merge main to pick up German locale for custom provider keys

Co-authored-by: Serhii Dziupin <makeittech@users.noreply.github.com>

packages/ui/src/components/chat/ChatInput.tsx

@@ -52,6 +52,8 @@ import { useCurrentSessionActivity } from '@/hooks/useSessionActivity';
 import { toast } from '@/components/ui';
 // useMessageStore removed — messages now come from sync system
 import { isVSCodeRuntime } from '@/lib/desktop';
+import { useTabletLayout } from '@/lib/device';
+import { useHardwareKeyboard } from '@/lib/hardwareKeyboard';
 import { isIMECompositionEvent } from '@/lib/ime';
 import { getCycledPrimaryAgentName, type MobileControlsPanel } from './mobileControlsUtils';
 import { MobileOverlayPanel } from '@/components/ui/MobileOverlayPanel';
@@ -349,6 +351,8 @@ const ChatInputComponent: React.FC<ChatInputProps> = ({ onOpenSettings, scrollTo
     const getVisibleAgents = useConfigStore((state) => state.getVisibleAgents);
     const agents = getVisibleAgents();
     const isMobile = useUIStore((state) => state.isMobile);
+    const hasHardwareKeyboard = useHardwareKeyboard();
+    const { enabled: isTabletLayout } = useTabletLayout();
     const setImagePreviewOpen = useUIStore((state) => state.setImagePreviewOpen);
     const inputBarOffset = useUIStore((state) => state.inputBarOffset);
     const persistChatDraft = useUIStore((state) => state.persistChatDraft);
@@ -369,6 +373,7 @@ const ChatInputComponent: React.FC<ChatInputProps> = ({ onOpenSettings, scrollTo
     );
     const ensureGitStatus = useGitStore((state) => state.ensureStatus);
     const fetchGitStatus = useGitStore((state) => state.fetchStatus);
+    const clearGitDiffCache = useGitStore((state) => state.clearDiffCache);
     const [showAbortStatus, setShowAbortStatus] = React.useState(false);
     const setSessionAutoAccept = usePermissionStore((state) => state.setSessionAutoAccept);
     const [isNarrowComposer, setIsNarrowComposer] = React.useState(false);
@@ -445,9 +450,12 @@ const ChatInputComponent: React.FC<ChatInputProps> = ({ onOpenSettings, scrollTo
         if (!currentDirectory || !runtimeGit) return;
         return sessionEvents.onGitRefreshHint((hint) => {
             if (normalizePath(hint.directory) !== normalizePath(currentDirectory)) return;
-            void fetchGitStatus(currentDirectory, runtimeGit);
+            if (hint.paths?.length) {
+                clearGitDiffCache(currentDirectory, hint.paths);
+            }
+            void fetchGitStatus(currentDirectory, runtimeGit, { silent: true });
         });
-    }, [currentDirectory, runtimeGit, fetchGitStatus]);
+    }, [clearGitDiffCache, currentDirectory, runtimeGit, fetchGitStatus]);
 
     const handleStartReviewFlow = React.useCallback(async (execution: ReviewFlowExecution) => {
         if (!currentSessionId) return;
@@ -2233,6 +2241,10 @@ const ChatInputComponent: React.FC<ChatInputProps> = ({ onOpenSettings, scrollTo
         editorRef: composerRef,
         formRef: composerFormRef,
         setExpandedInput,
+        // The pill exists to buy screen back from the soft keyboard. A tablet
+        // has the room regardless, and with a hardware keyboard there is no
+        // soft keyboard to buy it back from — keep the real composer up.
+        alwaysExpanded: hasHardwareKeyboard || isTabletLayout,
         holders: {
             controlsPanelOpen: Boolean(mobileControlsPanel),
             attachMenuOpen: mobileAttachMenuOpen,

packages/ui/src/components/chat/composer/language/__tests__/mentions.test.ts

@@ -138,6 +138,11 @@ describe('classifyMention', () => {
         expect(classifyMention('', classifier)).toBeNull();
     });
 
+    test('HTML fragments do not classify as file references', () => {
+        expect(classifyMention('import</style>', classifier)).toBeNull();
+        expect(classifyMention('src/<style.css', classifier)).toBeNull();
+    });
+
     test('an agent name wins over a file-looking name', () => {
         const shadowed = {
             knownAgentNames: new Set(['a.ts']),
@@ -152,4 +157,3 @@ describe('classifyMention', () => {
         expect(looksLikeFilePath('plain', new Set(['plain']))).toBe(true);
     });
 });
-

packages/ui/src/components/chat/composer/language/mentions.ts

@@ -116,6 +116,9 @@ export function classifyMention(
     classifier: MentionClassifier,
 ): MentionKind | null {
     if (!name) return null;
+    // HTML fragments are prompt text, never references. In particular, do not
+    // interpret CSS syntax such as `@import</style>` as a local file path.
+    if (name.includes('<') || name.includes('>')) return null;
     if (classifier.knownAgentNames.has(name.toLowerCase())) return 'agent';
     if (looksLikeFilePath(name, classifier.confirmedMentions)) return 'file';
     return null;

packages/ui/src/components/chat/composer/state/useMobileComposerShell.ts

@@ -18,6 +18,7 @@
 import React from 'react';
 import { flushSync } from 'react-dom';
 
+import { observeEditorFocus } from '@/lib/hardwareKeyboard';
 import { isCapacitorApp } from '@/lib/platform';
 import type { ComposerEditorHandle } from '../editor/ComposerEditor';
 
@@ -41,6 +42,13 @@ export interface MobileComposerShellOptions {
     formRef: React.RefObject<HTMLFormElement | null>;
     setExpandedInput: (expanded: boolean) => void;
     holders: MobileComposerHolders;
+    /**
+     * Keep the full composer up permanently and never fall back to the pill.
+     * The pill exists to buy screen back from the soft keyboard; with a
+     * hardware keyboard on a tablet there is no soft keyboard to hide from,
+     * and collapsing between keystrokes would only cost the user a tap.
+     */
+    alwaysExpanded?: boolean;
 }
 
 export interface MobileComposerShell {
@@ -65,9 +73,9 @@ export interface MobileComposerShell {
 export function useMobileComposerShell(
     options: MobileComposerShellOptions,
 ): MobileComposerShell {
-    const { isMobile, editorRef, formRef, setExpandedInput, holders } = options;
+    const { isMobile, editorRef, formRef, setExpandedInput, holders, alwaysExpanded = false } = options;
 
-    const [expanded, setExpanded] = React.useState(false);
+    const [expanded, setExpanded] = React.useState(alwaysExpanded && isMobile);
     const [focused, setFocused] = React.useState(false);
     const [overlayHostBusy, setOverlayHostBusy] = React.useState(false);
     const [dictationActive, setDictationActive] = React.useState(false);
@@ -88,6 +96,16 @@ export function useMobileComposerShell(
         expandedRef.current = expanded;
     });
 
+    // A hardware keyboard can be attached (or detached) at any moment, so this
+    // is a live condition rather than a mount-time one. Detaching does NOT
+    // force a collapse — the normal idle/keyboard-hide paths take over again.
+    const alwaysExpandedRef = React.useRef(alwaysExpanded);
+    alwaysExpandedRef.current = alwaysExpanded;
+    React.useEffect(() => {
+        if (!isMobile || !alwaysExpanded) return;
+        setExpanded(true);
+    }, [alwaysExpanded, isMobile]);
+
     // The draft screen restructures itself around the composer: its starter
     // chips leave once the full composer is up, and its centered title
     // re-centers over whatever room remains. Announced as a root class from a
@@ -95,12 +113,16 @@ export function useMobileComposerShell(
     // swap — keyed on the keyboard instead (oc-keyboard-open arrives with the
     // keyboardWillShow bridge event, ~100ms later), the chips vanished
     // mid-rise as a second visible jump.
+    //
+    // Not announced while `alwaysExpanded`: there the full composer is the
+    // resting state, not a keyboard takeover, so claiming otherwise would hide
+    // the starters permanently. The keyboard classes still cover that case.
     React.useLayoutEffect(() => {
         if (!isMobile || typeof document === 'undefined') return;
         const root = document.documentElement;
-        root.classList.toggle('oc-composer-expanded', expanded);
+        root.classList.toggle('oc-composer-expanded', expanded && !alwaysExpanded);
         return () => root.classList.remove('oc-composer-expanded');
-    }, [expanded, isMobile]);
+    }, [alwaysExpanded, expanded, isMobile]);
 
     const expand = React.useCallback(() => {
         expandIntentRef.current = 'focus';
@@ -151,7 +173,7 @@ export function useMobileComposerShell(
         // insert-and-send) collapse straight back to the pill rather than
         // parking on the normal composer for the usual grace period.
         window.setTimeout(() => {
-            if (!expandedRef.current) return;
+            if (!expandedRef.current || alwaysExpandedRef.current) return;
             if (editorRef.current?.isFocused()) return;
             setExpanded(false);
             setExpandedInput(false);
@@ -288,7 +310,7 @@ export function useMobileComposerShell(
         || holders.isDragging;
 
     React.useEffect(() => {
-        if (!isMobile || !expanded || busy) return;
+        if (!isMobile || !expanded || busy || alwaysExpanded) return;
         const timer = window.setTimeout(() => {
             // Authoritative DOM check: the React focus state can lag a
             // programmatic refocus (the overlay-close restore above).
@@ -299,7 +321,7 @@ export function useMobileComposerShell(
             setExpandedInput(false);
         }, 250);
         return () => window.clearTimeout(timer);
-    }, [busy, editorRef, expanded, isMobile, setExpandedInput]);
+    }, [alwaysExpanded, busy, editorRef, expanded, isMobile, setExpandedInput]);
 
     const busyRef = React.useRef(false);
     busyRef.current = busy;
@@ -344,7 +366,7 @@ export function useMobileComposerShell(
         const handleIntent = (event: Event) => {
             const detail = (event as CustomEvent<{ open?: boolean }>).detail;
             if (!detail || detail.open !== false) return;
-            if (!expandedRef.current) return;
+            if (!expandedRef.current || alwaysExpandedRef.current) return;
             // Something still holds the composer open (dictation, an overlay
             // that closed the keyboard, a drag) — the fallback path handles it.
             if (busyRef.current) return;
@@ -360,6 +382,9 @@ export function useMobileComposerShell(
 
     const onEditorFocus = React.useCallback(() => {
         if (!isMobile) return;
+        // Focus is the only moment a soft keyboard would be presented, so it is
+        // also the only moment its ABSENCE tells us a hardware one is attached.
+        if (isCapacitorApp()) observeEditorFocus();
         if (blurTimerRef.current !== null) {
             window.clearTimeout(blurTimerRef.current);
             blurTimerRef.current = null;

packages/ui/src/components/chat/markdown/markdownCore.test.ts

@@ -0,0 +1,18 @@
+import { describe, expect, test } from 'bun:test';
+
+import { escapeRawMarkdownHtml, MARKDOWN_FORBIDDEN_TAGS } from './markdownSecurity';
+
+describe('markdown sanitization', () => {
+  test('turns raw assistant HTML into inert visible text', () => {
+    const payload = '<style>@import url("https://example.test/theme.css");</style>';
+
+    expect(escapeRawMarkdownHtml(payload)).toBe(
+      '&lt;style&gt;@import url(&quot;https://example.test/theme.css&quot;);&lt;/style&gt;',
+    );
+  });
+
+  test('forbids script and stylesheet elements as active content', () => {
+    expect(MARKDOWN_FORBIDDEN_TAGS).toContain('script');
+    expect(MARKDOWN_FORBIDDEN_TAGS).toContain('style');
+  });
+});

packages/ui/src/components/chat/markdown/markdownCore.ts

@@ -5,6 +5,7 @@ import DOMPurify from 'dompurify';
 import { buildAgentMentionUrl, parseAgentHref, parseSkillHref } from '@/lib/messages/inlineMessageLinks';
 import { isVSCodeRuntime } from '@/lib/desktop';
 import { highlightCodeInWorker } from './markdown-worker';
+import { escapeRawMarkdownHtml, MARKDOWN_FORBIDDEN_TAGS } from './markdownSecurity';
 
 const escapeAttr = (value: string): string =>
   value.replace(/&/g, '&amp;').replace(/"/g, '&quot;').replace(/</g, '&lt;').replace(/>/g, '&gt;');
@@ -166,6 +167,12 @@ const parser = marked.use({
   breaks: false,
   extensions: [inlineMathExtension, blockMathExtension],
   renderer: {
+    // Assistant output is untrusted. Markdown constructs still render as HTML,
+    // but raw HTML must remain visible text so it cannot introduce active DOM
+    // such as stylesheets or positioned overlays into the application shell.
+    html({ text }) {
+      return escapeRawMarkdownHtml(text);
+    },
     link({ href, title, text }) {
       const target = href ?? '';
       const agentName = parseAgentHref(target);
@@ -283,8 +290,10 @@ const SANITIZE_CONFIG = {
   USE_PROFILES: { html: true, mathMl: true, svg: true },
   ADD_TAGS: ['svg', 'path', 'g', 'rect', 'line', 'polygon', 'polyline', 'circle', 'ellipse', 'text', 'tspan', 'defs', 'marker'],
   ADD_ATTR: ['d', 'viewBox', 'preserveAspectRatio', 'xmlns', 'target', 'fill', 'stroke', 'stroke-width', 'transform', 'points', 'x', 'y', 'x1', 'y1', 'x2', 'y2', 'cx', 'cy', 'r', 'rx', 'ry', 'style'],
-  FORBID_TAGS: ['script'],
-  FORBID_CONTENTS: ['script'],
+  // Defense in depth for generated/highlighter HTML after raw markdown HTML
+  // has been escaped by the marked renderer above.
+  FORBID_TAGS: [...MARKDOWN_FORBIDDEN_TAGS],
+  FORBID_CONTENTS: [...MARKDOWN_FORBIDDEN_TAGS],
 };
 
 let sanitizeHookInstalled = false;

packages/ui/src/components/chat/markdown/markdownSecurity.ts

@@ -0,0 +1,6 @@
+/** Raw HTML in assistant markdown is untrusted and must stay inert text. */
+export const escapeRawMarkdownHtml = (value: string): string =>
+  value.replace(/&/g, '&amp;').replace(/"/g, '&quot;').replace(/</g, '&lt;').replace(/>/g, '&gt;');
+
+/** Active elements forbidden again at the final DOMPurify boundary. */
+export const MARKDOWN_FORBIDDEN_TAGS = ['script', 'style'] as const;

packages/ui/src/components/chat/message/MessageBody.tsx

@@ -34,7 +34,6 @@ import { copyTextToClipboard } from '@/lib/clipboard';
 import { useChatSurfaceMode } from '@/components/chat/useChatSurfaceMode';
 import { isVSCodeRuntime } from '@/lib/desktop';
 import { useRuntimeAPIs } from '@/hooks/useRuntimeAPIs';
-import { toPng } from 'html-to-image';
 import { toast } from '@/components/ui';
 import { Icon } from "@/components/icon/Icon";
 import { formatTimestampForDisplay } from './timeFormat';
@@ -1532,6 +1531,9 @@ const AssistantMessageBody = React.memo(({
 
             let wrapper: HTMLDivElement | null = null;
             try {
+                // Load the exporter before attaching its temporary clone so a slow
+                // chunk request cannot leave export-only content in the page layout.
+                const { toPng } = await import('html-to-image');
                 const originalElement = sourceElement;
                 const computedStyle = window.getComputedStyle(originalElement);
                 const rootStyle = window.getComputedStyle(document.documentElement);

packages/ui/src/components/chat/message/parts/ApplyPatchFileButtons.test.tsx

@@ -0,0 +1,94 @@
+import { describe, expect, test } from 'bun:test';
+import React from 'react';
+import { renderToStaticMarkup } from 'react-dom/server';
+
+import type { EditorAPI } from '@/lib/api/types';
+
+import { ApplyPatchFileButtons } from './ApplyPatchFileButtons';
+import { openApplyPatchFileInEditor } from './applyPatchEditorAction';
+
+const makePatch = (path: string, line: number, before: string, after: string) => [
+    `--- a/${path}`,
+    `+++ b/${path}`,
+    `@@ -${line} +${line} @@`,
+    `-${before}`,
+    `+${after}`,
+].join('\n');
+
+const files = [
+    {
+        filePath: '/workspace/project/src/first.ts',
+        relativePath: 'src/first.ts',
+        patch: makePatch('src/first.ts', 4, 'first old', 'first new'),
+        additions: 1,
+        deletions: 1,
+        type: 'update',
+    },
+    {
+        filePath: '/workspace/project/src/second.ts',
+        relativePath: 'src/second.ts',
+        patch: makePatch('src/second.ts', 12, 'second old', 'second new'),
+        additions: 1,
+        deletions: 1,
+        type: 'update',
+    },
+];
+
+describe('ApplyPatchFileButtons', () => {
+    test('renders one labeled button per non-deleted file', () => {
+        const markup = renderToStaticMarkup(
+            <ApplyPatchFileButtons
+                metadata={{ files }}
+                openDiffLabel="Open file diff"
+                onFileClick={() => undefined}
+            />,
+        );
+
+        expect(markup.match(/<button/g)).toHaveLength(2);
+        expect(markup).toContain('aria-label="Open file diff: src/first.ts"');
+        expect(markup).toContain('aria-label="Open file diff: src/second.ts"');
+    });
+
+    test('opens each clicked file with its own authoritative path, patch, and line', () => {
+        const openDiffCalls: Parameters<EditorAPI['openDiff']>[] = [];
+        const editor: EditorAPI = {
+            openDiff: async (...args) => { openDiffCalls.push(args); },
+            openFile: async () => undefined,
+        };
+        let propagationStops = 0;
+        const stopPropagation = () => { propagationStops += 1; };
+        const tree = ApplyPatchFileButtons({
+            metadata: { files },
+            openDiffLabel: 'Open file diff',
+            onFileClick: (file, event) => {
+                event.stopPropagation();
+                const targetPath = typeof file.relativePath === 'string' ? file.relativePath : '';
+                openApplyPatchFileInEditor({
+                    currentDirectory: '/workspace/project',
+                    diffLabel: `${targetPath} (changes)`,
+                    editor,
+                    file,
+                    isVSCode: true,
+                });
+            },
+        }) as React.ReactElement<{ children: React.ReactNode }>;
+        const buttons = React.Children.toArray(tree.props.children) as React.ReactElement<{
+            onClick: (event: { stopPropagation: () => void }) => void;
+        }>[];
+
+        buttons[0]?.props.onClick({ stopPropagation });
+        buttons[1]?.props.onClick({ stopPropagation });
+
+        expect(propagationStops).toBe(2);
+        expect(openDiffCalls).toEqual([
+            ['', '/workspace/project/src/first.ts', 'src/first.ts (changes)', {
+                line: 4,
+                patch: files[0]?.patch,
+            }],
+            ['', '/workspace/project/src/second.ts', 'src/second.ts (changes)', {
+                line: 12,
+                patch: files[1]?.patch,
+            }],
+        ]);
+    });
+});

packages/ui/src/components/chat/message/parts/ApplyPatchFileButtons.tsx

@@ -0,0 +1,134 @@
+import React from 'react';
+
+import { FileTypeIcon } from '@/components/icons/FileTypeIcon';
+import { Button } from '@/components/ui/button';
+import { Text } from '@/components/ui/text';
+import { cn } from '@/lib/utils';
+
+import { getApplyPatchFilePath } from './toolDiffUtils';
+
+type ApplyPatchFileEntry = {
+    file: Record<string, unknown>;
+    path: string;
+    name: string;
+    added: number | null;
+    removed: number | null;
+};
+
+const parseCount = (value: unknown): number | null => {
+    if (typeof value === 'number' && Number.isFinite(value)) {
+        return Math.max(0, Math.trunc(value));
+    }
+    if (typeof value === 'string') {
+        const parsed = Number.parseInt(value, 10);
+        return Number.isFinite(parsed) ? Math.max(0, parsed) : null;
+    }
+    return null;
+};
+
+const combineCounts = (base: number | null, incoming: number | null): number | null => {
+    if (base === null) return incoming;
+    if (incoming === null) return base;
+    return base + incoming;
+};
+
+const getApplyPatchFileEntries = (metadata: Record<string, unknown> | undefined): ApplyPatchFileEntry[] => {
+    const files = Array.isArray(metadata?.files) ? metadata.files : [];
+    const entriesByPath = new Map<string, ApplyPatchFileEntry>();
+
+    for (const file of files) {
+        if (!file || typeof file !== 'object') continue;
+        const fileRecord = file as Record<string, unknown>;
+        const displayPath = typeof fileRecord.relativePath === 'string'
+            ? fileRecord.relativePath
+            : typeof fileRecord.filePath === 'string'
+                ? fileRecord.filePath
+                : '';
+        if (!displayPath) continue;
+
+        const added = parseCount(fileRecord.additions);
+        const removed = parseCount(fileRecord.deletions);
+        const existing = entriesByPath.get(displayPath);
+        if (existing) {
+            existing.added = combineCounts(existing.added, added);
+            existing.removed = combineCounts(existing.removed, removed);
+            continue;
+        }
+
+        entriesByPath.set(displayPath, {
+            file: fileRecord,
+            path: displayPath,
+            name: displayPath.split('/').pop() || displayPath,
+            added,
+            removed,
+        });
+    }
+
+    return Array.from(entriesByPath.values());
+};
+
+export const ApplyPatchFileButtons = ({
+    animate = true,
+    metadata,
+    onFileClick,
+    openDiffLabel,
+    showFileIcons = true,
+    textClassName,
+}: {
+    animate?: boolean;
+    metadata: Record<string, unknown> | undefined;
+    onFileClick?: (file: Record<string, unknown>, event: React.MouseEvent<HTMLButtonElement>) => void;
+    openDiffLabel: string;
+    showFileIcons?: boolean;
+    textClassName?: string;
+}): React.ReactNode => {
+    const entries = getApplyPatchFileEntries(metadata);
+    if (entries.length <= 1) return null;
+
+    return (
+        <>
+            {entries.map((entry) => {
+                const hasPerFileDiff = entry.added !== null || entry.removed !== null;
+                const content = (
+                    <>
+                        {showFileIcons ? <FileTypeIcon filePath={entry.path} className="h-3.5 w-3.5" /> : null}
+                        <Text
+                            variant={animate ? 'generate-effect' : 'static'}
+                            className={cn('min-w-0 max-w-full truncate', textClassName)}
+                            style={{ color: 'var(--tools-description)' }}
+                            title={entry.path}
+                        >
+                            {entry.name}
+                        </Text>
+                        {hasPerFileDiff ? (
+                            <span className="flex-shrink-0 inline-flex items-center gap-0 typography-meta" style={{ fontSize: '0.8rem', lineHeight: '1' }}>
+                                <span style={{ color: 'var(--status-success)' }}>+{entry.added ?? 0}</span>
+                                <span style={{ color: 'var(--tools-description)' }}>/</span>
+                                <span style={{ color: 'var(--status-error)' }}>-{entry.removed ?? 0}</span>
+                            </span>
+                        ) : null}
+                    </>
+                );
+                const canOpen = onFileClick && entry.file.type !== 'delete' && getApplyPatchFilePath(entry.file);
+                const actionLabel = `${openDiffLabel}: ${entry.path}`;
+                return canOpen ? (
+                    <Button
+                        key={entry.path}
+                        variant="ghost"
+                        size="xs"
+                        className={cn('min-w-0 max-w-full gap-1 normal-case font-normal tracking-normal', textClassName)}
+                        aria-label={actionLabel}
+                        title={actionLabel}
+                        onClick={(event) => onFileClick(entry.file, event)}
+                    >
+                        {content}
+                    </Button>
+                ) : (
+                    <span key={entry.path} className={cn('inline-flex min-w-0 max-w-full items-center gap-1', textClassName)} style={{ color: 'var(--tools-description)' }}>
+                        {content}
+                    </span>
+                );
+            })}
+        </>
+    );
+};

packages/ui/src/components/chat/message/parts/DOCUMENTATION.md

@@ -51,6 +51,10 @@ Use this doc when you ask an agent to change tool/header/description behavior.
 
