diff --git a/apps/web/package.json b/apps/web/package.json
index 700e4dc0..b9975f8f 100644
--- a/apps/web/package.json
+++ b/apps/web/package.json
@@ -6,6 +6,7 @@
   "dependencies": {
     "@antv/x6": "3.1.8",
     "@codemirror/lang-markdown": "^6.5.2",
+    "@lezer/highlight": "^1.2.3",
     "@edgeever/client": "workspace:*",
     "@floating-ui/react-dom": "^2.1.8",
     "@fontsource-variable/noto-sans-sc": "^5.2.8",
diff --git a/apps/web/src/components/EditorToolbar.tsx b/apps/web/src/components/EditorToolbar.tsx
index 697919cb..82b2038d 100644
--- a/apps/web/src/components/EditorToolbar.tsx
+++ b/apps/web/src/components/EditorToolbar.tsx
@@ -35,6 +35,7 @@ import {
 import { CODE_BLOCK_LANGUAGES, getCodeBlockLanguageValue } from "@/lib/code-block";
 import { EditorTableMenu } from "@/components/EditorTableMenu";
 import { wrapIndentedParagraphInList } from "@/lib/editor-shortcuts";
+import { MARKDOWN_THEME_PREFERENCES, useMarkdownTheme } from "@/components/ThemeProvider";
 
 const EditorToolbarButton = ({
   active = false,
@@ -159,6 +160,7 @@ export const EditorToolbar = ({
   externalLinkActive?: boolean;
 }) => {
   const { t } = useTranslation();
+  const { markdownThemePreference, setMarkdownTheme } = useMarkdownTheme();
   const controlsRef = useRef<HTMLDivElement>(null);
   const [expanded, setExpanded] = useState(readEditorToolbarExpandedPreference);
   const [hasOverflow, setHasOverflow] = useState(false);
@@ -366,7 +368,24 @@ export const EditorToolbar = ({
             </>
           )}
           {markdownMode ? (
-            <span className="shrink-0 text-xs text-slate-500">{t("editorToolbar.markdownSource")}</span>
+            <Select
+              value={markdownThemePreference}
+              onValueChange={(value) => setMarkdownTheme(value as typeof markdownThemePreference)}
+            >
+              <SelectTrigger
+                aria-label={t("editorToolbar.markdownTheme")}
+                className="h-8 w-[11.5rem] shrink-0 whitespace-nowrap border-slate-200 bg-card text-xs text-slate-800 [&>span]:truncate [&>span]:whitespace-nowrap"
+              >
+                <SelectValue />
+              </SelectTrigger>
+              <SelectContent className="bg-card border border-slate-200 rounded-md py-1 shadow-md">
+                {MARKDOWN_THEME_PREFERENCES.map((theme) => (
+                  <SelectItem key={theme} value={theme}>
+                    {t(`settings.markdownThemes.${theme}`)}
+                  </SelectItem>
+                ))}
+              </SelectContent>
+            </Select>
           ) : (
             <>
           <Select
diff --git a/apps/web/src/components/ThemeProvider.tsx b/apps/web/src/components/ThemeProvider.tsx
index 59ba2ca5..d8bcb458 100644
--- a/apps/web/src/components/ThemeProvider.tsx
+++ b/apps/web/src/components/ThemeProvider.tsx
@@ -87,6 +87,14 @@ export const MARKDOWN_THEME_NAMES = [
 export type MarkdownThemeName = (typeof MARKDOWN_THEME_NAMES)[number];
 export const MARKDOWN_THEME_PREFERENCES = ["auto", ...MARKDOWN_THEME_NAMES] as const;
 export type MarkdownThemePreference = (typeof MARKDOWN_THEME_PREFERENCES)[number];
+export const MARKDOWN_LIGHT_THEME_NAMES = [
+  "github-light",
+  "solarized-light",
+  "xcode-light",
+  "duotone-light",
+] as const satisfies readonly MarkdownThemeName[];
+export const isMarkdownLightTheme = (theme: MarkdownThemeName): boolean =>
+  (MARKDOWN_LIGHT_THEME_NAMES as readonly MarkdownThemeName[]).includes(theme);
 
