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

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

@@ -1,6 +1,6 @@
 import { describe, expect, expectTypeOf, it, vi } from 'vitest'
 import { Context } from 'cordis'
-import { CallId } from '@deepseek-ai/dsh-llm'
+import { CallId, ReasoningEffortId } from '@deepseek-ai/dsh-llm'
 import SessionStore, {
   findLastMessageTurnEnd,
   SESSION_FORMAT_VERSION,
@@ -192,6 +192,35 @@ describe('Session', () => {
       .toEqual([unrelatedPrimitiveData])
   })
 
+  it('round-trips a non-empty reasoning effort and rejects invalid durable values', () => {
+    const valid = {
+      type: 'request/header',
+      seq: 0,
+      time: 1,
+      data: {
+        header: {
+          config: {
+            provider: 'mock',
+            model: 'model',
+            reasoningEffort: ReasoningEffortId('adapter-owned'),
+          },
+        },
+        reason: 'initial',
+      },
+    } as const
+    expect(new Session(SessionId('reasoning-effort'), [valid]).events[0])
+      .toEqual(valid)
+
+    for (const reasoningEffort of ['', 1]) {
+      const invalid = structuredClone(valid) as unknown as SessionEvent
+      if (invalid.type !== 'request/header') throw new Error('test fixture must be a request header')
+      const config = invalid.data.header.config as unknown as Record<string, unknown>
+      config.reasoningEffort = reasoningEffort
+      expect(() => new Session(SessionId('invalid-reasoning-effort'), [invalid]))
+        .toThrow('seed request/header at index 0 has an invalid reasoningEffort')
+    }
+  })
+
   it('isolates the log from mutation through a derived message (append-only contract)', () => {
     const session = new Session(SessionId('s4'))
     session.append('user/message', { content: [{ type: 'text', text: 'original' }], source: { kind: 'user' } }, { surfaceOp: 'append' })