feat(editor): Markdown 预览内嵌 HTML 安全渲染 + 目录大纲（TOC）

宿主 MarkdownText 出于聊天安全把 raw HTML 按字面文本渲染，预览 GitHub
风格 README（徽章墙 div、details 折叠块内嵌 markdown、表格单元格内联
标签、video/picture）时全是源码文本。本次在不动渲染器的前提下：

- markdown-html.ts（纯函数）：fence 感知切分器把文档切成 markdown/html
  段（CommonMark type-6 块级标签名单 + 注释段 + 空行终止）；段内标签
  tokenizer 归约 open/close/html parts；全文档引用定义收集（每段追加
  保持 [text][id] 跨段语义）
- MarkdownHtml.tsx：DOMPurify 白名单消毒（显式禁 script/iframe/form
  等；a 强制 _blank+noopener；本地媒体 src 经 /sidebar/file 重写）；
  MarkdownDocument 帧栈状态机让 <details> 跨段嵌套内部 markdown；
  MarkdownSegment 内联替换（MutationObserver 幂等 pass，把表格单元格
  等处标签文本消毒还原为元素，纯散文不误伤）
- md-toc.tsx：零高度 sticky 浮动目录按钮（≥3 标题）+ 弹出大纲，跳转
  平滑滚动 + 自动展开折叠 details + 高亮闪现。关键修复：子组件读父
  ref 在 React layout 阶段恒为 null（子先于父），改为经自身 bar ref
  的 parentElement 定位容器（jsdom 单测传预填 ref 掩盖了该 bug，仅
  真实挂载 e2e 抓到）
- 纯 markdown 文档走原单次解析路径零变化（现有 mermaid e2e 守卫一字
  不动）；新增 readme-style.md 种子 + 探针（消毒渲染/嵌套/内联/TOC
  全链路）；19 语言词典新增 toc 键；dompurify 提升为直接依赖（与
  mermaid 传递依赖去重单版本）

