[Bug]: Desktop renders reasoning summaries only as generic “Thought” labels

[coygeek]

Area

apps/desktop

Steps to reproduce

1. Run a T3 Code session that produces progress/reasoning summaries during a long-running task.
2. Open the session in the T3 Code desktop client.
3. Inspect the progress/reasoning entries in the transcript.
4. Open the same session in the T3 Code mobile client and compare the corresponding entries.

The comparison was made using the same project and session, 2026-06-06-repo-fleet / Repo Fleet Recovery Path Defects.

Expected behavior

The desktop client should display the human-readable progress summary associated with each entry, consistently with mobile. For example: Reading release.py, Inspecting function, Refactoring activation flow, Running full tests, and Polling for completion.

If the desktop UI intentionally collapses these entries, expanding one should reveal its summary text rather than only a generic label.

Actual behavior

The desktop client renders repeated entries only as Thought or Thinking, with no meaningful explanation. The same session in mobile displays the readable summaries.

The session data is present: the local T3 Code transcript contains non-empty reasoning-summary messages for this run. This suggests the desktop client is losing or failing to render the summary text, rather than the provider omitting it.

Impact

This makes long-running desktop sessions difficult to follow and can make active work look stalled or broken. It also creates a significant visibility mismatch between desktop and mobile for the same session.

Evidence

I will attach:

• A desktop screenshot showing repeated generic Thought / Thinking entries.
• A mobile screenshot showing the corresponding readable progress summaries for the same session.

Impact level

Major degradation or frequent failure

Version or commit

Desktop and mobile versions were not recorded at capture time.

Environment

macOS desktop client and T3 Code mobile client; Codex provider/model visible in the attached desktop screenshot.

Logs or stack traces

None.

Workaround

Use the mobile client to view the progress summaries. No equivalent desktop workaround is known.

[coygeek]

Laptop:

Mobile:

[juliusmarminge]

Triage

Confirmed as a desktop/web rendering issue, not missing session data.

#11784 now stores Codex item/reasoning/summaryTextDelta as role: "reasoning" messages. The collapsed desktop row in ReasoningTimelineRow (apps/web/src/components/chat/MessagesTimeline.tsx) always labels those "Thought" / "Thinking" and only mounts message.text when expanded. Current main mobile (ThreadReasoningRow) uses the same generic labels.

The mobile screenshot is the older compatibility path: clients that do not advertise reasoningMessages=true get reasoning remapped to system (ActivityPayloadProjection), and mobile then prints that text as a normal message. That is why the same session shows Reading release.py, Inspecting function, etc. on mobile and a Thought stack on desktop.

Expand should already reveal the summary; the desktop shot is fully collapsed. The real gap is scanability: Codex summaries are the progress headlines, and hiding them behind identical Thought rows makes long desktop turns look stalled.

Next step

Use a truncated first line of message.text as the collapsed label in ReasoningTimelineRow and ThreadReasoningRow when a short summary exists; keep "Thinking" / "Thought" as the fallback for streaming, empty, or long raw traces. Fix both clients so mobile does not regress when it ships #11784.

[juliusmarminge]

Closed by merged PR #12302, which adds truncated reasoning previews to collapsed web thought rows and reveals the full summary when expanded.