Why: long multi-turn executions grow the JSONL transcript until they
hit provider context limits (parity-matrix #11), and a crashed append
left a partial line that made the whole session unloadable
(parity-matrix #12 resume semantics).
Evidence: go vet ./... clean; go test ./... 13 packages ok. Session
cases: crash-residue tail skipped while mid-file corruption still
errors, Stats line/byte counts, meta sidecar roundtrip (missing meta
nil), Compact rewriting system+summary+keepLastN atomically with no
tmp residue, no-op on short transcripts, summarizer error leaving the
file untouched. Adapter case: threshold-triggered compaction runs
before the loop and the summary marker reaches both the transcript
and the model's context.
Impact: session gains Stats/SaveMeta/ReadMeta/Compact; native.Options
gains Compact *CompactConfig (default summarizer is one tool-less
stream call; compaction failure logs and continues - optimization,
never a silent failure); session meta sidecar records model/scope/
exec id per execution.
Refs: docs/parity-matrix.md #11/#12 (Batch3 scope).
weichen
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