设计文档 docs/plans/2026-08-24-markdown-html-toc-design.md

src/client/MarkdownHtml.tsx

@@ -0,0 +1,295 @@
+/**
+ * The markdown preview's raw-HTML renderer. `markdown-html.ts` lifts HTML
+ * runs out of the markdown stream; this module renders them as sanitized DOM
+ * alongside the markdown runs (which keep flowing through the shared
+ * `MarkdownText`), nests markdown into unclosed block elements the way
+ * GitHub's linear HTML output does (`<details>` … fence … `</details>`), and
+ * runs an inline pass that turns literal tag text inside rendered markdown
+ * (table cells with `<br/>`, `<sub>`, `<img>`) back into elements.
+ *
+ * Security posture: every HTML string (block leaves, inline text, wrapper
+ * open-tag attributes) goes through DOMPurify with an explicit denylist on
+ * top of its defaults (no script/style/iframe/forms), anchors are forced to
+ * open in a new tab with noopener, and local media `src` attributes are
+ * rewritten through the session-scoped `/sidebar/file` media route — the same
+ * trust fence the markdown image rewriter (`markdown-images.ts`) uses.
+ */
+import { useLayoutEffect, useMemo, useRef } from 'react'
+import { createElement, type ReactNode } from 'react'
+import DOMPurify from 'dompurify'
+import { MarkdownText } from '@deepseek-ai/dsh-client-ui-primitives'
+import type { ComponentType } from 'react'
+import { lazyChunkComponent } from './lazy-chunk.tsx'
+import { resolveLocalMediaDest } from './markdown-images.ts'
+import {
+  analyzeHtmlSegment,
+  type AnalyzedMarkdownHtml,
+} from './markdown-html.ts'
+import { splitMermaidBlocks, type MermaidMarkdownProps } from './mermaid-blocks.ts'
+import type { SessionScope } from './api.ts'
+import css from './sidebar.module.css'
+
+/** The chunk-resident markdown renderer (mermaid lazy chunk), shared with the
+ *  legacy no-HTML preview path in TextEditor. */
+export const LazyMermaidMarkdown = lazyChunkComponent<MermaidMarkdownProps>(
+  'mermaid',
+  (mod) => mod.MermaidMarkdown as ComponentType<MermaidMarkdownProps> | undefined,
+)
+
+/** Everything the sanitizers need to resolve local media + scope the route. */
+export interface MarkdownHtmlMedia {
+  scope: SessionScope
+  path: string
+  origin: string
+}
+
+/** Tag-like text in a rendered text node — the inline pass gate. */
+const TAGLIKE_TEXT_RE = /<\/?[a-zA-Z][a-zA-Z0-9-]*[\s/>]/
+
+/** Explicit denylist on top of DOMPurify's defaults: no active content, no
+ *  form chrome, no document-level elements inside a preview. */
+const PURIFY_FORBID_TAGS = [
+  'script', 'style', 'iframe', 'object', 'embed', 'form', 'input', 'button',
+  'select', 'textarea', 'meta', 'link', 'base', 'frame', 'frameset', 'applet',
+]
+const PURIFY_FORBID_ATTR = ['srcdoc', 'formaction']
+
+/**
+ * Post-sanitize hardening on a detached element tree: anchors open in a new
+ * tab (never navigate the GUI), and local media sources go through the media
+ * route so they render instead of being dropped by protocol allowlists.
+ */
+function postProcessSanitized(root: Element, media: MarkdownHtmlMedia): void {
+  for (const anchor of root.querySelectorAll('a[href]')) {
+    anchor.setAttribute('target', '_blank')
+    anchor.setAttribute('rel', 'noopener noreferrer')
+  }
+  for (const element of root.querySelectorAll('img, video, audio, source')) {
+    const src = element.getAttribute('src')
+    if (src === null) continue
+    element.setAttribute('src', resolveLocalMediaDest(src, media.scope, media.path, media.origin))
+  }
+}
+
+/** Sanitize one balanced HTML span into markup for dangerouslySetInnerHTML. */
+function sanitizeHtmlBlock(source: string, media: MarkdownHtmlMedia): string {
+  const holder = document.createElement('div')
+  holder.innerHTML = DOMPurify.sanitize(source, {
+    FORBID_TAGS: PURIFY_FORBID_TAGS,
+    FORBID_ATTR: PURIFY_FORBID_ATTR,
+  })
+  postProcessSanitized(holder, media)
+  return holder.innerHTML
+}
+
+/**
+ * Sanitize literal tag text from a rendered markdown text node. Returns null
+ * when nothing real survived (pure prose like `a < b` — the DOMPurify output
+ * has no element children), so the caller leaves the text node untouched.
+ */
+function sanitizeInlineHtml(text: string, media: MarkdownHtmlMedia): string | null {
+  const holder = document.createElement('span')
+  holder.innerHTML = DOMPurify.sanitize(text, {
+    FORBID_TAGS: PURIFY_FORBID_TAGS,
+    FORBID_ATTR: PURIFY_FORBID_ATTR,
+  })
+  if (holder.firstElementChild === null) return null
+  postProcessSanitized(holder, media)
+  return holder.innerHTML
+}
+
+/**
+ * Sanitize a wrapper open tag (`<details open>`) into React props. Returns
+ * null when DOMPurify dropped the whole tag (denied element) — the renderer
+ * then treats the wrapper as transparent. `class`/`for` map to their React
+ * names; `style` is dropped (React needs an object; wrappers with inline
+ * styles are vanishingly rare and not worth a CSS parser).
+ */
+function sanitizeTagProps(tag: string, attrs: string): Record<string, string> | null {
+  const probe = DOMPurify.sanitize(`<${tag}${attrs}></${tag}>`, {
+    FORBID_TAGS: PURIFY_FORBID_TAGS,
+    FORBID_ATTR: PURIFY_FORBID_ATTR,
+  })
+  const holder = document.createElement('div')
+  holder.innerHTML = probe
+  const element = holder.firstElementChild
+  if (element === null || element.tagName.toLowerCase() !== tag) return null
+  const props: Record<string, string> = {}
+  for (const attr of element.attributes) {
+    if (/^on/i.test(attr.name) || !/^[a-zA-Z][a-zA-Z0-9:._-]*$/.test(attr.name)) continue
+    if (attr.name === 'style') continue
+    props[attr.name === 'class' ? 'className' : attr.name === 'for' ? 'htmlFor' : attr.name] = attr.value
+  }
+  return props
+}
+
+/**
+ * The inline pass: walk the rendered markdown's text nodes and swap any that
+ * contain tag-like text for a sanitized `<span data-html-inline>`. Rendered
+ * code (inline `code`, `pre`, the host `.md-code-block`, mermaid mounts, and
+ * spans this pass already produced) is skipped. The same commit-then-operate
+ * pattern the mermaid swap uses: React keeps owning the host tree, only leaf
+ * text nodes are replaced, and a text change re-renders the subtree fresh.
+ */
+function runInlineHtmlPass(container: HTMLElement, media: MarkdownHtmlMedia): void {
+  const walker = document.createTreeWalker(container, NodeFilter.SHOW_TEXT, {
+    acceptNode: (node) => {
+      const parent = (node as Text).parentElement
+      if (parent === null) return NodeFilter.FILTER_REJECT
+      if (parent.closest('code, pre, .md-code-block, [data-mermaid-processed], [data-html-inline]')) {
+        return NodeFilter.FILTER_REJECT
+      }
+      return TAGLIKE_TEXT_RE.test((node as Text).data)
+        ? NodeFilter.FILTER_ACCEPT
+        : NodeFilter.FILTER_REJECT
+    },
+  })
+  const targets: Text[] = []
+  for (let node = walker.nextNode(); node !== null; node = walker.nextNode()) targets.push(node as Text)
+  for (const node of targets) {
+    const html = sanitizeInlineHtml(node.data, media)
+    if (html === null) continue
+    const span = document.createElement('span')
+    span.setAttribute('data-html-inline', '')
+    span.innerHTML = html
+    node.replaceWith(span)
+  }
+}
+
+interface MarkdownSegmentProps {
+  text: string
+  hasMermaid: boolean
+  media: MarkdownHtmlMedia
+  codeLabels: { copyLabel: string; copiedLabel: string }
+}
+
+/**
+ * One markdown run of a split document: the shared MarkdownText pass (or the
+ * mermaid chunk renderer when the run contains a mermaid fence), plus the
+ * inline HTML pass. The pass runs after every text change and is re-armed by
+ * a MutationObserver so it also catches content that appears late (the lazy
+ * mermaid chunk mounting, shiki highlighting settling) — it is idempotent and
+ * skips its own output, so mutation feedback settles after one extra pass.
+ */
+function MarkdownSegment({ text, hasMermaid, media, codeLabels }: MarkdownSegmentProps): ReactNode {
+  const containerRef = useRef<HTMLDivElement>(null)
+  useLayoutEffect(() => {
+    const container = containerRef.current
+    if (container === null) return
+    runInlineHtmlPass(container, media)
+    let scheduled = false
+    const observer = new MutationObserver(() => {
+      if (scheduled) return
+      scheduled = true
+      queueMicrotask(() => {
+        scheduled = false
+        runInlineHtmlPass(container, media)
+      })
+    })
+    observer.observe(container, { childList: true, subtree: true })
+    return () => { observer.disconnect() }
+  }, [text, media])
+  return (
+    <div ref={containerRef}>
+      {hasMermaid
+        ? <LazyMermaidMarkdown text={text} codeLabels={codeLabels} />
+        : <MarkdownText text={text} codeLabels={codeLabels} />}
+    </div>
+  )
+}
+
+/** A sanitized, balanced HTML span rendered as its own block. */
+function HtmlLeaf({ html }: { html: string }): ReactNode {
+  return (
+    <div className={css.editorHtmlBlock} data-dsh-html-segment dangerouslySetInnerHTML={{ __html: html }} />
+  )
+}
+
+/** One fully-prepared HTML run: sanitized leaves + wrapper opens/closes. */
+type PreparedHtmlPart =
+  | { kind: 'html'; html: string }
+  | { kind: 'open'; tag: string; props: Record<string, string> | null }
+  | { kind: 'close' }
+
+type PreparedSegment =
+  | { kind: 'markdown'; text: string; hasMermaid: boolean }
+  | { kind: 'html'; parts: PreparedHtmlPart[] }
+
+interface MarkdownDocumentProps {
+  info: AnalyzedMarkdownHtml
+  media: MarkdownHtmlMedia
+  codeLabels: { copyLabel: string; copiedLabel: string }
+}
+
+/**
+ * The split-document renderer: markdown runs render through MarkdownSegment,
+ * HTML runs render as sanitized leaves, and unclosed block elements lower the
+ * following runs into themselves until their close part pops the frame (the
+ * renderer's frame stack persists across segments). Stray closes at the top
+ * level render nothing (the sanitizer/parser would drop them anyway), and
+ * frames still open at the end of the document are closed like a browser
+ * parser would. Sanitization runs once per prepared change, in a memo.
+ */
+export function MarkdownDocument({ info, media, codeLabels }: MarkdownDocumentProps): ReactNode {
+  const prepared = useMemo<PreparedSegment[]>(() => info.segments.map((segment): PreparedSegment => {
+    if (segment.kind === 'markdown') {
+      const defs = info.referenceDefinitions
+      const text = defs === '' ? segment.text : `${segment.text}\n\n${defs}`
+      return {
+        kind: 'markdown',
+        text,
+        hasMermaid: splitMermaidBlocks(text).some((block) => block.kind === 'mermaid'),
+      }
+    }
+    return {
+      kind: 'html',
+      parts: analyzeHtmlSegment(segment.text).parts.map((part): PreparedHtmlPart => {
+        if (part.kind === 'html') return { kind: 'html', html: sanitizeHtmlBlock(part.html, media) }
+        if (part.kind === 'open') return { kind: 'open', tag: part.tag, props: sanitizeTagProps(part.tag, part.attrs) }
+        return { kind: 'close' }
+      }),
+    }
+  // `media` is a memoized object in the host (TextEditor); identity tracks
+  // scope/path/origin changes so sanitization re-runs exactly when needed.
+  }), [info, media])
+
+  const nodes: ReactNode[] = []
+  const frames: { tag: string; props: Record<string, string> | null; children: ReactNode[] }[] = []
+  const emit = (node: ReactNode): void => {
+    const frame = frames[frames.length - 1]
+    if (frame !== undefined) frame.children.push(node)
+    else nodes.push(node)
+  }
+  let key = 0
+  for (const segment of prepared) {
+    if (segment.kind === 'markdown') {
+      emit(<MarkdownSegment key={`md-${key += 1}`} text={segment.text} hasMermaid={segment.hasMermaid} media={media} codeLabels={codeLabels} />)
+      continue
+    }
+    for (const part of segment.parts) {
+      if (part.kind === 'html') {
+        if (part.html.trim() === '') continue
+        emit(<HtmlLeaf key={`html-${key += 1}`} html={part.html} />)
+      } else if (part.kind === 'open') {
+        frames.push({ tag: part.tag, props: part.props, children: [] })
+      } else {
+        const frame = frames.pop()
+        if (frame === undefined) continue
+        if (frame.props === null) {
+          for (const child of frame.children) emit(child)
+        } else {
+          emit(createElement(frame.tag, { ...frame.props, key: `wrap-${key += 1}` }, ...frame.children))
+        }
+      }
+    }
+  }
+  while (frames.length > 0) {
+    const frame = frames.pop()!
+    if (frame.props === null) {
+      for (const child of frame.children) emit(child)
+    } else {
+      emit(createElement(frame.tag, { ...frame.props, key: `wrap-${key += 1}` }, ...frame.children))
+    }
+  }
+  return <>{nodes}</>
+}

