feat(renderer): Mermaid diagram rendering with dark theme (M10.7)

- Lazy-loads Mermaid.js on first ```mermaid block detected
- Dark theme with Bitcoin orange accent colors
- Cached renders to avoid re-rendering on scroll
- Error display inline without crashing app

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

packages/app/package.json

@@ -24,6 +24,7 @@
     "katex": "^0.16.33",
     "leaflet": "^1.9.4",
     "markdown-it": "^14.1.1",
+    "mermaid": "^11.12.3",
     "pdfjs-dist": "^5.5.207",
     "pinia": "^3.0.4",
     "plyr": "^3.8.4",

packages/app/src/components/chat/ChatMessage.vue

@@ -326,6 +326,7 @@
 import { computed, ref, nextTick, watch } from 'vue'
 import MarkdownIt from 'markdown-it'
 import { hasMath, renderMathInHtml } from '@/composables/useMathRenderer'
+import { hasMermaid, renderMermaidBlocks } from '@/composables/useMermaidRenderer'
 import ContextMenu from '@/components/ui/ContextMenu.vue'
 import ContextMenuItem from '@/components/ui/ContextMenuItem.vue'
 import type { Message, WebSearchResult } from '@aiui/core/types/message'
@@ -497,14 +498,17 @@ const displayText = computed(() => {
 const baseMarkdown = computed(() => md.render(displayText.value))
 const renderedMarkdown = ref('')
 
-// Render math after markdown, batch on content change
+// Render math/mermaid after markdown, batch on content change
 watch(baseMarkdown, async (html) => {
+  let result = html
+  renderedMarkdown.value = html // Show immediately
   if (hasMath(displayText.value)) {
-    renderedMarkdown.value = html // Show immediately
-    renderedMarkdown.value = await renderMathInHtml(html)
-  } else {
-    renderedMarkdown.value = html
+    result = await renderMathInHtml(result)
   }
+  if (hasMermaid(displayText.value)) {
+    result = await renderMermaidBlocks(result)
+  }
+  renderedMarkdown.value = result
 }, { immediate: true })
 
 const formattedTime = computed(() => {

packages/app/src/composables/useMermaidRenderer.ts

@@ -0,0 +1,96 @@
+/**
+ * Lazy Mermaid diagram rendering for ```mermaid code blocks.
+ * Dark theme matching glass design, cached renders.
+ */
+
+let mermaidModule: typeof import('mermaid') | null = null
+let mermaidLoading: Promise<typeof import('mermaid')> | null = null
+let mermaidInitialized = false
+
+async function loadMermaid() {
+  if (mermaidModule) return mermaidModule
+  if (mermaidLoading) return mermaidLoading
+  mermaidLoading = import('mermaid').then((m) => {
+    mermaidModule = m
+    return m
+  })
+  return mermaidLoading
+}
+
+function initMermaid() {
+  if (mermaidInitialized || !mermaidModule) return
+  mermaidModule.default.initialize({
+    startOnLoad: false,
+    theme: 'dark',
+    themeVariables: {
+      primaryColor: '#F7931A',
+      primaryTextColor: '#fff',
+      primaryBorderColor: '#F7931A',
+      lineColor: '#666',
+      secondaryColor: '#1a1a1a',
+      tertiaryColor: '#111',
+      background: '#0a0a0a',
+      mainBkg: '#1a1a1a',
+      nodeBorder: '#444',
+      clusterBkg: '#111',
+      clusterBorder: '#333',
+      titleColor: '#ddd',
+      edgeLabelBackground: '#1a1a1a',
+    },
+    fontFamily: 'Inter, system-ui, sans-serif',
+    fontSize: 13,
+  })
+  mermaidInitialized = true
+}
+
+// Cache rendered diagrams
+const renderCache = new Map<string, string>()
+
+export function hasMermaid(text: string): boolean {
+  return /```mermaid/i.test(text)
+}
+
+let renderCounter = 0
+
+export async function renderMermaidBlocks(html: string): Promise<string> {
+  await loadMermaid()
+  initMermaid()
+
+  const mermaid = mermaidModule!.default
+
+  // Find <pre><code class="language-mermaid">...</code></pre> blocks
+  const PRE_RE = /<pre><code class="language-mermaid">([\s\S]*?)<\/code><\/pre>/gi
+  const matches = [...html.matchAll(PRE_RE)]
+  if (matches.length === 0) return html
+
+  let result = html
+  for (const match of matches) {
+    const raw = match[1]
+      .replace(/&amp;/g, '&')
+      .replace(/&lt;/g, '<')
+      .replace(/&gt;/g, '>')
+      .replace(/&quot;/g, '"')
+      .replace(/&#39;/g, "'")
+      .trim()
+
+    const cacheKey = raw
+    if (renderCache.has(cacheKey)) {
+      result = result.replace(match[0], renderCache.get(cacheKey)!)
+      continue
+    }
+
+    try {
+      const id = `mermaid-${++renderCounter}`
+      const { svg } = await mermaid.render(id, raw)
+      const wrapped = `<div class="mermaid-diagram my-4 overflow-x-auto rounded-lg bg-white/5 border border-white/5 p-4">${svg}</div>`
+      renderCache.set(cacheKey, wrapped)
+      result = result.replace(match[0], wrapped)
+    } catch {
+      // Show error inline without crashing
+      const errHtml = `<div class="my-4 p-3 rounded-lg bg-red-500/10 border border-red-500/20 text-xs text-red-400/70">Mermaid render error</div><pre><code>${match[1]}</code></pre>`
+      result = result.replace(match[0], errHtml)
+    }
+  }
+
+  return result
+}