fix(subagent): require durability participant

.agents/notes/implemented/feature/2026-07-21-continuable-background-subagents.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/2026-07-21-continuable-background-subagents.md
-2026-07-21-continuable-background-subagents.md: 42e9f6dd653dee8df4b8c068e3a33b7c69f8dc4b
-2026-07-21-continuable-background-subagents.zh.md: e643e81f40074c3cc0cd6398b3f1d24e0d9bc988
+2026-07-21-continuable-background-subagents.md: fc1cd97dae2583f6d78ee1413561002b6391a0c9
+2026-07-21-continuable-background-subagents.zh.md: 31775d9c2b8bd6b2dc84b5e86d4dbc9d1bd8a1f5

.agents/notes/implemented/feature/2026-07-21-continuable-background-subagents.md

@@ -31,7 +31,7 @@ The low-level `ctx.subagents` seam stays collection-, Task-, and persistence-agn
 
 ### Task and cancellation ownership
 
-The initial background delegation asks the control service to start the child and register its Task. A continuable provider confirms the activation's final session state durable before fulfilling a successful run result. Task settlement awaits that result, calls `run.dispose()` (through the control service's `settleRun`), and only then records the `TaskOutcome`; `task_kill` aborts the active run, whose settlement path still disposes it. A terminal Task therefore leaves the durable child session but no live child Agent. A failed required durability checkpoint rejects the run with stable code `DURABILITY_FAILED` and the backend failure as its cause; the control service records a failed Task whose detail explains that the latest state was not confirmed persisted and may be unavailable or stale on resume.
+The initial background delegation asks the control service to start the child and register its Task. A continuable provider confirms the activation's final session state durable before fulfilling a successful run result. Task settlement awaits that result, calls `run.dispose()` (through the control service's `settleRun`), and only then records the `TaskOutcome`; `task_kill` aborts the active run, whose settlement path still disposes it. A terminal Task therefore leaves the durable child session but no live child Agent. A required durability checkpoint with no installed listener or a failing listener rejects the run with stable code `DURABILITY_FAILED` and the checkpoint failure as its cause; the control service records a failed Task whose detail explains that the latest state was not confirmed persisted and may be unavailable or stale on resume.
 
 Every later turn creates another Task. Its producer resources cover only that activation, never the child session. It reaches one terminal status, has one result, and is never reopened. The exact live parent Agent remains the Task registry owner: disposing that instance cancels, awaits, and removes its Tasks. Task APIs authorize a caller whose session id matches that owner, but a same-id replacement does not become the notification or teardown target. This preserves the `settleRun()` contract and bounds Task-owned live children by concurrent work rather than historical session count.
 
@@ -109,7 +109,7 @@ Task records and active-run associations are process-local. Persistence makes th
 
 ## Testing
 
-- `packages/subagent/subagent-inprocess/tests/subagent-inprocess.spec.ts` pins the continuable durability boundary: a permanent flush failure rejects with `DURABILITY_FAILED` and its cause, a transient loop-checkpoint failure can succeed on the final confirmation, cancellation owns either final-checkpoint outcome, resume also confirms durability, and foreground runs remain best-effort. `packages/subagent/subagent/tests/continuation.spec.ts` drives the real stack (agent loop, JSONL persistence, spawn/fork providers, Task service, and `ctx.subagents`) keylessly: initial and resumed activations create fresh Tasks and dispose their runs before terminal; the descriptor event is turn-enclosed, model-hidden, versioned, and durable under the service-allocated child id; cancellation, steering, cold follow-up, authorization, ownership conflicts, and resume races retain the contracts described above.
+- `packages/subagent/subagent-inprocess/tests/subagent-inprocess.spec.ts` pins the continuable durability boundary: an absent or detached flush listener and a permanent listener failure reject with `DURABILITY_FAILED`, a transient loop-checkpoint failure can succeed on the final confirmation, cancellation owns either final-checkpoint outcome, resume also confirms durability, and foreground runs remain best-effort. `packages/subagent/subagent/tests/continuation.spec.ts` drives the real stack (agent loop, JSONL persistence, spawn/fork providers, Task service, and `ctx.subagents`) keylessly: initial and resumed activations create fresh Tasks and dispose their runs before terminal; the descriptor event is turn-enclosed, model-hidden, versioned, and durable under the service-allocated child id; cancellation, steering, cold follow-up, authorization, ownership conflicts, and resume races retain the contracts described above.
 - `packages/subagent/tool-subagent-control/tests/tool-subagent-control.spec.ts` pins the `send_message` schema, coordinator attribution, both route renderings, the not-delivered failure, the no-agent rejection, and HMR disposal.
 - `packages/subagent/tool-subagent/tests/tool-subagent.spec.ts` covers the configured background route: continuable mode requires a resumable provider and returns both ids without requiring `send_message`, while one-shot mode keeps the plain Task acknowledgement even when the provider can resume.
 - `packages/sdk/helper/tests/project.spec.ts` pins the Task service and model-facing Task controls in generated spawn and fork compositions.

