cmux NEXT transcript: an opened message from another agent has one Copy

webviews/src/agent-session/acpmux/conversation/CardCopy.tsx

@@ -17,6 +17,11 @@ import "./CardCopy.css";
 /// `quiet`, a 12px glyph at 30%; `word`, the default glyph that says "Copied" beside its check.
 export type CardCopyLook = "faint" | "quiet" | "word";
 export const CardCopyLookContext = createContext<CardCopyLook>("faint");
+/// True inside a message whose opened card holds its Copy in the corner (IncomingMessageCard.tsx): the
+/// message's hover row then draws no Copy of its own, so an opened message has one Copy, never two
+/// (leo-workspace design/chat-transcript.md, "Each message has one Copy control"; Leo, 2026-10-27:
+/// "why are there two copy-paste symbols? I mean, two copy symbols").
+export const CardCopyShownContext = createContext(false);
 /// What puts the text on the clipboard: the page's clipboard, or a gallery stage's stand-in.
 export const CardCopyWriterContext = createContext<(text: string) => Promise<boolean>>(copyTextResult);
 

webviews/src/agent-session/acpmux/conversation/IncomingMessageCard.tsx

@@ -37,7 +37,7 @@ import { FindReveal } from "./chatFind";
 import { PromptMarksSession } from "../threadMinimap/promptMarks";
 import { Bot, ChevronRight, TerminalSquare } from "./icons";
 import { Markdown } from "./Markdown";
-import { CardCopy } from "./CardCopy";
+import { CardCopy, CardCopyShownContext } from "./CardCopy";
 import { AgentMark, knownMark } from "../../shared/AgentMark";
 import { useSenderChat, useSenderPlace } from "../subagents/subsessions";
 import { useAgentAvatar } from "../agentAvatar";
@@ -247,7 +247,8 @@ export function IncomingMessageLine({
               {t("message.reply")}
             </button>
           )}
-          {actions}
+          {/* Opened, the card's corner holds the message's Copy: the row draws none (CardCopy.tsx). */}
+          <CardCopyShownContext.Provider value={open && text.trim() !== ""}>{actions}</CardCopyShownContext.Provider>
         </span>
       }
     >

webviews/src/agent-session/acpmux/conversation/MessageActions.tsx

@@ -15,6 +15,7 @@ import { AlertCircle, Check, DoubleCheck, Pin, Retry, Speaker, Spinner, StopRead
 import { canReadAloud, readAloud, useReadingAloud } from "./readAloud";
 import { exactTime, relativeTime } from "./relativeTime";
 import { CopyButton } from "./CopyButton";
+import { CardCopyShownContext } from "./CardCopy";
 import { hasMessageMenuHost, openMessageMenu, openForkMenu } from "./messageMenu";
 import { RetryModelMenu } from "./RetryModelMenu";
 import { TurnActionsContext } from "./turnActions";
@@ -308,13 +309,15 @@ export function SentActions({ text }: { text: string }) {
 /// The row at the end of another agent's message line (IncomingMessageCard.tsx IncomingMessageLine):
 /// its age, Copy, Retry and Pin, then `more` (a waiting steer's ⋯, QueuedMessageCard.tsx) in the
 /// same group, never a second one beside it. No read receipt: the message is the agent's to read.
+/// Opened, its card's corner is the message's one Copy (CardCopyShownContext), so the row has none.
 export function ReceivedActions({ row, text, more }: { row: AcpmuxRow; text: string; more?: ReactNode }) {
+  const cardCopies = useContext(CardCopyShownContext);
   return (
     <>
       <span className="cv-received-actions">
         <MessageFooterRow>
           <MessageTime at={row.at} className="cv-user__time" />
-          <MessageCopy text={text} />
+          {!cardCopies && <MessageCopy text={text} />}
           <PromptRetry rowId={row.id} prompt={row.resend ?? row.text ?? ""} />
           <PinButton rowId={row.id} />
           {more}

