review: the persona becomes the system-prompt plugin's deployment config

Review round 2 (tianyicui inline comments):

- dsh-system-prompt itself registers the harness:identity (-100) and
  deployment:persona (0) sections — they must survive a swapped loop
  plugin, so they leave dsh-agent-loop; the persona text is the plugin's
  own validated 'persona' config. The model/cwd variables STAY on the
  loop: runtime facts of the agents it drives.
- AgentOptions.systemPrompt is deleted with all its forwarding plumbing:
  the app configs' systemPrompt keys become 'persona' routed through
  dsh-agent-core (schema = z.intersect of the owners'), the ACP bridge
  and tool-subagent stop carrying persona configuration, and subagent
  children now render the deployment persona like every other agent.
- Example personas drop transport/interface trivia (ACP, CLI) — facts
  irrelevant to the model.
- Root CONTEXT.md removed (not idiomatic); its persona definition was
  wrong under the new ownership anyway.
- Docs, READMEs, the prompt-variables RFC, and generated catalogs
  updated; new loop test pins the assemble-waterfall escape valve
  (an emptied assembly sends NO system field).

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

@@ -107,9 +107,9 @@ export function startInProcessRun(
   const seedLength = options.seed?.length ?? 0
   const parentHeader = request.parent.session.header
   // Inherit the parent's model by default (a child with no model cannot run);
-  // an explicit `request.agentOptions.model` overrides it. The parent's
-  // systemPrompt is NOT inherited — a fresh child is a clean specialist unless
-  // the caller supplies one.
+  // an explicit `request.agentOptions.model` overrides it. The persona needs
+  // no inheritance: the deployment persona is a context-wide prompt section,
+  // so parent and child render the same one.
   const agentOptions: AgentOptions = {
     ...request.parent.options.model !== undefined ? { model: request.parent.options.model } : {},
     ...request.agentOptions,

packages/subagent/subagent-spawn/tests/harness.ts

@@ -23,7 +23,10 @@ export async function spawnHarness(workdir: string): Promise<Context> {
   const ctx = new Context()
   await ctx.plugin(LlmService)
   await ctx.plugin(SessionStore)
-  await ctx.plugin(SystemPrompt)
+  // The deployment persona is context-wide (parent AND spawned children
+  // render it), so it stays neutral for both roles; the delegation nudge
+  // lives in the e2e's user prompt and the subagent tool's own description.
+  await ctx.plugin(SystemPrompt, { persona: 'You are a coding agent. Report only when the requested work is done.' })
   await ctx.plugin(ToolRegistry)
   await ctx.plugin(AgentRegistry)
   await ctx.plugin(AgentLoop, { agents: [] })

packages/subagent/subagent-spawn/tests/spawn.e2e.ts

@@ -29,11 +29,7 @@ describe.skipIf(!process.env.DEEPSEEK_API_KEY)('spawn backend with-key smoke', (
   it('a parent delegates to a child that writes a file on disk', async () => {
     workdir = await mkdtemp(join(tmpdir(), 'dsh-subagent-spawn-e2e-'))
     ctx = await spawnHarness(workdir)
-    const parent = ctx.agentLoop.create(AgentId('e2e-parent'), {
-      model: 'deepseek-v4-flash',
-      systemPrompt: 'You are an orchestrator. To do file work, delegate to a subagent with the `subagent` tool — '
-        + 'give it a complete, standalone instruction. Report only when done.',
-    })
+    const parent = ctx.agentLoop.create(AgentId('e2e-parent'), { model: 'deepseek-v4-flash' })
 
     parent.send([{ type: 'text', text:
       'Use the subagent tool to delegate this exact task: "Use the bash tool to write the text '

packages/subagent/tool-subagent/README.md

@@ -14,7 +14,7 @@ The tool description and the `prompt` parameter description are DERIVED from the
 |---|---|
 | `provider` (required) | The `ctx.subagents` provider name to start runs on (`spawn`, `fork`, `acp`, …). |
 | `toolName` | The model-facing tool name to register (default `subagent`). Set a distinct value per load when exposing multiple providers, e.g. `subagent` + `subagent_acp`. |
-| `agentOptions` | Default per-child `{ model?, systemPrompt? }` applied to every spawned child. |
+| `agentOptions` | Default per-child `{ model? }` applied to every spawned child. (No per-child persona: the deployment persona is a context-wide section every agent shares.) |
 
 ## Lifecycle (synchronous collect)
 

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

@@ -53,8 +53,10 @@ export interface Config {
    */
   toolName?: string
   /**
-   * Default per-child agent options (model, system prompt) applied to every
-   * spawned child. Omitted fields fall back to the child loop's own defaults.
+   * Default per-child agent options (model) applied to every spawned child.
+   * Omitted fields fall back to the child loop's own defaults. There is no
+   * per-child persona: the deployment persona (the system-prompt plugin's
+   * `persona` config) is a context-wide section every agent shares.
    */
   agentOptions?: AgentOptions
 }
@@ -64,7 +66,6 @@ export const Config: z<Config> = z.object({
   toolName: z.string().default('subagent'),
   agentOptions: z.object({
     model: z.string(),
-    systemPrompt: z.string(),
   }),
 })
 

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

@@ -149,10 +149,10 @@ describe('dsh-tool-subagent', () => {
         }
       },
     })
-    await ctx.plugin(tool, { provider: 'capture', agentOptions: { model: 'child-model', systemPrompt: 'be terse' } })
+    await ctx.plugin(tool, { provider: 'capture', agentOptions: { model: 'child-model' } })
 
     await callSubagent(ctx, { description: 'd', prompt: 'p' })
-    expect(seen?.agentOptions).toEqual({ model: 'child-model', systemPrompt: 'be terse' })
+    expect(seen?.agentOptions).toEqual({ model: 'child-model' })
   })
 
   it('defaults toolName and omits agentOptions when apply() is called directly (schema bypass)', async () => {