diff --git a/.gitignore b/.gitignore
index 82606b160..b1d476204 100644
--- a/.gitignore
+++ b/.gitignore
@@ -29,6 +29,7 @@ Thumbs.db
 playwright-report/
 test-results/
 blob-report/
+.playwright-mcp/
 
 # Node modules (pnpm workspace hoists to root)
 node_modules/
diff --git a/crates/sprout-acp/src/base_prompt.md b/crates/sprout-acp/src/base_prompt.md
index 5bec46770..bb9fe3762 100644
--- a/crates/sprout-acp/src/base_prompt.md
+++ b/crates/sprout-acp/src/base_prompt.md
@@ -23,6 +23,7 @@ Run `sprout --help` or `sprout <group> --help` for full usage.
 ## Communication Patterns
 
 - Address agents and humans with plain `@name` — do NOT bold or italicize mention text (formatting prevents alert delivery).
+- Message content supports GitHub-flavored Markdown. Use fenced code blocks with a language tag (` ```python `, ` ```typescript `, etc.) for syntax-highlighted rendering on desktop and mobile. Omitting the language tag renders monochrome.
 - Use `sprout messages thread` when responding in-thread; post new messages for new topics.
 - No push notifications — poll with `sprout messages get --channel <UUID> --since <ts>`. When `since` is set without `before`, results are oldest-first (chronological).
 
diff --git a/crates/sprout-mcp/src/server.rs b/crates/sprout-mcp/src/server.rs
index 3e5c29d5d..6b69ec297 100644
--- a/crates/sprout-mcp/src/server.rs
+++ b/crates/sprout-mcp/src/server.rs
@@ -170,7 +170,8 @@ async fn resolve_content_mentions(
 pub struct SendMessageParams {
     /// UUID of the channel to post to.
     pub channel_id: String,
-    /// Message body text.
+    /// Message body text. Supports GitHub-flavored Markdown including fenced code
+    /// blocks with syntax highlighting.
     pub content: String,
     /// Nostr event kind. Defaults to KIND_STREAM_MESSAGE (NIP-29 group chat message).
     #[serde(default = "default_kind")]
@@ -890,7 +891,9 @@ impl SproutMcpServer {
     /// Send a message to a Sprout channel.
     #[tool(
         name = "send_message",
-        description = "Send a message to a Sprout channel. Include `parent_event_id` to reply in a thread. \
+        description = "Send a message to a Sprout channel. Content supports GitHub-flavored Markdown — \
+use fenced code blocks with a language tag for syntax-highlighted rendering. \
+Include `parent_event_id` to reply in a thread. \
 Set `broadcast_to_channel` to also surface the reply in the main channel timeline. \
 For forum channels, set `kind` to 45001 (post) or 45003 (comment with `parent_event_id`). \
 Default kind is 9 (stream message)."
diff --git a/desktop/src-tauri/src/managed_agents/nest_skill.md b/desktop/src-tauri/src/managed_agents/nest_skill.md
index 5b24d2f1a..fb856f044 100644
--- a/desktop/src-tauri/src/managed_agents/nest_skill.md
+++ b/desktop/src-tauri/src/managed_agents/nest_skill.md
@@ -74,6 +74,15 @@ Write commands are unaffected. `--format json` (default) returns full fields.
 
 Other kind values are rejected. Use `messages vote --event <id> --direction up|down` to vote on forum posts.
 
+## Message Formatting
+
+Message content is rendered as GitHub-flavored Markdown on both desktop and mobile. Key formatting:
+
+- **Fenced code blocks**: triple-backtick with a language tag for syntax highlighting (190+ languages supported). Omitting the language tag renders a styled monochrome block.
+- **Inline code**: single backticks for inline monospace.
+- **Mentions**: plain `@name` — do NOT bold or italicize (formatting prevents alert delivery).
+- **Links, images, tables, blockquotes, headings**: standard GFM.
+
 ## Mem Patch Workflow
 
 For safe concurrent writes, use hash-based conflict detection:
diff --git a/desktop/src/features/messages/lib/codeBlockExtensions.ts b/desktop/src/features/messages/lib/codeBlockExtensions.ts
index 73c468225..c3490eda4 100644
--- a/desktop/src/features/messages/lib/codeBlockExtensions.ts
+++ b/desktop/src/features/messages/lib/codeBlockExtensions.ts
@@ -23,7 +23,20 @@ export function handleCodeFenceEnter(ed: Editor): boolean | undefined {
     "",
   );
 
-  if (FENCE_AT_START.test(textBefore)) return false;
+  const startMatch = textBefore.match(FENCE_AT_START);
+  if (startMatch) {
+    const { tr, schema } = ed.state;
+    const attrs = startMatch[1] ? { language: startMatch[1] } : {};
+    tr.delete($cursor.start(), $cursor.pos);
+    tr.setBlockType(
+      tr.mapping.map($cursor.start()),
+      tr.mapping.map($cursor.start()),
+      schema.nodes.codeBlock,
+      attrs,
+    );
+    ed.view.dispatch(tr);
+    return true;
+  }
 
   const m = textBefore.match(FENCE_AFTER_BREAK);
   if (!m) return undefined;
diff --git a/desktop/src/shared/styles/globals.css b/desktop/src/shared/styles/globals.css
index 99a37101b..eafb1dce1 100644
--- a/desktop/src/shared/styles/globals.css
+++ b/desktop/src/shared/styles/globals.css
@@ -173,6 +173,43 @@
   }
 }
 
