PR #21747 - manaflow-ai/cmux

Summary

A message from another session reached the agent pane as an ordinary prompt and drew as the person's own bubble. It showed the whole envelope the cmux-tui pump writes: "[cmux agent message] from …", the message id, the safety line and the reply hint, and then the words. The prompt carries _meta.provenance.kind: "agent_message" with the sender (acpmux prompt_provenance.rs, cx-55d27), but the pane never read it.

Now the message draws as Claude desktop does (refs transcript-received-messages-group.png, transcript-received-message-expanded.png and transcript-peer-session-message.png in cmux-design-references; "Messages and actions" in #21604):

One muted line, "Received message from ". The sender is underlined and opens that session's chat when it is a chat acpmux runs (from is acp:<id>). Any other sender is plain text.
The chevron, or a click on the line, opens the sender's own words under it in muted body type. The envelope is stripped at its --- line and its closing line, which repeats the message id so a body cannot fake it. Text in any other shape is kept whole.
A message waiting behind a busy turn stays in the composer queue, where it can be removed or sent now, as before. It draws as a received line once it lands.
Find searches the sender's words, not the envelope, and opens the line (and its group) to show a match. Copy copies the words. A received prompt offers no Retry or Edit, which would resend the envelope as the person's own.
Two or more received lines in a row fold into one "Received N messages" line, which opens to them.
This draws for everyone. A started task's result (offer_result) still draws as before, behind its toggle.

Out of scope, and listed in #21604:

Delivering a message at the agent's next step rather than after the turn. acpmux queues agent messages with steer: false.
The queued/submitted/done state from prompt_accepted and turn_started.

Testing

bun test test/received-messages.test.tsx. It drives the real AcpmuxDirectClient over a fake daemon, then shapes and renders the rows.
- Red on 0542edc, the test commit alone: the module didn't exist.
- Green on 0896598 and a1a20e6: 3 pass.
- After an independent review: a new test commit went red with 4 fail and 1 pass, then green on cc686da. It covers five things:
  - The row kind that redraws on open.
  - The queue keeping waiting messages.
  - Find, copy and retry/Edit using the body.
  - The group listing its lines.
  - The review found a misplaced memo comparator, so a landed message never opened. This is now fixed. The test checks four things:
  - The parsed sender, link and body, with no envelope text in the closed or open line.
  - A queued message is not in the composer queue and draws one line before and after it lands.
  - Three lines fold, and the fold opens to them.
  - A lone line stays a line.
bun test on chat-find (4 files), transcript-copy, gallery-coverage, transcript-newest-last and transcript-worked-fold, with the test above: 37 pass, 1 browser test skipped.
bun run typecheck passes.
Not run: the browser tests (agent-pane-suggested-tasks). Host load was 160 to 350 today and the dev server kept timing out. The offer_result path is unchanged.
No app build. The change is webview only, and the screenshots come from the new gallery entry agent-pane.received-messages in headless Chromium.
Localization: two new strings, received.group (plural, {n}) and received.show, in all 21 locales, marked needs_review outside English. The line reuses offer.received. gen-strings.mjs agentPane reports nothing missing.

Changelog

Changed: A message from another session shows as "Received message from" its sender, which opens to the message, instead of as your own prompt

Proof

Gallery agent-pane.received-messages, dark, normal width.

One message	Opened

Three in a row	Folded line opened

Before, each of these was a right-aligned user bubble holding the full envelope text.

Checklist

Failing test committed before the fix
Gallery coverage for the new components
Strings in every locale
Browser lane run (blocked by host load, see Testing)

🤖 Generated with Claude Code