Add /copy to copy the last assistant reply (#493)

src/components/ThreadView.tsx

@@ -1053,8 +1053,8 @@ export const ThreadView = memo(function ThreadView({
   );
   /** Bumps after a successful push so the sync pill refetches. */
   const [syncRefreshNonce, setSyncRefreshNonce] = useState(0);
-  /** Brief inline confirmation after copying the thread id. */
-  const [copied, setCopied] = useState<"id" | "link" | null>(null);
+  /** Brief inline confirmation after copying the thread id or `/copy`. */
+  const [copied, setCopied] = useState<"id" | "link" | "reply" | null>(null);
   /** Header quick action currently in flight (issue #153). */
   const [commandRunningId, setCommandRunningId] = useState<string | null>(null);
   const [commandError, setCommandError] = useState<string | null>(null);
@@ -1706,8 +1706,39 @@ export const ThreadView = memo(function ThreadView({
     onNewThread?.();
   }, [isWorking, onSettleThread, onNewThread]);
 
+  const flashCopied = useCallback((what: "id" | "link" | "reply") => {
+    setCopied(what);
+    if (copyFlashTimer.current != null) {
+      clearTimeout(copyFlashTimer.current);
+    }
+    copyFlashTimer.current = setTimeout(() => {
+      setCopied(null);
+      copyFlashTimer.current = null;
+    }, COPY_FLASH_MS);
+  }, []);
+
+  // `/copy` (#493): the latest finished assistant reply, as Markdown source.
+  // A still-streaming reply is skipped; no reply at all is a no-op.
+  const handleCopyLastReply = useCallback(() => {
+    const reply = [...(detail?.messages ?? [])].reverse().find(
+      (m) =>
+        m.role === "assistant" &&
+        !m.thinking &&
+        m.id !== streamingMessageId &&
+        m.text.trim() !== "",
+    );
+    if (!reply) return;
+    void navigator.clipboard
+      ?.writeText(reply.text)
+      .then(() => flashCopied("reply"), () => {});
+  }, [detail?.messages, streamingMessageId, flashCopied]);
+
   const handleSlashAction = useCallback(
     (action: SlashAction) => {
+      if (action === "copy") {
+        handleCopyLastReply();
+        return;
+      }
       if (action === "usage") {
         setContextOpen(false);
         setQuotaOpen(true);
@@ -1743,6 +1774,7 @@ export const ThreadView = memo(function ThreadView({
       }
     },
     [
+      handleCopyLastReply,
       ring,
       handleCompact,
       handleForkFresh,
@@ -2654,14 +2686,7 @@ export const ThreadView = memo(function ThreadView({
     } catch {
       return;
     }
-    setCopied(what);
-    if (copyFlashTimer.current != null) {
-      clearTimeout(copyFlashTimer.current);
-    }
-    copyFlashTimer.current = setTimeout(() => {
-      setCopied(null);
-      copyFlashTimer.current = null;
-    }, COPY_FLASH_MS);
+    flashCopied(what);
   };
 
   const hasVersionControl =
@@ -2746,7 +2771,11 @@ export const ThreadView = memo(function ThreadView({
   });
   // Run status rides on the composer's top edge (#1429), not the transcript.
   const composerStatus =
-    detail.thread.status === "quota-wait" ? (
+    copied === "reply" ? (
+      <div className={styles.statusStrip} data-copied-reply="" role="status">
+        <span className={styles.statusText}>Copied last reply</span>
+      </div>
+    ) : detail.thread.status === "quota-wait" ? (
       <div
         className={`${styles.statusStrip} ${styles.statusStripQuotaWait}`}
         data-quota-wait-strip=""

src/slashCommands.ts

@@ -14,6 +14,7 @@ export const NATIVE_COMPACT_PROVIDERS: readonly string[] = ["claude", "codex"];
 
 /** Immediate actions the palette can fire. Insert verbs have no action. */
 export type SlashAction =
+  | "copy"
   | "compact"
   | "rewind"
   | "usage"
@@ -79,6 +80,12 @@ export const SLASH_COMMANDS: readonly SlashCommand[] = [
     kind: "run",
     action: "context",
   },
+  {
+    name: "/copy",
+    hint: "Copy the last reply as Markdown",
+    kind: "run",
+    action: "copy",
+  },
   {
     name: "/model",
     hint: "Pick provider and model",

test/composerSlashActions.test.tsx

@@ -513,6 +513,60 @@ describe("ThreadView / palette actions", () => {
     assert.equal(opened, 1);
   });
 
+  describe("copy (#493)", () => {
+    let copied: string[] = [];
+    const stubClipboard = () => {
+      copied = [];
+      Object.defineProperty(navigator, "clipboard", {
+        value: {
+          writeText: async (text: string) => {
+            copied.push(text);
+          },
+        },
+        configurable: true,
+      });
+    };
+    const twoTurns = () =>
+      detail({
+        messages: [
+          msg({ id: "u1", role: "user", text: "first", createdAt: 1 }),
+          msg({ id: "a1", role: "assistant", text: "older **reply**", createdAt: 2 }),
+          msg({ id: "u2", role: "user", text: "second", createdAt: 3 }),
+          msg({ id: "a2", role: "assistant", text: "latest reply", createdAt: 4 }),
+          msg({ id: "t1", role: "tool", text: "ran ls", createdAt: 5 }),
+        ],
+      });
+
+    it("/copy copies the latest assistant reply and flashes", async () => {
+      stubClipboard();
+      const m = await mountView({ detail: twoTurns() });
+      await acceptSlash(m, "/copy");
+      await m.flush();
+      assert.deepEqual(copied, ["latest reply"]);
+      assert.match(m.query("[data-copied-reply]")?.textContent ?? "", /Copied last reply/);
+      assert.equal(textarea(m).value, "", "token cleared");
+    });
+
+    it("the per-message button copies that older turn's Markdown", async () => {
+      stubClipboard();
+      const m = await mountView({ detail: twoTurns() });
+      const btn = m.query('[data-msg="a1"] [data-msg-copy]');
+      assert.ok(btn, "copy button on the older reply");
+      await m.click(btn as HTMLElement);
+      await m.flush();
+      assert.deepEqual(copied, ["older **reply**"]);
+    });
+
+    it("/copy on an empty thread is a no-op", async () => {
+      stubClipboard();
+      const m = await mountView({ detail: detail({ messages: [] }) });
+      await acceptSlash(m, "/copy");
+      await m.flush();
+      assert.deepEqual(copied, []);
+      assert.equal(m.query("[data-copied-reply]"), null);
+    });
+  });
+
   it("/rewind opens the last-user-message confirm when there is no undo bar", async () => {
     const m = await mountView({
       onRewindAndResubmit: async () => {},

test/slashCommands.test.ts

@@ -42,6 +42,7 @@ describe("matchSlashCommands", () => {
       "/undo",
       "/usage",
       "/context",
+      "/copy",
       "/model",
       "/effort",
       "/permissions",
@@ -58,9 +59,9 @@ describe("matchSlashCommands", () => {
     }
   });
 
-  it("filters by prefix: /co hits compact, committee, context", () => {
+  it("filters by prefix: /co hits compact, context, copy, committee", () => {
     const names = matchSlashCommands("/co").map((c) => c.name);
-    assert.deepEqual(names, ["/compact", "/context", "/committee"]);
+    assert.deepEqual(names, ["/compact", "/context", "/copy", "/committee"]);
   });
 
   it("does not invent a match for an unknown /foo", () => {