.agents/notes/implemented/feature/2026-07-21-continuable-background-subagents.zh.md

@@ -31,7 +31,7 @@ durable child Session
 
 ### Task 与取消的所有权
 
-初始后台委派请求控制服务启动 child 并注册其 Task。可继续提供方只有在确认本次激活的最终会话状态已持久化后，才会返回成功的 run 结果。Task 结算流程等待该结果，调用 `run.dispose()`（经由控制服务的 `settleRun`），然后才记录 `TaskOutcome`；`task_kill` 中止活跃 run，其结算路径仍会 dispose 该 run。因此，终态 Task 会留下持久化 child 会话，但不会留下存活的 child agent。必需的持久性检查点失败时，run 会以稳定错误码 `DURABILITY_FAILED` 拒绝，并将后端失败保留为失败原因；控制服务会记录失败的 Task，其详情说明最新状态未确认已持久化，因此恢复时可能不可用或已陈旧。
+初始后台委派请求控制服务启动 child 并注册其 Task。可继续提供方只有在确认本次激活的最终会话状态已持久化后，才会返回成功的 run 结果。Task 结算流程等待该结果，调用 `run.dispose()`（经由控制服务的 `settleRun`），然后才记录 `TaskOutcome`；`task_kill` 中止活跃 run，其结算路径仍会 dispose 该 run。因此，终态 Task 会留下持久化 child 会话，但不会留下存活的 child agent。必需的持久性检查点若没有已安装的监听器或任一监听器失败，run 会以稳定错误码 `DURABILITY_FAILED` 拒绝，并将检查点失败保留为失败原因；控制服务会记录失败的 Task，其详情说明最新状态未确认已持久化，因此恢复时可能不可用或已陈旧。
 
 后续每个轮次都会创建另一个 Task。该轮 producer 持有的执行资源仅服务于这次激活，不属于 child 会话。它只会到达一次终态、只产生一个结果，也不会重新打开。Task 注册表中当前注册的那个存活 parent agent 实例仍是其 owner：dispose 该实例会取消、等待并移除其 Task。Task API 会授权 session id 与该 owner 匹配的调用方，但 id 相同的替代实例不会成为通知或资源清理目标。这一设计保留 `settleRun()` 契约，并使 Task 所拥有的存活 child 数量受并发工作量限制，而不是随历史会话数量增长。
 
@@ -109,7 +109,7 @@ Task 记录和活跃 run 关联都位于进程内。持久化使 child 会话可
 
 ## 测试
 
-- `packages/subagent/subagent-inprocess/tests/subagent-inprocess.spec.ts` 固定可继续执行的持久性边界：flush 持续失败时会以 `DURABILITY_FAILED` 拒绝并保留失败原因，循环检查点的瞬时失败可在最终确认成功后继续完成，发生取消时最终检查点无论成功还是失败都由取消优先决定结果，resume 同样会确认持久性，而前台运行仍采用尽力而为策略。`packages/subagent/subagent/tests/continuation.spec.ts` 以无密钥方式驱动真实栈（agent loop、JSONL 持久化、spawn／fork 提供方、Task 服务和 `ctx.subagents`）：初始及恢复后的激活都会创建新 Task，并在进入终态前 dispose 各自的 run；描述符事件位于轮次内、对模型隐藏、带版本，并在服务分配的 child id 下持久化；取消、steering、cold follow-up、授权、所有权冲突与 resume 竞态保留上述契约。
+- `packages/subagent/subagent-inprocess/tests/subagent-inprocess.spec.ts` 固定可继续执行的持久性边界：缺少 flush 监听器、flush 监听器已脱离或监听器持续失败时，均会以 `DURABILITY_FAILED` 拒绝；循环检查点的瞬时失败可在最终确认成功后继续完成，发生取消时最终检查点无论成功还是失败都由取消优先决定结果，resume 同样会确认持久性，而前台运行仍采用尽力而为策略。`packages/subagent/subagent/tests/continuation.spec.ts` 以无密钥方式驱动真实栈（agent loop、JSONL 持久化、spawn／fork 提供方、Task 服务和 `ctx.subagents`）：初始及恢复后的激活都会创建新 Task，并在进入终态前 dispose 各自的 run；描述符事件位于轮次内、对模型隐藏、带版本，并在服务分配的 child id 下持久化；取消、steering、cold follow-up、授权、所有权冲突与 resume 竞态保留上述契约。
 - `packages/subagent/tool-subagent-control/tests/tool-subagent-control.spec.ts` 固定 `send_message` 的 schema、coordinator 来源标记、两种路由渲染、未送达失败、无 agent 时的拒绝，以及 HMR（热模块替换）dispose。
 - `packages/subagent/tool-subagent/tests/tool-subagent.spec.ts` 覆盖配置的后台路由：可继续模式要求提供方可恢复，并在不要求 `send_message` 的情况下返回两个 id；即使提供方可以恢复，一次性模式仍保持普通的 Task 确认消息。
 - `packages/sdk/helper/tests/project.spec.ts` 固定生成的 spawn 与 fork 组合中的 Task 服务及面向模型的 Task 控制工具。

