Merge pull request #2277 from deepseek-harness/codex/background-first-continuable-subagents

feat(subagent): default continuable delegation to background

.agents/notes/implemented/feature/2026-08-06-manager-owned-subagent-settlement-delivery.i18n.yaml

@@ -2,5 +2,5 @@
 # side as of the last confirmed-consistent state. Both languages carry equal authority;
 # after editing either side, bring the other along and re-record with:
 #   pnpm run verify-translation-pairing --write .agents/notes/implemented/feature/2026-08-06-manager-owned-subagent-settlement-delivery.md
-2026-08-06-manager-owned-subagent-settlement-delivery.md: e06fe2b4ca7dd9a975f70524979de09d13cdcf79
-2026-08-06-manager-owned-subagent-settlement-delivery.zh.md: 77e8b5e4bae9b05e08bf2c4a4bf997b688cd1157
+2026-08-06-manager-owned-subagent-settlement-delivery.md: 11669d4603e658d1478557f81c2d2b4d5495bca7
+2026-08-06-manager-owned-subagent-settlement-delivery.zh.md: f3684777ccb3800226803e998438147ebc1dbf16

.agents/notes/implemented/feature/2026-08-06-manager-owned-subagent-settlement-delivery.md

@@ -16,7 +16,7 @@ The signal already existed. `subagent/end` has carried `stopReason` and `lastAss
 
 The continuation manager delivers the account itself, from inside the disposal transaction that ends the Activation.
 
-When a resident Activation settles, `notifySettlement()` resolves the child's durable direct parent and sends it one user-role message: the epoch's outcome as a sentence the parent can act on, then the child's final assistant content, or a statement that it produced none. Delivery is unconditional for every child whose id a caller actually received. It does not consult whether the child reported, and it keeps no bookkeeping that could make the promise conditional — that unconditionality is what lets `tool-subagent` tell the model "you are told when it finishes, so never poll or wait on it" and have that be true. A materialization rolled back before its first accepted message stays silent, because the caller was told that child was not established.
+When a resident Activation settles, `notifySettlement()` resolves the child's durable direct parent and sends it one user-role message: the epoch's outcome as a sentence the parent can act on, then the child's final assistant content, or a statement that it produced none. Delivery is unconditional for every child whose id a caller actually received. It does not consult whether the child reported, and it keeps no bookkeeping that could make the promise conditional — that unconditionality is what lets `tool-subagent` promise a runtime notice containing the outcome and any final assistant message. A materialization rolled back before its first accepted message stays silent, because the caller was told that child was not established.
 
 ### Provenance
 
@@ -44,7 +44,7 @@ Delivery never blocks or fails teardown. A rejected send is logged and dropped,
 
 ### The epoch's own log is the whole account
 
-`epochStopReason()` reads the epoch's outcome from its own log, because teardown succeeding says nothing about whether the model errored, hit its ceiling, or was stopped. Reading turns alone got that wrong twice, in the same shape both times: a turn stopped before its first step leaves a `turn/end` indistinguishable from the balanced no-op turns a rejection or an emptied claim produces, so the filter that skipped those also skipped real endings and answered with the previous turn's clean completion. The durability checkpoint (`dsh-session-checkpoint-policy`, in every shipped profile) and prompt assembly both run at that boundary and both propagate, and `Inbox.claim()` has already taken the messages by then — so the parent was told a child finished while the delivery it was waiting on had been swallowed. Under a promise that says "you are told when it finishes, so never poll", that is the one failure a parent cannot detect and will not retry.
+`epochStopReason()` reads the epoch's outcome from its own log, because teardown succeeding says nothing about whether the model errored, hit its ceiling, or was stopped. Reading turns alone got that wrong twice, in the same shape both times: a turn stopped before its first step leaves a `turn/end` indistinguishable from the balanced no-op turns a rejection or an emptied claim produces, so the filter that skipped those also skipped real endings and answered with the previous turn's clean completion. The durability checkpoint (`dsh-session-checkpoint-policy`, in every shipped profile) and prompt assembly both run at that boundary and both propagate, and `Inbox.claim()` has already taken the messages by then — so the parent was told a child finished while the delivery it was waiting on had been swallowed. Under the advertised automatic settlement notice, that is the one failure a parent cannot detect and will not retry.
 
 The missing fact was never the turn's; it was the inbox's. `Inbox` logs every mutation with `removedCount` and marks a cancellation `outcome: 'canceled'`, which separates a turn claiming its input from work being dropped unrun. `foldConsumedWork()` in `dsh-agent` folds both vocabularies into one answer: the latest turn that accounts for consumed work — stepped, or claimed-then-failed, stopped, or rejected — and whether accepted work was cancelled after it with no turn opening over it. A `blocked` end over claimed input is an account too: the pre-step rejection that produced it — a hook deny, a policy plugin — discarded the messages the turn claimed, so the notice says the child declined rather than finished. Only a `blocked` turn that claimed nothing stays invisible.
 
@@ -60,7 +60,7 @@ Three assembled ACP scenarios cover the notice: a child that never reports, a ch
 
 `subagent-continuable` is the one that pins a failure. Its child's last turn dies on the forced durability checkpoint without entering a step, so that transcript is where the stop-reason rule above is visible end to end: the notice says the child *failed*, carries the earlier `SECOND_OK` as its last content rather than as a result, and the parent's own acknowledgement turn reaches the ACP client.
 
-A keyless headless Loader snapshot covers the user-visible path end to end. Its replay parent starts one continuable child with `run_in_background: true`, never calls `list_agents`, `send_message`, or Task tools, consumes the manager-authored `subagent-settled` notice, and produces its final answer. The child never calls `report`, so the transcript cannot pass through the cooperative report path. A test-only Loader fence holds the parent's post-spawn request until the real manager notice enters its inbox, removing platform scheduling from the transcript without synthesizing the notice.
+A keyless headless Loader snapshot covers the user-visible path end to end. Its replay parent omits `run_in_background` to exercise the continuable background default, never calls `list_agents`, `send_message`, or Task tools, consumes the manager-authored `subagent-settled` notice, and produces its final answer. The child never calls `report`, so the transcript cannot pass through the cooperative report path. A test-only Loader fence holds the parent's post-spawn request until the real manager notice enters its inbox, removing platform scheduling from the transcript without synthesizing the notice.
 
 `subagent-report` needed one more concession. With the shipped waking report default, that scenario has two independent parent wakes — the report and the settlement — and whether the second extends the first's turn or opens its own is a genuine coin flip that measured 50/50 across runs. No authored transcript can hold both orders. Its overlay therefore pins `reportDelivery: quiet`, leaving settlement as the only wake, and a snapshot-only pre-step fence holds the child until the parent's spawn turn ends so that wake opens one deterministic turn claiming both messages. The waking report default keeps its coverage in the report package's own tests.
 

.agents/notes/implemented/feature/2026-08-06-manager-owned-subagent-settlement-delivery.zh.md

@@ -16,7 +16,7 @@ Status: implemented
 
 继续执行管理器自己投递这份记账，就在结束 Activation 的那笔 dispose 事务内部完成。
 
-当驻留 Activation 结算时，`notifySettlement()` 解析该 child 持久化的直接父级，并向它发送一条用户角色消息：先是父级可据以行动的一句结果说明，然后是 child 的最终 assistant 内容，或一句说明它没有产出内容。对每个调用方真正拿到过 id 的 child，投递都是无条件的。它不查询 child 是否上报过，也不保留任何可能让这项承诺变成有条件的记账——正是这种无条件性，才让 `tool-subagent` 能够告诉模型「它结束时你会被告知，因此绝不要轮询或等待它」并且这句话为真。在第一条消息被接受之前就回滚的物化保持静默，因为调用方已被告知该 child 未建立。
+当驻留 Activation 结算时，`notifySettlement()` 解析该 child 持久化的直接父级，并向它发送一条用户角色消息：先是父级可据以行动的一句结果说明，然后是 child 的最终 assistant 内容，或一句说明它没有产出内容。对每个调用方真正拿到过 id 的 child，投递都是无条件的。它不查询 child 是否上报过，也不保留任何可能让这项承诺变成有条件的记账——正是这种无条件性，才让 `tool-subagent` 能够承诺一条包含结局与可能存在的最终 assistant 消息的运行时通知。在第一条消息被接受之前就回滚的物化保持静默，因为调用方已被告知该 child 未建立。
 
 ### 来源信息
 
@@ -44,7 +44,7 @@ Status: implemented
 
 ### epoch 自己的日志就是全部交代
 
-`epochStopReason()` 从 epoch 自己的日志读取结局，因为拆卸成功与否，对「模型是否报错、是否撞到上限、是否被停下」什么也没说明。只读轮次这件事已经错了两次，而两次的形状相同：在第一个 step 之前被停下的轮次，其 `turn/end` 与「拒绝」或「被清空的认领」产生的平衡空转轮次长得一模一样，于是那道用来跳过后者的过滤，也把真实的结局一起跳过了，转而用上一个轮次的干净收尾作答。持久化检查点（`dsh-session-checkpoint-policy`，存在于每个随附 profile 中）与提示词组装都运行在这个边界上、且都会向外传播，而此时 `Inbox.claim()` 已经把消息取走了——于是父级被告知 child 已完成，而它正在等待的那条投递已被吞掉。在「你会在它完成时被告知，所以永远不要轮询」这一承诺之下，这恰恰是父级无法察觉、也不会重试的那一种失败。
+`epochStopReason()` 从 epoch 自己的日志读取结局，因为拆卸成功与否，对「模型是否报错、是否撞到上限、是否被停下」什么也没说明。只读轮次这件事已经错了两次，而两次的形状相同：在第一个 step 之前被停下的轮次，其 `turn/end` 与「拒绝」或「被清空的认领」产生的平衡空转轮次长得一模一样，于是那道用来跳过后者的过滤，也把真实的结局一起跳过了，转而用上一个轮次的干净收尾作答。持久化检查点（`dsh-session-checkpoint-policy`，存在于每个随附 profile 中）与提示词组装都运行在这个边界上、且都会向外传播，而此时 `Inbox.claim()` 已经把消息取走了——于是父级被告知 child 已完成，而它正在等待的那条投递已被吞掉。在已公布的自动结算通知约定下，这恰恰是父级无法察觉、也不会重试的那一种失败。
 
 缺失的事实从来不属于轮次，而属于 inbox。`Inbox` 会把每次改动连同 `removedCount` 一起记入日志，并给取消标记 `outcome: 'canceled'`，这就把「某个轮次认领了它的输入」与「工作被丢弃且从未运行」区分开来。`dsh-agent` 中的 `foldConsumedWork()` 把两套词汇折叠成一个答案：能为已消费工作作出交代的最新轮次——进入过 step 的，或认领后失败、被停下或被拒绝的——以及此后是否有已接受的工作被取消、而没有任何轮次为它开启过。认领过输入、以 `blocked` 结束的轮次同样是一份交代：产生它的 pre-step 拒绝——hook deny、策略插件——把该轮次认领的消息一并丢弃了，因此通知会说 child 拒绝了任务，而不是完成了任务。只有没认领任何输入的 `blocked` 轮次保持不可见。
 
@@ -60,7 +60,7 @@ Status: implemented
 
 `subagent-continuable` 是其中固定失败结局的那个。它的 child 最后一个轮次在被强制的持久化检查点上死亡，且未进入任何 step，因此该 transcript 正是上面那条终止原因规则的端到端可见之处：通知说该 child **失败**，把此前的 `SECOND_OK` 作为它最后产出的内容而非结果携带，而父级自己的确认轮次会到达 ACP 客户端。
 
-另有一个无密钥的 headless Loader 快照端到端覆盖用户可见路径。其重放父级通过 `run_in_background: true` 启动一个可继续 child，从不调用 `list_agents`、`send_message` 或 Task 工具，消费管理器写入的 `subagent-settled` 通知，并给出最终答案。child 从不调用 `report`，因此该 transcript 不可能经由协作式上报路径通过。一个仅用于测试的 Loader 栅栏会把父级启动后的请求保持到真实管理器通知进入其 inbox 为止，从 transcript 中排除平台调度差异，但不会伪造该通知。
+另有一个无密钥的 headless Loader 快照端到端覆盖用户可见路径。其重放父级省略 `run_in_background` 以覆盖可继续后台默认路径，从不调用 `list_agents`、`send_message` 或 Task 工具，消费管理器写入的 `subagent-settled` 通知，并给出最终答案。child 从不调用 `report`，因此该 transcript 不可能经由协作式上报路径通过。一个仅用于测试的 Loader 栅栏会把父级启动后的请求保持到真实管理器通知进入其 inbox 为止，从 transcript 中排除平台调度差异，但不会伪造该通知。
 
 `subagent-report` 还需要多做一步让步。在随附的唤醒上报默认值下，该场景有两个互相独立的父级唤醒——上报与结算——而第二个究竟是延长第一个的轮次还是另开一个轮次，是一枚真正的硬币，多次运行实测约为五五开。任何手写 transcript 都无法同时容纳两种顺序。因此它的 overlay 固定 `reportDelivery: quiet`，使结算成为唯一唤醒；另一个仅用于快照的 pre-step 栅栏会把 child 保持到父级启动轮次结束，使这次唤醒开启一个确定轮次并同时认领两条消息。唤醒上报默认值的覆盖则保留在 report 包自身的测试中。
 

.agents/notes/implemented/feature/2026-08-11-background-first-continuable-delegation.i18n.yaml

@@ -0,0 +1,6 @@
+# Bilingual-pair consistency record (docs/i18n/README.md): the git blob hash of each
+# side as of the last confirmed-consistent state. Both languages carry equal authority;
+# after editing either side, bring the other along and re-record with:
+#   pnpm run verify-translation-pairing --write .agents/notes/implemented/feature/2026-08-11-background-first-continuable-delegation.md
+2026-08-11-background-first-continuable-delegation.md: e90b0a97cd5eeb273c8084d231ced003a661b978
+2026-08-11-background-first-continuable-delegation.zh.md: b8f14e0c40c341fc91b2fd0dc8c3f00fc2e14b66

.agents/notes/implemented/feature/2026-08-11-background-first-continuable-delegation.md

@@ -0,0 +1,45 @@
+# Agent Note: Continuable delegation is background-first
+
+Status: implemented
+
+English | [中文](2026-08-11-background-first-continuable-delegation.zh.md)
+
+## Problem
+
+A continuable child already has a durable id, independent turns, follow-up messaging, and a manager-owned settlement notice. Treating an omitted `run_in_background` as foreground makes that lifecycle depend on the model restating `true` on every call. It also obscures the useful scheduling test: the parent should wait only when its next action requires the child's result.
+
+The child-scoped `report` prompt requires a self-contained final report, while [manager-owned settlement delivery](2026-08-06-manager-owned-subagent-settlement-delivery.md) independently sends the run outcome and closing message. A completed child can therefore wake its parent with a final report and again with settlement. Background-first scheduling must preserve both deliveries: the child-authored handoff remains mandatory guidance, while the manager-authored notice covers every terminal path regardless of model compliance.
+
+## Decision
+
+`tool-subagent` resolves an omitted `run_in_background` from the selected lifecycle policy. `backgroundMode: continuable` resolves omission to background and returns the durable child id immediately; explicit `false` selects foreground and waits for the result. `backgroundMode: one-shot` keeps its foreground default because background output still requires Task collection. `enableRunInBackground: false` continues to omit the parameter, reject forced `true`, and run in the foreground. No second default-selection config is added.
+
+The model-facing text divides responsibility by location:
+
+- the tool description states the call behavior, durable id, runtime settlement notice, follow-up through `send_message`, and the explicit foreground override;
+- the `run_in_background` parameter states the lifecycle-specific default and when to override it;
+- a `tool:<toolName>` system-prompt section tells the model to start independent delegations together, continue useful work while they run, and choose foreground only when the next action depends on the result. The section renders only when that tool remains visible in the assembly scope, so a child tool restriction removes the schema and its guidance together.
+
+The [continuable child report obligation](2026-08-06-continuable-child-report-obligation.md) remains unchanged: the child prompt requires one self-contained final report and earlier reports for findings that change the parent's next action. Manager-owned settlement remains unconditional and does not inspect whether a report arrived. The two messages may repeat final content, but they retain distinct authors and purposes: `report` is the child's explicit handoff, while settlement records how the run ended and preserves terminal output when the child cannot cooperate. `reportDelivery` remains deployment scheduling policy with `wakeup` as its default.
+
+The keyless headless `subagent-settlement` scenario omits `run_in_background`, receives the immediate child id, and reaches the final parent answer through the manager-authored settlement notice even though its fixture deliberately does not call `report`. Package tests separately pin explicit `false` as foreground, the parent scheduling text, and the child's mandatory-report prompt.
+
+## Alternatives considered
+
+**Replace the field with `run_in_foreground`.** Reversing the boolean makes the common case read positively, but creates a second vocabulary for the same scheduling choice and forces every existing caller and provider-facing transcript to change. Keeping `run_in_background` preserves one field and makes foreground the explicit exception.
+
+**Add a configurable background default.** A separate default can disagree with `backgroundMode`, the schema wording, and the installed prompt. The lifecycle policy already distinguishes a continuable activation from a one-shot Task, which is the distinction that determines whether background completion is delivered automatically.
+
+**Change only the prompt.** Prompt preference without runtime resolution still turns an omitted argument into foreground. The model must be able to rely on the advertised default rather than reproduce it perfectly on every tool call.
+
+**Suppress settlement after a final report arrives.** Conditional settlement reintroduces per-Activation bookkeeping and loses the unconditional runtime guarantee when a child reports progress and then fails. Settlement remains unconditional even when the resulting message overlaps a final report.
+
+**Use `report` only for progress before settlement.** This removes duplicate final content but also removes the explicit child-authored handoff from the child prompt. The final-report obligation remains, and runtime settlement remains its independent fallback and terminal record.
+
+## Consequences
+
+- An ordinary continuable call is non-blocking without spelling `run_in_background: true`; serialized delegation is an explicit `false` choice.
+- Independent subagent calls in one assistant message overlap under the tool loop's concurrency-safe dispatch, while dependent foreground calls can still be issued one at a time.
+- Parent guidance, tool schema, runtime resolution, and settlement delivery state the same default.
+- A compliant child reports one self-contained final result and may report important findings earlier. Every Activation also produces an unconditional settlement notice, so a completed run may deliver overlapping final content twice.
+- One-shot background Tasks and disabled-background tool instances retain their existing behavior.

.agents/notes/implemented/feature/2026-08-11-background-first-continuable-delegation.zh.md

@@ -0,0 +1,45 @@
+# Agent Note: 可继续委派采用后台优先
+
+Status: implemented
+
+[English](2026-08-11-background-first-continuable-delegation.md) | 中文
+
+## 问题
+
+可继续 child 已经具备持久化 id、独立轮次、后续消息以及由管理器负责的结算通知。如果把省略的 `run_in_background` 视为前台，模型就必须在每次调用时重复写出 `true`，才能得到这套生命周期。这样也会掩盖真正有用的调度判断：只有当 parent 的下一步动作需要 child 结果时，parent 才应等待。
+
+child 作用域的 `report` 提示词要求发送自包含的最终报告，而[由管理器负责的结算投递](2026-08-06-manager-owned-subagent-settlement-delivery.md)会独立发送本次运行的结束结果与收尾消息。已完成的 child 因而可能先用最终报告唤醒 parent，再用结算通知唤醒一次。后台优先调度会保留两次投递：由 child 编写的交接仍是强制提示词指引，由管理器生成的通知则不依赖模型是否遵循指令，覆盖每种终止路径。
+
+## 决策
+
+`tool-subagent` 根据选定的生命周期策略解析省略的 `run_in_background`。`backgroundMode: continuable` 会把省略解析为后台并立即返回持久化 child id；显式传入 `false` 会选择前台并等待结果。`backgroundMode: one-shot` 保留前台默认行为，因为它的后台输出仍需通过 Task 收集。`enableRunInBackground: false` 仍会省略该参数、拒绝强制传入的 `true` 并在前台运行。系统不增加第二个默认选择配置。
+
+面向模型的文本按位置划分职责：
+
+- 工具描述说明调用行为、持久化 id、运行时结算通知、通过 `send_message` 继续对话，以及显式前台覆盖；
+- `run_in_background` 参数说明具体生命周期的默认值以及何时覆盖；
+- `tool:<toolName>` 系统提示词 section 会告诉模型同时启动相互独立的委派、在它们运行时继续有用工作，并且仅当下一步动作依赖结果时选择前台。只有当该工具在组装作用域中仍可见时才会渲染这个 section，因此子级工具限制会同时移除 schema 与对应指引。
+
+[可继续 child 上报义务](2026-08-06-continuable-child-report-obligation.md)保持不变：child 提示词要求发送一份自包含的最终报告，并在发现会改变 parent 下一步动作的信息时提前报告。由管理器负责的结算仍然无条件执行，不检查报告是否已经到达。这两条消息可能重复最终内容，但作者和用途不同：`report` 是 child 的显式交接，结算则记录本次运行如何结束，并在 child 无法配合时保留终止输出。`reportDelivery` 仍是部署调度策略，默认值仍为 `wakeup`。
+
+无密钥 headless `subagent-settlement` 场景省略 `run_in_background`，收到立即返回的 child id；尽管 fixture（测试前置数据）有意不调用 `report`，它仍通过管理器生成的结算通知到达 parent 最终答案。包测试另行固定了显式 `false` 的前台语义、parent 调度文本以及 child 的强制报告提示词。
+
+## 考虑过的替代方案
+
+**把字段替换为 `run_in_foreground`。** 反转布尔值会让常见情形以肯定形式表达，却会为同一项调度选择创造第二套词汇，并迫使所有现有调用方与面向提供方的 transcript（文本记录）一起改变。保留 `run_in_background` 可以维持单一字段，并把前台作为显式例外。
+
+**增加可配置的后台默认值。** 独立默认值可能与 `backgroundMode`、schema 措辞和已安装提示词不一致。生命周期策略已经区分可继续 Activation 与一次性 Task，而这个区别正好决定了后台完成是否会自动投递。
+
+**只修改提示词。** 如果运行时解析不变，提示词偏好仍会让省略参数的调用进入前台。模型必须能够依赖公布的默认值，而不是在每次工具调用中完美复述它。
+
+**最终报告到达后抑制结算通知。** 条件结算会重新引入每次 Activation 的记账，并且当 child 先报告进度、随后失败时丢掉无条件运行时保证。即使生成的消息与最终报告重叠，结算仍然无条件执行。
+
+**只用 `report` 发送结算前的进度。** 这样可以消除重复的最终内容，但也会从 child 提示词中移除由 child 编写的显式交接。最终报告义务保持不变，运行时结算则继续作为它的独立后备和终止记录。
+
+## 后果
+
+- 普通可继续调用无需写出 `run_in_background: true` 即为非阻塞；串行委派需要显式选择 `false`。
+- 同一条 assistant 消息中的独立 subagent 调用会在工具循环的并发安全分发下重叠执行；有依赖的前台调用仍可逐个发出。
+- parent 指引、工具 schema、运行时解析和结算投递陈述同一个默认值。
+- 遵循指令的 child 会发送一份自包含的最终结果，也可以更早报告重要发现。每次 Activation 还会产生无条件结算通知，因此已完成的运行可能两次投递相互重叠的最终内容。
+- 一次性后台 Task 与禁用后台的工具实例保留现有行为。

docs/config-catalog.i18n.yaml

@@ -2,5 +2,5 @@
 # side as of the last confirmed-consistent state. Both languages carry equal authority;
 # after editing either side, bring the other along and re-record with:
 #   pnpm run verify-translation-pairing --write docs/config-catalog.md
-config-catalog.md: b29df04dc35e6fe472f425c4ef81d1d406445bde
-config-catalog.zh.md: 14a654d1e02fe1c1690e5cc7bf3a4bc40359f23d
+config-catalog.md: 08c1c63050aefd9e0fcc7c603ad40ec6405bf6c1
+config-catalog.zh.md: e7cfcff8d69c3a1efbe8426e25415783bc41f864

docs/config-catalog.md

@@ -2300,7 +2300,7 @@ Source: [`packages/fs/tool-str-replace-editor/src/index.ts:497`](../packages/fs/
 
 ## `@deepseek-ai/dsh-tool-subagent`
 
-Requires: `tools` · `subagents`
+Requires: `tools` · `subagents` · `systemPrompt`
 
 ```ts config-catalog
 /** Config: which registered provider this tool delegates to, plus child defaults. */
@@ -2318,9 +2318,10 @@ export interface Config {
    */
   enableRunInBackground?: boolean
   /**
-   * Background execution policy (default `one-shot`). `continuable` requires a
-   * provider with the `prepareContinuable` capability and returns the durable
-   * child id; follow-up adapters remain independently optional.
+   * Background execution policy (default `one-shot`). `one-shot` defaults calls
+   * to foreground; `continuable` defaults them to background, requires a provider
+   * with the `prepareContinuable` capability, and returns the durable child id.
+   * Follow-up adapters remain independently optional.
    */
   backgroundMode?: 'one-shot' | 'continuable'
   /**
@@ -2358,7 +2359,7 @@ export interface Config {
 
 Depends on: [`AgentOptions`](subsystems/core.md)
 
-Source: [`packages/subagent/tool-subagent/src/index.ts:25`](../packages/subagent/tool-subagent/src/index.ts)
+Source: [`packages/subagent/tool-subagent/src/index.ts:29`](../packages/subagent/tool-subagent/src/index.ts)
 
 ## `@deepseek-ai/dsh-tool-subagent-report`
 

docs/config-catalog.zh.md

@@ -2301,7 +2301,7 @@ export interface Config {
 
 ## `@deepseek-ai/dsh-tool-subagent`
 
-需要：`tools` · `subagents`
+需要：`tools` · `subagents` · `systemPrompt`
 
 ```ts config-catalog
 /** Config: which registered provider this tool delegates to, plus child defaults. */
@@ -2319,9 +2319,10 @@ export interface Config {
    */
   enableRunInBackground?: boolean
   /**
-   * Background execution policy (default `one-shot`). `continuable` requires a
-   * provider with the `prepareContinuable` capability and returns the durable
-   * child id; follow-up adapters remain independently optional.
+   * Background execution policy (default `one-shot`). `one-shot` defaults calls
+   * to foreground; `continuable` defaults them to background, requires a provider
+   * with the `prepareContinuable` capability, and returns the durable child id.
+   * Follow-up adapters remain independently optional.
    */
   backgroundMode?: 'one-shot' | 'continuable'
   /**
@@ -2359,7 +2360,7 @@ export interface Config {
 
 依赖：[`AgentOptions`](subsystems/core.md)
 
-来源：[`packages/subagent/tool-subagent/src/index.ts:25`](../packages/subagent/tool-subagent/src/index.ts)
+来源：[`packages/subagent/tool-subagent/src/index.ts:29`](../packages/subagent/tool-subagent/src/index.ts)
 
 ## `@deepseek-ai/dsh-tool-subagent-report`
 

docs/module-graph.i18n.yaml

@@ -2,5 +2,5 @@
 # side as of the last confirmed-consistent state. Both languages carry equal authority;
 # after editing either side, bring the other along and re-record with:
 #   pnpm run verify-translation-pairing --write docs/module-graph.md
-module-graph.md: 537d5c4bf78f5c4c69e7753e6840652cec7f04b5
-module-graph.zh.md: 222de9a3f0fd5fa77c4613a4c49aea49ed1b75d1
+module-graph.md: 64f1d33c57bbdf459a834ab5a51674c49c6a4a49
+module-graph.zh.md: 5f6ddd89a6d323ec6d8fd5acabb52fb1c9f7f43c

docs/module-graph.md

@@ -1009,6 +1009,7 @@ flowchart TD
   pkg_tool_subagent --> pkg_invariants
   pkg_tool_subagent --> pkg_llm
   pkg_tool_subagent --> pkg_subagent
+  pkg_tool_subagent --> pkg_system_prompt
   pkg_tool_subagent --> pkg_tasks
   pkg_tool_subagent --> pkg_tools
   pkg_tool_subagent_control --> pkg_invariants
@@ -1493,7 +1494,7 @@ flowchart TD
 | [`subagent-acp`](../packages/subagent/subagent-acp) | `subagent` | [`agent`](../packages/core/agent), [`invariants`](../packages/support/invariants), [`llm`](../packages/llm/llm), [`session`](../packages/core/session), [`subagent`](../packages/subagent/subagent), [`subprocess`](../packages/subprocess/subprocess), [`timeout`](../packages/util/timeout) |
 | [`subagent-claude-code`](../packages/subagent/subagent-claude-code) | `subagent` | [`invariants`](../packages/support/invariants), [`llm`](../packages/llm/llm), [`session`](../packages/core/session), [`subagent`](../packages/subagent/subagent), [`subprocess`](../packages/subprocess/subprocess), [`timeout`](../packages/util/timeout) |
 | [`subagent-inprocess`](../packages/subagent/subagent-inprocess) | `subagent` | [`agent`](../packages/core/agent), [`invariants`](../packages/support/invariants), [`llm`](../packages/llm/llm), [`session`](../packages/core/session), [`subagent`](../packages/subagent/subagent), [`system-prompt`](../packages/core/system-prompt), [`tools`](../packages/core/tools) |
-| [`tool-subagent`](../packages/subagent/tool-subagent) | `subagent` | [`agent`](../packages/core/agent), [`invariants`](../packages/support/invariants), [`llm`](../packages/llm/llm), [`subagent`](../packages/subagent/subagent), [`tasks`](../packages/tasks/tasks), [`tools`](../packages/core/tools) |
+| [`tool-subagent`](../packages/subagent/tool-subagent) | `subagent` | [`agent`](../packages/core/agent), [`invariants`](../packages/support/invariants), [`llm`](../packages/llm/llm), [`subagent`](../packages/subagent/subagent), [`system-prompt`](../packages/core/system-prompt), [`tasks`](../packages/tasks/tasks), [`tools`](../packages/core/tools) |
 | [`tool-subagent-control`](../packages/subagent/tool-subagent-control) | `subagent` | [`invariants`](../packages/support/invariants), [`llm`](../packages/llm/llm), [`session`](../packages/core/session), [`subagent`](../packages/subagent/subagent), [`tools`](../packages/core/tools) |
 | [`tool-subagent-report`](../packages/subagent/tool-subagent-report) | `subagent` | [`invariants`](../packages/support/invariants), [`llm`](../packages/llm/llm), [`subagent`](../packages/subagent/subagent), [`system-prompt`](../packages/core/system-prompt), [`tools`](../packages/core/tools) |
 | [`hooks-claude`](../packages/hooks/hooks-claude) | `hooks` | [`agent`](../packages/core/agent), [`hook-protocol`](../packages/hooks/hook-protocol), [`invariants`](../packages/support/invariants), [`llm`](../packages/llm/llm), [`session`](../packages/core/session), [`session-persistence`](../packages/session/session-persistence), [`subagent`](../packages/subagent/subagent), [`tools`](../packages/core/tools) |

docs/module-graph.zh.md

@@ -1011,6 +1011,7 @@ flowchart TD
   pkg_tool_subagent --> pkg_invariants
   pkg_tool_subagent --> pkg_llm
   pkg_tool_subagent --> pkg_subagent
+  pkg_tool_subagent --> pkg_system_prompt
   pkg_tool_subagent --> pkg_tasks
   pkg_tool_subagent --> pkg_tools
   pkg_tool_subagent_control --> pkg_invariants
@@ -1495,7 +1496,7 @@ flowchart TD
 | [`subagent-acp`](../packages/subagent/subagent-acp) | `subagent` | [`agent`](../packages/core/agent), [`invariants`](../packages/support/invariants), [`llm`](../packages/llm/llm), [`session`](../packages/core/session), [`subagent`](../packages/subagent/subagent), [`subprocess`](../packages/subprocess/subprocess), [`timeout`](../packages/util/timeout) |
 | [`subagent-claude-code`](../packages/subagent/subagent-claude-code) | `subagent` | [`invariants`](../packages/support/invariants), [`llm`](../packages/llm/llm), [`session`](../packages/core/session), [`subagent`](../packages/subagent/subagent), [`subprocess`](../packages/subprocess/subprocess), [`timeout`](../packages/util/timeout) |
 | [`subagent-inprocess`](../packages/subagent/subagent-inprocess) | `subagent` | [`agent`](../packages/core/agent), [`invariants`](../packages/support/invariants), [`llm`](../packages/llm/llm), [`session`](../packages/core/session), [`subagent`](../packages/subagent/subagent), [`system-prompt`](../packages/core/system-prompt), [`tools`](../packages/core/tools) |
-| [`tool-subagent`](../packages/subagent/tool-subagent) | `subagent` | [`agent`](../packages/core/agent), [`invariants`](../packages/support/invariants), [`llm`](../packages/llm/llm), [`subagent`](../packages/subagent/subagent), [`tasks`](../packages/tasks/tasks), [`tools`](../packages/core/tools) |
+| [`tool-subagent`](../packages/subagent/tool-subagent) | `subagent` | [`agent`](../packages/core/agent), [`invariants`](../packages/support/invariants), [`llm`](../packages/llm/llm), [`subagent`](../packages/subagent/subagent), [`system-prompt`](../packages/core/system-prompt), [`tasks`](../packages/tasks/tasks), [`tools`](../packages/core/tools) |
 | [`tool-subagent-control`](../packages/subagent/tool-subagent-control) | `subagent` | [`invariants`](../packages/support/invariants), [`llm`](../packages/llm/llm), [`session`](../packages/core/session), [`subagent`](../packages/subagent/subagent), [`tools`](../packages/core/tools) |
 | [`tool-subagent-report`](../packages/subagent/tool-subagent-report) | `subagent` | [`invariants`](../packages/support/invariants), [`llm`](../packages/llm/llm), [`subagent`](../packages/subagent/subagent), [`system-prompt`](../packages/core/system-prompt), [`tools`](../packages/core/tools) |
 | [`hooks-claude`](../packages/hooks/hooks-claude) | `hooks` | [`agent`](../packages/core/agent), [`hook-protocol`](../packages/hooks/hook-protocol), [`invariants`](../packages/support/invariants), [`llm`](../packages/llm/llm), [`session`](../packages/core/session), [`session-persistence`](../packages/session/session-persistence), [`subagent`](../packages/subagent/subagent), [`tools`](../packages/core/tools) |

