feat(session): fold compaction into a fat handoff file with a thin live spine - #1155
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TheGreatAxios merged 6 commits intoSep 22, 2026
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…ve spine A fold writes the full structured record to one stable handoff file and keeps only a short spine plus an explicit pointer in the prompt. The completeness gate rejects folds that drop novel text, so the spine re-renders carried facts byte-identical and every fold overwrites the same latest key instead of chaining per-fold files.
Iterative folds dropped fold-1 paths when the next region was only the prior spine plus later turns, and a growing Evidence/Constraints line fail-closed the completeness gate. Union the previous fat file, scan tool_result evidence, and archive synthetic spines as user_message.
Prefix-collapse treated src/auth as a truncation of src/auth.ts. Scanning every ## heading let a model Summary overwrite schema, and empty constraint arrays won over carried spine facts via ??.
Production iterative folds merge full prior-file text, so prefix unique collapsed distinct constraints, decisions, and verification that only shared a string start.
An 80-char complete fact that prefixes a sibling was collapsing on the next fold because the cut detector used length alone.
Cuts are 83 chars; longer-string-wins replaced 81- and 82-char complete facts with the truncated spine fragment and dropped the last characters.
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Summary
Verification
bun run checkpasses (typecheck, lint, format, full test suite)bun test src/session/compaction-handoff.test.tspasses (12 tests)bun test src/context-compactor.test.ts tests/integration/compaction-baseline.test.tspasses (updated spine expectations)Fixes CL-8744