Deliver 'don't silently lose work at compaction' via the mechanism that
actually works. Verified contract: a PreCompact hook CANNOT make the model
flush to Scribe (host hooks can't trigger model tool calls, and can't know the
in-flight task ids), and its additionalContext only shapes the one-shot summary.
The correct tool is SessionStart scoped to source=compact, which fires AFTER
compaction and injects context the model reads.
Our SessionStart hook is matcher-less, so it already fires on compact — it just
said nothing compaction-specific. Now it reads the stdin event and,
when source==compact, leads with a banner telling the model to reload the active
project + in-flight tasks from Scribe and reconcile half-remembered state.
Durable path = record-as-you-go (A4/B8) + this post-compaction reload.
Refs plan 812 (A7); supersedes the literal 'PreCompact hook' idea.
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
bvandeusen
d99c4e3c15