diff --git a/packages/app/package.json b/packages/app/package.json
index 6caa4d42..2cd48987 100644
--- a/packages/app/package.json
+++ b/packages/app/package.json
@@ -21,6 +21,7 @@
   "dependencies": {
     "@aiui/core": "workspace:*",
     "@tanstack/vue-virtual": "^3.13.19",
+    "katex": "^0.16.33",
     "leaflet": "^1.9.4",
     "markdown-it": "^14.1.1",
     "pdfjs-dist": "^5.5.207",
diff --git a/packages/app/src/components/chat/ChatMessage.vue b/packages/app/src/components/chat/ChatMessage.vue
index 7e865174..7aa7f2a9 100644
--- a/packages/app/src/components/chat/ChatMessage.vue
+++ b/packages/app/src/components/chat/ChatMessage.vue
@@ -323,8 +323,9 @@
 </template>
 
 <script setup lang="ts">
-import { computed, ref, nextTick } from 'vue'
+import { computed, ref, nextTick, watch } from 'vue'
 import MarkdownIt from 'markdown-it'
+import { hasMath, renderMathInHtml } from '@/composables/useMathRenderer'
 import ContextMenu from '@/components/ui/ContextMenu.vue'
 import ContextMenuItem from '@/components/ui/ContextMenuItem.vue'
 import type { Message, WebSearchResult } from '@aiui/core/types/message'
@@ -493,9 +494,18 @@ const displayText = computed(() => {
   return text
 })
 
-const renderedMarkdown = computed(() => {
-  return md.render(displayText.value)
-})
+const baseMarkdown = computed(() => md.render(displayText.value))
+const renderedMarkdown = ref('')
+
+// Render math after markdown, batch on content change
+watch(baseMarkdown, async (html) => {
+  if (hasMath(displayText.value)) {
+    renderedMarkdown.value = html // Show immediately
+    renderedMarkdown.value = await renderMathInHtml(html)
+  } else {
+    renderedMarkdown.value = html
+  }
+}, { immediate: true })
 
 const formattedTime = computed(() => {
   const d = new Date(props.message.timestamp)
diff --git a/packages/app/src/composables/useMathRenderer.ts b/packages/app/src/composables/useMathRenderer.ts
new file mode 100644
index 00000000..fbe91d7c
--- /dev/null
+++ b/packages/app/src/composables/useMathRenderer.ts
@@ -0,0 +1,66 @@
+/**
+ * Lazy KaTeX math rendering for markdown content.
+ * Detects $...$ (inline) and $$...$$ (block) LaTeX.
+ * Falls back to raw <code> on invalid LaTeX.
+ */
+
+let katexModule: typeof import('katex') | null = null
+let katexLoading: Promise<typeof import('katex')> | null = null
+
+async function loadKaTeX() {
+  if (katexModule) return katexModule
+  if (katexLoading) return katexLoading
+  katexLoading = import('katex').then((m) => {
+    katexModule = m
+    // Inject KaTeX CSS
+    if (!document.getElementById('katex-css')) {
+      const link = document.createElement('link')
+      link.id = 'katex-css'
+      link.rel = 'stylesheet'
+      link.href = new URL('katex/dist/katex.min.css', import.meta.url).toString()
+      document.head.appendChild(link)
+    }
+    return m
+  })
+  return katexLoading
+}
+
+const BLOCK_RE = /\$\$([\s\S]+?)\$\$/g
+const INLINE_RE = /\$([^\n$]+?)\$/g
+
+function renderKaTeX(latex: string, displayMode: boolean): string {
+  if (!katexModule) return `<code>${escapeForHtml(latex)}</code>`
+  try {
+    return katexModule.default.renderToString(latex, {
+      displayMode,
+      throwOnError: false,
+      output: 'html',
+    })
+  } catch {
+    return `<code>${escapeForHtml(latex)}</code>`
+  }
+}
+
+function escapeForHtml(s: string): string {
+  return s.replace(/&/g, '&amp;').replace(/</g, '&lt;').replace(/>/g, '&gt;')
+}
+
+export function hasMath(text: string): boolean {
+  return /\$\$[\s\S]+?\$\$/.test(text) || /\$[^\n$]+?\$/.test(text)
+}
+
+export async function renderMathInHtml(html: string): Promise<string> {
+  await loadKaTeX()
+
+  // Block math first ($$...$$)
+  let result = html.replace(BLOCK_RE, (_, latex) => {
+    return `<div class="katex-block my-4 text-center overflow-x-auto">${renderKaTeX(latex.trim(), true)}</div>`
+  })
+
+  // Inline math ($...$)
+  result = result.replace(INLINE_RE, (_, latex) => {
+    return renderKaTeX(latex.trim(), false)
+  })
+
+  return result
+}
diff --git a/pnpm-lock.yaml b/pnpm-lock.yaml
index c92b6b3f..c341fe54 100644
--- a/pnpm-lock.yaml
+++ b/pnpm-lock.yaml
@@ -27,6 +27,9 @@ importers:
       '@tanstack/vue-virtual':
         specifier: ^3.13.19
         version: 3.13.19(vue@3.5.29(typescript@5.8.3))
+      katex:
+        specifier: ^0.16.33
+        version: 0.16.33
       leaflet:
         specifier: ^1.9.4
         version: 1.9.4
@@ -1600,6 +1603,10 @@ packages:
   commander@2.20.3:
     resolution: {integrity: sha512-GpVkmM8vF2vQUkj2LvZmD35JxeJOLCwJ9cUkugyk2nuhbv3+mJvpLYYt+0+USMxE+oj+ey/lJEnhZw75x/OMcQ==}
 