+/* ── Code block line numbers & diff ────────────────────────────────── */
+.code-block-lines {
+  counter-reset: code-line;
+}
+
+.code-block-lines [data-line] {
+  display: block;
+  counter-increment: code-line;
+}
+
+.code-block-lines [data-line]::before {
+  content: counter(code-line);
+  display: inline-block;
+  width: 2.5ch;
+  margin-right: 1.5ch;
+  text-align: right;
+  color: hsl(var(--muted-foreground) / 0.4);
+  user-select: none;
+  pointer-events: none;
+}
+
+.code-line-diff-add {
+  background-color: hsl(120 40% 50% / 0.15);
+}
+
+.code-line-diff-remove {
+  background-color: hsl(0 60% 50% / 0.15);
+}
+
+.dark .code-line-diff-add {
+  background-color: hsl(120 40% 50% / 0.12);
+}
+
+.dark .code-line-diff-remove {
+  background-color: hsl(0 60% 50% / 0.12);
+}
+
 @layer base {
   :root {
     /* Catppuccin Latte (mauve accent) */
diff --git a/desktop/src/shared/ui/markdown.tsx b/desktop/src/shared/ui/markdown.tsx
index 4ac8f36f8..0c3b49c22 100644
--- a/desktop/src/shared/ui/markdown.tsx
+++ b/desktop/src/shared/ui/markdown.tsx
@@ -9,6 +9,15 @@ import remarkBreaks from "remark-breaks";
 import remarkGfm from "remark-gfm";
 import { toast } from "sonner";
 
+import {
+  getSingletonHighlighter,
+  type HighlighterGeneric,
+  type BundledLanguage,
+  type BundledTheme,
+  type ThemedToken,
+} from "shiki";
+
+import { useTheme } from "@/shared/theme/ThemeProvider";
 import { useAppNavigation } from "@/app/navigation/useAppNavigation";
 import {
   isMessageLink,
@@ -49,6 +58,59 @@ type ImetaEntry = {
 
 type ImetaLookup = Map<string, ImetaEntry>;
 
+let shikiHighlighter: HighlighterGeneric<BundledLanguage, BundledTheme> | null =
+  null;
+let shikiInitPromise: Promise<void> | null = null;
+const loadedLangs = new Set<string>();
+const loadedThemes = new Set<string>();
+const tokenCache = new Map<string, ThemedToken[][]>();
+const MAX_CACHE_ENTRIES = 100;
+const MAX_LOADED_LANGUAGES = 30;
+const MAX_HIGHLIGHT_LINES = 150;
+const CODE_BLOCK_CLASS =
+  "code-block-lines block min-w-full whitespace-pre font-mono text-[13px] leading-6 text-foreground";
+const DIFF_ADD_RE = /\s*\/\/\s*\[!code\s*\+\+\]\s*$/;
+const DIFF_REMOVE_RE = /\s*\/\/\s*\[!code\s*--\]\s*$/;
+
+function ensureHighlighter(): Promise<void> {
+  if (shikiHighlighter) return Promise.resolve();
+  if (!shikiInitPromise) {
+    shikiInitPromise = getSingletonHighlighter({
+      themes: [],
+      langs: [],
+    }).then((h) => {
+      shikiHighlighter = h;
+    });
+  }
+  return shikiInitPromise;
+}
+
+function extractLanguage(className?: string): string {
+  if (typeof className !== "string") return "";
+  const match = className.match(/language-(\S+)/);
+  return match ? match[1] : "";
+}
+
+function stripDiffMarker(tokens: ThemedToken[], marker: RegExp): ThemedToken[] {
+  const last = tokens[tokens.length - 1];
+  if (!last) return tokens;
+  const stripped = last.content.replace(marker, "");
+  if (stripped === last.content) return tokens;
+  if (stripped === "") return tokens.slice(0, -1);
+  return [...tokens.slice(0, -1), { ...last, content: stripped }];
+}
+
+function useStableArray<T>(arr: T[]): T[] {
+  const ref = React.useRef(arr);
+  if (
+    arr.length !== ref.current.length ||
+    arr.some((item, i) => item !== ref.current[i])
+  ) {
+    ref.current = arr;
+  }
+  return ref.current;
+}
+
 /**
  * `urlTransform` for `<ReactMarkdown>` that preserves `sprout://message?…`
  * links. The default transform strips unknown schemes (returns `""`) before
@@ -158,7 +220,13 @@ function getCodeBlockText(children: React.ReactNode) {
   return getReactNodeText(children).replace(/\n$/, "");
 }
 
-function MarkdownCodeBlock({ children }: { children?: React.ReactNode }) {
+function MarkdownCodeBlock({
+  children,
+  language,
+}: {
+  children?: React.ReactNode;
+  language?: string;
+}) {
   const [isCopying, setIsCopying] = React.useState(false);
   const code = React.useMemo(() => getCodeBlockText(children), [children]);
 
@@ -183,7 +251,12 @@ function MarkdownCodeBlock({ children }: { children?: React.ReactNode }) {
 
   return (
     <div className="group relative" data-code-block="">
-      <pre className="overflow-x-auto rounded-xl border border-border/70 bg-muted/60 px-3 py-1.5 pr-12 shadow-xs">
+      <pre className="max-h-[400px] overflow-x-auto overflow-y-auto rounded-xl border border-border/70 bg-muted/60 px-3 py-1.5 pr-12 shadow-xs">
+        {language && (
+          <div className="mb-1 text-xs text-muted-foreground/70">
+            {language}
+          </div>
+        )}
         {children}
       </pre>
       <Tooltip>
@@ -261,6 +334,139 @@ function FileCard({
   );
 }
 
