docs: clarify scoped persona shadowing

packages/core/agent-loop/README.md

@@ -40,7 +40,7 @@ interface Config {
 }
 ```
 
-Agents listed in config are auto-created at startup. `cwd` applies only to fresh config-created sessions; `resumeSessionId` keeps the persisted session header. There is no per-agent persona: the deployment persona is `dsh-system-prompt`'s own `persona` config, shared by every agent in the context. The plugin registers the built-in `model`/`cwd` prompt variables on `ctx.systemPrompt`, resolved per step from the `assemble({ agent })` context — runtime facts of the agents THIS loop drives, unlike the `harness:identity`/`deployment:persona` sections, which live on `dsh-system-prompt` so they survive a swapped loop plugin.
+Agents listed in config are auto-created at startup. `cwd` applies only to fresh config-created sessions; `resumeSessionId` keeps the persisted session header. Config agents have no per-agent persona field: they use `dsh-system-prompt`'s deployment default, while programmatic factory callers can register an agent-scoped `deployment:persona` shadow in `setup`. The plugin registers the built-in `model`/`cwd` prompt variables on `ctx.systemPrompt`, resolved per step from the `assemble({ agent })` context — runtime facts of the agents THIS loop drives, unlike the `harness:identity` and default `deployment:persona` sections, which live on `dsh-system-prompt` so they survive a swapped loop plugin.
 
 ### Exported concrete class
 

packages/core/system-prompt/README.md

@@ -1,12 +1,12 @@
 # dsh-system-prompt
 
-System prompt assembly registry. Plugins contribute ordered text sections, tool-schema providers, and named prompt variables; contributions that implement required protocol may declare themselves owner-final. The agent loop calls `assemble(context)` once per step, and `renderPrompt(assembly)` is the full system prompt the model sees. The plugin registers the harness-owned openers itself — the static `harness:identity` section and the deployment's `deployment:persona` section — so they exist for every agent regardless of which loop plugin drives it.
+System prompt assembly registry. Plugins contribute ordered text sections, tool-schema providers, and named prompt variables; contributions that implement required protocol may declare themselves owner-final. The agent loop calls `assemble(context)` once per step, and `renderPrompt(assembly)` is the full system prompt the model sees. The plugin registers the harness-owned openers itself — the static `harness:identity` section and the global default `deployment:persona` section — so they remain available regardless of which loop plugin drives an agent. An agent-scoped contribution with the same persona name shadows that default for its agent.
 
 ## Config
 
 | Key | Default | Meaning |
 |---|---|---|
-| `persona` | `''` | The deployment persona: the ONE deployment-authored prompt fragment, rendered as the order-0 `deployment:persona` section and shared by every agent in the context (subagents included). A template — complete `{{…}}` groups are interpreted strictly against the registered variables (the shipped loop registers `{{model}}`/`{{cwd}}`), with no escape syntax for literal braces yet. Empty ⇒ the section is dropped at render. |
+| `persona` | `''` | The global deployment-persona default: the ONE config-authored prompt fragment, rendered as the order-0 `deployment:persona` section unless an agent-scoped contribution shadows it. A template — complete `{{…}}` groups are interpreted strictly against the registered variables (the shipped loop registers `{{model}}`/`{{cwd}}`), with no escape syntax for literal braces yet. Empty ⇒ the section is dropped at render. |
 | `toolOrder` | — | Explicit model-facing tool order, as a list of `ToolSchema.name`s with one `'<unlisted-tools>'` rest entry (`TOOL_ORDER_REST`): listed tools take their listed position, unlisted tools land at the rest entry in lexicographic name order. Absent ⇒ plain lexicographic name order. Applied to the collected tools BEFORE the `system-prompt/assemble` waterfall — like the sections' `order` sort, it canonicalizes what the registry contributed (registration order is a plugin-load artifact), and a waterfall listener that mutates the list owns the determinism of what it emits. Misconfiguration fails loud: a list without exactly one rest entry, or with duplicates, throws at load; a listed name with no registered tool rejects every `assemble()`; a tool provider returning the reserved rest-entry name also rejects. Under the shipped loop the turn fails before any model request. Why a central list and not per-plugin weights: [Explicit model-facing tool order](../../../docs/rfc/implemented/feature/2026-07-06-explicit-tool-order.md). |
 
 ## Service: `SystemPrompt` (ctx key: `systemPrompt`)
@@ -41,7 +41,7 @@ Merge-extensible: plugins can declare extra fields on `PromptAssembly` and `Asse
 
 ### What is NOT here
 
-- Any deployment-authored prompt text outside config — the persona is this plugin's `persona` config, and every other section comes from the plugin that owns the fact. (The `harness:identity` line is deliberately a code literal: a harness fact, not a deployment choice; the `system-prompt/assemble` waterfall is the escape valve for a deployment that must drop it.)
+- Any end-user prompt-editing API — this plugin owns the config-authored global persona default, creator plugins may register agent-scoped shadows during setup, and every other section comes from the plugin that owns the fact. (The `harness:identity` line is deliberately a code literal: a harness fact, not a deployment choice; the `system-prompt/assemble` waterfall is the escape valve for a deployment that must drop it.)
 - Prompt compaction (belongs on the `agent/pre-step` seam in `dsh-agent`).
 
 Design rationale: [the prompt-variables RFC](../../../docs/rfc/implemented/architecture/2026-07-05-prompt-variables-and-tool-guidance-ownership.md).