docs/tool-catalog.i18n.yaml

@@ -2,5 +2,5 @@
 # side as of the last confirmed-consistent state. Both languages carry equal authority;
 # after editing either side, bring the other along and re-record with:
 #   pnpm run verify-translation-pairing --write docs/tool-catalog.md
-tool-catalog.md: b8f8e029ceed9d6447cd9e36b98fc75b7e6891b4
-tool-catalog.zh.md: 7a12097983380560153c2ed8721cb10a2a06aa7b
+tool-catalog.md: 898c5700eddfe49083b2ce0e3e04761298b28bbb
+tool-catalog.zh.md: 3b17cf4e3b1b74b0735783cfe899c9c693146c38

docs/tool-catalog.md

@@ -32,7 +32,7 @@ This table connects model-visible tool names to the plugin package and service s
 | `@deepseek-ai/dsh-tool-ralph` | `ralph` | `ctx.tools`, `ctx.workflows`, `ctx.subagents`, `ctx.systemPrompt`, `a calling Agent (exec.agent parents every fresh round)` | `tool/call`, `tool/result`, `workflow and child session events during execution` | - | A fixed foreground workflow starts one fresh structured child per round; the model selects only the immutable objective and an optional round cap. |
 | `@deepseek-ai/dsh-tool-skill` | `skill` | `ctx.tools`, `ctx.agents`, `ctx.skills` | `tool/call`, `tool/result`, `user/message replacement catalogs via agent.inject()` | - | - |
 | `@deepseek-ai/dsh-tool-session-query` | `session_event_read`, `session_event_search`, `session_event_trace`, `session_search`, `session_trace` | `ctx.tools`, `ctx.systemPrompt`, `ctx.sessionQuery`, `a calling Agent for workspace authority` | `tool/call`, `tool/result` | - | The five read-only tools hide provider cursors and authorize every result from the immutable calling agent session. The package is opt-in; compositions that need enforced deadlines or bounded inline output also mount the generic timeout or spill policies. |
-| `@deepseek-ai/dsh-tool-subagent` | `subagent` | `ctx.tools`, `ctx.subagents` | `tool/call`, `tool/result`, `child session events through the chosen provider` | `subagent`, `subagent_fork` | The registered tool name is the load-time `toolName` config (default `subagent`); the schema above is that default. The shipped compositions load this package once per subagent backend, so the model additionally sees `subagent_fork` bound to the fork backend. Each instance's description and `run_in_background` parameter follow its own `backgroundMode` and `enableRunInBackground`, so the two shipped schemas are not identical: `subagent` is `continuable`, while `subagent_fork` stays `one-shot` — see `packages/bundle/base/cordis.patch.yml` and `examples/acp-agent/cordis.yml`. |
+| `@deepseek-ai/dsh-tool-subagent` | `subagent` | `ctx.tools`, `ctx.subagents`, `ctx.systemPrompt` | `tool/call`, `tool/result`, `child session events through the chosen provider` | `subagent`, `subagent_fork` | The registered tool name is the load-time `toolName` config (default `subagent`); the schema above is that default. The shipped compositions load this package once per subagent backend, so the model additionally sees `subagent_fork` bound to the fork backend. Each instance's description, `run_in_background` parameter, and system-prompt policy follow its own `backgroundMode` and `enableRunInBackground`, so the two shipped schemas are not identical: `subagent` is `continuable` and defaults omitted calls to background with automatic settlement delivery, while `subagent_fork` stays `one-shot` and defaults them to foreground — see `packages/bundle/base/cordis.patch.yml` and `examples/acp-agent/cordis.yml`. |
 | `@deepseek-ai/dsh-tool-subagent-control` | `interrupt_agent`, `list_agents`, `send_message` | `ctx.tools`, `ctx.subagents`, `ctx.agents and ctx.sessionProjections (list_agents only)` | `tool/call`, `tool/result`, `child session events through ctx.subagents` | - | The globally named control tools over continuable background subagents: provider-bound `tool-subagent` instances register distinct delegation tools, while this package registers `send_message` and `interrupt_agent` once, plus `list_agents` from its separately loaded `/list-agents` plugin (whose catalog rows use the sessionProjections and live Agent registries). |
 | `@deepseek-ai/dsh-tool-subagent-report` | `report` | `ctx.subagents`, `ctx.systemPrompt`, `a live continuable in-process child Agent` | `tool/call`, `tool/result`, `a user-role message in the direct parent session` | - | Registered per continuable in-process child rather than globally, so this schema is visible only inside such a child and survives its global `toolFilter`. The same contribution installs the child-scoped `tool:report` prompt section, which this catalog does not render. The parent-facing `send_message` tool is installed independently. |
 | `@deepseek-ai/dsh-tool-tasks` | `task_kill`, `task_list`, `task_output` | `ctx.tools`, `ctx.tasks`, `ctx.systemPrompt` | `tool/call`, `tool/result`, `user/message via agent.inject() for background completion notices` | - | The kind-agnostic background-task controller: background bash commands, PTY sends, and subagents are read, listed, and killed through the same three tools. Loading the plugin attaches the controller that arms producers' `ctx.tasks.start()`. |
@@ -1278,7 +1278,7 @@ The five read-only tools hide provider cursors and authorize every result from t
 
 ### `subagent`
 
-Delegate a self-contained task to a subagent (a separate agent that works in its own context) and return its final result. Use this to offload focused, independent work — research, a scoped implementation, an analysis — so it does not consume this conversation's context. The subagent runs to completion and you receive only its final answer, not its intermediate steps. Give it a complete, standalone prompt: it does not see this conversation. Set `run_in_background: true` to return a task id; collect with `task_output` and stop with `task_kill`.
+Delegate a self-contained task to a subagent (a separate agent that works in its own context) to offload focused, independent work — research, a scoped implementation, an analysis — so it does not consume this conversation's context. The subagent returns its result, not its intermediate steps. Give it a complete, standalone prompt: it does not see this conversation. This call waits for the result by default. Set `run_in_background: true` to return a task id; collect with `task_output` and stop with `task_kill`.
 
 ```json
 {
@@ -1294,7 +1294,7 @@ Delegate a self-contained task to a subagent (a separate agent that works in its
     },
     "run_in_background": {
       "type": "boolean",
-      "description": "Run as a background task and return its id; collect with task_output or stop with task_kill."
+      "description": "Whether to run as a background task and return its id. Defaults to false; collect with task_output or stop with task_kill."
     }
   },
   "required": [
@@ -1306,7 +1306,7 @@ Delegate a self-contained task to a subagent (a separate agent that works in its
 
 Source: [`packages/subagent/tool-subagent/src/index.ts`](../packages/subagent/tool-subagent/src/index.ts)
 
-The registered tool name is the load-time `toolName` config (default `subagent`); the schema above is that default. The shipped compositions load this package once per subagent backend, so the model additionally sees `subagent_fork` bound to the fork backend. Each instance's description and `run_in_background` parameter follow its own `backgroundMode` and `enableRunInBackground`, so the two shipped schemas are not identical: `subagent` is `continuable`, while `subagent_fork` stays `one-shot` — see `packages/bundle/base/cordis.patch.yml` and `examples/acp-agent/cordis.yml`.
+The registered tool name is the load-time `toolName` config (default `subagent`); the schema above is that default. The shipped compositions load this package once per subagent backend, so the model additionally sees `subagent_fork` bound to the fork backend. Each instance's description, `run_in_background` parameter, and system-prompt policy follow its own `backgroundMode` and `enableRunInBackground`, so the two shipped schemas are not identical: `subagent` is `continuable` and defaults omitted calls to background with automatic settlement delivery, while `subagent_fork` stays `one-shot` and defaults them to foreground — see `packages/bundle/base/cordis.patch.yml` and `examples/acp-agent/cordis.yml`.
 
 ## `@deepseek-ai/dsh-tool-subagent-control`
 

docs/tool-catalog.zh.md

@@ -34,7 +34,7 @@
 | `@deepseek-ai/dsh-tool-ralph` | `ralph` | `ctx.tools`、`ctx.workflows`、`ctx.subagents`、`ctx.systemPrompt`、`a calling Agent (exec.agent parents every fresh round)` | `tool/call`、`tool/result`、`workflow and child session events during execution` | - | 固定的前台工作流会在每个 Round 启动一个全新的结构化子级；模型只能选择不可变目标和可选的 Round 上限。 |
 | `@deepseek-ai/dsh-tool-skill` | `skill` | `ctx.tools`、`ctx.agents`、`ctx.skills` | `tool/call`、`tool/result`、`user/message replacement catalogs via agent.inject()` | - | - |
 | `@deepseek-ai/dsh-tool-session-query` | `session_event_read`、`session_event_search`、`session_event_trace`、`session_search`、`session_trace` | `ctx.tools`、`ctx.systemPrompt`、`ctx.sessionQuery`、`a calling Agent for workspace authority` | `tool/call`、`tool/result` | - | 这 5 个只读工具会隐藏提供方游标，并根据不可变的调用 agent 会话为每个结果授权。该包需要选择启用；需要强制截止时间或限制行内输出的组合还会挂载通用超时或 spill 策略。 |
-| `@deepseek-ai/dsh-tool-subagent` | `subagent` | `ctx.tools`、`ctx.subagents` | `tool/call`、`tool/result`、`child session events through the chosen provider` | `subagent`、`subagent_fork` | 注册的工具名称取决于加载时 `toolName` 配置（默认为 `subagent`）；上述 schema 对应默认值。随产品发布的组合会为每个 subagent 后端加载一次该包，因此模型还会看到绑定到 fork 后端的 `subagent_fork`。每个实例的描述与 `run_in_background` 参数取决于它自己的 `backgroundMode` 与 `enableRunInBackground`，因此两个随附 schema 并不相同：`subagent` 为 `continuable`，而 `subagent_fork` 保持 `one-shot`；见 `packages/bundle/base/cordis.patch.yml` 和 `examples/acp-agent/cordis.yml`。 |
+| `@deepseek-ai/dsh-tool-subagent` | `subagent` | `ctx.tools`、`ctx.subagents`、`ctx.systemPrompt` | `tool/call`、`tool/result`、`child session events through the chosen provider` | `subagent`、`subagent_fork` | 注册的工具名称取决于加载时 `toolName` 配置（默认为 `subagent`）；上述 schema 对应默认值。随产品发布的组合会为每个 subagent 后端加载一次该包，因此模型还会看到绑定到 fork 后端的 `subagent_fork`。每个实例的描述、`run_in_background` 参数与 system prompt 策略取决于它自己的 `backgroundMode` 和 `enableRunInBackground`，因此两个随附 schema 并不相同：`subagent` 为 `continuable`，省略参数时默认后台运行，并由 runtime 自动投递结束结果；`subagent_fork` 保持 `one-shot`，省略参数时默认前台运行。详见 `packages/bundle/base/cordis.patch.yml` 和 `examples/acp-agent/cordis.yml`。 |
 | `@deepseek-ai/dsh-tool-subagent-control` | `interrupt_agent`、`list_agents`、`send_message` | `ctx.tools`、`ctx.subagents`、`ctx.agents and ctx.sessionProjections (list_agents only)` | `tool/call`、`tool/result`、`child session events through ctx.subagents` | - | 这些是控制可继续后台 subagent 的全局命名工具：绑定提供方的 `tool-subagent` 实例注册不同的委派工具；本包注册一次 `send_message` 和 `interrupt_agent`，另由 `list_agents` 通过单独加载的 `/list-agents` 插件提供，其目录行使用 sessionProjections 和实时 Agent 注册表。 |
 | `@deepseek-ai/dsh-tool-subagent-report` | `report` | `ctx.subagents`、`ctx.systemPrompt`、`a live continuable in-process child Agent` | `tool/call`、`tool/result`、`a user-role message in the direct parent session` | - | 按可继续的进程内子级注册，而非全局注册，因此该 schema 仅在这种子级内部可见，并且不受其全局 `toolFilter` 影响。同一份贡献还会安装子级作用域的 `tool:report` 系统提示词 section，本目录不渲染该 section。面向父级的 `send_message` 工具单独安装。 |
 | `@deepseek-ai/dsh-tool-tasks` | `task_kill`、`task_list`、`task_output` | `ctx.tools`、`ctx.tasks`、`ctx.systemPrompt` | `tool/call`、`tool/result`、`user/message via agent.inject() for background completion notices` | - | 与任务种类无关的后台任务控制器：后台 bash 命令、PTY 发送和 subagent 都通过相同的 3 个工具读取、列出和终止。加载该插件会挂接控制器，从而启用生产方的 `ctx.tasks.start()`。 |
@@ -1282,7 +1282,7 @@ lsp 工具将提供方选择和语言服务器子进程置于 ctx.lsp 之后，
 
 ### `subagent`
 
-将一项自包含任务委派给 subagent（在自身上下文中工作的独立 agent），并返回其最终结果。可用它卸载聚焦且独立的工作，例如研究、限定范围的实现或分析，以免消耗当前对话的上下文。subagent 会运行到完成；你只会收到最终答案，而看不到中间步骤。请提供完整、独立的提示词，因为它看不到当前对话。设置 `run_in_background: true` 可返回 task id；使用 `task_output` 收集结果，使用 `task_kill` 停止任务。
+将一项自包含任务委派给 subagent（在自身上下文中工作的独立 agent），用它卸载聚焦且独立的工作，例如研究、限定范围的实现或分析，以免消耗当前对话的上下文。subagent 会返回结果，但不会返回中间步骤。请提供完整、独立的提示词，因为它看不到当前对话。此调用默认等待结果。设置 `run_in_background: true` 可返回 task id；使用 `task_output` 收集结果，使用 `task_kill` 停止任务。
 
 ```json
 {
@@ -1298,7 +1298,7 @@ lsp 工具将提供方选择和语言服务器子进程置于 ctx.lsp 之后，
     },
     "run_in_background": {
       "type": "boolean",
-      "description": "Run as a background task and return its id; collect with task_output or stop with task_kill."
+      "description": "Whether to run as a background task and return its id. Defaults to false; collect with task_output or stop with task_kill."
     }
   },
   "required": [
@@ -1310,7 +1310,7 @@ lsp 工具将提供方选择和语言服务器子进程置于 ctx.lsp 之后，
 
 来源：[`packages/subagent/tool-subagent/src/index.ts`](../packages/subagent/tool-subagent/src/index.ts)
 
-注册的工具名称取决于加载时 `toolName` 配置（默认为 `subagent`）；上述 schema 对应默认值。随产品发布的组合会为每个 subagent 后端加载一次该包，因此模型还会看到绑定到 fork 后端的 `subagent_fork`。每个实例的描述与 `run_in_background` 参数取决于它自己的 `backgroundMode` 与 `enableRunInBackground`，因此两个随附 schema 并不相同：`subagent` 为 `continuable`，而 `subagent_fork` 保持 `one-shot`；见 `packages/bundle/base/cordis.patch.yml` 和 `examples/acp-agent/cordis.yml`。
+注册的工具名称取决于加载时 `toolName` 配置（默认为 `subagent`）；上述 schema 对应默认值。随产品发布的组合会为每个 subagent 后端加载一次该包，因此模型还会看到绑定到 fork 后端的 `subagent_fork`。每个实例的描述、`run_in_background` 参数与 system prompt 策略取决于它自己的 `backgroundMode` 和 `enableRunInBackground`，因此两个随附 schema 并不相同：`subagent` 为 `continuable`，省略参数时默认后台运行，并由 runtime 自动投递结束结果；`subagent_fork` 保持 `one-shot`，省略参数时默认前台运行。详见 `packages/bundle/base/cordis.patch.yml` 和 `examples/acp-agent/cordis.yml`。
 
 ## `@deepseek-ai/dsh-tool-subagent-control`
 

examples/acp-agent/tests/snapshots/advanced-toolchain/session.1.jsonl

@@ -6,7 +6,7 @@
 {"type":"subagent/descriptor","seq":4,"time":1786357538308,"data":{"version":2,"mode":"one-shot","provider":"spawn","label":"Check direct child"}}
 {"type":"step/start","seq":5,"time":1786357538310,"data":{"turn":1,"step":1}}
 {"type":"user/message","seq":6,"time":1785730458555,"data":{"content":[{"type":"text","text":"Reply with exactly DIRECT_CHILD_OK and nothing else."}],"source":{"kind":"user"},"role":"user","id":"ebe0cfa0-a909-47e0-8294-28ad84a8fe77"},"surfaceOp":"append"}
-{"type":"user/message","seq":7,"time":1786357538310,"data":{"content":[{"type":"text","text":"Current runtime context. This snapshot supersedes earlier runtime-context snapshots.\n\nCurrent DSH file policy: danger-full-access. The DSH file sandbox does not restrict file modifications by available operations.\n\nApproval prompts are disabled in this session: actions that require approval are rejected automatically — do not request sandbox escalation (do not set `sandbox_permissions`).\n\nYou are a delegated subagent: your permission scope was fixed when you were started and cannot be widened from inside this session — operations that require approval are rejected automatically. When the task needs access beyond that scope, do not retry the denied operation; state the limitation in your reply so the delegating agent can handle it."}],"source":{"kind":"plugin","plugin":"@deepseek-ai/dsh-system-prompt","form":"snapshot","sections":[{"name":"sandbox:policy","text":"Current DSH file policy: danger-full-access. The DSH file sandbox does not restrict file modifications by available operations."},{"name":"approval:policy","text":"Approval prompts are disabled in this session: actions that require approval are rejected automatically — do not request sandbox escalation (do not set `sandbox_permissions`)."},{"name":"subagent:delegation","text":"You are a delegated subagent: your permission scope was fixed when you were started and cannot be widened from inside this session — operations that require approval are rejected automatically. When the task needs access beyond that scope, do not retry the denied operation; state the limitation in your reply so the delegating agent can handle it."}]},"role":"user","id":"1f81ee1b-b08e-4fba-a075-426e41dd03d4"},"surfaceOp":"append"}
+{"type":"user/message","seq":7,"time":1786357538310,"data":{"content":[{"type":"text","text":"Current runtime context. This snapshot supersedes earlier runtime-context snapshots.\n\nCurrent DSH file policy: danger-full-access. The DSH file sandbox does not restrict file modifications by available operations.\n\nApproval prompts are disabled in this session: actions that require approval are rejected automatically — do not request sandbox escalation (do not set `sandbox_permissions`).\n\nYou are a delegated subagent: your permission scope was fixed when you were started and cannot be widened from inside this session — operations that require approval are rejected automatically. When the task needs access beyond that scope, do not retry the denied operation; state the limitation in your reply so the delegating agent can handle it."}],"source":{"kind":"plugin","plugin":"@deepseek-ai/dsh-system-prompt","form":"snapshot","sections":[{"name":"sandbox:policy","text":"Current DSH file policy: danger-full-access. The DSH file sandbox does not restrict file modifications by available operations."},{"name":"approval:policy","text":"Approval prompts are disabled in this session: actions that require approval are rejected automatically — do not request sandbox escalation (do not set `sandbox_permissions`)."},{"name":"subagent:delegation","text":"You are a delegated subagent: your permission scope was fixed when you were started and cannot be widened from inside this session — operations that require approval are rejected automatically. When the task needs access beyond that scope, do not retry the denied operation; state the limitation in your reply so the delegating agent can handle it."}]},"role":"user","id":"10c6c81d-85a2-4c50-a8c2-2f58f309f070"},"surfaceOp":"append"}
 {"type":"session/title","seq":8,"time":1786357538310,"data":{"title":"Reply with exactly DIRECT_CHILD_OK and","messageSeqs":[6],"source":{"kind":"fallback"}}}
 {"type":"request/header","seq":9,"time":1785730458555,"data":{"header":{"config":{"provider":"deepseek-official","model":"deepseek-v4-flash"},"system":"{{system}}","tools":"{{tools}}"},"reason":"initial"}}
 {"type":"request/context","seq":10,"time":1785730458555,"data":{"provider":"deepseek-official","model":"deepseek-v4-flash"}}

examples/acp-agent/tests/snapshots/advanced-toolchain/session.2.jsonl

@@ -6,7 +6,7 @@
 {"type":"subagent/descriptor","seq":4,"time":1786357538469,"data":{"version":2,"mode":"one-shot","provider":"spawn"}}
 {"type":"step/start","seq":5,"time":1786357538470,"data":{"turn":1,"step":1}}
 {"type":"user/message","seq":6,"time":1785730458703,"data":{"content":[{"type":"text","text":"Reply with exactly WORKFLOW_CHILD_OK and nothing else."}],"source":{"kind":"user"},"role":"user","id":"2ac2cc54-9bce-4cfa-a569-a64f51bc30a7"},"surfaceOp":"append"}
-{"type":"user/message","seq":7,"time":1786357538471,"data":{"content":[{"type":"text","text":"Current runtime context. This snapshot supersedes earlier runtime-context snapshots.\n\nCurrent DSH file policy: danger-full-access. The DSH file sandbox does not restrict file modifications by available operations.\n\nApproval prompts are disabled in this session: actions that require approval are rejected automatically — do not request sandbox escalation (do not set `sandbox_permissions`).\n\nYou are a delegated subagent: your permission scope was fixed when you were started and cannot be widened from inside this session — operations that require approval are rejected automatically. When the task needs access beyond that scope, do not retry the denied operation; state the limitation in your reply so the delegating agent can handle it."}],"source":{"kind":"plugin","plugin":"@deepseek-ai/dsh-system-prompt","form":"snapshot","sections":[{"name":"sandbox:policy","text":"Current DSH file policy: danger-full-access. The DSH file sandbox does not restrict file modifications by available operations."},{"name":"approval:policy","text":"Approval prompts are disabled in this session: actions that require approval are rejected automatically — do not request sandbox escalation (do not set `sandbox_permissions`)."},{"name":"subagent:delegation","text":"You are a delegated subagent: your permission scope was fixed when you were started and cannot be widened from inside this session — operations that require approval are rejected automatically. When the task needs access beyond that scope, do not retry the denied operation; state the limitation in your reply so the delegating agent can handle it."}]},"role":"user","id":"dbf0fe20-f0e0-4700-b0fc-d192f5e7b1ca"},"surfaceOp":"append"}
+{"type":"user/message","seq":7,"time":1786357538471,"data":{"content":[{"type":"text","text":"Current runtime context. This snapshot supersedes earlier runtime-context snapshots.\n\nCurrent DSH file policy: danger-full-access. The DSH file sandbox does not restrict file modifications by available operations.\n\nApproval prompts are disabled in this session: actions that require approval are rejected automatically — do not request sandbox escalation (do not set `sandbox_permissions`).\n\nYou are a delegated subagent: your permission scope was fixed when you were started and cannot be widened from inside this session — operations that require approval are rejected automatically. When the task needs access beyond that scope, do not retry the denied operation; state the limitation in your reply so the delegating agent can handle it."}],"source":{"kind":"plugin","plugin":"@deepseek-ai/dsh-system-prompt","form":"snapshot","sections":[{"name":"sandbox:policy","text":"Current DSH file policy: danger-full-access. The DSH file sandbox does not restrict file modifications by available operations."},{"name":"approval:policy","text":"Approval prompts are disabled in this session: actions that require approval are rejected automatically — do not request sandbox escalation (do not set `sandbox_permissions`)."},{"name":"subagent:delegation","text":"You are a delegated subagent: your permission scope was fixed when you were started and cannot be widened from inside this session — operations that require approval are rejected automatically. When the task needs access beyond that scope, do not retry the denied operation; state the limitation in your reply so the delegating agent can handle it."}]},"role":"user","id":"5a8c5ad7-352c-475a-9356-87510cc6b1a8"},"surfaceOp":"append"}
 {"type":"session/title","seq":8,"time":1786357538471,"data":{"title":"Reply with exactly WORKFLOW_CHILD_OK and","messageSeqs":[6],"source":{"kind":"fallback"}}}
 {"type":"request/header","seq":9,"time":1785730458703,"data":{"header":{"config":{"provider":"deepseek-official","model":"deepseek-v4-flash"},"system":"{{system}}","tools":"{{tools}}"},"reason":"initial"}}
 {"type":"request/context","seq":10,"time":1785730458703,"data":{"provider":"deepseek-official","model":"deepseek-v4-flash"}}

examples/acp-agent/tests/snapshots/advanced-toolchain/session.jsonl

@@ -31,12 +31,12 @@
 {"type":"step/end","seq":29,"time":1785730458520,"data":{"turn":1,"step":2}}
 {"type":"step/start","seq":30,"time":1785730458527,"data":{"turn":1,"step":3}}
 {"type":"assistant/chunk","seq":31,"time":1783950000029,"data":{"turn":1,"step":3,"chunk":{"type":"block-start","index":0,"blockType":"tool-call"}}}
-{"type":"assistant/chunk","seq":32,"time":1783950000030,"data":{"turn":1,"step":3,"chunk":{"type":"tool-call-delta","index":0,"id":"advanced-direct-child","name":"subagent","argumentsDelta":"{\"description\":\"Check direct child\",\"prompt\":\"Reply with exactly DIRECT_CHILD_OK and nothing else.\"}"}}}
-{"type":"assistant/chunk","seq":33,"time":1785036891179,"data":{"turn":1,"step":3,"chunk":{"type":"block-end","index":0,"block":{"type":"tool-call","id":"advanced-direct-child","name":"subagent","arguments":"{\"description\":\"Check direct child\",\"prompt\":\"Reply with exactly DIRECT_CHILD_OK and nothing else.\"}"}}}}
+{"type":"assistant/chunk","seq":32,"time":1783950000030,"data":{"turn":1,"step":3,"chunk":{"type":"tool-call-delta","index":0,"id":"advanced-direct-child","name":"subagent","argumentsDelta":"{\"description\":\"Check direct child\",\"prompt\":\"Reply with exactly DIRECT_CHILD_OK and nothing else.\",\"run_in_background\":false}"}}}
+{"type":"assistant/chunk","seq":33,"time":1785036891179,"data":{"turn":1,"step":3,"chunk":{"type":"block-end","index":0,"block":{"type":"tool-call","id":"advanced-direct-child","name":"subagent","arguments":"{\"description\":\"Check direct child\",\"prompt\":\"Reply with exactly DIRECT_CHILD_OK and nothing else.\",\"run_in_background\":false}"}}}}
 {"type":"assistant/chunk","seq":34,"time":1785498801872,"data":{"turn":1,"step":3,"chunk":{"type":"usage","usage":{"inputTokens":3,"outputTokens":3}}}}
 {"type":"assistant/chunk","seq":35,"time":1785730458531,"data":{"turn":1,"step":3,"chunk":{"type":"finish","reason":{"kind":"tool-calls"}}}}
-{"type":"assistant/message","seq":36,"time":1785730458531,"data":{"turn":1,"step":3,"message":{"role":"assistant","content":[{"type":"tool-call","id":"advanced-direct-child","name":"subagent","arguments":"{\"description\":\"Check direct child\",\"prompt\":\"Reply with exactly DIRECT_CHILD_OK and nothing else.\"}"}],"source":{"kind":"model","provider":"deepseek-official","model":"deepseek-v4-flash"},"id":"51fe1d59-eebc-457b-a072-fe217546ff04"},"usage":{"inputTokens":3,"outputTokens":3}},"sourceEventSeqs":[31,32,33,34,35],"surfaceOp":"append"}
-{"type":"tool/call","seq":37,"time":1785730458531,"data":{"turn":1,"step":3,"callId":"advanced-direct-child","name":"subagent","arguments":"{\"description\":\"Check direct child\",\"prompt\":\"Reply with exactly DIRECT_CHILD_OK and nothing else.\"}"}}
+{"type":"assistant/message","seq":36,"time":1785730458531,"data":{"turn":1,"step":3,"message":{"role":"assistant","content":[{"type":"tool-call","id":"advanced-direct-child","name":"subagent","arguments":"{\"description\":\"Check direct child\",\"prompt\":\"Reply with exactly DIRECT_CHILD_OK and nothing else.\",\"run_in_background\":false}"}],"source":{"kind":"model","provider":"deepseek-official","model":"deepseek-v4-flash"},"id":"51fe1d59-eebc-457b-a072-fe217546ff04"},"usage":{"inputTokens":3,"outputTokens":3}},"sourceEventSeqs":[31,32,33,34,35],"surfaceOp":"append"}
+{"type":"tool/call","seq":37,"time":1785730458531,"data":{"turn":1,"step":3,"callId":"advanced-direct-child","name":"subagent","arguments":"{\"description\":\"Check direct child\",\"prompt\":\"Reply with exactly DIRECT_CHILD_OK and nothing else.\",\"run_in_background\":false}"}}
 {"type":"tool/result","seq":38,"time":1785730458562,"data":{"turn":1,"step":3,"message":{"source":{"kind":"tool","callId":"advanced-direct-child"},"content":[{"type":"tool-result","toolCallId":"advanced-direct-child","content":[{"type":"text","text":"DIRECT_CHILD_OK"}],"isError":false}],"role":"user","id":"09028579-5ae5-4d57-955e-02504f4dfc2a"}},"sourceEventSeqs":[37],"surfaceOp":"append"}
 {"type":"step/end","seq":39,"time":1785730458563,"data":{"turn":1,"step":3}}
 {"type":"step/start","seq":40,"time":1785730458572,"data":{"turn":1,"step":4}}

examples/acp-agent/tests/snapshots/advanced-toolchain/system-prompt.expected.md

@@ -21,6 +21,8 @@ Use the workflow tool ONLY when the user explicitly asks for a workflow or for l
 
 Use the ralph tool ONLY when the direct human explicitly asks for a Ralph loop or fresh-agent iterative execution. Each Ralph round starts a fresh child with no conversation seed and uses the shared workspace as durable memory. Completion and blockers are worker reports, not independent evaluation. Use same-session goal tools for ordinary long-running objectives, and plain subagents or workflows for bounded delegation and fan-out.
 
