Improve thinking trace and file-edit tool presentation

[Yuruzuu]

Problem

Thinking traces currently use the foreground color, which makes them difficult to distinguish from regular assistant text.

File-edit tool rows are also difficult to scan. The full path takes up most of the row and gets truncated. Expanding one shows the path again and an “Open diff” button, so reviewing the actual change requires opening the diff tab on the right.

Proposal

• Use muted text for thinking traces. This would make them visually distinct from assistant responses while keeping them readable in light and dark themes.
• Show the action and file name first. For example, Edited SectionRail.luau or Created FileName.js. Keep the full path available on hover or expansion.
• Highlight file names in expanded tool calls and make them clickable. For read, edit, and create tools, clicking the highlighted file name should open that file in the right sidebar.
• Show a small inline diff when expanding an edit/create tool. Display the relevant changed lines directly below the tool call, similar to Claude Code/Codex. Keep “Open diff” available for the full view.
• Include lines added and removed in edit rows. For example, Edited SectionRail.luau +12 −4, so the size of the change is visible without opening the diff.

Scope

Thinking text and file read/edit/create tool presentation in the web/desktop chat timeline.

I’d like to discuss these together because they affect how readable the agent’s activity is while following a turn. Implementation could be split into separate PRs.

Related work includes #12302, which adds independent thinking expansion, and #15506, which mutes tool results. These requests build on that presentation.

Questions for maintainers

Would you be open to these changes? Are there any you’d prefer to narrow or handle differently?

I’d be happy to contribute once the direction and scope are agreed on.

[breadow]

+1 This would be super nice :)

[ShinsokuDev]

Would definitely love to see something like this implemented, it’d make the overall experience feel a lot smoother.

[Trtim]

+1 this would help alot

[thekuddlekoala]

Awesome work! Can't wait to use it!