feat(cli): per-turn /diff with interactive dialog

packages/cli/src/ui/AppContainer.tsx

@@ -987,6 +987,17 @@ export const AppContainer = (props: AppContainerProps) => {
   // is swapped in once the real callback exists.
   const openRewindSelectorRef = useRef<() => void>(() => {});
 
+  // /diff opens a per-turn diff dialog. Unlike rewind, no double-press or
+  // history-bound guard is needed, so the open/close handlers can live here
+  // (no ref bridge required).
+  const [isDiffDialogOpen, setIsDiffDialogOpen] = useState(false);
+  const openDiffDialog = useCallback(() => {
+    setIsDiffDialogOpen(true);
+  }, []);
+  const closeDiffDialog = useCallback(() => {
+    setIsDiffDialogOpen(false);
+  }, []);
+
   const slashCommandActions = useMemo(
     () => ({
       openAuthDialog,
@@ -1018,6 +1029,7 @@ export const AppContainer = (props: AppContainerProps) => {
       openHooksDialog,
       openResumeDialog,
       openRewindSelector: () => openRewindSelectorRef.current(),
+      openDiffDialog,
       handleResume,
       handleBranch,
       openDeleteDialog,
@@ -1049,6 +1061,7 @@ export const AppContainer = (props: AppContainerProps) => {
       handleBranch,
       openDeleteDialog,
       openHelpDialog,
+      openDiffDialog,
     ],
   );
 
@@ -2094,6 +2107,7 @@ export const AppContainer = (props: AppContainerProps) => {
     isHelpDialogOpen ||
     isExtensionsManagerDialogOpen ||
     isRewindSelectorOpen ||
+    isDiffDialogOpen ||
     bgTasksDialogOpen;
   dialogsVisibleRef.current = dialogsVisible;
   const shouldShowStickyTodos =
@@ -3093,6 +3107,8 @@ export const AppContainer = (props: AppContainerProps) => {
       // Rewind selector
       isRewindSelectorOpen,
       rewindEscPending,
+      // Diff dialog
+      isDiffDialogOpen,
     }),
     [
       isThemeDialogOpen,
@@ -3215,6 +3231,8 @@ export const AppContainer = (props: AppContainerProps) => {
       // Rewind selector
       isRewindSelectorOpen,
       rewindEscPending,
+      // Diff dialog
+      isDiffDialogOpen,
     ],
   );
 
@@ -3294,6 +3312,9 @@ export const AppContainer = (props: AppContainerProps) => {
       openRewindSelector,
       closeRewindSelector,
       handleRewindConfirm,
+      // Diff dialog
+      openDiffDialog,
+      closeDiffDialog,
     }),
     [
       openThemeDialog,
@@ -3368,6 +3389,9 @@ export const AppContainer = (props: AppContainerProps) => {
       openRewindSelector,
       closeRewindSelector,
       handleRewindConfirm,
+      // Diff dialog
+      openDiffDialog,
+      closeDiffDialog,
     ],
   );
 

packages/cli/src/ui/commands/diffCommand.test.ts

@@ -69,7 +69,12 @@ describe('diffCommand', () => {
 
   it('errors when getWorkingDir and getProjectRoot both return empty', async () => {
     if (!diffCommand.action) throw new Error('Command has no action');
+    // Non-interactive mode runs the fetchGitDiff path that actually needs a
+    // cwd. Interactive mode short-circuits to opening the dialog (the
+    // dialog's own hooks tolerate a missing cwd by showing the empty state),
+    // so the cwd guard only fires off the dialog path.
     const noCwdContext = createMockCommandContext({
+      executionMode: 'non_interactive',
       services: {
         config: {
           getWorkingDir: () => '',
@@ -301,75 +306,26 @@ describe('diffCommand interactive mode', () => {
     mockFetchGitDiff = vi.mocked(fetchGitDiff);
   });
 
-  it('dispatches a diff_stats history item instead of returning text', async () => {
+  it('opens the diff dialog without touching git or the history', async () => {
     if (!diffCommand.action) throw new Error('Command has no action');
     const ctx = makeInteractiveContext();
-    mockFetchGitDiff.mockResolvedValue({
-      stats: { filesCount: 2, linesAdded: 7, linesRemoved: 3 },
-      perFileStats: new Map([
-        ['src/a.ts', { added: 5, removed: 2, isBinary: false }],
-        ['src/b.ts', { added: 2, removed: 1, isBinary: false }],
-      ]),
-    } satisfies GitDiffResult);
 
     const result = await diffCommand.action(ctx, '');
-    expect(result).toBeUndefined();
-    expect(ctx.ui.addItem).toHaveBeenCalledTimes(1);
-    const call = (ctx.ui.addItem as Mock).mock.calls[0][0];
-    expect(call.type).toBe('diff_stats');
-    expect(call.model).toMatchObject({
-      filesCount: 2,
-      linesAdded: 7,
-      linesRemoved: 3,
-      hiddenCount: 0,
-    });
-    expect(call.model.rows).toHaveLength(2);
-    expect(call.model.rows[0]).toMatchObject({
-      filename: 'src/a.ts',
-      added: 5,
-      removed: 2,
-      isBinary: false,
-      isUntracked: false,
-    });
-  });
-
-  it('still returns a plain-text info message for the "clean tree" case', async () => {
-    if (!diffCommand.action) throw new Error('Command has no action');
-    const ctx = makeInteractiveContext();
-    mockFetchGitDiff.mockResolvedValue({
-      stats: { filesCount: 0, linesAdded: 0, linesRemoved: 0 },
-      perFileStats: new Map(),
-    } satisfies GitDiffResult);
-
-    const result = await diffCommand.action(ctx, '');
-    expect(result).toMatchObject({ type: 'message', messageType: 'info' });
+    expect(result).toEqual({ type: 'dialog', dialog: 'diff' });
+    // Dialog ownership: the data fetch happens inside the dialog's hooks,
+    // not in the command. Asserting we *don't* call git here keeps the
+    // contract from regressing to the old "summary in scroll history"
+    // behavior, which paid for a git fetch before the user could even
+    // see the picker.
+    expect(mockFetchGitDiff).not.toHaveBeenCalled();
     expect(ctx.ui.addItem).not.toHaveBeenCalled();
   });
 