+Use subagent in the background by default. Start independent delegations together in one assistant message and continue useful work while they run. Set `run_in_background: false` only when your next action depends on that subagent's result. When a background run settles, the runtime sends you a notice containing its outcome and any final assistant message.
+
 ## Writing code for run_code
 
 Pass `run_code` the body of an async TypeScript function (erasable syntax only — no `enum` or namespaces; type annotations are advisory, the code runs type-stripped). Inside the program:
@@ -132,16 +134,16 @@ interface ToolArgsMap {
     /** The exact skill name from the available skills list. */
     name: string;
   } & Record<string, JsonValue>;
-  /** Delegate a self-contained task to a subagent (a separate agent that works in its own context) and return its final result. Use this to offload focused, independent work — research, a scoped implementation, an analysis — so it does not consume this conversation's context. The subagent runs to completion and you receive only its final answer, not its intermediate steps. Give it a complete, standalone prompt: it does not see this conversation. Set `run_in_background: true` to start a background subagent that keeps its conversation: this call returns only its subagent id, and the subagent works on its own from there. You are told when it finishes, so never poll or wait on it; `send_message` sends it more work. */
+  /** Delegate a self-contained task to a subagent (a separate agent that works in its own context) to offload focused, independent work — research, a scoped implementation, an analysis — so it does not consume this conversation's context. The subagent returns its result, not its intermediate steps. Give it a complete, standalone prompt: it does not see this conversation. This tool runs in the background by default, immediately returns a durable subagent id, and keeps the child conversation available for later turns. When that run settles, the runtime sends the parent a notice containing its outcome and any final assistant message; `send_message` starts a later turn in the same child conversation. Set `run_in_background: false` only when your next action depends on receiving the result. */
   subagent: {
     /** A short (3-5 word) description of the delegated task, for display. */
     description: string;
     /** The complete, self-contained task for the subagent. It does not share this conversation's context, so include everything it needs. */
     prompt: string;
-    /** Run as a background subagent that keeps its conversation and return only its subagent id. This call does not wait for it; you are told when it finishes. Send it more work with send_message. */
+    /** Whether to run in the background and return a durable subagent id immediately. Defaults to true. Set false to wait for the result when your next action depends on it. */
     run_in_background?: boolean;
   } & Record<string, JsonValue>;
-  /** Delegate a task to a subagent that inherits this conversation: a child agent seeded with all completed turns so far (it does not see the current in-flight turn), returning only its final result. Use this when the subtask builds on this conversation's context — a follow-up analysis, a review, a continuation — without consuming this conversation's context for the work itself. You receive only its final answer, not its intermediate steps. */
+  /** Delegate a task to a subagent that inherits this conversation: a child agent seeded with all completed turns so far (it does not see the current in-flight turn). Use this when the subtask builds on this conversation's context — a follow-up analysis, a review, a continuation — without consuming this conversation's context for the work itself. You receive its result, not its intermediate steps. This call waits for the subagent and returns its result. */
   subagent_fork: {
     /** A short (3-5 word) description of the delegated task, for display. */
     description: string;

examples/acp-agent/tests/snapshots/advanced-toolchain/tool-schemas.expected.json

@@ -309,7 +309,7 @@
     },
     {
       "name": "subagent",
-      "description": "Delegate a self-contained task to a subagent (a separate agent that works in its own context) and return its final result. Use this to offload focused, independent work — research, a scoped implementation, an analysis — so it does not consume this conversation's context. The subagent runs to completion and you receive only its final answer, not its intermediate steps. Give it a complete, standalone prompt: it does not see this conversation. Set `run_in_background: true` to start a background subagent that keeps its conversation: this call returns only its subagent id, and the subagent works on its own from there. You are told when it finishes, so never poll or wait on it; `send_message` sends it more work.",
+      "description": "Delegate a self-contained task to a subagent (a separate agent that works in its own context) to offload focused, independent work — research, a scoped implementation, an analysis — so it does not consume this conversation's context. The subagent returns its result, not its intermediate steps. Give it a complete, standalone prompt: it does not see this conversation. This tool runs in the background by default, immediately returns a durable subagent id, and keeps the child conversation available for later turns. When that run settles, the runtime sends the parent a notice containing its outcome and any final assistant message; `send_message` starts a later turn in the same child conversation. Set `run_in_background: false` only when your next action depends on receiving the result.",
       "parameters": {
         "type": "object",
         "properties": {
@@ -323,7 +323,7 @@
           },
           "run_in_background": {
             "type": "boolean",
-            "description": "Run as a background subagent that keeps its conversation and return only its subagent id. This call does not wait for it; you are told when it finishes. Send it more work with send_message."
+            "description": "Whether to run in the background and return a durable subagent id immediately. Defaults to true. Set false to wait for the result when your next action depends on it."
           }
         },
         "required": [
@@ -334,7 +334,7 @@
     },
     {
       "name": "subagent_fork",
-      "description": "Delegate a task to a subagent that inherits this conversation: a child agent seeded with all completed turns so far (it does not see the current in-flight turn), returning only its final result. Use this when the subtask builds on this conversation's context — a follow-up analysis, a review, a continuation — without consuming this conversation's context for the work itself. You receive only its final answer, not its intermediate steps.",
+      "description": "Delegate a task to a subagent that inherits this conversation: a child agent seeded with all completed turns so far (it does not see the current in-flight turn). Use this when the subtask builds on this conversation's context — a follow-up analysis, a review, a continuation — without consuming this conversation's context for the work itself. You receive its result, not its intermediate steps. This call waits for the subagent and returns its result.",
       "parameters": {
         "type": "object",
         "properties": {

examples/acp-agent/tests/snapshots/both-mode-turn/tool-schemas.expected.json

@@ -252,7 +252,7 @@
     },
     {
       "name": "subagent",
-      "description": "Delegate a self-contained task to a subagent (a separate agent that works in its own context) and return its final result. Use this to offload focused, independent work — research, a scoped implementation, an analysis — so it does not consume this conversation's context. The subagent runs to completion and you receive only its final answer, not its intermediate steps. Give it a complete, standalone prompt: it does not see this conversation. Set `run_in_background: true` to start a background subagent that keeps its conversation: this call returns only its subagent id, and the subagent works on its own from there. You are told when it finishes, so never poll or wait on it; `send_message` sends it more work.",
+      "description": "Delegate a self-contained task to a subagent (a separate agent that works in its own context) to offload focused, independent work — research, a scoped implementation, an analysis — so it does not consume this conversation's context. The subagent returns its result, not its intermediate steps. Give it a complete, standalone prompt: it does not see this conversation. This tool runs in the background by default, immediately returns a durable subagent id, and keeps the child conversation available for later turns. When that run settles, the runtime sends the parent a notice containing its outcome and any final assistant message; `send_message` starts a later turn in the same child conversation. Set `run_in_background: false` only when your next action depends on receiving the result.",
       "parameters": {
         "type": "object",
         "properties": {
@@ -266,7 +266,7 @@
           },
           "run_in_background": {
             "type": "boolean",
-            "description": "Run as a background subagent that keeps its conversation and return only its subagent id. This call does not wait for it; you are told when it finishes. Send it more work with send_message."
+            "description": "Whether to run in the background and return a durable subagent id immediately. Defaults to true. Set false to wait for the result when your next action depends on it."
           }
         },
         "required": [
@@ -277,7 +277,7 @@
     },
     {
       "name": "subagent_fork",
-      "description": "Delegate a task to a subagent that inherits this conversation: a child agent seeded with all completed turns so far (it does not see the current in-flight turn), returning only its final result. Use this when the subtask builds on this conversation's context — a follow-up analysis, a review, a continuation — without consuming this conversation's context for the work itself. You receive only its final answer, not its intermediate steps.",
+      "description": "Delegate a task to a subagent that inherits this conversation: a child agent seeded with all completed turns so far (it does not see the current in-flight turn). Use this when the subtask builds on this conversation's context — a follow-up analysis, a review, a continuation — without consuming this conversation's context for the work itself. You receive its result, not its intermediate steps. This call waits for the subagent and returns its result.",
       "parameters": {
         "type": "object",
         "properties": {

examples/acp-agent/tests/snapshots/code-mode-turn/system-prompt.expected.md

@@ -21,6 +21,8 @@ Use the workflow tool ONLY when the user explicitly asks for a workflow or for l
 
 Use the ralph tool ONLY when the direct human explicitly asks for a Ralph loop or fresh-agent iterative execution. Each Ralph round starts a fresh child with no conversation seed and uses the shared workspace as durable memory. Completion and blockers are worker reports, not independent evaluation. Use same-session goal tools for ordinary long-running objectives, and plain subagents or workflows for bounded delegation and fan-out.
 
+Use subagent in the background by default. Start independent delegations together in one assistant message and continue useful work while they run. Set `run_in_background: false` only when your next action depends on that subagent's result. When a background run settles, the runtime sends you a notice containing its outcome and any final assistant message.
+
 ## Writing code for run_code
 
 Pass `run_code` the body of an async TypeScript function (erasable syntax only — no `enum` or namespaces; type annotations are advisory, the code runs type-stripped). Inside the program:
@@ -115,16 +117,16 @@ interface ToolArgsMap {
     /** The exact skill name from the available skills list. */
     name: string;
   } & Record<string, JsonValue>;
-  /** Delegate a self-contained task to a subagent (a separate agent that works in its own context) and return its final result. Use this to offload focused, independent work — research, a scoped implementation, an analysis — so it does not consume this conversation's context. The subagent runs to completion and you receive only its final answer, not its intermediate steps. Give it a complete, standalone prompt: it does not see this conversation. Set `run_in_background: true` to start a background subagent that keeps its conversation: this call returns only its subagent id, and the subagent works on its own from there. You are told when it finishes, so never poll or wait on it; `send_message` sends it more work. */
+  /** Delegate a self-contained task to a subagent (a separate agent that works in its own context) to offload focused, independent work — research, a scoped implementation, an analysis — so it does not consume this conversation's context. The subagent returns its result, not its intermediate steps. Give it a complete, standalone prompt: it does not see this conversation. This tool runs in the background by default, immediately returns a durable subagent id, and keeps the child conversation available for later turns. When that run settles, the runtime sends the parent a notice containing its outcome and any final assistant message; `send_message` starts a later turn in the same child conversation. Set `run_in_background: false` only when your next action depends on receiving the result. */
   subagent: {
     /** A short (3-5 word) description of the delegated task, for display. */
     description: string;
     /** The complete, self-contained task for the subagent. It does not share this conversation's context, so include everything it needs. */
     prompt: string;
-    /** Run as a background subagent that keeps its conversation and return only its subagent id. This call does not wait for it; you are told when it finishes. Send it more work with send_message. */
+    /** Whether to run in the background and return a durable subagent id immediately. Defaults to true. Set false to wait for the result when your next action depends on it. */
     run_in_background?: boolean;
   } & Record<string, JsonValue>;
-  /** Delegate a task to a subagent that inherits this conversation: a child agent seeded with all completed turns so far (it does not see the current in-flight turn), returning only its final result. Use this when the subtask builds on this conversation's context — a follow-up analysis, a review, a continuation — without consuming this conversation's context for the work itself. You receive only its final answer, not its intermediate steps. */
+  /** Delegate a task to a subagent that inherits this conversation: a child agent seeded with all completed turns so far (it does not see the current in-flight turn). Use this when the subtask builds on this conversation's context — a follow-up analysis, a review, a continuation — without consuming this conversation's context for the work itself. You receive its result, not its intermediate steps. This call waits for the subagent and returns its result. */
   subagent_fork: {
     /** A short (3-5 word) description of the delegated task, for display. */
     description: string;

examples/acp-agent/tests/snapshots/lsp-definition/system-prompt.expected.md

@@ -22,3 +22,5 @@ Use goal tools for one long-running completion objective in the current session.
 Use the workflow tool ONLY when the user explicitly asks for a workflow or for large multi-agent orchestration: you write a JavaScript script (the tool description documents the exact format) that fans work out across many subagents with phases and structured results. For one or two delegations, prefer plain subagent calls.
 
 Use the ralph tool ONLY when the direct human explicitly asks for a Ralph loop or fresh-agent iterative execution. Each Ralph round starts a fresh child with no conversation seed and uses the shared workspace as durable memory. Completion and blockers are worker reports, not independent evaluation. Use same-session goal tools for ordinary long-running objectives, and plain subagents or workflows for bounded delegation and fan-out.
+
+Use subagent in the background by default. Start independent delegations together in one assistant message and continue useful work while they run. Set `run_in_background: false` only when your next action depends on that subagent's result. When a background run settles, the runtime sends you a notice containing its outcome and any final assistant message.

examples/acp-agent/tests/snapshots/lsp-definition/tool-schemas.expected.json

@@ -268,7 +268,7 @@
     },
     {
       "name": "subagent",
-      "description": "Delegate a self-contained task to a subagent (a separate agent that works in its own context) and return its final result. Use this to offload focused, independent work — research, a scoped implementation, an analysis — so it does not consume this conversation's context. The subagent runs to completion and you receive only its final answer, not its intermediate steps. Give it a complete, standalone prompt: it does not see this conversation. Set `run_in_background: true` to start a background subagent that keeps its conversation: this call returns only its subagent id, and the subagent works on its own from there. You are told when it finishes, so never poll or wait on it; `send_message` sends it more work.",
+      "description": "Delegate a self-contained task to a subagent (a separate agent that works in its own context) to offload focused, independent work — research, a scoped implementation, an analysis — so it does not consume this conversation's context. The subagent returns its result, not its intermediate steps. Give it a complete, standalone prompt: it does not see this conversation. This tool runs in the background by default, immediately returns a durable subagent id, and keeps the child conversation available for later turns. When that run settles, the runtime sends the parent a notice containing its outcome and any final assistant message; `send_message` starts a later turn in the same child conversation. Set `run_in_background: false` only when your next action depends on receiving the result.",
       "parameters": {
         "type": "object",
         "properties": {
@@ -282,7 +282,7 @@
           },
           "run_in_background": {
             "type": "boolean",
-            "description": "Run as a background subagent that keeps its conversation and return only its subagent id. This call does not wait for it; you are told when it finishes. Send it more work with send_message."
+            "description": "Whether to run in the background and return a durable subagent id immediately. Defaults to true. Set false to wait for the result when your next action depends on it."
           }
         },
         "required": [
@@ -293,7 +293,7 @@
     },
     {
       "name": "subagent_fork",
-      "description": "Delegate a task to a subagent that inherits this conversation: a child agent seeded with all completed turns so far (it does not see the current in-flight turn), returning only its final result. Use this when the subtask builds on this conversation's context — a follow-up analysis, a review, a continuation — without consuming this conversation's context for the work itself. You receive only its final answer, not its intermediate steps.",
+      "description": "Delegate a task to a subagent that inherits this conversation: a child agent seeded with all completed turns so far (it does not see the current in-flight turn). Use this when the subtask builds on this conversation's context — a follow-up analysis, a review, a continuation — without consuming this conversation's context for the work itself. You receive its result, not its intermediate steps. This call waits for the subagent and returns its result.",
       "parameters": {
         "type": "object",
         "properties": {

examples/acp-agent/tests/snapshots/product-subagent-both/tool-schemas.expected.json

@@ -231,7 +231,7 @@
     },
     {
       "name": "subagent",
-      "description": "Delegate a self-contained task to a subagent (a separate agent that works in its own context) and return its final result. Use this to offload focused, independent work — research, a scoped implementation, an analysis — so it does not consume this conversation's context. The subagent runs to completion and you receive only its final answer, not its intermediate steps. Give it a complete, standalone prompt: it does not see this conversation. Set `run_in_background: true` to start a background subagent that keeps its conversation: this call returns only its subagent id, and the subagent works on its own from there. You are told when it finishes, so never poll or wait on it; `send_message` sends it more work.",
+      "description": "Delegate a self-contained task to a subagent (a separate agent that works in its own context) to offload focused, independent work — research, a scoped implementation, an analysis — so it does not consume this conversation's context. The subagent returns its result, not its intermediate steps. Give it a complete, standalone prompt: it does not see this conversation. This tool runs in the background by default, immediately returns a durable subagent id, and keeps the child conversation available for later turns. When that run settles, the runtime sends the parent a notice containing its outcome and any final assistant message; `send_message` starts a later turn in the same child conversation. Set `run_in_background: false` only when your next action depends on receiving the result.",
       "parameters": {
         "type": "object",
         "properties": {
@@ -245,7 +245,7 @@
           },
           "run_in_background": {
             "type": "boolean",
-            "description": "Run as a background subagent that keeps its conversation and return only its subagent id. This call does not wait for it; you are told when it finishes. Send it more work with send_message."
+            "description": "Whether to run in the background and return a durable subagent id immediately. Defaults to true. Set false to wait for the result when your next action depends on it."
           }
         },
         "required": [
@@ -256,7 +256,7 @@
     },
     {
       "name": "subagent_claude_code",
-      "description": "Delegate a self-contained task to a subagent (a separate agent that works in its own context) and return its final result. Use this to offload focused, independent work — research, a scoped implementation, an analysis — so it does not consume this conversation's context. The subagent runs to completion and you receive only its final answer, not its intermediate steps. Give it a complete, standalone prompt: it does not see this conversation.",
+      "description": "Delegate a self-contained task to a subagent (a separate agent that works in its own context) to offload focused, independent work — research, a scoped implementation, an analysis — so it does not consume this conversation's context. The subagent returns its result, not its intermediate steps. Give it a complete, standalone prompt: it does not see this conversation. This call waits for the subagent and returns its result.",
       "parameters": {
         "type": "object",
         "properties": {
@@ -277,7 +277,7 @@
     },
     {
       "name": "subagent_codex",
-      "description": "Delegate a self-contained task to a subagent (a separate agent that works in its own context) and return its final result. Use this to offload focused, independent work — research, a scoped implementation, an analysis — so it does not consume this conversation's context. The subagent runs to completion and you receive only its final answer, not its intermediate steps. Give it a complete, standalone prompt: it does not see this conversation.",
+      "description": "Delegate a self-contained task to a subagent (a separate agent that works in its own context) to offload focused, independent work — research, a scoped implementation, an analysis — so it does not consume this conversation's context. The subagent returns its result, not its intermediate steps. Give it a complete, standalone prompt: it does not see this conversation. This call waits for the subagent and returns its result.",
       "parameters": {
         "type": "object",
         "properties": {
@@ -298,7 +298,7 @@
     },
     {
       "name": "subagent_fork",
-      "description": "Delegate a task to a subagent that inherits this conversation: a child agent seeded with all completed turns so far (it does not see the current in-flight turn), returning only its final result. Use this when the subtask builds on this conversation's context — a follow-up analysis, a review, a continuation — without consuming this conversation's context for the work itself. You receive only its final answer, not its intermediate steps.",
+      "description": "Delegate a task to a subagent that inherits this conversation: a child agent seeded with all completed turns so far (it does not see the current in-flight turn). Use this when the subtask builds on this conversation's context — a follow-up analysis, a review, a continuation — without consuming this conversation's context for the work itself. You receive its result, not its intermediate steps. This call waits for the subagent and returns its result.",
       "parameters": {
         "type": "object",
         "properties": {

examples/acp-agent/tests/snapshots/product-subagent-codex/system-prompt.expected.md

@@ -20,3 +20,5 @@ Use goal tools for one long-running completion objective in the current session.
 Use the workflow tool ONLY when the user explicitly asks for a workflow or for large multi-agent orchestration: you write a JavaScript script (the tool description documents the exact format) that fans work out across many subagents with phases and structured results. For one or two delegations, prefer plain subagent calls.
 
 Use the ralph tool ONLY when the direct human explicitly asks for a Ralph loop or fresh-agent iterative execution. Each Ralph round starts a fresh child with no conversation seed and uses the shared workspace as durable memory. Completion and blockers are worker reports, not independent evaluation. Use same-session goal tools for ordinary long-running objectives, and plain subagents or workflows for bounded delegation and fan-out.
+
+Use subagent in the background by default. Start independent delegations together in one assistant message and continue useful work while they run. Set `run_in_background: false` only when your next action depends on that subagent's result. When a background run settles, the runtime sends you a notice containing its outcome and any final assistant message.

examples/acp-agent/tests/snapshots/product-subagent-codex/tool-schemas.expected.json

@@ -231,7 +231,7 @@
     },
     {
       "name": "subagent",
-      "description": "Delegate a self-contained task to a subagent (a separate agent that works in its own context) and return its final result. Use this to offload focused, independent work — research, a scoped implementation, an analysis — so it does not consume this conversation's context. The subagent runs to completion and you receive only its final answer, not its intermediate steps. Give it a complete, standalone prompt: it does not see this conversation. Set `run_in_background: true` to start a background subagent that keeps its conversation: this call returns only its subagent id, and the subagent works on its own from there. You are told when it finishes, so never poll or wait on it; `send_message` sends it more work.",
+      "description": "Delegate a self-contained task to a subagent (a separate agent that works in its own context) to offload focused, independent work — research, a scoped implementation, an analysis — so it does not consume this conversation's context. The subagent returns its result, not its intermediate steps. Give it a complete, standalone prompt: it does not see this conversation. This tool runs in the background by default, immediately returns a durable subagent id, and keeps the child conversation available for later turns. When that run settles, the runtime sends the parent a notice containing its outcome and any final assistant message; `send_message` starts a later turn in the same child conversation. Set `run_in_background: false` only when your next action depends on receiving the result.",
       "parameters": {
         "type": "object",
         "properties": {
@@ -245,7 +245,7 @@
           },
           "run_in_background": {
             "type": "boolean",
-            "description": "Run as a background subagent that keeps its conversation and return only its subagent id. This call does not wait for it; you are told when it finishes. Send it more work with send_message."
+            "description": "Whether to run in the background and return a durable subagent id immediately. Defaults to true. Set false to wait for the result when your next action depends on it."
           }
         },
         "required": [
@@ -256,7 +256,7 @@
     },
     {
       "name": "subagent_codex",
-      "description": "Delegate a self-contained task to a subagent (a separate agent that works in its own context) and return its final result. Use this to offload focused, independent work — research, a scoped implementation, an analysis — so it does not consume this conversation's context. The subagent runs to completion and you receive only its final answer, not its intermediate steps. Give it a complete, standalone prompt: it does not see this conversation.",
+      "description": "Delegate a self-contained task to a subagent (a separate agent that works in its own context) to offload focused, independent work — research, a scoped implementation, an analysis — so it does not consume this conversation's context. The subagent returns its result, not its intermediate steps. Give it a complete, standalone prompt: it does not see this conversation. This call waits for the subagent and returns its result.",
       "parameters": {
         "type": "object",
         "properties": {
@@ -277,7 +277,7 @@
     },
     {
       "name": "subagent_fork",
-      "description": "Delegate a task to a subagent that inherits this conversation: a child agent seeded with all completed turns so far (it does not see the current in-flight turn), returning only its final result. Use this when the subtask builds on this conversation's context — a follow-up analysis, a review, a continuation — without consuming this conversation's context for the work itself. You receive only its final answer, not its intermediate steps.",
+      "description": "Delegate a task to a subagent that inherits this conversation: a child agent seeded with all completed turns so far (it does not see the current in-flight turn). Use this when the subtask builds on this conversation's context — a follow-up analysis, a review, a continuation — without consuming this conversation's context for the work itself. You receive its result, not its intermediate steps. This call waits for the subagent and returns its result.",
       "parameters": {
         "type": "object",
         "properties": {

examples/acp-agent/tests/snapshots/pty-tools/system-prompt.expected.md

@@ -22,3 +22,5 @@ Use goal tools for one long-running completion objective in the current session.
 Use the workflow tool ONLY when the user explicitly asks for a workflow or for large multi-agent orchestration: you write a JavaScript script (the tool description documents the exact format) that fans work out across many subagents with phases and structured results. For one or two delegations, prefer plain subagent calls.
 
 Use the ralph tool ONLY when the direct human explicitly asks for a Ralph loop or fresh-agent iterative execution. Each Ralph round starts a fresh child with no conversation seed and uses the shared workspace as durable memory. Completion and blockers are worker reports, not independent evaluation. Use same-session goal tools for ordinary long-running objectives, and plain subagents or workflows for bounded delegation and fan-out.
+
+Use subagent in the background by default. Start independent delegations together in one assistant message and continue useful work while they run. Set `run_in_background: false` only when your next action depends on that subagent's result. When a background run settles, the runtime sends you a notice containing its outcome and any final assistant message.

examples/acp-agent/tests/snapshots/pty-tools/tool-schemas.expected.json

@@ -231,7 +231,7 @@
     },
     {
       "name": "subagent",
-      "description": "Delegate a self-contained task to a subagent (a separate agent that works in its own context) and return its final result. Use this to offload focused, independent work — research, a scoped implementation, an analysis — so it does not consume this conversation's context. The subagent runs to completion and you receive only its final answer, not its intermediate steps. Give it a complete, standalone prompt: it does not see this conversation. Set `run_in_background: true` to start a background subagent that keeps its conversation: this call returns only its subagent id, and the subagent works on its own from there. You are told when it finishes, so never poll or wait on it; `send_message` sends it more work.",
+      "description": "Delegate a self-contained task to a subagent (a separate agent that works in its own context) to offload focused, independent work — research, a scoped implementation, an analysis — so it does not consume this conversation's context. The subagent returns its result, not its intermediate steps. Give it a complete, standalone prompt: it does not see this conversation. This tool runs in the background by default, immediately returns a durable subagent id, and keeps the child conversation available for later turns. When that run settles, the runtime sends the parent a notice containing its outcome and any final assistant message; `send_message` starts a later turn in the same child conversation. Set `run_in_background: false` only when your next action depends on receiving the result.",
       "parameters": {
         "type": "object",
         "properties": {
@@ -245,7 +245,7 @@
           },
           "run_in_background": {
             "type": "boolean",
-            "description": "Run as a background subagent that keeps its conversation and return only its subagent id. This call does not wait for it; you are told when it finishes. Send it more work with send_message."
+            "description": "Whether to run in the background and return a durable subagent id immediately. Defaults to true. Set false to wait for the result when your next action depends on it."
           }
         },
         "required": [
@@ -256,7 +256,7 @@
     },
     {
       "name": "subagent_fork",
-      "description": "Delegate a task to a subagent that inherits this conversation: a child agent seeded with all completed turns so far (it does not see the current in-flight turn), returning only its final result. Use this when the subtask builds on this conversation's context — a follow-up analysis, a review, a continuation — without consuming this conversation's context for the work itself. You receive only its final answer, not its intermediate steps.",
+      "description": "Delegate a task to a subagent that inherits this conversation: a child agent seeded with all completed turns so far (it does not see the current in-flight turn). Use this when the subtask builds on this conversation's context — a follow-up analysis, a review, a continuation — without consuming this conversation's context for the work itself. You receive its result, not its intermediate steps. This call waits for the subagent and returns its result.",
       "parameters": {
         "type": "object",
         "properties": {

examples/acp-agent/tests/snapshots/read-image/tool-schemas.expected.json

@@ -247,7 +247,7 @@
     },
     {
       "name": "subagent",
-      "description": "Delegate a self-contained task to a subagent (a separate agent that works in its own context) and return its final result. Use this to offload focused, independent work — research, a scoped implementation, an analysis — so it does not consume this conversation's context. The subagent runs to completion and you receive only its final answer, not its intermediate steps. Give it a complete, standalone prompt: it does not see this conversation. Set `run_in_background: true` to start a background subagent that keeps its conversation: this call returns only its subagent id, and the subagent works on its own from there. You are told when it finishes, so never poll or wait on it; `send_message` sends it more work.",
+      "description": "Delegate a self-contained task to a subagent (a separate agent that works in its own context) to offload focused, independent work — research, a scoped implementation, an analysis — so it does not consume this conversation's context. The subagent returns its result, not its intermediate steps. Give it a complete, standalone prompt: it does not see this conversation. This tool runs in the background by default, immediately returns a durable subagent id, and keeps the child conversation available for later turns. When that run settles, the runtime sends the parent a notice containing its outcome and any final assistant message; `send_message` starts a later turn in the same child conversation. Set `run_in_background: false` only when your next action depends on receiving the result.",
       "parameters": {
         "type": "object",
         "properties": {
@@ -261,7 +261,7 @@
           },
           "run_in_background": {
             "type": "boolean",
-            "description": "Run as a background subagent that keeps its conversation and return only its subagent id. This call does not wait for it; you are told when it finishes. Send it more work with send_message."
+            "description": "Whether to run in the background and return a durable subagent id immediately. Defaults to true. Set false to wait for the result when your next action depends on it."
           }
         },
         "required": [
@@ -272,7 +272,7 @@
     },
     {
       "name": "subagent_fork",
-      "description": "Delegate a task to a subagent that inherits this conversation: a child agent seeded with all completed turns so far (it does not see the current in-flight turn), returning only its final result. Use this when the subtask builds on this conversation's context — a follow-up analysis, a review, a continuation — without consuming this conversation's context for the work itself. You receive only its final answer, not its intermediate steps.",
+      "description": "Delegate a task to a subagent that inherits this conversation: a child agent seeded with all completed turns so far (it does not see the current in-flight turn). Use this when the subtask builds on this conversation's context — a follow-up analysis, a review, a continuation — without consuming this conversation's context for the work itself. You receive its result, not its intermediate steps. This call waits for the subagent and returns its result.",
       "parameters": {
         "type": "object",
         "properties": {

examples/acp-agent/tests/snapshots/session-query-spill/system-prompt.expected.md

@@ -22,3 +22,5 @@ Use goal tools for one long-running completion objective in the current session.
 Use the workflow tool ONLY when the user explicitly asks for a workflow or for large multi-agent orchestration: you write a JavaScript script (the tool description documents the exact format) that fans work out across many subagents with phases and structured results. For one or two delegations, prefer plain subagent calls.
 
 Use the ralph tool ONLY when the direct human explicitly asks for a Ralph loop or fresh-agent iterative execution. Each Ralph round starts a fresh child with no conversation seed and uses the shared workspace as durable memory. Completion and blockers are worker reports, not independent evaluation. Use same-session goal tools for ordinary long-running objectives, and plain subagents or workflows for bounded delegation and fan-out.
+
+Use subagent in the background by default. Start independent delegations together in one assistant message and continue useful work while they run. Set `run_in_background: false` only when your next action depends on that subagent's result. When a background run settles, the runtime sends you a notice containing its outcome and any final assistant message.

examples/acp-agent/tests/snapshots/session-query-spill/tool-schemas.expected.json

@@ -435,7 +435,7 @@
     },
     {
       "name": "subagent",
-      "description": "Delegate a self-contained task to a subagent (a separate agent that works in its own context) and return its final result. Use this to offload focused, independent work — research, a scoped implementation, an analysis — so it does not consume this conversation's context. The subagent runs to completion and you receive only its final answer, not its intermediate steps. Give it a complete, standalone prompt: it does not see this conversation. Set `run_in_background: true` to start a background subagent that keeps its conversation: this call returns only its subagent id, and the subagent works on its own from there. You are told when it finishes, so never poll or wait on it; `send_message` sends it more work.",
+      "description": "Delegate a self-contained task to a subagent (a separate agent that works in its own context) to offload focused, independent work — research, a scoped implementation, an analysis — so it does not consume this conversation's context. The subagent returns its result, not its intermediate steps. Give it a complete, standalone prompt: it does not see this conversation. This tool runs in the background by default, immediately returns a durable subagent id, and keeps the child conversation available for later turns. When that run settles, the runtime sends the parent a notice containing its outcome and any final assistant message; `send_message` starts a later turn in the same child conversation. Set `run_in_background: false` only when your next action depends on receiving the result.",
       "parameters": {
         "type": "object",
         "properties": {
@@ -449,7 +449,7 @@
           },
           "run_in_background": {
             "type": "boolean",
-            "description": "Run as a background subagent that keeps its conversation and return only its subagent id. This call does not wait for it; you are told when it finishes. Send it more work with send_message."
+            "description": "Whether to run in the background and return a durable subagent id immediately. Defaults to true. Set false to wait for the result when your next action depends on it."
           }
         },
         "required": [
@@ -460,7 +460,7 @@
     },
     {
       "name": "subagent_fork",
-      "description": "Delegate a task to a subagent that inherits this conversation: a child agent seeded with all completed turns so far (it does not see the current in-flight turn), returning only its final result. Use this when the subtask builds on this conversation's context — a follow-up analysis, a review, a continuation — without consuming this conversation's context for the work itself. You receive only its final answer, not its intermediate steps.",
+      "description": "Delegate a task to a subagent that inherits this conversation: a child agent seeded with all completed turns so far (it does not see the current in-flight turn). Use this when the subtask builds on this conversation's context — a follow-up analysis, a review, a continuation — without consuming this conversation's context for the work itself. You receive its result, not its intermediate steps. This call waits for the subagent and returns its result.",
       "parameters": {
         "type": "object",
         "properties": {

examples/acp-agent/tests/snapshots/subagent-child-question-rejection/session.jsonl

@@ -9,13 +9,13 @@
 {"type":"request/header","seq":7,"time":1786173701218,"data":{"header":{"config":{"provider":"deepseek-official","model":"deepseek-v4-flash"},"system":"{{system}}","tools":"{{tools}}"},"reason":"initial"}}
 {"type":"request/context","seq":8,"time":1786173701219,"data":{"provider":"deepseek-official","model":"deepseek-v4-flash"}}
 {"type":"assistant/chunk","seq":9,"time":0,"data":{"turn":1,"step":1,"chunk":{"type":"block-start","index":0,"blockType":"tool-call"}}}
-{"type":"assistant/chunk","seq":10,"time":0,"data":{"turn":1,"step":1,"chunk":{"type":"tool-call-delta","index":0,"id":"call_question_child","name":"subagent","argumentsDelta":"{\"description\":\"Check deployment question\",\"prompt\":\"Call ask_user_question once to ask whether deployment should use the CUDA fallback. If the tool returns an error, include the unresolved question verbatim in your final result.\"}"}}}
-{"type":"assistant/chunk","seq":11,"time":1786173701233,"data":{"turn":1,"step":1,"chunk":{"type":"block-end","index":0,"block":{"type":"tool-call","id":"call_question_child","name":"subagent","arguments":"{\"description\":\"Check deployment question\",\"prompt\":\"Call ask_user_question once to ask whether deployment should use the CUDA fallback. If the tool returns an error, include the unresolved question verbatim in your final result.\"}"}}}}
+{"type":"assistant/chunk","seq":10,"time":0,"data":{"turn":1,"step":1,"chunk":{"type":"tool-call-delta","index":0,"id":"call_question_child","name":"subagent","argumentsDelta":"{\"description\":\"Check deployment question\",\"prompt\":\"Call ask_user_question once to ask whether deployment should use the CUDA fallback. If the tool returns an error, include the unresolved question verbatim in your final result.\", \"run_in_background\":false}"}}}
+{"type":"assistant/chunk","seq":11,"time":1786173701233,"data":{"turn":1,"step":1,"chunk":{"type":"block-end","index":0,"block":{"type":"tool-call","id":"call_question_child","name":"subagent","arguments":"{\"description\":\"Check deployment question\",\"prompt\":\"Call ask_user_question once to ask whether deployment should use the CUDA fallback. If the tool returns an error, include the unresolved question verbatim in your final result.\", \"run_in_background\":false}"}}}}
 {"type":"assistant/chunk","seq":12,"time":1786173701233,"data":{"turn":1,"step":1,"chunk":{"type":"usage","usage":{"inputTokens":10,"outputTokens":5}}}}
 {"type":"assistant/chunk","seq":13,"time":1786173701233,"data":{"turn":1,"step":1,"chunk":{"type":"finish","reason":{"kind":"tool-calls"}}}}
-{"type":"assistant/message","seq":14,"time":1786173701233,"data":{"turn":1,"step":1,"message":{"role":"assistant","content":[{"type":"tool-call","id":"call_question_child","name":"subagent","arguments":"{\"description\":\"Check deployment question\",\"prompt\":\"Call ask_user_question once to ask whether deployment should use the CUDA fallback. If the tool returns an error, include the unresolved question verbatim in your final result.\"}"}],"source":{"kind":"model","provider":"deepseek-official","model":"deepseek-v4-flash"},"id":"f8909de9-23ae-4dbe-a8c1-eaf1e8f2aba5"},"usage":{"inputTokens":10,"outputTokens":5}},"sourceEventSeqs":[9,10,11,12,13],"surfaceOp":"append"}
-{"type":"tool/call","seq":15,"time":1786173701234,"data":{"turn":1,"step":1,"callId":"call_question_child","name":"subagent","arguments":"{\"description\":\"Check deployment question\",\"prompt\":\"Call ask_user_question once to ask whether deployment should use the CUDA fallback. If the tool returns an error, include the unresolved question verbatim in your final result.\"}"}}
-{"type":"tool/result","seq":16,"time":1786173701316,"data":{"turn":1,"step":1,"message":{"source":{"kind":"tool","callId":"call_question_child"},"content":[{"type":"tool-result","toolCallId":"call_question_child","content":[{"type":"text","text":"UNRESOLVED: Should deployment use the CUDA fallback?"}],"isError":false}],"role":"user","id":"fdc5b075-574b-48c6-bdda-1b6442edfbef"}},"sourceEventSeqs":[15],"surfaceOp":"append"}
+{"type":"assistant/message","seq":14,"time":1786173701233,"data":{"turn":1,"step":1,"message":{"role":"assistant","content":[{"type":"tool-call","id":"call_question_child","name":"subagent","arguments":"{\"description\":\"Check deployment question\",\"prompt\":\"Call ask_user_question once to ask whether deployment should use the CUDA fallback. If the tool returns an error, include the unresolved question verbatim in your final result.\", \"run_in_background\":false}"}],"source":{"kind":"model","provider":"deepseek-official","model":"deepseek-v4-flash"},"id":"f8909de9-23ae-4dbe-a8c1-eaf1e8f2aba5"},"usage":{"inputTokens":10,"outputTokens":5}},"sourceEventSeqs":[9,10,11,12,13],"surfaceOp":"append"}
+{"type":"tool/call","seq":15,"time":1786173701234,"data":{"turn":1,"step":1,"callId":"call_question_child","name":"subagent","arguments":"{\"description\":\"Check deployment question\",\"prompt\":\"Call ask_user_question once to ask whether deployment should use the CUDA fallback. If the tool returns an error, include the unresolved question verbatim in your final result.\", \"run_in_background\":false}"}}
+{"type":"tool/result","seq":16,"time":1786173701316,"data":{"turn":1,"step":1,"message":{"source":{"kind":"tool","callId":"call_question_child"},"content":[{"type":"tool-result","toolCallId":"call_question_child","content":[{"type":"text","text":"UNRESOLVED: Should deployment use the CUDA fallback?"}],"isError":false}],"role":"user","id":"1f6384c7-3d6b-4472-968f-2a4a4e3aba79"}},"sourceEventSeqs":[15],"surfaceOp":"append"}
 {"type":"step/end","seq":17,"time":1786173701317,"data":{"turn":1,"step":1}}
 {"type":"step/start","seq":18,"time":1786173701334,"data":{"turn":1,"step":2}}
 {"type":"assistant/chunk","seq":19,"time":1786173701339,"data":{"turn":1,"step":2,"chunk":{"type":"block-start","index":0,"blockType":"text"}}}

examples/acp-agent/tests/snapshots/subagent-child-question-rejection/tool-schemas.expected.json