+function SyntaxHighlightedCode({
+  code,
+  language,
+  ...props
+}: {
+  code: string;
+  language: string;
+} & React.ComponentProps<"code">) {
+  const { themeName } = useTheme();
+  const [loadedKey, setLoadedKey] = React.useState(0);
+
+  React.useEffect(() => {
+    let cancelled = false;
+    async function loadAssets() {
+      try {
+        await ensureHighlighter();
+        if (!shikiHighlighter || cancelled) return;
+        let loaded = false;
+        if (!loadedLangs.has(language)) {
+          if (loadedLangs.size >= MAX_LOADED_LANGUAGES) return;
+          try {
+            await shikiHighlighter.loadLanguage(language as BundledLanguage);
+            loadedLangs.add(language);
+            loaded = true;
+          } catch {
+            return;
+          }
+        }
+        if (!loadedThemes.has(themeName as string)) {
+          try {
+            await shikiHighlighter.loadTheme(themeName as BundledTheme);
+            loadedThemes.add(themeName as string);
+            loaded = true;
+          } catch {
+            return;
+          }
+        }
+        if (loaded && !cancelled) setLoadedKey((k) => k + 1);
+      } catch {
+        /* ignore */
+      }
+    }
+    if (!loadedLangs.has(language) || !loadedThemes.has(themeName as string)) {
+      loadAssets();
+    }
+    return () => {
+      cancelled = true;
+    };
+  }, [language, themeName]);
+
+  // biome-ignore lint/correctness/useExhaustiveDependencies: loadedKey intentionally triggers re-memoization after async asset loading
+  const tokens = React.useMemo(() => {
+    if (
+      !shikiHighlighter ||
+      !loadedLangs.has(language) ||
+      !loadedThemes.has(themeName as string)
+    )
+      return null;
+    if ((code.match(/\n/g) || []).length > MAX_HIGHLIGHT_LINES) return null;
+    const cacheKey = `${language}:${themeName}:${code}`;
+    const cached = tokenCache.get(cacheKey);
+    if (cached) return cached;
+    try {
+      const result = shikiHighlighter.codeToTokens(code, {
+        lang: language as BundledLanguage,
+        theme: themeName as BundledTheme,
+      });
+      if (tokenCache.size >= MAX_CACHE_ENTRIES) {
+        const firstKey = tokenCache.keys().next().value;
+        if (firstKey !== undefined) tokenCache.delete(firstKey);
+      }
+      tokenCache.set(cacheKey, result.tokens);
+      return result.tokens;
+    } catch {
+      return null;
+    }
+  }, [code, language, themeName, loadedKey]);
+
+  const codeClassName = CODE_BLOCK_CLASS;
+
+  if (!tokens) {
+    const lines = code.split("\n");
+    return (
+      <code {...props} className={codeClassName}>
+        {lines.map((line, i) => (
+          // biome-ignore lint/suspicious/noArrayIndexKey: lines are positional
+          <span key={i} data-line="">
+            {line}
+          </span>
+        ))}
+      </code>
+    );
+  }
+
+  return (
+    <code {...props} className={codeClassName}>
+      {tokens.map((line, lineIdx) => {
+        const lineText = line.map((t) => t.content).join("");
+        const isAdd = DIFF_ADD_RE.test(lineText);
+        const isRemove = DIFF_REMOVE_RE.test(lineText);
+        const diffClass = isAdd
+          ? "code-line-diff-add"
+          : isRemove
+            ? "code-line-diff-remove"
+            : undefined;
+
+        const renderedTokens =
+          isAdd || isRemove
+            ? stripDiffMarker(line, isAdd ? DIFF_ADD_RE : DIFF_REMOVE_RE)
+            : line;
+
+        return (
+          <span
+            // biome-ignore lint/suspicious/noArrayIndexKey: tokens are positional and never reordered
+            key={lineIdx}
+            data-line=""
+            className={diffClass}
+          >
+            {renderedTokens.map((token, tokenIdx) => (
+              <span
+                // biome-ignore lint/suspicious/noArrayIndexKey: tokens are positional and never reordered
+                key={tokenIdx}
+                style={token.color ? { color: token.color } : undefined}
+              >
+                {token.content}
+              </span>
+            ))}
+          </span>
+        );
+      })}
+    </code>
+  );
+}
 function createMarkdownComponents(
   variant: MarkdownVariant,
   channels: Channel[],
@@ -356,15 +562,23 @@ function createMarkdownComponents(
         typeof className === "string" && className.includes("language-");
 
       if (isFencedCodeBlock || rawCode.endsWith("\n") || code.includes("\n")) {
+        const language = extractLanguage(className);
+
+        if (language) {
+          return (
+            <SyntaxHighlightedCode code={code} language={language} {...props} />
+          );
+        }
+
+        const lines = code.split("\n");
         return (
-          <code
-            {...props}
-            className={cn(
-              "block min-w-full whitespace-pre font-mono text-[13px] leading-6 text-foreground",
-              className,
-            )}
-          >
-            {code}
+          <code {...props} className={CODE_BLOCK_CLASS}>
+            {lines.map((line, i) => (
+              // biome-ignore lint/suspicious/noArrayIndexKey: lines are positional
+              <span key={i} data-line="">
+                {line}
+              </span>
+            ))}
           </code>
         );
       }
@@ -517,12 +731,21 @@ function createMarkdownComponents(
 
       return <p className={paragraphClassName}>{children}</p>;
     },
-    pre: ({ children }) =>
-      interactive ? (
-        <MarkdownCodeBlock>{children}</MarkdownCodeBlock>
-      ) : (
-        <span>{children}</span>
-      ),
+    pre: ({ children }) => {
+      if (!interactive) return <span>{children}</span>;
+      let language = "";
+      React.Children.forEach(children, (child) => {
+        if (
+          React.isValidElement<Record<string, unknown>>(child) &&
+          typeof child.props?.className === "string"
+        ) {
+          language = extractLanguage(child.props.className);
+        }
+      });
+      return (
+        <MarkdownCodeBlock language={language}>{children}</MarkdownCodeBlock>
+      );
+    },
     strong: ({ children }) => (
       <strong className="font-semibold">{children}</strong>
     ),
@@ -665,7 +888,8 @@ function MarkdownInner({
     : compact
       ? "compact"
       : "default";
-  const { channels } = useChannelNavigation();
+  const { channels: rawChannels } = useChannelNavigation();
+  const channels = useStableArray(rawChannels);
   const { goChannel } = useAppNavigation();
 
   const components = React.useMemo(
diff --git a/desktop/tests/e2e/messaging.spec.ts b/desktop/tests/e2e/messaging.spec.ts
index de6d6b7d9..9a6bae0d4 100644
--- a/desktop/tests/e2e/messaging.spec.ts
+++ b/desktop/tests/e2e/messaging.spec.ts
@@ -71,12 +71,12 @@ test("copy a rendered code block and paste it back as code", async ({
   await page.keyboard.press("ControlOrMeta+V");
   await page.getByTestId("send-message").click();
 
-  const copiedCodeBlock = page.locator("pre", { hasText: code });
-  await expect(copiedCodeBlock).toHaveCount(1);
+  const codeBlock = page.locator("[data-code-block]");
+  await expect(codeBlock).toHaveCount(1);
 
   const copyButton = page.getByLabel("Copy code block");
   await expect(copyButton).toHaveCSS("opacity", "0");
-  await copiedCodeBlock.hover();
+  await codeBlock.hover();
   await expect(copyButton).toHaveCSS("opacity", "1");
   await copyButton.click();
   await expect
@@ -87,7 +87,7 @@ test("copy a rendered code block and paste it back as code", async ({
   await page.keyboard.press("ControlOrMeta+V");
   await input.press("Enter");
 