docs/cordis-catalog/events.md

@@ -685,13 +685,14 @@ Source: [`packages/core/session/src/index.ts:93`](../../packages/core/session/sr
 
 ### `session/flush` — parallel
 
-Awaited parallel durability checkpoint: every listener runs and the caller awaits all of them, with no waterfall veto. Dispatch through SessionStore.flush. Scope-filtered dispatch (`@deepseek-ai/dsh-scope`) reuses the session's owner scope.
+Awaited parallel durability checkpoint: every listener runs and the caller awaits all of them, with no waterfall veto. An empty listener snapshot is accepted by SessionStore.flush and rejected by SessionStore.flushRequired. Scope-filtered dispatch (`@deepseek-ai/dsh-scope`) reuses the session's owner scope.
 
 ```ts cordis-catalog
 /**
  * Awaited parallel durability checkpoint: every listener runs and the
- * caller awaits all of them, with no waterfall veto. Dispatch through
- * {@link SessionStore.flush}. Scope-filtered dispatch
+ * caller awaits all of them, with no waterfall veto. An empty listener
+ * snapshot is accepted by {@link SessionStore.flush} and rejected by
+ * {@link SessionStore.flushRequired}. Scope-filtered dispatch
  * (`@deepseek-ai/dsh-scope`) reuses the session's owner scope.
  * @param session - the session whose buffered events must reach durable storage.
  * @dshScopeScan unsupported
@@ -702,7 +703,7 @@ Awaited parallel durability checkpoint: every listener runs and the caller await
 
 Types: [Scoped](../core-data-structures/scope.md) · [Session](../core-data-structures/session.md)
 
-Source: [`packages/core/session/src/index.ts:103`](../../packages/core/session/src/index.ts)
+Source: [`packages/core/session/src/index.ts:104`](../../packages/core/session/src/index.ts)
 
 ## `settings/*`
 

docs/cordis-catalog/services.md

@@ -1640,6 +1640,18 @@ announce(session: Session): void
  */
 async flush(session: Session): Promise<void>
 
+/**
+ * Dispatch the same awaited checkpoint as {@link flush}, but reject when its
+ * scoped listener snapshot is empty. Callers use this operation when success
+ * requires an installed durability participant rather than optional
+ * best-effort persistence.
+ * @param session - the session whose buffered events must reach durable storage.
+ * @returns resolves when at least one listener participated and every
+ *   listener settled successfully.
+ * @throws when no listener is registered or any registered listener fails.
+ */
+async flushRequired(session: Session): Promise<void>
+
 /**
  * Look up a live session.
  * @param id - the session id to look up.
@@ -1672,7 +1684,7 @@ fork(source: SessionForkSource, boundary?: number, childSessionId?: SessionId):
 
 Types: [CreateSessionOptions](../core-data-structures/persistence.md) · [Session](../core-data-structures/session.md) · [SessionId](../core-data-structures/core.md)
 
-Source: [`packages/core/session/src/index.ts:765`](../../packages/core/session/src/index.ts)
+Source: [`packages/core/session/src/index.ts:766`](../../packages/core/session/src/index.ts)
 
 ## `ctx.sessionTitle` — `SessionTitleService`
 

docs/event-producer-consumer.md

@@ -37,7 +37,7 @@ This matrix shows which packages dispatch each harness-owned event and which pac
 | `session/created` | `emit` | [`packages/core/session/src/index.ts:71`](../packages/core/session/src/index.ts) | [`session`](../packages/core/session) (`events.dispatch`) | `apiproxy`, [`compact`](../packages/compact/compact), [`goal`](../packages/goal/goal), [`hook-protocol`](../packages/hooks/hook-protocol), [`jsonrpc`](../packages/ui/jsonrpc), [`llm-retry`](../packages/llm/llm-retry), [`permission`](../packages/ui/permission), [`plan-mode`](../packages/plan/plan-mode), [`session`](../packages/core/session), [`session-persistence`](../packages/session-persistence/session-persistence), [`session-telemetry`](../packages/telemetry/session-telemetry), [`tools`](../packages/core/tools), [`user-approval`](../packages/ui/user-approval) |
 | `session/disposed` | `emit` | [`packages/core/session/src/index.ts:81`](../packages/core/session/src/index.ts) | [`session`](../packages/core/session) (`events.dispatch`) | [`agent-loop`](../packages/core/agent-loop), `apiproxy`, [`session-persistence`](../packages/session-persistence/session-persistence), [`session-projection-cache`](../packages/session-projection/session-projection-cache), [`session-telemetry`](../packages/telemetry/session-telemetry), [`session-title`](../packages/session-title/session-title) |