 ## Current important behavior
 
+- Assistant markdown treats raw HTML as inert visible text. The final generated
+  HTML is sanitized as defense in depth, with script and style elements
+  forbidden, so message content cannot inject active DOM or application-wide
+  CSS into any runtime surface.
 - `read` and `skill` are **static navigation tools** and render via `StaticToolRow`.
 - Every other tool, including search/fetch, OpenCode built-ins, custom tools, plugins, and MCP tools, is **expandable** and renders through `ToolPart`.
 - The managed `openchamber` plugin tool uses the expandable path and hides its broad protocol input. The plugin supplies the selected action's human description as the native tool title; the UI renders that metadata without owning an action map. The full versioned result envelope renders through the same neutral JSON summary/tree/raw views as other tools, without a tool-specific output card.

packages/ui/src/components/chat/message/parts/ToolPart.tsx

@@ -54,11 +54,23 @@ import {
 } from './taskToolModel';
 import { areRenderRelevantPartsEqual } from '../renderCompare';
 import { useI18n } from '@/lib/i18n';
-import { getDiffPatchEntries, getPatchText, type DiffPatchEntry } from './toolDiffUtils';
+import {
+    extractFirstChangedLineFromDiff,
+    getDiffPatchEntries,
+    getFirstChangedLineFromMetadata,
+    getMutatedToolPaths,
+    getPatchText,
+    getPrimaryDiffFromMetadata,
+    getPrimaryToolPath,
+    type DiffPatchEntry,
+} from './toolDiffUtils';
 import { isEmbeddedSessionChat } from '@/components/layout/contextPanelEmbeddedChat';
 import { useStreamingTextThrottle } from '../../hooks/useStreamingTextThrottle';
 import { getStreamingOutputAppend, getToolOutput } from './toolOutput';
+import { toAbsoluteFilePath } from '@/lib/path-utils';
 import { getToolDescriptionFallback } from './toolRenderUtils';
+import { ApplyPatchFileButtons } from './ApplyPatchFileButtons';
+import { openApplyPatchFileInEditor } from './applyPatchEditorAction';
 
 const TOOL_ROW_TEXT_CLASS = '!text-[length:var(--text-meta)] !leading-5 sm:!leading-6 tracking-normal';
 const TOOL_ROW_TITLE_CLASS = cn('typography-meta font-medium', TOOL_ROW_TEXT_CLASS);
@@ -77,84 +89,6 @@ interface ToolPartProps {
     animateTailText?: boolean;
 }
 
-const getMultiFileDescription = (
-    metadata: Record<string, unknown> | undefined,
-    animate = true,
-    showFileIcons = true,
-): React.ReactNode => {
-    const files = Array.isArray(metadata?.files) ? metadata?.files : [];
-    if (files.length <= 1) return null;
-
-    const parseCount = (value: unknown): number | null => {
-        if (typeof value === 'number' && Number.isFinite(value)) {
-            return Math.max(0, Math.trunc(value));
-        }
-        if (typeof value === 'string') {
-            const parsed = Number.parseInt(value, 10);
-            if (Number.isFinite(parsed)) {
-                return Math.max(0, parsed);
-            }
-        }
-        return null;
-    };
-
-    const combineCounts = (base: number | null, incoming: number | null): number | null => {
-        if (base === null) return incoming;
-        if (incoming === null) return base;
-        return base + incoming;
-    };
-
-    const entriesByPath = new Map<string, { path: string; name: string; added: number | null; removed: number | null }>();
-
-    for (const file of files) {
-        const fileObj = file as { relativePath?: string; filePath?: string; additions?: unknown; deletions?: unknown };
-        const filePath = fileObj.relativePath || fileObj.filePath || '';
-        if (!filePath) continue;
-        const fileName = filePath.split('/').pop() || filePath;
-        const added = parseCount(fileObj.additions);
-        const removed = parseCount(fileObj.deletions);
-
-        const existing = entriesByPath.get(filePath);
-        if (existing) {
-            existing.added = combineCounts(existing.added, added);
-            existing.removed = combineCounts(existing.removed, removed);
-            continue;
-        }
-
-        entriesByPath.set(filePath, { path: filePath, name: fileName, added, removed });
-    }
-
-    const entries = Array.from(entriesByPath.values());
-
-    return (
-        <>
-            {entries.map((entry) => {
-                const hasPerFileDiff = entry.added !== null || entry.removed !== null;
-                return (
-                    <span key={entry.path} className={cn('inline-flex min-w-0 max-w-full items-center gap-1', TOOL_ROW_DESCRIPTION_CLASS)} style={{ color: 'var(--tools-description)' }}>
-                        {showFileIcons ? <FileTypeIcon filePath={entry.path} className="h-3.5 w-3.5" /> : null}
-                        <Text
-                            variant={animate ? 'generate-effect' : 'static'}
-                            className={cn('min-w-0 max-w-full truncate', TOOL_ROW_DESCRIPTION_CLASS)}
-                            style={{ color: 'var(--tools-description)' }}
-                            title={entry.path}
-                        >
-                            {entry.name}
-                        </Text>
-                        {hasPerFileDiff ? (
-                            <span className="flex-shrink-0 inline-flex items-center gap-0 typography-meta" style={{ fontSize: '0.8rem', lineHeight: '1' }}>
-                                <span style={{ color: 'var(--status-success)' }}>+{entry.added ?? 0}</span>
-                                <span style={{ color: 'var(--tools-description)' }}>/</span>
-                                <span style={{ color: 'var(--status-error)' }}>-{entry.removed ?? 0}</span>
-                            </span>
-                        ) : null}
-                    </span>
-                );
-            })}
-        </>
-    );
-};
-
 const normalizeToolName = (toolName: string | undefined | null): string => {
     if (typeof toolName !== 'string') {
         return '';
@@ -180,7 +114,6 @@ const GIT_REFRESH_MUTATING_TOOLS = new Set([
     'write',
     'apply_patch',
     'patch',
-    'task',
 ]);
 
 const formatDuration = (start: number, end?: number, now: number = Date.now()) => {
@@ -306,54 +239,6 @@ const parseWriteLineCount = (input?: Record<string, unknown>): number | null =>
     return lines;
 };
 
-const extractFirstChangedLineFromDiff = (diffText: string): number | undefined => {
-    if (!diffText || typeof diffText !== 'string') {
-        return undefined;
-    }
-
-    const lines = diffText.split('\n');
-    let currentNewLine: number | undefined;
-    let firstHunkStart: number | undefined;
-
-    for (const rawLine of lines) {
-        const line = rawLine.replace(/\r$/, '');
-        const hunkMatch = line.match(/^@@\s+-\d+(?:,\d+)?\s+\+(\d+)(?:,\d+)?\s+@@/);
-        if (hunkMatch) {
-            const parsed = Number.parseInt(hunkMatch[1] ?? '', 10);
-            if (Number.isFinite(parsed)) {
-                currentNewLine = Math.max(1, parsed);
-                if (!Number.isFinite(firstHunkStart)) {
-                    firstHunkStart = currentNewLine;
-                }
-            }
-            continue;
-        }
-
-        if (currentNewLine === undefined || !Number.isFinite(currentNewLine)) {
-            continue;
-        }
-
-        if (line.startsWith('+++') || line.startsWith('---') || line.startsWith('diff ')) {
-            continue;
-        }
-
-        if (line.startsWith('+')) {
-            return currentNewLine;
-        }
-
-        if (line.startsWith(' ')) {
-            currentNewLine += 1;
-            continue;
-        }
-
-        if (line.startsWith('-') || line.startsWith('\\')) {
-            continue;
-        }
-    }
-
-    return firstHunkStart;
-};
-
 const buildWritePreviewPatch = (filePath: string | undefined, content: string): string | undefined => {
     const normalizedContent = content.replace(/\r\n/g, '\n');
     if (!normalizedContent.trim()) {
@@ -380,73 +265,6 @@ const buildWritePreviewPatch = (filePath: string | undefined, content: string):
     ].join('\n');
 };
 
-const getFirstChangedLineFromMetadata = (tool: string, metadata?: Record<string, unknown>): number | undefined => {
-    if (!metadata || (tool !== 'edit' && tool !== 'multiedit' && tool !== 'apply_patch')) {
-        return undefined;
-    }
-
-    const topLevelPatch = getPatchText((metadata as { patch?: unknown }).patch) ?? getPatchText(metadata.diff);
-    if (topLevelPatch) {
-        const line = extractFirstChangedLineFromDiff(topLevelPatch);
-        if (Number.isFinite(line)) {
-            return line;
-        }
-    }
-
-    const files = Array.isArray(metadata.files) ? metadata.files : [];
-    const firstFile = files[0] as { patch?: unknown; diff?: unknown } | undefined;
-    const filePatch = getPatchText(firstFile?.patch) ?? getPatchText(firstFile?.diff);
-    if (filePatch) {
-        const line = extractFirstChangedLineFromDiff(filePatch);
-        if (Number.isFinite(line)) {
-            return line;
-        }
-    }
-
-    return undefined;
-};
-
-const getPrimaryDiffFromMetadata = (
-    tool: string,
-    metadata?: Record<string, unknown>,
-    preferredPath?: string,
-): string | undefined => {
-    if (!metadata || (tool !== 'edit' && tool !== 'multiedit' && tool !== 'apply_patch')) {
-        return undefined;
-    }
-
-    const files = Array.isArray(metadata.files) ? metadata.files : [];
-    if (files.length > 0) {
-        const preferred = typeof preferredPath === 'string' && preferredPath.length > 0
-            ? preferredPath
-            : undefined;
-        const matched = preferred
-            ? files.find((file) => {
-                if (!file || typeof file !== 'object') {
-                    return false;
-                }
-                const candidate = file as { relativePath?: unknown; filePath?: unknown };
-                return candidate.relativePath === preferred || candidate.filePath === preferred;
-            })
-            : files[0];
-
-        if (matched && typeof matched === 'object') {
-            const patch = getPatchText((matched as { patch?: unknown; diff?: unknown }).patch)
-                ?? getPatchText((matched as { patch?: unknown; diff?: unknown }).diff);
-            if (patch) {
-                return patch;
-            }
-        }
-    }
-
-    const topLevelPatch = getPatchText((metadata as { patch?: unknown }).patch) ?? getPatchText(metadata.diff);
-    if (topLevelPatch) {
-        return topLevelPatch;
-    }
-
-    return undefined;
-};
-
 const normalizeDisplayPath = (value: string): string => {
     const trimmed = value.trim().replace(/\\/g, '/').replace(/\/{2,}/g, '/');
     if (!trimmed || trimmed === '/') {
@@ -526,58 +344,6 @@ const normalizeToolDiagnostic = (value: unknown): ToolDiagnostic | null => {
     };
 };
 
-const getPrimaryToolPath = (
-    toolName: string,
-    input: Record<string, unknown> | undefined,
-    metadata: Record<string, unknown> | undefined,
-): string | null => {
-    if (toolName === 'apply_patch') {
-        const files = Array.isArray(metadata?.files) ? metadata.files : [];
-        const first = files.find((entry) => {
-            if (!isRecord(entry)) {
-                return false;
-            }
-            return entry.type !== 'delete';
-        });
-        if (!isRecord(first)) {
-            return null;
-        }
-        return typeof first.movePath === 'string'
-            ? first.movePath
-            : typeof first.filePath === 'string'
-                ? first.filePath
-                : typeof first.relativePath === 'string'
-                    ? first.relativePath
-                    : null;
-    }
-
-    if (toolName === 'edit' || toolName === 'multiedit') {
-        const fileDiff = isRecord(metadata?.filediff) ? metadata.filediff : undefined;
-        if (isRecord(fileDiff) && typeof fileDiff.file === 'string') {
-            return fileDiff.file;
-        }
-        return typeof input?.filePath === 'string'
-            ? input.filePath
-            : typeof input?.file_path === 'string'
-                ? input.file_path
-                : typeof input?.path === 'string'
-                    ? input.path
-                    : null;
-    }
-
-    if (toolName === 'write') {
-        return typeof input?.filePath === 'string'
-            ? input.filePath
-            : typeof input?.file_path === 'string'
-                ? input.file_path
-                : typeof input?.path === 'string'
-                    ? input.path
-                    : null;
-    }
-
-    return null;
-};
-
 const getToolDiagnosticSection = (
     toolName: string,
     input: Record<string, unknown> | undefined,
@@ -1686,9 +1452,7 @@ const ToolExpandedContent: React.FC<ToolExpandedContentProps> = React.memo(({
     );
 
     const renderResultContent = () => {
-        const getEntryAbsolutePath = (entry: DiffPatchEntry) => (
-            entry.title.startsWith('/') ? entry.title : `${currentDirectory}/${entry.title}`.replace(/\/+/g, '/')
-        );
+        const getEntryAbsolutePath = (entry: DiffPatchEntry) => toAbsoluteFilePath(currentDirectory, entry.filePath ?? entry.title);
         const openEntryFile = (entry: DiffPatchEntry, event: React.MouseEvent<HTMLButtonElement>) => {
             event.stopPropagation();
             const line = extractFirstChangedLineFromDiff(entry.patch);
@@ -2054,7 +1818,11 @@ const ToolPartContent: React.FC<ToolPartProps> = ({
     onShowPopup,
     animateTailText = true,
 }) => {
+    const { t } = useI18n();
     const state = part.state;
+    const stateWithData = state as ToolStateWithMetadata;
+    const metadata = stateWithData.metadata;
+    const input = stateWithData.input;
     const showToolFileIcons = useUIStore((s) => s.showToolFileIcons);
     const currentDirectory = useEffectiveDirectory() ?? '';
 
@@ -2063,18 +1831,19 @@ const ToolPartContent: React.FC<ToolPartProps> = ({
 
     const status = state?.status as string | undefined;
     const isFinalized = status === 'completed' || status === 'error' || status === 'aborted' || status === 'failed' || status === 'timeout' || status === 'cancelled';
+    const isSuccessfullyFinalized = status === 'completed';
     const isError = status === 'error' || status === 'failed';
 
     const [activeLatched, setActiveLatched] = React.useState<boolean>(!isFinalized);
     const previousPartIdRef = React.useRef<string | undefined>(part.id);
-    const lastGitRefreshSignatureRef = React.useRef<string>('');
+    const observedActiveGitToolRef = React.useRef(!isFinalized);
 
     React.useEffect(() => {
         if (previousPartIdRef.current === part.id) {
             return;
         }
         previousPartIdRef.current = part.id;
-        lastGitRefreshSignatureRef.current = '';
+        observedActiveGitToolRef.current = !isFinalized;
         // Reset latch only when tool identity changes.
         setActiveLatched(!isFinalized);
     }, [isFinalized, part.id]);
@@ -2086,20 +1855,34 @@ const ToolPartContent: React.FC<ToolPartProps> = ({
     }, [isFinalized]);
 
     React.useEffect(() => {
-        if (!isFinalized || isError || !currentDirectory) {
-            return;
-        }
-        if (!GIT_REFRESH_MUTATING_TOOLS.has(normalizedPartTool)) {
+        if (!isFinalized) {
+            observedActiveGitToolRef.current = true;
             return;
         }
 
-        const signature = `${part.id}:${status ?? 'unknown'}`;
-        if (lastGitRefreshSignatureRef.current === signature) {
+        // Historical completed tools can remount when the timeline changes.
+        // Refresh only for a tool whose active state this instance observed.
+        const finalizedAfterObservedActive = observedActiveGitToolRef.current;
+        if (!finalizedAfterObservedActive) {
             return;
         }
-        lastGitRefreshSignatureRef.current = signature;
-        sessionEvents.requestGitRefresh({ directory: currentDirectory });
-    }, [currentDirectory, isError, isFinalized, normalizedPartTool, part.id, status]);
+
+        if (!isSuccessfullyFinalized || !GIT_REFRESH_MUTATING_TOOLS.has(normalizedPartTool)) {
+            observedActiveGitToolRef.current = false;
+            return;
+        }
+        if (!currentDirectory) {
+            return;
+        }
+
+        observedActiveGitToolRef.current = false;
+        const paths = getMutatedToolPaths(normalizedPartTool, input, metadata)
+            .map((path) => getRelativePath(path, currentDirectory));
+        sessionEvents.requestGitRefresh({
+            directory: currentDirectory,
+            ...(paths.length > 0 ? { paths } : {}),
+        });
+    }, [currentDirectory, input, isFinalized, isSuccessfullyFinalized, metadata, normalizedPartTool]);
 
     const shouldNotifyStructuralChange = isFinalized || isTaskTool;
 
@@ -2125,10 +1908,7 @@ const ToolPartContent: React.FC<ToolPartProps> = ({
         }
     }, [isExpanded, isTaskTool, shouldNotifyStructuralChange]);
 
-    const stateWithData = state as ToolStateWithMetadata;
-    const metadata = stateWithData.metadata;
     const partMetadata = (part as unknown as { metadata?: unknown }).metadata;
-    const input = stateWithData.input;
     const time = stateWithData.time;
 
     const [pinnedTime, setPinnedTime] = React.useState<{ start?: number; end?: number }>(() => ({
@@ -2347,6 +2127,26 @@ const ToolPartContent: React.FC<ToolPartProps> = ({
     }, [descriptionPath, normalizedPartTool, stateWithData, input]);
     const runtime = React.useContext(RuntimeAPIContext);
 
+    const openApplyPatchFile = (file: Record<string, unknown>, event: React.MouseEvent<HTMLButtonElement>) => {
+        if (!runtime?.editor) {
+            return;
+        }
+
+        event.stopPropagation();
+        const displayPath = typeof file.relativePath === 'string'
+            ? file.relativePath
+            : typeof file.filePath === 'string'
+                ? getRelativePath(file.filePath, currentDirectory)
+                : '';
+        openApplyPatchFileInEditor({
+            currentDirectory,
+            diffLabel: `${displayPath} (changes)`,
+            editor: runtime.editor,
+            file,
+            isVSCode: runtime.runtime.isVSCode,
+        });
+    };
+
     const handleMainClick = (e: { stopPropagation: () => void }) => {
         if (isTaskTool || !runtime?.editor) {
             onToggle(part.id);
@@ -2356,23 +2156,21 @@ const ToolPartContent: React.FC<ToolPartProps> = ({
         let filePath: unknown;
         let targetLine: number | undefined;
         let toolDiff: string | undefined;
-        if (part.tool === 'edit' || part.tool === 'multiedit') {
+        if (normalizedPartTool === 'edit' || normalizedPartTool === 'multiedit') {
             filePath = input?.filePath || input?.file_path || input?.path || metadata?.filePath || metadata?.file_path || metadata?.path;
-            targetLine = getFirstChangedLineFromMetadata(part.tool, metadata);
             if (typeof filePath === 'string') {
-                toolDiff = getPrimaryDiffFromMetadata(part.tool, metadata, filePath);
+                toolDiff = getPrimaryDiffFromMetadata(normalizedPartTool, metadata, filePath);
+                targetLine = getFirstChangedLineFromMetadata(normalizedPartTool, metadata, filePath);
             }
-        } else if (part.tool === 'apply_patch') {
-            const files = Array.isArray(metadata?.files) ? metadata?.files : [];
-            const firstFile = files[0] as { relativePath?: string; filePath?: string } | undefined;
-            filePath = firstFile?.relativePath || firstFile?.filePath;
-            targetLine = getFirstChangedLineFromMetadata(part.tool, metadata);
+        } else if (normalizedPartTool === 'apply_patch') {
+            filePath = getPrimaryToolPath(normalizedPartTool, input, metadata);
             if (typeof filePath === 'string') {
-                toolDiff = getPrimaryDiffFromMetadata(part.tool, metadata, filePath);
+                toolDiff = getPrimaryDiffFromMetadata(normalizedPartTool, metadata, filePath);
+                targetLine = getFirstChangedLineFromMetadata(normalizedPartTool, metadata, filePath);
             }
-        } else if (['write', 'create', 'file_write'].includes(part.tool)) {
+        } else if (['write', 'create', 'file_write'].includes(normalizedPartTool)) {
             filePath = input?.filePath || input?.file_path || input?.path || metadata?.filePath || metadata?.file_path || metadata?.path;
-        } else if (part.tool === 'lsp') {
+        } else if (normalizedPartTool === 'lsp') {
             filePath = input?.filePath || input?.file_path || input?.path;
             const line = input?.line;
             targetLine = typeof line === 'number' && Number.isFinite(line) ? Math.trunc(line) : undefined;
@@ -2380,11 +2178,8 @@ const ToolPartContent: React.FC<ToolPartProps> = ({
 
         if (typeof filePath === 'string') {
             e.stopPropagation();
-            let absolutePath = filePath;
-            if (!filePath.startsWith('/')) {
-                absolutePath = currentDirectory.endsWith('/') ? currentDirectory + filePath : currentDirectory + '/' + filePath;
-            }
-            if (runtime.runtime.isVSCode && toolDiff && (part.tool === 'edit' || part.tool === 'multiedit' || part.tool === 'apply_patch')) {
+            const absolutePath = toAbsoluteFilePath(currentDirectory, filePath);
+            if (runtime.runtime.isVSCode && toolDiff && (normalizedPartTool === 'edit' || normalizedPartTool === 'multiedit' || normalizedPartTool === 'apply_patch')) {
                 const label = `${getRelativePath(absolutePath, currentDirectory)} (changes)`;
                 void runtime.editor.openDiff('', absolutePath, label, { line: targetLine, patch: toolDiff });
                 return;
@@ -2417,60 +2212,85 @@ const ToolPartContent: React.FC<ToolPartProps> = ({
             {}
             <div
                 className={cn(
-                'group/tool flex gap-1.5 pr-2 pl-px py-1.5 rounded-xl cursor-pointer',
-                isMultiFileApplyPatch ? 'flex-wrap items-start' : 'items-center'
-            )}
-                onClick={handleMainClick}
-                onKeyDown={handleMainKeyDown}
+                    'group/tool flex gap-1.5 pr-2 pl-px py-1.5 rounded-xl',
+                    isMultiFileApplyPatch ? 'flex-wrap items-start cursor-pointer' : 'items-center cursor-pointer',
+                )}
+                onClick={isMultiFileApplyPatch ? () => onToggle(part.id) : handleMainClick}
+                onKeyDown={isMultiFileApplyPatch ? (event) => {
+                    if (event.target !== event.currentTarget) return;
+                    if (event.key !== 'Enter' && event.key !== ' ') return;
+                    event.preventDefault();
+                    onToggle(part.id);
+                } : handleMainKeyDown}
                 role="button"
                 tabIndex={0}
             >
                 <div className={cn('flex gap-1.5', isMultiFileApplyPatch ? 'w-full min-w-0 flex-wrap items-center gap-x-2 gap-y-0.5' : 'items-center flex-shrink-0')}>
-                    {}
-                    <div
-                        // h-5 matches StaticToolRow's icon column, so expandable
-                        // and static rows come out the same height (the 14px
-                        // icon alone left these rows ~2px shorter).
-                        className="relative h-5 w-3.5 flex-shrink-0 cursor-pointer"
-                        onClick={(event) => { event.stopPropagation(); onToggle(part.id); }}
-                    >
-                        {}
-                        <div
-                            className={cn(
-                                'absolute inset-0 flex items-center justify-center transition-opacity',
-                                isExpanded && 'opacity-0',
-                                !isExpanded && 'group-hover/tool:opacity-0'
-                            )}
-                            style={iconStyle}
-                        >
-                            {getToolIcon(normalizedPartTool || part.tool)}
-                        </div>
-                        {}
-                        <div
-                            className={cn(
-                                'absolute inset-0 transition-opacity flex items-center justify-center',
-                                isExpanded && 'opacity-100',
-                                !isExpanded && 'opacity-0 group-hover/tool:opacity-100'
-                            )}
-                        >
-                            {isExpanded ? <Icon name="arrow-down-s" className="h-3.5 w-3.5" /> : <Icon name="arrow-right-s" className="h-3.5 w-3.5" />}
-                        </div>
-                    </div>
                     {isMultiFileApplyPatch ? (
                         <>
-                            <MinDurationShineText
-                                active={Boolean(isActive && !isError)}
-                                minDurationMs={300}
-                                className={cn(TOOL_ROW_TITLE_CLASS, 'flex-shrink-0')}
-                                style={titleStyle}
-                                title={displayName}
-                            >
-                                {displayName}
-                            </MinDurationShineText>
-                            {getMultiFileDescription(metadata, animateTailText, showToolFileIcons)}
+                            <div className="flex h-5 flex-shrink-0 items-center gap-1.5">
+                                <span className="relative h-3.5 w-3.5 flex-shrink-0">
+                                    <span className={cn(
+                                        'absolute inset-0 flex items-center justify-center transition-opacity',
+                                        isExpanded ? 'opacity-0' : 'group-hover/tool:opacity-0',
+                                    )} style={iconStyle}>
+                                        {getToolIcon(normalizedPartTool || part.tool)}
+                                    </span>
+                                    <Icon
+                                        name={isExpanded ? 'arrow-down-s' : 'arrow-right-s'}
+                                        className={cn(
+                                            'absolute inset-0 h-3.5 w-3.5 transition-opacity',
+                                            isExpanded ? 'opacity-100' : 'opacity-0 group-hover/tool:opacity-100',
+                                        )}
+                                    />
+                                </span>
+                                <MinDurationShineText
+                                    active={Boolean(isActive && !isError)}
+                                    minDurationMs={300}
+                                    className={cn(TOOL_ROW_TITLE_CLASS, 'flex-shrink-0')}
+                                    style={titleStyle}
+                                >
+                                    {displayName}
+                                </MinDurationShineText>
+                            </div>
+                            <ApplyPatchFileButtons
+                                metadata={metadata}
+                                animate={animateTailText}
+                                showFileIcons={showToolFileIcons}
+                                textClassName={TOOL_ROW_DESCRIPTION_CLASS}
+                                openDiffLabel={t('chat.toolPart.openFileDiff')}
+                                onFileClick={runtime?.editor ? openApplyPatchFile : undefined}
+                            />
                         </>
                     ) : (
                         <>
+                            <div
+                                // h-5 matches StaticToolRow's icon column, so expandable
+                                // and static rows come out the same height (the 14px
+                                // icon alone left these rows ~2px shorter).
+                                className="relative h-5 w-3.5 flex-shrink-0 cursor-pointer"
+                                onClick={(event) => { event.stopPropagation(); onToggle(part.id); }}
+                            >
+                                <div
+                                    className={cn(
+                                        'absolute inset-0 flex items-center justify-center transition-opacity',
+                                        isExpanded && 'opacity-0',
+                                        !isExpanded && 'group-hover/tool:opacity-0'
+                                    )}
+                                    style={iconStyle}
+                                >
+                                    {getToolIcon(normalizedPartTool || part.tool)}
+                                </div>
+                                <div
+                                    className={cn(
+                                        'absolute inset-0 transition-opacity flex items-center justify-center',
+                                        isExpanded && 'opacity-100',
+                                        !isExpanded && 'opacity-0 group-hover/tool:opacity-100'
+                                    )}
+                                >
+                                    {isExpanded ? <Icon name="arrow-down-s" className="h-3.5 w-3.5" /> : <Icon name="arrow-right-s" className="h-3.5 w-3.5" />}
+                                </div>
+                            </div>
                             <div className="flex items-center gap-2 min-w-0 flex-1">
                                 <MinDurationShineText
                                     active={Boolean(isActive && !isError)}

packages/ui/src/components/chat/message/parts/applyPatchEditorAction.ts

@@ -0,0 +1,33 @@
+import type { EditorAPI } from '@/lib/api/types';
+import { toAbsoluteFilePath } from '@/lib/path-utils';
+
+import { extractFirstChangedLineFromDiff, getApplyPatchFilePath, getPatchText } from './toolDiffUtils';
+
+export const openApplyPatchFileInEditor = ({
+    currentDirectory,
+    diffLabel,
+    editor,
+    file,
+    isVSCode,
+}: {
+    currentDirectory: string;
+    diffLabel: string;
+    editor: EditorAPI;
+    file: Record<string, unknown>;
+    isVSCode: boolean;
+}): boolean => {
+    const filePath = getApplyPatchFilePath(file);
+    if (!filePath || file.type === 'delete') {
+        return false;
+    }
+
+    const patch = getPatchText(file.patch) ?? getPatchText(file.diff);
+    const line = patch ? extractFirstChangedLineFromDiff(patch) : undefined;
+    const absolutePath = toAbsoluteFilePath(currentDirectory, filePath);
+    if (isVSCode && patch) {
+        void editor.openDiff('', absolutePath, diffLabel, { line, patch });
+    } else {
+        void editor.openFile(absolutePath, line);
+    }
+    return true;
+};

packages/ui/src/components/chat/message/parts/toolDiffUtils.test.ts

@@ -1,10 +1,110 @@
 import { describe, expect, test } from 'bun:test';
 