@@ -294,7 +294,7 @@
     },
     {
       "name": "subagent",
-      "description": "Delegate a self-contained task to a subagent (a separate agent that works in its own context) and return its final result. Use this to offload focused, independent work — research, a scoped implementation, an analysis — so it does not consume this conversation's context. The subagent runs to completion and you receive only its final answer, not its intermediate steps. Give it a complete, standalone prompt: it does not see this conversation. Set `run_in_background: true` to start a background subagent that keeps its conversation: this call returns only its subagent id, and the subagent works on its own from there. You are told when it finishes, so never poll or wait on it; `send_message` sends it more work.",
+      "description": "Delegate a self-contained task to a subagent (a separate agent that works in its own context) to offload focused, independent work — research, a scoped implementation, an analysis — so it does not consume this conversation's context. The subagent returns its result, not its intermediate steps. Give it a complete, standalone prompt: it does not see this conversation. This tool runs in the background by default, immediately returns a durable subagent id, and keeps the child conversation available for later turns. When that run settles, the runtime sends the parent a notice containing its outcome and any final assistant message; `send_message` starts a later turn in the same child conversation. Set `run_in_background: false` only when your next action depends on receiving the result.",
       "parameters": {
         "type": "object",
         "properties": {
@@ -308,7 +308,7 @@
           },
           "run_in_background": {
             "type": "boolean",
-            "description": "Run as a background subagent that keeps its conversation and return only its subagent id. This call does not wait for it; you are told when it finishes. Send it more work with send_message."
+            "description": "Whether to run in the background and return a durable subagent id immediately. Defaults to true. Set false to wait for the result when your next action depends on it."
           }
         },
         "required": [
@@ -319,7 +319,7 @@
     },
     {
       "name": "subagent_fork",
-      "description": "Delegate a task to a subagent that inherits this conversation: a child agent seeded with all completed turns so far (it does not see the current in-flight turn), returning only its final result. Use this when the subtask builds on this conversation's context — a follow-up analysis, a review, a continuation — without consuming this conversation's context for the work itself. You receive only its final answer, not its intermediate steps.",
+      "description": "Delegate a task to a subagent that inherits this conversation: a child agent seeded with all completed turns so far (it does not see the current in-flight turn). Use this when the subtask builds on this conversation's context — a follow-up analysis, a review, a continuation — without consuming this conversation's context for the work itself. You receive its result, not its intermediate steps. This call waits for the subagent and returns its result.",
       "parameters": {
         "type": "object",
         "properties": {

examples/acp-agent/tests/snapshots/subagent-continuable-inheritance/system-prompt.1.expected.md

@@ -21,4 +21,6 @@ Use the workflow tool ONLY when the user explicitly asks for a workflow or for l
 
 Use the ralph tool ONLY when the direct human explicitly asks for a Ralph loop or fresh-agent iterative execution. Each Ralph round starts a fresh child with no conversation seed and uses the shared workspace as durable memory. Completion and blockers are worker reports, not independent evaluation. Use same-session goal tools for ordinary long-running objectives, and plain subagents or workflows for bounded delegation and fan-out.
 
+Use subagent in the background by default. Start independent delegations together in one assistant message and continue useful work while they run. Set `run_in_background: false` only when your next action depends on that subagent's result. When a background run settles, the runtime sends you a notice containing its outcome and any final assistant message.
+
 Deliver your result with the report tool before you finish: call it once with a self-contained answer. The agent that started you shares your workspace but does not automatically receive your transcript, tool output, or reasoning, so a closing remark such as "done" leaves it nothing it can use. Report earlier as well whenever a partial finding changes what that agent should do next; reporting never ends your turn.

examples/acp-agent/tests/snapshots/subagent-continuable-inheritance/tool-schemas.1.expected.json

@@ -247,7 +247,7 @@
     },
     {
       "name": "subagent",
-      "description": "Delegate a self-contained task to a subagent (a separate agent that works in its own context) and return its final result. Use this to offload focused, independent work — research, a scoped implementation, an analysis — so it does not consume this conversation's context. The subagent runs to completion and you receive only its final answer, not its intermediate steps. Give it a complete, standalone prompt: it does not see this conversation. Set `run_in_background: true` to start a background subagent that keeps its conversation: this call returns only its subagent id, and the subagent works on its own from there. You are told when it finishes, so never poll or wait on it; `send_message` sends it more work.",
+      "description": "Delegate a self-contained task to a subagent (a separate agent that works in its own context) to offload focused, independent work — research, a scoped implementation, an analysis — so it does not consume this conversation's context. The subagent returns its result, not its intermediate steps. Give it a complete, standalone prompt: it does not see this conversation. This tool runs in the background by default, immediately returns a durable subagent id, and keeps the child conversation available for later turns. When that run settles, the runtime sends the parent a notice containing its outcome and any final assistant message; `send_message` starts a later turn in the same child conversation. Set `run_in_background: false` only when your next action depends on receiving the result.",
       "parameters": {
         "type": "object",
         "properties": {
@@ -261,7 +261,7 @@
           },
           "run_in_background": {
             "type": "boolean",
-            "description": "Run as a background subagent that keeps its conversation and return only its subagent id. This call does not wait for it; you are told when it finishes. Send it more work with send_message."
+            "description": "Whether to run in the background and return a durable subagent id immediately. Defaults to true. Set false to wait for the result when your next action depends on it."
           }
         },
         "required": [
@@ -272,7 +272,7 @@
     },
     {
       "name": "subagent_fork",
-      "description": "Delegate a task to a subagent that inherits this conversation: a child agent seeded with all completed turns so far (it does not see the current in-flight turn), returning only its final result. Use this when the subtask builds on this conversation's context — a follow-up analysis, a review, a continuation — without consuming this conversation's context for the work itself. You receive only its final answer, not its intermediate steps.",
+      "description": "Delegate a task to a subagent that inherits this conversation: a child agent seeded with all completed turns so far (it does not see the current in-flight turn). Use this when the subtask builds on this conversation's context — a follow-up analysis, a review, a continuation — without consuming this conversation's context for the work itself. You receive its result, not its intermediate steps. This call waits for the subagent and returns its result.",
       "parameters": {
         "type": "object",
         "properties": {

examples/acp-agent/tests/snapshots/subagent-continuable/system-prompt.1.expected.md

@@ -21,4 +21,6 @@ Use the workflow tool ONLY when the user explicitly asks for a workflow or for l
 
 Use the ralph tool ONLY when the direct human explicitly asks for a Ralph loop or fresh-agent iterative execution. Each Ralph round starts a fresh child with no conversation seed and uses the shared workspace as durable memory. Completion and blockers are worker reports, not independent evaluation. Use same-session goal tools for ordinary long-running objectives, and plain subagents or workflows for bounded delegation and fan-out.
 
+Use subagent in the background by default. Start independent delegations together in one assistant message and continue useful work while they run. Set `run_in_background: false` only when your next action depends on that subagent's result. When a background run settles, the runtime sends you a notice containing its outcome and any final assistant message.
+
 Deliver your result with the report tool before you finish: call it once with a self-contained answer. The agent that started you shares your workspace but does not automatically receive your transcript, tool output, or reasoning, so a closing remark such as "done" leaves it nothing it can use. Report earlier as well whenever a partial finding changes what that agent should do next; reporting never ends your turn.

examples/acp-agent/tests/snapshots/subagent-continuable/tool-schemas.1.expected.json

@@ -247,7 +247,7 @@
     },
     {
       "name": "subagent",
-      "description": "Delegate a self-contained task to a subagent (a separate agent that works in its own context) and return its final result. Use this to offload focused, independent work — research, a scoped implementation, an analysis — so it does not consume this conversation's context. The subagent runs to completion and you receive only its final answer, not its intermediate steps. Give it a complete, standalone prompt: it does not see this conversation. Set `run_in_background: true` to start a background subagent that keeps its conversation: this call returns only its subagent id, and the subagent works on its own from there. You are told when it finishes, so never poll or wait on it; `send_message` sends it more work.",
+      "description": "Delegate a self-contained task to a subagent (a separate agent that works in its own context) to offload focused, independent work — research, a scoped implementation, an analysis — so it does not consume this conversation's context. The subagent returns its result, not its intermediate steps. Give it a complete, standalone prompt: it does not see this conversation. This tool runs in the background by default, immediately returns a durable subagent id, and keeps the child conversation available for later turns. When that run settles, the runtime sends the parent a notice containing its outcome and any final assistant message; `send_message` starts a later turn in the same child conversation. Set `run_in_background: false` only when your next action depends on receiving the result.",
       "parameters": {
         "type": "object",
         "properties": {
@@ -261,7 +261,7 @@
           },
           "run_in_background": {
             "type": "boolean",
-            "description": "Run as a background subagent that keeps its conversation and return only its subagent id. This call does not wait for it; you are told when it finishes. Send it more work with send_message."
+            "description": "Whether to run in the background and return a durable subagent id immediately. Defaults to true. Set false to wait for the result when your next action depends on it."
           }
         },
         "required": [
@@ -272,7 +272,7 @@
     },
     {
       "name": "subagent_fork",
-      "description": "Delegate a task to a subagent that inherits this conversation: a child agent seeded with all completed turns so far (it does not see the current in-flight turn), returning only its final result. Use this when the subtask builds on this conversation's context — a follow-up analysis, a review, a continuation — without consuming this conversation's context for the work itself. You receive only its final answer, not its intermediate steps.",
+      "description": "Delegate a task to a subagent that inherits this conversation: a child agent seeded with all completed turns so far (it does not see the current in-flight turn). Use this when the subtask builds on this conversation's context — a follow-up analysis, a review, a continuation — without consuming this conversation's context for the work itself. You receive its result, not its intermediate steps. This call waits for the subagent and returns its result.",
       "parameters": {
         "type": "object",
         "properties": {

examples/acp-agent/tests/snapshots/subagent-depth-two-rejection/replay.override.json

@@ -3,8 +3,8 @@
     "kind": "chunks",
     "chunks": [
       { "type": "block-start", "index": 0, "blockType": "tool-call" },
-      { "type": "tool-call-delta", "index": 0, "id": "call_root_child", "name": "subagent", "argumentsDelta": "{\"description\":\"Start depth one\",\"prompt\":\"Call subagent once. Ask that child to attempt one further subagent call, then report the result.\"}" },
-      { "type": "block-end", "index": 0, "block": { "type": "tool-call", "id": "call_root_child", "name": "subagent", "arguments": "{\"description\":\"Start depth one\",\"prompt\":\"Call subagent once. Ask that child to attempt one further subagent call, then report the result.\"}" } },
+      { "type": "tool-call-delta", "index": 0, "id": "call_root_child", "name": "subagent", "argumentsDelta": "{\"description\":\"Start depth one\",\"prompt\":\"Call subagent once. Ask that child to attempt one further subagent call, then report the result.\",\"run_in_background\":false}" },
+      { "type": "block-end", "index": 0, "block": { "type": "tool-call", "id": "call_root_child", "name": "subagent", "arguments": "{\"description\":\"Start depth one\",\"prompt\":\"Call subagent once. Ask that child to attempt one further subagent call, then report the result.\",\"run_in_background\":false}" } },
       { "type": "usage", "usage": { "inputTokens": 10, "outputTokens": 5 } },
       { "type": "finish", "reason": { "kind": "tool-calls" } }
     ]

examples/acp-agent/tests/snapshots/subagent-depth-two-rejection/session.1.jsonl

@@ -6,17 +6,17 @@
 {"type":"subagent/descriptor","seq":4,"time":1786357533600,"data":{"version":2,"mode":"one-shot","provider":"spawn","label":"Start depth one"}}
 {"type":"step/start","seq":5,"time":1786357533602,"data":{"turn":1,"step":1}}
 {"type":"user/message","seq":6,"time":1785730456014,"data":{"content":[{"type":"text","text":"Call subagent once. Ask that child to attempt one further subagent call, then report the result."}],"source":{"kind":"user"},"role":"user","id":"a8129357-1bde-4cbd-90b4-6b8ad51d52e1"},"surfaceOp":"append"}
-{"type":"user/message","seq":7,"time":1786357533602,"data":{"content":[{"type":"text","text":"Current runtime context. This snapshot supersedes earlier runtime-context snapshots.\n\nCurrent DSH file policy: danger-full-access. The DSH file sandbox does not restrict file modifications by available operations.\n\nApproval prompts are disabled in this session: actions that require approval are rejected automatically — do not request sandbox escalation (do not set `sandbox_permissions`).\n\nYou are a delegated subagent: your permission scope was fixed when you were started and cannot be widened from inside this session — operations that require approval are rejected automatically. When the task needs access beyond that scope, do not retry the denied operation; state the limitation in your reply so the delegating agent can handle it."}],"source":{"kind":"plugin","plugin":"@deepseek-ai/dsh-system-prompt","form":"snapshot","sections":[{"name":"sandbox:policy","text":"Current DSH file policy: danger-full-access. The DSH file sandbox does not restrict file modifications by available operations."},{"name":"approval:policy","text":"Approval prompts are disabled in this session: actions that require approval are rejected automatically — do not request sandbox escalation (do not set `sandbox_permissions`)."},{"name":"subagent:delegation","text":"You are a delegated subagent: your permission scope was fixed when you were started and cannot be widened from inside this session — operations that require approval are rejected automatically. When the task needs access beyond that scope, do not retry the denied operation; state the limitation in your reply so the delegating agent can handle it."}]},"role":"user","id":"d8d6b5bf-db7b-484f-8095-e35915b94274"},"surfaceOp":"append"}
+{"type":"user/message","seq":7,"time":1786357533602,"data":{"content":[{"type":"text","text":"Current runtime context. This snapshot supersedes earlier runtime-context snapshots.\n\nCurrent DSH file policy: danger-full-access. The DSH file sandbox does not restrict file modifications by available operations.\n\nApproval prompts are disabled in this session: actions that require approval are rejected automatically — do not request sandbox escalation (do not set `sandbox_permissions`).\n\nYou are a delegated subagent: your permission scope was fixed when you were started and cannot be widened from inside this session — operations that require approval are rejected automatically. When the task needs access beyond that scope, do not retry the denied operation; state the limitation in your reply so the delegating agent can handle it."}],"source":{"kind":"plugin","plugin":"@deepseek-ai/dsh-system-prompt","form":"snapshot","sections":[{"name":"sandbox:policy","text":"Current DSH file policy: danger-full-access. The DSH file sandbox does not restrict file modifications by available operations."},{"name":"approval:policy","text":"Approval prompts are disabled in this session: actions that require approval are rejected automatically — do not request sandbox escalation (do not set `sandbox_permissions`)."},{"name":"subagent:delegation","text":"You are a delegated subagent: your permission scope was fixed when you were started and cannot be widened from inside this session — operations that require approval are rejected automatically. When the task needs access beyond that scope, do not retry the denied operation; state the limitation in your reply so the delegating agent can handle it."}]},"role":"user","id":"837ea332-428c-4e4a-b3f1-df24dd20c93a"},"surfaceOp":"append"}
 {"type":"session/title","seq":8,"time":1786357533602,"data":{"title":"Call subagent once. Ask that","messageSeqs":[6],"source":{"kind":"fallback"}}}
 {"type":"request/header","seq":9,"time":1785730456014,"data":{"header":{"config":{"provider":"deepseek-official","model":"deepseek-v4-flash"},"system":"{{system}}","tools":"{{tools}}"},"reason":"initial"}}
 {"type":"request/context","seq":10,"time":1785730456014,"data":{"provider":"deepseek-official","model":"deepseek-v4-flash"}}
 {"type":"assistant/chunk","seq":11,"time":0,"data":{"turn":1,"step":1,"chunk":{"type":"block-start","index":0,"blockType":"tool-call"}}}
-{"type":"assistant/chunk","seq":12,"time":0,"data":{"turn":1,"step":1,"chunk":{"type":"tool-call-delta","index":0,"id":"call_depth_one_child","name":"subagent","argumentsDelta":"{\"description\":\"Start depth two\",\"prompt\":\"Attempt one subagent call beyond the configured cap, then report the rejection.\"}"}}}
-{"type":"assistant/chunk","seq":13,"time":1785498798883,"data":{"turn":1,"step":1,"chunk":{"type":"block-end","index":0,"block":{"type":"tool-call","id":"call_depth_one_child","name":"subagent","arguments":"{\"description\":\"Start depth two\",\"prompt\":\"Attempt one subagent call beyond the configured cap, then report the rejection.\"}"}}}}
+{"type":"assistant/chunk","seq":12,"time":0,"data":{"turn":1,"step":1,"chunk":{"type":"tool-call-delta","index":0,"id":"call_depth_one_child","name":"subagent","argumentsDelta":"{\"description\":\"Start depth two\",\"prompt\":\"Attempt one subagent call beyond the configured cap, then report the rejection.\",\"run_in_background\":false}"}}}
+{"type":"assistant/chunk","seq":13,"time":1785498798883,"data":{"turn":1,"step":1,"chunk":{"type":"block-end","index":0,"block":{"type":"tool-call","id":"call_depth_one_child","name":"subagent","arguments":"{\"description\":\"Start depth two\",\"prompt\":\"Attempt one subagent call beyond the configured cap, then report the rejection.\",\"run_in_background\":false}"}}}}
 {"type":"assistant/chunk","seq":14,"time":1785730456018,"data":{"turn":1,"step":1,"chunk":{"type":"usage","usage":{"inputTokens":10,"outputTokens":5}}}}
 {"type":"assistant/chunk","seq":15,"time":1785730456018,"data":{"turn":1,"step":1,"chunk":{"type":"finish","reason":{"kind":"tool-calls"}}}}
-{"type":"assistant/message","seq":16,"time":1785730456018,"data":{"turn":1,"step":1,"message":{"role":"assistant","content":[{"type":"tool-call","id":"call_depth_one_child","name":"subagent","arguments":"{\"description\":\"Start depth two\",\"prompt\":\"Attempt one subagent call beyond the configured cap, then report the rejection.\"}"}],"source":{"kind":"model","provider":"deepseek-official","model":"deepseek-v4-flash"},"id":"21044d12-2e0e-40e3-b47e-4920e21c3e83"},"usage":{"inputTokens":10,"outputTokens":5}},"sourceEventSeqs":[11,12,13,14,15],"surfaceOp":"append"}
-{"type":"tool/call","seq":17,"time":1785730456019,"data":{"turn":1,"step":1,"callId":"call_depth_one_child","name":"subagent","arguments":"{\"description\":\"Start depth two\",\"prompt\":\"Attempt one subagent call beyond the configured cap, then report the rejection.\"}"}}
+{"type":"assistant/message","seq":16,"time":1785730456018,"data":{"turn":1,"step":1,"message":{"role":"assistant","content":[{"type":"tool-call","id":"call_depth_one_child","name":"subagent","arguments":"{\"description\":\"Start depth two\",\"prompt\":\"Attempt one subagent call beyond the configured cap, then report the rejection.\",\"run_in_background\":false}"}],"source":{"kind":"model","provider":"deepseek-official","model":"deepseek-v4-flash"},"id":"21044d12-2e0e-40e3-b47e-4920e21c3e83"},"usage":{"inputTokens":10,"outputTokens":5}},"sourceEventSeqs":[11,12,13,14,15],"surfaceOp":"append"}
+{"type":"tool/call","seq":17,"time":1785730456019,"data":{"turn":1,"step":1,"callId":"call_depth_one_child","name":"subagent","arguments":"{\"description\":\"Start depth two\",\"prompt\":\"Attempt one subagent call beyond the configured cap, then report the rejection.\",\"run_in_background\":false}"}}
 {"type":"tool/result","seq":18,"time":1785730456072,"data":{"turn":1,"step":1,"message":{"source":{"kind":"tool","callId":"call_depth_one_child"},"content":[{"type":"tool-result","toolCallId":"call_depth_one_child","content":[{"type":"text","text":"DEPTH_REJECTED"}],"isError":false}],"role":"user","id":"aa5451a8-812b-4a51-a52c-dbc5c84f16d0"}},"sourceEventSeqs":[17],"surfaceOp":"append"}
 {"type":"step/end","seq":19,"time":1785730456072,"data":{"turn":1,"step":1}}
 {"type":"step/start","seq":20,"time":1785730456082,"data":{"turn":1,"step":2}}

examples/acp-agent/tests/snapshots/subagent-depth-two-rejection/session.2.jsonl

@@ -6,17 +6,17 @@
 {"type":"subagent/descriptor","seq":4,"time":1786357533628,"data":{"version":2,"mode":"one-shot","provider":"spawn","label":"Start depth two"}}
 {"type":"step/start","seq":5,"time":1786357533630,"data":{"turn":1,"step":1}}
 {"type":"user/message","seq":6,"time":1785730456041,"data":{"content":[{"type":"text","text":"Attempt one subagent call beyond the configured cap, then report the rejection."}],"source":{"kind":"user"},"role":"user","id":"d4dc5a16-e542-4dd9-8e82-e6b7829cfc4b"},"surfaceOp":"append"}
-{"type":"user/message","seq":7,"time":1786357533630,"data":{"content":[{"type":"text","text":"Current runtime context. This snapshot supersedes earlier runtime-context snapshots.\n\nCurrent DSH file policy: danger-full-access. The DSH file sandbox does not restrict file modifications by available operations.\n\nApproval prompts are disabled in this session: actions that require approval are rejected automatically — do not request sandbox escalation (do not set `sandbox_permissions`).\n\nYou are a delegated subagent: your permission scope was fixed when you were started and cannot be widened from inside this session — operations that require approval are rejected automatically. When the task needs access beyond that scope, do not retry the denied operation; state the limitation in your reply so the delegating agent can handle it."}],"source":{"kind":"plugin","plugin":"@deepseek-ai/dsh-system-prompt","form":"snapshot","sections":[{"name":"sandbox:policy","text":"Current DSH file policy: danger-full-access. The DSH file sandbox does not restrict file modifications by available operations."},{"name":"approval:policy","text":"Approval prompts are disabled in this session: actions that require approval are rejected automatically — do not request sandbox escalation (do not set `sandbox_permissions`)."},{"name":"subagent:delegation","text":"You are a delegated subagent: your permission scope was fixed when you were started and cannot be widened from inside this session — operations that require approval are rejected automatically. When the task needs access beyond that scope, do not retry the denied operation; state the limitation in your reply so the delegating agent can handle it."}]},"role":"user","id":"e9907a11-3d7c-4796-a459-16afd4afde32"},"surfaceOp":"append"}
+{"type":"user/message","seq":7,"time":1786357533630,"data":{"content":[{"type":"text","text":"Current runtime context. This snapshot supersedes earlier runtime-context snapshots.\n\nCurrent DSH file policy: danger-full-access. The DSH file sandbox does not restrict file modifications by available operations.\n\nApproval prompts are disabled in this session: actions that require approval are rejected automatically — do not request sandbox escalation (do not set `sandbox_permissions`).\n\nYou are a delegated subagent: your permission scope was fixed when you were started and cannot be widened from inside this session — operations that require approval are rejected automatically. When the task needs access beyond that scope, do not retry the denied operation; state the limitation in your reply so the delegating agent can handle it."}],"source":{"kind":"plugin","plugin":"@deepseek-ai/dsh-system-prompt","form":"snapshot","sections":[{"name":"sandbox:policy","text":"Current DSH file policy: danger-full-access. The DSH file sandbox does not restrict file modifications by available operations."},{"name":"approval:policy","text":"Approval prompts are disabled in this session: actions that require approval are rejected automatically — do not request sandbox escalation (do not set `sandbox_permissions`)."},{"name":"subagent:delegation","text":"You are a delegated subagent: your permission scope was fixed when you were started and cannot be widened from inside this session — operations that require approval are rejected automatically. When the task needs access beyond that scope, do not retry the denied operation; state the limitation in your reply so the delegating agent can handle it."}]},"role":"user","id":"a62cf283-f87f-4f6f-be16-a00978557f99"},"surfaceOp":"append"}
 {"type":"session/title","seq":8,"time":1786357533630,"data":{"title":"Attempt one subagent call beyond","messageSeqs":[6],"source":{"kind":"fallback"}}}
 {"type":"request/header","seq":9,"time":1785730456041,"data":{"header":{"config":{"provider":"deepseek-official","model":"deepseek-v4-flash"},"system":"{{system}}","tools":"{{tools}}"},"reason":"initial"}}
 {"type":"request/context","seq":10,"time":1785730456042,"data":{"provider":"deepseek-official","model":"deepseek-v4-flash"}}
 {"type":"assistant/chunk","seq":11,"time":0,"data":{"turn":1,"step":1,"chunk":{"type":"block-start","index":0,"blockType":"tool-call"}}}
-{"type":"assistant/chunk","seq":12,"time":0,"data":{"turn":1,"step":1,"chunk":{"type":"tool-call-delta","index":0,"id":"call_depth_three_rejected","name":"subagent","argumentsDelta":"{\"description\":\"Exceed depth cap\",\"prompt\":\"This child must never start.\"}"}}}
-{"type":"assistant/chunk","seq":13,"time":1785498798916,"data":{"turn":1,"step":1,"chunk":{"type":"block-end","index":0,"block":{"type":"tool-call","id":"call_depth_three_rejected","name":"subagent","arguments":"{\"description\":\"Exceed depth cap\",\"prompt\":\"This child must never start.\"}"}}}}
+{"type":"assistant/chunk","seq":12,"time":0,"data":{"turn":1,"step":1,"chunk":{"type":"tool-call-delta","index":0,"id":"call_depth_three_rejected","name":"subagent","argumentsDelta":"{\"description\":\"Exceed depth cap\",\"prompt\":\"This child must never start.\",\"run_in_background\":false}"}}}
+{"type":"assistant/chunk","seq":13,"time":1785498798916,"data":{"turn":1,"step":1,"chunk":{"type":"block-end","index":0,"block":{"type":"tool-call","id":"call_depth_three_rejected","name":"subagent","arguments":"{\"description\":\"Exceed depth cap\",\"prompt\":\"This child must never start.\",\"run_in_background\":false}"}}}}
 {"type":"assistant/chunk","seq":14,"time":1785730456047,"data":{"turn":1,"step":1,"chunk":{"type":"usage","usage":{"inputTokens":10,"outputTokens":5}}}}
 {"type":"assistant/chunk","seq":15,"time":1785730456047,"data":{"turn":1,"step":1,"chunk":{"type":"finish","reason":{"kind":"tool-calls"}}}}
-{"type":"assistant/message","seq":16,"time":1785730456047,"data":{"turn":1,"step":1,"message":{"role":"assistant","content":[{"type":"tool-call","id":"call_depth_three_rejected","name":"subagent","arguments":"{\"description\":\"Exceed depth cap\",\"prompt\":\"This child must never start.\"}"}],"source":{"kind":"model","provider":"deepseek-official","model":"deepseek-v4-flash"},"id":"467433db-5dbf-42ee-94c0-25c011ce711b"},"usage":{"inputTokens":10,"outputTokens":5}},"sourceEventSeqs":[11,12,13,14,15],"surfaceOp":"append"}
-{"type":"tool/call","seq":17,"time":1785730456048,"data":{"turn":1,"step":1,"callId":"call_depth_three_rejected","name":"subagent","arguments":"{\"description\":\"Exceed depth cap\",\"prompt\":\"This child must never start.\"}"}}
+{"type":"assistant/message","seq":16,"time":1785730456047,"data":{"turn":1,"step":1,"message":{"role":"assistant","content":[{"type":"tool-call","id":"call_depth_three_rejected","name":"subagent","arguments":"{\"description\":\"Exceed depth cap\",\"prompt\":\"This child must never start.\",\"run_in_background\":false}"}],"source":{"kind":"model","provider":"deepseek-official","model":"deepseek-v4-flash"},"id":"467433db-5dbf-42ee-94c0-25c011ce711b"},"usage":{"inputTokens":10,"outputTokens":5}},"sourceEventSeqs":[11,12,13,14,15],"surfaceOp":"append"}
+{"type":"tool/call","seq":17,"time":1785730456048,"data":{"turn":1,"step":1,"callId":"call_depth_three_rejected","name":"subagent","arguments":"{\"description\":\"Exceed depth cap\",\"prompt\":\"This child must never start.\",\"run_in_background\":false}"}}
 {"type":"tool/result","seq":18,"time":1785730456056,"data":{"turn":1,"step":1,"message":{"source":{"kind":"tool","callId":"call_depth_three_rejected"},"content":[{"type":"tool-result","toolCallId":"call_depth_three_rejected","content":[{"type":"text","text":"Error: subagent depth 3 exceeds maxDepth 2"}],"isError":true}],"role":"user","id":"9a3d59f3-542a-4400-a62c-be28dcea3bd1"}},"sourceEventSeqs":[17],"surfaceOp":"append"}
 {"type":"step/end","seq":19,"time":1785730456056,"data":{"turn":1,"step":1}}
 {"type":"step/start","seq":20,"time":1785730456066,"data":{"turn":1,"step":2}}

examples/acp-agent/tests/snapshots/subagent-depth-two-rejection/session.jsonl

@@ -9,12 +9,12 @@
 {"type":"request/header","seq":7,"time":1785498798841,"data":{"header":{"config":{"provider":"deepseek-official","model":"deepseek-v4-flash"},"system":"{{system}}","tools":"{{tools}}"},"reason":"initial"}}
 {"type":"request/context","seq":8,"time":1785730455981,"data":{"provider":"deepseek-official","model":"deepseek-v4-flash"}}
 {"type":"assistant/chunk","seq":9,"time":1784540790309,"data":{"turn":1,"step":1,"chunk":{"type":"block-start","index":0,"blockType":"tool-call"}}}
-{"type":"assistant/chunk","seq":10,"time":1784540790309,"data":{"turn":1,"step":1,"chunk":{"type":"tool-call-delta","index":0,"id":"call_root_child","name":"subagent","argumentsDelta":"{\"description\":\"Start depth one\",\"prompt\":\"Call subagent once. Ask that child to attempt one further subagent call, then report the result.\"}"}}}
-{"type":"assistant/chunk","seq":11,"time":1784540790309,"data":{"turn":1,"step":1,"chunk":{"type":"block-end","index":0,"block":{"type":"tool-call","id":"call_root_child","name":"subagent","arguments":"{\"description\":\"Start depth one\",\"prompt\":\"Call subagent once. Ask that child to attempt one further subagent call, then report the result.\"}"}}}}
+{"type":"assistant/chunk","seq":10,"time":1784540790309,"data":{"turn":1,"step":1,"chunk":{"type":"tool-call-delta","index":0,"id":"call_root_child","name":"subagent","argumentsDelta":"{\"description\":\"Start depth one\",\"prompt\":\"Call subagent once. Ask that child to attempt one further subagent call, then report the result.\",\"run_in_background\":false}"}}}
+{"type":"assistant/chunk","seq":11,"time":1784540790309,"data":{"turn":1,"step":1,"chunk":{"type":"block-end","index":0,"block":{"type":"tool-call","id":"call_root_child","name":"subagent","arguments":"{\"description\":\"Start depth one\",\"prompt\":\"Call subagent once. Ask that child to attempt one further subagent call, then report the result.\",\"run_in_background\":false}"}}}}
 {"type":"assistant/chunk","seq":12,"time":1785498798850,"data":{"turn":1,"step":1,"chunk":{"type":"usage","usage":{"inputTokens":10,"outputTokens":5}}}}
 {"type":"assistant/chunk","seq":13,"time":1785730455990,"data":{"turn":1,"step":1,"chunk":{"type":"finish","reason":{"kind":"tool-calls"}}}}
-{"type":"assistant/message","seq":14,"time":1785730455990,"data":{"turn":1,"step":1,"message":{"role":"assistant","content":[{"type":"tool-call","id":"call_root_child","name":"subagent","arguments":"{\"description\":\"Start depth one\",\"prompt\":\"Call subagent once. Ask that child to attempt one further subagent call, then report the result.\"}"}],"source":{"kind":"model","provider":"deepseek-official","model":"deepseek-v4-flash"},"id":"f0284ec5-b83d-4eca-8f10-d3e4e09d0a39"},"usage":{"inputTokens":10,"outputTokens":5}},"sourceEventSeqs":[9,10,11,12,13],"surfaceOp":"append"}
-{"type":"tool/call","seq":15,"time":1785730455990,"data":{"turn":1,"step":1,"callId":"call_root_child","name":"subagent","arguments":"{\"description\":\"Start depth one\",\"prompt\":\"Call subagent once. Ask that child to attempt one further subagent call, then report the result.\"}"}}
+{"type":"assistant/message","seq":14,"time":1785730455990,"data":{"turn":1,"step":1,"message":{"role":"assistant","content":[{"type":"tool-call","id":"call_root_child","name":"subagent","arguments":"{\"description\":\"Start depth one\",\"prompt\":\"Call subagent once. Ask that child to attempt one further subagent call, then report the result.\",\"run_in_background\":false}"}],"source":{"kind":"model","provider":"deepseek-official","model":"deepseek-v4-flash"},"id":"4683ea2f-13fc-42d8-9794-cf5f714fb001"},"usage":{"inputTokens":10,"outputTokens":5}},"sourceEventSeqs":[9,10,11,12,13],"surfaceOp":"append"}
+{"type":"tool/call","seq":15,"time":1785730455990,"data":{"turn":1,"step":1,"callId":"call_root_child","name":"subagent","arguments":"{\"description\":\"Start depth one\",\"prompt\":\"Call subagent once. Ask that child to attempt one further subagent call, then report the result.\",\"run_in_background\":false}"}}
 {"type":"tool/result","seq":16,"time":1785730456087,"data":{"turn":1,"step":1,"message":{"source":{"kind":"tool","callId":"call_root_child"},"content":[{"type":"tool-result","toolCallId":"call_root_child","content":[{"type":"text","text":"DEPTH_ONE_DONE"}],"isError":false}],"role":"user","id":"6e5d6cdb-d9da-47a0-826a-50f7022b544d"}},"sourceEventSeqs":[15],"surfaceOp":"append"}
 {"type":"step/end","seq":17,"time":1785730456087,"data":{"turn":1,"step":1}}
 {"type":"step/start","seq":18,"time":1785730456097,"data":{"turn":1,"step":2}}

examples/acp-agent/tests/snapshots/subagent-list-agents/system-prompt.1.expected.md

@@ -21,4 +21,6 @@ Use the workflow tool ONLY when the user explicitly asks for a workflow or for l
 
 Use the ralph tool ONLY when the direct human explicitly asks for a Ralph loop or fresh-agent iterative execution. Each Ralph round starts a fresh child with no conversation seed and uses the shared workspace as durable memory. Completion and blockers are worker reports, not independent evaluation. Use same-session goal tools for ordinary long-running objectives, and plain subagents or workflows for bounded delegation and fan-out.
 