 | `session/event` | `emit` | [`packages/core/session/src/index.ts:93`](../packages/core/session/src/index.ts) | [`session`](../packages/core/session) (`events.dispatch`) | [`acp`](../packages/acp/acp), `apiproxy`, [`cli-demo`](../packages/examples/cli-demo), [`compact`](../packages/compact/compact), [`compact-basic`](../packages/compact/compact-basic), [`goal`](../packages/goal/goal), [`goal-session`](../packages/goal/goal-session), [`hook-protocol`](../packages/hooks/hook-protocol), [`jsonrpc`](../packages/ui/jsonrpc), [`session`](../packages/core/session), [`session-persistence`](../packages/session-persistence/session-persistence), [`session-projection`](../packages/session-projection/session-projection), [`session-projection-cache`](../packages/session-projection/session-projection-cache), [`session-telemetry`](../packages/telemetry/session-telemetry), [`session-title`](../packages/session-title/session-title), [`token-meter`](../packages/llm/token-meter), [`tools`](../packages/core/tools), [`tui`](../packages/ui/tui), [`user-approval`](../packages/ui/user-approval), [`workspace-context`](../packages/context/workspace-context) |
-| `session/flush` | `parallel` | [`packages/core/session/src/index.ts:103`](../packages/core/session/src/index.ts) | [`session`](../packages/core/session) (`events.dispatch`) | [`session-persistence`](../packages/session-persistence/session-persistence), [`session-telemetry`](../packages/telemetry/session-telemetry) |
+| `session/flush` | `parallel` | [`packages/core/session/src/index.ts:104`](../packages/core/session/src/index.ts) | [`session`](../packages/core/session) (`events.dispatch`) | [`session-persistence`](../packages/session-persistence/session-persistence), [`session-telemetry`](../packages/telemetry/session-telemetry) |
 | `settings/document-updated` | `emit` | [`packages/settings/settings/src/index.ts:150`](../packages/settings/settings/src/index.ts) | [`settings`](../packages/settings/settings) (`events.dispatch`) | `apiproxy` |
 | `settings/updated` | `emit` | [`packages/settings/settings/src/index.ts:137`](../packages/settings/settings/src/index.ts) | [`settings`](../packages/settings/settings) (`events.dispatch`) | [`settings`](../packages/settings/settings) |
 | `skills/change` | `emit` | [`packages/skill/skill/src/index.ts:188`](../packages/skill/skill/src/index.ts) | [`skill`](../packages/skill/skill) (`events.dispatch`) | [`tui`](../packages/ui/tui) |

packages/cordis/tool-cordis/src/api-catalog.ts

@@ -746,6 +746,10 @@ export const SERVICE_API: readonly ServiceApiEntry[] = [
         signature: 'async flush(session: Session): Promise<void>',
         jsDoc: '/**\n * Dispatch the awaited `session/flush` durability checkpoint for `session`,\n * with the carrier captured at {@link enter}. THE flush entry point: the\n * store owns the carrier, so callers (the loop\'s turn-end checkpoint, idle\n * injection, teardown drains) must come through here rather than dispatch a\n * raw `ctx.parallel(\'session/flush\', …)` — one owner, one spelling, and the\n * scoped-dispatch invariant can pin it.\n * @param session - the session whose buffered events must reach durable storage.\n * @returns resolves when every flush listener has settled; after all settle,\n *   rejects with the first registered listener failure if any listener failed.\n */',
       },
+      {
+        signature: 'async flushRequired(session: Session): Promise<void>',
+        jsDoc: '/**\n * Dispatch the same awaited checkpoint as {@link flush}, but reject when its\n * scoped listener snapshot is empty. Callers use this operation when success\n * requires an installed durability participant rather than optional\n * best-effort persistence.\n * @param session - the session whose buffered events must reach durable storage.\n * @returns resolves when at least one listener participated and every\n *   listener settled successfully.\n * @throws when no listener is registered or any registered listener fails.\n */',
+      },
       {
         signature: 'get(id: SessionId): Session | undefined',