-import { getDiffPatchEntries, getRenderablePatchInfo } from './toolDiffUtils';
+import {
+    getApplyPatchFilePath,
+    getDiffPatchEntries,
+    getFirstChangedLineFromMetadata,
+    getMutatedToolPaths,
+    getPrimaryDiffFromMetadata,
+    getPrimaryToolPath,
+    getRenderablePatchInfo,
+} from './toolDiffUtils';
 
 const identity = (path: string) => path;
 
 describe('toolDiffUtils', () => {
+    test('prefers the absolute apply_patch path over its worktree-relative label', () => {
+        expect(getPrimaryToolPath('apply_patch', undefined, {
+            files: [{
+                filePath: '/workspace/project/src/file.ts',
+                relativePath: 'workspace/project/src/file.ts',
+                type: 'update',
+            }],
+        })).toBe('/workspace/project/src/file.ts');
+    });
+
+    test('opens the move destination and skips deleted apply_patch files', () => {
+        expect(getPrimaryToolPath('apply_patch', undefined, {
+            files: [
+                { filePath: '/workspace/deleted.ts', relativePath: 'deleted.ts', type: 'delete' },
+                {
+                    filePath: '/workspace/old.ts',
+                    relativePath: 'new.ts',
+                    movePath: '/workspace/new.ts',
+                    type: 'move',
+                },
+            ],
+        })).toBe('/workspace/new.ts');
+    });
+
+    test('falls back to the relative apply_patch path for legacy metadata', () => {
+        expect(getPrimaryToolPath('apply_patch', undefined, {
+            files: [{ relativePath: 'src/file.ts', type: 'update' }],
+        })).toBe('src/file.ts');
+    });
+
+    test('resolves each apply_patch file independently', () => {
+        expect(getApplyPatchFilePath({
+            filePath: '/workspace/project/src/first.ts',
+            relativePath: 'workspace/project/src/first.ts',
+        })).toBe('/workspace/project/src/first.ts');
+        expect(getApplyPatchFilePath({
+            filePath: '/workspace/project/src/old.ts',
+            movePath: '/workspace/project/src/second.ts',
+            relativePath: 'src/second.ts',
+        })).toBe('/workspace/project/src/second.ts');
+    });
+
+    test('lists every apply_patch mutation path, including both sides of a move', () => {
+        expect(getMutatedToolPaths('apply_patch', undefined, {
+            files: [
+                { filePath: '/workspace/project/src/deleted.ts', type: 'delete' },
+                {
+                    filePath: '/workspace/project/src/old.ts',
+                    movePath: '/workspace/project/src/new.ts',
+                    type: 'move',
+                },
+            ],
+        })).toEqual([
+            '/workspace/project/src/deleted.ts',
+            '/workspace/project/src/new.ts',
+            '/workspace/project/src/old.ts',
+        ]);
+    });
+
+    test('does not invent paths for bash or task tools', () => {
+        expect(getMutatedToolPaths('bash', { command: 'date' }, undefined)).toEqual([]);
+        expect(getMutatedToolPaths('task', { description: 'inspect' }, undefined)).toEqual([]);
+    });
+
+    test('selects the move patch and line from the same non-deleted file', () => {
+        const deletedPatch = '@@ -3 +3 @@\n-old\n+deleted';
+        const movedPatch = '@@ -42 +42 @@\n-before\n+after';
+        const metadata = {
+            patch: deletedPatch,
+            files: [
+                {
+                    filePath: '/workspace/project/src/deleted.ts',
+                    relativePath: 'src/deleted.ts',
+                    patch: deletedPatch,
+                    type: 'delete',
+                },
+                {
+                    filePath: '/workspace/project/src/old.ts',
+                    movePath: '/workspace/project/src/moved.ts',
+                    relativePath: 'src/moved.ts',
+                    patch: movedPatch,
+                    type: 'move',
+                },
+            ],
+        };
+
+        expect(getPrimaryDiffFromMetadata('apply_patch', metadata, '/workspace/project/src/moved.ts'))
+            .toBe(movedPatch);
+        expect(getFirstChangedLineFromMetadata('apply_patch', metadata, '/workspace/project/src/moved.ts'))
+            .toBe(42);
+    });
+
     test('treats raw apply_patch envelopes as text, not visual diffs', () => {
         const entries = getDiffPatchEntries(undefined, [
             '*** Begin Patch',
@@ -57,6 +157,27 @@ describe('toolDiffUtils', () => {
         expect(entries[0]?.title).toBe('src/file.ts');
     });
 
+    test('keeps the authoritative path for every metadata file entry', () => {
+        const patch = [
+            '--- a/src/file.ts',
+            '+++ b/src/file.ts',
+            '@@ -1 +1 @@',
+            '-old',
+            '+new',
+        ].join('\n');
+        const entries = getDiffPatchEntries({
+            files: [
+                { filePath: '/workspace/project/src/first.ts', relativePath: 'src/first.ts', patch },
+                { filePath: '/workspace/project/src/second.ts', relativePath: 'src/second.ts', patch },
+            ],
+        }, undefined, identity);
+
+        expect(entries.map((entry) => entry.filePath)).toEqual([
+            '/workspace/project/src/first.ts',
+            '/workspace/project/src/second.ts',
+        ]);
+    });
+
     test('synthesizes headers for valid headerless hunks', () => {
         const entries = getDiffPatchEntries(undefined, [
             '@@ -1 +1 @@',

packages/ui/src/components/chat/message/parts/toolDiffUtils.ts

@@ -3,6 +3,7 @@ import { parsePatchFiles } from '@pierre/diffs';
 export type DiffPatchEntry = {
     id: string;
     title: string;
+    filePath?: string;
     patch: string;
     renderMode: 'diff' | 'text';
 };
@@ -140,6 +141,195 @@ export const getPatchText = (value: unknown): string | undefined => {
     return undefined;
 };
 
+export const getApplyPatchFilePath = (file: unknown): string | null => {
+    if (!isRecord(file)) {
+        return null;
+    }
+
+    return typeof file.movePath === 'string'
+        ? file.movePath
+        : typeof file.filePath === 'string'
+            ? file.filePath
+            : typeof file.relativePath === 'string'
+                ? file.relativePath
+                : null;
+};
+
+export const getPrimaryToolPath = (
+    toolName: string,
+    input: Record<string, unknown> | undefined,
+    metadata: Record<string, unknown> | undefined,
+): string | null => {
+    if (toolName === 'apply_patch') {
+        const files = Array.isArray(metadata?.files) ? metadata.files : [];
+        for (const file of files) {
+            if (isRecord(file) && file.type !== 'delete') {
+                const filePath = getApplyPatchFilePath(file);
+                if (filePath) {
+                    return filePath;
+                }
+            }
+        }
+        return null;
+    }
+
+    if (toolName === 'edit' || toolName === 'multiedit') {
+        const fileDiff = isRecord(metadata?.filediff) ? metadata.filediff : undefined;
+        if (fileDiff && typeof fileDiff.file === 'string') {
+            return fileDiff.file;
+        }
+        return typeof input?.filePath === 'string'
+            ? input.filePath
+            : typeof input?.file_path === 'string'
+                ? input.file_path
+                : typeof input?.path === 'string'
+                    ? input.path
+                    : null;
+    }
+
+    if (toolName === 'write') {
+        return typeof input?.filePath === 'string'
+            ? input.filePath
+            : typeof input?.file_path === 'string'
+                ? input.file_path
+                : typeof input?.path === 'string'
+                    ? input.path
+                    : null;
+    }
+
+    return null;
+};
+
+export const getMutatedToolPaths = (
+    toolName: string,
+    input: Record<string, unknown> | undefined,
+    metadata: Record<string, unknown> | undefined,
+): string[] => {
+    if (toolName === 'apply_patch') {
+        const files = Array.isArray(metadata?.files) ? metadata.files : [];
+        const paths = new Set<string>();
+        for (const file of files) {
+            if (!isRecord(file)) continue;
+            const filePath = getApplyPatchFilePath(file);
+            if (filePath) paths.add(filePath);
+            if (file.type === 'move' && typeof file.filePath === 'string') {
+                paths.add(file.filePath);
+            }
+        }
+        return [...paths];
+    }
+
+    const primaryPath = getPrimaryToolPath(toolName, input, metadata);
+    return primaryPath ? [primaryPath] : [];
+};
+
+const supportsDiffMetadata = (toolName: string): boolean => (
+    toolName === 'edit' || toolName === 'multiedit' || toolName === 'apply_patch'
+);
+
+const getMetadataFileForPath = (
+    metadata: Record<string, unknown>,
+    preferredPath?: string,
+): Record<string, unknown> | undefined => {
+    const files = Array.isArray(metadata.files) ? metadata.files : [];
+    if (!preferredPath) {
+        const first = files[0];
+        return isRecord(first) ? first : undefined;
+    }
+
+    return files.find((file): file is Record<string, unknown> => (
+        isRecord(file)
+        && (file.relativePath === preferredPath || file.filePath === preferredPath || file.movePath === preferredPath)
+    ));
+};
+
+export const getPrimaryDiffFromMetadata = (
+    toolName: string,
+    metadata?: Record<string, unknown>,
+    preferredPath?: string,
+): string | undefined => {
+    if (!metadata || !supportsDiffMetadata(toolName)) {
+        return undefined;
+    }
+
+    const matchedFile = getMetadataFileForPath(metadata, preferredPath);
+    const filePatch = getPatchText(matchedFile?.patch) ?? getPatchText(matchedFile?.diff);
+    if (filePatch) {
+        return filePatch;
+    }
+
+    return getPatchText(metadata.patch) ?? getPatchText(metadata.diff);
+};
+
+export const extractFirstChangedLineFromDiff = (diffText: string): number | undefined => {
+    if (!diffText) {
+        return undefined;
+    }
+
+    let currentNewLine: number | undefined;
+    let firstHunkStart: number | undefined;
+    for (const rawLine of diffText.split('\n')) {
+        const line = rawLine.replace(/\r$/, '');
+        const hunkMatch = line.match(/^@@\s+-\d+(?:,\d+)?\s+\+(\d+)(?:,\d+)?\s+@@/);
+        if (hunkMatch) {
+            const parsed = Number.parseInt(hunkMatch[1] ?? '', 10);
+            if (Number.isFinite(parsed)) {
+                currentNewLine = Math.max(1, parsed);
+                firstHunkStart ??= currentNewLine;
+            }
+            continue;
+        }
+
+        if (currentNewLine === undefined) {
+            continue;
+        }
+        if (line.startsWith('+++') || line.startsWith('---') || line.startsWith('diff ')) {
+            continue;
+        }
+        if (line.startsWith('+')) {
+            return currentNewLine;
+        }
+        if (line.startsWith(' ')) {
+            currentNewLine += 1;
+        }
+    }
+
+    return firstHunkStart;
+};
+
+export const getFirstChangedLineFromMetadata = (
+    toolName: string,
+    metadata?: Record<string, unknown>,
+    preferredPath?: string,
+): number | undefined => {
+    if (!metadata || !supportsDiffMetadata(toolName)) {
+        return undefined;
+    }
+
+    if (preferredPath) {
+        const matchedFile = getMetadataFileForPath(metadata, preferredPath);
+        const matchedPatch = getPatchText(matchedFile?.patch) ?? getPatchText(matchedFile?.diff);
+        if (matchedPatch) {
+            const matchedLine = extractFirstChangedLineFromDiff(matchedPatch);
+            if (matchedLine !== undefined) {
+                return matchedLine;
+            }
+        }
+    }
+
+    const topLevelPatch = getPatchText(metadata.patch) ?? getPatchText(metadata.diff);
+    if (topLevelPatch) {
+        const topLevelLine = extractFirstChangedLineFromDiff(topLevelPatch);
+        if (topLevelLine !== undefined) {
+            return topLevelLine;
+        }
+    }
+
+    const firstFile = getMetadataFileForPath(metadata);
+    const firstPatch = getPatchText(firstFile?.patch) ?? getPatchText(firstFile?.diff);
+    return firstPatch ? extractFirstChangedLineFromDiff(firstPatch) : undefined;
+};
+
 const normalizeParsedPath = (path: string | undefined): string => {
     const trimmed = (path ?? '').trim().replace(/\t.*$/, '');
     if (!trimmed || trimmed === '/dev/null') {
@@ -287,7 +477,7 @@ const getPatchEntriesFromText = (
     }];
 };
 
-const getFilePatch = (file: unknown): { patch: string; title: string } | null => {
+const getFilePatch = (file: unknown): { filePath?: string; patch: string; title: string } | null => {
     if (!isRecord(file)) {
         return null;
     }
@@ -304,6 +494,7 @@ const getFilePatch = (file: unknown): { patch: string; title: string } | null =>
             : '';
 
     return {
+        filePath: getApplyPatchFilePath(file) ?? undefined,
         patch,
         title: rawPath,
     };
@@ -325,7 +516,7 @@ export const getDiffPatchEntries = (
             filePatch.title || `File ${index + 1}`,
             `file-${index}`,
             resolveTitle,
-        );
+        ).map((entry) => ({ ...entry, filePath: filePatch.filePath }));
     });
 
     if (fileEntries.length > 0) {

packages/ui/src/components/icon/sprite.ts

@@ -30,6 +30,7 @@ export const iconSpriteData = {
   "book": `<path d="M3 18.5V5C3 3.34315 4.34315 2 6 2H20C20.5523 2 21 2.44772 21 3V21C21 21.5523 20.5523 22 20 22H6.5C4.567 22 3 20.433 3 18.5ZM19 20V17H6.5C5.67157 17 5 17.6716 5 18.5C5 19.3284 5.67157 20 6.5 20H19ZM5 15.3368C5.45463 15.1208 5.9632 15 6.5 15H19V4H6C5.44772 4 5 4.44772 5 5V15.3368Z" fill="currentColor"/>`,
   "book-open": `<path d="M13 21V23H11V21H3C2.44772 21 2 20.5523 2 20V4C2 3.44772 2.44772 3 3 3H9C10.1947 3 11.2671 3.52375 12 4.35418C12.7329 3.52375 13.8053 3 15 3H21C21.5523 3 22 3.44772 22 4V20C22 20.5523 21.5523 21 21 21H13ZM20 19V5H15C13.8954 5 13 5.89543 13 7V19H20ZM11 19V7C11 5.89543 10.1046 5 9 5H4V19H11Z" fill="currentColor"/>`,
   "booklet": `<path d="M20.0049 2C21.1068 2 22 2.89821 22 3.9908V20.0092C22 21.1087 21.1074 22 20.0049 22H4V18H2V16H4V13H2V11H4V8H2V6H4V2H20.0049ZM8 4H6V20H8V4ZM20 4H10V20H20V4Z" fill="currentColor"/>`,
+  "braces": `<path d="M4 18V14.3C4 13.4716 3.32843 12.8 2.5 12.8H2V11.2H2.5C3.32843 11.2 4 10.5284 4 9.7V6C4 4.34315 5.34315 3 7 3H8V5H7C6.44772 5 6 5.44772 6 6V10.1C6 10.9858 5.42408 11.7372 4.62623 12C5.42408 12.2628 6 13.0142 6 13.9V18C6 18.5523 6.44772 19 7 19H8V21H7C5.34315 21 4 19.6569 4 18ZM20 14.3V18C20 19.6569 18.6569 21 17 21H16V19H17C17.5523 19 18 18.5523 18 18V13.9C18 13.0142 18.5759 12.2628 19.3738 12C18.5759 11.7372 18 10.9858 18 10.1V6C18 5.44772 17.5523 5 17 5H16V3H17C18.6569 3 20 4.34315 20 6V9.7C20 10.5284 20.6716 11.2 21.5 11.2H22V12.8H21.5C20.6716 12.8 20 13.4716 20 14.3Z" fill="currentColor"/>`,
   "brain": `<path d="M9 4C10.1046 4 11 4.89543 11 6V12.8271C10.1058 12.1373 8.96602 11.7305 7.6644 11.5136L7.3356 13.4864C8.71622 13.7165 9.59743 14.1528 10.1402 14.7408C10.67 15.3147 11 16.167 11 17.5C11 18.8807 9.88071 20 8.5 20C7.11929 20 6 18.8807 6 17.5V17.1493C6.43007 17.2926 6.87634 17.4099 7.3356 17.4864L7.6644 15.5136C6.92149 15.3898 6.1752 15.1144 5.42909 14.7599C4.58157 14.3573 4 13.499 4 12.5C4 11.6653 4.20761 11.0085 4.55874 10.5257C4.90441 10.0504 5.4419 9.6703 6.24254 9.47014L7 9.28078V6C7 4.89543 7.89543 4 9 4ZM12 3.35418C11.2671 2.52376 10.1947 2 9 2C6.79086 2 5 3.79086 5 6V7.77422C4.14895 8.11644 3.45143 8.64785 2.94126 9.34933C2.29239 10.2415 2 11.3347 2 12.5C2 14.0652 2.79565 15.4367 4 16.2422V17.5C4 19.9853 6.01472 22 8.5 22C9.91363 22 11.175 21.3482 12 20.3287C12.825 21.3482 14.0864 22 15.5 22C17.9853 22 20 19.9853 20 17.5V16.2422C21.2044 15.4367 22 14.0652 22 12.5C22 11.3347 21.7076 10.2415 21.0587 9.34933C20.5486 8.64785 19.8511 8.11644 19 7.77422V6C19 3.79086 17.2091 2 15 2C13.8053 2 12.7329 2.52376 12 3.35418ZM18 17.1493V17.5C18 18.8807 16.8807 20 15.5 20C14.1193 20 13 18.8807 13 17.5C13 16.167 13.33 15.3147 13.8598 14.7408C14.4026 14.1528 15.2838 13.7165 16.6644 13.4864L16.3356 11.5136C15.034 11.7305 13.8942 12.1373 13 12.8271V6C13 4.89543 13.8954 4 15 4C16.1046 4 17 4.89543 17 6V9.28078L17.7575 9.47014C18.5581 9.6703 19.0956 10.0504 19.4413 10.5257C19.7924 11.0085 20 11.6653 20 12.5C20 13.499 19.4184 14.3573 18.5709 14.7599C17.8248 15.1144 17.0785 15.3898 16.3356 15.5136L16.6644 17.4864C17.1237 17.4099 17.5699 17.2926 18 17.1493Z" fill="currentColor"/>`,
   "brain-ai-3": `<path d="M19.5 4.7832V7.6709L22 9.11426V14.8867L19.499 16.3311L19.5 19.2178L14.5 22.1045L12 20.6611L9.5 22.1045L4.5 19.2178V16.3311L2 14.8877L2.00098 9.11328L4.5 7.66992V4.78418L9.5 1.89746L11.999 3.34082L14.501 1.89648L19.5 4.7832ZM13 5.07227V7H11V5.07324L9.5 4.20703L6.49902 5.93848V8.8252L4 10.2676V13.7334L6.5 15.1768V18.0635L9.5 19.7959L11 18.9287V17H13V18.9297L14.5 19.7959L17.5 18.0625V15.1768L20 13.7324V10.2695L17.499 8.8252L17.5 5.9375L14.501 4.20605L13 5.07227ZM14.2646 13.1602C14.3529 12.9473 14.6472 12.9473 14.7354 13.1602L14.8623 13.4648C15.0783 13.986 15.4807 14.4027 15.9873 14.6279L16.3457 14.7871C16.5511 14.8784 16.5511 15.1773 16.3457 15.2686L15.9658 15.4375C15.4721 15.6571 15.0761 16.0586 14.8564 16.5625L14.7334 16.8447C14.6432 17.0517 14.3569 17.0517 14.2666 16.8447L14.1436 16.5625C13.9239 16.0586 13.5279 15.6571 13.0342 15.4375L12.6543 15.2686C12.4489 15.1773 12.4489 14.8784 12.6543 14.7871L13.0127 14.6279C13.5193 14.4027 13.9217 13.986 14.1377 13.4648L14.2646 13.1602ZM9.58789 7.7793C9.74239 7.40671 10.2577 7.4067 10.4121 7.7793L10.6338 8.31445C11.0118 9.22695 11.7161 9.95624 12.6025 10.3506L13.2305 10.6289C13.5899 10.7887 13.5897 11.3117 13.2305 11.4717L12.5654 11.7676C11.7013 12.152 11.0086 12.8548 10.624 13.7373L10.4082 14.2324C10.2504 14.5948 9.74973 14.5948 9.5918 14.2324L9.37598 13.7373C8.99143 12.8548 8.29875 12.152 7.43457 11.7676L6.76953 11.4717C6.41033 11.3117 6.41022 10.7887 6.76953 10.6289L7.39746 10.3506C8.2839 9.95624 8.98832 9.22697 9.36621 8.31445L9.58789 7.7793Z" fill="currentColor"/>`,
   "briefcase": `<path d="M7 5V2C7 1.44772 7.44772 1 8 1H16C16.5523 1 17 1.44772 17 2V5H21C21.5523 5 22 5.44772 22 6V20C22 20.5523 21.5523 21 21 21H3C2.44772 21 2 20.5523 2 20V6C2 5.44772 2.44772 5 3 5H7ZM4 16V19H20V16H4ZM4 14H20V7H4V14ZM9 3V5H15V3H9ZM11 11H13V13H11V11Z" fill="currentColor"/>`,
@@ -192,6 +193,7 @@ export const iconSpriteData = {
   "robot": `<path d="M13 4.05493C17.5 4.55237 21 8.36745 21 13V22H3V13C3 8.36745 6.50005 4.55237 11 4.05493V1H13V4.05493ZM19 20V13C19 9.13401 15.866 6 12 6C8.13401 6 5 9.13401 5 13V20H19ZM12 18C9.23858 18 7 15.7614 7 13C7 10.2386 9.23858 8 12 8C14.7614 8 17 10.2386 17 13C17 15.7614 14.7614 18 12 18ZM12 16C13.6569 16 15 14.6569 15 13C15 11.3431 13.6569 10 12 10C10.3431 10 9 11.3431 9 13C9 14.6569 10.3431 16 12 16ZM12 14C11.4477 14 11 13.5523 11 13C11 12.4477 11.4477 12 12 12C12.5523 12 13 12.4477 13 13C13 13.5523 12.5523 14 12 14Z" fill="currentColor"/>`,
   "robot-2": `<path d="M13.5 2C13.5 2.44425 13.3069 2.84339 13 3.11805V5H18C19.6569 5 21 6.34315 21 8V18C21 19.6569 19.6569 21 18 21H6C4.34315 21 3 19.6569 3 18V8C3 6.34315 4.34315 5 6 5H11V3.11805C10.6931 2.84339 10.5 2.44425 10.5 2C10.5 1.17157 11.1716 0.5 12 0.5C12.8284 0.5 13.5 1.17157 13.5 2ZM6 7C5.44772 7 5 7.44772 5 8V18C5 18.5523 5.44772 19 6 19H18C18.5523 19 19 18.5523 19 18V8C19 7.44772 18.5523 7 18 7H13H11H6ZM2 10H0V16H2V10ZM22 10H24V16H22V10ZM9 14.5C9.82843 14.5 10.5 13.8284 10.5 13C10.5 12.1716 9.82843 11.5 9 11.5C8.17157 11.5 7.5 12.1716 7.5 13C7.5 13.8284 8.17157 14.5 9 14.5ZM15 14.5C15.8284 14.5 16.5 13.8284 16.5 13C16.5 12.1716 15.8284 11.5 15 11.5C14.1716 11.5 13.5 12.1716 13.5 13C13.5 13.8284 14.1716 14.5 15 14.5Z" fill="currentColor"/>`,
   "rocket": `<path d="M4.99958 12.9999C4.99958 7.91198 7.90222 3.5636 11.9996 1.81799C16.0969 3.5636 18.9996 7.91198 18.9996 12.9999C18.9996 13.8229 18.9236 14.6264 18.779 15.4027L20.7194 17.2353C20.8845 17.3913 20.9238 17.6389 20.815 17.8383L18.3196 22.4133C18.1873 22.6557 17.8836 22.7451 17.6412 22.6128C17.5993 22.59 17.5608 22.5612 17.5271 22.5274L15.2925 20.2928C15.1049 20.1053 14.8506 19.9999 14.5854 19.9999H9.41379C9.14857 19.9999 8.89422 20.1053 8.70668 20.2928L6.47209 22.5274C6.27683 22.7227 5.96025 22.7227 5.76498 22.5274C5.73122 22.4937 5.70246 22.4552 5.67959 22.4133L3.18412 17.8383C3.07537 17.6389 3.11464 17.3913 3.27975 17.2353L5.22014 15.4027C5.07551 14.6264 4.99958 13.8229 4.99958 12.9999ZM6.47542 19.6957L7.29247 18.8786C7.85508 18.316 8.61814 17.9999 9.41379 17.9999H14.5854C15.381 17.9999 16.1441 18.316 16.7067 18.8786L17.5237 19.6957L18.5056 17.8955L17.4058 16.8568C16.9117 16.3901 16.6884 15.7045 16.8128 15.0364C16.9366 14.3722 16.9996 13.6911 16.9996 12.9999C16.9996 9.13037 15.0045 5.69965 11.9996 4.04033C8.99462 5.69965 6.99958 9.13037 6.99958 12.9999C6.99958 13.6911 7.06255 14.3722 7.18631 15.0364C7.31078 15.7045 7.08746 16.3901 6.59338 16.8568L5.49353 17.8955L6.47542 19.6957ZM11.9996 12.9999C10.895 12.9999 9.99958 12.1045 9.99958 10.9999C9.99958 9.89537 10.895 8.99994 11.9996 8.99994C13.1041 8.99994 13.9996 9.89537 13.9996 10.9999C13.9996 12.1045 13.1041 12.9999 11.9996 12.9999Z" fill="currentColor"/>`,
+  "route": `<path d="M4 15V8.5C4 6.01472 6.01472 4 8.5 4C10.9853 4 13 6.01472 13 8.5V15.5C13 16.8807 14.1193 18 15.5 18C16.8807 18 18 16.8807 18 15.5V8.82929C16.8348 8.41746 16 7.30622 16 6C16 4.34315 17.3431 3 19 3C20.6569 3 22 4.34315 22 6C22 7.30622 21.1652 8.41746 20 8.82929V15.5C20 17.9853 17.9853 20 15.5 20C13.0147 20 11 17.9853 11 15.5V8.5C11 7.11929 9.88071 6 8.5 6C7.11929 6 6 7.11929 6 8.5V15H9L5 20L1 15H4ZM19 7C19.5523 7 20 6.55228 20 6C20 5.44772 19.5523 5 19 5C18.4477 5 18 5.44772 18 6C18 6.55228 18.4477 7 19 7Z" fill="currentColor"/>`,
   "save-3": `<path d="M18 19H19V6.82843L17.1716 5H16V9H7V5H5V19H6V12H18V19ZM4 3H18L20.7071 5.70711C20.8946 5.89464 21 6.149 21 6.41421V20C21 20.5523 20.5523 21 20 21H4C3.44772 21 3 20.5523 3 20V4C3 3.44772 3.44772 3 4 3ZM8 14V19H16V14H8Z" fill="currentColor"/>`,
   "scales-3": `<path d="M12.9985 2L12.9979 3.278L17.9985 4.94591L21.631 3.73509L22.2634 5.63246L19.2319 6.643L22.3272 15.1549C21.2353 16.2921 19.6996 17 17.9985 17C16.2975 17 14.7618 16.2921 13.6699 15.1549L16.7639 6.643L12.9979 5.387V19H16.9985V21H6.99854V19H10.9979V5.387L7.23192 6.643L10.3272 15.1549C9.23528 16.2921 7.69957 17 5.99854 17C4.2975 17 2.76179 16.2921 1.66992 15.1549L4.76392 6.643L1.73363 5.63246L2.36608 3.73509L5.99854 4.94591L10.9979 3.278L10.9985 2H12.9985ZM17.9985 9.10267L16.04 14.4892C16.628 14.8201 17.2979 15 17.9985 15C18.6992 15 19.3691 14.8201 19.957 14.4892L17.9985 9.10267ZM5.99854 9.10267L4.04004 14.4892C4.62795 14.8201 5.29792 15 5.99854 15C6.69916 15 7.36912 14.8201 7.95703 14.4892L5.99854 9.10267Z" fill="currentColor"/>`,
   "scan-2": `<path d="M5.67127 4.25705L13.4142 12L12 13.4142L8.55382 9.96803C8.20193 10.5635 8 11.2582 8 12C8 14.2091 9.79086 16 12 16C14.2091 16 16 14.2091 16 12C16 9.87494 14.3429 8.13693 12.2503 8.00771L10.4459 6.20323C10.9416 6.07067 11.4625 6 12 6C15.3137 6 18 8.68629 18 12C18 15.3137 15.3137 18 12 18C8.68629 18 6 15.3137 6 12C6 10.7042 6.41079 9.50428 7.10925 8.52347L5.68014 7.09436C4.62708 8.44904 4 10.1513 4 12C4 16.4183 7.58172 20 12 20C16.4183 20 20 16.4183 20 12C20 7.58172 16.4183 4 12 4C10.8915 4 9.83557 4.22547 8.8757 4.63306L7.37443 3.13179C8.75768 2.40883 10.3311 2 12 2C17.5228 2 22 6.47715 22 12C22 17.5228 17.5228 22 12 22C6.47715 22 2 17.5228 2 12C2 8.87842 3.43029 6.09091 5.67127 4.25705Z" fill="currentColor"/>`,

