diff --git a/src/channels/chat-sdk-bridge-byline.test.ts b/src/channels/chat-sdk-bridge-byline.test.ts
new file mode 100644
index 000000000..28bbcdcad
--- /dev/null
+++ b/src/channels/chat-sdk-bridge-byline.test.ts
@@ -0,0 +1,112 @@
+/**
+ * Approval-card actor byline in the Chat SDK bridge.
+ *
+ * Drives the bridge's real onAction handler through the real Chat SDK
+ * dispatch (`chat.processAction`): `bridge.setup()` registers the handler on
+ * a real Chat instance, which the test captures from the webhook-server
+ * registration (mocked so no HTTP server binds a port). After a button click
+ * the bridge edits the card; the edit must append " — <actor>" so shared
+ * channels see who resolved an approval. Goes red if the byLine concatenation
+ * is removed from the edited markdown.
+ */
+import { afterEach, beforeEach, describe, expect, it, vi } from 'vitest';
+
+import type { Adapter, Chat } from 'chat';
+
+const captured = vi.hoisted(() => ({ chat: null as unknown }));
+
+vi.mock('../webhook-server.js', () => ({
+  registerWebhookAdapter: vi.fn((chat: unknown) => {
+    captured.chat = chat;
+  }),
+}));
+
+import { closeDb, initTestDb, runMigrations } from '../db/index.js';
+import type { ChannelSetup } from './adapter.js';
+import { createChatSdkBridge } from './chat-sdk-bridge.js';
+
+interface CapturedEdit {
+  threadId: string;
+  messageId: string;
+  markdown: string;
+}
+
+function makeAdapter(edits: CapturedEdit[]): Adapter {
+  return {
+    name: 'stub',
+    initialize: async () => {},
+    channelIdFromThreadId: (threadId: string) => `stub:${threadId}`,
+    editMessage: async (threadId: string, messageId: string, content: { markdown: string }) => {
+      edits.push({ threadId, messageId, markdown: content.markdown });
+    },
+  } as unknown as Adapter;
+}
+
+async function fireAction(user: Record<string, unknown>): Promise<{ edits: CapturedEdit[]; actions: string[] }> {
+  const edits: CapturedEdit[] = [];
+  const actions: string[] = [];
+  const adapter = makeAdapter(edits);
+  const bridge = createChatSdkBridge({ adapter, supportsThreads: false });
+
+  await bridge.setup({
+    onInbound: async () => {},
+    onInboundEvent: async () => {},
+    onMetadata: () => {},
+    onAction: (questionId: string, selectedOption: string, userId: string) => {
+      actions.push(`${questionId}:${selectedOption}:${userId}`);
+    },
+  } as ChannelSetup);
+
+  const chat = captured.chat as Chat;
+  expect(chat).toBeTruthy();
+  await chat.processAction(
+    {
+      actionId: 'ncq:q-1:approve',
+      adapter,
+      messageId: 'msg-1',
+      raw: {},
+      threadId: 'T-1',
+      user: user as never,
+      value: 'approve',
+    },
+    undefined,
+  );
+  return { edits, actions };
+}
+
+beforeEach(() => {
+  captured.chat = null;
+  const db = initTestDb();
+  runMigrations(db);
+});
+
+afterEach(() => {
+  closeDb();
+});
+
+describe('chat-sdk-bridge approval-card byline', () => {
+  it('appends the acting user to the edited card markdown', async () => {
+    const { edits, actions } = await fireAction({ userId: 'U1', userName: 'gavriel', fullName: 'Gavriel C' });
+
+    expect(edits).toHaveLength(1);
+    expect(edits[0].threadId).toBe('T-1');
+    expect(edits[0].messageId).toBe('msg-1');
+    expect(edits[0].markdown).toContain('approve — gavriel');
+    expect(actions).toEqual(['q-1:approve:U1']);
+  });
+
+  it('falls back to fullName when userName is missing', async () => {
+    const { edits } = await fireAction({ userId: 'U2', fullName: 'Gavriel C' });
+
+    expect(edits).toHaveLength(1);
+    expect(edits[0].markdown).toContain('— Gavriel C');
+  });
+
+  it('omits the byline when the actor has no name', async () => {
+    const { edits } = await fireAction({ userId: 'U3' });
+
+    expect(edits).toHaveLength(1);
+    expect(edits[0].markdown).not.toContain('—');
+    expect(edits[0].markdown).toContain('approve');
+  });
+});
diff --git a/src/channels/chat-sdk-bridge.ts b/src/channels/chat-sdk-bridge.ts
index efeb32f16..64071d35e 100644
--- a/src/channels/chat-sdk-bridge.ts
+++ b/src/channels/chat-sdk-bridge.ts
@@ -284,11 +284,13 @@ export function createChatSdkBridge(config: ChatSdkBridgeConfig): ChannelAdapter
         const matched = render?.options.find((o) => o.value === selectedOption);
         const selectedLabel = matched?.selectedLabel ?? selectedOption ?? '(clicked)';
 
-        // Update the card to show the selected answer and remove buttons
+        // Update the card to show the selected answer, who acted, and remove buttons
+        const actorName = event.user?.userName || event.user?.fullName || '';
+        const byLine = actorName ? ` — ${actorName}` : '';
         try {
           const tid = event.threadId;
           await adapter.editMessage(tid, event.messageId, {
-            markdown: `${title}\n\n${selectedLabel}`,
+            markdown: `${title}\n\n${selectedLabel}${byLine}`,
           });
         } catch (err) {
           log.warn('Failed to update card after action', { err });