src/client/TextEditor.tsx

@@ -14,7 +14,6 @@
  * renders the controls instead.
  */
 import { useEffect, useMemo, useRef, useState } from 'react'
-import type { ComponentType } from 'react'
 import { createPortal } from 'react-dom'
 import clsx from 'clsx'
 import { EditorState } from '@codemirror/state'
@@ -30,7 +29,10 @@ import { SandboxStatusBar } from './SandboxStatusBar.tsx'
 import { appendToDraft } from './conversation-draft.ts'
 import { buildSelectionInsert, linesOfSelection } from './selection-payload.ts'
 import { lazyChunkComponent } from './lazy-chunk.tsx'
-import { splitMermaidBlocks, type MermaidMarkdownProps } from './mermaid-blocks.ts'
+import { analyzeMarkdownHtml } from './markdown-html.ts'
+import { LazyMermaidMarkdown, MarkdownDocument, type MarkdownHtmlMedia } from './MarkdownHtml.tsx'
+import { MdToc } from './md-toc.tsx'
+import { splitMermaidBlocks } from './mermaid-blocks.ts'
 import { t } from './locales.ts'
 import type { EditorToolbarState, FileViewerProps } from './service.ts'
 import css from './sidebar.module.css'
@@ -45,16 +47,6 @@ interface SelectionPopup {
   top: number
 }
 
-/**
- * The chunk-resident markdown preview renderer (mermaid lazy chunk): one
- * MarkdownText pass over the whole source, with rendered mermaid fences
- * swapped for diagrams. Module-level `pick` keeps the load effect stable.
- */
-const LazyMermaidMarkdown = lazyChunkComponent<MermaidMarkdownProps>(
-  'mermaid',
-  (mod) => mod.MermaidMarkdown as ComponentType<MermaidMarkdownProps> | undefined,
-)
-
 /**
  * The sandbox tokens of the HTML preview iframe. NO allow-same-origin (the
  * preview must stay in an opaque origin — with the route's own origin it
@@ -266,9 +258,28 @@ export function TextEditor(props: FileViewerProps) {
     () => (markdown && mode === 'preview' ? splitMermaidBlocks(mdText) : []),
     [markdown, mode, mdText],
   )
+  /** Raw-HTML analysis (block runs lifted out + inline gate). Non-null only
+   *  for documents that actually contain HTML — plain markdown keeps the
+   *  legacy single-pass render path below, byte-for-byte. */
+  const htmlInfo = useMemo(
+    () => (markdown && mode === 'preview' ? analyzeMarkdownHtml(mdText) : null),
+    [markdown, mode, mdText],
+  )
   const hasMermaid = useMemo(
-    () => mdBlocks.some(block => block.kind === 'mermaid'),
-    [mdBlocks],
+    () => htmlInfo !== null
+      ? htmlInfo.segments.some((segment) => segment.kind === 'markdown'
+        && splitMermaidBlocks(segment.text).some((block) => block.kind === 'mermaid'))
+      : mdBlocks.some((block) => block.kind === 'mermaid'),
+    [htmlInfo, mdBlocks],
+  )
+  /** The media context for the split renderer (local-src rewriting inside
+   *  sanitized HTML). Memoized on primitives: MarkdownDocument sanitizes per
+   *  `media` identity, so a fresh object per render would re-sanitize every
+   *  keystroke. */
+  const htmlMedia = useMemo<MarkdownHtmlMedia>(
+    () => ({ scope, path, origin: window.location.origin }),
+    // eslint-disable-next-line react-hooks/exhaustive-deps
+    [scope.sessionId, scope.cwd, path],
   )
   const codeLabels = { copyLabel: t('copy'), copiedLabel: t('copied') }
 
@@ -395,13 +406,23 @@ export function TextEditor(props: FileViewerProps) {
               dictionary: the DSH MarkdownText/CodeBlock are cordis-free and
               fall back to hardcoded Chinese otherwise (same pattern as the
               chat's AssistantMarkdown). Render-time t() keeps them following
-              the active locale on live switches. Mermaid fences hand the
-              whole document to the mermaid lazy chunk (single markdown
-              parse; cross-fence references/footnotes stay intact); files
-              without one render exactly as before. */}
-          {hasMermaid
-            ? <LazyMermaidMarkdown text={previewText} codeLabels={codeLabels} />
-            : <MarkdownText text={previewText} codeLabels={codeLabels} />}
+              the active locale on live switches. Plain markdown (no HTML)
+              renders exactly as before — one MarkdownText pass for the whole
+              document, or the mermaid lazy chunk (single markdown parse;
+              cross-fence references/footnotes stay intact) when a mermaid
+              fence exists. Documents containing HTML (block runs or inline
+              tags) render through the split document renderer: markdown runs
+              keep the MarkdownText/mermaid path while raw-HTML runs render
+              as sanitized DOM (see markdown-html.tsx). */}
+          {/* The outline button rides on top of the preview scroll container
+              (sticky, zero-height — first child so it pins from the very
+              top) once the document has enough headings. */}
+          <MdToc />
+          {htmlInfo !== null
+            ? <MarkdownDocument info={htmlInfo} media={htmlMedia} codeLabels={codeLabels} />
+            : hasMermaid
+              ? <LazyMermaidMarkdown text={previewText} codeLabels={codeLabels} />
+              : <MarkdownText text={previewText} codeLabels={codeLabels} />}
         </div>
       )}
       {html && mode === 'preview' && (

src/client/locales-ar.ts

@@ -80,6 +80,7 @@ export const ar: Record<string, string> = {
   terminalDepsHint: 'شغّل الأمر التالي في طرفية أو cmd على جهاز DSH للإصلاح، ثم أعد المحاولة (يبقى node-pty متزامناً مع إصدار نواة DSH):',
   terminalDepsProfile: ' (الملف الشخصي المكتشف: {profile})',
   preview: 'معاينة',
+  toc: 'الفهرس',
   edit: 'تحرير',
   mermaidError: 'فشل رسم Mermaid',
   mermaidZoomIn: 'تكبير',

src/client/locales-de.ts

@@ -65,6 +65,7 @@ export const de: Record<string, string> = {
   terminalDepsHint: 'Führen Sie den folgenden Befehl in einem Terminal oder in cmd auf dem DSH-System aus, um dies zu beheben, und klicken Sie dann auf „Erneut versuchen“ (node-pty bleibt mit der DSH-Core-Version synchron):',
   terminalDepsProfile: ' (erkanntes Profil: {profile})',
   preview: 'Vorschau',
+  toc: 'Inhaltsverzeichnis',
   edit: 'Bearbeiten',
   mermaidError: 'Mermaid-Rendering fehlgeschlagen',
   mermaidZoomIn: 'Vergrößern',

src/client/locales-fr.ts

@@ -72,6 +72,7 @@ export const fr: Record<string, string> = {
   terminalDepsHint: 'Exécutez la commande suivante dans un terminal ou cmd de l’environnement DSH pour réparer, puis cliquez sur Réessayer (node-pty reste à la même version que le cœur DSH) :',
   terminalDepsProfile: ' (profil détecté : {profile})',
   preview: 'Aperçu',
+  toc: 'Sommaire',
   edit: 'Modifier',
   mermaidError: 'Échec du rendu Mermaid',
   mermaidZoomIn: 'Agrandir',