packages/ui/src/components/icons/DiffIcon.tsx

@@ -1,9 +1,21 @@
 import type { SVGProps } from 'react';
 
+import { Icon } from '@/components/icon/Icon';
+
 interface DiffIconProps extends Omit<SVGProps<SVGSVGElement>, 'children'> {
   size?: number | string;
 }
 
+export function DiffViewIcon({ className = 'h-5 w-5' }: { className?: string }) {
+  return (
+    <span aria-hidden="true" className={`relative inline-block overflow-hidden rounded-[2px] ${className}`}>
+      <span className="absolute left-[20%] top-[20%] h-[60%] w-[25%] bg-[var(--status-error)]/25" />
+      <span className="absolute right-[20%] top-[20%] h-[60%] w-[25%] bg-[var(--status-success)]/25" />
+      <Icon name="layout-column" className="absolute inset-0 h-full w-full" />
+    </span>
+  );
+}
+
 /**
  * Git merge/branch icon for the Diff tab.
  */

packages/ui/src/components/layout/ContextPanel.tsx

@@ -1,6 +1,7 @@
 import React from 'react';
 
 import { FileTypeIcon } from '@/components/icons/FileTypeIcon';
+import { DiffViewIcon } from '@/components/icons/DiffIcon';
 import { Button } from '@/components/ui/button';
 import { SortableTabsStrip } from '@/components/ui/sortable-tabs-strip';
 import { DiffView } from '@/components/views/DiffView';
@@ -8,6 +9,7 @@ import { FilesView } from '@/components/views/FilesView';
 import { GitView } from '@/components/views/GitView';
 import { PullRequestView } from '@/components/views/PullRequestView';
 import { TerminalView } from '@/components/views/TerminalView';
+import { WalkthroughView } from '@/components/views/walkthrough/WalkthroughView';
 import { PlanView } from '@/components/views/PlanView';
 import { ProjectContextPanel } from './RightSidebarTabs';
 import { SidebarFilesTree } from './SidebarFilesTree';
@@ -158,6 +160,7 @@ const getModeLabel = (
   if (mode === 'chat') return t('contextPanel.mode.chat');
   if (mode === 'file') return t('contextPanel.mode.files');
   if (mode === 'diff') return t('contextPanel.mode.diff');
+  if (mode === 'walkthrough') return t('contextPanel.mode.walkthrough');
   if (mode === 'plan') return t('contextPanel.mode.plan');
   if (mode === 'preview') return t('contextPanel.mode.preview');
   if (mode === 'browser') return t('contextPanel.mode.browser');
@@ -244,7 +247,11 @@ const getTabIcon = (tab: { mode: ContextPanelMode; targetPath: string | null }):
   }
 
   if (tab.mode === 'diff') {
-    return <Icon name="arrow-left-right" className="h-3.5 w-3.5" />;
+    return <DiffViewIcon className="h-3.5 w-3.5" />;
+  }
+
+  if (tab.mode === 'walkthrough') {
+    return <Icon name="route" className="h-3.5 w-3.5" />;
   }
 
   if (tab.mode === 'git') {
@@ -252,7 +259,7 @@ const getTabIcon = (tab: { mode: ContextPanelMode; targetPath: string | null }):
   }
 
   if (tab.mode === 'pr') {
-    return <Icon name="git-pull-request" className="h-3.5 w-3.5" />;
+    return <Icon name="github" className="h-3.5 w-3.5" />;
   }
 
   if (tab.mode === 'notes') {
@@ -2717,6 +2724,12 @@ export const ContextPanel: React.FC = () => {
     () => tabs.some((tab) => tab.mode === 'terminal'),
     [tabs],
   );
+  // Keep-alive: the walkthrough holds reading progress and scroll position that
+  // a remount would silently throw away.
+  const hasWalkthroughTab = React.useMemo(
+    () => tabs.some((tab) => tab.mode === 'walkthrough'),
+    [tabs],
+  );
   const BrowserPane = isElectronBrowserRuntime() ? DesktopBrowserPane : IframeBrowserPane;
   const hasFileTabs = React.useMemo(
     () => tabs.some((tab) => tab.mode === 'file'),
@@ -2979,7 +2992,12 @@ export const ContextPanel: React.FC = () => {
             <TerminalView visible={isOpen && activeTab?.mode === 'terminal'} />
           </div>
         ) : null}
-        {activeTab?.mode !== 'chat' && !isFileTabActive && activeTab?.mode !== 'browser' && activeTab?.mode !== 'diff' && activeTab?.mode !== 'terminal' ? activeNonChatContent : null}
+        {hasWalkthroughTab ? (
+          <div className={cn('absolute inset-0', activeTab?.mode === 'walkthrough' ? 'block' : 'hidden')}>
+            <WalkthroughView directory={effectiveDirectory} />
+          </div>
+        ) : null}
+        {activeTab?.mode !== 'chat' && !isFileTabActive && activeTab?.mode !== 'browser' && activeTab?.mode !== 'diff' && activeTab?.mode !== 'terminal' && activeTab?.mode !== 'walkthrough' ? activeNonChatContent : null}
       </div>
       </div>
     </aside>

packages/ui/src/components/layout/ContextPanelRail.tsx

@@ -17,8 +17,11 @@ import {
 import { CSS } from '@dnd-kit/utilities';
 
 import { Icon } from '@/components/icon/Icon';
+import { DiffViewIcon } from '@/components/icons/DiffIcon';
 import { Tooltip, TooltipContent, TooltipTrigger } from '@/components/ui/tooltip';
 import { useEffectiveDirectory } from '@/hooks/useEffectiveDirectory';
+import { useDeviceInfo } from '@/lib/device';
+import { isVSCodeRuntime } from '@/lib/desktop';
 import { useI18n } from '@/lib/i18n';
 import {
   sortContextSurfaces,
@@ -30,6 +33,9 @@ import { useGitStatus } from '@/stores/useGitStore';
 import { normalizeContextPanelDirectoryKey, useUIStore } from '@/stores/useUIStore';
 
 const RAIL_TOOLTIP_DELAY_MS = 150;
+// Tablet width and up: below this the walkthrough cannot show a stop and its
+// code side by side, which is the whole point of the surface.
+const WALKTHROUGH_MIN_WIDTH = 768;
 const EMPTY_TABS: never[] = [];
 
 type RailItemProps = {
@@ -75,7 +81,11 @@ const ContextPanelRailItem: React.FC<RailItemProps> = ({
                 : 'text-muted-foreground hover:text-foreground',
             )}
           >
-            <Icon name={surface.icon} className="h-[18px] w-[18px]" />
+            {surface.id === 'diff' ? (
+              <DiffViewIcon />
+            ) : (
+              <Icon name={surface.icon} className="h-[18px] w-[18px]" />
+            )}
             {showActivityDot ? (
               <span
                 aria-hidden="true"
@@ -105,6 +115,7 @@ export const ContextPanelRail: React.FC = () => {
   const setContextRailOrder = useUIStore((state) => state.setContextRailOrder);
   const openContextSurface = useUIStore((state) => state.openContextSurface);
   const planModeEnabled = useFeatureFlagsStore((state) => state.planModeEnabled);
+  const { screenWidth } = useDeviceInfo();
   const gitStatus = useGitStatus(directoryKey || null);
 
   const sensors = useSensors(
@@ -124,12 +135,17 @@ export const ContextPanelRail: React.FC = () => {
       if (surface.id === 'plan' && !planModeEnabled) {
         return false;
       }
+      // The walkthrough needs room for a stop list beside real code, and its
+      // diffs come from OpenChamber's Git routes, which VS Code does not serve.
+      if (surface.id === 'walkthrough' && (isVSCodeRuntime() || screenWidth < WALKTHROUGH_MIN_WIDTH)) {
+        return false;
+      }
       if (surface.availability === 'has-content') {
         return tabs.some((tab) => tab.mode === surface.mode);
       }
       return true;
     });
-  }, [contextRailOrder, planModeEnabled, tabs]);
+  }, [contextRailOrder, planModeEnabled, screenWidth, tabs]);
 
   const handleDragEnd = React.useCallback((event: DragEndEvent) => {
     const { active, over } = event;

packages/ui/src/components/model-picker/ModelPickerList.tsx

@@ -339,6 +339,11 @@ interface ModelPickerListProps {
   selectedModel?: { providerID: string; modelID: string } | null;
   hiddenModels?: HiddenModel[];
   allowedProviderIds?: string[];
+  /**
+   * Per-model gate, for callers whose feature needs a capability rather than a
+   * provider (e.g. structured output). Applied on top of `allowedProviderIds`.
+   */
+  isModelAllowed?: (providerID: string, modelID: string) => boolean;
   includeNotSelected?: boolean;
   onSelectNone?: () => void;
   selectionCount?: (entry: ModelPickerEntry) => number;
@@ -379,6 +384,7 @@ export const ModelPickerList: React.FC<ModelPickerListProps> = ({
   selectedModel,
   hiddenModels = [],
   allowedProviderIds,
+  isModelAllowed,
   includeNotSelected = false,
   onSelectNone,
   selectionCount,
@@ -448,17 +454,19 @@ export const ModelPickerList: React.FC<ModelPickerListProps> = ({
 
   const filteredFavorites = React.useMemo(() => favoriteModels.filter(({ model, providerID, modelID }) => {
     if (allowedProviderSet && !allowedProviderSet.has(providerID)) return false;
+    if (isModelAllowed && !isModelAllowed(providerID, modelID)) return false;
     if (isHidden(providerID, modelID)) return false;
     const providerName = providerById.get(providerID)?.name || providerID;
     return matchesQuery(getModelDisplayName(model), providerName);
-  }), [allowedProviderSet, favoriteModels, isHidden, matchesQuery, providerById]);
+  }), [allowedProviderSet, favoriteModels, isHidden, isModelAllowed, matchesQuery, providerById]);
 
   const filteredRecents = React.useMemo(() => recentModels.filter(({ model, providerID, modelID }) => {
     if (allowedProviderSet && !allowedProviderSet.has(providerID)) return false;
+    if (isModelAllowed && !isModelAllowed(providerID, modelID)) return false;
     if (isHidden(providerID, modelID)) return false;
     const providerName = providerById.get(providerID)?.name || providerID;
     return matchesQuery(getModelDisplayName(model), providerName);
-  }), [allowedProviderSet, isHidden, matchesQuery, providerById, recentModels]);
+  }), [allowedProviderSet, isHidden, isModelAllowed, matchesQuery, providerById, recentModels]);
 
   const orderedProviders = React.useMemo(() => {
     if (!providerOrder || providerOrder.length === 0) return providers;
@@ -477,11 +485,12 @@ export const ModelPickerList: React.FC<ModelPickerListProps> = ({
       const filteredModels = models.filter((model) => {
         const modelID = typeof model.id === 'string' ? model.id : '';
         if (!modelID || isHidden(provider.id, modelID)) return false;
+        if (isModelAllowed && !isModelAllowed(provider.id, modelID)) return false;
         return matchesQuery(getModelDisplayName(model), provider.name || provider.id);
       });
       return { ...provider, models: filteredModels };
     })
-    .filter((provider) => provider.models.length > 0), [allowedProviderSet, isHidden, matchesQuery, orderedProviders]);
+    .filter((provider) => provider.models.length > 0), [allowedProviderSet, isHidden, isModelAllowed, matchesQuery, orderedProviders]);
 
   const flatModelList = React.useMemo(() => {
     const items: ModelPickerEntry[] = [];

packages/ui/src/components/sections/agents/ModelSelector.tsx

@@ -23,9 +23,17 @@ interface ModelSelectorProps {
     onChange: (providerId: string, modelId: string) => void;
     className?: string;
     allowedProviderIds?: string[];
+    isModelAllowed?: (providerId: string, modelId: string) => boolean;
     placeholder?: string;
     tooltipsEnabled?: boolean;
     dropdownPortalToBody?: boolean;
+    /**
+     * Drop the model name and the chevron, leaving the provider logo. For
+     * headers that run out of room before they run out of controls — the logo
+     * still says which provider is answering, which is the part a glance is
+     * usually after.
+     */
+    compact?: boolean;
 }
 
 export const ModelSelector: React.FC<ModelSelectorProps> = ({
@@ -34,9 +42,11 @@ export const ModelSelector: React.FC<ModelSelectorProps> = ({
     onChange,
     className,
     allowedProviderIds,
+    isModelAllowed,
     placeholder,
     tooltipsEnabled = true,
     dropdownPortalToBody = false,
+    compact = false,
 }) => {
     const { t } = useI18n();
     const { isReady, isUnavailable } = useOpenCodeReadiness();
@@ -115,6 +125,7 @@ export const ModelSelector: React.FC<ModelSelectorProps> = ({
             selectedModel={selectedModel}
             hiddenModels={hiddenModels}
             allowedProviderIds={allowedProviderIds}
+            isModelAllowed={isModelAllowed}
             includeNotSelected
             onSelectNone={handleSelectNone}
             onEscape={closePicker}
@@ -166,26 +177,35 @@ export const ModelSelector: React.FC<ModelSelectorProps> = ({
     return (
         <DropdownMenu open={isReady && isDropdownOpen} onOpenChange={isReady ? setIsDropdownOpen : undefined}>
             <DropdownMenuTrigger asChild>
-                <div className={cn(
-                    dropdownTriggerVariants({ size: 'sm' }),
-                    'min-w-0 w-fit',
-                    !isReady && 'opacity-60 cursor-not-allowed',
-                    className,
-                )}>
+                <div
+                    className={cn(
+                        dropdownTriggerVariants({ size: 'sm' }),
+                        'min-w-0 w-fit',
+                        !isReady && 'opacity-60 cursor-not-allowed',
+                        className,
+                    )}
+                    // The name is gone from the trigger, so it has to stay
+                    // reachable somewhere.
+                    title={compact && isReady ? triggerLabel : undefined}
+                >
                     {!isReady ? (
                         <>
                             <Icon name="loader-4" className="h-3.5 w-3.5 animate-spin text-muted-foreground flex-shrink-0" />
-                            <span className="typography-ui-label font-normal whitespace-nowrap text-muted-foreground">
-                                {isUnavailable ? t('common.unavailable') : t('common.loading')}
-                            </span>
+                            {!compact && (
+                                <span className="typography-ui-label font-normal whitespace-nowrap text-muted-foreground">
+                                    {isUnavailable ? t('common.unavailable') : t('common.loading')}
+                                </span>
+                            )}
                         </>
                     ) : (
                         <>
                             {providerId ? <ProviderLogo providerId={providerId} className="h-3.5 w-3.5 flex-shrink-0" /> : <Icon name="pencil-ai" className="h-3.5 w-3.5 flex-shrink-0 text-muted-foreground" />}
-                            <span className="typography-ui-label min-w-0 flex-1 truncate text-left font-normal text-foreground">{triggerLabel}</span>
+                            {!compact && (
+                                <span className="typography-ui-label min-w-0 flex-1 truncate text-left font-normal text-foreground">{triggerLabel}</span>
+                            )}
                         </>
                     )}
-                    <Icon name="arrow-down-s" className="h-4 w-4 flex-shrink-0 text-muted-foreground/50" />
+                    {!compact && <Icon name="arrow-down-s" className="h-4 w-4 flex-shrink-0 text-muted-foreground/50" />}
                 </div>
             </DropdownMenuTrigger>
             <DropdownMenuContent className="w-[min(380px,calc(100vw-2rem))] p-0 flex flex-col" align="start" portalToBody={dropdownPortalToBody}>

packages/ui/src/components/sections/openchamber/DefaultsSettings.tsx

@@ -45,6 +45,7 @@ export const DefaultsSettings: React.FC = () => {
   const showDeletionDialog = useUIStore((state) => state.showDeletionDialog);
   const setShowDeletionDialog = useUIStore((state) => state.setShowDeletionDialog);
   const providers = useConfigStore((state) => state.providers);
+  const modelsMetadata = useConfigStore((state) => state.modelsMetadata);
 
   const [defaultModel, setDefaultModel] = React.useState<string | undefined>();
   const [defaultVariant, setDefaultVariant] = React.useState<string | undefined>();
@@ -52,6 +53,7 @@ export const DefaultsSettings: React.FC = () => {
   const [smallModelUseDefault, setSmallModelUseDefault] = React.useState(true);
   const [smallModelOverride, setSmallModelOverride] = React.useState<string | undefined>();
   const [smallModelProviders, setSmallModelProviders] = React.useState<string[] | undefined>();
+  const [walkthroughModelOverride, setWalkthroughModelOverride] = React.useState<string | undefined>();
   const [isLoading, setIsLoading] = React.useState(true);
 
   const parsedModel = React.useMemo(() => getDisplayModel(defaultModel), [defaultModel]);
@@ -65,6 +67,7 @@ export const DefaultsSettings: React.FC = () => {
           defaultAgent?: string;
           smallModelUseDefault?: boolean;
           smallModelOverride?: string;
+          walkthroughModelOverride?: string;
         } | null = null;
 
         if (!data) {
@@ -84,6 +87,8 @@ export const DefaultsSettings: React.FC = () => {
                   defaultAgent: typeof settings.defaultAgent === 'string' ? settings.defaultAgent : undefined,
                   smallModelUseDefault: typeof raw.smallModelUseDefault === 'boolean' ? raw.smallModelUseDefault : undefined,
                   smallModelOverride: typeof raw.smallModelOverride === 'string' ? raw.smallModelOverride : undefined,
+                  walkthroughModelOverride:
+                    typeof raw.walkthroughModelOverride === 'string' ? raw.walkthroughModelOverride : undefined,
                 };
               }
             } catch {
@@ -123,6 +128,9 @@ export const DefaultsSettings: React.FC = () => {
           if (typeof data.smallModelOverride === 'string' && data.smallModelOverride.trim()) {
             setSmallModelOverride(data.smallModelOverride.trim());
           }
+          if (typeof data.walkthroughModelOverride === 'string' && data.walkthroughModelOverride.trim()) {
+            setWalkthroughModelOverride(data.walkthroughModelOverride.trim());
+          }
         }
       } catch (error) {
         console.warn('Failed to load defaults settings:', error);
@@ -236,10 +244,43 @@ export const DefaultsSettings: React.FC = () => {
     []
   );
 
