[flamboh]

Fix for the redesign stack, targets layer 2 (#28840).

Note

🤖 Claude Opus 5.5 on behalf of Oliver

Problem

A finished turn with a steer folds into a "Worked for …" row on top and a "Continued for …" row below each steer. The rows measured different things. The top row showed the whole turn's time and the turn's checkpoint diff. Each "Continued" row showed only its own segment's time and the edits the provider reported in it. So a segment could show a bigger diff than the whole turn, and the top row's time already included the segments below it, which read like the turn took twice as long.

Fix

In a steered turn, every fold row now describes its own segment only, measured the same way:

• Time: the top row runs from the turn start to the first steer. Each "Continued" row keeps its own segment's time.
• Diff: every row, the top one included, sums the provider's file edits in its own segment. Rows with no edits show no diff.

Turns without steers are unchanged: one row with the whole turn's time and the checkpoint diff, matching the changed-files card. Running turns are unchanged too.

Trade-off: steered rows use provider edit counts, so their diffs can add up to more than the changed-files card when the same lines were edited twice.

Before (layer 2)	After

Validation

• The steer-segment fold test in MessagesTimeline.logic.test.ts now gives each segment different edits and asserts each row's own time and diff (Worked for 10s +12 −1, Continued for 20s +40 −0). It fails on layer 2 and on the previous head of this PR, and passes now. The existing single-row checkpoint test still asserts the checkpoint diff.
• vp run check:changed origin/maria/redesign/2-composer-timeline: all pass.
• Captured a finished Replay turn steered mid-run, dark mode, same thread before and after.

Made with Claude Opus 5.5 in Claude Code.

[macroscopeapp]

Approvability

Verdict: Approved at 599b632

Macroscope's review found this PR approvable — Steered timeline folds now show segment-specific time and edit counts, with the ending status attached to the final displayed segment. The change is confined to presentation and does not alter execution or stored data.

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Dismissing prior approval to re-evaluate e677fd2