         jsDoc: '/**\n * Look up a live session.\n * @param id - the session id to look up.\n * @returns the session, or undefined when no live session has that id.\n */',
@@ -1410,7 +1414,7 @@ export const EVENT_API: readonly EventApiEntry[] = [
     name: 'session/flush',
     mode: 'parallel',
     signature: '\'session/flush\'(this: Scoped<Session>, session: Session): Promise<void> | void',
-    jsDoc: '/**\n * Awaited parallel durability checkpoint: every listener runs and the\n * caller awaits all of them, with no waterfall veto. Dispatch through\n * {@link SessionStore.flush}. Scope-filtered dispatch\n * (`@deepseek-ai/dsh-scope`) reuses the session\'s owner scope.\n * @param session - the session whose buffered events must reach durable storage.\n * @dshScopeScan unsupported\n * @mode parallel\n */',
+    jsDoc: '/**\n * Awaited parallel durability checkpoint: every listener runs and the\n * caller awaits all of them, with no waterfall veto. An empty listener\n * snapshot is accepted by {@link SessionStore.flush} and rejected by\n * {@link SessionStore.flushRequired}. Scope-filtered dispatch\n * (`@deepseek-ai/dsh-scope`) reuses the session\'s owner scope.\n * @param session - the session whose buffered events must reach durable storage.\n * @dshScopeScan unsupported\n * @mode parallel\n */',
     summary: 'Awaited parallel durability checkpoint: every listener runs and the caller awaits all of them, with no waterfall veto.',
   },
   {

packages/core/session/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/core/session/README.md
-README.md: 9c7d41901e6fb0133fff0e210260e5310a025f75
-README.zh.md: ca1292289901a09b83f9b0a794fa4edc9754b1da
+README.md: 59e8694a957e9742a22662766d671dc2145c44e3
+README.zh.md: 7618bc8f3a9146a4fc5afbfb19317deef7f13068

packages/core/session/README.md

@@ -14,6 +14,7 @@ Creates and holds event-sourced `Session` instances. Persistence is intentionall
 
 - `ctx.sessions.create(id?, { seed?, meta? }?)` validates and detaches durable seed/header data, fills the version and id, defaults `createdAt` to now, publishes the session, and binds it to the calling fiber. Persisted reconstruction supplies its original `createdAt`, `seedLength`, and `delegationDepth`.
 - `ctx.sessions.flush(session)` dispatches the awaited parallel durability checkpoint through the session's captured scope. Every listener starts and the call waits for all to settle before reporting failure; unpublished, detached, and stale objects reject.
+- `ctx.sessions.flushRequired(session)` uses the same dispatch but also rejects an empty scoped listener snapshot. Callers use it when success requires an installed durability participant rather than optional best-effort persistence.
 - `findLastMessageTurnEnd(events)` pairs message-triggered starts with their ends and returns the latest matched `turn/end`. Outcome consumers use this fold instead of the raw latest log event because between-turn records and non-message turns have no prompt outcome.
 - `ctx.sessions.fork(source, boundary?, childSessionId?): Session` — Resolve a live session object or id, select a seed through the inclusive `boundary` event seq (default: current last event), require that prefix to end outside an open turn, and create a live child session with lineage metadata.
 - `ctx.sessions.get(id: SessionId): Session | undefined`

packages/core/session/README.zh.md

@@ -14,6 +14,7 @@
 
 - `ctx.sessions.create(id?, { seed?, meta? }?)` 校验持久种子／头部数据并生成脱离副本，补齐版本和 id，在未提供 `createdAt` 时使用当前时间，发布会话并将其绑定到调用方 fiber。持久化重建会提供原始的 `createdAt`、`seedLength` 和 `delegationDepth`。
 - `ctx.sessions.flush(session)` 通过会话捕获的作用域分发受等待的并行持久性检查点。每个监听器都会启动；调用会等待全部结算后才报告失败。未发布、已脱离和陈旧的对象会被拒绝。
+- `ctx.sessions.flushRequired(session)` 沿用相同的分发逻辑，但也会拒绝空的作用域监听器快照。若成功要求已安装的持久性参与方介入，而不是采用可选的尽力持久化，调用方应使用此方法。
 - `findLastMessageTurnEnd(events)` 将由消息触发的开始与结束配对，并返回最近匹配的 `turn/end`。结果消费方使用该折叠逻辑，而不直接取日志中最近的事件，因为轮次间记录和非消息轮次没有提示词结果。
 - `ctx.sessions.fork(source, boundary?, childSessionId?): Session`：解析实时会话对象或 id，选取截至 `boundary` 事件序号（含该事件）的种子（默认为当前最后一个事件），要求所选前缀结束时没有开放轮次，再创建带谱系元数据的实时子会话。
 - `ctx.sessions.get(id: SessionId): Session | undefined`

packages/core/session/src/index.ts

@@ -93,8 +93,9 @@ declare module 'cordis' {
     'session/event'(this: Scoped<Session>, session: Session, event: SessionEvent): void
     /**
