## Why
The 900-byte recap prompt limit leaves little room for completed progress, unresolved caveats, and recent corrections. Recaps need this context to distinguish completed work from pending requests.
## What changed
- Introduce a shared `RecapPrompt` with a 32 KiB ceiling for instructions and history, using an 8,192-token estimate. Instruct summaries to retain the broader goal, completed outcomes, and unresolved availability or validation caveats.
- Select up to eight answered exchanges plus a pending request, preserving adjacent steering and progress messages. Drop older whole exchanges before excerpting both ends of oversized messages, while retaining the newest answer and pending correction.
- Require a `summary` and nullable `next_action`, bounded to 700 and 200 characters respectively. Reject malformed or oversized responses and display an optional, separately styled `Next:` line.
## Testing
Add coverage for UTF-8 prompt bounds, exchange selection, pending corrections, excerpt boundaries, strict response parsing, and next-action rendering. Extend the recap generation integration test to verify bounded history and the structured response schema.
GitOrigin-RevId: 6c6a84bc602a168418c1952feb1d286ec0cb9e28
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