+  const handleWalkthroughModelOverrideChange = React.useCallback(
+    async (providerId: string, modelId: string) => {
+      const newValue = providerId && modelId ? `${providerId}/${modelId}` : undefined;
+      setWalkthroughModelOverride(newValue);
+      try {
+        // Clearing the picker is how the user goes back to the small model, so
+        // an empty value is a real choice rather than a no-op.
+        await updateDesktopSettings({ walkthroughModelOverride: newValue ?? '' });
+      } catch (error) {
+        console.warn('Failed to save walkthrough model override:', error);
+      }
+    },
+    []
+  );
+
+  // The walkthrough cannot work at all without schema-shaped output, so models
+  // the catalog says cannot do it are hidden rather than offered and then
+  // refused. A missing capability is not a "no": roughly half the catalog omits
+  // the field, and those models usually work.
+  const isStructuredOutputCapable = React.useCallback(
+    (providerId: string, modelId: string) =>
+      modelsMetadata.get(`${providerId}/${modelId}`)?.structured_output !== false,
+    [modelsMetadata]
+  );
+
   const parsedSmallModel = React.useMemo(() => getDisplayModel(smallModelOverride), [smallModelOverride]);
+  const parsedWalkthroughModel = React.useMemo(
+    () => getDisplayModel(walkthroughModelOverride),
+    [walkthroughModelOverride]
+  );
 
   React.useEffect(() => {
-    if (smallModelUseDefault || smallModelProviders !== undefined) return;
+    // Both pickers filter by the same authenticated-provider list, so either
+    // one being open is reason enough to fetch it.
+    // Both pickers filter by the same authenticated-provider list, and the
+    // walkthrough picker is always visible, so this is always worth fetching.
+    if (smallModelProviders !== undefined) return;
     let cancelled = false;
     (async () => {
       try {
@@ -256,7 +297,7 @@ export const DefaultsSettings: React.FC = () => {
     return () => {
       cancelled = true;
     };
-  }, [smallModelUseDefault, smallModelProviders]);
+  }, [smallModelProviders]);
 
   const availableVariants = React.useMemo(() => {
     if (!parsedModel.providerId || !parsedModel.modelId) return [];
@@ -396,6 +437,32 @@ export const DefaultsSettings: React.FC = () => {
                 />
               </SettingsFieldRow>
             ) : null}
+
+            <SettingsInset className={SETTINGS_OPTION_STACK_CLASS}>
+              <div className="flex items-center gap-1.5">
+                <SettingsGroupTitle>
+                  {t('settings.openchamber.defaults.walkthroughModel.title')}
+                </SettingsGroupTitle>
+                <SettingsInfoHint>
+                  {t('settings.openchamber.defaults.walkthroughModel.description')}
+                </SettingsInfoHint>
+              </div>
+
+              <SettingsFieldRow
+                settingsItem="sessions.walkthrough-model"
+                label={t('settings.openchamber.defaults.walkthroughModel.overrideModel')}
+              >
+                <ModelSelector
+                  providerId={parsedWalkthroughModel.providerId}
+                  modelId={parsedWalkthroughModel.modelId}
+                  onChange={handleWalkthroughModelOverrideChange}
+                  allowedProviderIds={smallModelProviders}
+                  isModelAllowed={isStructuredOutputCapable}
+                  placeholder={t('settings.openchamber.defaults.walkthroughModel.usesSmallModel')}
+                  className={SETTINGS_CUSTOM_TRIGGER_CLASS}
+                />
+              </SettingsFieldRow>
+            </SettingsInset>
           </div>
         </div>
       </SettingsSection>

packages/ui/src/components/session/DirectoryExplorerDialog.tsx

@@ -711,7 +711,9 @@ export const DirectoryExplorerDialog: React.FC<DirectoryExplorerDialogProps> = (
         open={open}
         onClose={handleClose}
         title={t('directoryExplorerDialog.title')}
-        className="h-[88dvh] max-h-[720px] max-w-full"
+        // Height only — the width stays on MobileOverlayPanel's shared max-w-lg
+        // so this sheet matches every other mobile overlay on wide screens.
+        className="h-[88dvh] max-h-[720px]"
         contentMaxHeightClassName="flex-1"
         footer={<div className="flex flex-col gap-2">{renderFooter()}</div>}
       >

packages/ui/src/components/session/SessionDialogs.tsx

@@ -413,13 +413,7 @@ export const SessionDialogs: React.FC = () => {
                 const target = deleteDialog.sessions[0];
                 const success = isWorktreeDelete
                     ? await archiveSession(target.id)
-                    : await deleteSession(target.id, {
-                        // In "worktree" mode, remove the selected worktree explicitly below.
-                        // Don't try to derive worktree removal from per-session metadata (may be missing).
-                        archiveWorktree: false,
-                        deleteRemoteBranch: removeRemoteBranch,
-                        deleteLocalBranch,
-                    });
+                    : await deleteSession(target.id);
                 if (!success) {
                     toast.error(isWorktreeDelete
                         ? t('sessions.sidebar.session.archive.error')

packages/ui/src/components/session/sidebar/SessionNodeItem.tsx

@@ -1204,7 +1204,7 @@ function SessionNodeItemComponent(props: Props): React.ReactNode {
                       handleSessionDoubleClick(session.id, sessionTitle);
                     }}
                     className={cn(
-	                      'flex min-w-0 flex-1 cursor-pointer flex-col gap-0 overflow-hidden rounded-md text-left focus-visible:outline-none focus-visible:ring-2 focus-visible:ring-primary/50 text-foreground select-none transition-[padding]',
+	                      'flex min-w-0 flex-1 cursor-pointer flex-col gap-0 overflow-hidden text-left focus-visible:outline-none focus-visible:ring-2 focus-visible:ring-primary/50 text-foreground select-none transition-[padding]',
 	                      isTouchPressed && 'bg-interactive-hover/70',
                       alwaysShowActions
                         ? (isVSCode ? revealPaddingClass : alwaysActionPaddingClass)

packages/ui/src/components/ui/MobileOverlayPanel.tsx

@@ -119,6 +119,15 @@ export const MobileOverlayPanel: React.FC<MobileOverlayPanelProps> = ({
       role="dialog"
       aria-modal="true"
       onClick={onClose}
+      // The panel centers over the CHAT column, not the whole app: on a tablet
+      // the shell keeps a persistent sessions sidebar, and a sheet centered on
+      // the window reads as belonging to nothing. The shell publishes the
+      // column's insets; on phones they are 0 and this is a no-op. The scrim
+      // deliberately still covers everything.
+      style={{
+        paddingLeft: 'var(--oc-chat-inset-left, 0px)',
+        paddingRight: 'var(--oc-chat-inset-right, 0px)',
+      }}
     >
         <div
           className={cn(

packages/ui/src/components/views/DiffView.tsx

@@ -34,11 +34,14 @@ import { Icon } from "@/components/icon/Icon";
 import { getContextFileOpenFailureMessage, validateContextFileOpen } from '@/lib/contextFileOpenGuard';
 import { toAbsoluteFilePath } from '@/lib/path-utils';
 import { sessionEvents } from '@/lib/sessionEvents';
+import { findDiffScrollAnchor, getRestoredDiffScrollTop, type DiffScrollAnchor } from './diffScrollAnchor';
 import { useI18n } from '@/lib/i18n';
 import type { I18nKey } from '@/lib/i18n/store';
 import { fileDiffFromPatch } from '@/lib/diff/patchFileDiff';
 import { isVSCodeRuntime } from '@/lib/desktop';
 import { startReviewFlow } from '@/lib/reviewFlow';
+import { WALKTHROUGH_ACTION_CLASS } from '@/components/views/walkthrough/walkthroughAction';
+import { useWalkthroughStore } from '@/stores/useWalkthroughStore';
 import { useSessionUIStore } from '@/sync/session-ui-store';
 import { useSessionMessages } from '@/sync/sync-context';
 import { getFirstChangedModifiedLineFromPatch } from './diffPatchUtils';
@@ -961,6 +964,8 @@ export const DiffView: React.FC<DiffViewProps> = ({
     const { t } = useI18n();
     const { git, files } = useRuntimeAPIs();
     const effectiveDirectory = useEffectiveDirectory();
+    const openContextSurface = useUIStore((state) => state.openContextSurface);
+    const requestWalkthroughSource = useWalkthroughStore((state) => state.requestSource);
     const { screenWidth, isMobile } = useDeviceInfo();
 
     const isGitRepo = useIsGitRepo(effectiveDirectory ?? null);
@@ -969,6 +974,7 @@ export const DiffView: React.FC<DiffViewProps> = ({
     const setActiveDirectory = useGitStore((state) => state.setActiveDirectory);
     const ensureStatus = useGitStore((state) => state.ensureStatus);
     const fetchStatus = useGitStore((state) => state.fetchStatus);
+    const clearDiffCache = useGitStore((state) => state.clearDiffCache);
     const setDiff = useGitStore((state) => state.setDiff);
     const [displayFile, setDisplayFile] = React.useState<string | null>(null);
     const [displayFileStaged, setDisplayFileStaged] = React.useState(false);
@@ -977,6 +983,7 @@ export const DiffView: React.FC<DiffViewProps> = ({
     const [mountedStackedFiles, setMountedStackedFiles] = React.useState<Set<string>>(() => new Set());
     const [loadFullFiles, setLoadFullFiles] = React.useState(false);
     const [scrollRequestNonce, setScrollRequestNonce] = React.useState(0);
+    const [fileDiffRefreshNonce, setFileDiffRefreshNonce] = React.useState<Map<string, number>>(() => new Map());
     const [reviewDialogOpen, setReviewDialogOpen] = React.useState(false);
     const [reviewFlowSubmitting, setReviewFlowSubmitting] = React.useState(false);
     const [activeDiffScope, setActiveDiffScope] = React.useState(diffScope);
@@ -1003,6 +1010,9 @@ export const DiffView: React.FC<DiffViewProps> = ({
 
     const isMobileLayout = isMobile || screenWidth <= 768;
     const showReviewAction = Boolean(currentSessionId) && activeDiffScope !== 'turn' && !isMobileLayout && !isVSCodeRuntime();
+    // Same runtime and width rules as the rail surface: no point offering an
+    // entry point to a surface that cannot open here.
+    const showWalkthroughAction = activeDiffScope !== 'turn' && !isMobileLayout && !isVSCodeRuntime();
     const showFileSidebar = !hideStackedFileSidebar && !isMobileLayout && screenWidth >= 1024;
     const diffScrollRef = React.useRef<HTMLElement | null>(null);
     const fileSectionRefs = React.useRef(new Map<string, HTMLDivElement | null>());
@@ -1011,6 +1021,20 @@ export const DiffView: React.FC<DiffViewProps> = ({
     const shouldPinAfterAlignRef = React.useRef(false);
     const visibleSyncFrameRef = React.useRef<number | null>(null);
     const stackedStateScopeRef = React.useRef<string | null>(null);
+    const lastScrollAnchorRef = React.useRef<DiffScrollAnchor | null>(null);
+    const pendingScrollAnchorRestoreRef = React.useRef<DiffScrollAnchor | null>(null);
+
+    const captureScrollAnchor = React.useCallback((): DiffScrollAnchor | null => {
+        const scrollRoot = diffScrollRef.current;
+        if (!scrollRoot) return null;
+
+        const rootTop = scrollRoot.getBoundingClientRect().top;
+        const sections: Array<{ path: string; top: number }> = [];
+        for (const [path, node] of fileSectionRefs.current) {
+            if (node) sections.push({ path, top: node.getBoundingClientRect().top });
+        }
+        return findDiffScrollAnchor(rootTop, sections);
+    }, []);
 
     const cancelPendingScrollAlignment = React.useCallback(() => {
         pendingScrollTargetRef.current = null;
@@ -1164,13 +1188,17 @@ export const DiffView: React.FC<DiffViewProps> = ({
         const top = rootRect.top - STACKED_DIFF_MOUNT_MARGIN;
         const bottom = rootRect.bottom + STACKED_DIFF_MOUNT_MARGIN;
         const next: Record<string, boolean> = {};
+        const sectionPositions: Array<{ path: string; top: number }> = [];
 
         for (const [path, node] of fileSectionRefs.current) {
-            if (!node || !expandedFiles.has(path)) continue;
+            if (!node) continue;
             const rect = node.getBoundingClientRect();
+            sectionPositions.push({ path, top: rect.top });
+            if (!expandedFiles.has(path)) continue;
             if (rect.bottom < top || rect.top > bottom) continue;
             next[path] = true;
         }
+        lastScrollAnchorRef.current = findDiffScrollAnchor(rootRect.top, sectionPositions);
 
         setMountedStackedFiles((previous) => {
             let changed = false;
@@ -1252,9 +1280,40 @@ export const DiffView: React.FC<DiffViewProps> = ({
             if (normalizePath(hint.directory) !== normalizePath(effectiveDirectory)) {
                 return;
             }
-            void fetchStatus(effectiveDirectory, git);
+            if (hint.paths?.length) {
+                pendingScrollAnchorRestoreRef.current = captureScrollAnchor() ?? lastScrollAnchorRef.current;
+                clearDiffCache(effectiveDirectory, hint.paths);
+                setFileDiffRefreshNonce((previous) => {
+                    const next = new Map(previous);
+                    for (const path of hint.paths ?? []) {
+                        next.set(path, (next.get(path) ?? 0) + 1);
+                    }
+                    return next;
+                });
+            }
+            void fetchStatus(effectiveDirectory, git, { silent: true });
         });
-    }, [effectiveDirectory, fetchStatus, git]);
+    }, [captureScrollAnchor, clearDiffCache, effectiveDirectory, fetchStatus, git]);
+
+    React.useLayoutEffect(() => {
+        const anchor = pendingScrollAnchorRestoreRef.current;
+        if (!anchor) return;
+        pendingScrollAnchorRestoreRef.current = null;
+
+        const scrollRoot = diffScrollRef.current;
+        const node = fileSectionRefs.current.get(anchor.path);
+        if (!scrollRoot || !node) return;
+
+        const rootTop = scrollRoot.getBoundingClientRect().top;
+        const currentTopOffset = node.getBoundingClientRect().top - rootTop;
+        scrollRoot.scrollTop = getRestoredDiffScrollTop(
+            scrollRoot.scrollTop,
+            anchor.topOffset,
+            currentTopOffset,
+            scrollRoot.scrollHeight - scrollRoot.clientHeight,
+        );
+        lastScrollAnchorRef.current = anchor;
+    }, [fileDiffRefreshNonce]);
 
     // Handle pending diff file from external navigation
     React.useEffect(() => {
@@ -1392,11 +1451,8 @@ export const DiffView: React.FC<DiffViewProps> = ({
             return false;
         }
 
-        const rootRect = scrollRoot.getBoundingClientRect();
-        const nodeRect = node.getBoundingClientRect();
-        const delta = nodeRect.top - rootRect.top;
-        const maxTop = Math.max(0, scrollRoot.scrollHeight - scrollRoot.clientHeight);
-        scrollRoot.scrollTop = Math.min(maxTop, Math.max(0, scrollRoot.scrollTop + delta));
+        const scrollOffset = node.getBoundingClientRect().top - scrollRoot.getBoundingClientRect().top;
+        scrollRoot.scrollTo({ top: scrollRoot.scrollTop + scrollOffset, behavior: 'auto' });
         return true;
     }, []);
 
@@ -1408,14 +1464,16 @@ export const DiffView: React.FC<DiffViewProps> = ({
         const maxAttempts = 20;
         let cancelled = false;
 
-        const cancelPending = () => {
+        const cancelPending = (clearPinnedTarget = true) => {
             if (cancelled) {
                 return;
             }
             cancelled = true;
             pendingScrollTargetRef.current = null;
             shouldPinAfterAlignRef.current = false;
-            setPinnedStackedTarget(null);
+            if (clearPinnedTarget) {
+                setPinnedStackedTarget(null);
+            }
             if (pendingScrollFrameRef.current !== null) {
                 window.cancelAnimationFrame(pendingScrollFrameRef.current);
                 pendingScrollFrameRef.current = null;
@@ -1448,6 +1506,8 @@ export const DiffView: React.FC<DiffViewProps> = ({
 
             if (pinSelectedFileHeaderToTopOnNavigate && shouldPinAfterAlignRef.current) {
                 setPinnedStackedTarget(currentTarget);
+                cancelPending(false);
+                return;
             }
             cancelPending();
         };
@@ -1592,7 +1652,7 @@ export const DiffView: React.FC<DiffViewProps> = ({
                         <div className="flex flex-col [overflow-anchor:none]" data-diff-virtual-content>
                             {changedFiles.map((file) => (
                                 <MultiFileDiffEntry
-                                    key={file.path}
+                                    key={`${file.path}:${fileDiffRefreshNonce.get(file.path) ?? 0}`}
                                     directory={effectiveDirectory}
                                     file={file}
                                     layout={getLayoutForFile(file)}
@@ -1724,6 +1784,32 @@ export const DiffView: React.FC<DiffViewProps> = ({
                         </span>
                     </Button>
                 )}
+                {changedFiles.length > 0 && showWalkthroughAction && (
+                    <Button
+                        variant="outline"
+                        size="sm"
+                        onClick={() => {
+                            // Carry the scope across: opening the walkthrough
+                            // while looking at staged changes should review
+                            // staged changes, not whatever the panel showed last.
+                            const directory = effectiveDirectory ?? '';
+                            requestWalkthroughSource(directory, {
+                                kind: 'working-tree',
+                                scope: activeDiffScope === 'staged' || activeDiffScope === 'working'
+                                    ? activeDiffScope
+                                    : 'all',
+                            });
+                            openContextSurface(directory, 'walkthrough');
+                        }}
+                        className={cn('diff-toolbar__walkthrough-button h-7 flex-shrink-0 gap-1.5 px-2', WALKTHROUGH_ACTION_CLASS)}
+                        aria-label={t('walkthrough.action.open')}
+                    >
+                        <Icon name="route" className="size-4" />
+                        <span className="diff-toolbar__walkthrough-label typography-ui-label">
+                            {t('walkthrough.action.open')}
+                        </span>
+                    </Button>
+                )}
                 {changedFiles.length > 0 && (
                     <Tooltip>
                         <TooltipTrigger asChild>

packages/ui/src/components/views/FilesView.tsx

@@ -74,6 +74,7 @@ import { openDesktopFileInApp, openDesktopPath } from '@/lib/desktop';
 import { useOpenInAppsStore } from '@/stores/useOpenInAppsStore';
 import { eventMatchesShortcut, getEffectiveShortcutCombo } from '@/lib/shortcuts';
 import { useI18n } from '@/lib/i18n';
+import { sessionEvents } from '@/lib/sessionEvents';
 
 type FileNode = {
   name: string;
@@ -1655,6 +1656,12 @@ export const FilesView: React.FC<FilesViewProps> = ({ mode = 'full' }) => {
         return false;
       }
       setFileContent(draftContent);
+      if (root && isPathWithinRoot(selectedFile.path, root)) {
+        const relativePath = getDisplayPath(root, selectedFile.path);
+        if (relativePath) {
+          sessionEvents.requestGitRefresh({ directory: root, paths: [relativePath] });
+        }
+      }
       if (selectedFile?.path && isDrawioFile(selectedFile.path)) {
         diagramXmlRef.current = draftContent;
         diagramSavedXmlRef.current = draftContent;
@@ -1674,7 +1681,7 @@ export const FilesView: React.FC<FilesViewProps> = ({ mode = 'full' }) => {
     } finally {
       setIsSaving(false);
     }
-  }, [contentDetectedBinary, draftContent, fileContent, fileLoading, files, isDirty, loadedFileLineEnding, loadedFilePath, readFileStat, selectedFile, t]);
+  }, [contentDetectedBinary, draftContent, fileContent, fileLoading, files, isDirty, loadedFileLineEnding, loadedFilePath, readFileStat, root, selectedFile, t]);
 
   React.useEffect(() => {
     if (!isDirty) {

packages/ui/src/components/views/GitView.tsx

@@ -280,6 +280,7 @@ export const GitView: React.FC<GitViewProps> = ({ isActive }) => {
     setLogMaxCount,
     fetchIdentity,
     prefetchDiffs,
+    clearDiffCache,
     moveStatusPathsOptimistically,
     restoreStatus,
     bumpIndexRevision,
@@ -293,6 +294,7 @@ export const GitView: React.FC<GitViewProps> = ({ isActive }) => {
     setLogMaxCount: state.setLogMaxCount,
     fetchIdentity: state.fetchIdentity,
     prefetchDiffs: state.prefetchDiffs,
+    clearDiffCache: state.clearDiffCache,
     moveStatusPathsOptimistically: state.moveStatusPathsOptimistically,
     restoreStatus: state.restoreStatus,
     bumpIndexRevision: state.bumpIndexRevision,
@@ -861,9 +863,12 @@ export const GitView: React.FC<GitViewProps> = ({ isActive }) => {
       if (normalizePath(hint.directory) !== normalizePath(currentDirectory)) {
         return;
       }
-      void fetchStatus(currentDirectory, git);
+      if (hint.paths?.length) {
+        clearDiffCache(currentDirectory, hint.paths);
+      }
+      void fetchStatus(currentDirectory, git, { silent: true });
     });
-  }, [isActive, currentDirectory, fetchStatus, git]);
+  }, [isActive, clearDiffCache, currentDirectory, fetchStatus, git]);
 
   const refreshStatusAndBranches = React.useCallback(
     async (showErrors = true) => {
@@ -2019,14 +2024,14 @@ export const GitView: React.FC<GitViewProps> = ({ isActive }) => {
     }
   }, [currentDirectory, git, conflictOperation, refreshStatusAndBranches, refreshLog, clearConflictState, t]);
 
-  // Check if there are unresolved conflicts (files with 'U' status)
-  const hasUnresolvedConflicts = React.useMemo(() => {
-    if (!status?.files) return false;
-    return status.files.some((f) =>
+  // Count unresolved conflicts (files with 'U' status)
+  const conflictCount = React.useMemo(() => {
+    if (!status?.files) return 0;
+    return status.files.filter((f) =>
       (f.index === 'U' || f.working_dir === 'U') ||
       (f.index === 'A' && f.working_dir === 'A') ||
       (f.index === 'D' && f.working_dir === 'D')
-    );
+    ).length;
   }, [status?.files]);
 
   const handleContinueOperation = React.useCallback(async () => {
@@ -2350,7 +2355,7 @@ export const GitView: React.FC<GitViewProps> = ({ isActive }) => {
             onContinue={handleContinueOperation}
             onAbort={handleAbortOperation}
             onResolveWithAI={handleResolveWithAIFromBanner}
-            hasUnresolvedConflicts={hasUnresolvedConflicts}
+            conflictCount={conflictCount}
             isLoading={isLoading}
           />
         )}

packages/ui/src/components/views/diffScrollAnchor.test.ts

@@ -0,0 +1,25 @@
+import { describe, expect, test } from 'bun:test';
+
+import { findDiffScrollAnchor, getRestoredDiffScrollTop } from './diffScrollAnchor';
+
+describe('diff scroll anchoring', () => {
+  test('uses the last file section that reached the top of the viewport', () => {
+    expect(findDiffScrollAnchor(100, [
+      { path: 'third.ts', top: 240 },
+      { path: 'second.ts', top: 80 },
+      { path: 'first.ts', top: -200 },
+    ])).toEqual({ path: 'second.ts', topOffset: -20 });
+  });
+
+  test('uses the first section when no header reached the viewport top yet', () => {
+    expect(findDiffScrollAnchor(100, [
+      { path: 'first.ts', top: 140 },
+      { path: 'second.ts', top: 300 },
+    ])).toEqual({ path: 'first.ts', topOffset: 40 });
+  });
+
+  test('restores the prior section offset and clamps at the scroll boundary', () => {
+    expect(getRestoredDiffScrollTop(500, -20, 80, 1000)).toBe(600);
+    expect(getRestoredDiffScrollTop(950, -20, 80, 1000)).toBe(1000);
+  });
+});

packages/ui/src/components/views/diffScrollAnchor.ts

@@ -0,0 +1,35 @@
+export type DiffScrollAnchor = {
+  path: string;
+  topOffset: number;
+};
+
+export const findDiffScrollAnchor = (
+  rootTop: number,
+  sections: Array<{ path: string; top: number }>,
+): DiffScrollAnchor | null => {
+  if (sections.length === 0) return null;
+
+  let beforeTop: { path: string; top: number } | null = null;
+  let afterTop: { path: string; top: number } | null = null;
+  for (const section of sections) {
+    if (section.top <= rootTop) {
+      if (!beforeTop || section.top > beforeTop.top) beforeTop = section;
+    } else if (!afterTop || section.top < afterTop.top) {
+      afterTop = section;
+    }
+  }
+
+  const anchor = beforeTop ?? afterTop;
+  if (!anchor) return null;
+  return { path: anchor.path, topOffset: anchor.top - rootTop };
+};
+
+export const getRestoredDiffScrollTop = (
+  scrollTop: number,
+  previousTopOffset: number,
+  currentTopOffset: number,
+  maxScrollTop: number,
+): number => Math.min(
+  Math.max(0, maxScrollTop),
+  Math.max(0, scrollTop + currentTopOffset - previousTopOffset),
+);

packages/ui/src/components/views/git/InProgressOperationBanner.tsx

@@ -10,7 +10,7 @@ interface InProgressOperationBannerProps {
   onContinue: () => Promise<void>;
   onAbort: () => Promise<void>;
   onResolveWithAI?: () => void;
-  hasUnresolvedConflicts?: boolean;
+  conflictCount?: number;
   isLoading?: boolean;
 }
 