-  await expect(copiedCodeBlock).toHaveCount(2);
+  await expect(codeBlock).toHaveCount(2);
 });
 
 test("pasting a long copied code block scrolls composer to cursor", async ({
@@ -115,7 +115,7 @@ test("pasting a long copied code block scrolls composer to cursor", async ({
   await page.keyboard.press("ControlOrMeta+V");
   await page.getByTestId("send-message").click();
 
-  const copiedCodeBlock = page.locator("pre", { hasText: longCode });
+  const copiedCodeBlock = page.locator("[data-code-block]");
   await expect(copiedCodeBlock).toHaveCount(1);
   await copiedCodeBlock.hover();
   await page.getByLabel("Copy code block").click();
@@ -134,6 +134,52 @@ test("pasting a long copied code block scrolls composer to cursor", async ({
     .toBeLessThanOrEqual(1);
 });
 
+test("code block shows language label when language is specified", async ({
+  page,
+}) => {
+  await page.context().grantPermissions(["clipboard-read", "clipboard-write"], {
+    origin: "http://127.0.0.1:4173",
+  });
+
+  await page.goto("/");
+  await page.getByTestId("channel-general").click();
+  await expect(page.getByTestId("chat-title")).toHaveText("general");
+
+  const input = page.getByTestId("message-input");
+  await page.evaluate(
+    (text) => navigator.clipboard.writeText(text),
+    "```typescript\nconst x = 1;\n```",
+  );
+
+  await input.click();
+  await page.keyboard.press("ControlOrMeta+V");
+  await page.getByTestId("send-message").click();
+
+  const codeBlock = page.locator("[data-code-block]");
+  await expect(codeBlock).toBeVisible();
+  await expect(codeBlock.getByText("typescript")).toBeVisible();
+});
+
+test("typing triple backticks and Enter creates a code block in composer", async ({
+  page,
+}) => {
+  await page.goto("/");
+  await page.getByTestId("channel-general").click();
+  await expect(page.getByTestId("chat-title")).toHaveText("general");
+
+  const input = page.getByTestId("message-input");
+  await input.click();
+  await page.keyboard.type("```");
+  await page.keyboard.press("Enter");
+
+  // A <pre> code block should appear inside the ProseMirror editor
+  const editorPre = input.locator("pre");
+  await expect(editorPre).toBeVisible();
+
+  // The literal backticks should be consumed (not visible as text)
+  await expect(input).not.toContainText("```");
+});
+
 test("message input clears after send", async ({ page }) => {
   const message = `Clear after send ${Date.now()}`;
   const input = page.getByTestId("message-input");
diff --git a/mobile/lib/features/channels/compose_bar.dart b/mobile/lib/features/channels/compose_bar.dart
index 24f57fe37..9f63bc2df 100644
--- a/mobile/lib/features/channels/compose_bar.dart
+++ b/mobile/lib/features/channels/compose_bar.dart
@@ -89,10 +89,12 @@ class ComposeBar extends HookConsumerWidget {
 
     // Typing indicator broadcast — throttled to one event per 3 seconds.
     final lastTypingSentMs = useRef(0);
+    final isModifyingText = useRef(false);
 
     // Detect @mention query and broadcast typing on text / selection change.
     useEffect(() {
       void listener() {
+        if (isModifyingText.value) return;
         final text = controller.text;
         final sel = controller.selection;
 
@@ -291,51 +293,27 @@ class ComposeBar extends HookConsumerWidget {
       final sel = controller.selection;
       if (!sel.isValid) return;
 
-      if (sel.isCollapsed) {
-        final offset = sel.baseOffset;
-        final updated =
-            '${text.substring(0, offset)}$prefix$suffix${text.substring(offset)}';
-        controller.text = updated;
-        controller.selection = TextSelection.collapsed(
-          offset: offset + prefix.length,
-        );
-      } else {
-        final selected = text.substring(sel.start, sel.end);
-        final updated =
-            '${text.substring(0, sel.start)}$prefix$selected$suffix${text.substring(sel.end)}';
-        controller.text = updated;
-        controller.selection = TextSelection.collapsed(
-          offset: sel.start + prefix.length + selected.length + suffix.length,
-        );
-      }
-      focusNode.requestFocus();
-    }
-
-    void applyCodeBlock() {
-      final text = controller.text;
-      final sel = controller.selection;
-      if (!sel.isValid) return;
-
-      if (sel.isCollapsed) {
-        final offset = sel.baseOffset;
-        const open = '```\n';
-        const close = '\n```';
-        final updated =
-            '${text.substring(0, offset)}$open$close${text.substring(offset)}';
-        controller.text = updated;
-        controller.selection = TextSelection.collapsed(
-          offset: offset + open.length,
-        );
-      } else {
-        final selected = text.substring(sel.start, sel.end);
-        const open = '```\n';
-        const close = '\n```';
-        final updated =
-            '${text.substring(0, sel.start)}$open$selected$close${text.substring(sel.end)}';
-        controller.text = updated;
-        controller.selection = TextSelection.collapsed(
-          offset: sel.start + open.length + selected.length + close.length,
-        );
+      isModifyingText.value = true;
+      try {
+        if (sel.isCollapsed) {
+          final offset = sel.baseOffset;
+          final updated =
+              '${text.substring(0, offset)}$prefix$suffix${text.substring(offset)}';
+          controller.text = updated;
+          controller.selection = TextSelection.collapsed(
+            offset: offset + prefix.length,
+          );
+        } else {
+          final selected = text.substring(sel.start, sel.end);
+          final updated =
+              '${text.substring(0, sel.start)}$prefix$selected$suffix${text.substring(sel.end)}';
+          controller.text = updated;
+          controller.selection = TextSelection.collapsed(
+            offset: sel.start + prefix.length + selected.length + suffix.length,
+          );
+        }
+      } finally {
+        isModifyingText.value = false;
       }
       focusNode.requestFocus();
     }
@@ -394,10 +372,7 @@ class ComposeBar extends HookConsumerWidget {
             children: [
               // Formatting toolbar (toggled via Aa button).
               if (showFormatting.value)
-                _FormattingToolbar(
-                  onFormat: applyFormat,
-                  onCodeBlock: applyCodeBlock,
-                ),
+                _FormattingToolbar(onFormat: applyFormat),
 
               if (hasAttachments || hasPendingUploads) ...[
                 _AttachmentStrip(
@@ -852,9 +827,8 @@ class _ChannelSuggestions extends StatelessWidget {
 
 class _FormattingToolbar extends StatelessWidget {
   final void Function(String prefix, [String? suffix]) onFormat;
-  final VoidCallback onCodeBlock;
 