src/client/locales-hi.ts

@@ -79,6 +79,7 @@ export const hi: Record<string, string> = {
   terminalDepsHint: 'DSH मशीन पर एक टर्मिनल या cmd में नीचे दिया गया कमांड चलाएँ, फिर पुनः प्रयास करें (node-pty DSH कोर संस्करण के साथ सिंक रहता है):',
   terminalDepsProfile: ' (पहचाना गया प्रोफ़ाइल: {profile})',
   preview: 'पूर्वावलोकन',
+  toc: 'विषय-सूची',
   edit: 'संपादित करें',
   mermaidError: 'Mermaid रेंडर विफल',
   mermaidZoomIn: 'ज़ूम इन',

src/client/locales-id.ts

@@ -77,6 +77,7 @@ export const id: Record<string, string> = {
   terminalDepsHint: 'Jalankan perintah di bawah ini di terminal atau cmd pada mesin DSH untuk memperbaikinya, lalu coba lagi (node-pty tetap sinkron dengan versi inti DSH):',
   terminalDepsProfile: ' (profil terdeteksi: {profile})',
   preview: 'Pratinjau',
+  toc: 'Daftar Isi',
   edit: 'Edit',
   mermaidError: 'Render Mermaid gagal',
   mermaidZoomIn: 'Perbesar',

src/client/locales-it.ts

@@ -70,6 +70,7 @@ export const it: Record<string, string> = {
   terminalDepsHint: 'Esegua il comando seguente in un terminale o cmd sul computer DSH per ripristinarlo, poi riprovi (node-pty resta sincronizzato con la versione del core DSH):',
   terminalDepsProfile: ' (rilevato profilo: {profile})',
   preview: 'Anteprima',
+  toc: 'Indice',
   edit: 'Modifica',
   mermaidError: 'Rendering Mermaid non riuscito',
   mermaidZoomIn: 'Ingrandisci',

src/client/locales-ja.ts

@@ -79,6 +79,7 @@ export const ja: Record<string, string> = {
   terminalDepsHint: 'DSH 環境のターミナルまたは cmd で以下のコマンドを実行して修復し、再試行してください（node-pty は DSH コアと同じバージョンを維持）：',
   terminalDepsProfile: '（検出された profile：{profile}）',
   preview: 'プレビュー',
+  toc: '目次',
   edit: '編集',
   mermaidError: 'Mermaid レンダリング失敗',
   mermaidZoomIn: '拡大',

src/client/locales-ko.ts

@@ -71,6 +71,7 @@ export const ko: Record<string, string> = {
   terminalDepsHint: 'DSH가 설치된 환경의 터미널 또는 cmd에서 아래 명령을 실행하여 복구한 후 다시 시도를 클릭하세요(node-pty는 DSH 코어와 동일한 버전을 유지합니다):',
   terminalDepsProfile: ' (profile 감지됨: {profile})',
   preview: '미리보기',
+  toc: '목차',
   edit: '편집',
   mermaidError: 'Mermaid 렌더링 실패',
   mermaidZoomIn: '확대',

src/client/locales-nl.ts

@@ -77,6 +77,7 @@ export const nl: Record<string, string> = {
   terminalDepsHint: 'Voer het onderstaande commando uit in een terminal of cmd op de DSH-machine om het te herstellen en probeer het opnieuw (node-pty blijft in sync met de DSH-coreversie):',
   terminalDepsProfile: ' (gedetecteerde profile: {profile})',
   preview: 'Voorbeeld',
+  toc: 'Inhoudsopgave',
   edit: 'Bewerken',
   mermaidError: 'Mermaid-renderen mislukt',
   mermaidZoomIn: 'Inzoomen',

src/client/locales-pl.ts

@@ -81,6 +81,7 @@ export const pl: Record<string, string> = {
   terminalDepsHint: 'Uruchom poniższe polecenie w terminalu lub cmd na maszynie DSH, aby to naprawić, a następnie ponów (node-pty pozostaje w synchronizacji z wersją rdzenia DSH):',
   terminalDepsProfile: ' (wykryty profil: {profile})',
   preview: 'Podgląd',
+  toc: 'Spis treści',
   edit: 'Edytuj',
   mermaidError: 'Renderowanie Mermaid nie powiodło się',
   mermaidZoomIn: 'Powiększ',

src/client/locales-pt.ts

@@ -62,6 +62,7 @@ export const pt: Record<string, string> = {
   terminalDepsHint: 'Execute o comando abaixo em um terminal ou cmd na máquina do DSH para reparar e tente novamente (node-pty permanece em sincronia com a versão do núcleo do DSH):',
   terminalDepsProfile: ' (perfil detectado: {profile})',
   preview: 'Pré-visualizar',
+  toc: 'Sumário',
   edit: 'Editar',
   mermaidError: 'Falha ao renderizar o Mermaid',
   mermaidZoomIn: 'Ampliar',

src/client/locales-ru.ts

@@ -75,6 +75,7 @@ export const ru: Record<string, string> = {
   terminalDepsHint: 'Выполните приведённую ниже команду в терминале или cmd на машине DSH, затем нажмите «Повторить» (node-pty остаётся синхронизированным с версией ядра DSH):',
   terminalDepsProfile: ' (обнаружен profile: {profile})',
   preview: 'Предпросмотр',
+  toc: 'Оглавление',
   edit: 'Изменить',
   mermaidError: 'Сбой рендеринга Mermaid',
   mermaidZoomIn: 'Приблизить',

src/client/locales-sv.ts

@@ -62,6 +62,7 @@ export const sv: Record<string, string> = {
   terminalDepsHint: 'Kör kommandot nedan i en terminal eller cmd på DSH-maskinen för att reparera det, försök sedan igen (node-pty hålls synkad med DSH-kärnversionen):',
   terminalDepsProfile: ' (upptäckt profil: {profile})',
   preview: 'Förhandsgranska',
+  toc: 'Innehållsförteckning',
   edit: 'Redigera',
   mermaidError: 'Mermaid-rendering misslyckades',
   mermaidZoomIn: 'Zooma in',

src/client/locales-th.ts

@@ -79,6 +79,7 @@ export const th: Record<string, string> = {
   terminalDepsHint: 'เรียกใช้คำสั่งด้านล่างในเทอร์มินัลหรือ cmd บนเครื่อง DSH เพื่อซ่อมแซม แล้วกดลองอีกครั้ง (node-pty ต้องซิงค์กับเวอร์ชันหลักของ DSH):',
   terminalDepsProfile: ' (ตรวจพบ profile: {profile})',
   preview: 'พรีวิว',
+  toc: 'สารบัญ',
   edit: 'แก้ไข',
   mermaidError: 'เรนเดอร์ Mermaid ล้มเหลว',
   mermaidZoomIn: 'ซูมเข้า',

src/client/locales-tr.ts

@@ -79,6 +79,7 @@ export const tr: Record<string, string> = {
   terminalDepsHint: 'Onarmak için DSH makinesindeki bir terminalde veya cmd’de aşağıdaki komutu çalıştırın, sonra yeniden deneyin (node-pty, DSH çekirdek sürümüyle senkron kalır):',
   terminalDepsProfile: ' (algılanan profil: {profile})',
   preview: 'Önizleme',
+  toc: 'İçindekiler',
   edit: 'Düzenle',
   mermaidError: 'Mermaid oluşturma başarısız',
   mermaidZoomIn: 'Yakınlaştır',

src/client/locales-vi.ts

@@ -79,6 +79,7 @@ export const vi: Record<string, string> = {
   terminalDepsHint: 'Chạy lệnh sau trong terminal hoặc cmd trên máy DSH để sửa, rồi nhấn thử lại (node-pty đồng bộ phiên bản với lõi DSH):',
   terminalDepsProfile: ' (phát hiện profile: {profile})',
   preview: 'Xem trước',
+  toc: 'Mục lục',
   edit: 'Chỉnh sửa',
   mermaidError: 'Render Mermaid thất bại',
   mermaidZoomIn: 'Phóng to',

