Merge remote-tracking branch 'origin/master' into xtr/agent-loop-message-machine

# Conflicts:
#	docs/architecture.i18n.yaml
#	docs/architecture.md
#	docs/architecture.zh.md
#	docs/cordis-catalog/services.md
#	docs/core-data-structures/core.i18n.yaml
#	docs/core-data-structures/core.md
#	docs/core-data-structures/core.zh.md
#	docs/core-data-structures/llm-streaming.i18n.yaml
#	docs/core-data-structures/session.i18n.yaml
#	docs/event-producer-consumer.md
#	examples/acp-agent/tests/snapshots/cordis-inspect-jsdoc/session.jsonl
#	examples/headless-agent/tests/snapshots/advanced-toolchain/session.1.jsonl
#	examples/headless-agent/tests/snapshots/advanced-toolchain/session.2.jsonl
#	packages/core/agent-loop/README.i18n.yaml
#	packages/core/agent-loop/README.md
#	packages/core/agent-loop/README.zh.md
#	packages/core/agent-loop/src/loop.ts
#	packages/core/agent/README.i18n.yaml
#	packages/core/agent/tests/llm-target.spec.ts
#	packages/core/session/tests/request-header.spec.ts

docs/core-data-structures/core.md

@@ -199,7 +199,7 @@ interface LlmModelInfo {
 }
 ```
 
-Correctness-sensitive model capacity is queried separately from the advisory catalog and is owned by the adapter serving the exact route.
+Correctness-sensitive metadata is resolved separately from the advisory catalog and is owned by the adapter serving the exact route. Context capacity and reasoning choices share one exact-model result so consumers do not repeat authoritative model resolution.
 
 ```ts type-equiv
 /** Provider-owned context capacity for one exact provider/model route. */
@@ -209,12 +209,56 @@ interface LlmModelContext {
 }
 ```
 
+Reasoning effort is another exact-route capability. The core brands identifiers but does not enumerate their values; each adapter owns the ordered set, display names, and optional deployment default.
+
+```ts type-equiv
+/** Adapter-owned identifier for one model's selectable reasoning effort. */
+type ReasoningEffortId = Branded<'ReasoningEffortId'>
+```
+
+```ts type-equiv
+/** Display metadata for one adapter-owned reasoning effort. */
+interface LlmReasoningEffortInfo {
+  /** Opaque stable value accepted by {@link GenerateOptions.reasoningEffort}. */
+  id: ReasoningEffortId
+  /** Human-readable effort name for selectors and diagnostics. */
+  name: string
+  /** Optional user-facing distinction from otherwise similar efforts. */
+  description?: string
+}
+```
+
+```ts type-equiv
+/** Selectable reasoning efforts for one exact provider/model route. */
+interface LlmModelReasoningInfo {
+  /** Supported efforts in adapter-preferred display order. */
+  efforts: readonly LlmReasoningEffortInfo[]
+  /**
+   * Adapter-configured default materialized into requests when callers omit
+   * an effort. Absence preserves the provider's own default.
+   */
+  defaultEffort?: ReasoningEffortId
+}
+```
+
+```ts type-equiv
+/** Exact-route model metadata resolved by its owning adapter. */
+interface LlmResolvedModelInfo extends LlmModelInfo {
+  /** Provider-owned context capacity when known. */
+  context?: LlmModelContext
+  /** Adapter-owned selectable reasoning levels when exposed. */
+  reasoning?: LlmModelReasoningInfo
+}
+```
+
 ```ts type-equiv
 /** A single model request, fully assembled. */
 interface GenerateOptions {
   /** Registered provider route selecting the adapter instance. */
   provider: string
   model: string
+  /** Adapter-owned reasoning effort selected for this exact model. */
+  reasoningEffort?: ReasoningEffortId
   /**
    * Ordered conversation messages, exactly as the provider sees them (after
    * the `system` slot). A loop-built request assembles them as
@@ -290,21 +334,23 @@ The model-facing `ToolSchema` is the wire shape; the registered `ToolDefinition`
 
 The loop builds each request from logged state. `EpochHeader` records call config, rendered prompt, and authoritative returned tool order (configured by `toolOrder`, or lexicographic when unset) through full `request/header` snapshots. Together with derived history, this makes the request reconstructable from the session log. See [session.md](session.md#the-request-header-event-requestheader) and the [reconstructability Agent Note](../../.agents/notes/implemented/architecture/2026-07-05-reconstructable-requests.md).
 
-`agent/request` receives a frozen call-config seed and may return a replacement to switch provider, model, or sampling. Requests reaching `llm/stream` are deep-frozen, so mutation throws, and carry a process-local loop identity so observers do not confuse separately logged frozen auxiliary calls with conversation requests.
+`agent/request` receives a frozen call-config seed and may return a replacement to switch provider, model, reasoning effort, or sampling. After the waterfall, the loop prepares the exact model capability under the turn signal, rejects unsupported explicit effort ids without clamping, materializes an adapter-configured default, and logs the effective value. The prepared call keeps one adapter registration through dispatch. Requests reaching `llm/stream` are deep-frozen, so mutation throws, and carry a process-local loop identity so observers do not confuse separately logged frozen auxiliary calls with conversation requests.
 
 On the wire, a loop-built request reads the `system` slot (the rendered prompt assembly) followed by the derived history — the boundary snapshot, whose tail is the newest `user/message` on a turn's first step and the previous step's tool results on later steps. The dev invariant recomputes exactly this equation against every loop-built request.
 
-FIXME(call-config-shape): revisit the exact definition of this type — which fields are genuinely epoch-level for cache purposes (`model` certainly; the sampling scalars sit here out of caution), and where provider-specific extras (reasoning options, extra body params) belong when an adapter needs them.
+FIXME(call-config-shape): revisit which remaining fields are genuinely epoch-level for cache purposes (`model` and the model-owned reasoning effort are explicit; the sampling scalars sit here out of caution).
 
 ```ts type-equiv
 /**
- * Provider + model + sampling scalars of one conversation's requests. Every field maps
- * 1:1 onto the same-named `GenerateOptions` field; the loop builds requests
- * from the logged header rather than accepting these per call.
+ * Provider, model, reasoning effort, and sampling scalars of one conversation's
+ * requests. Every field maps 1:1 onto the same-named `GenerateOptions` field;
+ * the loop builds requests from the logged header rather than accepting these
+ * per call.
  */
 interface LlmCallConfig {
   provider: string
   model: string
+  reasoningEffort?: ReasoningEffortId
   temperature?: number
   maxTokens?: number
   stop?: string[]