 export const EDITOR_THEME_NAMES = [
   "default",
diff --git a/apps/web/src/components/editor/MarkdownSourceEditor.tsx b/apps/web/src/components/editor/MarkdownSourceEditor.tsx
index 2239a764..e8ef5a4e 100644
--- a/apps/web/src/components/editor/MarkdownSourceEditor.tsx
+++ b/apps/web/src/components/editor/MarkdownSourceEditor.tsx
@@ -6,7 +6,7 @@ import CodeMirror, {
 } from "@uiw/react-codemirror";
 import { markdown } from "@codemirror/lang-markdown";
 import {
-  githubLight,
+  githubLightInit,
   githubDark,
   atomone,
   tokyoNight,
@@ -14,17 +14,18 @@ import {
   dracula,
   nord,
   monokai,
-  solarizedLight,
+  solarizedLightInit,
   solarizedDark,
   vscodeDark,
-  xcodeLight,
+  xcodeLightInit,
   sublime,
-  duotoneLight,
+  duotoneLightInit,
   duotoneDark,
   gruvboxDark,
 } from "@uiw/codemirror-themes-all";
 import type { MarkdownThemeName } from "../ThemeProvider";
 import { getAiSlashCommandStart } from "@/lib/editor-shortcuts";
+import { lightMarkdownHighlightStyles } from "@/lib/markdown-source-highlight";
 import { cn } from "@/lib/utils";
 
 export interface MarkdownSourceEditorRef {
@@ -49,7 +50,7 @@ export interface MarkdownSourceEditorProps {
 }
 
 export const CODE_MIRROR_THEME_MAP: Record<MarkdownThemeName, Extension> = {
-  "github-light": githubLight,
+  "github-light": githubLightInit({ styles: lightMarkdownHighlightStyles }),
   "github-dark": githubDark,
   "one-dark": atomone,
   "tokyo-night": tokyoNight,
@@ -57,12 +58,12 @@ export const CODE_MIRROR_THEME_MAP: Record<MarkdownThemeName, Extension> = {
   dracula,
   nord,
   monokai,
-  "solarized-light": solarizedLight,
+  "solarized-light": solarizedLightInit({ styles: lightMarkdownHighlightStyles }),
   "solarized-dark": solarizedDark,
   "vscode-dark": vscodeDark,
-  "xcode-light": xcodeLight,
+  "xcode-light": xcodeLightInit({ styles: lightMarkdownHighlightStyles }),
   sublime,
-  "duotone-light": duotoneLight,
+  "duotone-light": duotoneLightInit({ styles: lightMarkdownHighlightStyles }),
   "duotone-dark": duotoneDark,
   "gruvbox-dark": gruvboxDark,
 };
diff --git a/apps/web/src/lib/markdown-source-highlight.ts b/apps/web/src/lib/markdown-source-highlight.ts
new file mode 100644
index 00000000..65647f67
--- /dev/null
+++ b/apps/web/src/lib/markdown-source-highlight.ts
@@ -0,0 +1,32 @@
+import { tags as t } from "@lezer/highlight";
+
+/**
+ * Appended to light CodeMirror themes so Markdown source tokens stay
+ * distinct. Later rules in the same HighlightStyle win, which is why these
+ * go through `*Init({ styles })` instead of a second highlighter.
+ */
+export const lightMarkdownHighlightStyles = [
+  { tag: t.heading1, color: "#0550ae", fontWeight: "700" },
+  { tag: t.heading2, color: "#0550ae", fontWeight: "700" },
+  { tag: t.heading3, color: "#0a3069", fontWeight: "700" },
+  { tag: t.heading4, color: "#0f766e", fontWeight: "700" },
+  { tag: t.heading5, color: "#0f766e", fontWeight: "700" },
+  { tag: t.heading6, color: "#0f766e", fontWeight: "700" },
+  { tag: t.heading, color: "#0550ae", fontWeight: "700" },
+  { tag: t.processingInstruction, color: "#64748b" },
+  { tag: t.meta, color: "#64748b" },
+  { tag: t.comment, color: "#64748b" },
+  { tag: t.strong, color: "#0f172a", fontWeight: "700" },
+  { tag: t.emphasis, color: "#9f1239", fontStyle: "italic" },
+  { tag: t.strikethrough, color: "#64748b", textDecoration: "line-through" },
+  { tag: t.link, color: "#0969da" },
+  { tag: t.url, color: "#0969da", textDecoration: "underline" },
+  { tag: t.monospace, color: "#be185d" },
+  { tag: t.quote, color: "#15803d" },
+  { tag: t.atom, color: "#0f766e", fontWeight: "700" },
+  { tag: t.contentSeparator, color: "#94a3b8" },
+  { tag: t.labelName, color: "#7c3aed" },
+  { tag: t.string, color: "#0f766e" },
+  { tag: t.escape, color: "#b45309" },
+  { tag: t.character, color: "#b45309" },
+];
diff --git a/apps/web/src/lib/markdown-theme.test.mjs b/apps/web/src/lib/markdown-theme.test.mjs
index 9897d4bd..9dfe8535 100644
--- a/apps/web/src/lib/markdown-theme.test.mjs
+++ b/apps/web/src/lib/markdown-theme.test.mjs
@@ -1,11 +1,15 @@
 import { describe, expect, test } from "bun:test";
+import { readFileSync } from "node:fs";
 import {
   getStoredMarkdownTheme,
+  isMarkdownLightTheme,
+  MARKDOWN_LIGHT_THEME_NAMES,
   MARKDOWN_THEME_NAMES,
   MARKDOWN_THEME_PREFERENCES,
   resolveMarkdownTheme,
 } from "../components/ThemeProvider";
 import { CODE_MIRROR_THEME_MAP } from "../components/editor/MarkdownSourceEditor";
+import { lightMarkdownHighlightStyles } from "./markdown-source-highlight";
 