      * Awaited parallel durability checkpoint: every listener runs and the
-     * caller awaits all of them, with no waterfall veto. Dispatch through
-     * {@link SessionStore.flush}. Scope-filtered dispatch
+     * caller awaits all of them, with no waterfall veto. An empty listener
+     * snapshot is accepted by {@link SessionStore.flush} and rejected by
+     * {@link SessionStore.flushRequired}. Scope-filtered dispatch
      * (`@deepseek-ai/dsh-scope`) reuses the session's owner scope.
      * @param session - the session whose buffered events must reach durable storage.
      * @dshScopeScan unsupported
@@ -973,9 +974,31 @@ export class SessionStore extends Service {
    *   rejects with the first registered listener failure if any listener failed.
    */
   async flush(session: Session): Promise<void> {
+    await this.dispatchFlush(session, false)
+  }
+
+  /**
+   * Dispatch the same awaited checkpoint as {@link flush}, but reject when its
+   * scoped listener snapshot is empty. Callers use this operation when success
+   * requires an installed durability participant rather than optional
+   * best-effort persistence.
+   * @param session - the session whose buffered events must reach durable storage.
+   * @returns resolves when at least one listener participated and every
+   *   listener settled successfully.
+   * @throws when no listener is registered or any registered listener fails.
+   */
+  async flushRequired(session: Session): Promise<void> {
+    await this.dispatchFlush(session, true)
+  }
+
+  /** Dispatch one optional or required flush listener snapshot. */
+  private async dispatchFlush(session: Session, requireListener: boolean): Promise<void> {
     const { carrier } = this.liveEntryFor(session)
     const callbackArgs: unknown[] = [session]
     const callbacks = collectSessionCallbacks(this.ctx, [carrier, 'session/flush', session])
+    if (requireListener && callbacks.length === 0) {
+      throw new Error(`session "${session.id}" required durability checkpoint has no registered listener`)
+    }
     const results = await Promise.allSettled(callbacks.map((callback) => {
       try {
         return callback(...callbackArgs)

packages/core/session/tests/scoped.spec.ts

@@ -80,6 +80,33 @@ describe('session dispatch carriers', () => {
 })
 
 describe('sessions.flush()', () => {
+  it('allows an ordinary flush with no listeners', async () => {
+    const ctx = await mount()
+    const session = ctx.sessions.create()
+
+    await expect(ctx.sessions.flush(session)).resolves.toBeUndefined()
+  })
+
+  it('rejects a required flush with no listeners', async () => {
+    const ctx = await mount()
+    const session = ctx.sessions.create()
+
+    await expect(ctx.sessions.flushRequired(session)).rejects.toThrow(
+      `session "${session.id}" required durability checkpoint has no registered listener`,
+    )
+  })
+
+  it('completes a required flush when a listener succeeds', async () => {
+    const ctx = await mount()
+    const session = ctx.sessions.create()
+    const flushed: Session[] = []
+    ctx.on('session/flush', current => void flushed.push(current))
+
+    await ctx.sessions.flushRequired(session)
+
+    expect(flushed).toEqual([session])
+  })
+
   it('dispatches session/flush with the owning carrier and awaits all listeners', async () => {
     const ctx = await mount()
     const scope = await mintScope(ctx, 'owner')

packages/subagent/subagent-inprocess/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/subagent-inprocess/README.md
-README.md: 1bbbfd282fe98f73b1828b22a95efd34e5ddc0ab
-README.zh.md: d6dc91415beb3986ad226a8467ce2abbabce8591
+README.md: afc92cf4f38830c22a2de401620e0223e7bf62d1
+README.zh.md: dcf7d343901145f63758bfce0f85fa70691cb14e

packages/subagent/subagent-inprocess/README.md

@@ -14,7 +14,7 @@ The driver follows this sequence:
 2. Call `parent.ctx.agents.create` directly, passing the required request signal into the factory's creation transaction. A continuable request publishes exactly `request.continuation.sessionId` instead of an internally minted id.
 3. During that transaction's unpublished setup window, install the requested persona, tool restriction, structured-output runtime, and — for a continuable request — the one-shot `agent/step` contribution that appends the `subagent/descriptor` event after the initial `turn/start` and before the first request, so the descriptor reaches persistence with that turn's flush.