webviews/test/received-message-one-copy-browser.test.ts

@@ -0,0 +1,115 @@
+// cmux-web-test-timeout: 300
+// l10n-allow-file: browser test diagnostics, not shipped UI.
+// Another agent's message has one Copy (leo-workspace design/chat-transcript.md: "Each message has
+// one Copy control"; Leo, 2026-10-27: "why are there two copy-paste symbols? I mean, two copy
+// symbols"). Closed, its line's hover row holds it; opened, the card's top-right corner does (Leo,
+// 2026-10-29: "wouldnt it be a little copy symbol on the top right within this card?", #28057), and
+// the line's hover row drew a second one beside the time. Real Chromium on the gallery's
+// `agent-pane.incoming-message` entry, the pointer on the message's line as a person reads it. With
+// FAST_CHECKS_OUT set it writes 2x light and dark stills of the opened message.
+import { afterAll, beforeAll, describe, expect, setDefaultTimeout, test } from "bun:test";
+import path from "node:path";
+import { mkdir } from "node:fs/promises";
+import { chromium, type Browser, type Page } from "playwright";
+import { requireBrowserLane } from "./support/requireBrowserLane";
+import { galleryFrame, warmGalleryFrame } from "./support/galleryFrame";
+
+await requireBrowserLane("received-message-one-copy-browser.test.ts", async () => {
+  const ENTRY = "agent-pane.incoming-message";
+  const LINE = ".cv-received .cv-disclosure__toggle";
+  setDefaultTimeout(180_000);
+  let browser: Browser | undefined;
+  try {
+    browser = await chromium.launch({ headless: true, timeout: 30_000 });
+  } catch {
+    console.warn("received-message-one-copy: chromium cannot launch here; skipping");
+    describe.skip("received message one copy", () => test("browser", () => {}));
+    return;
+  }
+  const { createServer } = await import("vite");
+  const webviews = path.resolve(import.meta.dir, "..");
+  const out = process.env.FAST_CHECKS_OUT;
+  let vite: Awaited<ReturnType<typeof createServer>> | undefined;
+
+  beforeAll(async () => {
+    vite = await createServer({
+      root: webviews,
+      configFile: path.join(webviews, "vite.config.ts"),
+      server: { port: 0, host: "127.0.0.1", strictPort: false },
+      logLevel: "error",
+    });
+    await vite.listen();
+    await warmGalleryFrame(vite, ENTRY, { params: { variant: "opened" } });
+    if (out) await mkdir(out, { recursive: true });
+  }, 200_000);
+  afterAll(async () => {
+    await browser?.close();
+    await vite?.close();
+  });
+
+  const open = async (variant: string, colorScheme: "light" | "dark"): Promise<Page> => {
+    const port = (vite!.httpServer!.address() as { port: number }).port;
+    const page = await browser!.newPage({
+      viewport: { width: 760, height: 520 },
+      deviceScaleFactor: 2,
+      reducedMotion: "reduce",
+    });
+    await page.goto(
+      `http://127.0.0.1:${port}${galleryFrame(ENTRY, { variant, colorScheme, width: 760, height: 520 })}`,
+    );
+    await page.waitForFunction(() => document.documentElement.dataset.galleryReady);
+    await page.waitForSelector(LINE);
+    return page;
+  };
+
+  /// The Copy buttons of the first received message, the line's hover row and its opened card.
+  const copies = (page: Page) =>
+    page.evaluate((line) => {
+      const message = document.querySelector(line)!.closest(".cv-received")!;
+      const names = [...message.querySelectorAll<HTMLButtonElement>("button[aria-label]")].map(
+        (button) => button.getAttribute("aria-label") ?? "",
+      );
+      return {
+        expanded: document.querySelector(line)!.getAttribute("aria-expanded"),
+        copy: names.filter((name) => name === "Copy").length,
+        corner: message.querySelectorAll(".cv-card-copy button").length,
+      };
+    }, LINE);
+
+  for (const colorScheme of ["light", "dark"] as const) {
+    test(`a closed message's line has one Copy (${colorScheme})`, async () => {
+      const page = await open("long", colorScheme);
+      try {
+        await page.hover(LINE);
+        expect(await copies(page)).toEqual({ expanded: "false", copy: 1, corner: 0 });
+      } finally {
+        await page.close();
+      }
+    });
+
+    test(`an opened message has one Copy, the card's corner (${colorScheme})`, async () => {
+      const page = await open("opened", colorScheme);
+      try {
+        await page.waitForSelector(`${LINE}[aria-expanded="true"]`);
+        await page.waitForSelector(".cv-received__text");
+        // The pointer on the line, where the hover row shows.
+        await page.hover(LINE);
+        // The still first, so a red run still shows what it drew.
+        if (out) await page.screenshot({ path: path.join(out, `received-message-opened-${colorScheme}-chromium.png`) });
+        expect(await copies(page)).toEqual({ expanded: "true", copy: 1, corner: 1 });
+        // Closed again, the line's row has its Copy back.
+        await page.click(LINE);
+        await page.waitForSelector(`${LINE}[aria-expanded="false"]`);
+        // Its panel (and the corner Copy in it) leaves once the close has played.
+        await page.waitForFunction(
+          (line) => !document.querySelector(line)!.closest(".cv-received")!.querySelector(".cv-card-copy"),
+          LINE,
+        );
+        await page.hover(LINE);
+        expect((await copies(page)).copy).toBe(1);
+      } finally {
+        await page.close();
+      }
+    });
+  }
+});