src/client/locales-zh-HK.ts

@@ -94,6 +94,7 @@ export const zhHK: Record<string, string> = {
   terminalDepsHint: '在 DSH 所在環境的終端或 cmd 中執行以下命令修復，然後點重試（node-pty 與 DSH 核心保持同一版本）：',
   terminalDepsProfile: '（偵測到 profile：{profile}）',
   preview: '預覽',
+  toc: '目錄',
   edit: '編輯',
   mermaidError: 'Mermaid 渲染失敗',
   mermaidZoomIn: '放大',

src/client/locales-zh-MO.ts

@@ -94,6 +94,7 @@ export const zhMO: Record<string, string> = {
   terminalDepsHint: '在 DSH 所在環境的終端或 cmd 中執行以下命令修復，然後點重試（node-pty 與 DSH 核心保持同一版本）：',
   terminalDepsProfile: '（偵測到 profile：{profile}）',
   preview: '預覽',
+  toc: '目錄',
   edit: '編輯',
   mermaidError: 'Mermaid 渲染失敗',
   mermaidZoomIn: '放大',

src/client/locales-zh-TW.ts

@@ -94,6 +94,7 @@ export const zhTW: Record<string, string> = {
   terminalDepsHint: '在 DSH 所在環境的終端或 cmd 中執行以下命令修復，然後點重試（node-pty 與 DSH 核心保持同一版本）：',
   terminalDepsProfile: '（偵測到 profile：{profile}）',
   preview: '預覽',
+  toc: '目錄',
   edit: '編輯',
   mermaidError: 'Mermaid 渲染失敗',
   mermaidZoomIn: '放大',

src/client/locales.ts

@@ -86,6 +86,7 @@ export const zh = {
   terminalDepsHint: '在 DSH 所在环境的终端或 cmd 中执行以下命令修复，然后点重试（node-pty 与 DSH 核心保持同一版本）：',
   terminalDepsProfile: '（检测到 profile：{profile}）',
   preview: '预览',
+  toc: '目录',
   edit: '编辑',
   mermaidError: 'Mermaid 渲染失败',
   mermaidZoomIn: '放大',
@@ -420,6 +421,7 @@ export const en: Record<keyof typeof zh, string> = {
   terminalDepsHint: 'Run the command below in a terminal or cmd on the DSH machine to repair it, then retry (node-pty stays in sync with the DSH core version):',
   terminalDepsProfile: ' (detected profile: {profile})',
   preview: 'Preview',
+  toc: 'Table of contents',
   edit: 'Edit',
   mermaidError: 'Mermaid render failed',
   mermaidZoomIn: 'Zoom in',