@@ -20,7 +20,7 @@ export const InProgressOperationBanner: React.FC<InProgressOperationBannerProps>
   onContinue,
   onAbort,
   onResolveWithAI,
-  hasUnresolvedConflicts = false,
+  conflictCount = 0,
   isLoading = false,
 }) => {
   const { t } = useI18n();
@@ -30,7 +30,7 @@ export const InProgressOperationBanner: React.FC<InProgressOperationBannerProps>
   const hasMergeInProgress = mergeInProgress && mergeInProgress.head;
   const hasRebaseInProgress = rebaseInProgress && (rebaseInProgress.headName || rebaseInProgress.onto);
   const operation = hasMergeInProgress ? 'merge' : hasRebaseInProgress ? 'rebase' : null;
-  
+
   if (!operation) {
     return null;
   }
@@ -54,54 +54,52 @@ export const InProgressOperationBanner: React.FC<InProgressOperationBannerProps>
   };
 
   const isProcessing = processingAction !== null;
+  const hasUnresolvedConflicts = conflictCount > 0;
 
   const operationLabel = operation === 'merge' ? t('gitView.operation.merge') : t('gitView.operation.rebase');
-  const operationIconName = operation === 'merge' ? 'git-merge' : 'git-branch';
 
   // Build description
   let description = '';
   if (mergeInProgress) {
-    description = mergeInProgress.message 
+    description = mergeInProgress.message
       ? t('gitView.operation.mergingMessage', { message: mergeInProgress.message })
       : t('gitView.operation.mergeInProgressWithHead', { head: mergeInProgress.head });
   } else if (rebaseInProgress) {
-    description = rebaseInProgress.headName 
+    description = rebaseInProgress.headName
       ? t('gitView.operation.rebasingOnto', { headName: rebaseInProgress.headName, onto: rebaseInProgress.onto || '' })
       : t('gitView.operation.rebaseInProgress');
   }
 
+  const title = !hasUnresolvedConflicts
+    ? t('gitView.operation.inProgressTitle', { operation: operationLabel })
+    : conflictCount === 1
+      ? t('gitView.operation.inProgressTitleOneConflict', { operation: operationLabel, count: conflictCount })
+      : t('gitView.operation.inProgressTitleManyConflicts', { operation: operationLabel, count: conflictCount });
+
+  const hint = hasUnresolvedConflicts
+    ? t('gitView.operation.resolveConflictsHint')
+    : t('gitView.operation.readyToContinueHint');
+
   return (
-    <div className="bg-[var(--status-warning-bg)] border border-[var(--status-warning)] rounded-lg p-3 mx-3 mt-3">
-      <div className="flex flex-col gap-3">
-        <div className="flex items-start gap-2 min-w-0">
-          <Icon name={operationIconName} className="size-4 text-[var(--status-warning)] shrink-0" />
-          <div className="min-w-0">
-            <p className="typography-label text-[var(--status-warning)]">
-              {t('gitView.operation.inProgressTitle', { operation: operationLabel })}
+    <div className="mx-4 mt-3 overflow-hidden rounded-lg border border-[var(--status-warning-border)]">
+      <div className="flex flex-col gap-3 p-3">
+        <div className="min-w-0">
+          <p className="typography-label text-[var(--status-warning)]">
+            {title}
+          </p>
+          {description && (
+            <p className="typography-micro break-words text-muted-foreground">
+              {description}
             </p>
-            {description && (
-              <p className="typography-micro text-muted-foreground truncate">
-                {description}
-              </p>
-            )}
-          </div>
+          )}
         </div>
 
-        <div className="flex flex-wrap items-center gap-2">
-          {hasUnresolvedConflicts && onResolveWithAI && (
-            <Button
-              variant="outline"
-              size="sm"
-              onClick={onResolveWithAI}
-              disabled={isProcessing || isLoading}
-              className="gap-1.5"
-            >
-              <Icon name="sparkling" className="size-4" />
-              {t('gitView.operation.resolveWithAi')}
-            </Button>
-          )}
+        <div className="flex flex-wrap items-center justify-between gap-2">
+          <p className="typography-micro min-w-0 flex-1 text-muted-foreground">
+            {hint}
+          </p>
 
-          {processingAction !== 'continue' && (
+          <div className="flex shrink-0 items-center gap-1.5">
             <Button
               variant="ghost"
               size="sm"
@@ -116,31 +114,36 @@ export const InProgressOperationBanner: React.FC<InProgressOperationBannerProps>
               )}
               {t('gitView.operation.abort')}
             </Button>
-          )}
 
-          {!hasUnresolvedConflicts && (
-            <Button
-              variant="default"
-              size="sm"
-              onClick={handleContinue}
-              disabled={isProcessing || isLoading}
-              className="gap-1.5"
-            >
-              {processingAction === 'continue' ? (
-                <Icon name="loader-4" className="size-4 animate-spin" />
-              ) : (
-                <Icon name="check" className="size-4" />
+            {hasUnresolvedConflicts
+              ? onResolveWithAI && (
+                <Button
+                  variant="default"
+                  size="sm"
+                  onClick={onResolveWithAI}
+                  disabled={isProcessing || isLoading}
+                >
+                  {t('gitView.operation.resolveWithAi')}
+                </Button>
+              )
+              : (
+                <Button
+                  variant="default"
+                  size="sm"
+                  onClick={handleContinue}
+                  disabled={isProcessing || isLoading}
+                  className="gap-1.5"
+                >
+                  {processingAction === 'continue' ? (
+                    <Icon name="loader-4" className="size-4 animate-spin" />
+                  ) : (
+                    <Icon name="check" className="size-4" />
+                  )}
+                  {t('gitView.operation.continue')}
+                </Button>
               )}
-              {t('gitView.operation.continue')}
-            </Button>
-          )}
+          </div>
         </div>
-
-        {hasUnresolvedConflicts && (
-          <p className="typography-micro text-[var(--status-warning)]">
-            {t('gitView.operation.resolveConflictsHint')}
-          </p>
-        )}
       </div>
     </div>
   );

packages/ui/src/components/views/git/PullRequestSection.tsx

@@ -21,6 +21,9 @@ import { MobileOverlayPanel } from '@/components/ui/MobileOverlayPanel';
 import { SimpleMarkdownRenderer } from '@/components/chat/MarkdownRenderer';
 import { Icon } from "@/components/icon/Icon";
 import { useUIStore } from '@/stores/useUIStore';
+import { useWalkthroughStore } from '@/stores/useWalkthroughStore';
+import { WALKTHROUGH_ACTION_CLASS } from '@/components/views/walkthrough/walkthroughAction';
+import { isVSCodeRuntime } from '@/lib/desktop';
 import { formatDateTimeForPreference } from '@/lib/timeFormat';
 import { useSessionUIStore } from '@/sync/session-ui-store';
 import { useInlineCommentDraftStore, type InlineCommentDraftTarget } from '@/stores/useInlineCommentDraftStore';
@@ -327,7 +330,12 @@ export const PullRequestSection: React.FC<{
   const setActiveMainTab = useUIStore((state) => state.setActiveMainTab);
   const currentSessionId = useSessionUIStore((state) => state.currentSessionId);
   const newSessionDraftOpen = useSessionUIStore((state) => Boolean(state.newSessionDraft?.open));
-  const { isMobile, hasTouchInput } = useDeviceInfo();
+  const { isMobile, hasTouchInput, screenWidth } = useDeviceInfo();
+  const openContextSurface = useUIStore((state) => state.openContextSurface);
+  const requestWalkthroughSource = useWalkthroughStore((state) => state.requestSource);
+  // Mirrors the rail's gating: the surface is not available on mobile widths or
+  // in VS Code, so neither is its entry point.
+  const showWalkthroughAction = !isMobile && screenWidth >= 768 && !isVSCodeRuntime();
 
   const openGitHubSettings = React.useCallback(() => {
     setSettingsPage('github');
@@ -1487,7 +1495,7 @@ export const PullRequestSection: React.FC<{
         </div>
 
         {pr ? (
-          <div className="flex min-w-0 items-center justify-between gap-2">
+          <div className="@container/pr-actions flex min-w-0 items-center justify-between gap-2">
             <div className="flex min-w-0 flex-wrap items-center gap-x-2 gap-y-1 typography-micro text-muted-foreground">
               <span style={{ color: prColorVar }}>{prStatusText}</span>
               {checks ? (
@@ -1503,6 +1511,23 @@ export const PullRequestSection: React.FC<{
               ) : null}
             </div>
             <div className="flex shrink-0 items-center gap-1.5">
+              {showWalkthroughAction ? (
+                <Button
+                  variant="outline"
+                  size="sm"
+                  className={cn('pr-actions__walkthrough-button h-7 shrink-0 gap-1.5 px-2', WALKTHROUGH_ACTION_CLASS)}
+                  onClick={() => {
+                    requestWalkthroughSource(directory, { kind: 'pr', number: pr.number });
+                    openContextSurface(directory, 'walkthrough');
+                  }}
+                  aria-label={t('walkthrough.action.open')}
+                >
+                  <Icon name="route" className="size-4" />
+                  <span className="pr-actions__walkthrough-label typography-ui-label">
+                    {t('walkthrough.action.open')}
+                  </span>
+                </Button>
+              ) : null}
               {canMerge && pr.draft && pr.state === 'open' ? (
                 <Tooltip>
                   <TooltipTrigger asChild>

packages/ui/src/components/views/walkthrough/WalkthroughBlocker.tsx

@@ -0,0 +1,166 @@
+import { useCallback, useEffect, useState } from 'react';
+import { Icon } from '@/components/icon/Icon';
+import { ModelSelector } from '@/components/sections/agents/ModelSelector';
+import { Button } from '@/components/ui/button';
+import { useI18n } from '@/lib/i18n';
+import { useConfigStore } from '@/stores/useConfigStore';
+import { runtimeFetch } from '@/lib/runtime-fetch';
+import { updateDesktopSettings } from '@/lib/persistence';
+import type { WalkthroughBlockedReason, WalkthroughModel } from '@/lib/walkthrough/types';
+
+interface WalkthroughBlockerProps {
+  reason: WalkthroughBlockedReason;
+  model?: WalkthroughModel;
+  requiredChars?: number;
+  availableChars?: number;
+  onRetry: () => void;
+}
+
+const modelLabel = (model?: WalkthroughModel) =>
+  model ? `${model.providerID}/${model.modelID}` : '';
+
+/**
+ * A refusal the user can act on. Both blocking reasons come down to "this small
+ * model cannot do this job", so the remedy — pick a different one — is offered
+ * in place rather than sending the user to Settings to guess.
+ */
+export const WalkthroughBlocker = ({
+  reason,
+  model,
+  requiredChars,
+  availableChars,
+  onRetry,
+}: WalkthroughBlockerProps) => {
+  const { t } = useI18n();
+  const modelsMetadata = useConfigStore((state) => state.modelsMetadata);
+  const [providers, setProviders] = useState<string[] | undefined>(undefined);
+  const [saving, setSaving] = useState(false);
+
+  // Every one of these means "this small model cannot do this job", so the
+  // remedy is the same: choose a different one, here, without a detour through
+  // Settings.
+  const canChooseModel = reason === 'context-too-small'
+    || reason === 'structured-output-unsupported'
+    || reason === 'output-exhausted';
+
+  useEffect(() => {
+    if (!canChooseModel || providers !== undefined) return;
+    let cancelled = false;
+    (async () => {
+      try {
+        const response = await runtimeFetch('/api/small-model', {
+          method: 'GET',
+          headers: { Accept: 'application/json' },
+        });
+        if (!response.ok) return;
+        const payload = (await response.json().catch(() => null)) as
+          | { authenticatedProviders?: unknown }
+          | null;
+        if (!cancelled && Array.isArray(payload?.authenticatedProviders)) {
+          setProviders(payload.authenticatedProviders.filter((id): id is string => typeof id === 'string'));
+        }
+      } catch {
+        // Leave undefined: the picker then offers every provider, which is a
+        // worse experience but not a broken one.
+      }
+    })();
+    return () => {
+      cancelled = true;
+    };
+  }, [canChooseModel, providers]);
+
+  const handleModelChange = useCallback(
+    async (providerId: string, modelId: string) => {
+      if (!providerId || !modelId || saving) return;
+      const value = `${providerId}/${modelId}`;
+      setSaving(true);
+      try {
+        // Scoped to this feature: fixing the walkthrough must not quietly
+        // change the model used for commit messages and recaps.
+        await updateDesktopSettings({ walkthroughModelOverride: value });
+        onRetry();
+      } catch (error) {
+        console.warn('Failed to save small model override:', error);
+      } finally {
+        setSaving(false);
+      }
+    },
+    [onRetry, saving]
+  );
+
+  // Offering a model the catalog already says cannot do this would just move
+  // the same refusal one click later.
+  const isStructuredOutputCapable = useCallback(
+    (providerId: string, modelId: string) =>
+      modelsMetadata.get(`${providerId}/${modelId}`)?.structured_output !== false,
+    [modelsMetadata]
+  );
+
+  const label = modelLabel(model);
+
+  const description = () => {
+    if (reason === 'no-model') return t('walkthrough.blocked.noModel.description');
+    if (reason === 'empty-diff') return t('walkthrough.blocked.emptyDiff.description');
+    if (reason === 'only-generated') return t('walkthrough.blocked.onlyGenerated.description');
+    if (reason === 'output-exhausted') {
+      return label
+        ? t('walkthrough.blocked.outputExhausted.description', { model: label })
+        : t('walkthrough.blocked.outputExhausted.descriptionUnknownModel');
+    }
+    if (reason === 'structured-output-unsupported') {
+      // Naming the model that was actually tried is the whole point of this
+      // screen; the unnamed variant is a defensive fallback, not the norm.
+      return label
+        ? t('walkthrough.blocked.structuredOutput.description', { model: label })
+        : t('walkthrough.blocked.structuredOutput.descriptionUnknownModel');
+    }
+    const required = Math.ceil((requiredChars ?? 0) / 1000);
+    const available = Math.ceil((availableChars ?? 0) / 1000);
+    return label
+      ? t('walkthrough.blocked.contextTooSmall.description', { model: label, required, available })
+      : t('walkthrough.blocked.contextTooSmall.descriptionUnknownModel', { required, available });
+  };
+
+  const title = () => {
+    if (reason === 'no-model') return t('walkthrough.blocked.noModel.title');
+    if (reason === 'empty-diff') return t('walkthrough.blocked.emptyDiff.title');
+    if (reason === 'only-generated') return t('walkthrough.blocked.onlyGenerated.title');
+    if (reason === 'output-exhausted') return t('walkthrough.blocked.outputExhausted.title');
+    if (reason === 'structured-output-unsupported') return t('walkthrough.blocked.structuredOutput.title');
+    return t('walkthrough.blocked.contextTooSmall.title');
+  };
+
+  return (
+    <div className="flex flex-1 flex-col items-center justify-center gap-3 p-8 text-center">
+      <Icon
+        name={reason === 'empty-diff' || reason === 'only-generated' ? 'information' : 'error-warning'}
+        className="size-6 text-muted-foreground"
+      />
+      <h3 className="typography-ui-label font-semibold text-foreground">{title()}</h3>
+      <p className="typography-meta max-w-md text-muted-foreground">{description()}</p>
+
+      {canChooseModel && (
+        <div className="flex flex-col items-center gap-2 pt-2">
+          <span className="typography-micro text-muted-foreground">
+            {t('walkthrough.blocked.chooseModel')}
+          </span>
+          <ModelSelector
+            providerId={model?.providerID ?? ''}
+            modelId={model?.modelID ?? ''}
+            onChange={(providerId, modelId) => {
+              void handleModelChange(providerId, modelId);
+            }}
+            allowedProviderIds={providers}
+            isModelAllowed={isStructuredOutputCapable}
+          />
+        </div>
+      )}
+
+      {(reason === 'empty-diff' || reason === 'only-generated') && (
+        <Button type="button" variant="outline" size="sm" onClick={onRetry}>
+          {t('walkthrough.action.refresh')}
+        </Button>
+      )}
+    </div>
+  );
+};

packages/ui/src/components/views/walkthrough/WalkthroughHunkRun.tsx

@@ -0,0 +1,50 @@
+import { memo, useMemo } from 'react';
+import { PierreDiffViewer } from '@/components/views/PierreDiffViewer';
+import { fileDiffFromPatch } from '@/lib/diff/patchFileDiff';
+import { getLanguageFromExtension } from '@/lib/toolHelpers';
+import { mergeRunPatch } from '@/lib/walkthrough/model';
+import type { WalkthroughHunk } from '@/lib/walkthrough/types';
+
+interface WalkthroughHunkRunProps {
+  path: string;
+  hunks: WalkthroughHunk[];
+  renderSideBySide: boolean;
+  wrapLines: boolean;
+}
+
+/**
+ * One file's contribution to a stop. Consecutive hunks are merged back into a
+ * single patch so the reader sees continuous code rather than a stack of
+ * one-hunk cards.
+ *
+ * Inline comments are on: a review you cannot annotate is a reader, not a tool.
+ * They work here because the merged patch keeps the original `@@` headers, so
+ * the line numbers a comment captures are the file's real ones and not offsets
+ * into an excerpt.
+ */
+export const WalkthroughHunkRun = memo(function WalkthroughHunkRun({
+  path,
+  hunks,
+  renderSideBySide,
+  wrapLines,
+}: WalkthroughHunkRunProps) {
+  const fileDiff = useMemo(() => {
+    const patch = mergeRunPatch(hunks);
+    return patch ? fileDiffFromPatch(path, patch) : undefined;
+  }, [hunks, path]);
+
+  if (!fileDiff) return null;
+
+  return (
+    <PierreDiffViewer
+      original=""
+      modified=""
+      fileDiff={fileDiff}
+      language={getLanguageFromExtension(path) || ''}
+      fileName={path}
+      renderSideBySide={renderSideBySide}
+      wrapLines={wrapLines}
+      layout="inline"
+    />
+  );
+});

packages/ui/src/components/views/walkthrough/WalkthroughStages.tsx

@@ -0,0 +1,61 @@
+import { Icon } from '@/components/icon/Icon';
+import { useI18n } from '@/lib/i18n';
+import type { I18nKey } from '@/lib/i18n';
+import { cn } from '@/lib/utils';
+import type { WalkthroughStageProgress } from './useWalkthroughStageProgress';
+
+interface WalkthroughStagesProps {
+  progress: WalkthroughStageProgress;
+}
+
+/**
+ * The wait is long and uneven — collecting a pull request diff is seconds of
+ * network, the model call is minutes — and a lone spinner makes those look
+ * identical. Naming the phase says which one you are waiting on, and that the
+ * cost has been committed once it reads "waiting on the model".
+ *
+ * No durations: a stopwatch on a step nobody can hurry adds pressure, not
+ * information. And no mention of the schema fallback — from out here it is the
+ * same wait, and naming our plumbing only invites the question of what it is.
+ */
+const STAGES: Array<{ labelKey: I18nKey }> = [
+  { labelKey: 'walkthrough.stage.collecting' },
+  { labelKey: 'walkthrough.stage.asking' },
+  { labelKey: 'walkthrough.stage.assembling' },
+];
+
+export const WalkthroughStages = ({ progress }: WalkthroughStagesProps) => {
+  const { t } = useI18n();
+  const { completedCount, activeIndex } = progress;
+
+  return (
+    <ul className="flex flex-col gap-2 text-left">
+      {STAGES.map((entry, index) => {
+        const isDone = index < completedCount;
+        const isActive = activeIndex === index;
+
+        return (
+          <li key={entry.labelKey} className="flex items-center gap-2">
+            <span className="flex size-4 shrink-0 items-center justify-center">
+              {isDone ? (
+                <Icon name="check" className="size-3.5 text-status-success" />
+              ) : isActive ? (
+                <Icon name="loader-4" className="size-3.5 animate-spin text-[var(--status-info)]" />
+              ) : (
+                <span className="size-1.5 rounded-full bg-surface-muted" />
+              )}
+            </span>
+            <span
+              className={cn(
+                'typography-meta',
+                isActive ? 'text-foreground' : isDone ? 'text-muted-foreground' : 'text-muted-foreground/60'
+              )}
+            >
+              {t(entry.labelKey)}
+            </span>
+          </li>
+        );
+      })}
+    </ul>
+  );
+};