+Use subagent in the background by default. Start independent delegations together in one assistant message and continue useful work while they run. Set `run_in_background: false` only when your next action depends on that subagent's result. When a background run settles, the runtime sends you a notice containing its outcome and any final assistant message.
+
 Deliver your result with the report tool before you finish: call it once with a self-contained answer. The agent that started you shares your workspace but does not automatically receive your transcript, tool output, or reasoning, so a closing remark such as "done" leaves it nothing it can use. Report earlier as well whenever a partial finding changes what that agent should do next; reporting never ends your turn.

examples/acp-agent/tests/snapshots/subagent-list-agents/tool-schemas.1.expected.json

@@ -247,7 +247,7 @@
     },
     {
       "name": "subagent",
-      "description": "Delegate a self-contained task to a subagent (a separate agent that works in its own context) and return its final result. Use this to offload focused, independent work — research, a scoped implementation, an analysis — so it does not consume this conversation's context. The subagent runs to completion and you receive only its final answer, not its intermediate steps. Give it a complete, standalone prompt: it does not see this conversation. Set `run_in_background: true` to start a background subagent that keeps its conversation: this call returns only its subagent id, and the subagent works on its own from there. You are told when it finishes, so never poll or wait on it; `send_message` sends it more work.",
+      "description": "Delegate a self-contained task to a subagent (a separate agent that works in its own context) to offload focused, independent work — research, a scoped implementation, an analysis — so it does not consume this conversation's context. The subagent returns its result, not its intermediate steps. Give it a complete, standalone prompt: it does not see this conversation. This tool runs in the background by default, immediately returns a durable subagent id, and keeps the child conversation available for later turns. When that run settles, the runtime sends the parent a notice containing its outcome and any final assistant message; `send_message` starts a later turn in the same child conversation. Set `run_in_background: false` only when your next action depends on receiving the result.",
       "parameters": {
         "type": "object",
         "properties": {
@@ -261,7 +261,7 @@
           },
           "run_in_background": {
             "type": "boolean",
-            "description": "Run as a background subagent that keeps its conversation and return only its subagent id. This call does not wait for it; you are told when it finishes. Send it more work with send_message."
+            "description": "Whether to run in the background and return a durable subagent id immediately. Defaults to true. Set false to wait for the result when your next action depends on it."
           }
         },
         "required": [
@@ -272,7 +272,7 @@
     },
     {
       "name": "subagent_fork",
-      "description": "Delegate a task to a subagent that inherits this conversation: a child agent seeded with all completed turns so far (it does not see the current in-flight turn), returning only its final result. Use this when the subtask builds on this conversation's context — a follow-up analysis, a review, a continuation — without consuming this conversation's context for the work itself. You receive only its final answer, not its intermediate steps.",
+      "description": "Delegate a task to a subagent that inherits this conversation: a child agent seeded with all completed turns so far (it does not see the current in-flight turn). Use this when the subtask builds on this conversation's context — a follow-up analysis, a review, a continuation — without consuming this conversation's context for the work itself. You receive its result, not its intermediate steps. This call waits for the subagent and returns its result.",
       "parameters": {
         "type": "object",
         "properties": {

examples/acp-agent/tests/snapshots/subagent-max-tokens-partial/session.jsonl

@@ -9,12 +9,12 @@
 {"type":"request/header","seq":7,"time":1786348800115,"data":{"header":{"config":{"provider":"deepseek-official","model":"deepseek-v4-flash"},"system":"{{system}}","tools":"{{tools}}"},"reason":"initial"}}
 {"type":"request/context","seq":8,"time":1786348800115,"data":{"provider":"deepseek-official","model":"deepseek-v4-flash"}}
 {"type":"assistant/chunk","seq":9,"time":1786348800120,"data":{"turn":1,"step":1,"chunk":{"type":"block-start","index":0,"blockType":"tool-call"}}}
-{"type":"assistant/chunk","seq":10,"time":1786348800120,"data":{"turn":1,"step":1,"chunk":{"type":"block-end","index":0,"block":{"type":"tool-call","id":"call_parent_1","name":"subagent","arguments":"{\"description\": \"Truncated child\", \"prompt\": \"Write the words 'partial one', call todo_write once, then keep going until you are cut off.\"}"}}}}
+{"type":"assistant/chunk","seq":10,"time":1786348800120,"data":{"turn":1,"step":1,"chunk":{"type":"block-end","index":0,"block":{"type":"tool-call","id":"call_parent_1","name":"subagent","arguments":"{\"description\": \"Truncated child\", \"prompt\": \"Write the words 'partial one', call todo_write once, then keep going until you are cut off.\", \"run_in_background\":false}"}}}}
 {"type":"assistant/chunk","seq":11,"time":1786348800120,"data":{"turn":1,"step":1,"chunk":{"type":"usage","usage":{"inputTokens":10,"outputTokens":5}}}}
 {"type":"assistant/chunk","seq":12,"time":1786348800120,"data":{"turn":1,"step":1,"chunk":{"type":"finish","reason":{"kind":"tool-calls"}}}}
-{"type":"assistant/message","seq":13,"time":1786348800120,"data":{"turn":1,"step":1,"message":{"role":"assistant","content":[{"type":"tool-call","id":"call_parent_1","name":"subagent","arguments":"{\"description\": \"Truncated child\", \"prompt\": \"Write the words 'partial one', call todo_write once, then keep going until you are cut off.\"}"}],"source":{"kind":"model","provider":"deepseek-official","model":"deepseek-v4-flash"},"id":"f4269cd2-9132-4b68-8f9b-ff3a40321bc9"},"usage":{"inputTokens":10,"outputTokens":5}},"sourceEventSeqs":[9,10,11,12],"surfaceOp":"append"}
-{"type":"tool/call","seq":14,"time":1786348800121,"data":{"turn":1,"step":1,"callId":"call_parent_1","name":"subagent","arguments":"{\"description\": \"Truncated child\", \"prompt\": \"Write the words 'partial one', call todo_write once, then keep going until you are cut off.\"}"}}
-{"type":"tool/result","seq":15,"time":1786348800163,"data":{"turn":1,"step":1,"message":{"source":{"kind":"tool","callId":"call_parent_1"},"content":[{"type":"tool-result","toolCallId":"call_parent_1","content":[{"type":"text","text":"Error: subagent run hit its token limit before finishing\nPartial output before the run ended:\npartial one"}],"isError":true}],"role":"user","id":"5dd34050-a533-4f1b-99ee-5fc62c6a4502"}},"sourceEventSeqs":[14],"surfaceOp":"append"}
+{"type":"assistant/message","seq":13,"time":1786348800120,"data":{"turn":1,"step":1,"message":{"role":"assistant","content":[{"type":"tool-call","id":"call_parent_1","name":"subagent","arguments":"{\"description\": \"Truncated child\", \"prompt\": \"Write the words 'partial one', call todo_write once, then keep going until you are cut off.\", \"run_in_background\":false}"}],"source":{"kind":"model","provider":"deepseek-official","model":"deepseek-v4-flash"},"id":"f4269cd2-9132-4b68-8f9b-ff3a40321bc9"},"usage":{"inputTokens":10,"outputTokens":5}},"sourceEventSeqs":[9,10,11,12],"surfaceOp":"append"}
+{"type":"tool/call","seq":14,"time":1786348800121,"data":{"turn":1,"step":1,"callId":"call_parent_1","name":"subagent","arguments":"{\"description\": \"Truncated child\", \"prompt\": \"Write the words 'partial one', call todo_write once, then keep going until you are cut off.\", \"run_in_background\":false}"}}
+{"type":"tool/result","seq":15,"time":1786348800163,"data":{"turn":1,"step":1,"message":{"source":{"kind":"tool","callId":"call_parent_1"},"content":[{"type":"tool-result","toolCallId":"call_parent_1","content":[{"type":"text","text":"Error: subagent run hit its token limit before finishing\nPartial output before the run ended:\npartial one"}],"isError":true}],"role":"user","id":"84e0d207-3fad-40bd-b68d-2dfefb0e181c"}},"sourceEventSeqs":[14],"surfaceOp":"append"}
 {"type":"step/end","seq":16,"time":1786348800163,"data":{"turn":1,"step":1}}
 {"type":"step/start","seq":17,"time":1786348800169,"data":{"turn":1,"step":2}}
 {"type":"assistant/chunk","seq":18,"time":1786348800173,"data":{"turn":1,"step":2,"chunk":{"type":"block-start","index":0,"blockType":"text"}}}

examples/acp-agent/tests/snapshots/subagent-mixed/session.1.jsonl

@@ -1,23 +1,23 @@
 {"type":"session","version":0,"id":"e4aafa18-b9e3-48d0-8aae-6c9b25dcae80","createdAt":1783352145223,"cwd":"{{cwd}}","parentSession":"959ffdf5-03e2-465e-9482-009b704632dc","origin":"subagent","delegationDepth":1}
-{"type":"approval/policy","seq":0,"time":1786357524735,"data":{"policy":"never","source":"delegation"}}
-{"type":"agent/inbox/spliced","seq":1,"time":1786357524735,"data":{"target":"next-turn","start":0,"inserted":[{"content":[{"type":"text","text":"Reply with exactly the word ALPHA and nothing else."}],"source":{"kind":"user"},"role":"user","id":"73ce401a-faaf-408a-879e-7485380d537d"}]}}
-{"type":"turn/start","seq":2,"time":1786357524735,"data":{"turn":1}}
+{"type":"approval/policy","seq":0,"time":1786443013973,"data":{"policy":"never","source":"delegation"}}
+{"type":"agent/inbox/spliced","seq":1,"time":1786443013973,"data":{"target":"next-turn","start":0,"inserted":[{"content":[{"type":"text","text":"Reply with exactly the word ALPHA and nothing else."}],"source":{"kind":"user"},"role":"user","id":"73ce401a-faaf-408a-879e-7485380d537d"}]}}
+{"type":"turn/start","seq":2,"time":1786443013974,"data":{"turn":1}}
 {"type":"agent/inbox/spliced","seq":3,"time":1786357524735,"data":{"target":"next-turn","start":0,"removedCount":1,"inserted":[]}}
-{"type":"subagent/descriptor","seq":4,"time":1786357524752,"data":{"version":2,"mode":"one-shot","provider":"spawn","label":"Reply ALPHA only"}}
-{"type":"step/start","seq":5,"time":1786357524755,"data":{"turn":1,"step":1}}
-{"type":"user/message","seq":6,"time":1785730450187,"data":{"content":[{"type":"text","text":"Reply with exactly the word ALPHA and nothing else."}],"source":{"kind":"user"},"role":"user","id":"73ce401a-faaf-408a-879e-7485380d537d"},"surfaceOp":"append"}
-{"type":"user/message","seq":7,"time":1786357524755,"data":{"content":[{"type":"text","text":"Current runtime context. This snapshot supersedes earlier runtime-context snapshots.\n\nCurrent DSH file policy: danger-full-access. The DSH file sandbox does not restrict file modifications by available operations.\n\nApproval prompts are disabled in this session: actions that require approval are rejected automatically — do not request sandbox escalation (do not set `sandbox_permissions`).\n\nYou are a delegated subagent: your permission scope was fixed when you were started and cannot be widened from inside this session — operations that require approval are rejected automatically. When the task needs access beyond that scope, do not retry the denied operation; state the limitation in your reply so the delegating agent can handle it."}],"source":{"kind":"plugin","plugin":"@deepseek-ai/dsh-system-prompt","form":"snapshot","sections":[{"name":"sandbox:policy","text":"Current DSH file policy: danger-full-access. The DSH file sandbox does not restrict file modifications by available operations."},{"name":"approval:policy","text":"Approval prompts are disabled in this session: actions that require approval are rejected automatically — do not request sandbox escalation (do not set `sandbox_permissions`)."},{"name":"subagent:delegation","text":"You are a delegated subagent: your permission scope was fixed when you were started and cannot be widened from inside this session — operations that require approval are rejected automatically. When the task needs access beyond that scope, do not retry the denied operation; state the limitation in your reply so the delegating agent can handle it."}]},"role":"user","id":"cb073ca7-b412-4509-99ef-4e1351e7e74d"},"surfaceOp":"append"}
+{"type":"subagent/descriptor","seq":4,"time":1786443013990,"data":{"version":2,"mode":"one-shot","provider":"spawn","label":"Reply ALPHA only"}}
+{"type":"step/start","seq":5,"time":1786443013993,"data":{"turn":1,"step":1}}
+{"type":"user/message","seq":6,"time":1786443013993,"data":{"content":[{"type":"text","text":"Reply with exactly the word ALPHA and nothing else."}],"source":{"kind":"user"},"role":"user","id":"73ce401a-faaf-408a-879e-7485380d537d"},"surfaceOp":"append"}
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examples/acp-agent/tests/snapshots/subagent-mixed/session.2.jsonl

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examples/acp-agent/tests/snapshots/subagent-mixed/session.jsonl

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-{"type":"assistant/message","seq":291,"time":1785730450270,"data":{"turn":2,"step":3,"message":{"role":"assistant","content":[{"type":"reasoning","text":"Both subagents returned:\n1. First (fresh child): \"ALPHA\"\n2. Second (forked child): \"SAFFRON\" - correctly inherited the conversation context where I was asked to remember the codeword \"SAFFRON\".\n\nNow I reply with \"PARENT_DONE\" as instructed."},{"type":"text","text":"PARENT_DONE"}],"source":{"kind":"model","provider":"deepseek-official","model":"deepseek-v4-flash"},"id":"256c985a-449a-4176-9233-7d29cf47ba5e"},"usage":{"inputTokens":69,"outputTokens":69,"cacheReadTokens":3200,"reasoningTokens":64}},"sourceEventSeqs":[217,218,219,220,221,222,223,224,225,226,227,228,229,230,231,232,233,234,235,236,237,238,239,240,241,242,243,244,245,246,247,248,249,250,251,252,253,254,255,256,257,258,259,260,261,262,263,264,265,266,267,268,269,270,271,272,273,274,275,276,277,278,279,280,281,282,283,284,285,286,287,288,289,290],"surfaceOp":"append"}
-{"type":"step/end","seq":292,"time":1785730450270,"data":{"turn":2,"step":3}}
-{"type":"turn/end","seq":293,"time":1785730450270,"data":{"turn":2,"reason":{"kind":"completed"}}}
+{"type":"assistant/message","seq":291,"time":1786443014062,"data":{"turn":2,"step":3,"message":{"role":"assistant","content":[{"type":"reasoning","text":"Both subagents returned:\n1. First (fresh child): \"ALPHA\"\n2. Second (forked child): \"SAFFRON\" - correctly inherited the conversation context where I was asked to remember the codeword \"SAFFRON\".\n\nNow I reply with \"PARENT_DONE\" as instructed."},{"type":"text","text":"PARENT_DONE"}],"source":{"kind":"model","provider":"deepseek-official","model":"deepseek-v4-flash"},"id":"256c985a-449a-4176-9233-7d29cf47ba5e"},"usage":{"inputTokens":69,"outputTokens":69,"cacheReadTokens":3200,"reasoningTokens":64}},"sourceEventSeqs":[217,218,219,220,221,222,223,224,225,226,227,228,229,230,231,232,233,234,235,236,237,238,239,240,241,242,243,244,245,246,247,248,249,250,251,252,253,254,255,256,257,258,259,260,261,262,263,264,265,266,267,268,269,270,271,272,273,274,275,276,277,278,279,280,281,282,283,284,285,286,287,288,289,290],"surfaceOp":"append"}
+{"type":"step/end","seq":292,"time":1786443014063,"data":{"turn":2,"step":3}}
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examples/acp-agent/tests/snapshots/subagent-multi/session.1.jsonl

@@ -6,7 +6,7 @@
 {"type":"subagent/descriptor","seq":4,"time":1786357521754,"data":{"version":2,"mode":"one-shot","provider":"spawn","label":"Return ALPHA only"}}
 {"type":"step/start","seq":5,"time":1786357521756,"data":{"turn":1,"step":1}}
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-{"type":"user/message","seq":7,"time":1786357521756,"data":{"content":[{"type":"text","text":"Current runtime context. This snapshot supersedes earlier runtime-context snapshots.\n\nCurrent DSH file policy: danger-full-access. The DSH file sandbox does not restrict file modifications by available operations.\n\nApproval prompts are disabled in this session: actions that require approval are rejected automatically — do not request sandbox escalation (do not set `sandbox_permissions`).\n\nYou are a delegated subagent: your permission scope was fixed when you were started and cannot be widened from inside this session — operations that require approval are rejected automatically. When the task needs access beyond that scope, do not retry the denied operation; state the limitation in your reply so the delegating agent can handle it."}],"source":{"kind":"plugin","plugin":"@deepseek-ai/dsh-system-prompt","form":"snapshot","sections":[{"name":"sandbox:policy","text":"Current DSH file policy: danger-full-access. The DSH file sandbox does not restrict file modifications by available operations."},{"name":"approval:policy","text":"Approval prompts are disabled in this session: actions that require approval are rejected automatically — do not request sandbox escalation (do not set `sandbox_permissions`)."},{"name":"subagent:delegation","text":"You are a delegated subagent: your permission scope was fixed when you were started and cannot be widened from inside this session — operations that require approval are rejected automatically. When the task needs access beyond that scope, do not retry the denied operation; state the limitation in your reply so the delegating agent can handle it."}]},"role":"user","id":"6f423049-484c-48d6-9cdd-db504d79f892"},"surfaceOp":"append"}
+{"type":"user/message","seq":7,"time":1786357521756,"data":{"content":[{"type":"text","text":"Current runtime context. This snapshot supersedes earlier runtime-context snapshots.\n\nCurrent DSH file policy: danger-full-access. The DSH file sandbox does not restrict file modifications by available operations.\n\nApproval prompts are disabled in this session: actions that require approval are rejected automatically — do not request sandbox escalation (do not set `sandbox_permissions`).\n\nYou are a delegated subagent: your permission scope was fixed when you were started and cannot be widened from inside this session — operations that require approval are rejected automatically. When the task needs access beyond that scope, do not retry the denied operation; state the limitation in your reply so the delegating agent can handle it."}],"source":{"kind":"plugin","plugin":"@deepseek-ai/dsh-system-prompt","form":"snapshot","sections":[{"name":"sandbox:policy","text":"Current DSH file policy: danger-full-access. The DSH file sandbox does not restrict file modifications by available operations."},{"name":"approval:policy","text":"Approval prompts are disabled in this session: actions that require approval are rejected automatically — do not request sandbox escalation (do not set `sandbox_permissions`)."},{"name":"subagent:delegation","text":"You are a delegated subagent: your permission scope was fixed when you were started and cannot be widened from inside this session — operations that require approval are rejected automatically. When the task needs access beyond that scope, do not retry the denied operation; state the limitation in your reply so the delegating agent can handle it."}]},"role":"user","id":"59d87d55-736f-4836-be4e-084a9f5cc7b1"},"surfaceOp":"append"}
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examples/acp-agent/tests/snapshots/subagent-multi/session.2.jsonl

@@ -6,7 +6,7 @@
 {"type":"subagent/descriptor","seq":4,"time":1786357521799,"data":{"version":2,"mode":"one-shot","provider":"spawn","label":"Return BETA only"}}
 {"type":"step/start","seq":5,"time":1786357521801,"data":{"turn":1,"step":1}}
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-{"type":"user/message","seq":7,"time":1786357521802,"data":{"content":[{"type":"text","text":"Current runtime context. This snapshot supersedes earlier runtime-context snapshots.\n\nCurrent DSH file policy: danger-full-access. The DSH file sandbox does not restrict file modifications by available operations.\n\nApproval prompts are disabled in this session: actions that require approval are rejected automatically — do not request sandbox escalation (do not set `sandbox_permissions`).\n\nYou are a delegated subagent: your permission scope was fixed when you were started and cannot be widened from inside this session — operations that require approval are rejected automatically. When the task needs access beyond that scope, do not retry the denied operation; state the limitation in your reply so the delegating agent can handle it."}],"source":{"kind":"plugin","plugin":"@deepseek-ai/dsh-system-prompt","form":"snapshot","sections":[{"name":"sandbox:policy","text":"Current DSH file policy: danger-full-access. The DSH file sandbox does not restrict file modifications by available operations."},{"name":"approval:policy","text":"Approval prompts are disabled in this session: actions that require approval are rejected automatically — do not request sandbox escalation (do not set `sandbox_permissions`)."},{"name":"subagent:delegation","text":"You are a delegated subagent: your permission scope was fixed when you were started and cannot be widened from inside this session — operations that require approval are rejected automatically. When the task needs access beyond that scope, do not retry the denied operation; state the limitation in your reply so the delegating agent can handle it."}]},"role":"user","id":"5832009f-12a3-4f6e-85e5-257c06f4c716"},"surfaceOp":"append"}
+{"type":"user/message","seq":7,"time":1786357521802,"data":{"content":[{"type":"text","text":"Current runtime context. This snapshot supersedes earlier runtime-context snapshots.\n\nCurrent DSH file policy: danger-full-access. The DSH file sandbox does not restrict file modifications by available operations.\n\nApproval prompts are disabled in this session: actions that require approval are rejected automatically — do not request sandbox escalation (do not set `sandbox_permissions`).\n\nYou are a delegated subagent: your permission scope was fixed when you were started and cannot be widened from inside this session — operations that require approval are rejected automatically. When the task needs access beyond that scope, do not retry the denied operation; state the limitation in your reply so the delegating agent can handle it."}],"source":{"kind":"plugin","plugin":"@deepseek-ai/dsh-system-prompt","form":"snapshot","sections":[{"name":"sandbox:policy","text":"Current DSH file policy: danger-full-access. The DSH file sandbox does not restrict file modifications by available operations."},{"name":"approval:policy","text":"Approval prompts are disabled in this session: actions that require approval are rejected automatically — do not request sandbox escalation (do not set `sandbox_permissions`)."},{"name":"subagent:delegation","text":"You are a delegated subagent: your permission scope was fixed when you were started and cannot be widened from inside this session — operations that require approval are rejected automatically. When the task needs access beyond that scope, do not retry the denied operation; state the limitation in your reply so the delegating agent can handle it."}]},"role":"user","id":"1cc862ff-09a2-496d-817a-c4281b4540d7"},"surfaceOp":"append"}
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examples/acp-agent/tests/snapshots/subagent-multi/session.jsonl

@@ -11,27 +11,27 @@
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-{"type":"tool/call","seq":165,"time":1785730447859,"data":{"turn":1,"step":2,"callId":"call_00_FudNKuJ0fchSptGy3Scw1411","name":"subagent","arguments":"{\"description\": \"Return BETA only\", \"prompt\": \"Reply with exactly the word BETA and nothing else.\"}"}}
-{"type":"tool/result","seq":166,"time":1785730447888,"data":{"turn":1,"step":2,"message":{"source":{"kind":"tool","callId":"call_00_FudNKuJ0fchSptGy3Scw1411"},"content":[{"type":"tool-result","toolCallId":"call_00_FudNKuJ0fchSptGy3Scw1411","content":[{"type":"text","text":"BETA"}],"isError":false}],"role":"user","id":"d882a00e-e991-4e2a-9610-698f6bc8924d"}},"sourceEventSeqs":[165],"surfaceOp":"append"}
+{"type":"assistant/message","seq":164,"time":1785730447858,"data":{"turn":1,"step":2,"message":{"role":"assistant","content":[{"type":"reasoning","text":"First subagent returned \"ALPHA\". Now I'll call the second subagent to return \"BETA\"."},{"type":"tool-call","id":"call_00_FudNKuJ0fchSptGy3Scw1411","name":"subagent","arguments":"{\"description\": \"Return BETA only\", \"prompt\": \"Reply with exactly the word BETA and nothing else.\", \"run_in_background\": false}"}],"source":{"kind":"model","provider":"deepseek-official","model":"deepseek-v4-flash"},"id":"6271fc4f-19d3-41fe-9500-8f15c823e262"},"usage":{"inputTokens":133,"outputTokens":96,"cacheReadTokens":2944,"reasoningTokens":23}},"sourceEventSeqs":[103,104,105,106,107,108,109,110,111,112,113,114,115,116,117,118,119,120,121,122,123,124,125,126,127,128,129,130,131,132,133,134,135,136,137,138,139,140,141,142,143,144,145,146,147,148,149,150,151,152,153,154,155,156,157,158,159,160,161,162,163],"surfaceOp":"append"}
+{"type":"tool/call","seq":165,"time":1785730447859,"data":{"turn":1,"step":2,"callId":"call_00_FudNKuJ0fchSptGy3Scw1411","name":"subagent","arguments":"{\"description\": \"Return BETA only\", \"prompt\": \"Reply with exactly the word BETA and nothing else.\", \"run_in_background\": false}"}}
+{"type":"tool/result","seq":166,"time":1785730447888,"data":{"turn":1,"step":2,"message":{"source":{"kind":"tool","callId":"call_00_FudNKuJ0fchSptGy3Scw1411"},"content":[{"type":"tool-result","toolCallId":"call_00_FudNKuJ0fchSptGy3Scw1411","content":[{"type":"text","text":"BETA"}],"isError":false}],"role":"user","id":"92fc990e-874a-4927-a918-7244bf2d4ff4"}},"sourceEventSeqs":[165],"surfaceOp":"append"}
 {"type":"step/end","seq":167,"time":1785730447888,"data":{"turn":1,"step":2}}
 {"type":"step/start","seq":168,"time":1785730447902,"data":{"turn":1,"step":3}}
 {"type":"assistant/chunk","seq":169,"time":1783352131045,"data":{"turn":1,"step":3,"chunk":{"type":"block-start","index":0,"blockType":"reasoning"}}}