src/client/markdown-html.ts

@@ -0,0 +1,331 @@
+/**
+ * Raw-HTML block detection for the markdown preview. The shared `MarkdownText`
+ * renders raw HTML as literal text (a chat-security stance), so a GitHub-style
+ * README (`<div align="center">` badge walls, `<details>` collapsibles with
+ * markdown inside, table cells full of inline tags) previews as source soup.
+ * This module's pure splitter lifts those HTML runs OUT of the markdown stream
+ * before rendering: markdown runs keep flowing through `MarkdownText` (shiki /
+ * KaTeX / GFM intact, mermaid chunk path unchanged) while HTML runs render as
+ * sanitized DOM (see markdown-html.tsx).
+ *
+ * Splitting follows CommonMark's shape closely enough for real-world READMEs:
+ * a line outside code fences that starts with a block-level tag (type-6 list
+ * below) or `<!--` opens an HTML run that extends to the next blank line
+ * (comments end at the line containing `-->`). Inline-only tags (`<b>`, `<br>`,
+ * `<a>`…) never open a run — they stay in the markdown stream and are handled
+ * by the inline pass instead. Unclosed block tags (`<details>` … markdown …
+ * `</details>`) are surfaced by {@link analyzeHtmlSegment} as ordered parts so
+ * the renderer can nest the in-between markdown inside the open element, the
+ * way GitHub's linear HTML output nests.
+ */
+
+import { CLOSE_FENCE_RE, OPEN_FENCE_RE, fenceInfo } from './mermaid-blocks.ts'
+
+/** A run of raw HTML lines lifted out of the markdown stream. */
+export interface HtmlSegment {
+  kind: 'html'
+  text: string
+}
+
+/** A run of markdown source (may contain non-mermaid fences, inline HTML…). */
+export interface MarkdownHtmlSegment {
+  kind: 'markdown'
+  text: string
+}
+
+export type MdHtmlSegment = MarkdownHtmlSegment | HtmlSegment
+
+/** The doc-wide analysis the preview consumes (all pure, unit-tested here). */
+export interface AnalyzedMarkdownHtml {
+  /** The document split into markdown / html runs (empty input → []). */
+  segments: MdHtmlSegment[]
+  /** True when at least one html run was lifted out. */
+  hasBlockHtml: boolean
+  /** True when the source contains any tag-like text (block OR inline). */
+  hasInlineHtml: boolean
+  /** Every reference definition found in the markdown runs (`[label]: dest`
+   *  lines), joined — appended to each markdown run so `[text][id]` keeps
+   *  resolving across the lifted HTML runs (first-match wins makes the
+   *  appended copy inert inside runs that already define it). */
+  referenceDefinitions: string
+}
+
+/**
+ * CommonMark HTML-block type-6 tag names (block-level elements), lowercased.
+ * A line starting with one of these (open or close) outside a fence begins an
+ * HTML run. `<summary>` is CommonMark-inline but intentionally included: it is
+ * the idiomatic first child of a `<details>` run in GitHub-flavored READMEs.
+ */
+export const HTML_BLOCK_TAGS: ReadonlySet<string> = new Set([
+  'address', 'article', 'aside', 'base', 'basefont', 'blockquote', 'body',
+  'caption', 'center', 'col', 'colgroup', 'dd', 'details', 'dialog', 'dir',
+  'div', 'dl', 'dt', 'fieldset', 'figcaption', 'figure', 'footer', 'form',
+  'frame', 'frameset', 'h1', 'h2', 'h3', 'h4', 'h5', 'h6', 'head', 'header',
+  'hr', 'html', 'legend', 'li', 'link', 'main', 'menu', 'menuitem', 'nav',
+  'noframes', 'ol', 'optgroup', 'option', 'p', 'param', 'picture', 'pre',
+  'section', 'source', 'summary', 'table', 'tbody', 'td', 'tfoot', 'th',
+  'thead', 'title', 'tr', 'track', 'ul', 'video',
+])
+
+/** HTML void elements — never pushed on the balance stack. */
+const VOID_TAGS: ReadonlySet<string> = new Set([
+  'area', 'base', 'br', 'col', 'embed', 'hr', 'img', 'input', 'link', 'meta',
+  'param', 'source', 'track', 'wbr',
+])
+
+/** A block-tag line start: indent + `<` or `</` + tag name + space/`/`/`>`. */
+const HTML_BLOCK_START_RE = /^ {0,3}<\/?([a-zA-Z][a-zA-Z0-9-]*)[\s/>]/
+
+/** A comment-open line start (CommonMark type 2). */
+const COMMENT_START_RE = /^ {0,3}<!--/
+
+/** Tag-like text anywhere — the cheap gate for the inline pass. */
+const TAGLIKE_RE = /<\/?[a-zA-Z][a-zA-Z0-9-]*[\s/>]/
+
+/** One HTML tag token (open/close/void) in a lifted HTML run. */
+interface HtmlToken {
+  kind: 'open' | 'close' | 'void'
+  tag: string
+  /** Raw attribute source of an open tag (between the name and `>`/`/>`). */
+  attrs: string
+  start: number
+  end: number
+}
+
+/** A comment range within a run — tags inside comments are not tokens. */
+interface CommentRange {
+  start: number
+  end: number
+}
+
+/** A full tag match including its `>` (token regex; quotes guard `>` inside attrs). */
+const TAG_TOKEN_RE = /<(\/?)([a-zA-Z][a-zA-Z0-9-]*)((?:"[^"]*"|'[^']*'|[^>"'])*)>/g
+const COMMENT_RE = /<!--[\s\S]*?-->/g
+
+/**
+ * Tokenize a lifted HTML run into tags (comments are located first so tags
+ * inside them are skipped). Text between tokens is not tokenized — it stays
+ * part of the raw `html` spans the part analysis slices out.
+ */
+function tokenizeHtml(source: string): HtmlToken[] {
+  const comments: CommentRange[] = []
+  for (const match of source.matchAll(COMMENT_RE)) {
+    comments.push({ start: match.index, end: match.index + match[0].length })
+  }
+  const inComment = (index: number): boolean =>
+    comments.some((range) => index >= range.start && index < range.end)
+  const tokens: HtmlToken[] = []
+  for (const match of source.matchAll(TAG_TOKEN_RE)) {
+    if (inComment(match.index)) continue
+    const closing = match[1] === '/'
+    const tag = match[2]!.toLowerCase()
+    let attrs = match[3] ?? ''
+    // Self-closing syntax (`<div/>`) behaves as void regardless of the name.
+    const selfClosing = /\/\s*$/.test(attrs)
+    if (selfClosing) attrs = attrs.replace(/\/\s*$/, '')
+    tokens.push({
+      kind: closing ? 'close' : selfClosing || VOID_TAGS.has(tag) ? 'void' : 'open',
+      tag,
+      attrs,
+      start: match.index,
+      end: match.index + match[0].length,
+    })
+  }
+  return tokens
+}
+
+/** One structural piece of a lifted HTML run, in document order. */
+export type HtmlPart =
+  | { kind: 'html'; html: string }
+  | { kind: 'open'; tag: string; attrs: string }
+  | { kind: 'close'; tag: string }
+
+/** The run's structure relative to the surrounding document nesting. */
+export interface HtmlSegmentShape {
+  parts: HtmlPart[]
+}
+
+/**
+ * Reduce a lifted HTML run to ordered parts: balanced spans become `html`
+ * leaves, unclosed open tags become `open` (a wrapper the renderer lowers
+ * following markdown runs into), unmatched closes become `close` (pops one
+ * wrapper level). A mismatched close pops through the matching open — the
+ * HTML parser's implicit-close behavior. Runs with no structural tags reduce
+ * to a single `html` part.
+ */
+export function analyzeHtmlSegment(source: string): HtmlSegmentShape {
+  const tokens = tokenizeHtml(source)
+  const stack: { token: HtmlToken }[] = []
+  const unmatchedCloses: HtmlToken[] = []
+
+  for (let index = 0; index < tokens.length; index += 1) {
+    const token = tokens[index]!
+    if (token.kind === 'void') continue
+    if (token.kind === 'open') {
+      stack.push({ token })
+      continue
+    }
+    // Close: pop through the nearest matching open (implicit closes inside).
+    let matchAt = -1
+    for (let depth = stack.length - 1; depth >= 0; depth -= 1) {
+      if (stack[depth]!.token.tag === token.tag) { matchAt = depth; break }
+    }
+    if (matchAt === -1) {
+      unmatchedCloses.push(token)
+      continue
+    }
+    stack.length = matchAt
+  }
+
+  // Structural tokens in source order: unmatched closes + surviving opens.
+  const structural: Array<{ token: HtmlToken; kind: 'open' | 'close' }> = []
+  for (const token of unmatchedCloses) structural.push({ token, kind: 'close' })
+  for (const entry of stack) structural.push({ token: entry.token, kind: 'open' })
+  structural.sort((a, b) => a.token.start - b.token.start)
+
+  if (structural.length === 0) return { parts: [{ kind: 'html', html: source }] }
+
+  const parts: HtmlPart[] = []
+  let cursor = 0
+  for (const { token, kind } of structural) {
+    if (token.start > cursor) parts.push({ kind: 'html', html: source.slice(cursor, token.start) })
+    parts.push(kind === 'open'
+      ? { kind: 'open', tag: token.tag, attrs: token.attrs }
+      : { kind: 'close', tag: token.tag })
+    cursor = token.end
+  }
+  if (cursor < source.length) parts.push({ kind: 'html', html: source.slice(cursor) })
+  return { parts }
+}
+
+/**
+ * Split markdown source into markdown / html runs (fence-aware: an HTML-looking
+ * line inside any fenced code block is content, not a run start). Blank lines
+ * terminate HTML runs and are dropped between segments (they carry no markdown
+ * semantics the preview needs); everything else stays byte-identical.
+ */
+export function splitHtmlBlocks(text: string): MdHtmlSegment[] {
+  if (text === '') return []
+  const lines = text.split('\n')
+  const segments: MdHtmlSegment[] = []
+  let markdown: string[] = []
+  let html: string[] = []
+  /** Fence state: the char + length of the currently open fence, if any. */
+  let openFence: { char: string; length: number } | null = null
+  /** Comment state: an HTML comment run ends at the line containing `-->`. */
+  let inComment = false
+  /** True while accumulating a blank-line-terminated HTML run. */
+  let inHtmlRun = false
+
+  const flushMarkdown = (): void => {
+    // Separator blank lines around HTML runs carry no markdown semantics.
+    while (markdown.length > 0 && isBlank(markdown[markdown.length - 1] ?? '')) markdown.pop()
+    if (markdown.length === 0) return
+    segments.push({ kind: 'markdown', text: markdown.join('\n') })
+    markdown = []
+  }
+  const flushHtml = (): void => {
+    if (html.length === 0) return
+    segments.push({ kind: 'html', text: html.join('\n') })
+    html = []
+    inHtmlRun = false
+    inComment = false
+  }
+  const isBlank = (line: string): boolean => /^[ \t]*$/.test(line)
+
+  for (const line of lines) {
+    if (openFence !== null) {
+      const close = CLOSE_FENCE_RE.exec(line)
+      if (close !== null && close[1]!.charAt(0) === openFence.char && close[1]!.length >= openFence.length) {
+        openFence = null
+      }
+      markdown.push(line)
+      continue
+    }
+    const fenceMatch = OPEN_FENCE_RE.exec(line)
+    if (fenceMatch !== null) {
+      const fence = fenceMatch[1]!
+      const rest = line.slice(fenceMatch.index + fenceMatch[0].length)
+      const info = fenceInfo(rest, fence)
+      if (info !== null) {
+        openFence = { char: fence.charAt(0), length: fence.length }
+        markdown.push(line)
+        continue
+      }
+      // Not a valid fence (backtick info containing backticks): plain text.
+      markdown.push(line)
+      continue
+    }
+
+    if (inComment) {
+      html.push(line)
+      if (line.includes('-->')) flushHtml()
+      continue
+    }
+    if (inHtmlRun) {
+      if (isBlank(line)) {
+        flushHtml()
+        continue
+      }
+      html.push(line)
+      continue
+    }
+
+    if (COMMENT_START_RE.test(line)) {
+      flushMarkdown()
+      html.push(line)
+      inComment = true
+      if (line.includes('-->')) flushHtml()
+      continue
+    }
+    const htmlMatch = HTML_BLOCK_START_RE.exec(line)
+    const tag = htmlMatch?.[1]?.toLowerCase()
+    if (htmlMatch !== null && tag !== undefined && HTML_BLOCK_TAGS.has(tag)) {
+      flushMarkdown()
+      html.push(line)
+      inHtmlRun = true
+      continue
+    }
+    // Blank lines only survive inside a markdown run (paragraph separators);
+    // at a run boundary they are separators and are dropped.
+    if (isBlank(line) && markdown.length === 0) continue
+    markdown.push(line)
+  }
+  flushMarkdown()
+  flushHtml()
+  return segments
+}
+
+/** A reference definition line: `[label]: destination` (up to 3 spaces indent). */
+const REFERENCE_DEF_RE = /^ {0,3}\[((?:[^\][]|\[[^\]]*\])*)\]:\s*(?:<([^<>]*)>|(\S+))/
+
+/**
+ * Collect the reference definitions of every markdown run (HTML runs cannot
+ * define them), in document order, newline-joined for appending.
+ */
+export function collectReferenceDefinitions(segments: readonly MdHtmlSegment[]): string {
+  const defs: string[] = []
+  for (const segment of segments) {
+    if (segment.kind !== 'markdown') continue
+    for (const line of segment.text.split('\n')) {
+      if (REFERENCE_DEF_RE.test(line)) defs.push(line)
+    }
+  }
+  return defs.join('\n')
+}
+
+/**
+ * The whole-document gate + split the preview consumes. `hasInlineHtml` is a
+ * cheap source-level regex (code-fence content may false-positive; the inline
+ * pass skips rendered code blocks anyway, so a false positive only costs the
+ * enhanced render path, never a behavior change).
+ */
+export function analyzeMarkdownHtml(text: string): AnalyzedMarkdownHtml {
+  const segments = splitHtmlBlocks(text)
+  return {
+    segments,
+    hasBlockHtml: segments.some((segment) => segment.kind === 'html'),
+    hasInlineHtml: TAGLIKE_RE.test(text),
+    referenceDefinitions: collectReferenceDefinitions(segments),
+  }
+}