-  it('still returns an error MessageActionReturn when fetchGitDiff throws', async () => {
+  it('errors when config is unavailable even in interactive mode', async () => {
     if (!diffCommand.action) throw new Error('Command has no action');
-    const ctx = makeInteractiveContext();
-    mockFetchGitDiff.mockRejectedValueOnce(new Error('boom'));
-
+    const ctx = createMockCommandContext({ executionMode: 'interactive' });
     const result = await diffCommand.action(ctx, '');
     expect(result).toMatchObject({ type: 'message', messageType: 'error' });
-    expect(ctx.ui.addItem).not.toHaveBeenCalled();
-  });
-
-  it('propagates hiddenCount to the history item for fast-path results', async () => {
-    if (!diffCommand.action) throw new Error('Command has no action');
-    const ctx = makeInteractiveContext();
-    mockFetchGitDiff.mockResolvedValue({
-      stats: { filesCount: 60, linesAdded: 100, linesRemoved: 20 },
-      perFileStats: new Map([
-        ['src/a.ts', { added: 1, removed: 0, isBinary: false }],
-      ]),
-    } satisfies GitDiffResult);
-
-    await diffCommand.action(ctx, '');
-    const call = (ctx.ui.addItem as Mock).mock.calls[0][0];
-    expect(call.model.hiddenCount).toBe(59);
-    expect(call.model.rows).toHaveLength(1);
   });
 });
 

packages/cli/src/ui/commands/diffCommand.ts

@@ -13,20 +13,16 @@ import {
   CommandKind,
   type CommandContext,
   type MessageActionReturn,
+  type OpenDialogActionReturn,
   type SlashCommand,
 } from './types.js';
 import { t } from '../../i18n/index.js';
-import {
-  MessageType,
-  type DiffRenderModel,
-  type DiffRenderRow,
-  type HistoryItemDiffStats,
-} from '../types.js';
+import { type DiffRenderModel, type DiffRenderRow } from '../types.js';
 import { escapeAnsiCtrlCodes } from '../utils/textUtils.js';
 
 async function diffAction(
   context: CommandContext,
-): Promise<MessageActionReturn | void> {
+): Promise<MessageActionReturn | OpenDialogActionReturn | void> {
   const { config } = context.services;
   if (!config) {
     return {
@@ -36,6 +32,13 @@ async function diffAction(
     };
   }
 
+  // Interactive mode: open the per-turn diff dialog. Non-interactive / ACP
+  // paths keep the plain-text "working tree vs HEAD" summary so pipes, logs,
+  // and remote transports that don't speak Ink still get legible output.
+  if (context.executionMode === 'interactive') {
+    return { type: 'dialog', dialog: 'diff' };
+  }
+
   const cwd = config.getWorkingDir() || config.getProjectRoot();
   if (!cwd) {
     return {
@@ -78,19 +81,6 @@ async function diffAction(
 
   const model = buildDiffRenderModel(result);
 
-  // Interactive path: dispatch a structured history item so `DiffStatsDisplay`
-  // can render with theme colors. Non-interactive / ACP stay on the
-  // plain-text MessageActionReturn path so pipes, logs, and transports that
-  // don't speak Ink still see legible output.
-  if (context.executionMode === 'interactive') {
-    const item: HistoryItemDiffStats = {
-      type: MessageType.DIFF_STATS,
-      model,
-    };
-    context.ui.addItem(item, Date.now());
-    return;
-  }
-
   return {
     type: 'message',
     messageType: 'info',

packages/cli/src/ui/commands/types.ts

@@ -189,7 +189,8 @@ export interface OpenDialogActionReturn {
     | 'extensions_manage'
     | 'hooks'
     | 'mcp'
-    | 'rewind';
+    | 'rewind'
+    | 'diff';
 }
 
 /**

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

@@ -48,6 +48,7 @@ import { MCPManagementDialog } from './mcp/MCPManagementDialog.js';
 import { HooksManagementDialog } from './hooks/HooksManagementDialog.js';
 import { SessionPicker } from './SessionPicker.js';
 import { RewindSelector } from './RewindSelector.js';
+import { DiffDialog } from './DiffDialog.js';
 import { MemoryDialog } from './MemoryDialog.js';
 import { Help } from './Help.js';
 import { BackgroundTasksDialog } from './background-view/BackgroundTasksDialog.js';
@@ -472,6 +473,18 @@ export const DialogManager = ({
     );
   }
 
+  if (uiState.isDiffDialogOpen) {
+    return (
+      <DiffDialog
+        history={uiState.history}
+        cwd={config.getWorkingDir() || config.getProjectRoot()}
+        fileHistoryService={config.getFileHistoryService()}
+        fileCheckpointingEnabled={config.getFileCheckpointingEnabled()}
+        onClose={uiActions.closeDiffDialog}
+      />
+    );
+  }
+
   // Background tasks dialog — lowest priority so other dialogs
   // (permissions, trust prompts, auth, etc.) always take precedence. The
   // dialog is part of the shared dialogsVisible machinery (see