Merge remote-tracking branch 'origin/master' into pr-265

# Conflicts:
#	docs/config-catalog.md
#	docs/cordis-catalog/services.md
#	docs/rfc/INDEX.md
#	examples/acp-agent/tests/snapshots/both-mode-turn/session.jsonl
#	examples/acp-agent/tests/snapshots/skill-load/session.jsonl
#	examples/acp-agent/tests/snapshots/text-turn/session.jsonl
#	examples/sandbox-acp-agent/tests/snapshots/escalation-approved/session.jsonl
#	examples/sandbox-acp-agent/tests/snapshots/escalation-rejected/session.jsonl
#	packages/core/agent-loop/README.md
#	packages/core/agent-loop/src/loop.ts
#	packages/core/tools/README.md
#	packages/core/tools/src/index.ts
#	packages/core/tools/src/schema.ts
#	packages/ui/acp/src/index.ts
#	packages/ui/stdio-agent/README.md

packages/subagent/tool-subagent/README.md

@@ -30,3 +30,41 @@ A non-`completed` stop reason becomes an `isError` tool result; partial child ou
 The tool declares `isConcurrencySafe: () => true`: each call starts an independent child run and returns only its final answer, touching no parent-agent state, and `SubagentProvider.start()` is contractually concurrent-safe for independent runs (see [subagent/](../README.md)). So the agent loop may run several `subagent` calls from one assistant step in parallel, and the tool description tells the model it may issue independent tasks together when their work scopes do not overlap. The subagent tool stays synchronous (one result = the child's final answer); background spawning + later collection is separate future work.
 
 `toolFilter` changes the child's visible global tool layer; it is not a parent-derived authority ceiling. See the [agent-scope security non-goal](../../../docs/rfc/implemented/architecture/2026-07-08-agent-scope-contexts.md#security-and-authority-are-explicit-non-goals).
+
+## Model Experience
+
+### Standalone-provider schema
+
+**What the model sees**: While a fresh-context provider exists, the configured tool uses the generated default [`subagent` schema](../../../docs/tool-catalog.md#deepseek-aidsh-tool-subagent); the catalog also records how `toolName` changes the visible name.
+
+**Token effect**: Fixed schema cost per parent request while mounted. Removing the provider removes the whole schema.
+
+### Inherited-context-provider schema
+
+**What the model sees**: Relative to the generated default [`subagent` schema](../../../docs/tool-catalog.md#deepseek-aidsh-tool-subagent), a provider that seeds completed turns replaces only the tool and `prompt` parameter descriptions with the text below; the shape and `description` parameter stay unchanged.
+
+**Token effect**: Fixed schema cost per parent request while mounted. Exposing multiple providers adds one independently named schema per load.
+
+#### Inherited-context-provider tool description
+
+```markdown
+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. You may issue several subagent calls in one message to run independent tasks concurrently when their work scopes do not overlap.
+```
+
+#### Inherited-context-provider prompt description
+
+```markdown
+The task for the subagent. It already sees this conversation's completed turns, so build on them freely and state only what is new.
+```
+
+### Tool-call history and result
+
+**What the model sees**: The task description and full prompt remain in the parent assistant tool call. Success contains only the child's data-dependent final text. Other stop reasons become exactly `Error: subagent run was cancelled`, `Error: subagent run failed`, `Error: subagent run hit its token limit before finishing`, `Error: subagent declined the task`, or `Error: subagent run ended abnormally (<reason>)`; a call without an owning agent becomes `Error: subagent tool requires a calling agent (exec.agent was undefined)`. Intermediate child steps never enter the parent.
+
+**Token effect**: Prompt and final output are data-dependent retained tokens. All child working context is paid in the child and omitted from the parent.
+
+## Known Limitations and Deferred Work
+
+- **Delegation blocks the parent turn** — synchronous collect only; background start and poll collection are deferred to the long-running-runtime redesign.
+- **Duplicate `toolName` across waiting loads is detected late** (`TODO(subagent-dup-toolname)`) — two loads waiting on providers collide only when a provider arrives, and the throw rolls back the provider's fiber rather than the misconfigured tool's; config-time detection needs a cross-fiber registry of intended names.
+- **Child policy is fixed per tool registration** — `model`, persona, tool filter, and depth cap come from this plugin load's config, not model-call arguments; exposing another policy requires another distinctly named tool.