examples/acp-agent/tests/snapshots/subagent-parallel/session.1.jsonl

@@ -1,18 +1,18 @@
 {"type":"session","version":0,"id":"bbbbbbbb-0000-4000-8000-000000000002","createdAt":1783352127000,"cwd":"{{cwd}}","parentSession":"aaaaaaaa-0000-4000-8000-000000000001","origin":"subagent","delegationDepth":1}
 {"type":"approval/policy","seq":0,"time":1786373947132,"data":{"policy":"never","source":"delegation"}}
-{"type":"agent/inbox/spliced","seq":1,"time":1786373947134,"data":{"target":"next-turn","start":0,"inserted":[{"content":[{"type":"text","text":"Reply with exactly the word ALPHA and nothing else."}],"source":{"kind":"user"},"role":"user","id":"84b2bc8e-878b-4337-ae82-26c3074069f2"}]}}
+{"type":"agent/inbox/spliced","seq":1,"time":1786373947134,"data":{"target":"next-turn","start":0,"inserted":[{"content":[{"type":"text","text":"Reply with exactly the word ALPHA and nothing else."}],"source":{"kind":"user"},"role":"user","id":"fcb407e0-2c85-4875-81cf-ad18fd96e3dc"}]}}
 {"type":"turn/start","seq":2,"time":1786373947134,"data":{"turn":1}}
 {"type":"agent/inbox/spliced","seq":3,"time":1786373947134,"data":{"target":"next-turn","start":0,"removedCount":1,"inserted":[]}}
 {"type":"subagent/descriptor","seq":4,"time":1786373947165,"data":{"version":2,"mode":"one-shot","provider":"spawn","label":"Say the word ALPHA"}}
 {"type":"step/start","seq":5,"time":1786373947168,"data":{"turn":1,"step":1}}
-{"type":"user/message","seq":6,"time":1786338530759,"data":{"content":[{"type":"text","text":"Reply with exactly the word ALPHA and nothing else."}],"source":{"kind":"user"},"role":"user","id":"84b2bc8e-878b-4337-ae82-26c3074069f2"},"surfaceOp":"append"}
-{"type":"user/message","seq":7,"time":1786373947168,"data":{"content":[{"type":"text","text":"Current runtime context. This snapshot supersedes earlier runtime-context snapshots.\n\nCurrent DSH file policy: danger-full-access. The DSH file sandbox does not restrict file modifications by available operations.\n\nApproval prompts are disabled in this session: actions that require approval are rejected automatically — do not request sandbox escalation (do not set `sandbox_permissions`).\n\nYou are a delegated subagent: your permission scope was fixed when you were started and cannot be widened from inside this session — operations that require approval are rejected automatically. When the task needs access beyond that scope, do not retry the denied operation; state the limitation in your reply so the delegating agent can handle it."}],"source":{"kind":"plugin","plugin":"@deepseek-ai/dsh-system-prompt","form":"snapshot","sections":[{"name":"sandbox:policy","text":"Current DSH file policy: danger-full-access. The DSH file sandbox does not restrict file modifications by available operations."},{"name":"approval:policy","text":"Approval prompts are disabled in this session: actions that require approval are rejected automatically — do not request sandbox escalation (do not set `sandbox_permissions`)."},{"name":"subagent:delegation","text":"You are a delegated subagent: your permission scope was fixed when you were started and cannot be widened from inside this session — operations that require approval are rejected automatically. When the task needs access beyond that scope, do not retry the denied operation; state the limitation in your reply so the delegating agent can handle it."}]},"role":"user","id":"05fbd821-3adf-4877-b805-2cc5e6de3f9c"},"surfaceOp":"append"}
+{"type":"user/message","seq":6,"time":1786338530759,"data":{"content":[{"type":"text","text":"Reply with exactly the word ALPHA and nothing else."}],"source":{"kind":"user"},"role":"user","id":"fcb407e0-2c85-4875-81cf-ad18fd96e3dc"},"surfaceOp":"append"}
+{"type":"user/message","seq":7,"time":1786373947168,"data":{"content":[{"type":"text","text":"Current runtime context. This snapshot supersedes earlier runtime-context snapshots.\n\nCurrent DSH file policy: danger-full-access. The DSH file sandbox does not restrict file modifications by available operations.\n\nApproval prompts are disabled in this session: actions that require approval are rejected automatically — do not request sandbox escalation (do not set `sandbox_permissions`).\n\nYou are a delegated subagent: your permission scope was fixed when you were started and cannot be widened from inside this session — operations that require approval are rejected automatically. When the task needs access beyond that scope, do not retry the denied operation; state the limitation in your reply so the delegating agent can handle it."}],"source":{"kind":"plugin","plugin":"@deepseek-ai/dsh-system-prompt","form":"snapshot","sections":[{"name":"sandbox:policy","text":"Current DSH file policy: danger-full-access. The DSH file sandbox does not restrict file modifications by available operations."},{"name":"approval:policy","text":"Approval prompts are disabled in this session: actions that require approval are rejected automatically — do not request sandbox escalation (do not set `sandbox_permissions`)."},{"name":"subagent:delegation","text":"You are a delegated subagent: your permission scope was fixed when you were started and cannot be widened from inside this session — operations that require approval are rejected automatically. When the task needs access beyond that scope, do not retry the denied operation; state the limitation in your reply so the delegating agent can handle it."}]},"role":"user","id":"43134073-e26c-4314-a019-95f39d40ab19"},"surfaceOp":"append"}
 {"type":"session/title","seq":8,"time":1786373947168,"data":{"title":"Reply with exactly the word","messageSeqs":[6],"source":{"kind":"fallback"}}}
 {"type":"request/header","seq":9,"time":1786338530759,"data":{"header":{"config":{"provider":"deepseek-official","model":"deepseek-v4-flash"},"system":"{{system}}","tools":"{{tools}}"},"reason":"initial"}}
 {"type":"request/context","seq":10,"time":1786338530759,"data":{"provider":"deepseek-official","model":"deepseek-v4-flash"}}
 {"type":"assistant/chunk","seq":11,"time":1786338530769,"data":{"turn":1,"step":1,"chunk":{"type":"block-start","index":0,"blockType":"text"}}}
 {"type":"assistant/chunk","seq":12,"time":1786338530769,"data":{"turn":1,"step":1,"chunk":{"type":"block-end","index":0,"block":{"type":"text","text":"ALPHA"}}}}
 {"type":"assistant/chunk","seq":13,"time":1786338530769,"data":{"turn":1,"step":1,"chunk":{"type":"finish","reason":{"kind":"stop"}}}}
-{"type":"assistant/message","seq":14,"time":1786338530769,"data":{"turn":1,"step":1,"message":{"role":"assistant","content":[{"type":"text","text":"ALPHA"}],"source":{"kind":"model","provider":"deepseek-official","model":"deepseek-v4-flash"},"id":"224c83f1-4449-451d-8f8a-f2889c19068e"}},"sourceEventSeqs":[11,12,13],"surfaceOp":"append"}
+{"type":"assistant/message","seq":14,"time":1786338530769,"data":{"turn":1,"step":1,"message":{"role":"assistant","content":[{"type":"text","text":"ALPHA"}],"source":{"kind":"model","provider":"deepseek-official","model":"deepseek-v4-flash"},"id":"4923daf1-fb8a-4278-b173-477ff3e36df0"}},"sourceEventSeqs":[11,12,13],"surfaceOp":"append"}
 {"type":"step/end","seq":15,"time":1786338530769,"data":{"turn":1,"step":1}}
 {"type":"turn/end","seq":16,"time":1786338530769,"data":{"turn":1,"reason":{"kind":"completed"}}}

examples/acp-agent/tests/snapshots/subagent-parallel/session.2.jsonl

@@ -1,18 +1,18 @@
 {"type":"session","version":0,"id":"cccccccc-0000-4000-8000-000000000003","createdAt":1783352127001,"cwd":"{{cwd}}","parentSession":"aaaaaaaa-0000-4000-8000-000000000001","origin":"subagent","delegationDepth":1}
 {"type":"approval/policy","seq":0,"time":1786373947132,"data":{"policy":"never","source":"delegation"}}
-{"type":"agent/inbox/spliced","seq":1,"time":1786373947133,"data":{"target":"next-turn","start":0,"inserted":[{"content":[{"type":"text","text":"Reply with exactly the word ALPHA and nothing else."}],"source":{"kind":"user"},"role":"user","id":"a3da85dc-6428-4a31-8653-b7327e518436"}]}}
+{"type":"agent/inbox/spliced","seq":1,"time":1786373947133,"data":{"target":"next-turn","start":0,"inserted":[{"content":[{"type":"text","text":"Reply with exactly the word ALPHA and nothing else."}],"source":{"kind":"user"},"role":"user","id":"f768a0a8-04f9-4dbe-baf0-a55a2be33866"}]}}
 {"type":"turn/start","seq":2,"time":1786373947133,"data":{"turn":1}}
 {"type":"agent/inbox/spliced","seq":3,"time":1786373947134,"data":{"target":"next-turn","start":0,"removedCount":1,"inserted":[]}}
 {"type":"subagent/descriptor","seq":4,"time":1786373947170,"data":{"version":2,"mode":"one-shot","provider":"spawn","label":"Say the word ALPHA"}}
 {"type":"step/start","seq":5,"time":1786373947173,"data":{"turn":1,"step":1}}
-{"type":"user/message","seq":6,"time":1786338530749,"data":{"content":[{"type":"text","text":"Reply with exactly the word ALPHA and nothing else."}],"source":{"kind":"user"},"role":"user","id":"a3da85dc-6428-4a31-8653-b7327e518436"},"surfaceOp":"append"}
-{"type":"user/message","seq":7,"time":1786373947174,"data":{"content":[{"type":"text","text":"Current runtime context. This snapshot supersedes earlier runtime-context snapshots.\n\nCurrent DSH file policy: danger-full-access. The DSH file sandbox does not restrict file modifications by available operations.\n\nApproval prompts are disabled in this session: actions that require approval are rejected automatically — do not request sandbox escalation (do not set `sandbox_permissions`).\n\nYou are a delegated subagent: your permission scope was fixed when you were started and cannot be widened from inside this session — operations that require approval are rejected automatically. When the task needs access beyond that scope, do not retry the denied operation; state the limitation in your reply so the delegating agent can handle it."}],"source":{"kind":"plugin","plugin":"@deepseek-ai/dsh-system-prompt","form":"snapshot","sections":[{"name":"sandbox:policy","text":"Current DSH file policy: danger-full-access. The DSH file sandbox does not restrict file modifications by available operations."},{"name":"approval:policy","text":"Approval prompts are disabled in this session: actions that require approval are rejected automatically — do not request sandbox escalation (do not set `sandbox_permissions`)."},{"name":"subagent:delegation","text":"You are a delegated subagent: your permission scope was fixed when you were started and cannot be widened from inside this session — operations that require approval are rejected automatically. When the task needs access beyond that scope, do not retry the denied operation; state the limitation in your reply so the delegating agent can handle it."}]},"role":"user","id":"670f5fc4-3eb6-4430-959a-08e8adf25036"},"surfaceOp":"append"}
+{"type":"user/message","seq":6,"time":1786338530749,"data":{"content":[{"type":"text","text":"Reply with exactly the word ALPHA and nothing else."}],"source":{"kind":"user"},"role":"user","id":"f768a0a8-04f9-4dbe-baf0-a55a2be33866"},"surfaceOp":"append"}
+{"type":"user/message","seq":7,"time":1786373947174,"data":{"content":[{"type":"text","text":"Current runtime context. This snapshot supersedes earlier runtime-context snapshots.\n\nCurrent DSH file policy: danger-full-access. The DSH file sandbox does not restrict file modifications by available operations.\n\nApproval prompts are disabled in this session: actions that require approval are rejected automatically — do not request sandbox escalation (do not set `sandbox_permissions`).\n\nYou are a delegated subagent: your permission scope was fixed when you were started and cannot be widened from inside this session — operations that require approval are rejected automatically. When the task needs access beyond that scope, do not retry the denied operation; state the limitation in your reply so the delegating agent can handle it."}],"source":{"kind":"plugin","plugin":"@deepseek-ai/dsh-system-prompt","form":"snapshot","sections":[{"name":"sandbox:policy","text":"Current DSH file policy: danger-full-access. The DSH file sandbox does not restrict file modifications by available operations."},{"name":"approval:policy","text":"Approval prompts are disabled in this session: actions that require approval are rejected automatically — do not request sandbox escalation (do not set `sandbox_permissions`)."},{"name":"subagent:delegation","text":"You are a delegated subagent: your permission scope was fixed when you were started and cannot be widened from inside this session — operations that require approval are rejected automatically. When the task needs access beyond that scope, do not retry the denied operation; state the limitation in your reply so the delegating agent can handle it."}]},"role":"user","id":"2934ee83-26a7-4262-8517-e4fe8f97312a"},"surfaceOp":"append"}
 {"type":"session/title","seq":8,"time":1786373947174,"data":{"title":"Reply with exactly the word","messageSeqs":[6],"source":{"kind":"fallback"}}}
 {"type":"request/header","seq":9,"time":1786338530749,"data":{"header":{"config":{"provider":"deepseek-official","model":"deepseek-v4-flash"},"system":"{{system}}","tools":"{{tools}}"},"reason":"initial"}}
 {"type":"request/context","seq":10,"time":1786338530749,"data":{"provider":"deepseek-official","model":"deepseek-v4-flash"}}
 {"type":"assistant/chunk","seq":11,"time":1786338530759,"data":{"turn":1,"step":1,"chunk":{"type":"block-start","index":0,"blockType":"text"}}}
 {"type":"assistant/chunk","seq":12,"time":1786338530759,"data":{"turn":1,"step":1,"chunk":{"type":"block-end","index":0,"block":{"type":"text","text":"ALPHA"}}}}
 {"type":"assistant/chunk","seq":13,"time":1786338530759,"data":{"turn":1,"step":1,"chunk":{"type":"finish","reason":{"kind":"stop"}}}}
-{"type":"assistant/message","seq":14,"time":1786338530759,"data":{"turn":1,"step":1,"message":{"role":"assistant","content":[{"type":"text","text":"ALPHA"}],"source":{"kind":"model","provider":"deepseek-official","model":"deepseek-v4-flash"},"id":"ac2dc91f-7dfa-45f6-88e0-21a2e762c3dd"}},"sourceEventSeqs":[11,12,13],"surfaceOp":"append"}
+{"type":"assistant/message","seq":14,"time":1786338530759,"data":{"turn":1,"step":1,"message":{"role":"assistant","content":[{"type":"text","text":"ALPHA"}],"source":{"kind":"model","provider":"deepseek-official","model":"deepseek-v4-flash"},"id":"013bb4a7-f401-4d39-8552-15232d042d26"}},"sourceEventSeqs":[11,12,13],"surfaceOp":"append"}
 {"type":"step/end","seq":15,"time":1786338530760,"data":{"turn":1,"step":1}}
 {"type":"turn/end","seq":16,"time":1786338530760,"data":{"turn":1,"reason":{"kind":"completed"}}}

examples/acp-agent/tests/snapshots/subagent-parallel/session.jsonl

@@ -9,15 +9,15 @@
 {"type":"request/header","seq":7,"time":1786338530717,"data":{"header":{"config":{"provider":"deepseek-official","model":"deepseek-v4-flash"},"system":"{{system}}","tools":"{{tools}}"},"reason":"initial"}}
 {"type":"request/context","seq":8,"time":1786338530717,"data":{"provider":"deepseek-official","model":"deepseek-v4-flash"}}
 {"type":"assistant/chunk","seq":9,"time":1786338530722,"data":{"turn":1,"step":1,"chunk":{"type":"block-start","index":0,"blockType":"tool-call"}}}
-{"type":"assistant/chunk","seq":10,"time":1786338530722,"data":{"turn":1,"step":1,"chunk":{"type":"block-end","index":0,"block":{"type":"tool-call","id":"call_parallel_alpha_1","name":"subagent","arguments":"{\"description\": \"Say the word ALPHA\", \"prompt\": \"Reply with exactly the word ALPHA and nothing else.\"}"}}}}
+{"type":"assistant/chunk","seq":10,"time":1786338530722,"data":{"turn":1,"step":1,"chunk":{"type":"block-end","index":0,"block":{"type":"tool-call","id":"call_parallel_alpha_1","name":"subagent","arguments":"{\"description\": \"Say the word ALPHA\", \"prompt\": \"Reply with exactly the word ALPHA and nothing else.\", \"run_in_background\":false}"}}}}
 {"type":"assistant/chunk","seq":11,"time":1786338530722,"data":{"turn":1,"step":1,"chunk":{"type":"block-start","index":1,"blockType":"tool-call"}}}
-{"type":"assistant/chunk","seq":12,"time":1786338530722,"data":{"turn":1,"step":1,"chunk":{"type":"block-end","index":1,"block":{"type":"tool-call","id":"call_parallel_alpha_2","name":"subagent","arguments":"{\"description\": \"Say the word ALPHA\", \"prompt\": \"Reply with exactly the word ALPHA and nothing else.\"}"}}}}
+{"type":"assistant/chunk","seq":12,"time":1786338530722,"data":{"turn":1,"step":1,"chunk":{"type":"block-end","index":1,"block":{"type":"tool-call","id":"call_parallel_alpha_2","name":"subagent","arguments":"{\"description\": \"Say the word ALPHA\", \"prompt\": \"Reply with exactly the word ALPHA and nothing else.\", \"run_in_background\":false}"}}}}
 {"type":"assistant/chunk","seq":13,"time":1786338530722,"data":{"turn":1,"step":1,"chunk":{"type":"finish","reason":{"kind":"tool-calls"}}}}
-{"type":"assistant/message","seq":14,"time":1786338530723,"data":{"turn":1,"step":1,"message":{"role":"assistant","content":[{"type":"tool-call","id":"call_parallel_alpha_1","name":"subagent","arguments":"{\"description\": \"Say the word ALPHA\", \"prompt\": \"Reply with exactly the word ALPHA and nothing else.\"}"},{"type":"tool-call","id":"call_parallel_alpha_2","name":"subagent","arguments":"{\"description\": \"Say the word ALPHA\", \"prompt\": \"Reply with exactly the word ALPHA and nothing else.\"}"}],"source":{"kind":"model","provider":"deepseek-official","model":"deepseek-v4-flash"},"id":"6ff33634-55af-4c37-a491-dd5b8673923f"}},"sourceEventSeqs":[9,10,11,12,13],"surfaceOp":"append"}
-{"type":"tool/call","seq":15,"time":1786338530723,"data":{"turn":1,"step":1,"callId":"call_parallel_alpha_1","name":"subagent","arguments":"{\"description\": \"Say the word ALPHA\", \"prompt\": \"Reply with exactly the word ALPHA and nothing else.\"}"}}
-{"type":"tool/call","seq":16,"time":1786338530723,"data":{"turn":1,"step":1,"callId":"call_parallel_alpha_2","name":"subagent","arguments":"{\"description\": \"Say the word ALPHA\", \"prompt\": \"Reply with exactly the word ALPHA and nothing else.\"}"}}
-{"type":"tool/result","seq":17,"time":1786338530770,"data":{"turn":1,"step":1,"message":{"source":{"kind":"tool","callId":"call_parallel_alpha_1"},"content":[{"type":"tool-result","toolCallId":"call_parallel_alpha_1","content":[{"type":"text","text":"ALPHA"}],"isError":false}],"role":"user","id":"9fa4fa59-7326-4bc8-8ea2-120b37d91ea3"}},"sourceEventSeqs":[15],"surfaceOp":"append"}
-{"type":"tool/result","seq":18,"time":1786338530770,"data":{"turn":1,"step":1,"message":{"source":{"kind":"tool","callId":"call_parallel_alpha_2"},"content":[{"type":"tool-result","toolCallId":"call_parallel_alpha_2","content":[{"type":"text","text":"ALPHA"}],"isError":false}],"role":"user","id":"895bb620-534e-4857-9743-68273126eccf"}},"sourceEventSeqs":[16],"surfaceOp":"append"}
+{"type":"assistant/message","seq":14,"time":1786338530723,"data":{"turn":1,"step":1,"message":{"role":"assistant","content":[{"type":"tool-call","id":"call_parallel_alpha_1","name":"subagent","arguments":"{\"description\": \"Say the word ALPHA\", \"prompt\": \"Reply with exactly the word ALPHA and nothing else.\", \"run_in_background\":false}"},{"type":"tool-call","id":"call_parallel_alpha_2","name":"subagent","arguments":"{\"description\": \"Say the word ALPHA\", \"prompt\": \"Reply with exactly the word ALPHA and nothing else.\", \"run_in_background\":false}"}],"source":{"kind":"model","provider":"deepseek-official","model":"deepseek-v4-flash"},"id":"6ff33634-55af-4c37-a491-dd5b8673923f"}},"sourceEventSeqs":[9,10,11,12,13],"surfaceOp":"append"}
+{"type":"tool/call","seq":15,"time":1786338530723,"data":{"turn":1,"step":1,"callId":"call_parallel_alpha_1","name":"subagent","arguments":"{\"description\": \"Say the word ALPHA\", \"prompt\": \"Reply with exactly the word ALPHA and nothing else.\", \"run_in_background\":false}"}}
+{"type":"tool/call","seq":16,"time":1786338530723,"data":{"turn":1,"step":1,"callId":"call_parallel_alpha_2","name":"subagent","arguments":"{\"description\": \"Say the word ALPHA\", \"prompt\": \"Reply with exactly the word ALPHA and nothing else.\", \"run_in_background\":false}"}}
+{"type":"tool/result","seq":17,"time":1786338530770,"data":{"turn":1,"step":1,"message":{"source":{"kind":"tool","callId":"call_parallel_alpha_1"},"content":[{"type":"tool-result","toolCallId":"call_parallel_alpha_1","content":[{"type":"text","text":"ALPHA"}],"isError":false}],"role":"user","id":"caa3552f-81bf-415c-852f-1c88ca1b29b3"}},"sourceEventSeqs":[15],"surfaceOp":"append"}
+{"type":"tool/result","seq":18,"time":1786338530770,"data":{"turn":1,"step":1,"message":{"source":{"kind":"tool","callId":"call_parallel_alpha_2"},"content":[{"type":"tool-result","toolCallId":"call_parallel_alpha_2","content":[{"type":"text","text":"ALPHA"}],"isError":false}],"role":"user","id":"ef6b5f6f-94bb-4719-a914-87bc0366660a"}},"sourceEventSeqs":[16],"surfaceOp":"append"}
 {"type":"step/end","seq":19,"time":1786338530770,"data":{"turn":1,"step":1}}
 {"type":"step/start","seq":20,"time":1786338530778,"data":{"turn":1,"step":2}}
 {"type":"assistant/chunk","seq":21,"time":1786338530782,"data":{"turn":1,"step":2,"chunk":{"type":"block-start","index":0,"blockType":"text"}}}

examples/acp-agent/tests/snapshots/subagent-published-run-failure/replay.override.json

@@ -3,8 +3,8 @@
     "kind": "chunks",
     "chunks": [
       { "type": "block-start", "index": 0, "blockType": "tool-call" },
-      { "type": "tool-call-delta", "index": 0, "id": "call_published_failure", "name": "subagent", "argumentsDelta": "{\"description\":\"Fail published run\",\"prompt\":\"This child prompt must never run.\"}" },
-      { "type": "block-end", "index": 0, "block": { "type": "tool-call", "id": "call_published_failure", "name": "subagent", "arguments": "{\"description\":\"Fail published run\",\"prompt\":\"This child prompt must never run.\"}" } },
+      { "type": "tool-call-delta", "index": 0, "id": "call_published_failure", "name": "subagent", "argumentsDelta": "{\"description\":\"Fail published run\",\"prompt\":\"This child prompt must never run.\",\"run_in_background\":false}" },
+      { "type": "block-end", "index": 0, "block": { "type": "tool-call", "id": "call_published_failure", "name": "subagent", "arguments": "{\"description\":\"Fail published run\",\"prompt\":\"This child prompt must never run.\",\"run_in_background\":false}" } },
       { "type": "usage", "usage": { "inputTokens": 10, "outputTokens": 5 } },
       { "type": "finish", "reason": { "kind": "tool-calls" } }
     ]

examples/acp-agent/tests/snapshots/subagent-published-run-failure/session.1.jsonl

@@ -1,2 +1,2 @@
 {"type":"session","version":0,"id":"eb69342c-62b6-4320-a78b-961745f89333","createdAt":1786358409171,"cwd":"{{cwd}}","parentSession":"11111111-1111-4111-8111-111111111111","origin":"subagent","delegationDepth":1}
-{"type":"approval/policy","seq":0,"time":1786358409171,"data":{"policy":"never","source":"delegation"}}
+{"type":"approval/policy","seq":0,"time":1786443070419,"data":{"policy":"never","source":"delegation"}}

examples/acp-agent/tests/snapshots/subagent-published-run-failure/session.jsonl

@@ -9,13 +9,13 @@
 {"type":"request/header","seq":7,"time":1785730452506,"data":{"header":{"config":{"provider":"deepseek-official","model":"deepseek-v4-flash"},"system":"{{system}}","tools":"{{tools}}"},"reason":"initial"}}
 {"type":"request/context","seq":8,"time":1785730452506,"data":{"provider":"deepseek-official","model":"deepseek-v4-flash"}}
 {"type":"assistant/chunk","seq":9,"time":0,"data":{"turn":1,"step":1,"chunk":{"type":"block-start","index":0,"blockType":"tool-call"}}}
-{"type":"assistant/chunk","seq":10,"time":0,"data":{"turn":1,"step":1,"chunk":{"type":"tool-call-delta","index":0,"id":"call_published_failure","name":"subagent","argumentsDelta":"{\"description\":\"Fail published run\",\"prompt\":\"This child prompt must never run.\"}"}}}
-{"type":"assistant/chunk","seq":11,"time":1785537317619,"data":{"turn":1,"step":1,"chunk":{"type":"block-end","index":0,"block":{"type":"tool-call","id":"call_published_failure","name":"subagent","arguments":"{\"description\":\"Fail published run\",\"prompt\":\"This child prompt must never run.\"}"}}}}
+{"type":"assistant/chunk","seq":10,"time":0,"data":{"turn":1,"step":1,"chunk":{"type":"tool-call-delta","index":0,"id":"call_published_failure","name":"subagent","argumentsDelta":"{\"description\":\"Fail published run\",\"prompt\":\"This child prompt must never run.\",\"run_in_background\":false}"}}}
+{"type":"assistant/chunk","seq":11,"time":1785537317619,"data":{"turn":1,"step":1,"chunk":{"type":"block-end","index":0,"block":{"type":"tool-call","id":"call_published_failure","name":"subagent","arguments":"{\"description\":\"Fail published run\",\"prompt\":\"This child prompt must never run.\",\"run_in_background\":false}"}}}}
 {"type":"assistant/chunk","seq":12,"time":1785537317619,"data":{"turn":1,"step":1,"chunk":{"type":"usage","usage":{"inputTokens":10,"outputTokens":5}}}}
 {"type":"assistant/chunk","seq":13,"time":1785730452515,"data":{"turn":1,"step":1,"chunk":{"type":"finish","reason":{"kind":"tool-calls"}}}}
-{"type":"assistant/message","seq":14,"time":1785730452515,"data":{"turn":1,"step":1,"message":{"role":"assistant","content":[{"type":"tool-call","id":"call_published_failure","name":"subagent","arguments":"{\"description\":\"Fail published run\",\"prompt\":\"This child prompt must never run.\"}"}],"source":{"kind":"model","provider":"deepseek-official","model":"deepseek-v4-flash"},"id":"6af49587-fae3-4027-922d-bdc7b833e6d2"},"usage":{"inputTokens":10,"outputTokens":5}},"sourceEventSeqs":[9,10,11,12,13],"surfaceOp":"append"}
-{"type":"tool/call","seq":15,"time":1785730452515,"data":{"turn":1,"step":1,"callId":"call_published_failure","name":"subagent","arguments":"{\"description\":\"Fail published run\",\"prompt\":\"This child prompt must never run.\"}"}}
-{"type":"tool/result","seq":16,"time":1785730452525,"data":{"turn":1,"step":1,"message":{"source":{"kind":"tool","callId":"call_published_failure"},"content":[{"type":"tool-result","toolCallId":"call_published_failure","content":[{"type":"text","text":"Error: subagent run failed: Error: snapshot published run failed; dispose failed: Error: snapshot published handle disposal failed"}],"isError":true}],"role":"user","id":"9a913910-4a99-4a22-825f-2cf9d51e665a"}},"sourceEventSeqs":[15],"surfaceOp":"append"}
+{"type":"assistant/message","seq":14,"time":1785730452515,"data":{"turn":1,"step":1,"message":{"role":"assistant","content":[{"type":"tool-call","id":"call_published_failure","name":"subagent","arguments":"{\"description\":\"Fail published run\",\"prompt\":\"This child prompt must never run.\",\"run_in_background\":false}"}],"source":{"kind":"model","provider":"deepseek-official","model":"deepseek-v4-flash"},"id":"bcc7161a-d563-47ed-a854-1ccf563992cb"},"usage":{"inputTokens":10,"outputTokens":5}},"sourceEventSeqs":[9,10,11,12,13],"surfaceOp":"append"}
+{"type":"tool/call","seq":15,"time":1785730452515,"data":{"turn":1,"step":1,"callId":"call_published_failure","name":"subagent","arguments":"{\"description\":\"Fail published run\",\"prompt\":\"This child prompt must never run.\",\"run_in_background\":false}"}}
+{"type":"tool/result","seq":16,"time":1785730452525,"data":{"turn":1,"step":1,"message":{"source":{"kind":"tool","callId":"call_published_failure"},"content":[{"type":"tool-result","toolCallId":"call_published_failure","content":[{"type":"text","text":"Error: subagent run failed: Error: snapshot published run failed; dispose failed: Error: snapshot published handle disposal failed"}],"isError":true}],"role":"user","id":"280647fb-2acf-45e4-9b20-cbdad027fbfa"}},"sourceEventSeqs":[15],"surfaceOp":"append"}
 {"type":"step/end","seq":17,"time":1785730452525,"data":{"turn":1,"step":1}}
 {"type":"step/start","seq":18,"time":1785730452536,"data":{"turn":1,"step":2}}
 {"type":"assistant/chunk","seq":19,"time":0,"data":{"turn":1,"step":2,"chunk":{"type":"block-start","index":0,"blockType":"text"}}}

examples/acp-agent/tests/snapshots/subagent-report/system-prompt.1.expected.md

@@ -21,4 +21,6 @@ Use the workflow tool ONLY when the user explicitly asks for a workflow or for l
 
 Use the ralph tool ONLY when the direct human explicitly asks for a Ralph loop or fresh-agent iterative execution. Each Ralph round starts a fresh child with no conversation seed and uses the shared workspace as durable memory. Completion and blockers are worker reports, not independent evaluation. Use same-session goal tools for ordinary long-running objectives, and plain subagents or workflows for bounded delegation and fan-out.
 
+Use subagent in the background by default. Start independent delegations together in one assistant message and continue useful work while they run. Set `run_in_background: false` only when your next action depends on that subagent's result. When a background run settles, the runtime sends you a notice containing its outcome and any final assistant message.
+
 Deliver your result with the report tool before you finish: call it once with a self-contained answer. The agent that started you shares your workspace but does not automatically receive your transcript, tool output, or reasoning, so a closing remark such as "done" leaves it nothing it can use. Report earlier as well whenever a partial finding changes what that agent should do next; reporting never ends your turn.

examples/acp-agent/tests/snapshots/subagent-report/tool-schemas.1.expected.json

@@ -247,7 +247,7 @@
     },
     {
       "name": "subagent",
-      "description": "Delegate a self-contained task to a subagent (a separate agent that works in its own context) and return its final result. Use this to offload focused, independent work — research, a scoped implementation, an analysis — so it does not consume this conversation's context. The subagent runs to completion and you receive only its final answer, not its intermediate steps. Give it a complete, standalone prompt: it does not see this conversation. Set `run_in_background: true` to start a background subagent that keeps its conversation: this call returns only its subagent id, and the subagent works on its own from there. You are told when it finishes, so never poll or wait on it; `send_message` sends it more work.",
+      "description": "Delegate a self-contained task to a subagent (a separate agent that works in its own context) to offload focused, independent work — research, a scoped implementation, an analysis — so it does not consume this conversation's context. The subagent returns its result, not its intermediate steps. Give it a complete, standalone prompt: it does not see this conversation. This tool runs in the background by default, immediately returns a durable subagent id, and keeps the child conversation available for later turns. When that run settles, the runtime sends the parent a notice containing its outcome and any final assistant message; `send_message` starts a later turn in the same child conversation. Set `run_in_background: false` only when your next action depends on receiving the result.",
       "parameters": {
         "type": "object",
         "properties": {
@@ -261,7 +261,7 @@
           },
           "run_in_background": {
             "type": "boolean",
-            "description": "Run as a background subagent that keeps its conversation and return only its subagent id. This call does not wait for it; you are told when it finishes. Send it more work with send_message."
+            "description": "Whether to run in the background and return a durable subagent id immediately. Defaults to true. Set false to wait for the result when your next action depends on it."
           }
         },
         "required": [
@@ -272,7 +272,7 @@
     },
     {
       "name": "subagent_fork",
-      "description": "Delegate a task to a subagent that inherits this conversation: a child agent seeded with all completed turns so far (it does not see the current in-flight turn), returning only its final result. Use this when the subtask builds on this conversation's context — a follow-up analysis, a review, a continuation — without consuming this conversation's context for the work itself. You receive only its final answer, not its intermediate steps.",
+      "description": "Delegate a task to a subagent that inherits this conversation: a child agent seeded with all completed turns so far (it does not see the current in-flight turn). Use this when the subtask builds on this conversation's context — a follow-up analysis, a review, a continuation — without consuming this conversation's context for the work itself. You receive its result, not its intermediate steps. This call waits for the subagent and returns its result.",
       "parameters": {
         "type": "object",
         "properties": {

