Turn folds hide the agent's replies to mid-run messages and leave progress notes visible instead #28161

What happened

In long working sessions, the turn fold ("Worked for X" / "Continued for X") often hides the agent's actual reply to the user and leaves a progress note visible instead. When the user sends a message during a run, the agent's reply to it is usually folded. Sometimes the agent answers only inside a progress note and carries on working, so the user sees no answer at all unless they ask again. Same on web, desktop and mobile.

Diagnosis

In apps/web/src/components/chat/MessagesTimeline.logic.ts, deriveTerminalAssistantMessageIds treats only the last assistant message of each run as the answer, and deriveTurnFolds hides every other assistant message in the run. A message sent during a run becomes a steer inside the same run, so the reply to it is never the run's last message:

1. Replies to steers are folded. With several follow-ups in one run, only the final summary stays visible.
2. Answers given inside a progress note disappear. Agents often answer a mid-run question in one clause of their next status update and keep working. That habit isn't T3's bug, but the fold hides the only place the answer exists.
3. A trailing progress note ("check is running, I'll report when it finishes") becomes the visible answer, and the findings before it are folded.

Related: interrupted, failed and cancelled runs never fold, so all their progress notes stay visible.

Steps to reproduce

1. Start a task that keeps the agent working for several minutes.
2. While it works, ask a question about the work ("should we do X or Y?").
3. The agent answers briefly, often inside a status update, keeps working, and finishes with a summary of the work.
4. After the run, the answer is inside the "Continued for X" fold and the visible summary doesn't repeat it.

Version

0.1.5-nightly.20261029.3877 (local server). Later commits to MessagesTimeline.logic.ts don't change this rule.

Environment

Server: Linux x64, local. Clients: web (Firefox on Android) and others, same behaviour. Provider: Claude agent (claude-opus-5-5).

Evidence

One long thread (~80 runs, many with several steers):
- In multi-steer runs, every direct reply to a mid-run question was folded; only the final summary stayed visible.
- A design question was answered in one clause of the next progress note, followed by 17 minutes of work. The "Continued for 17m 8s" fold hid it; the user had to ask again (screenshot below).
- One run's only visible message was "The check is running in the background; I'll report once it finishes"; its findings were folded.
- One interrupted and twelve cancelled runs showed every progress note unfolded.

Related issues

#15380 (closed): mid-turn progress note shown below "Worked for". #17382: replies disappear after expanding "Worked for". #15279 (closed): steered messages render below "Worked for".

Fix applied or workaround

None applied. Workarounds: expand the fold; wait for a run to finish before asking a follow-up.

Detecting answers by content probably isn't reliable and may vary by model. Directions using only timeline structure:

• Keep the first agent message after each steer visible.
• Show a hint on the fold row (count of hidden replies or a short preview).
• Fold interrupted and cancelled runs like completed ones.
  Might also help: T3's agent instructions could ask for a short standalone reply to a mid-run message before resuming work.

Filed by

Claude Code (claude-opus-5-5) via t3 triage, on the user's behalf.