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

@@ -1,34 +1,11 @@
 /**
- * The model-facing `subagent` tool: delegate a task to a child agent and return
- * its final output. Pure schema + lifecycle shaping — every transport concern
- * lives behind the `ctx.subagents` provider registry
- * (`@deepseek-ai/dsh-subagent`), so an in-process, ACP, or future A2A backend
- * swaps in without touching what the model sees.
- *
- * Provider selection is config, not model-facing: this plugin is bound to
- * EXACTLY ONE provider name (`Config.provider`). To expose more than one
- * transport, load the plugin more than once, each bound to a different provider
- * — there is no provider/type parameter in the model-facing schema. The model
- * sees only `{ description, prompt }`.
- *
- * The tool DESCRIPTION is derived from the bound provider's conversation-history
- * descriptor ({@link providerWording}): a fresh-conversation provider (spawn,
- * ACP) gets the standalone-prompt wording, while a seeded-conversation provider
- * (fork) tells the model the child already sees the conversation's completed
- * turns. This descriptor says nothing about Cordis scope, services, tools, or
- * authority. The tool MIRRORS the
- * provider's lifecycle via `subagent/provider-added`/`-removed` — it registers
- * when the provider is (or becomes) available and unregisters when the
- * provider goes away — so no load-order requirement exists and an HMR reload
- * of the backend re-derives the wording from the fresh provider.
- *
- * Collection is SYNCHRONOUS this cut: `execute` starts a run and awaits
- * `run.result` inside a `try/finally` that always disposes the run, so the
- * owned child agent/session is torn down on every path (success, error, abort)
- * and never leaks as a live idle child. A non-`completed` stop reason maps to an
- * `isError` tool result (by throwing) rather than returning partial output as
- * success.
+ * Model-facing delegation tool bound by configuration to one provider; transport selection is not
+ * exposed in its `{ description, prompt }` schema. Provider lifecycle controls registration and
+ * re-derives conversation-history wording after reload, so load order is irrelevant.
  *
+ * Execution synchronously awaits the child result and always disposes the run. Non-completed stop
+ * reasons become error results, while transport details remain behind `ctx.subagents`. Load this
+ * plugin more than once to expose multiple configured providers.
  * @module @deepseek-ai/dsh-tool-subagent
  */
 
@@ -105,16 +82,8 @@ export const Config: z<Config> = z.object({
     model: z.string(),
   }).default(undefined as unknown as { model: string }),
   persona: z.string(),
-  // A schemastery object materializes {} (with [] for nested arrays) when the
-  // key is omitted — for toolFilter that would mean an EMPTY ALLOW-LIST, i.e.
-  // deny-everything, silently. Force the omitted key to stay absent (the same
-  // shape discipline as SystemPrompt's toolOrder); the cast is needed because
-  // .default() expects the object type.
-  // The NESTED arrays get the same treatment as the object itself: a partial
-  // filter ({deny: […]}) must not materialize allow: [] beside it — an empty
-  // allow-list means deny-EVERYTHING, so the materialized default would turn
-  // a deny-one config into deny-all. An EXPLICIT allow: [] (grant-only
-  // children) survives, since only the omitted key defaults to undefined.
+  // Schemastery otherwise materializes omitted objects and nested arrays as `{ allow: [] }`, which
+  // silently means deny all. Preserve omission while retaining an explicit empty allow-list.
   toolFilter: z.object({
     allow: z.array(z.string()).default(undefined as unknown as string[]),
     deny: z.array(z.string()).default(undefined as unknown as string[]),
@@ -298,7 +267,7 @@ export function apply(ctx: Context, config: Config): void {
   if (present !== undefined) {
     mount(present)
   } else {
-    // Not an error: the backend's fiber may simply activate after this one.
+    // Not an error: the backend's fiber may activate after this one.
     // The tool appears the moment the provider registers; a typo'd provider
     // name shows up as this note plus a tool that never materializes.
     ctx.logger.info(`subagent provider "${config.provider}" not registered yet; the "${config.toolName ?? 'subagent'}" tool will register when it appears`)