examples/acp-agent/tests/snapshots/subagent-spawn/session.jsonl

@@ -11,14 +11,14 @@
 {"type":"assistant/chunk","seq":9,"time":1783352120053,"data":{"turn":1,"step":1,"chunk":{"type":"block-start","index":0,"blockType":"reasoning"}}}
 {"type":"reasoning-chunks","seq0":10,"time0":1783352120080,"data":{"turn":1,"step":1,"index":0,"dt":[1,0,30,1,0,0,1,23,1,0,0,0,0,27,0,28,0,29,0,0,0,0,1,26,0,1,0,0,0,28,0,0,1,0,27,0,0,1,0,0,28,0,0,0,0,0,27,1,0,32,1,0,1,0,1,0,24,0,28,1,0,0,0,26,56,0],"texts":["The"," user"," wants"," me"," to",":\n","1","."," Use"," the"," sub","agent"," tool"," exactly"," once"," to"," delegate"," the"," task",":"," \"","Reply"," with"," exactly"," the"," word"," CH","ILD","_OK"," and"," nothing"," else",".\"\n","2","."," After"," the"," sub","agent"," returns",","," reply"," with"," the"," single"," word"," PAR","ENT","_D","ONE"," and"," stop",".\n","3","."," Do"," not"," use"," the"," bash"," tool",".\n\n","Let"," me"," do"," this","."]}}
 {"type":"assistant/chunk","seq":77,"time":1783352120559,"data":{"turn":1,"step":1,"chunk":{"type":"block-start","index":1,"blockType":"tool-call"}}}
-{"type":"tool-call-chunks","seq0":78,"time0":1783352120560,"data":{"turn":1,"step":1,"index":1,"dt":[0,28,0,0,0,29,1,0,0,25,28,0,0,1,0,28,2,0,1,25,1,0,0,0,0,36,0,1,0,0,18,67,0],"id":"call_00_gVbLWC12Qu8JheZpVRRz8749","name":"subagent","args":["","{","\"","description","\"",": ","\"","Reply"," with"," CH","ILD","_OK","\"",", ","\"","prom","pt","\"",": ","\"","Reply"," with"," exactly"," the"," word"," CH","ILD","_OK"," and"," nothing"," else",".","\"","}"]}}
+{"type":"tool-call-chunks","seq0":78,"time0":1783352120560,"data":{"turn":1,"step":1,"index":1,"dt":[0,28,0,0,0,29,1,0,0,25,28,0,0,1,0,28,2,0,1,25,1,0,0,0,0,36,0,1,0,0,18,67,0],"id":"call_00_gVbLWC12Qu8JheZpVRRz8749","name":"subagent","args":["","{","\"","description","\"",": ","\"","Reply"," with"," CH","ILD","_OK","\"",", ","\"","prom","pt","\"",": ","\"","Reply"," with"," exactly"," the"," word"," CH","ILD","_OK"," and"," nothing"," else",".","\"",", \"run_in_background\":false}"]}}
 {"type":"assistant/chunk","seq":112,"time":1783352120852,"data":{"turn":1,"step":1,"chunk":{"type":"block-end","index":0,"block":{"type":"reasoning","text":"The user wants me to:\n1. Use the subagent tool exactly once to delegate the task: \"Reply with exactly the word CHILD_OK and nothing else.\"\n2. After the subagent returns, reply with the single word PARENT_DONE and stop.\n3. Do not use the bash tool.\n\nLet me do this."}}}}
-{"type":"assistant/chunk","seq":113,"time":1783352120852,"data":{"turn":1,"step":1,"chunk":{"type":"block-end","index":1,"block":{"type":"tool-call","id":"call_00_gVbLWC12Qu8JheZpVRRz8749","name":"subagent","arguments":"{\"description\": \"Reply with CHILD_OK\", \"prompt\": \"Reply with exactly the word CHILD_OK and nothing else.\"}"}}}}
+{"type":"assistant/chunk","seq":113,"time":1783352120852,"data":{"turn":1,"step":1,"chunk":{"type":"block-end","index":1,"block":{"type":"tool-call","id":"call_00_gVbLWC12Qu8JheZpVRRz8749","name":"subagent","arguments":"{\"description\": \"Reply with CHILD_OK\", \"prompt\": \"Reply with exactly the word CHILD_OK and nothing else.\", \"run_in_background\":false}"}}}}
 {"type":"assistant/chunk","seq":114,"time":1785498793638,"data":{"turn":1,"step":1,"chunk":{"type":"usage","usage":{"inputTokens":2907,"outputTokens":142,"cacheReadTokens":0,"reasoningTokens":67}}}}
 {"type":"assistant/chunk","seq":115,"time":1785730446696,"data":{"turn":1,"step":1,"chunk":{"type":"finish","reason":{"kind":"tool-calls"}}}}
-{"type":"assistant/message","seq":116,"time":1785730446697,"data":{"turn":1,"step":1,"message":{"role":"assistant","content":[{"type":"reasoning","text":"The user wants me to:\n1. Use the subagent tool exactly once to delegate the task: \"Reply with exactly the word CHILD_OK and nothing else.\"\n2. After the subagent returns, reply with the single word PARENT_DONE and stop.\n3. Do not use the bash tool.\n\nLet me do this."},{"type":"tool-call","id":"call_00_gVbLWC12Qu8JheZpVRRz8749","name":"subagent","arguments":"{\"description\": \"Reply with CHILD_OK\", \"prompt\": \"Reply with exactly the word CHILD_OK and nothing else.\"}"}],"source":{"kind":"model","provider":"deepseek-official","model":"deepseek-v4-flash"},"id":"4da5cf2f-f9bd-4f1b-9c60-c9a56a7dae75"},"usage":{"inputTokens":2907,"outputTokens":142,"cacheReadTokens":0,"reasoningTokens":67}},"sourceEventSeqs":[9,10,11,12,13,14,15,16,17,18,19,20,21,22,23,24,25,26,27,28,29,30,31,32,33,34,35,36,37,38,39,40,41,42,43,44,45,46,47,48,49,50,51,52,53,54,55,56,57,58,59,60,61,62,63,64,65,66,67,68,69,70,71,72,73,74,75,76,77,78,79,80,81,82,83,84,85,86,87,88,89,90,91,92,93,94,95,96,97,98,99,100,101,102,103,104,105,106,107,108,109,110,111,112,113,114,115],"surfaceOp":"append"}
-{"type":"tool/call","seq":117,"time":1785730446697,"data":{"turn":1,"step":1,"callId":"call_00_gVbLWC12Qu8JheZpVRRz8749","name":"subagent","arguments":"{\"description\": \"Reply with CHILD_OK\", \"prompt\": \"Reply with exactly the word CHILD_OK and nothing else.\"}"}}
-{"type":"tool/result","seq":118,"time":1785730446730,"data":{"turn":1,"step":1,"message":{"source":{"kind":"tool","callId":"call_00_gVbLWC12Qu8JheZpVRRz8749"},"content":[{"type":"tool-result","toolCallId":"call_00_gVbLWC12Qu8JheZpVRRz8749","content":[{"type":"text","text":"CHILD_OK"}],"isError":false}],"role":"user","id":"8afba8c6-ad6a-4389-851b-77fc8f1fe5c9"}},"sourceEventSeqs":[117],"surfaceOp":"append"}
+{"type":"assistant/message","seq":116,"time":1785730446697,"data":{"turn":1,"step":1,"message":{"role":"assistant","content":[{"type":"reasoning","text":"The user wants me to:\n1. Use the subagent tool exactly once to delegate the task: \"Reply with exactly the word CHILD_OK and nothing else.\"\n2. After the subagent returns, reply with the single word PARENT_DONE and stop.\n3. Do not use the bash tool.\n\nLet me do this."},{"type":"tool-call","id":"call_00_gVbLWC12Qu8JheZpVRRz8749","name":"subagent","arguments":"{\"description\": \"Reply with CHILD_OK\", \"prompt\": \"Reply with exactly the word CHILD_OK and nothing else.\", \"run_in_background\":false}"}],"source":{"kind":"model","provider":"deepseek-official","model":"deepseek-v4-flash"},"id":"4da5cf2f-f9bd-4f1b-9c60-c9a56a7dae75"},"usage":{"inputTokens":2907,"outputTokens":142,"cacheReadTokens":0,"reasoningTokens":67}},"sourceEventSeqs":[9,10,11,12,13,14,15,16,17,18,19,20,21,22,23,24,25,26,27,28,29,30,31,32,33,34,35,36,37,38,39,40,41,42,43,44,45,46,47,48,49,50,51,52,53,54,55,56,57,58,59,60,61,62,63,64,65,66,67,68,69,70,71,72,73,74,75,76,77,78,79,80,81,82,83,84,85,86,87,88,89,90,91,92,93,94,95,96,97,98,99,100,101,102,103,104,105,106,107,108,109,110,111,112,113,114,115],"surfaceOp":"append"}
+{"type":"tool/call","seq":117,"time":1785730446697,"data":{"turn":1,"step":1,"callId":"call_00_gVbLWC12Qu8JheZpVRRz8749","name":"subagent","arguments":"{\"description\": \"Reply with CHILD_OK\", \"prompt\": \"Reply with exactly the word CHILD_OK and nothing else.\", \"run_in_background\":false}"}}
+{"type":"tool/result","seq":118,"time":1785730446730,"data":{"turn":1,"step":1,"message":{"source":{"kind":"tool","callId":"call_00_gVbLWC12Qu8JheZpVRRz8749"},"content":[{"type":"tool-result","toolCallId":"call_00_gVbLWC12Qu8JheZpVRRz8749","content":[{"type":"text","text":"CHILD_OK"}],"isError":false}],"role":"user","id":"2f4bb919-c9c3-4011-98d2-65c904dddcef"}},"sourceEventSeqs":[117],"surfaceOp":"append"}
 {"type":"step/end","seq":119,"time":1785730446730,"data":{"turn":1,"step":1}}
 {"type":"step/start","seq":120,"time":1785730446739,"data":{"turn":1,"step":2}}
 {"type":"assistant/chunk","seq":121,"time":1783352122524,"data":{"turn":1,"step":2,"chunk":{"type":"block-start","index":0,"blockType":"reasoning"}}}

examples/acp-agent/tests/snapshots/text-turn/system-prompt.expected.md

@@ -20,3 +20,5 @@ Use goal tools for one long-running completion objective in the current session.
 Use the workflow tool ONLY when the user explicitly asks for a workflow or for large multi-agent orchestration: you write a JavaScript script (the tool description documents the exact format) that fans work out across many subagents with phases and structured results. For one or two delegations, prefer plain subagent calls.
 
 Use the ralph tool ONLY when the direct human explicitly asks for a Ralph loop or fresh-agent iterative execution. Each Ralph round starts a fresh child with no conversation seed and uses the shared workspace as durable memory. Completion and blockers are worker reports, not independent evaluation. Use same-session goal tools for ordinary long-running objectives, and plain subagents or workflows for bounded delegation and fan-out.
+
+Use subagent in the background by default. Start independent delegations together in one assistant message and continue useful work while they run. Set `run_in_background: false` only when your next action depends on that subagent's result. When a background run settles, the runtime sends you a notice containing its outcome and any final assistant message.

examples/acp-agent/tests/snapshots/text-turn/tool-schemas.expected.json

@@ -231,7 +231,7 @@
     },
     {
       "name": "subagent",
-      "description": "Delegate a self-contained task to a subagent (a separate agent that works in its own context) and return its final result. Use this to offload focused, independent work — research, a scoped implementation, an analysis — so it does not consume this conversation's context. The subagent runs to completion and you receive only its final answer, not its intermediate steps. Give it a complete, standalone prompt: it does not see this conversation. Set `run_in_background: true` to start a background subagent that keeps its conversation: this call returns only its subagent id, and the subagent works on its own from there. You are told when it finishes, so never poll or wait on it; `send_message` sends it more work.",
+      "description": "Delegate a self-contained task to a subagent (a separate agent that works in its own context) to offload focused, independent work — research, a scoped implementation, an analysis — so it does not consume this conversation's context. The subagent returns its result, not its intermediate steps. Give it a complete, standalone prompt: it does not see this conversation. This tool runs in the background by default, immediately returns a durable subagent id, and keeps the child conversation available for later turns. When that run settles, the runtime sends the parent a notice containing its outcome and any final assistant message; `send_message` starts a later turn in the same child conversation. Set `run_in_background: false` only when your next action depends on receiving the result.",
       "parameters": {
         "type": "object",
         "properties": {
@@ -245,7 +245,7 @@
           },
           "run_in_background": {
             "type": "boolean",
-            "description": "Run as a background subagent that keeps its conversation and return only its subagent id. This call does not wait for it; you are told when it finishes. Send it more work with send_message."
+            "description": "Whether to run in the background and return a durable subagent id immediately. Defaults to true. Set false to wait for the result when your next action depends on it."
           }
         },
         "required": [
@@ -256,7 +256,7 @@
     },
     {
       "name": "subagent_fork",
-      "description": "Delegate a task to a subagent that inherits this conversation: a child agent seeded with all completed turns so far (it does not see the current in-flight turn), returning only its final result. Use this when the subtask builds on this conversation's context — a follow-up analysis, a review, a continuation — without consuming this conversation's context for the work itself. You receive only its final answer, not its intermediate steps.",
+      "description": "Delegate a task to a subagent that inherits this conversation: a child agent seeded with all completed turns so far (it does not see the current in-flight turn). Use this when the subtask builds on this conversation's context — a follow-up analysis, a review, a continuation — without consuming this conversation's context for the work itself. You receive its result, not its intermediate steps. This call waits for the subagent and returns its result.",
       "parameters": {
         "type": "object",
         "properties": {

examples/acp-agent/tests/snapshots/web-fetch/system-prompt.expected.md

@@ -22,3 +22,5 @@ Use goal tools for one long-running completion objective in the current session.
 Use the workflow tool ONLY when the user explicitly asks for a workflow or for large multi-agent orchestration: you write a JavaScript script (the tool description documents the exact format) that fans work out across many subagents with phases and structured results. For one or two delegations, prefer plain subagent calls.
 
 Use the ralph tool ONLY when the direct human explicitly asks for a Ralph loop or fresh-agent iterative execution. Each Ralph round starts a fresh child with no conversation seed and uses the shared workspace as durable memory. Completion and blockers are worker reports, not independent evaluation. Use same-session goal tools for ordinary long-running objectives, and plain subagents or workflows for bounded delegation and fan-out.
+
+Use subagent in the background by default. Start independent delegations together in one assistant message and continue useful work while they run. Set `run_in_background: false` only when your next action depends on that subagent's result. When a background run settles, the runtime sends you a notice containing its outcome and any final assistant message.

examples/acp-agent/tests/snapshots/web-fetch/tool-schemas.expected.json

@@ -231,7 +231,7 @@
     },
     {
       "name": "subagent",
-      "description": "Delegate a self-contained task to a subagent (a separate agent that works in its own context) and return its final result. Use this to offload focused, independent work — research, a scoped implementation, an analysis — so it does not consume this conversation's context. The subagent runs to completion and you receive only its final answer, not its intermediate steps. Give it a complete, standalone prompt: it does not see this conversation. Set `run_in_background: true` to start a background subagent that keeps its conversation: this call returns only its subagent id, and the subagent works on its own from there. You are told when it finishes, so never poll or wait on it; `send_message` sends it more work.",
+      "description": "Delegate a self-contained task to a subagent (a separate agent that works in its own context) to offload focused, independent work — research, a scoped implementation, an analysis — so it does not consume this conversation's context. The subagent returns its result, not its intermediate steps. Give it a complete, standalone prompt: it does not see this conversation. This tool runs in the background by default, immediately returns a durable subagent id, and keeps the child conversation available for later turns. When that run settles, the runtime sends the parent a notice containing its outcome and any final assistant message; `send_message` starts a later turn in the same child conversation. Set `run_in_background: false` only when your next action depends on receiving the result.",
       "parameters": {
         "type": "object",
         "properties": {
@@ -245,7 +245,7 @@
           },
           "run_in_background": {
             "type": "boolean",
-            "description": "Run as a background subagent that keeps its conversation and return only its subagent id. This call does not wait for it; you are told when it finishes. Send it more work with send_message."
+            "description": "Whether to run in the background and return a durable subagent id immediately. Defaults to true. Set false to wait for the result when your next action depends on it."
           }
         },
         "required": [
@@ -256,7 +256,7 @@
     },
     {
       "name": "subagent_fork",
-      "description": "Delegate a task to a subagent that inherits this conversation: a child agent seeded with all completed turns so far (it does not see the current in-flight turn), returning only its final result. Use this when the subtask builds on this conversation's context — a follow-up analysis, a review, a continuation — without consuming this conversation's context for the work itself. You receive only its final answer, not its intermediate steps.",
+      "description": "Delegate a task to a subagent that inherits this conversation: a child agent seeded with all completed turns so far (it does not see the current in-flight turn). Use this when the subtask builds on this conversation's context — a follow-up analysis, a review, a continuation — without consuming this conversation's context for the work itself. You receive its result, not its intermediate steps. This call waits for the subagent and returns its result.",
       "parameters": {
         "type": "object",
         "properties": {

examples/acp-agent/tests/snapshots/workspace-context/system-prompt.expected.md

@@ -20,3 +20,5 @@ Use goal tools for one long-running completion objective in the current session.
 Use the workflow tool ONLY when the user explicitly asks for a workflow or for large multi-agent orchestration: you write a JavaScript script (the tool description documents the exact format) that fans work out across many subagents with phases and structured results. For one or two delegations, prefer plain subagent calls.
 
 Use the ralph tool ONLY when the direct human explicitly asks for a Ralph loop or fresh-agent iterative execution. Each Ralph round starts a fresh child with no conversation seed and uses the shared workspace as durable memory. Completion and blockers are worker reports, not independent evaluation. Use same-session goal tools for ordinary long-running objectives, and plain subagents or workflows for bounded delegation and fan-out.
+
+Use subagent in the background by default. Start independent delegations together in one assistant message and continue useful work while they run. Set `run_in_background: false` only when your next action depends on that subagent's result. When a background run settles, the runtime sends you a notice containing its outcome and any final assistant message.

examples/headless-agent/tests/headless.snapshot.ts

@@ -816,7 +816,7 @@ describe('headless stream-json snapshots', () => {
         expect(calls.map(record => (record.data as JsonObject | undefined)?.name)).toEqual(['subagent'])
         const callArguments = (calls[0]?.data as JsonObject | undefined)?.arguments
         if (typeof callArguments !== 'string') throw new Error('subagent call did not persist its arguments')
-        expect(JSON.parse(callArguments)).toMatchObject({ run_in_background: true })
+        expect(JSON.parse(callArguments)).not.toHaveProperty('run_in_background')
 
         const notices = parentRecords.flatMap((record) => {
           if (record.type !== 'agent/inbox/spliced') return []

examples/headless-agent/tests/snapshots/advanced-toolchain/stream-json.expected.jsonl

@@ -29,12 +29,12 @@
 {"type":"session_event","sessionId":"{{sessionId}}","event":{"type":"step/end","seq":28,"time":0,"data":{"turn":1,"step":2}}}
 {"type":"session_event","sessionId":"{{sessionId}}","event":{"type":"step/start","seq":29,"time":0,"data":{"turn":1,"step":3}}}
 {"type":"session_event","sessionId":"{{sessionId}}","event":{"type":"assistant/chunk","seq":30,"time":0,"data":{"turn":1,"step":3,"chunk":{"type":"block-start","index":0,"blockType":"tool-call"}}}}
-{"type":"session_event","sessionId":"{{sessionId}}","event":{"type":"assistant/chunk","seq":31,"time":0,"data":{"turn":1,"step":3,"chunk":{"type":"tool-call-delta","index":0,"id":"advanced-direct-child","name":"subagent","argumentsDelta":"{\"description\":\"Check direct child\",\"prompt\":\"Reply with exactly DIRECT_CHILD_OK and nothing else.\"}"}}}}
-{"type":"session_event","sessionId":"{{sessionId}}","event":{"type":"assistant/chunk","seq":32,"time":0,"data":{"turn":1,"step":3,"chunk":{"type":"block-end","index":0,"block":{"type":"tool-call","id":"advanced-direct-child","name":"subagent","arguments":"{\"description\":\"Check direct child\",\"prompt\":\"Reply with exactly DIRECT_CHILD_OK and nothing else.\"}"}}}}}
+{"type":"session_event","sessionId":"{{sessionId}}","event":{"type":"assistant/chunk","seq":31,"time":0,"data":{"turn":1,"step":3,"chunk":{"type":"tool-call-delta","index":0,"id":"advanced-direct-child","name":"subagent","argumentsDelta":"{\"description\":\"Check direct child\",\"prompt\":\"Reply with exactly DIRECT_CHILD_OK and nothing else.\",\"run_in_background\":false}"}}}}
+{"type":"session_event","sessionId":"{{sessionId}}","event":{"type":"assistant/chunk","seq":32,"time":0,"data":{"turn":1,"step":3,"chunk":{"type":"block-end","index":0,"block":{"type":"tool-call","id":"advanced-direct-child","name":"subagent","arguments":"{\"description\":\"Check direct child\",\"prompt\":\"Reply with exactly DIRECT_CHILD_OK and nothing else.\",\"run_in_background\":false}"}}}}}
 {"type":"session_event","sessionId":"{{sessionId}}","event":{"type":"assistant/chunk","seq":33,"time":0,"data":{"turn":1,"step":3,"chunk":{"type":"usage","usage":{"inputTokens":3,"outputTokens":3}}}}}
 {"type":"session_event","sessionId":"{{sessionId}}","event":{"type":"assistant/chunk","seq":34,"time":0,"data":{"turn":1,"step":3,"chunk":{"type":"finish","reason":{"kind":"tool-calls"}}}}}
-{"type":"session_event","sessionId":"{{sessionId}}","event":{"type":"assistant/message","seq":35,"time":0,"data":{"turn":1,"step":3,"message":{"role":"assistant","content":[{"type":"tool-call","id":"advanced-direct-child","name":"subagent","arguments":"{\"description\":\"Check direct child\",\"prompt\":\"Reply with exactly DIRECT_CHILD_OK and nothing else.\"}"}],"source":{"kind":"model","provider":"deepseek-official","model":"deepseek-v4-flash"},"id":"{{sessionId}}"},"usage":{"inputTokens":3,"outputTokens":3}},"sourceEventSeqs":[30,31,32,33,34],"surfaceOp":"append"}}
-{"type":"session_event","sessionId":"{{sessionId}}","event":{"type":"tool/call","seq":36,"time":0,"data":{"turn":1,"step":3,"callId":"advanced-direct-child","name":"subagent","arguments":"{\"description\":\"Check direct child\",\"prompt\":\"Reply with exactly DIRECT_CHILD_OK and nothing else.\"}"}}}
+{"type":"session_event","sessionId":"{{sessionId}}","event":{"type":"assistant/message","seq":35,"time":0,"data":{"turn":1,"step":3,"message":{"role":"assistant","content":[{"type":"tool-call","id":"advanced-direct-child","name":"subagent","arguments":"{\"description\":\"Check direct child\",\"prompt\":\"Reply with exactly DIRECT_CHILD_OK and nothing else.\",\"run_in_background\":false}"}],"source":{"kind":"model","provider":"deepseek-official","model":"deepseek-v4-flash"},"id":"{{sessionId}}"},"usage":{"inputTokens":3,"outputTokens":3}},"sourceEventSeqs":[30,31,32,33,34],"surfaceOp":"append"}}
+{"type":"session_event","sessionId":"{{sessionId}}","event":{"type":"tool/call","seq":36,"time":0,"data":{"turn":1,"step":3,"callId":"advanced-direct-child","name":"subagent","arguments":"{\"description\":\"Check direct child\",\"prompt\":\"Reply with exactly DIRECT_CHILD_OK and nothing else.\",\"run_in_background\":false}"}}}
 {"type":"session_event","sessionId":"{{sessionId}}","event":{"type":"tool/result","seq":37,"time":0,"data":{"turn":1,"step":3,"message":{"source":{"kind":"tool","callId":"advanced-direct-child"},"content":[{"type":"tool-result","toolCallId":"advanced-direct-child","content":[{"type":"text","text":"DIRECT_CHILD_OK"}],"isError":false}],"role":"user","id":"{{sessionId}}"}},"sourceEventSeqs":[36],"surfaceOp":"append"}}
 {"type":"session_event","sessionId":"{{sessionId}}","event":{"type":"step/end","seq":38,"time":0,"data":{"turn":1,"step":3}}}
 {"type":"session_event","sessionId":"{{sessionId}}","event":{"type":"step/start","seq":39,"time":0,"data":{"turn":1,"step":4}}}

examples/headless-agent/tests/snapshots/subagent-settlement/parent.override.json

@@ -3,8 +3,8 @@
     "kind": "chunks",
     "chunks": [
       { "type": "block-start", "index": 0, "blockType": "tool-call" },
-      { "type": "tool-call-delta", "index": 0, "id": "start-child", "name": "subagent", "argumentsDelta": "{\"description\":\"Return child result\",\"prompt\":\"Reply with exactly CHILD_RESULT and nothing else. Do not call report.\",\"run_in_background\":true}" },
-      { "type": "block-end", "index": 0, "block": { "type": "tool-call", "id": "start-child", "name": "subagent", "arguments": "{\"description\":\"Return child result\",\"prompt\":\"Reply with exactly CHILD_RESULT and nothing else. Do not call report.\",\"run_in_background\":true}" } },
+      { "type": "tool-call-delta", "index": 0, "id": "start-child", "name": "subagent", "argumentsDelta": "{\"description\":\"Return child result\",\"prompt\":\"Reply with exactly CHILD_RESULT and nothing else. Do not call report.\"}" },
+      { "type": "block-end", "index": 0, "block": { "type": "tool-call", "id": "start-child", "name": "subagent", "arguments": "{\"description\":\"Return child result\",\"prompt\":\"Reply with exactly CHILD_RESULT and nothing else. Do not call report.\"}" } },
       { "type": "usage", "usage": { "inputTokens": 10, "outputTokens": 5 } },
       { "type": "finish", "reason": { "kind": "tool-calls" } }
     ]

examples/headless-agent/tests/snapshots/subagent-settlement/stream-json.expected.jsonl

@@ -7,12 +7,12 @@
 {"type":"session_event","sessionId":"{{sessionId}}","event":{"type":"request/header","seq":6,"time":0,"data":{"header":{"config":{"provider":"deepseek-official","model":"deepseek-v4-flash"},"system":"{{system}}","tools":"{{tools}}"},"reason":"initial"}}}
 {"type":"session_event","sessionId":"{{sessionId}}","event":{"type":"request/context","seq":7,"time":0,"data":{"provider":"deepseek-official","model":"deepseek-v4-flash"}}}
 {"type":"session_event","sessionId":"{{sessionId}}","event":{"type":"assistant/chunk","seq":8,"time":0,"data":{"turn":1,"step":1,"chunk":{"type":"block-start","index":0,"blockType":"tool-call"}}}}
-{"type":"session_event","sessionId":"{{sessionId}}","event":{"type":"assistant/chunk","seq":9,"time":0,"data":{"turn":1,"step":1,"chunk":{"type":"tool-call-delta","index":0,"id":"start-child","name":"subagent","argumentsDelta":"{\"description\":\"Return child result\",\"prompt\":\"Reply with exactly CHILD_RESULT and nothing else. Do not call report.\",\"run_in_background\":true}"}}}}
-{"type":"session_event","sessionId":"{{sessionId}}","event":{"type":"assistant/chunk","seq":10,"time":0,"data":{"turn":1,"step":1,"chunk":{"type":"block-end","index":0,"block":{"type":"tool-call","id":"start-child","name":"subagent","arguments":"{\"description\":\"Return child result\",\"prompt\":\"Reply with exactly CHILD_RESULT and nothing else. Do not call report.\",\"run_in_background\":true}"}}}}}
+{"type":"session_event","sessionId":"{{sessionId}}","event":{"type":"assistant/chunk","seq":9,"time":0,"data":{"turn":1,"step":1,"chunk":{"type":"tool-call-delta","index":0,"id":"start-child","name":"subagent","argumentsDelta":"{\"description\":\"Return child result\",\"prompt\":\"Reply with exactly CHILD_RESULT and nothing else. Do not call report.\"}"}}}}
+{"type":"session_event","sessionId":"{{sessionId}}","event":{"type":"assistant/chunk","seq":10,"time":0,"data":{"turn":1,"step":1,"chunk":{"type":"block-end","index":0,"block":{"type":"tool-call","id":"start-child","name":"subagent","arguments":"{\"description\":\"Return child result\",\"prompt\":\"Reply with exactly CHILD_RESULT and nothing else. Do not call report.\"}"}}}}}
 {"type":"session_event","sessionId":"{{sessionId}}","event":{"type":"assistant/chunk","seq":11,"time":0,"data":{"turn":1,"step":1,"chunk":{"type":"usage","usage":{"inputTokens":10,"outputTokens":5}}}}}
 {"type":"session_event","sessionId":"{{sessionId}}","event":{"type":"assistant/chunk","seq":12,"time":0,"data":{"turn":1,"step":1,"chunk":{"type":"finish","reason":{"kind":"tool-calls"}}}}}
-{"type":"session_event","sessionId":"{{sessionId}}","event":{"type":"assistant/message","seq":13,"time":0,"data":{"turn":1,"step":1,"message":{"role":"assistant","content":[{"type":"tool-call","id":"start-child","name":"subagent","arguments":"{\"description\":\"Return child result\",\"prompt\":\"Reply with exactly CHILD_RESULT and nothing else. Do not call report.\",\"run_in_background\":true}"}],"source":{"kind":"model","provider":"deepseek-official","model":"deepseek-v4-flash"},"id":"{{sessionId}}"},"usage":{"inputTokens":10,"outputTokens":5}},"sourceEventSeqs":[8,9,10,11,12],"surfaceOp":"append"}}
-{"type":"session_event","sessionId":"{{sessionId}}","event":{"type":"tool/call","seq":14,"time":0,"data":{"turn":1,"step":1,"callId":"start-child","name":"subagent","arguments":"{\"description\":\"Return child result\",\"prompt\":\"Reply with exactly CHILD_RESULT and nothing else. Do not call report.\",\"run_in_background\":true}"}}}
+{"type":"session_event","sessionId":"{{sessionId}}","event":{"type":"assistant/message","seq":13,"time":0,"data":{"turn":1,"step":1,"message":{"role":"assistant","content":[{"type":"tool-call","id":"start-child","name":"subagent","arguments":"{\"description\":\"Return child result\",\"prompt\":\"Reply with exactly CHILD_RESULT and nothing else. Do not call report.\"}"}],"source":{"kind":"model","provider":"deepseek-official","model":"deepseek-v4-flash"},"id":"{{sessionId}}"},"usage":{"inputTokens":10,"outputTokens":5}},"sourceEventSeqs":[8,9,10,11,12],"surfaceOp":"append"}}
+{"type":"session_event","sessionId":"{{sessionId}}","event":{"type":"tool/call","seq":14,"time":0,"data":{"turn":1,"step":1,"callId":"start-child","name":"subagent","arguments":"{\"description\":\"Return child result\",\"prompt\":\"Reply with exactly CHILD_RESULT and nothing else. Do not call report.\"}"}}}
 {"type":"session_event","sessionId":"{{sessionId}}","event":{"type":"tool/result","seq":15,"time":0,"data":{"turn":1,"step":1,"message":{"source":{"kind":"tool","callId":"start-child"},"content":[{"type":"tool-result","toolCallId":"start-child","content":[{"type":"text","text":"started subagent {{sessionId}}"}],"isError":false}],"role":"user","id":"{{sessionId}}"}},"sourceEventSeqs":[14],"surfaceOp":"append"}}
 {"type":"session_event","sessionId":"{{sessionId}}","event":{"type":"step/end","seq":16,"time":0,"data":{"turn":1,"step":1}}}
 {"type":"session_event","sessionId":"{{sessionId}}","event":{"type":"agent/inbox/spliced","seq":17,"time":0,"data":{"target":"next-step","start":0,"inserted":[{"content":[{"type":"text","text":"Background subagent {{sessionId}} finished and will do no further work unless you send it more."},{"type":"text","text":"Its closing message:"},{"type":"text","text":"CHILD_RESULT"}],"source":{"kind":"subagent-settled","form":"notice","summary":"Background subagent {{sessionId}} finished and will do no further work unless you send it more.","senderSessionId":"{{sessionId}}"},"role":"user","id":"{{sessionId}}"}]}}}

packages/subagent/tool-subagent/README.i18n.yaml

@@ -2,5 +2,5 @@
 # side as of the last confirmed-consistent state. Both languages carry equal authority;
 # after editing either side, bring the other along and re-record with:
 #   pnpm run verify-translation-pairing --write packages/subagent/tool-subagent/README.md
-README.md: d4c472d54f87d6006aef96079050cf14885ed8fb
-README.zh.md: 36f79ac879067dc74fcc6b96122088bb68d53321
+README.md: cc872f3decc4c85f26bd997293c8dc4140eb221c
+README.zh.md: f7616dc677d10c141b1be606dae36d7dc7bb23ac

packages/subagent/tool-subagent/README.md

@@ -10,7 +10,7 @@ Each plugin instance binds one `provider` to one `toolName`; the model receives
 
 A foreground call passes the execution signal through startup and execution, awaits `run.result`, and always awaits `run.dispose()` before returning. Only `completed` returns the canonical `{ kind: 'foreground', runId, output: JsonValue[] }`, rendered as the same final text; abort, refusal, token limit, and other failures become errored tool results whose message appends the child's preserved partial text (the `SubagentResult.output` selection) after the stop-reason headline, so a truncated answer is never reported as success yet never silently lost. If result collection and disposal both reject, the errored result preserves both diagnostics.
 
-With `run_in_background: true`, `backgroundMode` selects the route. `one-shot` registers a plain parent-owned Task and returns canonical `{ kind: 'background', taskId }`, rendered as `started background subagent task <id>`, even when the provider supports continuable children; generic task tools own its later status, collection, cancellation, and notices. `continuable` requires a provider with the `prepareContinuable` capability, calls `ctx.subagents.startContinuable()`, and returns `{ kind: 'continuable', subagentId }`, rendered as `started subagent <childId>`. The continuable route resolves at inbox acceptance: the child owns its own turns from there, so this call neither waits for nor collects a result. The child's transcript by that id remains the source of its detailed output, and the optional global `send_message` tool sends it more work. The parent is not left guessing when to look, though: the continuation service delivers one settlement notice to it whenever a continuable child's Activation ends, which is why the schema tells the model it will be told and must not poll. Starting continuable work does not require `send_message` to be loaded. See the [background subagent Agent Note](../../../.agents/notes/implemented/feature/2026-07-08-background-subagent-tasks.md), the [continuable subagents Agent Note](../../../.agents/notes/implemented/feature/2026-07-28-continuable-subagent-conversations.md), and the [merged-service Agent Note](../../../.agents/notes/implemented/simplification/2026-07-26-merge-subagent-control-service.md).
+`backgroundMode` selects both the background route and the omitted `run_in_background` default. `one-shot` waits in the foreground by default; an explicit `true` registers a plain parent-owned Task and returns canonical `{ kind: 'background', taskId }`, rendered as `started background subagent task <id>`, even when the provider supports continuable children. Generic task tools own its later status, collection, cancellation, and notices. `continuable` runs in the background when the argument is omitted or `true`; an explicit `false` waits for the result in the foreground. Its background route requires a provider with the `prepareContinuable` capability, calls `ctx.subagents.startContinuable()`, and returns `{ kind: 'continuable', subagentId }`, rendered as `started subagent <childId>`. The route resolves at inbox acceptance: the child owns its own turns from there, so this call neither waits for nor collects a result. The child's transcript by that id remains the source of its detailed output, and the optional global `send_message` tool sends it more work. The continuation service delivers one settlement notice whenever the child's Activation ends, containing its outcome and any final assistant message independently of `report`. Starting continuable work does not require `send_message` to be loaded. See the [background subagent Agent Note](../../../.agents/notes/implemented/feature/2026-07-08-background-subagent-tasks.md), the [continuable subagents Agent Note](../../../.agents/notes/implemented/feature/2026-07-28-continuable-subagent-conversations.md), and the [background-first delegation Agent Note](../../../.agents/notes/implemented/feature/2026-08-11-background-first-continuable-delegation.md).
 
