fix: scope observation to current turn

Require assistant natural language after the latest user message so a completed prompt cannot reuse historical replies when queuing the observation snapshot.

.project-docs/30-worklog/tasks/20260824-pi-remove-opencode-a41c9e72.md

@@ -120,13 +120,14 @@
   noise remains.
 - `pnpm run typecheck`: passed, including after the pinned-pnpm dependency rebuild.
 - `pnpm exec eslint . --quiet`: passed.
-- Full unit suite after planner fixes: 174 files passed; 1495 tests passed,
-  2 skipped (1497 total).
+- Full unit suite after planner fixes: 174 files passed; 1496 tests passed,
+  2 skipped (1498 total).
 - Pressure suite: 1 file and 1 test passed.
-- Focused post-review suite: 3 files and 33 tests passed for migration,
+- Focused post-review suite: 3 files and 34 tests passed for migration,
   session-observation sync, and Conversation store settlement behavior. It covers
   valid-v2 no-legacy-read, unknown/modified Agent backup, live ordinary-prompt
-  settlement, no hydrate/follow-up replay, and assistant-natural-language gating.
+  settlement, no hydrate/follow-up replay, and current-turn assistant natural-
+  language gating that cannot reuse an older assistant reply.
 - Electron E2E: 3 tests passed for first Pi conversation latency/submit ordering,
   Pi product UI, and bundled Skill project configuration.
 - `pnpm run build:vite`: passed (Renderer, Electron Main, Preload, and utility).

src/lib/agent-session-sync.ts

@@ -363,8 +363,22 @@ export function queueAgentSessionSync(
 
 /** Queue the final product Conversation snapshot after a completed prompt turn. */
 export function queueCodingConversationSessionSync(snapshot: ConversationSnapshot): void {
-  const messages: RawMessage[] = snapshot.nodes.flatMap((node) => {
-    if (node.kind !== 'message') return [];
+  const messageNodes = snapshot.nodes.filter((node) => node.kind === 'message');
+  let lastUserIndex = -1;
+  for (let index = messageNodes.length - 1; index >= 0; index -= 1) {
+    if (messageNodes[index].role === 'user') {
+      lastUserIndex = index;
+      break;
+    }
+  }
+  if (lastUserIndex < 0) return;
+  const currentTurnAssistantIds = new Set(messageNodes
+    .slice(lastUserIndex + 1)
+    .filter((node) => node.role === 'assistant')
+    .map((node) => node.id));
+  if (currentTurnAssistantIds.size === 0) return;
+
+  const messages: RawMessage[] = messageNodes.flatMap((node) => {
     return [{
       id: node.id,
       role: node.role,
@@ -384,7 +398,11 @@ export function queueCodingConversationSessionSync(snapshot: ConversationSnapsho
     messages,
     updatedAt,
   );
-  if (!data?.messages.some((message) => message.role === 'assistant')) return;
+  if (!data?.messages.some((message) => (
+    message.role === 'assistant'
+    && typeof message.id === 'string'
+    && currentTurnAssistantIds.has(message.id)
+  ))) return;
   queueAgentSessionData(data);
 }
 

tests/unit/agent-session-sync.test.ts

@@ -220,6 +220,45 @@ describe('local Agent session sync', () => {
     expect(pushSessionDataMock).not.toHaveBeenCalled();
   });
 
+  it('does not reuse an older assistant reply when the current turn has no reply', async () => {
+    const base = createProductSnapshot('conversation-1');
+    queueCodingConversationSessionSync({
+      ...base,
+      nodes: [
+        {
+          kind: 'message',
+          id: 'old-user',
+          role: 'user',
+          status: 'complete',
+          blocks: [{ kind: 'text', id: 'old-question', text: '旧问题', status: 'complete' }],
+        },
+        {
+          kind: 'message',
+          id: 'old-assistant',
+          role: 'assistant',
+          status: 'complete',
+          blocks: [{ kind: 'text', id: 'old-answer', text: '旧回答', status: 'complete' }],
+        },
+        {
+          kind: 'message',
+          id: 'current-user',
+          role: 'user',
+          status: 'complete',
+          blocks: [{ kind: 'text', id: 'current-question', text: '新问题', status: 'complete' }],
+        },
+      ],
+      run: {
+        status: 'idle',
+        runId: 'run-2',
+        settledAt: Date.parse('2026-08-24T08:01:00.000Z'),
+        terminalReason: 'completed',
+      },
+    });
+    await flushPendingAgentSessionSync();
+
+    expect(pushSessionDataMock).not.toHaveBeenCalled();
+  });
+
   it('never uploads a pending snapshot under a different authenticated account', async () => {
     queueAgentSessionSync('prj_1', 'ses_1', [
       { id: 'user-1', role: 'user', content: '账号 A 的问题' },