src/client/markdown-images.ts

@@ -65,28 +65,41 @@ function normalizeLocalPath(path: string): string {
  * so the core rewrite stays pure and unit-testable.
  * @returns The markdown with local image destinations rewritten in place.
  */
+/**
+ * Resolve one media destination against the session's media route: local
+ * (relative or absolute) paths become absolute `/sidebar/file` URLs (prefixed
+ * with the GUI's own origin so the shared MarkdownText http(s) allowlist
+ * accepts them), while remote URLs, `#`-anchors and empty destinations are
+ * returned untouched. Shared by the markdown image rewriter below and by the
+ * preview's raw-HTML sanitizer (`markdown-html.tsx`, which meets the same
+ * allowlist when rendering `<img src="./x.png">` inside HTML blocks).
+ */
+export function resolveLocalMediaDest(
+  dest: string,
+  scope: SessionScope,
+  filePath: string,
+  origin: string,
+): string {
+  const trimmed = dest.trim()
+  if (trimmed === '' || trimmed.startsWith('#')) return dest
+  if (isRemoteUrl(trimmed)) return dest
+  const slash = Math.max(filePath.lastIndexOf('/'), filePath.lastIndexOf('\\'))
+  const directory = slash === -1 ? '/' : filePath.slice(0, slash + 1)
+  const candidate = isAbsolutePath(trimmed) ? trimmed : directory + trimmed
+  // Mirrors api.ts fileUrl/mediaUrl for the /sidebar/file media route, made
+  // absolute so the shared MarkdownText http(s) allowlist accepts it.
+  const params = new URLSearchParams({ sessionId: scope.sessionId, path: normalizeLocalPath(candidate) })
+  if (scope.cwd !== undefined && scope.cwd !== '') params.set('cwd', scope.cwd)
+  return `${origin}/sidebar/file?${params.toString()}`
+}
+
 export function rewriteLocalImageUrls(
   text: string,
   scope: SessionScope,
   filePath: string,
   origin: string,
 ): string {
-  const slash = Math.max(filePath.lastIndexOf('/'), filePath.lastIndexOf('\\'))
-  const directory = slash === -1 ? '/' : filePath.slice(0, slash + 1)
-  const mediaUrl = (candidate: string): string => {
-    // Mirrors api.ts fileUrl/mediaUrl for the /sidebar/file media route, made
-    // absolute so the shared MarkdownText http(s) allowlist accepts it.
-    const params = new URLSearchParams({ sessionId: scope.sessionId, path: candidate })
-    if (scope.cwd !== undefined && scope.cwd !== '') params.set('cwd', scope.cwd)
-    return `${origin}/sidebar/file?${params.toString()}`
-  }
-  const resolve = (dest: string): string => {
-    const trimmed = dest.trim()
-    if (trimmed === '' || trimmed.startsWith('#')) return dest
-    if (isRemoteUrl(trimmed)) return dest
-    const candidate = isAbsolutePath(trimmed) ? trimmed : directory + trimmed
-    return mediaUrl(normalizeLocalPath(candidate))
-  }
+  const resolve = (dest: string): string => resolveLocalMediaDest(dest, scope, filePath, origin)
 
   // Mask fenced code blocks and inline code spans so image-looking text
   // inside documentation examples is never rewritten. The sentinel uses a

src/client/md-toc.tsx

@@ -0,0 +1,127 @@
+/**
+ * The markdown preview's table of contents: a sticky zero-height bar keeping
+ * a small "outline" button pinned at the top-right of the preview's scroll
+ * container, visible once the document has at least {@link TOC_MIN_HEADINGS}
+ * headings. The button opens a popover outline (h1–h6 collected from the
+ * rendered DOM — so headings inside HTML runs count too); clicking an entry
+ * expands any collapsed `<details>` ancestor, smooth-scrolls the heading into
+ * view and flashes it. The scan re-runs through a MutationObserver so late
+ * content (lazy mermaid chunk, shiki highlighting) is picked up.
+ *
+ * Mount contract: render as a DIRECT child of the scroll container it
+ * outlines. The container is discovered through the bar's own DOM position
+ * (`parentElement`), not a passed ref — React attaches a parent host
+ * element's ref only after its children's layout effects have run, so a
+ * ref-based container read here would see null at mount and never re-run.
+ * The bar itself renders unconditionally (zero height, pointer-events
+ * none), so it never affects the preview layout.
+ */
+import { useLayoutEffect, useRef, useState } from 'react'
+import type { ReactNode } from 'react'
+import { IconListPenOutline16 } from '@deepseek-ai/dsh-client-ui-primitives'
+import { t } from './locales.ts'
+import css from './sidebar.module.css'
+
+/** Fewer headings than this and the button stays hidden (no outline value). */
+export const TOC_MIN_HEADINGS = 3
+
+/** One collected outline entry; `el` is the live rendered heading element. */
+interface TocEntry {
+  level: number
+  text: string
+  el: HTMLElement
+}
+
+/** The signature used to skip no-op rescans (identity-safe setState guard). */
+function signatureOf(entries: readonly TocEntry[]): string {
+  return entries.map((entry) => `${entry.level}:${entry.text}`).join('\n')
+}
+
+export function MdToc(): ReactNode {
+  const barRef = useRef<HTMLDivElement>(null)
+  const [entries, setEntries] = useState<TocEntry[]>([])
+  const [open, setOpen] = useState(false)
+  const signatureRef = useRef('')
+
+  useLayoutEffect(() => {
+    // The bar's own host ref is attached before this effect runs; the scroll
+    // container is its parent by the mount contract above.
+    const container = barRef.current?.parentElement ?? null
+    if (container === null) return
+    const scan = (): void => {
+      const found: TocEntry[] = []
+      for (const el of container.querySelectorAll<HTMLElement>('h1, h2, h3, h4, h5, h6')) {
+        const text = (el.textContent ?? '').trim()
+        if (text === '') continue
+        found.push({ level: Number(el.tagName.charAt(1)), text, el })
+      }
+      const signature = signatureOf(found)
+      if (signature === signatureRef.current) return
+      signatureRef.current = signature
+      setEntries(found)
+    }
+    scan()
+    const observer = new MutationObserver(() => { scan() })
+    observer.observe(container, { childList: true, subtree: true })
+    return () => { observer.disconnect() }
+  }, [])
+
+  // Esc closes the popover (the panel is a sibling of the button, so focus
+  // stays wherever the user came from — a document listener is the simplest).
+  useLayoutEffect(() => {
+    if (!open) return
+    const onKey = (event: KeyboardEvent): void => {
+      if (event.key === 'Escape') setOpen(false)
+    }
+    document.addEventListener('keydown', onKey)
+    return () => { document.removeEventListener('keydown', onKey) }
+  }, [open])
+
+  const jump = (entry: TocEntry): void => {
+    entry.el.closest('details:not([open])')?.setAttribute('open', '')
+    entry.el.scrollIntoView({ behavior: 'smooth', block: 'start' })
+    const el = entry.el
+    const flash = css.tocFlash
+    if (flash !== undefined) {
+      el.classList.add(flash)
+      window.setTimeout(() => { el.classList.remove(flash) }, 1200)
+    }
+    setOpen(false)
+  }
+
+  const showOutline = entries.length >= TOC_MIN_HEADINGS
+  return (
+    <div className={css.tocBar} ref={barRef}>
+      {open && showOutline && (
+        <div className={css.tocPanel} data-dsh-md-toc-panel>
+          {entries.map((entry, index) => (
+            <button
+              key={index}
+              type="button"
+              className={css.tocItem}
+              data-level={entry.level}
+              title={entry.text}
+              onClick={() => { jump(entry) }}
+            >
+              <span className={css.tocItemLevel}>{entry.level}</span>
+              <span className={css.tocItemText}>{entry.text}</span>
+            </button>
+          ))}
+        </div>
+      )}
+      {showOutline && (
+        <button
+          type="button"
+          className={css.tocButton}
+          data-dsh-md-toc=""
+          aria-label={t('toc')}
+          title={t('toc')}
+          aria-expanded={open}
+          onClick={() => { setOpen(!open) }}
+        >
+          <IconListPenOutline16 />
+        </button>
+      )}
+    </div>
+  )
+}

