fix(rewind): close slash-command, compression, and IDE bypass holes

Three bugs found by Codex review:

1. P1: `/rewind` slash command bypassed the IDE-mode guard because
   `slashCommandActions.openRewindSelector` called `setIsRewindSelectorOpen`
   directly. Fixed by introducing a ref bridge (`openRewindSelectorRef`)
   that delegates to the guarded callback.

2. P1: Slash-command invocations (`/help`, `/stats`, etc.) are stored as
   `type: 'user'` in UI history but never reach the API or recording
   service. The turn-index counter in `handleRewindConfirm` and
   `computeApiTruncationIndex` counted them, producing off-by-N errors.
   Added `isRealUserTurn()` helper that excludes items starting with
   `/` or `?`, applied in all three counting sites (AppContainer,
   historyMapping, RewindSelector).

3. P2: After chat compression, `computeApiTruncationIndex` returned
   `apiHistory.length` when the target turn was unreachable, silently
   keeping the full API history while the UI was truncated. Changed to
   return `-1`; `handleRewindConfirm` now aborts with an error message
   when the target turn was absorbed by compression.

Tests: 14 unit tests for historyMapping (including slash-command and
compression cases), full suite 616/616 passed.

🤖 Generated with [Qwen Code](https://github.com/QwenLM/qwen-code)

packages/cli/src/ui/AppContainer.tsx

@@ -75,7 +75,10 @@ import { useResumeCommand } from './hooks/useResumeCommand.js';
 import { useDeleteCommand } from './hooks/useDeleteCommand.js';
 import { useSlashCommandProcessor } from './hooks/slashCommandProcessor.js';
 import { useDoublePress } from './hooks/useDoublePress.js';
-import { computeApiTruncationIndex } from './utils/historyMapping.js';
+import {
+  computeApiTruncationIndex,
+  isRealUserTurn,
+} from './utils/historyMapping.js';
 import { useVimMode } from './contexts/VimModeContext.js';
 import { CompactModeProvider } from './contexts/CompactModeContext.js';
 import { useTerminalSize } from './hooks/useTerminalSize.js';
@@ -634,6 +637,12 @@ export const AppContainer = (props: AppContainerProps) => {
   const { isHooksDialogOpen, openHooksDialog, closeHooksDialog } =
     useHooksDialog();
 
+  // Ref bridge: the guarded openRewindSelector callback is defined later
+  // (after useDoublePress), but slashCommandActions needs it now. The ref
+  // lets the useMemo capture a stable function pointer whose implementation
+  // is swapped in once the real callback exists.
+  const openRewindSelectorRef = useRef<() => void>(() => {});
+
   const slashCommandActions = useMemo(
     () => ({
       openAuthDialog,
@@ -662,7 +671,7 @@ export const AppContainer = (props: AppContainerProps) => {
       openMcpDialog,
       openHooksDialog,
       openResumeDialog,
-      openRewindSelector: () => setIsRewindSelectorOpen(true),
+      openRewindSelector: () => openRewindSelectorRef.current(),
       handleResume,
       openDeleteDialog,
     }),
@@ -1591,6 +1600,7 @@ export const AppContainer = (props: AppContainerProps) => {
     if (!hasUserTurns) return;
     setIsRewindSelectorOpen(true);
   }, [streamingState, config, historyManager.history]);
+  openRewindSelectorRef.current = openRewindSelector;
 
   const closeRewindSelector = useCallback(() => {
     setIsRewindSelectorOpen(false);
@@ -1608,7 +1618,7 @@ export const AppContainer = (props: AppContainerProps) => {
       let targetTurnIndex = 0;
       for (const h of originalHistory) {
         if (h.id === userItem.id) break;
-        if (h.type === 'user') targetTurnIndex++;
+        if (isRealUserTurn(h)) targetTurnIndex++;
       }
 
       // 2. Compute API truncation point
@@ -1619,6 +1629,19 @@ export const AppContainer = (props: AppContainerProps) => {
         apiHistory,
       );
 
+      // Abort if the target turn is unreachable (e.g., absorbed by compression)
+      if (apiTruncateIndex < 0) {
+        historyManager.addItem(
+          {
+            type: 'error',
+            text: 'Cannot rewind to a turn that was compressed. Try a more recent turn.',
+          },
+          Date.now(),
+        );
+        setIsRewindSelectorOpen(false);
+        return;
+      }
+
       // 3. Truncate API history and strip stale thinking blocks
       geminiClient.truncateHistory(apiTruncateIndex);
       geminiClient.stripThoughtsFromHistory();

packages/cli/src/ui/components/RewindSelector.tsx

@@ -11,6 +11,7 @@ import { theme } from '../semantic-colors.js';
 import { useTerminalSize } from '../hooks/useTerminalSize.js';
 import { useKeypress } from '../hooks/useKeypress.js';
 import { truncateText } from '../utils/sessionPickerUtils.js';
+import { isRealUserTurn } from '../utils/historyMapping.js';
 import { t } from '../../i18n/index.js';
 