 `toolFilter` changes the child's global tool layer but is not a parent-derived authority ceiling. See the [agent-scope security non-goal](../../../.agents/notes/implemented/architecture/2026-07-08-agent-scope-contexts.md#security-and-authority-are-non-goals).
 
@@ -21,7 +21,7 @@ With `run_in_background: true`, `backgroundMode` selects the route. `one-shot` r
 | `provider` (required) | Provider name (`spawn`, `fork`, `acp`, ...). |
 | `toolName` | Model-facing name, default `subagent`; distinct for every loaded instance. |
 | `enableRunInBackground` | Exposes background mode, default `true`; disabling also rejects forced background calls. |
-| `backgroundMode` | Background lifecycle policy, default `one-shot`. `continuable` requires the provider's `prepareContinuable` capability and returns a durable child id; it does not require the follow-up tool. |
+| `backgroundMode` | Background lifecycle policy, default `one-shot`. `one-shot` defaults calls to foreground; `continuable` defaults them to background, requires the provider's `prepareContinuable` capability, and returns a durable child id without requiring the follow-up tool. |
 | `agentOptions` | Provider-specific child `provider`, `model`, and positive `maxTokens`; the in-process provider treats explicit values as overrides of inherited parent options. |
 | `persona` | Per-child persona; requires provider `persona` capability. |
 | `toolFilter` | Per-child global-tool restriction; requires `toolFilter` capability. |
@@ -37,11 +37,11 @@ Foreground and background calls are concurrency-safe: sibling delegations in one
 
 #### What the model sees
 
-The generated default [`subagent` schema](../../../docs/tool-catalog.md#deepseek-aidsh-tool-subagent) under this instance's configured name while its provider exists. Provider context inheritance changes the tool and prompt descriptions; enabled background mode adds `run_in_background`, and continuable mode describes starting a background subagent that keeps its conversation, returns its subagent id, and reports its own completion — so the model is told never to poll or wait on it — while one-shot mode describes a background task id collected with `task_output` and stopped with `task_kill`.
+The generated default [`subagent` schema](../../../docs/tool-catalog.md#deepseek-aidsh-tool-subagent) under this instance's configured name while its provider exists. Provider context inheritance changes the tool and prompt descriptions. Enabled background mode adds `run_in_background`: continuable mode documents its `true` default, runtime settlement notice, and explicit foreground override, while one-shot mode documents its `false` default and the task id collected with `task_output` or stopped with `task_kill`. While the tool is visible in an assembly's scope, a `tool:<toolName>` system-prompt section tells the model to start independent continuable delegations together, keep working while they run, and choose foreground only when its next action depends on the result; a tool restriction removes both its schema and this guidance.
 
 #### Token effect
 
-Fixed schema cost per parent request; each provider instance adds one schema.
+Fixed schema cost per parent request; each provider instance adds one schema, and each continuable instance adds one short system-prompt section.
 
 #### KV Cache effect
 
@@ -77,6 +77,6 @@ Append-only; newly visible content follows the reusable request prefix and does
 
 ## Known Limitations and Deferred Work
 
-- **Background runs expose no result through this tool** — a one-shot task's final output is collected through the generic task surface, and a continuable child's output stays in its own session, read by its subagent id. The settlement notice states how that child ended and carries its closing message, but it is not this call's return value and cannot be awaited here.
-- **Duplicate names across waiting instances are detected late** (`TODO(subagent-dup-toolname)`) — preventing provider-registration rollback requires a registry of intended names.
+- **Background runs expose no result through this tool** — a one-shot task's final output is collected through the generic task surface, and a continuable child's output stays in its own session, read by its subagent id. The settlement notice states how that child ended and carries any final assistant message, but it is not this call's return value and cannot be awaited here.
+- **Duplicate names across waiting one-shot instances are detected late** (`TODO(subagent-dup-toolname)`) — continuable instances reserve their prompt-section name during plugin application, but preventing provider-registration rollback for waiting one-shot instances requires a registry of intended names.
 - **Child policy is fixed per instance** — another model, persona, tool filter, or depth cap requires another distinctly named tool.

packages/subagent/tool-subagent/README.zh.md

@@ -10,7 +10,7 @@
 
 前台调用会让执行信号贯穿启动和执行，等待 `run.result`，并且在返回前总会等待 `run.dispose()`。只有 `completed` 会返回规范值 `{ kind: 'foreground', runId, output: JsonValue[] }`，并渲染为相同的最终文本；中止、拒绝、token 上限和其他失败都会变成出错的工具结果，其消息在终止原因标题之后附带子代理保留下来的部分文本（即 `SubagentResult.output` 的选取结果）——被截断的回答不会被报告为成功，也绝不会被悄悄丢弃。如果结果收集与 dispose（资源释放）都 reject，出错的结果会保留两项诊断信息。
 
-设置 `run_in_background: true` 后，`backgroundMode` 会选择路由。`one-shot` 会注册一个归父级所有的普通 Task，并返回规范值 `{ kind: 'background', taskId }`，渲染为 `started background subagent task <id>`，即使提供方支持可继续子 agent 也不例外；通用 Task 工具负责其后续状态、收集、取消和通知。`continuable` 要求提供方具备 `prepareContinuable` 能力，调用 `ctx.subagents.startContinuable()`，并返回 `{ kind: 'continuable', subagentId }`，渲染为 `started subagent <childId>`。可继续路由在 inbox 接受时结算：子 agent 自此拥有自己的轮次，因此该调用既不等待也不收集结果。通过该 id 查看其 transcript（文本记录）仍是其详细输出的来源，可选的全局 `send_message` 工具则向其发送更多工作。不过父级无需猜测何时查看：每当可继续子 agent 的 Activation 结束，继续执行服务都会向父级投递一条结算通知——正因如此，schema 才告诉模型它会被通知，且不得轮询。启动可继续工作不要求加载 `send_message`。见 [后台 subagent Agent Note](../../../.agents/notes/implemented/feature/2026-07-08-background-subagent-tasks.md)、[可继续的 subagent Agent Note](../../../.agents/notes/implemented/feature/2026-07-28-continuable-subagent-conversations.md)和[服务合并 Agent Note](../../../.agents/notes/implemented/simplification/2026-07-26-merge-subagent-control-service.md)。
+`backgroundMode` 同时选择后台路由与省略 `run_in_background` 时的默认行为。`one-shot` 默认在前台等待；显式传入 `true` 时，它会注册一个归父级所有的普通 Task，并返回规范值 `{ kind: 'background', taskId }`，渲染为 `started background subagent task <id>`，即使提供方支持可继续子 agent 也不例外。通用 Task 工具负责其后续状态、收集、取消和通知。`continuable` 在参数省略或为 `true` 时于后台运行；显式传入 `false` 时则在前台等待结果。其后台路由要求提供方具备 `prepareContinuable` 能力，调用 `ctx.subagents.startContinuable()`，并返回 `{ kind: 'continuable', subagentId }`，渲染为 `started subagent <childId>`。该路由在 inbox 接受时结算：子 agent 自此拥有自己的轮次，因此该调用既不等待也不收集结果。通过该 id 查看其 transcript（文本记录）仍是其详细输出的来源，可选的全局 `send_message` 工具则向其发送更多工作。每当子 agent 的 Activation 结束，继续执行服务都会投递一条结算通知，其中包含结束结果及可能存在的最终 assistant 消息，且这项投递不依赖 `report`。启动可继续工作不要求加载 `send_message`。见[后台 subagent Agent Note](../../../.agents/notes/implemented/feature/2026-07-08-background-subagent-tasks.md)、[可继续的 subagent Agent Note](../../../.agents/notes/implemented/feature/2026-07-28-continuable-subagent-conversations.md)和[后台优先委派 Agent Note](../../../.agents/notes/implemented/feature/2026-08-11-background-first-continuable-delegation.md)。
 
 `toolFilter` 会改变子 agent 的全局工具层，但不是从父级派生的权限上限。见 [agent 作用域的安全非目标](../../../.agents/notes/implemented/architecture/2026-07-08-agent-scope-contexts.md#security-and-authority-are-non-goals)。
 
@@ -21,7 +21,7 @@
 | `provider`（必填） | 提供方名称（`spawn`、`fork`、`acp` 等）。 |
 | `toolName` | 面向模型的名称，默认 `subagent`；每个已加载实例必须不同。 |
 | `enableRunInBackground` | 公开后台模式，默认 `true`；禁用时也会拒绝强制后台调用。 |
-| `backgroundMode` | 后台生命周期策略，默认 `one-shot`。`continuable` 要求提供方具备 `prepareContinuable` 能力并返回持久化子 agent ID；它不要求加载后续消息工具。 |
+| `backgroundMode` | 后台生命周期策略，默认 `one-shot`。`one-shot` 默认前台调用；`continuable` 默认后台调用，要求提供方具备 `prepareContinuable` 能力，并返回持久化子 agent ID，且不要求加载后续消息工具。 |
 | `agentOptions` | 传给具体提供方的子 agent `provider`、`model` 和正整数 `maxTokens`；进程内提供方会用显式值覆盖继承的父级选项。 |
 | `persona` | 每个子 agent 独立的 persona；要求提供方具备 `persona` 能力。 |
 | `toolFilter` | 每个子 agent 独立的全局工具限制；要求提供方具备 `toolFilter` 能力。 |
@@ -37,11 +37,11 @@
 
 #### 模型看到的内容
 
-当提供方存在时，以当前实例配置的名称公开已生成的默认 [`subagent` schema](../../../docs/tool-catalog.md#deepseek-aidsh-tool-subagent)。提供方是否继承上下文会改变工具描述和提示词描述；启用后台模式会添加 `run_in_background`，可继续模式描述为启动一个保留其对话、返回子 agent id 并会自行报告完成的后台子 agent——因此模型被告知绝不要轮询或等待它——而一次性模式描述为返回一个用 `task_output` 收集、用 `task_kill` 停止的后台任务 id。
+当提供方存在时，以当前实例配置的名称公开已生成的默认 [`subagent` schema](../../../docs/tool-catalog.md#deepseek-aidsh-tool-subagent)。提供方是否继承上下文会改变工具描述和提示词描述。启用后台模式会添加 `run_in_background`：可继续模式会记录其默认值为 `true`、运行时结算通知与显式前台覆盖；一次性模式会记录其默认值为 `false`，以及用 `task_output` 收集或用 `task_kill` 停止的 task id。当工具在本次组装的作用域中可见时，一个 `tool:<toolName>` 系统提示词 section 会指示模型同时启动相互独立的可继续委派、在它们运行时继续工作，并且仅当下一步动作依赖结果时选择前台；工具限制会同时移除其 schema 和这段指引。
 
 #### Token 影响
 
-每个父级请求都会产生固定的 schema token 开销；每个提供方实例增加一个 schema。
+每个父级请求都会产生固定的 schema token 开销；每个提供方实例增加一个 schema，每个可继续实例还会增加一个简短的系统提示词 section。
 
 #### KV Cache 影响
 
@@ -77,6 +77,6 @@
 
 ## 已知限制与暂缓事项
 
-- **后台运行不通过本工具公开结果**：一次性任务的最终输出通过通用 Task 接口收集，可继续子 agent 的输出留在其自身会话中，按其 subagent id 读取。结算通知会说明该子 agent 如何结束并携带其收尾消息，但它不是本次调用的返回值，也无法在此等待。
-- **等待中实例的重复名称发现较晚**（`TODO(subagent-dup-toolname)`）：若要阻止提供方注册回滚，需要一份预期名称注册表。
+- **后台运行不通过本工具公开结果**：一次性任务的最终输出通过通用 Task 接口收集，可继续子 agent 的输出留在其自身会话中，按其 subagent id 读取。结算通知会说明该子 agent 如何结束，并携带可能存在的最终 assistant 消息，但它不是本次调用的返回值，也无法在此等待。
+- **等待中的一次性实例较晚才发现重复名称**（`TODO(subagent-dup-toolname)`）：可继续实例会在插件应用期间预留提示词 section 名称，但若要阻止等待中的一次性实例回滚提供方注册，仍需要一份预期名称注册表。
 - **每个实例的子 agent 策略固定**：其他模型、persona、工具过滤器或深度上限都需要另一个名称不同的工具。

packages/subagent/tool-subagent/package.json

@@ -36,6 +36,7 @@
     "@deepseek-ai/dsh-invariants": "workspace:^",
     "@deepseek-ai/dsh-llm": "workspace:^",
     "@deepseek-ai/dsh-subagent": "workspace:^",
+    "@deepseek-ai/dsh-system-prompt": "workspace:^",
     "@deepseek-ai/dsh-tasks": "workspace:^",
     "@deepseek-ai/dsh-tools": "workspace:^",
     "@deepseek-ai/cordis": "workspace:^"

packages/subagent/tool-subagent/src/index.ts

@@ -17,9 +17,13 @@ import type { JsonValue } from '@deepseek-ai/dsh-session'
 import { assertSubagentMaxDepth, settleRun } from '@deepseek-ai/dsh-subagent'
 import type { SubagentProvider, SubagentResult, SubagentRun } from '@deepseek-ai/dsh-subagent'
 import type { TaskOutcome } from '@deepseek-ai/dsh-tasks'
+import type {} from '@deepseek-ai/dsh-system-prompt'
 
 export const name = 'tool-subagent'
-export const inject = ['tools', 'subagents']
+export const inject = ['tools', 'subagents', 'systemPrompt']
+
+/** Prompt order after bounded delegation policy and before child reporting. */
+const SUBAGENT_SECTION_ORDER = 116.5
 
 /** Config: which registered provider this tool delegates to, plus child defaults. */
 export interface Config {
@@ -36,9 +40,10 @@ export interface Config {
    */
   enableRunInBackground?: boolean
   /**
-   * Background execution policy (default `one-shot`). `continuable` requires a
-   * provider with the `prepareContinuable` capability and returns the durable
-   * child id; follow-up adapters remain independently optional.
+   * Background execution policy (default `one-shot`). `one-shot` defaults calls
+   * to foreground; `continuable` defaults them to background, requires a provider
+   * with the `prepareContinuable` capability, and returns the durable child id.
+   * Follow-up adapters remain independently optional.
    */
   backgroundMode?: 'one-shot' | 'continuable'
   /**
@@ -208,10 +213,10 @@ function providerWording(inheritsConversation: boolean): { description: string;
     return {
       description:
         'Delegate a task to a subagent that inherits this conversation: a child agent seeded with all '
-        + 'completed turns so far (it does not see the current in-flight turn), returning only its final '
-        + 'result. Use this when the subtask builds on this conversation\'s context — a follow-up analysis, '
+        + 'completed turns so far (it does not see the current in-flight turn). Use this when the subtask '
+        + 'builds on this conversation\'s context — a follow-up analysis, '
         + 'a review, a continuation — without consuming this conversation\'s context for the work itself. '
-        + 'You receive only its final answer, not its intermediate steps.',
+        + 'You receive its result, not its intermediate steps.',
       promptDescription:
         'The task for the subagent. It already sees this conversation\'s completed turns, so build on them '
         + 'freely and state only what is new.',
@@ -220,9 +225,9 @@ function providerWording(inheritsConversation: boolean): { description: string;
   return {
     description:
       'Delegate a self-contained task to a subagent (a separate agent that works in its own context) '
-      + 'and return its final result. Use this to offload focused, independent work — research, a scoped '
+      + 'to offload focused, independent work — research, a scoped '
       + 'implementation, an analysis — so it does not consume this conversation\'s context. The subagent '
-      + 'runs to completion and you receive only its final answer, not its intermediate steps. Give it a '
+      + 'returns its result, not its intermediate steps. Give it a '
       + 'complete, standalone prompt: it does not see this conversation.',
     promptDescription:
       'The complete, self-contained task for the subagent. It does not share this '
@@ -230,6 +235,35 @@ function providerWording(inheritsConversation: boolean): { description: string;
   }
 }
 
+interface DelegationRunRequest {
+  readonly run_in_background?: boolean
+}
+
+interface DelegationRunSpec {
+  readonly runInBackground: boolean
+}
+
+/** Resolve the model's optional scheduling request into one execution route. */
+function resolveDelegationRun(
+  request: DelegationRunRequest,
+  options: { readonly backgroundEnabled: boolean; readonly continuable: boolean },
+): DelegationRunSpec {
+  if (!options.backgroundEnabled) {
+    // The validator permits undeclared keys, so schema omission also needs
+    // execution-time enforcement.
+    if (request.run_in_background === true) {
+      throw new Error('run_in_background is disabled for this tool instance (enableRunInBackground: false)')
+    }
+    return { runInBackground: false }
+  }
+  return {
+    // Continuable work is independently scheduled unless the caller explicitly
+    // needs the result before its next action. One-shot policy keeps its existing
+    // foreground default because its background result requires Task collection.
+    runInBackground: request.run_in_background ?? options.continuable,
+  }
+}
+
 export function apply(ctx: Context, config: Config): void {
   // Direct apply() bypasses Schemastery's numeric constraints. A direct-apply
   // omission stays capless (the schema default only runs through the loader).
@@ -238,6 +272,9 @@ export function apply(ctx: Context, config: Config): void {
   if (config.toolFilter !== undefined && config.toolFilter.allow === undefined && config.toolFilter.deny === undefined) {
     throw new Error('tool-subagent: `toolFilter` is configured but names neither `allow` nor `deny` — remove the key or fill the filter')
   }
+  const backgroundEnabled = config.enableRunInBackground !== false
+  const continuable = (config.backgroundMode ?? 'one-shot') === 'continuable'
+  const toolName = config.toolName ?? 'subagent'
   // Mirror provider lifecycle because sibling load order and HMR replacement
   // can change provider availability while this fiber remains active.
   let disposeTool: (() => void) | undefined
@@ -252,25 +289,21 @@ export function apply(ctx: Context, config: Config): void {
       )
     }
     const wording = providerWording(provider.inheritsParentContext)
-    const backgroundEnabled = config.enableRunInBackground !== false
-    const continuable = (config.backgroundMode ?? 'one-shot') === 'continuable'
     if (continuable && provider.prepareContinuable === undefined) {
       throw new Error(
         `tool-subagent: provider "${provider.name}" does not support \`backgroundMode: continuable\``,
       )
     }
     disposeTool = ctx.tools.register(defineTool({
-      name: config.toolName ?? 'subagent',
+      name: toolName,
       description: wording.description + (backgroundEnabled
         // The completion notice is the continuation service's own behavior, not
         // a separately installed capability, so this promise holds whenever the
         // continuable background path is reachable at all.
         ? continuable
-          ? ' Set `run_in_background: true` to start a background subagent that keeps its conversation:'
-          + ' this call returns only its subagent id, and the subagent works on its own from there. You'
-          + ' are told when it finishes, so never poll or wait on it; `send_message` sends it more work.'
-          : ' Set `run_in_background: true` to return a task id; collect with `task_output` and stop with `task_kill`.'
-        : ''),
+          ? ' This tool runs in the background by default, immediately returns a durable subagent id, and keeps the child conversation available for later turns. When that run settles, the runtime sends the parent a notice containing its outcome and any final assistant message; `send_message` starts a later turn in the same child conversation. Set `run_in_background: false` only when your next action depends on receiving the result.'
+          : ' This call waits for the result by default. Set `run_in_background: true` to return a task id; collect with `task_output` and stop with `task_kill`.'
+        : ' This call waits for the subagent and returns its result.'),
       parameters: {
         description: {
           type: 'string',
@@ -286,9 +319,8 @@ export function apply(ctx: Context, config: Config): void {
           run_in_background: {
             type: 'boolean' as const,
             description: continuable
-              ? 'Run as a background subagent that keeps its conversation and return only its subagent id. '
-              + 'This call does not wait for it; you are told when it finishes. Send it more work with send_message.'
-              : 'Run as a background task and return its id; collect with task_output or stop with task_kill.',
+              ? 'Whether to run in the background and return a durable subagent id immediately. Defaults to true. Set false to wait for the result when your next action depends on it.'
+              : 'Whether to run as a background task and return its id. Defaults to false; collect with task_output or stop with task_kill.',
           },
         } : {},
       },
@@ -352,12 +384,8 @@ export function apply(ctx: Context, config: Config): void {
           ...maxDepth !== undefined ? { maxDepth } : {},
         }
 
-        if (args.run_in_background === true) {
-          // The validator permits undeclared keys, so schema omission also needs
-          // execution-time enforcement.
-          if (!backgroundEnabled) {
-            throw new Error('run_in_background is disabled for this tool instance (enableRunInBackground: false)')
-          }
+        const runSpec = resolveDelegationRun(args, { backgroundEnabled, continuable })
+        if (runSpec.runInBackground) {
           if (continuable) {
             // Resolves at inbox acceptance: the child owns its own turns from
             // there, so this call neither waits for nor collects a result.
@@ -404,9 +432,11 @@ export function apply(ctx: Context, config: Config): void {
   }
 
   // Register listeners before checking presence so no synchronous change is missed.
-  // TODO(subagent-dup-toolname): two WAITING fibers configured with the same
-  // toolName collide when their provider appears, and the duplicate-name throw
-  // rolls back the provider registration. Add an intent registry if this occurs.
+  // TODO(subagent-dup-toolname): two waiting one-shot fibers configured with the
+  // same toolName collide when their provider appears, and the duplicate-name
+  // throw rolls back the provider registration. Continuable instances reserve
+  // their prompt-section name during apply() and fail earlier. Add an intent
+  // registry if the late one-shot collision occurs in a shipped composition.
   ctx.on('subagent/provider-added', (provider) => {
     if (provider.name === config.provider && disposeTool === undefined) mount(provider)
   })
@@ -422,4 +452,16 @@ export function apply(ctx: Context, config: Config): void {
     // A backend fiber may activate later; a misspelled provider remains visible in this log.
     ctx.logger.info(`subagent provider "${config.provider}" not registered yet; the "${config.toolName ?? 'subagent'}" tool will register when it appears`)
   }
+  if (backgroundEnabled && continuable) {
+    // The section follows provider availability without its own manual
+    // lifecycle: empty text is omitted from rendered prompts while the tool is
+    // absent, and the registration itself stays owned by this plugin fiber.
+    ctx.systemPrompt.section({
+      name: `tool:${toolName}`,
+      order: SUBAGENT_SECTION_ORDER,
+      text: context => disposeTool === undefined || ctx.tools.get(toolName, context.scope) === undefined
+        ? ''
+        : `Use ${toolName} in the background by default. Start independent delegations together in one assistant message and continue useful work while they run. Set \`run_in_background: false\` only when your next action depends on that subagent's result. When a background run settles, the runtime sends you a notice containing its outcome and any final assistant message.`,
+    })
+  }
 }

packages/subagent/tool-subagent/tests/tool-subagent.spec.ts

@@ -7,7 +7,7 @@ import Loader from '@deepseek-ai/cordis-plugin-loader'
 import { CallId } from '@deepseek-ai/dsh-llm'
 import SystemPrompt from '@deepseek-ai/dsh-system-prompt'
 import ToolRegistry, { TOOL_ABORTED_BEFORE_DISPATCH } from '@deepseek-ai/dsh-tools'
-import { type Agent } from '@deepseek-ai/dsh-agent'
+import { assembleContextFor, type Agent } from '@deepseek-ai/dsh-agent'
 import AgentRegistry from '@deepseek-ai/dsh-agent'
 import AgentLoop from '@deepseek-ai/dsh-agent-loop'
 import { mountAgentLoopTestDependencies } from '@deepseek-ai/dsh-agent-loop-testkit'
@@ -313,6 +313,22 @@ describe('dsh-tool-subagent', () => {
     expect(text(result)).toBe('late but fine')
   })
 
+  it('keeps continuable guidance empty while its provider is absent', async () => {
+    const ctx = new Context()
+    await ctx.plugin(SystemPrompt)
+    await ctx.plugin(ToolRegistry)
+    await ctx.plugin(SubagentService)
+    tool.apply(ctx, {
+      provider: 'later-continuable',
+      backgroundMode: 'continuable',
+      maxDepth: 'provider-managed',
+    })
+
+    const assembly = await ctx.systemPrompt.assemble()
+    expect(assembly.sections.find(section => section.name === 'tool:subagent')?.text).toBe('')
+    expect(ctx.tools.schemas().some(schema => schema.name === 'subagent')).toBe(false)
+  })
+
   it('mirrors the provider lifecycle: gone on backend dispose, re-derived wording on re-registration', async () => {
     const ctx = new Context()
     await ctx.plugin(SystemPrompt)
@@ -338,13 +354,26 @@ describe('dsh-tool-subagent', () => {
     await ctx.plugin(ToolRegistry)
     await ctx.plugin(SubagentService)
 
-    // Arm 1: a mounted tool dies with its plugin fiber; the provider survives.
-    await mock.mountScriptedProvider(ctx, { name: 'mock' })
-    const mounted = await ctx.plugin(tool, { provider: 'mock' })
+    // Arm 1: a mounted tool and its prompt section die with the plugin fiber;
+    // the provider survives.
+    ctx.subagents.registerProvider({
+      name: 'continuable',
+      capabilities: { outputSchema: false, depthLimit: false, toolFilter: false, persona: false },
+      inheritsParentContext: false,
+      start: async () => { throw new Error('lifecycle test does not start a child') },
+      prepareContinuable: async () => ({}),
+    })
+    const mounted = await ctx.plugin(tool, {
+      provider: 'continuable',
+      backgroundMode: 'continuable',
+      maxDepth: 'provider-managed',
+    })
     expect(ctx.tools.schemas().some(s => s.name === 'subagent')).toBe(true)
+    expect((await ctx.systemPrompt.assemble()).sections.some(s => s.name === 'tool:subagent')).toBe(true)
     await mounted.dispose()
     expect(ctx.tools.schemas().some(s => s.name === 'subagent')).toBe(false)
-    expect(ctx.subagents.getProvider('mock')).toBeDefined()
+    expect((await ctx.systemPrompt.assemble()).sections.some(s => s.name === 'tool:subagent')).toBe(false)
+    expect(ctx.subagents.getProvider('continuable')).toBeDefined()
 
     // Arm 2: a fiber disposed while WAITING must not react to the provider
     // arriving later — a surviving listener would re-register a tool that no
@@ -563,7 +592,7 @@ describe('dsh-tool-subagent', () => {
     const ctx = new Context()
     await ctx.plugin(SystemPrompt)
     await ctx.plugin(ToolRegistry)
-    // No SubagentService mounted. The tool injects ['tools','subagents'] so its
+    // No SubagentService mounted. The tool injects its three required services so its
     // apply never runs; the tool is absent rather than half-registered.
     let booted = true
     try {
@@ -578,19 +607,19 @@ describe('dsh-tool-subagent', () => {
   })
 
   it('has the namespace-plugin export shape (no stray default) so the Loader keeps name/inject/Config/apply', () => {
-    // Postmortem 0001 guard: this plugin HAS `inject = ['tools','subagents']`, so
+    // Postmortem 0001 guard: this plugin HAS an explicit `inject`, so
     // a stray `export default apply` would collapse the module via
     // `unwrapExports` (`exports.default ?? exports`), DROP `inject`, and crash at
     // load with "cannot get property … without inject". Guard the shape directly.
     expect('default' in tool).toBe(false)
     expect(tool.name).toBe('tool-subagent')
-    expect(tool.inject).toEqual(['tools', 'subagents'])
+    expect(tool.inject).toEqual(['tools', 'subagents', 'systemPrompt'])
 
     const loader = Object.create(Loader.prototype) as Loader
     const unwrapped = loader.unwrapExports(tool) as Record<string, unknown>
     expect(unwrapped).toBe(tool)
     expect(unwrapped.name).toBe('tool-subagent')
-    expect(unwrapped.inject).toEqual(['tools', 'subagents'])
+    expect(unwrapped.inject).toEqual(['tools', 'subagents', 'systemPrompt'])
     expect(typeof unwrapped.apply).toBe('function')
     expect(unwrapped.Config).toBeDefined()
   })
@@ -985,21 +1014,31 @@ describe('dsh-tool-subagent continuable background mode', () => {
       signal: testToolSignal,
       callId: CallId('subagent-continuable'),
       name: 'subagent',
-      arguments: { description: 'do work', prompt: 'Reply OK', run_in_background: true },
+      arguments: { description: 'do work', prompt: 'Reply OK' },
     })).toEqual({ kind: 'parallel' })
   })
 
-  it('starts a continuable child and returns only its durable id, creating no Task', async () => {
+  it('defaults continuable delegation to background and returns only its durable id', async () => {
     const { ctx, parent } = await continuableSetup()
     const schema = ctx.tools.schemas().find(s => s.name === 'subagent')!
     // Continuable delegation has no Task, so the schema promises no collection.
     expect(schema.description).not.toContain('task_output')
     expect(schema.description).not.toContain('task_kill')
     expect(schema.description).toContain('send_message')
+    expect(schema.description).toContain('runs in the background by default')
+    expect(schema.description).not.toContain('never poll or wait on it')
+    const properties = (schema.parameters as {
+      properties: Record<string, { description?: string }>
+    }).properties
+    expect(properties.run_in_background?.description).toContain('Defaults to true')
+    const assembly = await ctx.systemPrompt.assemble(assembleContextFor(parent))
+    const guidance = assembly.sections.find(section => section.name === 'tool:subagent')
+    expect(guidance?.text).toContain('Use subagent in the background by default')
+    expect(guidance?.text).toContain('runtime sends you a notice containing its outcome')
 
     const started = await callSubagent(
       ctx,
-      { description: 'continuable work', prompt: 'dig in', run_in_background: true },
+      { description: 'continuable work', prompt: 'dig in' },
       { agent: parent },
     )
     expect(started.isError).toBe(false)
@@ -1018,6 +1057,29 @@ describe('dsh-tool-subagent continuable background mode', () => {
     expect(loaded.events.some(event => event.type === 'assistant/message')).toBe(true)
   })
 
+  it('hides continuable guidance when the current agent cannot see the tool', async () => {
+    const { ctx, parent } = await continuableSetup()
+    parent.ctx.tools.restrict({ deny: ['subagent'] })
+
+    expect(ctx.tools.get('subagent', parent)).toBeUndefined()
+    const assembly = await ctx.systemPrompt.assemble(assembleContextFor(parent))
+    expect(assembly.sections.find(section => section.name === 'tool:subagent')?.text).toBe('')
+  })
+
+  it('waits for a continuable provider only when run_in_background is explicitly false', async () => {
+    const { ctx, parent } = await continuableSetup()
+    const result = await callSubagent(
+      ctx,
+      { description: 'blocking work', prompt: 'dig in', run_in_background: false },
+      { agent: parent },
+    )
+    expect(result.isError).toBe(false)
+    if (result.isError) throw new Error('expected foreground subagent success')
+    expect(result.value).toMatchObject({ kind: 'foreground' })
+    expect(text(result)).toBe('continuable answer')
+    expect(ctx.tasks.list(parent)).toEqual([])
+  })
+
   it('isolates a cancelled continuable preparation from a concurrent sibling', async () => {
     const { ctx, parent } = await continuableSetup()
     const bothPreparing = Promise.withResolvers<undefined>()

packages/subagent/tool-subagent/tsconfig.json

@@ -26,6 +26,9 @@
     {
       "path": "../../core/tools"
     },
+    {
+      "path": "../../core/system-prompt"
+    },
     {
       "path": "../subagent"
     },

scripts/gen-tool-catalog.ts

@@ -436,7 +436,7 @@ const TOOL_PACKAGES: ToolPackage[] = [
     pkg: '@deepseek-ai/dsh-tool-subagent',
     dir: 'tool-subagent',
     source: 'packages/subagent/tool-subagent/src/index.ts',
-    requires: ['ctx.tools', 'ctx.subagents'],
+    requires: ['ctx.tools', 'ctx.subagents', 'ctx.systemPrompt'],
     writes: ['tool/call', 'tool/result', 'child session events through the chosen provider'],
     shippedNames: ['subagent', 'subagent_fork'],
     async mount(ctx) {
@@ -445,7 +445,7 @@ const TOOL_PACKAGES: ToolPackage[] = [
       await ctx.plugin(ToolSubagent, { provider: 'mock' })
     },
     note:
-      'The registered tool name is the load-time `toolName` config (default `subagent`); the schema above is that default. The shipped compositions load this package once per subagent backend, so the model additionally sees `subagent_fork` bound to the fork backend. Each instance\'s description and `run_in_background` parameter follow its own `backgroundMode` and `enableRunInBackground`, so the two shipped schemas are not identical: `subagent` is `continuable`, while `subagent_fork` stays `one-shot` — see `packages/bundle/base/cordis.patch.yml` and `examples/acp-agent/cordis.yml`.',
+      'The registered tool name is the load-time `toolName` config (default `subagent`); the schema above is that default. The shipped compositions load this package once per subagent backend, so the model additionally sees `subagent_fork` bound to the fork backend. Each instance\'s description, `run_in_background` parameter, and system-prompt policy follow its own `backgroundMode` and `enableRunInBackground`, so the two shipped schemas are not identical: `subagent` is `continuable` and defaults omitted calls to background with automatic settlement delivery, while `subagent_fork` stays `one-shot` and defaults them to foreground — see `packages/bundle/base/cordis.patch.yml` and `examples/acp-agent/cordis.yml`.',
   },
   {
     pkg: '@deepseek-ai/dsh-tool-subagent-control',