 describe("markdown theme contracts", () => {
   test("automatic Markdown themes follow the resolved appearance", () => {
@@ -34,4 +38,28 @@ describe("markdown theme contracts", () => {
       expect(extension).toBeDefined();
     }
   });
+
+  test("light markdown themes receive an extra syntax highlight layer", () => {
+    const editorSource = readFileSync(new URL("../components/editor/MarkdownSourceEditor.tsx", import.meta.url), "utf8");
+    expect(lightMarkdownHighlightStyles.length).toBeGreaterThan(0);
+    expect(editorSource).toContain("lightMarkdownHighlightStyles");
+    for (const theme of MARKDOWN_LIGHT_THEME_NAMES) {
+      expect(MARKDOWN_THEME_NAMES).toContain(theme);
+      expect(isMarkdownLightTheme(theme)).toBe(true);
+      expect(CODE_MIRROR_THEME_MAP[theme]).toBeDefined();
+      expect(editorSource).toContain(`"${theme}":`);
+    }
+    expect(isMarkdownLightTheme("tokyo-night")).toBe(false);
+    expect(editorSource).toContain("githubLightInit({ styles: lightMarkdownHighlightStyles })");
+    expect(editorSource).toContain("xcodeLightInit({ styles: lightMarkdownHighlightStyles })");
+  });
+
+  test("the editor toolbar can switch Markdown source themes", () => {
+    const toolbar = readFileSync(new URL("../components/EditorToolbar.tsx", import.meta.url), "utf8");
+    expect(toolbar).toContain("useMarkdownTheme");
+    expect(toolbar).toContain("MARKDOWN_THEME_PREFERENCES");
+    expect(toolbar).toContain("markdownThemePreference");
+    expect(toolbar).toContain('t("editorToolbar.markdownTheme")');
+    expect(toolbar).not.toContain('t("editorToolbar.markdownSource")');
+  });
 });
diff --git a/bun.lock b/bun.lock
index f171a748..0874babf 100644
--- a/bun.lock
+++ b/bun.lock
@@ -95,7 +95,7 @@
     },
     "apps/desktop": {
       "name": "@edgeever/desktop",
-      "version": "1.59.0",
+      "version": "1.67.0",
       "dependencies": {
         "@edgeever/public-network": "workspace:*",
         "croner": "^10.0.1",
@@ -217,6 +217,7 @@
         "@edgeever/client": "workspace:*",
         "@floating-ui/react-dom": "^2.1.8",
         "@fontsource-variable/noto-sans-sc": "^5.2.8",
+        "@lezer/highlight": "^1.2.3",
         "@tiptap/extension-code-block-lowlight": "3.31.0",
         "@tiptap/pm": "3.31.0",
         "@uiw/codemirror-themes-all": "^4.25.11",
diff --git a/packages/shared/src/i18n/en-US.ts b/packages/shared/src/i18n/en-US.ts
index ed7fb52f..45f89183 100644
--- a/packages/shared/src/i18n/en-US.ts
+++ b/packages/shared/src/i18n/en-US.ts
@@ -1879,6 +1879,7 @@ export const enUS = {
     markdown: "Switch to Markdown source",
     richText: "Switch to rich text",
     markdownSource: "Markdown source",
+    markdownTheme: "Markdown source theme",
     switchToMarkdown: "Switch to Markdown mode",
     switchToRichText: "Switch to rich text mode",
     attachment: "Upload attachment",
diff --git a/packages/shared/src/i18n/zh-CN.ts b/packages/shared/src/i18n/zh-CN.ts
index 49b95e7e..3ede294c 100644
--- a/packages/shared/src/i18n/zh-CN.ts
+++ b/packages/shared/src/i18n/zh-CN.ts
@@ -1877,6 +1877,7 @@ export const zhCN = {
     markdown: "切换到 Markdown 源码",
     richText: "切换到富文本编辑",
     markdownSource: "Markdown 源码",
+    markdownTheme: "Markdown 源码主题",
     switchToMarkdown: "切换到 Markdown 模式",
     switchToRichText: "切换到富文本模式",
     attachment: "上传附件",