-  const _FormattingToolbar({required this.onFormat, required this.onCodeBlock});
+  const _FormattingToolbar({required this.onFormat});
 
   @override
   Widget build(BuildContext context) {
@@ -885,7 +859,7 @@ class _FormattingToolbar extends StatelessWidget {
           _FormatButton(
             icon: LucideIcons.squareCode,
             tooltip: 'Code block',
-            onTap: onCodeBlock,
+            onTap: () => onFormat('```\n', '\n```'),
           ),
         ],
       ),
diff --git a/mobile/lib/features/channels/message_content.dart b/mobile/lib/features/channels/message_content.dart
index 57d1cf2ac..a6156e1d7 100644
--- a/mobile/lib/features/channels/message_content.dart
+++ b/mobile/lib/features/channels/message_content.dart
@@ -1,11 +1,14 @@
 import 'dart:math' as math;
 
 import 'package:flutter/material.dart';
+import 'package:flutter_hooks/flutter_hooks.dart';
 import 'package:gpt_markdown/gpt_markdown.dart';
 import 'package:gpt_markdown/custom_widgets/markdown_config.dart';
 import 'package:lucide_icons_flutter/lucide_icons.dart';
 import 'package:url_launcher/url_launcher.dart';
 
+import '../../shared/clipboard_utils.dart';
+import '../../shared/syntax_highlight.dart';
 import '../../shared/theme/theme.dart';
 import 'media_viewer_page.dart';
 import 'message_media.dart';
@@ -15,7 +18,7 @@ const _messageMediaMaxImageHeight = 240.0;
 
 /// Renders message content with markdown formatting, @mentions, #channel links,
 /// and media-aware markdown images/videos.
-class MessageContent extends StatelessWidget {
+class MessageContent extends HookWidget {
   final String content;
 
   /// Display names for mentioned pubkeys, extracted from event p-tags.
@@ -51,75 +54,80 @@ class MessageContent extends StatelessWidget {
         context.textTheme.bodyMedium?.copyWith(color: context.colors.onSurface);
     final imetaByUrl = parseImetaTags(tags);
 
-    // Convert autolinks and bare URLs to standard markdown links,
-    // but skip content inside backticks (inline code / fenced blocks).
-    final buffer = StringBuffer();
-    final parts = content.split('`');
-    for (var i = 0; i < parts.length; i++) {
-      if (i.isOdd) {
-        // Inside backticks — preserve as-is.
-        buffer.write('`${parts[i]}`');
-      } else {
-        // 1. Angle-bracket autolinks: <https://...>
-        var segment = parts[i].replaceAllMapped(
-          RegExp(r'<(https?://[^>]+)>'),
-          (m) => '[${m[1]}](${m[1]})',
-        );
-        // 2. Bare URLs not already inside markdown link/image syntax.
-        //    Negative lookbehind avoids matching URLs preceded by ]( or =
-        //    which are already part of markdown links or imeta tags.
-        segment = segment.replaceAllMapped(
-          RegExp(r'(?<![(\]=])https?://[^\s)>\]]+'),
-          (m) {
-            final url = m[0]!;
-            // Skip if this URL is already a markdown link label that equals
-            // the URL (produced by step 1 or authored as [url](url)).
-            final start = m.start;
-            if (start >= 1 && segment[start - 1] == '[') return url;
-            return '[$url]($url)';
-          },
-        );
-        buffer.write(segment);
+    final finalContent = useMemoized(() {
+      // Convert autolinks and bare URLs to standard markdown links,
+      // but skip content inside backticks (inline code / fenced blocks).
+      final buffer = StringBuffer();
+      final parts = content.split('`');
+      for (var i = 0; i < parts.length; i++) {
+        if (i.isOdd) {
+          // Inside backticks — preserve as-is.
+          buffer.write('`${parts[i]}`');
+        } else {
+          // 1. Angle-bracket autolinks: <https://...>
+          var segment = parts[i].replaceAllMapped(
+            RegExp(r'<(https?://[^>]+)>'),
+            (m) => '[${m[1]}](${m[1]})',
+          );
+          // 2. Bare URLs not already inside markdown link/image syntax.
+          //    Negative lookbehind avoids matching URLs preceded by ]( or =
+          //    which are already part of markdown links or imeta tags.
+          segment = segment.replaceAllMapped(
+            RegExp(r'(?<![(\]=])https?://[^\s)>\]]+'),
+            (m) {
+              final url = m[0]!;
+              // Skip if this URL is already a markdown link label that equals
+              // the URL (produced by step 1 or authored as [url](url)).
+              final start = m.start;
+              if (start >= 1 && segment[start - 1] == '[') return url;
+              return '[$url]($url)';
+            },
+          );
+          buffer.write(segment);
+        }
       }
-    }
-    final processed = buffer.toString();
-
-    // Replace spaces with non-breaking spaces inside known mention names
-    // so the gpt_markdown combined regex can match multi-word names
-    // even when caseSensitive is not preserved.
-    // Skip content inside backticks to avoid altering inline code.
-    final mentionParts = processed.split('`');
-    final mentionBuf = StringBuffer();
-    for (var i = 0; i < mentionParts.length; i++) {
-      if (i.isOdd) {
-        mentionBuf.write('`${mentionParts[i]}`');
-      } else {
-        var segment = mentionParts[i];
-        for (final name in mentionNames.values) {
-          if (name.contains(' ')) {
-            final nbspName = name.replaceAll(' ', '\u00A0');
-            segment = segment.replaceAllMapped(
-              RegExp('@${RegExp.escape(name)}', caseSensitive: false),
-              (m) => '@$nbspName',
-            );
+      final processed = buffer.toString();
+
+      // Replace spaces with non-breaking spaces inside known mention names
+      // so the gpt_markdown combined regex can match multi-word names
+      // even when caseSensitive is not preserved.
+      // Skip content inside backticks to avoid altering inline code.
+      final mentionParts = processed.split('`');
+      final mentionBuf = StringBuffer();
+      for (var i = 0; i < mentionParts.length; i++) {
+        if (i.isOdd) {
+          mentionBuf.write('`${mentionParts[i]}`');
+        } else {
+          var segment = mentionParts[i];
+          for (final name in mentionNames.values) {
+            if (name.contains(' ')) {
+              final nbspName = name.replaceAll(' ', '\u00A0');
+              segment = segment.replaceAllMapped(
+                RegExp('@${RegExp.escape(name)}', caseSensitive: false),
+                (m) => '@$nbspName',
+              );
+            }
           }
+          mentionBuf.write(segment);
         }
-        mentionBuf.write(segment);
       }
-    }
-    final mentionProcessed = mentionBuf.toString();
+      final mentionProcessed = mentionBuf.toString();
 