+  commander@8.3.0:
+    resolution: {integrity: sha512-OkTL9umf+He2DZkUq8f8J9of7yL6RJKI24dVITBmNfZBmri9zYZQrKkuXiKhyfPSu8tUhnVBB1iKXevvnlR4Ww==}
+    engines: {node: '>= 12'}
+
   common-tags@1.8.2:
     resolution: {integrity: sha512-gk/Z852D2Wtb//0I+kRFNKKE9dIIVirjoqPoA1wJU+XePVXZfGeBpk45+A1rKO4Q43prqWBNY/MiIeRLbPWUaA==}
     engines: {node: '>=4.0.0'}
@@ -2171,6 +2178,10 @@ packages:
     resolution: {integrity: sha512-p/nXbhSEcu3pZRdkW1OfJhpsVtW1gd4Wa1fnQc9YLiTfAjn0312eMKimbdIQzuZl9aa9xUGaRlP9T/CJE/ditQ==}
     engines: {node: '>=0.10.0'}
 
+  katex@0.16.33:
+    resolution: {integrity: sha512-q3N5u+1sY9Bu7T4nlXoiRBXWfwSefNGoKeOwekV+gw0cAXQlz2Ww6BLcmBxVDeXBMUDQv6fK5bcNaJLxob3ZQA==}
+    hasBin: true
+
   keyv@4.5.4:
     resolution: {integrity: sha512-oxVHkHR/EJf2CNXnWxRLW6mg7JyCCUcG0DtEGmL2ctUo1PNTin1PUil+r/+4r5MpVgC/fn1kjsx7mjSujKqIpw==}
 
@@ -4654,6 +4665,8 @@ snapshots:
 
   commander@2.20.3: {}
 
+  commander@8.3.0: {}
+
   common-tags@1.8.2: {}
 
   confbox@0.1.8: {}
@@ -5293,6 +5306,10 @@ snapshots:
 
   jsonpointer@5.0.1: {}
 
+  katex@0.16.33:
+    dependencies:
+      commander: 8.3.0
+
   keyv@4.5.4:
     dependencies:
       json-buffer: 3.0.1