 4. Publish the child, retain the returned `AgentHandle`, and drive one task with `child.followup(prompt)` followed by `child.whenIdle()`.
-5. For a continuable start or resume, call `child.ctx.sessions.flush(child.session)` again before returning the result. This final confirmation retries events retained after a failed turn checkpoint; if it still fails, `result` rejects with `SubagentError.code === 'DURABILITY_FAILED'`, retains the backend failure as `cause`, and names the resumability risk in its message. Activation cancellation during this await owns the unpublished result even when the completed turn was already recorded or the checkpoint subsequently fails. Foreground runs keep the loop's best-effort checkpoint behavior.
+5. For a continuable start or resume, call `child.ctx.sessions.flushRequired(child.session)` again before returning the result. This final confirmation requires an installed durability listener and retries events retained after a failed turn checkpoint; if no listener participates or any listener fails, `result` rejects with `SubagentError.code === 'DURABILITY_FAILED'`, retains the checkpoint failure as `cause`, and names the resumability risk in its message. Activation cancellation during this await owns the unpublished result even when the completed turn was already recorded or the checkpoint subsequently fails. Foreground runs keep the loop's best-effort checkpoint behavior.
 6. Read the child's own last assistant message and latest message-triggered turn reason, excluding any fork seed and later plugin-owned between-turn records.
 
 The child gets the parent's working-directory/session lineage and inherits the parent provider, model, and output-token cap unless `request.agentOptions` overrides them. It gets a fresh flat registration scope: parent ownership does not import parent tool restrictions or establish an authority subset.

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

@@ -14,7 +14,7 @@
 2. 直接调用 `parent.ctx.agents.create`，把必需的请求信号传入工厂的创建事务。可继续请求会精确发布 `request.continuation.sessionId`，而不是内部生成的 ID。
 3. 在该事务未发布的设置窗口中，安装请求的 persona、工具限制和结构化输出运行时；对于可继续请求，还会安装一次性的 `agent/step` 贡献，在初始 `turn/start` 之后、首次请求之前追加 `subagent/descriptor` 事件，使描述符随该轮次的 flush 到达持久化层。
 4. 发布子 agent，保留返回的 `AgentHandle`，并通过先调用 `child.followup(prompt)`、再调用 `child.whenIdle()` 来驱动一项任务。
-5. 对于可继续的启动或恢复，在返回结果前再次调用 `child.ctx.sessions.flush(child.session)`。这次最终确认会重试轮次检查点失败后保留的事件；若仍然失败，`result` 会以 `SubagentError.code === 'DURABILITY_FAILED'` 拒绝，保留后端失败作为 `cause`，并在消息中指出可恢复性风险。在这次等待期间取消 activation 时，即使已记录完成的轮次，或检查点随后失败，取消仍决定尚未发布的结果。前台运行仍采用循环的尽力而为检查点行为。
+5. 对于可继续启动或恢复，在返回结果前再次调用 `child.ctx.sessions.flushRequired(child.session)`。这次最终确认要求有已安装的持久性监听器参与，并会重试轮次检查点失败后保留的事件；如果没有监听器参与或任一监听器失败，`result` 会以 `SubagentError.code === 'DURABILITY_FAILED'` 拒绝，将检查点失败保留为 `cause`，并在消息中说明恢复风险。即使已记录完成的轮次，或随后检查点失败，等待期间发生的激活取消仍决定尚未发布的结果。前台运行保留循环的尽力检查点行为。
 6. 读取子 agent 自身最后一条 assistant 消息，以及由消息触发的最新轮次原因；排除任何 fork 初始内容和后续由插件拥有的轮次间记录。
 
 子 agent 会获得父 agent 的工作目录／会话谱系；除非 `request.agentOptions` 覆盖，否则还会继承父 agent 的提供方、模型和输出 token 上限。它获得全新的扁平注册作用域：父级所有权不会导入父 agent 的工具限制，也不会建立权限子集。

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

@@ -270,7 +270,7 @@ function driveTurn(
       await child.whenIdle()
       if (durability === 'required') {
         try {
-          await child.ctx.sessions.flush(child.session)
+          await child.ctx.sessions.flushRequired(child.session)
         } catch (error: unknown) {
           if (!signal.aborted) {
             throw new SubagentError(

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

@@ -73,6 +73,40 @@ describe('startInProcessRun', () => {
     expect(ctx.agents.get(run.id)).toBeUndefined()
   })
 
+  it('rejects a continuable child when no durability listener is registered', async () => {
+    const { parent } = await setup([textResponse('driver answer')])
+
+    const run = await startInProcessRun(continuableRequest(parent), {})
+    const caught: unknown = await run.result.catch((error: unknown) => error)
+
+    expect(caught).toBeInstanceOf(SubagentError)
+    const durabilityError = caught as SubagentError