 export interface RewindSelectorProps {
@@ -25,7 +26,7 @@ const MAX_VISIBLE_ITEMS = 7;
  * Extract user-type items from UI history for the rewind pick list.
  */
 function getUserTurns(history: HistoryItem[]): HistoryItem[] {
-  return history.filter((item) => item.type === 'user');
+  return history.filter(isRealUserTurn);
 }
 
 interface TurnItemViewProps {

packages/cli/src/ui/utils/historyMapping.test.ts

@@ -5,7 +5,7 @@
  */
 
 import { describe, it, expect } from 'vitest';
-import { computeApiTruncationIndex } from './historyMapping.js';
+import { computeApiTruncationIndex, isRealUserTurn } from './historyMapping.js';
 import type { HistoryItem } from '../types.js';
 import type { Content, Part } from '@google/genai';
 
@@ -169,7 +169,7 @@ describe('computeApiTruncationIndex', () => {
   });
 
   describe('compression fallback', () => {
-    it('returns apiHistory.length when not enough user prompts found', () => {
+    it('returns -1 when not enough user prompts found', () => {
       const ui: HistoryItem[] = [
         userItem(1),
         geminiItem(2),
@@ -185,7 +185,28 @@ describe('computeApiTruncationIndex', () => {
         modelContent('response 5'),
       ];
       // Rewind to turn 5 → 2 user turns before it, but API only has 1 user text
-      expect(computeApiTruncationIndex(ui, 5, api)).toBe(api.length);
+      expect(computeApiTruncationIndex(ui, 5, api)).toBe(-1);
+    });
+  });
+
+  describe('with slash-command items in UI history', () => {
+    it('ignores slash-command items when counting user turns', () => {
+      const ui: HistoryItem[] = [
+        userItem(1, 'hello'),
+        geminiItem(2),
+        userItem(3, '/help'), // slash command — should be skipped
+        userItem(5, 'world'),
+        geminiItem(6),
+      ];
+      const api: Content[] = [
+        userContent('hello'),
+        modelContent('response 1'),
+        userContent('world'),
+        modelContent('response 2'),
+      ];
+      // Rewind to 'world' (id=5): 1 real user turn before it (id=1)
+      // Slash '/help' (id=3) should not be counted
+      expect(computeApiTruncationIndex(ui, 5, api)).toBe(2);
     });
   });
 
@@ -200,3 +221,23 @@ describe('computeApiTruncationIndex', () => {
     });
   });
 });
+
+describe('isRealUserTurn', () => {
+  it('returns true for normal user prompts', () => {
+    expect(isRealUserTurn(userItem(1, 'hello world'))).toBe(true);
+  });
+
+  it('returns false for slash commands', () => {
+    expect(isRealUserTurn(userItem(1, '/help'))).toBe(false);
+    expect(isRealUserTurn(userItem(1, '/rewind'))).toBe(false);
+    expect(isRealUserTurn(userItem(1, '/stats'))).toBe(false);
+  });
+
+  it('returns false for ? commands', () => {
+    expect(isRealUserTurn(userItem(1, '?help'))).toBe(false);
+  });
+
+  it('returns false for non-user items', () => {
+    expect(isRealUserTurn(geminiItem(1))).toBe(false);
+  });
+});

packages/cli/src/ui/utils/historyMapping.ts

@@ -7,6 +7,17 @@
 import type { HistoryItem } from '../types.js';
 import type { Content } from '@google/genai';
 
+/**
+ * Returns true when the history item represents a real user prompt that was
+ * sent to the model, as opposed to a slash-command invocation (`/help`,
+ * `/stats`, …) which is stored with `type: 'user'` in the UI but never
+ * reaches the API history or `turnParentUuids`.
+ */
+export function isRealUserTurn(item: HistoryItem): boolean {
+  if (item.type !== 'user' || !item.text) return false;
+  return !item.text.startsWith('/') && !item.text.startsWith('?');
+}
+
 /**
  * The well-known startup context model acknowledgment.
  * Used to identify the startup context pair in the API history.
@@ -67,7 +78,8 @@ function hasStartupContext(apiHistory: Content[]): boolean {
  * @param uiHistory The full UI history array
  * @param targetUserItemId The ID of the user HistoryItem to rewind to
  * @param apiHistory The current API Content[] array
- * @returns The number of Content entries to keep in the API history
+ * @returns The number of Content entries to keep, or -1 if the target turn
+ *   could not be located (e.g., it was absorbed by chat compression).
  */
 export function computeApiTruncationIndex(
   uiHistory: HistoryItem[],
@@ -80,7 +92,7 @@ export function computeApiTruncationIndex(
     if (item.id === targetUserItemId) {
       break;
     }
-    if (item.type === 'user') {
+    if (isRealUserTurn(item)) {
       uiUserTurnCount++;
     }
   }
@@ -109,6 +121,6 @@ export function computeApiTruncationIndex(
   }
 
   // If we didn't find enough user prompts (e.g., after compression),
-  // return the full API history length
+  // signal that the target turn is unreachable.
-  return apiHistory.length;
+  return -1;
 }