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[FEATURE]: Async background compaction — don't block chat input #27358
Description
Problem
When auto-compaction fires (compaction.auto: true), it runs synchronously in the session loop, freezing the prompt input until it completes. On slow models or large contexts, this can lock the user out for minutes. The TUI becomes unresponsive and you can't even type.
Proposed behavior
- Compaction runs as a background job — user keeps chatting uninterrupted
- New messages sent during compaction get appended to the uncompacted history
- Once compaction finishes, the old history gets replaced by the compacted summary
- A toast or indicator shows "Compacting…" while it runs
- On completion, emit
session.compactedand swap in the compacted context
Existing foundation
SDK already defines CompactionPart and EventSessionCompacted — the event plumbing is there, only the execution path needs to become non-blocking.
Config
Could expose a toggle (default false for safety):
"compaction": {
"auto": true,
"background": true
}
Activity
github-actions commentedon May 13, 2026
This issue doesn't fully meet our contributing guidelines.
What needs to be fixed:
[FEATURE]: <title>(missing the colon after[FEATURE]).Please edit this issue to address the above within 2 hours, or it will be automatically closed.
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[-][FEATURE] Async background compaction — don't block chat input[/-][+][FEATURE]: Async background compaction — don't block chat input[/+]github-actions commentedon May 13, 2026
Thanks for updating the issue title and adding detailed content! However, there is still one required item missing from the Feature Request template:
- [x] I have searched existing issues and this has not been requested yet). Please add this to your issue.Please edit the issue to include this checkbox. Note that there are also potentially related issues (#16466, #13033) that you may want to review to confirm this is distinct.