Three review follow-ups on the salvaged #79286 commit:
- update_model() zeroed the in-memory prune runway but left the durable
model_config copy stale, breaking the method's own durable-sync
discipline (the strike reset three lines above keeps its durable copy
in sync). A restart after a model switch resurrected a runway
computed under the old model's trigger sizes. New
_clear_durable_proactive_prune_rearm() removes the persisted key via
patch_session_model_config() without touching the transcript.
- The archive_and_compact capability check ran AFTER the expensive
3-pass prune scan, so a duck-typed session store lacking the method
paid the full scan on every eligible iteration forever with pruning
permanently no-opping. Hoist it above the scan (all in-tree stores
pass a real SessionDB; this only affects third-party stores).
- _load_proactive_prune_rearm_tokens now uses the shared
get_session_model_config_value() accessor instead of inlining a 5th
copy of the model_config JSON parse, matching its sibling loaders'
typed-accessor pattern.
Also documents why the rotation-publish-failure branch restores only
the runway field rather than the full attempt snapshot.
Tests: model-switch durable clear, patch_session_model_config
merge/delete/no-op, and a guard proving incapable stores skip the scan.
kshitij