-    // Ensure channel links at the very start of content don't get
-    // swallowed by markdown processing.
-    var finalContent = mentionProcessed;
-    if (RegExp(r'^#[A-Za-z0-9_]').hasMatch(finalContent)) {
-      finalContent = '\u200B$finalContent';
-    }
+      // Ensure channel links at the very start of content don't get
+      // swallowed by markdown processing.
+      var result = mentionProcessed;
+      if (RegExp(r'^#[A-Za-z0-9_]').hasMatch(result)) {
+        result = '\u200B$result';
+      }
+      return result;
+    }, [content, mentionNames]);
 
     return GptMarkdown(
       finalContent,
       style: style,
       followLinkColor: false,
+      codeBuilder: (context, name, code, closed) =>
+          _MessageCodeBlock(name: name, code: code),
       linkBuilder: (context, linkText, url, linkStyle) =>
           _buildLink(context, linkText, url, linkStyle, style),
       imageBuilder: (context, imageUrl) =>
@@ -443,6 +451,111 @@ class _MediaPreviewFallback extends StatelessWidget {
   }
 }
 
+class _MessageCodeBlock extends HookWidget {
+  final String name;
+  final String code;
+
+  const _MessageCodeBlock({required this.name, required this.code});
+
+  @override
+  Widget build(BuildContext context) {
+    final isCopied = useState(false);
+
+    Future<void> handleCopy() async {
+      await copyToClipboard(context, code, message: 'Copied code to clipboard');
+      if (!context.mounted) return;
+      isCopied.value = true;
+      Future.delayed(const Duration(seconds: 2), () {
+        if (context.mounted) isCopied.value = false;
+      });
+    }
+
+    final codeBaseStyle = TextStyle(
+      fontFamily: 'GeistMono',
+      fontSize: 13,
+      height: 1.5,
+      color: context.colors.onSurface,
+    );
+    final isDark = context.theme.brightness == Brightness.dark;
+    final codeTheme = isDark ? highlightDarkTheme : highlightLightTheme;
+    final codeSpans = useMemoized(
+      () => highlightCode(code, name, codeTheme, codeBaseStyle),
+      [code, name, isDark],
+    );
+    return Container(
+      margin: const EdgeInsets.only(top: Grid.half),
+      decoration: BoxDecoration(
+        color: context.colors.surfaceContainerHighest.withValues(alpha: 0.6),
+        borderRadius: BorderRadius.circular(12),
+        border: Border.all(
+          color: context.colors.outline.withValues(alpha: 0.7),
+        ),
+      ),
+      child: Column(
+        crossAxisAlignment: CrossAxisAlignment.stretch,
+        mainAxisSize: MainAxisSize.min,
+        children: [
+          if (name.isNotEmpty)
+            Padding(
+              padding: const EdgeInsets.only(
+                left: Grid.twelve,
+                top: Grid.half + Grid.quarter,
+              ),
+              child: Text(
+                name,
+                style: context.textTheme.labelSmall?.copyWith(
+                  color: context.colors.onSurfaceVariant,
+                ),
+              ),
+            ),
+          Stack(
+            children: [
+              Padding(
+                padding: EdgeInsets.fromLTRB(
+                  Grid.twelve,
+                  name.isEmpty ? Grid.half + Grid.quarter : Grid.quarter,
+                  44,
+                  Grid.half + Grid.quarter,
+                ),
+                child: SingleChildScrollView(
+                  scrollDirection: Axis.horizontal,
+                  child: RichText(
+                    softWrap: false,
+                    text: TextSpan(style: codeBaseStyle, children: codeSpans),
+                  ),
+                ),
+              ),
+              Positioned(
+                top: 0,
+                right: Grid.quarter,
+                child: SizedBox(
+                  width: 28,
+                  height: 28,
+                  child: IconButton(
+                    onPressed: handleCopy,
+                    padding: EdgeInsets.zero,
+                    visualDensity: VisualDensity.compact,
+                    style: IconButton.styleFrom(
+                      tapTargetSize: MaterialTapTargetSize.shrinkWrap,
+                    ),
+                    icon: Icon(
+                      isCopied.value ? LucideIcons.check : LucideIcons.copy,
+                      size: 14,
+                      color: isCopied.value
+                          ? context.colors.primary
+                          : context.colors.onSurfaceVariant,
+                    ),
+                  ),
+                ),
+              ),
+            ],
+          ),
+        ],
+      ),
+    );
+  }
+}
+
 class _MentionMd extends InlineMd {
   final Map<String, String> mentionNames;
   late final RegExp _exp = _buildPrefixPattern(
diff --git a/mobile/lib/features/profile/user_profile_sheet.dart b/mobile/lib/features/profile/user_profile_sheet.dart
index 27fe5cc27..da9818d50 100644
--- a/mobile/lib/features/profile/user_profile_sheet.dart
+++ b/mobile/lib/features/profile/user_profile_sheet.dart
@@ -1,9 +1,9 @@
 import 'package:flutter/material.dart';
-import 'package:flutter/services.dart';
 import 'package:flutter_hooks/flutter_hooks.dart';
 import 'package:hooks_riverpod/hooks_riverpod.dart';
 import 'package:lucide_icons_flutter/lucide_icons.dart';
 