src/client/mermaid-blocks.ts

@@ -32,13 +32,13 @@ export interface MermaidMarkdownProps {
 }
 
 /** CommonMark opening fence: 0-3 spaces indent + a run of 3+ backticks or tildes. */
-const OPEN_FENCE_RE = /^ {0,3}(`{3,}|~{3,})/
+export const OPEN_FENCE_RE = /^ {0,3}(`{3,}|~{3,})/
 
 /** A closing-fence line: 0-3 spaces indent + 3+ backticks/tildes + trailing spaces only. */
-const CLOSE_FENCE_RE = /^ {0,3}(`{3,}|~{3,})[ \t]*$/
+export const CLOSE_FENCE_RE = /^ {0,3}(`{3,}|~{3,})[ \t]*$/
 
 /** Parse the info string from the line tail after the fence run; null when invalid. */
-function fenceInfo(rest: string, fence: string): string | null {
+export function fenceInfo(rest: string, fence: string): string | null {
   const info = rest.trimStart().split(/\s+/)[0] ?? ''
   // CommonMark: a backtick fence's info string may not contain backticks —
   // such a line is not an opening fence at all.

src/client/sidebar.module.css

@@ -2758,3 +2758,135 @@ body[data-dsh-sidebar-dragging] .bottomPanel {
 .openWithPinActive {
   color: var(--dsw-alias-state-business-primary);
 }
+
+/* ── Markdown preview: raw-HTML runs + table of contents ─────────────────
+   The HTML runs lifted out of the markdown source (MarkdownHtml.tsx) render
+   as sanitized block leaves; the TOC is a zero-height sticky bar keeping the
+   outline button pinned at the preview's top-right without consuming layout.
+   All visuals ride the alias tokens (skin system follows automatically). */
+
+/* A sanitized HTML run leaf (block-level box; content is DOMPurify output). */
+.editorHtmlBlock {
+  margin: 8px 0;
+}
+
+.editorHtmlBlock img,
+.editorHtmlBlock video {
+  max-width: 100%;
+}
+
+.editorHtmlBlock details {
+  margin: 4px 0;
+  padding: 4px 0;
+}
+
+.editorHtmlBlock summary {
+  cursor: pointer;
+}
+
+/* The zero-height sticky bar: occupies no layout, keeps the button visible
+   while the preview scrolls, and lets pointer events pass through the bar
+   itself (only the interactive children re-enable them). */
+.tocBar {
+  position: sticky;
+  top: 0;
+  z-index: 3;
+  display: flex;
+  justify-content: flex-end;
+  height: 0;
+  pointer-events: none;
+}
+
+.tocButton {
+  pointer-events: auto;
+  display: inline-flex;
+  align-items: center;
+  justify-content: center;
+  width: 26px;
+  height: 26px;
+  margin: 4px 2px 0 0;
+  padding: 0;
+  border: 1px solid var(--dsw-alias-border-l1);
+  border-radius: 6px;
+  background: var(--dsw-alias-bg-layer-1);
+  color: var(--dsw-alias-label-secondary);
+  cursor: pointer;
+}
+
+.tocButton:hover {
+  background: var(--dsw-alias-interactive-bg-hover);
+  color: var(--dsw-alias-label-primary);
+}
+
+/* The outline popover, anchored under the button (the bar is the containing
+   block; its height is 0, so the panel drops below the pinned button row). */
+.tocPanel {
+  position: absolute;
+  top: 32px;
+  right: 2px;
+  display: flex;
+  flex-direction: column;
+  width: min(300px, 82%);
+  max-height: 60vh;
+  overflow-y: auto;
+  padding: 4px;
+  border: 1px solid var(--dsw-alias-border-l1);
+  border-radius: 8px;
+  background: var(--dsw-alias-bg-layer-2);
+  box-shadow: var(--dsw-shadow-lv2);
+  pointer-events: auto;
+}
+
+.tocItem {
+  display: flex;
+  align-items: baseline;
+  gap: 8px;
+  min-width: 0;
+  padding: 4px 8px;
+  border: none;
+  border-radius: 6px;
+  background: transparent;
+  color: var(--dsw-alias-label-secondary);
+  font: var(--dsw-font-xxs-12);
+  text-align: left;
+  cursor: pointer;
+}
+
+.tocItem:hover {
+  background: var(--dsw-alias-interactive-bg-hover);
+  color: var(--dsw-alias-label-primary);
+}
+
+/* Indent by heading level (h2 = one step, h3 = two steps…). */
+.tocItem[data-level='2'] { padding-left: 18px; }
+.tocItem[data-level='3'] { padding-left: 28px; }
+.tocItem[data-level='4'] { padding-left: 38px; }
+.tocItem[data-level='5'] { padding-left: 48px; }
+.tocItem[data-level='6'] { padding-left: 58px; }
+
+/* The tiny level number keeps deep outlines scannable. */
+.tocItemLevel {
+  flex: none;
+  font: var(--dsw-font-xxxs-11);
+  color: var(--dsw-alias-label-tertiary);
+}
+
+.tocItemText {
+  flex: 1 1 auto;
+  min-width: 0;
+  overflow: hidden;
+  text-overflow: ellipsis;
+  white-space: nowrap;
+}
+
+/* The jumped-to heading flashes once (the class is added to the host-rendered
+   heading element by md-toc.tsx; @keyframes rides the CSS module). */
+@keyframes dsh-toc-flash {
+  0%, 60% { background: var(--dsw-alias-interactive-bg-hover); }
+  100% { background: transparent; }
+}
+
+.tocFlash {
+  animation: dsh-toc-flash 1.2s ease-out;
+  border-radius: 4px;
+}