+    expect(durabilityError.code).toBe('DURABILITY_FAILED')
+    expect(durabilityError.message).toContain('required durability checkpoint has no registered listener')
+    await run.dispose()
+  })
+
+  it('rejects when the durability listener disappears before final confirmation', async () => {
+    const { ctx, parent } = await setup([textResponse('driver answer')])
+    let flushes = 0
+    let detach = (): void => {}
+    detach = ctx.on('session/flush', (session) => {
+      if (session.header.parentSession === undefined) return
+      flushes++
+      if (flushes === 1) detach()
+    })
+
+    const run = await startInProcessRun(continuableRequest(parent), {})
+    const caught: unknown = await run.result.catch((error: unknown) => error)
+
+    expect(caught).toBeInstanceOf(SubagentError)
+    const durabilityError = caught as SubagentError
+    expect(durabilityError.code).toBe('DURABILITY_FAILED')
+    expect(durabilityError.message).toContain('required durability checkpoint has no registered listener')
+    expect(flushes).toBe(1)
+    await run.dispose()
+  })
+
   it('requires a final durability checkpoint for a continuable child', async () => {
     const { ctx, parent } = await setup([textResponse('driver answer')])
     const failure = new Error('disk full')
@@ -312,7 +346,7 @@ describe('startInProcessRun', () => {
       acceptsNextStep: false,
       ctx: {
         sessions: {
-          flush: () => {
+          flushRequired: () => {
             flushes++
             return Promise.resolve()
           },

packages/subagent/subagent/tests/continuation.spec.ts

@@ -1,4 +1,4 @@
-import { afterEach, describe, expect, it } from 'vitest'
+import { afterEach, describe, expect, it, vi } from 'vitest'
 import { mkdtempSync, rmSync } from 'node:fs'
 import { tmpdir } from 'node:os'
 import { join } from 'node:path'
@@ -61,10 +61,12 @@ afterEach(() => {
 async function setupWith(adapter: LlmAdapter, options: { persistence?: boolean } = {}) {
   const ctx = new Context()
   await mountAgentLoopTestDependencies(ctx)
+  let disposePersistence: (() => Promise<void>) | undefined
   if (options.persistence !== false) {
     const root = mkdtempSync(join(tmpdir(), 'dsh-subagent-continuation-'))
     roots.push(root)
-    await ctx.plugin(JsonlSessionPersistence, { root })
+    const persistenceFiber = await ctx.plugin(JsonlSessionPersistence, { root })
+    disposePersistence = () => persistenceFiber.dispose()
   }
   await ctx.plugin(AgentLoop, { agents: [] })
   await ctx.plugin(SubagentService)
@@ -74,7 +76,7 @@ async function setupWith(adapter: LlmAdapter, options: { persistence?: boolean }
   await ctx.plugin(ToolTasks, {})
   ctx.llm.registerAdapter(['mock'], adapter)
   const parent = ctx.agentLoop.create(SessionId('parent'), { provider: 'mock', model: 'mock' })
-  return { ctx, parent }
+  return { ctx, parent, disposePersistence }
 }
 
 async function setup(script: Script, options: { persistence?: boolean } = {}) {
@@ -141,6 +143,25 @@ describe('SubagentService.startContinuable', () => {
     expect(ctx.agents.get(started.childId)).toBeUndefined()
   })
 
+  it('fails the Task when persistence detaches before the activation completes', async () => {
+    const releaseResponse = Promise.withResolvers<undefined>()
+    const adapter = new GatedAdapter([
+      { chunks: textResponse('unconfirmed answer'), gate: releaseResponse.promise },
+    ])
+    const { ctx, parent, disposePersistence } = await setupWith(adapter)
+    const started = ctx.subagents.startContinuable(startSpec(parent))
+    await vi.waitFor(() => { expect(adapter.requests).toHaveLength(1) })
+
+    await disposePersistence!()
+    releaseResponse.resolve(undefined)
+
+    const snapshot = await waitTerminal(ctx, started.taskId, parent)
+    expect(snapshot.status).toBe('failed')
+    expect(snapshot.detail).toContain('durability checkpoint failed')
+    expect(snapshot.detail).toContain('required durability checkpoint has no registered listener')
+    expect(ctx.agents.get(started.childId)).toBeUndefined()
+  })
+
   it('publishes the service-allocated child id and appends the turn-enclosed descriptor', async () => {
     const { ctx, parent } = await setup([textResponse('answer')])
     const seen: SessionEvent[] = []