Long-lived sessions become unloadable: events.jsonl never capped/rotated, replayed in full on open

[Ljosmann]

Summary

A long-lived CLI chat session becomes unloadable once its events.jsonl grows large. The loader appears to read/replay the entire event log on open, so a heavily-reused session eventually fails to load. Reuse + pinning is the intended workflow, so this hits the sessions people care about most.

Impact

• A reused session ran for weeks and became impossible to open.
• events.jsonl reached ~460 MB / ~147k lines across 544 compactions.
• On open the app loops: load → fail → append sessionEnd hooks → repeat, so the file keeps growing during failed loads.
• User-visible: "can't get it to load," accumulated context appears lost.

Root cause

• events.jsonl is append-only and is never rotated or capped.
• Compaction shrinks the model context but does not shrink the on-disk log.
• It is not a few giant lines: lines >200 KB total only ~23 MB (largest ~775 KB). The remaining ~435 MB is the sheer count of ordinary events, so the loader must not depend on full-log size.

Repro

1. Reuse one session for many days (hundreds of compactions).
2. Let events.jsonl exceed a few hundred MB.
3. Reopen — load hangs/fails; file grows on each retry.

Workaround (reversible)

Trim events.jsonl to the last few compaction cycles (keep session.start + tail): ~35 MB / ~11.6k lines loaded fine, full log preserved as backup.

Proposed fixes

1. Tail-load on open from the latest compaction boundary; don't replay the whole file.
2. Cap + rotate events.jsonl (roll past a threshold; keep N recent cycles; archive the rest).
3. Stop the failure loop — don't append sessionEnd on failed load; expire/release the stale inuse.<pid>.lock.
4. Optional: keep heavy assets out of the event stream (store as files referenced by path).

Acceptance

A session reused for weeks (hundreds of compactions) opens reliably without manual trimming.