fix(cli): Recover sessions across archive races

docs/e2e-tests/worktree-phase-d.md

@@ -168,7 +168,7 @@ or "git init".
 ### B1: sidecar written with all six fields
 
 ```bash
-SESSION_ID=$(uuidgen)
+SESSION_ID=$(uuidgen | tr '[:upper:]' '[:lower:]')
 $QWEN --worktree b1-test --session-id "$SESSION_ID" "say hi" \
   --approval-mode yolo --output-format json 2>/dev/null > /tmp/b1.out
 
@@ -220,7 +220,7 @@ is inside the worktree.
 
 ```bash
 # Run 1: create a session with worktree "first"
-SESSION_ID=$(uuidgen)
+SESSION_ID=$(uuidgen | tr '[:upper:]' '[:lower:]')
 $QWEN --worktree first --session-id "$SESSION_ID" "say hi" \
   --approval-mode yolo --output-format json 2>/dev/null > /tmp/c1-run1.out
 
@@ -246,7 +246,7 @@ ls -d "$TEST_DIR/.qwen/worktrees/"*
 ### C2: stale sidecar (manually deleted dir) + `--worktree` → fresh worktree
 
 ```bash
-SESSION_ID=$(uuidgen)
+SESSION_ID=$(uuidgen | tr '[:upper:]' '[:lower:]')
 $QWEN --worktree c2 --session-id "$SESSION_ID" "say hi" \
   --approval-mode yolo --output-format json 2>/dev/null > /tmp/c2-run1.out
 
@@ -312,7 +312,7 @@ tmux kill-session -t d2
 ### D3: Dialog → Remove → worktree + branch + sidecar all gone
 