+import '../../shared/clipboard_utils.dart';
 import '../../shared/relay/relay.dart';
 import '../../shared/theme/theme.dart';
 import '../../shared/utils/string_utils.dart';
@@ -173,13 +173,11 @@ class UserProfileSheet extends HookConsumerWidget {
                     color: context.colors.onSurfaceVariant,
                     fontFamily: 'monospace',
                   ),
-                  onTap: () {
-                    Clipboard.setData(ClipboardData(text: pubkey));
-                    ScaffoldMessenger.of(context).showSnackBar(
-                      const SnackBar(
-                        content: Text('Public key copied'),
-                        duration: Duration(seconds: 2),
-                      ),
+                  onTap: () async {
+                    await copyToClipboard(
+                      context,
+                      pubkey,
+                      message: 'Public key copied',
                     );
                   },
                 ),
diff --git a/mobile/lib/features/pulse/note_card.dart b/mobile/lib/features/pulse/note_card.dart
index ea8bd6c8f..0ee093070 100644
--- a/mobile/lib/features/pulse/note_card.dart
+++ b/mobile/lib/features/pulse/note_card.dart
@@ -1,10 +1,10 @@
 import 'package:flutter/material.dart';
-import 'package:flutter/services.dart';
 import 'package:flutter_hooks/flutter_hooks.dart';
 import 'package:hooks_riverpod/hooks_riverpod.dart';
 import 'package:lucide_icons_flutter/lucide_icons.dart';
 import 'package:nostr/nostr.dart' as nostr;
 
+import '../../shared/clipboard_utils.dart';
 import '../../shared/theme/theme.dart';
 import '../channels/channel_detail_page.dart';
 import '../channels/channel_management_provider.dart';
@@ -182,10 +182,11 @@ class NoteCard extends HookConsumerWidget {
                     ),
                     _ActionButton(
                       icon: LucideIcons.share,
-                      onTap: () {
-                        Clipboard.setData(ClipboardData(text: _shareUri(note)));
-                        ScaffoldMessenger.of(context).showSnackBar(
-                          const SnackBar(content: Text('Copied note URI')),
+                      onTap: () async {
+                        await copyToClipboard(
+                          context,
+                          _shareUri(note),
+                          message: 'Copied note URI',
                         );
                       },
                     ),
diff --git a/mobile/lib/features/settings/settings_page.dart b/mobile/lib/features/settings/settings_page.dart
index 4f0ed942a..cbc426e03 100644
--- a/mobile/lib/features/settings/settings_page.dart
+++ b/mobile/lib/features/settings/settings_page.dart
@@ -1,5 +1,4 @@
 import 'package:flutter/material.dart';
-import 'package:flutter/services.dart';
 import 'package:flutter_hooks/flutter_hooks.dart';
 import 'package:hooks_riverpod/hooks_riverpod.dart';
 import 'package:lucide_icons_flutter/lucide_icons.dart';
@@ -7,6 +6,7 @@ import 'package:nostr/nostr.dart' as nostr;
 import 'package:package_info_plus/package_info_plus.dart';
 