packages/ui/src/components/views/walkthrough/WalkthroughStream.tsx

@@ -0,0 +1,269 @@
+import { memo, useCallback, useEffect, useMemo, useRef, useState } from 'react';
+import { Icon } from '@/components/icon/Icon';
+import { FileTypeIcon } from '@/components/icons/FileTypeIcon';
+import { Button } from '@/components/ui/button';
+import { useI18n } from '@/lib/i18n';
+import { groupHunksByFile } from '@/lib/walkthrough/model';
+import type { WalkthroughStopView, WalkthroughView } from '@/lib/walkthrough/model';
+import type { WalkthroughHunk, WalkthroughStopImportance } from '@/lib/walkthrough/types';
+import { cn } from '@/lib/utils';
+import { WalkthroughHunkRun } from './WalkthroughHunkRun';
+import { stopElementId } from './stopElementId';
+
+interface WalkthroughStreamProps {
+  view: WalkthroughView;
+  activeStopId: string | null;
+  scrollToStopId: string | null;
+  onActiveStopChange: (stopId: string) => void;
+  onScrollHandled: () => void;
+  renderSideBySide: boolean;
+  wrapLines: boolean;
+}
+
+const IMPORTANCE_CLASS: Record<WalkthroughStopImportance, string> = {
+  critical: 'bg-status-error/10 text-status-error',
+  normal: 'bg-surface-muted text-muted-foreground',
+  context: 'bg-surface-muted text-muted-foreground',
+};
+
+const StopHeader = ({ stopView }: { stopView: WalkthroughStopView }) => {
+  const { t } = useI18n();
+  const { stop } = stopView;
+
+  return (
+    <header className="flex flex-col gap-2 px-4 pt-5 pb-3">
+      <div className="flex items-center gap-2">
+        <span className="typography-micro flex h-5 min-w-5 shrink-0 items-center justify-center rounded-full bg-surface-muted px-1.5 tabular-nums text-muted-foreground">
+          {stopView.position}
+        </span>
+        <h3 className="typography-ui-label font-semibold text-foreground">{stop.title}</h3>
+        {/* Same height as the step badge, so a row with an importance pill is
+            exactly as tall as one without: vertical padding on a smaller type
+            size was pushing past the tallest element in the row. */}
+        {stop.importance !== 'normal' && (
+          <span className={cn('typography-micro flex h-5 items-center rounded px-1.5 leading-none', IMPORTANCE_CLASS[stop.importance])}>
+            {stop.importance === 'critical'
+              ? t('walkthrough.importance.critical')
+              : t('walkthrough.importance.context')}
+          </span>
+        )}
+      </div>
+      <p className="typography-body text-muted-foreground">{stop.prose}</p>
+      {stopView.isStale && (
+        <p className="typography-meta flex items-center gap-1.5 text-status-warning">
+          <Icon name="error-warning" className="size-3.5 shrink-0" />
+          {stopView.hunks.length === 0
+            ? t('walkthrough.stop.staleAll')
+            : t('walkthrough.stop.stalePartial', { count: stopView.missingHunkIds.length })}
+        </p>
+      )}
+    </header>
+  );
+};
+
+/**
+ * Sticky so the file you are reading stays named while you scroll through its
+ * hunks — the path is the main orientation cue in a long stream, and as a plain
+ * caption it was easy to scroll straight past.
+ */
+const FileHeader = ({ path }: { path: string }) => (
+  <div className="sticky top-0 z-10 flex items-center gap-1.5 border-b border-[var(--interactive-border)]/35 bg-[var(--surface-elevated)]/90 px-4 py-1.5 backdrop-blur-md supports-[backdrop-filter]:bg-[var(--surface-elevated)]/80">
+    <FileTypeIcon filePath={path} className="size-3.5 shrink-0" />
+    <span className="typography-meta truncate font-mono text-foreground">{path}</span>
+  </div>
+);
+
+const HunkRuns = ({
+  hunks,
+  renderSideBySide,
+  wrapLines,
+}: {
+  hunks: WalkthroughHunk[];
+  renderSideBySide: boolean;
+  wrapLines: boolean;
+}) => {
+  const runs = useMemo(() => groupHunksByFile(hunks), [hunks]);
+
+  return (
+    <>
+      {runs.map((run, index) => (
+        <div key={`${run.path}-${index}`}>
+          <FileHeader path={run.path} />
+          <WalkthroughHunkRun
+            path={run.path}
+            hunks={run.hunks}
+            renderSideBySide={renderSideBySide}
+            wrapLines={wrapLines}
+          />
+        </div>
+      ))}
+    </>
+  );
+};
+
+/**
+ * Everything the walkthrough covers, plus everything it does not, in one
+ * continuous scroll: a stop's explanation sits directly above the code it
+ * explains.
+ */
+export const WalkthroughStream = memo(function WalkthroughStream({
+  view,
+  activeStopId,
+  scrollToStopId,
+  onActiveStopChange,
+  onScrollHandled,
+  renderSideBySide,
+  wrapLines,
+}: WalkthroughStreamProps) {
+  const { t } = useI18n();
+  const scrollRef = useRef<HTMLDivElement | null>(null);
+  const [uncoveredOpen, setUncoveredOpen] = useState(false);
+
+  // Set while a click-driven jump is in flight. Without it the observer reports
+  // every stop the viewport passes over on the way to the target and the
+  // highlight ends up on whichever one happened to be reported last — the
+  // sidebar showing step 5 while the stream shows step 6.
+  const navigatingRef = useRef<string | null>(null);
+  const navigationTimerRef = useRef<number | null>(null);
+
+  useEffect(() => () => {
+    if (navigationTimerRef.current !== null) window.clearTimeout(navigationTimerRef.current);
+  }, []);
+
+  // Scrolling is driven by the DOM rather than a virtualizer: only the visible
+  // stops mount their diff viewers, and each stop is its own element, so there
+  // is nothing to translate between index space and pixel space.
+  useEffect(() => {
+    if (!scrollToStopId) return;
+    const element = document.getElementById(stopElementId(scrollToStopId));
+    if (element) {
+      navigatingRef.current = scrollToStopId;
+      // Instant, not smooth: picking a step is a jump to a known destination,
+      // and a long animation only creates a window for the highlight to drift
+      // through everything in between.
+      element.scrollIntoView({ behavior: 'auto', block: 'start' });
+
+      // The observer fires asynchronously after the jump, and an element that
+      // was already in view may not fire at all — so the mute is released on a
+      // timer as well as on arrival.
+      if (navigationTimerRef.current !== null) window.clearTimeout(navigationTimerRef.current);
+      navigationTimerRef.current = window.setTimeout(() => {
+        navigatingRef.current = null;
+        navigationTimerRef.current = null;
+      }, 250);
+    }
+    onScrollHandled();
+  }, [scrollToStopId, onScrollHandled]);
+
+  const handleIntersection = useCallback(
+    (entries: IntersectionObserverEntry[]) => {
+      const visible = entries
+        .filter((entry) => entry.isIntersecting)
+        .sort((a, b) => a.boundingClientRect.top - b.boundingClientRect.top)[0];
+      if (!visible) return;
+      const stopId = visible.target.getAttribute('data-stop-id');
+      if (!stopId) return;
+
+      const navigatingTo = navigatingRef.current;
+      if (navigatingTo) {
+        // Arrived: hand control back to free scrolling.
+        if (stopId === navigatingTo) navigatingRef.current = null;
+        return;
+      }
+
+      onActiveStopChange(stopId);
+    },
+    [onActiveStopChange]
+  );
+
+  useEffect(() => {
+    const root = scrollRef.current;
+    if (!root) return;
+
+    const observer = new IntersectionObserver(handleIntersection, {
+      root,
+      // Only count a stop as active once its header reaches the upper band of
+      // the viewport, so scrolling through a long diff does not flicker the
+      // active step back and forth.
+      rootMargin: '0px 0px -70% 0px',
+      threshold: 0,
+    });
+
+    for (const stopView of view.stops) {
+      const element = document.getElementById(stopElementId(stopView.stop.id));
+      if (element) observer.observe(element);
+    }
+
+    return () => observer.disconnect();
+  }, [handleIntersection, view.stops]);
+
+  const uncoveredRuns = useMemo(() => groupHunksByFile(view.uncoveredHunks), [view.uncoveredHunks]);
+
+  return (
+    <div
+      ref={scrollRef}
+      className="min-h-0 flex-1 overflow-y-auto"
+      data-diff-virtual-root
+      data-diff-virtual-content
+    >
+      {view.stops.map((stopView) => (
+        <section
+          key={stopView.stop.id}
+          id={stopElementId(stopView.stop.id)}
+          data-stop-id={stopView.stop.id}
+          className={cn(
+            'border-b border-border/60',
+            activeStopId === stopView.stop.id && 'bg-interactive-selection/5'
+          )}
+        >
+          <StopHeader stopView={stopView} />
+          {stopView.hunks.length > 0 ? (
+            <HunkRuns
+              hunks={stopView.hunks}
+              renderSideBySide={renderSideBySide}
+              wrapLines={wrapLines}
+            />
+          ) : (
+            <p className="typography-meta px-4 pb-4 text-muted-foreground">
+              {t('walkthrough.stop.noCode')}
+            </p>
+          )}
+        </section>
+      ))}
+
+      {view.uncoveredHunks.length > 0 && (
+        <section className="border-b border-border/60">
+          <Button
+            type="button"
+            variant="ghost"
+            className="h-auto w-full justify-start gap-2 px-4 py-3"
+            onClick={() => setUncoveredOpen((open) => !open)}
+            aria-expanded={uncoveredOpen}
+          >
+            <Icon name={uncoveredOpen ? 'arrow-down-s' : 'arrow-right-s'} className="size-4 shrink-0" />
+            <span className="typography-ui-label text-muted-foreground">
+              {t('walkthrough.uncovered.title', { count: view.uncoveredHunks.length })}
+            </span>
+          </Button>
+          {!uncoveredOpen && (
+            <p className="typography-meta px-4 pb-3 pl-10 text-muted-foreground">
+              {t('walkthrough.uncovered.description')}
+            </p>
+          )}
+          {uncoveredOpen
+            && uncoveredRuns.map((run, index) => (
+              <div key={`${run.path}-${index}`}>
+                <FileHeader path={run.path} />
+                <WalkthroughHunkRun
+                  path={run.path}
+                  hunks={run.hunks}
+                  renderSideBySide={renderSideBySide}
+                  wrapLines={wrapLines}
+                />
+              </div>
+            ))}
+        </section>
+      )}
+    </div>
+  );
+});

packages/ui/src/components/views/walkthrough/WalkthroughToc.tsx

@@ -0,0 +1,150 @@
+import { memo, useEffect, useRef } from 'react';
+import { Icon } from '@/components/icon/Icon';
+import type { IconName } from '@/components/icon/icons';
+import { useI18n } from '@/lib/i18n';
+import { summarizeHunkFiles } from '@/lib/walkthrough/model';
+import type { WalkthroughStopView, WalkthroughView } from '@/lib/walkthrough/model';
+import type { WalkthroughChapterIcon } from '@/lib/walkthrough/types';
+import { cn } from '@/lib/utils';
+
+interface WalkthroughTocProps {
+  view: WalkthroughView;
+  activeStopId: string | null;
+  visitedStopIds: ReadonlySet<string>;
+  onSelectStop: (stopId: string) => void;
+  width: number;
+}
+
+const CHAPTER_ICONS: Record<WalkthroughChapterIcon, IconName> = {
+  bug: 'bug',
+  wrench: 'tools',
+  path: 'compass-3',
+  flask: 'flask',
+  doc: 'file-text',
+  gear: 'settings-3',
+};
+
+const TocStop = ({
+  stopView,
+  isActive,
+  isVisited,
+  onSelect,
+  activeRef,
+}: {
+  stopView: WalkthroughStopView;
+  isActive: boolean;
+  isVisited: boolean;
+  onSelect: () => void;
+  activeRef: React.Ref<HTMLButtonElement>;
+}) => {
+  const { t } = useI18n();
+  const files = summarizeHunkFiles(stopView.hunks);
+
+  return (
+    <li>
+      <button
+        ref={isActive ? activeRef : undefined}
+        type="button"
+        onClick={onSelect}
+        aria-current={isActive ? 'step' : undefined}
+        className={cn(
+          'flex w-full flex-col gap-1 rounded px-2 py-1.5 text-left transition-colors',
+          'hover:bg-interactive-hover',
+          isActive && 'bg-interactive-selection text-interactive-selection-foreground'
+        )}
+      >
+        <span className="flex items-center gap-2">
+          <span
+            className={cn(
+              // A pill rather than a fixed circle: two-digit steps were cramped
+              // and visibly off-centre in a square.
+              'typography-micro flex h-4 min-w-4 shrink-0 items-center justify-center rounded-full px-1 tabular-nums',
+              isActive
+                ? 'bg-interactive-selection-foreground/20'
+                : isVisited
+                  ? 'bg-status-success/15 text-status-success'
+                  : 'bg-surface-muted text-muted-foreground'
+            )}
+          >
+            {isVisited && !isActive ? <Icon name="check" className="size-2.5" /> : stopView.position}
+          </span>
+          <span className="typography-meta truncate font-medium">{stopView.stop.title}</span>
+          {stopView.isStale && (
+            <Icon
+              name="error-warning"
+              className="size-3 shrink-0 text-status-warning"
+              aria-label={t('walkthrough.stop.staleShort')}
+            />
+          )}
+        </span>
+        {files.length > 0 && (
+          <span className="typography-micro flex flex-col gap-0.5 pl-6 text-muted-foreground">
+            {files.slice(0, 3).map((file) => (
+              <span key={file.path} className="truncate font-mono">
+                {file.path}
+              </span>
+            ))}
+            {files.length > 3 && (
+              <span>{t('walkthrough.toc.moreFiles', { count: files.length - 3 })}</span>
+            )}
+          </span>
+        )}
+      </button>
+    </li>
+  );
+};
+
+export const WalkthroughToc = memo(function WalkthroughToc({
+  view,
+  activeStopId,
+  visitedStopIds,
+  onSelectStop,
+  width,
+}: WalkthroughTocProps) {
+  const { t } = useI18n();
+  const activeRef = useRef<HTMLButtonElement | null>(null);
+
+  // Scrolling the stream moves the active step, and past a certain point the
+  // highlighted row leaves the contents column entirely — the reader loses
+  // their place in the very thing meant to hold it. `nearest` keeps the move
+  // minimal, so clicking a row that is already visible does not jolt the list.
+  useEffect(() => {
+    activeRef.current?.scrollIntoView({ block: 'nearest' });
+  }, [activeStopId]);
+
+  return (
+    <nav
+      className="flex shrink-0 flex-col overflow-y-auto border-r border-border/60 p-2"
+      style={{ width }}
+    >
+      {view.walkthrough.focus && (
+        <p className="typography-meta px-2 pb-3 pt-1 text-muted-foreground">{view.walkthrough.focus}</p>
+      )}
+      {view.chapters.map(({ chapter, stops }) => (
+        <section key={chapter.id} className="pb-3">
+          <h4 className="typography-micro flex items-center gap-1.5 px-2 py-1 font-semibold uppercase tracking-wide text-muted-foreground">
+            <Icon name={CHAPTER_ICONS[chapter.icon] ?? 'file-text'} className="size-3 shrink-0" />
+            <span className="truncate">{chapter.title}</span>
+          </h4>
+          <ul className="flex flex-col gap-0.5">
+            {stops.map((stopView) => (
+              <TocStop
+                key={stopView.stop.id}
+                stopView={stopView}
+                isActive={activeStopId === stopView.stop.id}
+                isVisited={visitedStopIds.has(stopView.stop.id)}
+                onSelect={() => onSelectStop(stopView.stop.id)}
+                activeRef={activeRef}
+              />
+            ))}
+          </ul>
+        </section>
+      ))}
+      {view.uncoveredHunks.length > 0 && (
+        <p className="typography-micro mt-auto px-2 pt-3 text-muted-foreground">
+          {t('walkthrough.toc.uncovered', { count: view.uncoveredHunks.length })}
+        </p>
+      )}
+    </nav>
+  );
+});