 ```bash
-SESSION_ID=$(uuidgen)
+SESSION_ID=$(uuidgen | tr '[:upper:]' '[:lower:]')
 tmux new-session -d -s d3 -x 200 -y 50 \
   "cd $TEST_DIR && $QWEN --worktree d3-test --session-id $SESSION_ID --approval-mode yolo"
 sleep 3
@@ -541,7 +541,7 @@ readlink "$TEST_DIR/.qwen/worktrees/pr-4174/node_modules"
 > the dry-run, or skip G1 entirely in baseline mode.
 
 ```bash
-SESSION_ID=$(uuidgen)
+SESSION_ID=$(uuidgen | tr '[:upper:]' '[:lower:]')
 tmux new-session -d -s g1 -x 200 -y 50 \
   "cd $TEST_DIR && $QWEN --worktree g1-test --session-id $SESSION_ID --approval-mode yolo 2>&1 | tee /tmp/g1-stderr.out"
 sleep 3

integration-tests/cli/qwen-serve-routes.test.ts

@@ -481,7 +481,7 @@ describe('qwen serve — transcript paging route', () => {
     expect(missing.status).toBe(404);
   });
 
-  it('maps archived, conflicting, and unavailable transcript snapshots to 409', async () => {
+  it('reads exact conflicts from active and maps archived/unavailable snapshots to 409', async () => {
     const archivedId = '99999999-aaaa-bbbb-cccc-444444444444';
     const archivedRecord = chatRecord(
       archivedId,
@@ -497,19 +497,33 @@ describe('qwen serve — transcript paging route', () => {
     });
 
     const conflictId = '99999999-aaaa-bbbb-cccc-555555555555';
-    const conflictRecord = chatRecord(
+    const activeConflictRecord = chatRecord(
       conflictId,
       'u1',
       null,
-      'conflicting transcript',
+      'active conflicting transcript',
     );
-    writePersistedTranscript(conflictId, [conflictRecord]);
-    writePersistedTranscript(conflictId, [conflictRecord], 'archived');
+    const archivedConflictRecord = chatRecord(
+      conflictId,
+      'u1',
+      null,
+      'archived conflicting transcript',
+    );
+    writePersistedTranscript(conflictId, [activeConflictRecord]);
+    writePersistedTranscript(conflictId, [archivedConflictRecord], 'archived');
     const conflict = await getTranscript(conflictId);
-    expect(conflict.status).toBe(409);
-    await expect(conflict.json()).resolves.toMatchObject({
-      code: 'session_conflict',
+    expect(conflict.status).toBe(200);
+    const conflictBody = await conflict.json();
+    expect(conflictBody).toMatchObject({
+      sessionId: conflictId,
+      hasMore: false,
     });
+    expect(JSON.stringify(conflictBody)).toContain(
+      'active conflicting transcript',
+    );
+    expect(JSON.stringify(conflictBody)).not.toContain(
+      'archived conflicting transcript',
+    );
 
     const unavailable = await getTranscript(
       '99999999-aaaa-bbbb-cccc-666666666666',

packages/cli/src/acp-integration/acpAgent.test.ts

@@ -17056,6 +17056,36 @@ describe('QwenAgent loadSession / unstable_resumeSession', () => {
     },
   );
 
+  it.each(['load', 'resume'] as const)(
+    '%s restores an exact persisted session from active when both states exist',
+    async (action) => {
+      const sessionId = '550e8400-e29b-41d4-a716-446655440001';
+      const innerConfig = bindRestoreMocks({
+        sessionExists: false,
+        resolverError: new SessionIdCaseConflictError(sessionId, sessionId),
+      });
+      innerConfig.getSessionId.mockReturnValue(sessionId);
+      const { agent, agentPromise } = await spawnAgent();
+
+      try {
+        const request = { cwd: '/tmp', sessionId, mcpServers: [] };
+        if (action === 'load') {
+          await agent.loadSession(request);
+        } else {
+          await agent.unstable_resumeSession(request);
+        }
+
+        const argv = vi.mocked(loadCliConfig).mock.calls.at(-1)?.[1] as
+          | CliArgs
+          | undefined;
+        expect(argv?.resume).toBe(sessionId);
+      } finally {
+        mockConnectionState.resolve();
+        await agentPromise;
+      }
+    },
+  );
+
   it.each(['load', 'resume'] as const)(
     '%s surfaces the both-states conflict message as session_conflict',
     async (action) => {

packages/cli/src/acp-integration/acpAgent.ts

@@ -870,6 +870,30 @@ const RESUME_RESTORE_OPTIONS: SelectiveSessionRestoreOptions = {
   replay: { kind: 'none' },
 };
 
+async function resolvePersistedSessionIdForRestore(
+  sessionService: SessionService,
+  sessionId: string,
+): Promise<string | undefined> {
+  try {
+    return await sessionService.findSessionIdIgnoringCase(sessionId);
+  } catch (error) {
+    if (
+      error instanceof SessionIdCaseConflictError &&
+      error.reason === 'case_conflict' &&
+      error.candidateSessionId === sessionId
+    ) {
+      return sessionId;
+    }
+    if (error instanceof SessionIdCaseConflictError) {
+      throw RequestError.internalError(
+        { errorKind: 'session_conflict', sessionId },
+        error.message,
+      );
+    }
+    throw error;
+  }
+}
+
 function mapSessionRestoreRequestError(
   error: unknown,
   sessionId: string,
@@ -5411,21 +5435,7 @@ class QwenAgent implements Agent {
       const persistedSessionId = await profiler.time('existence_check', () =>
         this.runWithPinnedRuntimeBaseDir(settings, params.cwd, async () => {
           const sessionService = new SessionService(params.cwd);
-          try {
-            return await sessionService.findSessionIdIgnoringCase(sessionId);
-          } catch (error) {
-            if (error instanceof SessionIdCaseConflictError) {
-              // Parity with the daemon surfaces (toRpcError / REST 409):
-              // persisted-storage conflicts use `session_conflict`;
-              // `session_id_conflict` is reserved for live-id admission
-              // occupancy.
-              throw RequestError.internalError(
-                { errorKind: 'session_conflict', sessionId },
-                error.message,
-              );
-            }
-            throw error;
-          }
+          return resolvePersistedSessionIdForRestore(sessionService, sessionId);
         }),
       );
       if (!persistedSessionId) {
@@ -5740,21 +5750,7 @@ class QwenAgent implements Agent {
       const persistedSessionId = await profiler.time('existence_check', () =>
         this.runWithPinnedRuntimeBaseDir(settings, params.cwd, async () => {
           const sessionService = new SessionService(params.cwd);
-          try {
-            return await sessionService.findSessionIdIgnoringCase(sessionId);
-          } catch (error) {
-            if (error instanceof SessionIdCaseConflictError) {
-              // Parity with the daemon surfaces (toRpcError / REST 409):
-              // persisted-storage conflicts use `session_conflict`;
-              // `session_id_conflict` is reserved for live-id admission
-              // occupancy.
-              throw RequestError.internalError(
-                { errorKind: 'session_conflict', sessionId },
-                error.message,
-              );
-            }
-            throw error;
-          }
+          return resolvePersistedSessionIdForRestore(sessionService, sessionId);
         }),
       );
       if (!persistedSessionId) {