 import '../../shared/auth/auth.dart';
+import '../../shared/clipboard_utils.dart';
 import '../../shared/relay/relay.dart';
 import '../../shared/theme/theme.dart';
 import '../../shared/widgets/frosted_app_bar.dart';
@@ -76,13 +76,11 @@ class SettingsPage extends HookConsumerWidget {
                   ),
                   trailing: IconButton(
                     icon: const Icon(LucideIcons.copy, size: 16),
-                    onPressed: () {
-                      Clipboard.setData(ClipboardData(text: pubkey));
-                      ScaffoldMessenger.of(context).showSnackBar(
-                        const SnackBar(
-                          content: Text('Pubkey copied'),
-                          duration: Duration(seconds: 2),
-                        ),
+                    onPressed: () async {
+                      await copyToClipboard(
+                        context,
+                        pubkey,
+                        message: 'Pubkey copied',
                       );
                     },
                   ),
diff --git a/mobile/lib/shared/clipboard_utils.dart b/mobile/lib/shared/clipboard_utils.dart
new file mode 100644
index 000000000..d08ab9506
--- /dev/null
+++ b/mobile/lib/shared/clipboard_utils.dart
@@ -0,0 +1,14 @@
+import 'package:flutter/material.dart';
+import 'package:flutter/services.dart';
+
+Future<void> copyToClipboard(
+  BuildContext context,
+  String text, {
+  String message = 'Copied to clipboard',
+}) async {
+  await Clipboard.setData(ClipboardData(text: text));
+  if (!context.mounted) return;
+  ScaffoldMessenger.of(context).showSnackBar(
+    SnackBar(content: Text(message), duration: const Duration(seconds: 2)),
+  );
+}
diff --git a/mobile/lib/shared/syntax_highlight.dart b/mobile/lib/shared/syntax_highlight.dart
new file mode 100644
index 000000000..60e47cc16
--- /dev/null
+++ b/mobile/lib/shared/syntax_highlight.dart
@@ -0,0 +1,107 @@
+import 'package:flutter/material.dart';
+import 'package:highlight/highlight.dart' show highlight, Node;
+
+const highlightLightTheme = <String, TextStyle>{
+  'keyword': TextStyle(color: Color(0xFFa626a4)),
+  'built_in': TextStyle(color: Color(0xFF0184bc)),
+  'type': TextStyle(color: Color(0xFF0184bc)),
+  'literal': TextStyle(color: Color(0xFF0184bc)),
+  'number': TextStyle(color: Color(0xFF986801)),
+  'string': TextStyle(color: Color(0xFF50a14f)),
+  'symbol': TextStyle(color: Color(0xFF50a14f)),
+  'comment': TextStyle(color: Color(0xFFa0a1a7), fontStyle: FontStyle.italic),
+  'doctag': TextStyle(color: Color(0xFFa0a1a7), fontStyle: FontStyle.italic),
+  'meta': TextStyle(color: Color(0xFF986801)),
+  'attr': TextStyle(color: Color(0xFF986801)),
+  'attribute': TextStyle(color: Color(0xFF986801)),
+  'title': TextStyle(color: Color(0xFF4078f2)),
+  'title.class_': TextStyle(color: Color(0xFFc18401)),
+  'title.function_': TextStyle(color: Color(0xFF4078f2)),
+  'name': TextStyle(color: Color(0xFFe45649)),
+  'tag': TextStyle(color: Color(0xFFe45649)),
+  'selector-tag': TextStyle(color: Color(0xFFe45649)),
+  'params': TextStyle(color: Color(0xFF383a42)),
+  'variable': TextStyle(color: Color(0xFFe45649)),
+  'subst': TextStyle(color: Color(0xFFe45649)),
+  'section': TextStyle(color: Color(0xFF4078f2)),
+  'bullet': TextStyle(color: Color(0xFF4078f2)),
+  'link': TextStyle(color: Color(0xFF4078f2)),
+  'addition': TextStyle(color: Color(0xFF50a14f)),
+  'deletion': TextStyle(color: Color(0xFFe45649)),
+};
+
+const highlightDarkTheme = <String, TextStyle>{
+  'keyword': TextStyle(color: Color(0xFFc678dd)),
+  'built_in': TextStyle(color: Color(0xFF56b6c2)),
+  'type': TextStyle(color: Color(0xFF56b6c2)),
+  'literal': TextStyle(color: Color(0xFF56b6c2)),
+  'number': TextStyle(color: Color(0xFFd19a66)),
+  'string': TextStyle(color: Color(0xFF98c379)),
+  'symbol': TextStyle(color: Color(0xFF98c379)),
+  'comment': TextStyle(color: Color(0xFF5c6370), fontStyle: FontStyle.italic),
+  'doctag': TextStyle(color: Color(0xFF5c6370), fontStyle: FontStyle.italic),
+  'meta': TextStyle(color: Color(0xFFd19a66)),
+  'attr': TextStyle(color: Color(0xFFd19a66)),
+  'attribute': TextStyle(color: Color(0xFFd19a66)),
+  'title': TextStyle(color: Color(0xFF61afef)),
+  'title.class_': TextStyle(color: Color(0xFFe5c07b)),
+  'title.function_': TextStyle(color: Color(0xFF61afef)),
+  'name': TextStyle(color: Color(0xFFe06c75)),
+  'tag': TextStyle(color: Color(0xFFe06c75)),
+  'selector-tag': TextStyle(color: Color(0xFFe06c75)),
+  'params': TextStyle(color: Color(0xFFabb2bf)),
+  'variable': TextStyle(color: Color(0xFFe06c75)),
+  'subst': TextStyle(color: Color(0xFFe06c75)),
+  'section': TextStyle(color: Color(0xFF61afef)),
+  'bullet': TextStyle(color: Color(0xFF61afef)),
+  'link': TextStyle(color: Color(0xFF61afef)),
+  'addition': TextStyle(color: Color(0xFF98c379)),
+  'deletion': TextStyle(color: Color(0xFFe06c75)),
+};
+
+List<InlineSpan> highlightCode(
+  String code,
+  String language,
+  Map<String, TextStyle> theme,
+  TextStyle baseStyle,
+) {
+  try {
+    if (language.isEmpty) return [TextSpan(text: code, style: baseStyle)];
+    final result = highlight.parse(code, language: language);
+    if (result.nodes == null) return [TextSpan(text: code, style: baseStyle)];
+    return buildSpans(result.nodes!, theme, baseStyle);
+  } catch (_) {
+    return [TextSpan(text: code, style: baseStyle)];
+  }
+}
+
+List<InlineSpan> buildSpans(
+  List<Node> nodes,
+  Map<String, TextStyle> theme,
+  TextStyle baseStyle, {
+  int maxDepth = 10,
+}) {
+  final spans = <InlineSpan>[];
+  for (final node in nodes) {
+    if (maxDepth <= 0) {
+      if (node.value != null) {
+        spans.add(TextSpan(text: node.value, style: baseStyle));
+      }
+      continue;
+    }
+    if (node.children != null && node.children!.isNotEmpty) {
+      final childStyle = node.className != null
+          ? baseStyle.merge(theme[node.className])
+          : baseStyle;
+      spans.addAll(
+        buildSpans(node.children!, theme, childStyle, maxDepth: maxDepth - 1),
+      );
+    } else if (node.value != null) {
+      final style = node.className != null
+          ? baseStyle.merge(theme[node.className])
+          : baseStyle;
+      spans.add(TextSpan(text: node.value, style: style));
+    }
+  }
+  return spans;
+}
diff --git a/mobile/pubspec.lock b/mobile/pubspec.lock
index 8569de00e..b81f20083 100644
--- a/mobile/pubspec.lock
+++ b/mobile/pubspec.lock
@@ -472,6 +472,14 @@ packages:
       url: "https://pub.dev"
     source: hosted
     version: "1.1.6"
+  highlight:
+    dependency: "direct main"
+    description:
+      name: highlight
+      sha256: "5353a83ffe3e3eca7df0abfb72dcf3fa66cc56b953728e7113ad4ad88497cf21"
+      url: "https://pub.dev"
+    source: hosted
+    version: "0.7.0"
   hooks:
     dependency: transitive
     description:
diff --git a/mobile/pubspec.yaml b/mobile/pubspec.yaml
index 8c6b78193..e76010ed2 100644
--- a/mobile/pubspec.yaml
+++ b/mobile/pubspec.yaml
@@ -22,6 +22,7 @@ dependencies:
   pointycastle: ^4.0.0
   url_launcher: ^6.3.2
   gpt_markdown: ^1.1.6
+  highlight: ^0.7.0
   intl: ^0.20.2
   uuid: ^4.5.1
   image_picker: ^1.1.2
diff --git a/mobile/test/features/channels/message_content_test.dart b/mobile/test/features/channels/message_content_test.dart
index 4f8a3a058..c2e12d9ab 100644
--- a/mobile/test/features/channels/message_content_test.dart
+++ b/mobile/test/features/channels/message_content_test.dart
@@ -254,6 +254,7 @@ void main() {
         );
 
         expect(_findRich('void main() {}'), findsWidgets);
+        expect(find.text('dart'), findsOneWidget);
       });
     });