packages/ui/src/components/views/walkthrough/WalkthroughView.tsx

@@ -0,0 +1,761 @@
+import { useCallback, useEffect, useMemo, useRef, useState } from 'react';
+import { Icon } from '@/components/icon/Icon';
+import { Button } from '@/components/ui/button';
+import {
+  DropdownMenu,
+  DropdownMenuContent,
+  DropdownMenuLabel,
+  DropdownMenuRadioGroup,
+  DropdownMenuRadioItem,
+  DropdownMenuSeparator,
+  DropdownMenuTrigger,
+} from '@/components/ui/dropdown-menu';
+import { useI18n, type Locale } from '@/lib/i18n';
+import { buildWalkthroughView } from '@/lib/walkthrough/model';
+import type { WalkthroughSource, WalkthroughWorkingTreeScope } from '@/lib/walkthrough/types';
+import { ModelSelector } from '@/components/sections/agents/ModelSelector';
+import { deriveBaseBranch } from '@/components/views/git/baseBranch';
+import { runtimeFetch } from '@/lib/runtime-fetch';
+import { useConfigStore } from '@/stores/useConfigStore';
+import { useGitBranches, useGitStatus } from '@/stores/useGitStore';
+import { useGitHubAuthStore } from '@/stores/useGitHubAuthStore';
+import {
+  getFreshestPrStatusForBranch,
+  getGitHubPrStatusKey,
+  useGitHubPrStatusStore,
+} from '@/stores/useGitHubPrStatusStore';
+import { useRuntimeAPIs } from '@/hooks/useRuntimeAPIs';
+import { useUIStore } from '@/stores/useUIStore';
+import { useWalkthroughStore } from '@/stores/useWalkthroughStore';
+import { cn } from '@/lib/utils';
+import { WalkthroughBlocker } from './WalkthroughBlocker';
+import { WALKTHROUGH_ACTION_CLASS } from './walkthroughAction';
+import { WalkthroughStages } from './WalkthroughStages';
+import { useWalkthroughStageProgress } from './useWalkthroughStageProgress';
+import { WalkthroughStream } from './WalkthroughStream';
+import { WalkthroughToc } from './WalkthroughToc';
+
+interface WalkthroughViewProps {
+  directory: string;
+}
+
+const SCOPES: WalkthroughWorkingTreeScope[] = ['all', 'staged', 'working'];
+
+// DropdownMenuLabel defaults to the same size and weight as its items, which
+// makes a heading read as another choice. This matches SelectLabel, the
+// treatment used by the worktree picker.
+const SCOPE_GROUP_LABEL_CLASS = 'typography-meta font-normal text-muted-foreground';
+
+// Below this the table of contents would squeeze the diff into uselessness, so
+// the stream takes the whole panel and the header arrows carry navigation.
+const TOC_MIN_PANEL_WIDTH = 720;
+const TOC_MIN_WIDTH = 180;
+// The diff is the point of the surface; the contents column may never take more
+// than half the panel no matter how far the user drags.
+const TOC_MAX_FRACTION = 0.5;
+
+// Below this the header controls wrap onto a second row and the labels squeeze
+// to two letters and an ellipsis, which reads as broken rather than dense. The
+// controls drop their text instead: every one of them carries an icon that
+// already identifies it.
+//
+// Every control in this row is 32px tall — `Button` size `sm` and the dropdown
+// trigger's `default` size are both h-8, so this is the design system's form
+// scale rather than a number picked here. Three heights in one row (28px
+// pickers, 32px action, 36px arrows) read as misalignment, not hierarchy.
+const HEADER_COMPACT_WIDTH = 680;
+
+export const WalkthroughView = ({ directory }: WalkthroughViewProps) => {
+  const { t, locale, locales, label } = useI18n();
+  const rootRef = useRef<HTMLDivElement | null>(null);
+  const [panelWidth, setPanelWidth] = useState(0);
+
+  // Panel width, not viewport width: this surface is resizable independently of
+  // the window.
+  useEffect(() => {
+    const element = rootRef.current;
+    if (!element || typeof ResizeObserver === 'undefined') return;
+    const observer = new ResizeObserver((entries) => {
+      setPanelWidth(entries[0]?.contentRect.width ?? 0);
+    });
+    observer.observe(element);
+    return () => observer.disconnect();
+  }, []);
+
+  const storedTocWidth = useUIStore((state) => state.walkthroughTocWidth);
+  const setStoredTocWidth = useUIStore((state) => state.setWalkthroughTocWidth);
+  const [draggingToc, setDraggingToc] = useState(false);
+
+  const showToc = panelWidth === 0 || panelWidth >= TOC_MIN_PANEL_WIDTH;
+  // Zero means the observer has not reported yet; assume there is room rather
+  // than rendering a compact header for one frame on every open.
+  const compactHeader = panelWidth > 0 && panelWidth < HEADER_COMPACT_WIDTH;
+  // Clamped on read rather than on write: the panel can be resized after the
+  // width was stored, and a remembered 400px column must not swallow a narrow
+  // panel.
+  const tocWidth = Math.min(
+    Math.max(storedTocWidth, TOC_MIN_WIDTH),
+    Math.max(TOC_MIN_WIDTH, (panelWidth || TOC_MIN_PANEL_WIDTH) * TOC_MAX_FRACTION)
+  );
+
+  const handleTocResizeStart = useCallback(
+    (event: React.PointerEvent<HTMLDivElement>) => {
+      event.preventDefault();
+      const startX = event.clientX;
+      const startWidth = tocWidth;
+      const maxWidth = Math.max(TOC_MIN_WIDTH, (rootRef.current?.clientWidth ?? 0) * TOC_MAX_FRACTION);
+      setDraggingToc(true);
+
+      const onMove = (moveEvent: PointerEvent) => {
+        const next = Math.min(maxWidth, Math.max(TOC_MIN_WIDTH, startWidth + moveEvent.clientX - startX));
+        setStoredTocWidth(next);
+      };
+      const onUp = () => {
+        setDraggingToc(false);
+        window.removeEventListener('pointermove', onMove);
+        window.removeEventListener('pointerup', onUp);
+        window.removeEventListener('pointercancel', onUp);
+      };
+
+      window.addEventListener('pointermove', onMove);
+      window.addEventListener('pointerup', onUp);
+      window.addEventListener('pointercancel', onUp);
+    },
+    [setStoredTocWidth, tocWidth]
+  );
+
+  const handleTocResizeKey = useCallback(
+    (event: React.KeyboardEvent<HTMLDivElement>) => {
+      const step = event.shiftKey ? 40 : 10;
+      const delta = event.key === 'ArrowLeft' ? -step : event.key === 'ArrowRight' ? step : 0;
+      if (delta === 0) return;
+      event.preventDefault();
+      const maxWidth = Math.max(TOC_MIN_WIDTH, (rootRef.current?.clientWidth ?? 0) * TOC_MAX_FRACTION);
+      setStoredTocWidth(Math.min(maxWidth, Math.max(TOC_MIN_WIDTH, tocWidth + delta)));
+    },
+    [setStoredTocWidth, tocWidth]
+  );
+  const [scope, setScope] = useState<WalkthroughWorkingTreeScope>('all');
+  const [activeStopId, setActiveStopId] = useState<string | null>(null);
+  const [scrollToStopId, setScrollToStopId] = useState<string | null>(null);
+  const [visitedStopIds, setVisitedStopIds] = useState<ReadonlySet<string>>(() => new Set());
+
+  const diffLayoutPreference = useUIStore((state) => state.diffLayoutPreference);
+  const wrapLines = useUIStore((state) => state.diffWrapLines);
+  // The walkthrough column is narrower than the diff surface and stops are read
+  // top-to-bottom, so `dynamic` resolves to inline here rather than guessing
+  // from the window width.
+  const renderSideBySide = diffLayoutPreference === 'side-by-side';
+
+  const requestedSource = useWalkthroughStore((state) => state.requestedSource[directory]);
+  const clearRequestedSource = useWalkthroughStore((state) => state.clearRequestedSource);
+
+  const status = useGitStatus(directory || null);
+  const branches = useGitBranches(directory || null);
+
+  // The branch source reviews everything on this branch that is not on its
+  // base. Three-dot semantics server-side mean merges from the base are
+  // already excluded.
+  const currentBranch = status?.current ?? null;
+  const branchSource = useMemo<WalkthroughSource | null>(() => {
+    const headRef = currentBranch;
+    if (!headRef) return null;
+    const all = branches?.all ?? [];
+    const localBranches = all.filter((name) => !name.startsWith('remotes/'));
+    const remoteNames = new Set(
+      all
+        .filter((name) => name.startsWith('remotes/'))
+        .map((name) => name.slice('remotes/'.length).split('/')[0])
+        .filter(Boolean)
+    );
+    const baseRef = deriveBaseBranch({ remoteNames, localBranches });
+    if (!baseRef || baseRef === headRef) return null;
+    return { kind: 'branch', baseRef, headRef };
+  }, [branches, currentBranch]);
+
+  // The pull request for this branch used to appear only after visiting the PR
+  // panel, because nothing else asked GitHub about it. Ask here too: the status
+  // store already dedupes by signature and throttles by TTL, so several panels
+  // wanting the same answer produce one request.
+  const { github } = useRuntimeAPIs();
+  const githubConnected = useGitHubAuthStore((state) => state.status?.connected ?? false);
+  const githubAuthChecked = useGitHubAuthStore((state) => state.hasChecked);
+  const ensurePrStatusEntry = useGitHubPrStatusStore((state) => state.ensureEntry);
+  const setPrStatusParams = useGitHubPrStatusStore((state) => state.setParams);
+  const refreshPrStatusTargets = useGitHubPrStatusStore((state) => state.refreshTargets);
+
+  useEffect(() => {
+    if (!directory || !currentBranch || !githubAuthChecked || !githubConnected) return;
+    const key = getGitHubPrStatusKey(directory, currentBranch);
+    ensurePrStatusEntry(key);
+    setPrStatusParams(key, {
+      directory,
+      branch: currentBranch,
+      remoteName: null,
+      canShow: true,
+      github,
+      githubAuthChecked,
+      githubConnected,
+    });
+    void refreshPrStatusTargets([{ directory, branch: currentBranch, remoteName: null }]);
+  }, [
+    currentBranch,
+    directory,
+    ensurePrStatusEntry,
+    github,
+    githubAuthChecked,
+    githubConnected,
+    refreshPrStatusTargets,
+    setPrStatusParams,
+  ]);
+
+  // Selecting the number rather than the entry map: a primitive keeps this
+  // panel out of every unrelated PR status update.
+  const branchPrNumber = useGitHubPrStatusStore((state) => (
+    directory && currentBranch
+      ? getFreshestPrStatusForBranch(state.entries, directory, currentBranch)?.pr?.number ?? null
+      : null
+  ));
+
+  const source = useMemo<WalkthroughSource>(
+    () => requestedSource ?? { kind: 'working-tree', scope },
+    [requestedSource, scope]
+  );
+
+  // Offer whichever pull request we know about: the one already selected, or
+  // the one this branch has.
+  const prSource = useMemo<Extract<WalkthroughSource, { kind: 'pr' }> | null>(() => {
+    if (source.kind === 'pr') return source;
+    return branchPrNumber ? { kind: 'pr', number: branchPrNumber } : null;
+  }, [branchPrNumber, source]);
+
+  const selectWorkingTree = useCallback(
+    (value: WalkthroughWorkingTreeScope) => {
+      clearRequestedSource(directory);
+      setScope(value);
+    },
+    [clearRequestedSource, directory]
+  );
+  const entry = useWalkthroughStore((state) => state.getEntry(directory, source));
+  const load = useWalkthroughStore((state) => state.load);
+  const generate = useWalkthroughStore((state) => state.generate);
+  const cancel = useWalkthroughStore((state) => state.cancel);
+  const requestSource = useWalkthroughStore((state) => state.requestSource);
+  const selectModel = useWalkthroughStore((state) => state.selectModel);
+  const selectedModel = useWalkthroughStore((state) => state.getSelectedModel(directory, source));
+  const selectLanguage = useWalkthroughStore((state) => state.selectLanguage);
+  const selectedLanguage = useWalkthroughStore((state) => state.getSelectedLanguage(directory, source));
+
+  // Explicit pick first, then the language the walkthrough on screen is
+  // actually written in, then the interface locale. The middle step matters for
+  // the same reason it does for the model: reopening a review should describe
+  // what is there, not what a fresh one would be.
+  const generatedLanguage = entry.result?.language;
+  const activeLanguage: Locale = (
+    selectedLanguage && locales.includes(selectedLanguage as Locale)
+      ? (selectedLanguage as Locale)
+      : generatedLanguage && locales.includes(generatedLanguage as Locale)
+        ? (generatedLanguage as Locale)
+        : locale
+  );
+
+  // Reloads on a model or language change: whether this diff fits, and whether
+  // the model can produce structured output, are answers about a specific
+  // request — and the language instruction is part of that request.
+  useEffect(() => {
+    void load(directory, source, { language: activeLanguage });
+  }, [activeLanguage, directory, load, source, selectedModel]);
+
+  const view = useMemo(() => buildWalkthroughView(entry.result), [entry.result]);
+
+  // A new walkthrough is a new reading path: keeping the old progress would
+  // mark stops as visited that the user has never seen.
+  const generatedAt = entry.result?.generatedAt;
+  const lastGeneratedAt = useRef<string | undefined>(undefined);
+  useEffect(() => {
+    if (lastGeneratedAt.current === generatedAt) return;
+    lastGeneratedAt.current = generatedAt;
+    setVisitedStopIds(new Set());
+    setActiveStopId(view?.stops[0]?.stop.id ?? null);
+  }, [generatedAt, view]);
+
+  const handleActiveStopChange = useCallback((stopId: string) => {
+    setActiveStopId(stopId);
+    setVisitedStopIds((visited) => {
+      if (visited.has(stopId)) return visited;
+      const next = new Set(visited);
+      next.add(stopId);
+      return next;
+    });
+  }, []);
+
+  const handleSelectStop = useCallback(
+    (stopId: string) => {
+      handleActiveStopChange(stopId);
+      setScrollToStopId(stopId);
+    },
+    [handleActiveStopChange]
+  );
+
+  const step = useCallback(
+    (delta: number) => {
+      if (!view || view.stops.length === 0) return;
+      const currentIndex = view.stops.findIndex((stop) => stop.stop.id === activeStopId);
+      const nextIndex = Math.min(view.stops.length - 1, Math.max(0, (currentIndex < 0 ? 0 : currentIndex) + delta));
+      handleSelectStop(view.stops[nextIndex].stop.id);
+    },
+    [activeStopId, handleSelectStop, view]
+  );
+
+  const [sourceMenuOpen, setSourceMenuOpen] = useState(false);
+  const [languageMenuOpen, setLanguageMenuOpen] = useState(false);
+  const sourceValue = source.kind === 'working-tree' ? source.scope : source.kind;
+  const sourceLabel = source.kind === 'branch'
+    ? t('walkthrough.scope.branch')
+    : source.kind === 'pr'
+      ? t('walkthrough.scope.pullRequest', { number: source.number })
+      : scope === 'all'
+        ? t('walkthrough.scope.all')
+        : scope === 'staged'
+          ? t('walkthrough.scope.staged')
+          : t('walkthrough.scope.working');
+
+  // Explicit pick first, then the model that actually produced what is on
+  // screen, then whatever settings resolve to. The middle step is what makes
+  // reopening a review show the model behind it rather than the default.
+  const activeModel = selectedModel
+    ?? (entry.result?.model ? `${entry.result.model.providerID}/${entry.result.model.modelID}` : undefined)
+    ?? (entry.readiness?.model ? `${entry.readiness.model.providerID}/${entry.readiness.model.modelID}` : undefined);
+  const [activeProviderId, ...activeModelParts] = (activeModel ?? '').split('/');
+  const activeModelId = activeModelParts.join('/');
+
+  const modelsMetadata = useConfigStore((state) => state.modelsMetadata);
+  const [modelProviders, setModelProviders] = useState<string[] | undefined>(undefined);
+
+  useEffect(() => {
+    if (modelProviders !== undefined) return;
+    let cancelled = false;
+    (async () => {
+      try {
+        const response = await runtimeFetch('/api/small-model', {
+          method: 'GET',
+          headers: { Accept: 'application/json' },
+        });
+        if (!response.ok) return;
+        const payload = (await response.json().catch(() => null)) as { authenticatedProviders?: unknown } | null;
+        if (!cancelled && Array.isArray(payload?.authenticatedProviders)) {
+          setModelProviders(payload.authenticatedProviders.filter((id): id is string => typeof id === 'string'));
+        }
+      } catch {
+        // Leave undefined: the picker then offers every provider, which is
+        // worse but not broken.
+      }
+    })();
+    return () => {
+      cancelled = true;
+    };
+  }, [modelProviders]);
+
+  const isStructuredOutputCapable = useCallback(
+    (providerId: string, modelId: string) =>
+      modelsMetadata.get(`${providerId}/${modelId}`)?.structured_output !== false,
+    [modelsMetadata]
+  );
+
+  // Only generation is worth interrupting. A read is a few hundred milliseconds
+  // of git with nothing to cancel, and offering a Cancel button for it made the
+  // action flicker every time the model or language changed.
+  const isGeneratingEntry = entry.status === 'generating';
+
+  // What is on screen versus what is being asked for. A read that has settled
+  // is the only thing that can answer this: while one is in flight the panel is
+  // still showing the previous answer, and a banner claiming something is
+  // missing before we know would be the same flicker in another place.
+  const shownModel = entry.result?.model
+    ? `${entry.result.model.providerID}/${entry.result.model.modelID}`
+    : undefined;
+  const shownLanguage = entry.result?.language;
+  const shownLocale = shownLanguage && locales.includes(shownLanguage as Locale)
+    ? (shownLanguage as Locale)
+    : undefined;
+  const settled = entry.status === 'ready' && Boolean(view);
+  // An entry written before walkthroughs had a language carries none. Unknown
+  // is not the same as different, so it is not reported as missing.
+  const languageMissing = settled && Boolean(shownLocale) && shownLocale !== activeLanguage;
+  const modelMissing = settled && Boolean(shownModel) && Boolean(activeModel) && shownModel !== activeModel;
+
+  // The stage list outlives the work by a beat. Assembling takes milliseconds,
+  // so without this the result replaces the list before the last step is ever
+  // seen finishing — the user is told about a step they never observe.
+  const stageProgress = useWalkthroughStageProgress(entry.stage, entry.status === 'generating');
+
+  // Only a generation that started from an empty panel gets held: regenerating
+  // over an existing walkthrough keeps the stream on screen with a banner, and
+  // hiding readable content to show a progress list would be a downgrade.
+  const startedFromEmptyRef = useRef(false);
+  const previousStatusRef = useRef(entry.status);
+  useEffect(() => {
+    if (previousStatusRef.current !== 'generating' && entry.status === 'generating') {
+      startedFromEmptyRef.current = !view;
+    }
+    previousStatusRef.current = entry.status;
+  }, [entry.status, view]);
+
+  const showStages = startedFromEmptyRef.current
+    && (entry.status === 'generating' || stageProgress.holding);
+  const blockedReason = entry.error?.code === 'context-too-small'
+    || entry.error?.code === 'structured-output-unsupported'
+    || entry.error?.code === 'no-model'
+    || entry.error?.code === 'empty-diff'
+    || entry.error?.code === 'only-generated'
+    || entry.error?.code === 'output-exhausted'
+    ? entry.error.code
+    : entry.readiness && !entry.readiness.ready && !view
+      ? entry.readiness.reason
+      : undefined;
+
+  // Both sources carry the model that was tried; the error is the more specific
+  // one when generation actually ran.
+  const blockedModel = entry.error?.model ?? entry.readiness?.model;
+  const blockedRequiredChars = entry.error?.requiredChars ?? entry.readiness?.requiredChars;
+  const blockedAvailableChars = entry.error?.availableChars ?? entry.readiness?.availableChars;
+
+  const handleGenerate = useCallback(
+    (force: boolean) => {
+      void generate(directory, source, { force, language: activeLanguage });
+    },
+    [activeLanguage, directory, generate, source]
+  );
+
+  return (
+    <div ref={rootRef} className="flex h-full min-h-0 flex-col">
+      <header className="flex shrink-0 flex-wrap items-center gap-2 border-b border-border/60 px-3 py-2">
+        <DropdownMenu open={sourceMenuOpen} onOpenChange={setSourceMenuOpen}>
+          <DropdownMenuTrigger asChild>
+            <button
+              type="button"
+              className="flex h-8 flex-shrink-0 items-center gap-1.5 rounded-md px-2 typography-ui-label font-semibold text-foreground outline-none hover:bg-interactive-hover focus-visible:ring-2 focus-visible:ring-ring"
+              aria-label={t('walkthrough.scope.selectorAria')}
+            >
+              <span className="whitespace-nowrap">{sourceLabel}</span>
+              <Icon name="arrow-down-s" className="size-4 flex-shrink-0 opacity-60" />
+            </button>
+          </DropdownMenuTrigger>
+          <DropdownMenuContent align="start" className="w-48">
+            <DropdownMenuRadioGroup
+              value={sourceValue}
+              onValueChange={(value) => {
+                setSourceMenuOpen(false);
+                if (value === 'branch') {
+                  if (branchSource) requestSource(directory, branchSource);
+                  return;
+                }
+                if (value === 'pr') {
+                  if (prSource) requestSource(directory, prSource);
+                  return;
+                }
+                selectWorkingTree(value as WalkthroughWorkingTreeScope);
+              }}
+            >
+              {/* Grouped so "everything" is visibly scoped to uncommitted work:
+                  on its own next to "This branch" it read as "all changes that
+                  exist", which is the opposite of what it selects. */}
+              <DropdownMenuLabel className={SCOPE_GROUP_LABEL_CLASS}>
+                {t('walkthrough.scope.group.workingTree')}
+              </DropdownMenuLabel>
+              {SCOPES.map((value) => (
+                <DropdownMenuRadioItem key={value} value={value}>
+                  {value === 'all'
+                    ? t('walkthrough.scope.all')
+                    : value === 'staged'
+                      ? t('walkthrough.scope.staged')
+                      : t('walkthrough.scope.working')}
+                </DropdownMenuRadioItem>
+              ))}
+              {(branchSource || prSource) && (
+                <>
+                  <DropdownMenuSeparator />
+                  <DropdownMenuLabel className={SCOPE_GROUP_LABEL_CLASS}>
+                    {t('walkthrough.scope.group.committed')}
+                  </DropdownMenuLabel>
+                </>
+              )}
+              {branchSource && (
+                <DropdownMenuRadioItem value="branch">
+                  {t('walkthrough.scope.branch')}
+                </DropdownMenuRadioItem>
+              )}
+              {prSource && (
+                <DropdownMenuRadioItem value="pr">
+                  {t('walkthrough.scope.pullRequest', { number: prSource.number })}
+                </DropdownMenuRadioItem>
+              )}
+            </DropdownMenuRadioGroup>
+          </DropdownMenuContent>
+        </DropdownMenu>
+
+        <div className="ml-auto flex min-w-0 items-center gap-1">
+          {/* A walkthrough nobody can read is worth nothing, so the prose
+              language is a per-review choice like the model — defaulting to the
+              interface language, which is the best evidence of what the reader
+              reads. */}
+          <DropdownMenu open={languageMenuOpen} onOpenChange={setLanguageMenuOpen}>
+            <DropdownMenuTrigger asChild>
+              <button
+                type="button"
+                className="flex h-8 min-w-0 flex-shrink items-center gap-1.5 rounded-md px-2 typography-ui-label text-muted-foreground outline-none hover:bg-interactive-hover hover:text-foreground focus-visible:ring-2 focus-visible:ring-ring"
+                aria-label={t('walkthrough.language.selectorAria')}
+                title={compactHeader ? label(activeLanguage) : undefined}
+              >
+                <Icon name="global" className="size-4 flex-shrink-0 opacity-70" />
+                {!compactHeader && (
+                  <>
+                    <span className="truncate">{label(activeLanguage)}</span>
+                    <Icon name="arrow-down-s" className="size-4 flex-shrink-0 opacity-60" />
+                  </>
+                )}
+              </button>
+            </DropdownMenuTrigger>
+            <DropdownMenuContent align="end" className="w-48">
+              <DropdownMenuLabel className={SCOPE_GROUP_LABEL_CLASS}>
+                {t('walkthrough.language.menuLabel')}
+              </DropdownMenuLabel>
+              <DropdownMenuRadioGroup
+                value={activeLanguage}
+                onValueChange={(value) => {
+                  setLanguageMenuOpen(false);
+                  selectLanguage(directory, source, value);
+                }}
+              >
+                {locales.map((value) => (
+                  <DropdownMenuRadioItem key={value} value={value}>
+                    {label(value)}
+                  </DropdownMenuRadioItem>
+                ))}
+              </DropdownMenuRadioGroup>
+            </DropdownMenuContent>
+          </DropdownMenu>
+
+          {/* Choosing a roomier model for a risky change is a per-review call,
+              so this is panel state rather than a settings edit. */}
+          <ModelSelector
+            providerId={activeProviderId ?? ''}
+            modelId={activeModelId}
+            onChange={(providerId, modelId) => {
+              selectModel(directory, source, providerId && modelId ? `${providerId}/${modelId}` : null);
+            }}
+            allowedProviderIds={modelProviders}
+            isModelAllowed={isStructuredOutputCapable}
+            tooltipsEnabled={false}
+            dropdownPortalToBody
+            compact={compactHeader}
+            className={cn('h-8 min-w-0', !compactHeader && 'max-w-48')}
+          />
+          {view && (
+            <>
+              <Button
+                type="button"
+                variant="ghost"
+                size="sm"
+                aria-label={t('walkthrough.action.previous')}
+                onClick={() => step(-1)}
+              >
+                <Icon name="arrow-right-s" className="size-4 rotate-180" />
+              </Button>
+              <Button
+                type="button"
+                variant="ghost"
+                size="sm"
+                aria-label={t('walkthrough.action.next')}
+                onClick={() => step(1)}
+              >
+                <Icon name="arrow-right-s" className="size-4" />
+              </Button>
+            </>
+          )}
+
+          {isGeneratingEntry ? (
+            <Button
+              type="button"
+              variant="outline"
+              size="sm"
+              aria-label={compactHeader ? t('walkthrough.action.cancel') : undefined}
+              title={compactHeader ? t('walkthrough.action.cancel') : undefined}
+              onClick={() => cancel(directory, source)}
+            >
+              {compactHeader
+                ? <Icon name="stop" className="size-3.5" />
+                : t('walkthrough.action.cancel')}
+            </Button>
+          ) : (
+            <Button
+              type="button"
+              variant="outline"
+              size="sm"
+              className={WALKTHROUGH_ACTION_CLASS}
+              aria-label={compactHeader
+                ? (view ? t('walkthrough.action.regenerate') : t('walkthrough.action.generate'))
+                : undefined}
+              title={compactHeader
+                ? (view ? t('walkthrough.action.regenerate') : t('walkthrough.action.generate'))
+                : undefined}
+              onClick={() => handleGenerate(Boolean(view))}
+            >
+              <Icon name={view ? 'refresh' : 'route'} className="size-3.5" />
+              {!compactHeader && (view ? t('walkthrough.action.regenerate') : t('walkthrough.action.generate'))}
+            </Button>
+          )}
+        </div>
+      </header>
+
+      {/* While regenerating over an existing walkthrough the stream keeps showing
+          the old content, so the only other signal would be the button swapping
+          to Cancel — far too quiet for something that runs for tens of seconds. */}
+      {entry.status === 'generating' && view && (
+        <div className="flex shrink-0 items-center gap-2 border-b border-border/60 bg-[var(--status-info-background)] px-3 py-2">
+          <Icon name="loader-4" className="size-4 shrink-0 animate-spin text-[var(--status-info)]" />
+          <span className="typography-meta text-foreground">
+            {entry.stage === 'collecting'
+              ? t('walkthrough.stage.collecting')
+              : entry.stage === 'assembling'
+                ? t('walkthrough.stage.assembling')
+                : t('walkthrough.stage.asking')}
+          </span>
+        </div>
+      )}
+
+      {/* Switching the model or the language is a request for a walkthrough
+          that may not exist yet. Falling back to the last one is better than an
+          empty panel, but only if the panel says so — otherwise the picker
+          claims Ukrainian over English prose. */}
+      {(languageMissing || modelMissing) && (
+        <div className="flex shrink-0 items-center gap-2 border-b border-border/60 bg-[var(--status-info-background)] px-3 py-2">
+          <Icon name="information" className="size-4 shrink-0 text-[var(--status-info)]" />
+          <span className="typography-meta text-foreground">
+            {languageMissing && modelMissing
+              ? t('walkthrough.missing.languageAndModel')
+              : languageMissing
+                ? t('walkthrough.missing.language', {
+                  requested: label(activeLanguage),
+                  shown: label(shownLocale as Locale),
+                })
+                : t('walkthrough.missing.model', { model: activeModelId })}
+          </span>
+          <Button
+            type="button"
+            variant="ghost"
+            size="xs"
+            className="ml-auto"
+            // Not forced: if an entry for this exact request existed the banner
+            // would not be here, and a forced run would refuse the cache it may
+            // find on the way.
+            onClick={() => handleGenerate(false)}
+          >
+            {t('walkthrough.action.generate')}
+          </Button>
+        </div>
+      )}
+
+      {view?.isStale && entry.status !== 'generating' && (
+        <div className="flex shrink-0 items-center gap-2 border-b border-border/60 bg-status-warning/10 px-3 py-2">
+          <Icon name="error-warning" className="size-4 shrink-0 text-status-warning" />
+          <span className="typography-meta text-foreground">
+            {t('walkthrough.stale.banner', { count: view.staleStopCount })}
+          </span>
+          <Button
+            type="button"
+            variant="ghost"
+            size="xs"
+            className="ml-auto"
+            // Clicking this again mid-flight would abort the running generation
+            // and start another — paying for the same answer twice.
+            disabled={isGeneratingEntry}
+            onClick={() => handleGenerate(true)}
+          >
+            {t('walkthrough.action.regenerate')}
+          </Button>
+        </div>
+      )}
+
+      {entry.error && !blockedReason && (
+        <div className="flex shrink-0 items-start gap-2 border-b border-border/60 bg-status-error/10 px-3 py-2">
+          <Icon name="error-warning" className="mt-0.5 size-4 shrink-0 text-status-error" />
+          {/* Provider errors arrive as raw JSON bodies. Show a readable amount
+              and keep the rest reachable rather than filling the panel. */}
+          <span className="typography-meta line-clamp-2 text-foreground" title={entry.error.message}>
+            {entry.error.message}
+          </span>
+        </div>
+      )}
+
+      <div className={cn('flex min-h-0 flex-1', showToc ? 'flex-row' : 'flex-col')}>
+        {blockedReason ? (
+          <WalkthroughBlocker
+            reason={blockedReason}
+            model={blockedModel}
+            requiredChars={blockedRequiredChars}
+            availableChars={blockedAvailableChars}
+            onRetry={() => void load(directory, source)}
+          />
+        ) : showStages ? (
+          <div className="flex flex-1 flex-col items-center justify-center gap-3 p-8">
+            <WalkthroughStages progress={stageProgress} />
+          </div>
+        ) : view ? (
+          <>
+            {showToc && (
+              <>
+                <WalkthroughToc
+                  view={view}
+                  activeStopId={activeStopId}
+                  visitedStopIds={visitedStopIds}
+                  onSelectStop={handleSelectStop}
+                  width={tocWidth}
+                />
+                <div
+                  role="separator"
+                  aria-orientation="vertical"
+                  aria-label={t('walkthrough.toc.resize')}
+                  tabIndex={0}
+                  onPointerDown={handleTocResizeStart}
+                  onKeyDown={handleTocResizeKey}
+                  className={cn(
+                    'group relative w-1 shrink-0 cursor-col-resize',
+                    'before:absolute before:inset-y-0 before:-left-1 before:-right-1 before:content-[\'\']',
+                    'hover:bg-interactive-selection focus-visible:bg-interactive-selection focus-visible:outline-none',
+                    draggingToc && 'bg-interactive-selection'
+                  )}
+                />
+              </>
+            )}
+            <WalkthroughStream
+              view={view}
+              activeStopId={activeStopId}
+              scrollToStopId={scrollToStopId}
+              onActiveStopChange={handleActiveStopChange}
+              onScrollHandled={() => setScrollToStopId(null)}
+              renderSideBySide={renderSideBySide}
+              wrapLines={wrapLines}
+            />
+          </>
+        ) : (
+          <div className="flex flex-1 flex-col items-center justify-center gap-3 p-8 text-center">
+            {entry.status === 'loading' ? (
+              <Icon name="loader-4" className="size-6 animate-spin text-muted-foreground" />
+            ) : (
+              <>
+                <Icon name="route" className="size-6 text-muted-foreground" />
+                <h3 className="typography-ui-label font-semibold text-foreground">
+                  {t('walkthrough.empty.title')}
+                </h3>
+                <p className="typography-meta max-w-md text-muted-foreground">
+                  {t('walkthrough.empty.description')}
+                </p>
+              </>
+            )}
+          </div>
+        )}
+      </div>
+    </div>
+  );
+};

packages/ui/src/components/views/walkthrough/stopElementId.ts

@@ -0,0 +1,2 @@
+/** DOM id for a stop section, shared by the stream and its scroll callers. */
+export const stopElementId = (stopId: string): string => `walkthrough-stop-${stopId}`;

packages/ui/src/components/views/walkthrough/useWalkthroughStageProgress.test.ts

@@ -0,0 +1,40 @@
+import { describe, expect, test } from 'bun:test';
+import { WALKTHROUGH_STAGE_ORDER, __testing } from './useWalkthroughStageProgress';
+
+const { indexOfStage, nextIndex } = __testing;
+
+// The pacing itself is a React effect, but the two decisions it rests on are
+// plain functions and are where the mistakes would live.
+describe('stage ordering', () => {
+  test('maps every server stage onto a visible step', () => {
+    expect(indexOfStage('collecting')).toBe(0);
+    expect(indexOfStage('asking')).toBe(1);
+    expect(indexOfStage('assembling')).toBe(2);
+  });
+
+  test('folds the schema fallback into the same wait', () => {
+    // From out here it is still "waiting on the model"; the fallback is our
+    // plumbing and must not show up as its own step or as going backwards.
+    expect(indexOfStage('retrying')).toBe(indexOfStage('asking'));
+  });
+
+  test('treats an absent stage as not started', () => {
+    expect(indexOfStage(null)).toBe(-1);
+  });
+});
+
+describe('advancing', () => {
+  test('moves one step at a time so none is skipped', () => {
+    expect(nextIndex(-1, 2)).toBe(0);
+    expect(nextIndex(0, 2)).toBe(1);
+    expect(nextIndex(1, 2)).toBe(2);
+  });
+
+  test('stops at the target', () => {
+    expect(nextIndex(2, 2)).toBe(2);
+  });
+
+  test('completion goes one past the last step so everything reads as done', () => {
+    expect(nextIndex(2, WALKTHROUGH_STAGE_ORDER.length)).toBe(WALKTHROUGH_STAGE_ORDER.length);
+  });
+});

packages/ui/src/components/views/walkthrough/useWalkthroughStageProgress.ts

@@ -0,0 +1,92 @@
+import { useEffect, useRef, useState } from 'react';
+import type { WalkthroughStage } from '@/lib/walkthrough/types';
+
+/**
+ * Paces the stage display so every step is actually seen.
+ *
+ * Assembling the walkthrough takes milliseconds, so on the real timeline it
+ * flickers past between "waiting on the model" and the finished result — the
+ * user is told about a step they never observe, which is worse than not
+ * naming it. Each step is therefore held for a floor before the next one is
+ * revealed, including the final all-done state.
+ *
+ * This delays the result by well under a second at the end of a wait measured
+ * in minutes, and buys a legible finish in exchange.
+ */
+
+const ORDER: WalkthroughStage[] = ['collecting', 'asking', 'assembling'];
+const MIN_STEP_MS = 450;
+
+/** `retrying` is the same wait from the user's side: still waiting on the model. */
+const indexOfStage = (stage: WalkthroughStage | null): number => {
+  if (stage === 'retrying') return ORDER.indexOf('asking');
+  return stage ? ORDER.indexOf(stage) : -1;
+};
+
+/** One step at a time, so a fast stage is still shown rather than skipped. */
+const nextIndex = (current: number, target: number): number => Math.min(current + 1, target);
+
+export interface WalkthroughStageProgress {
+  /** Steps to render as finished. */
+  completedCount: number;
+  /** Step to render as running, or `null` when everything is done. */
+  activeIndex: number | null;
+  /** True while the display still owes the user time after the work finished. */
+  holding: boolean;
+}
+
+export const useWalkthroughStageProgress = (
+  stage: WalkthroughStage | null,
+  active: boolean
+): WalkthroughStageProgress => {
+  // `ORDER.length` means "all done"; -1 means nothing started.
+  const [shownIndex, setShownIndex] = useState(-1);
+  const shownAtRef = useRef(0);
+
+  const target = active ? Math.max(indexOfStage(stage), 0) : (shownIndex < 0 ? -1 : ORDER.length);
+
+  useEffect(() => {
+    if (target <= shownIndex) {
+      // Work restarted: fall back to the earlier step immediately rather than
+      // pretending the later one is still running.
+      if (target < shownIndex && active) {
+        setShownIndex(target);
+        shownAtRef.current = Date.now();
+      }
+      return;
+    }
+
+    const elapsed = Date.now() - shownAtRef.current;
+    const advance = () => {
+      shownAtRef.current = Date.now();
+      setShownIndex((current) => nextIndex(current, target));
+    };
+
+    if (shownIndex < 0 || elapsed >= MIN_STEP_MS) {
+      advance();
+      return;
+    }
+
+    const timer = setTimeout(advance, MIN_STEP_MS - elapsed);
+    return () => clearTimeout(timer);
+  }, [active, shownIndex, target]);
+
+  // A fresh run resets the display so the next generation starts from the top.
+  useEffect(() => {
+    if (active || shownIndex < ORDER.length) return;
+    const timer = setTimeout(() => setShownIndex(-1), MIN_STEP_MS);
+    return () => clearTimeout(timer);
+  }, [active, shownIndex]);
+
+  const done = shownIndex >= ORDER.length;
+
+  return {
+    completedCount: Math.max(0, Math.min(shownIndex, ORDER.length)),
+    activeIndex: done || shownIndex < 0 ? null : shownIndex,
+    holding: !active && shownIndex >= 0,
+  };
+};
+
+export const WALKTHROUGH_STAGE_ORDER = ORDER;
+
+export const __testing = { indexOfStage, nextIndex };

packages/ui/src/components/views/walkthrough/walkthroughAction.ts

@@ -0,0 +1,14 @@
+/**
+ * Shared chrome for every "open / generate the AI walkthrough" action.
+ *
+ * The walkthrough is informational rather than a primary or destructive act, so
+ * it carries the info status tint instead of competing with the primary button
+ * next to it (Review in the diff toolbar, Merge in the pull request header).
+ * Keeping it in one constant is what stops the three entry points from drifting
+ * apart.
+ *
+ * No sparkle iconography: "this is AI" is not what the button does, and the
+ * cliché tells the user nothing about the outcome.
+ */
+export const WALKTHROUGH_ACTION_CLASS =
+  'border-[var(--status-info-border)] bg-[var(--status-info-background)] text-[var(--status-info)] hover:bg-[var(--status-info-background)] hover:text-[var(--status-info)]';