The #14694 recovery clock (`_anti_thrash_recovery_deadline`) was a
process-local `time.monotonic()` value zeroed in `bind_session_state()`.
The gateway rebuilds the AIAgent (and its ContextCompressor) on every
cache eviction, so each fresh compressor bound to a durably tripped
session row (#69872) re-armed a full 300s window and the half-open probe
never fired — a long messaging conversation above the threshold stayed
blocked permanently.
Persist the deadline as a wall-clock epoch in a new
`sessions.compression_recovery_deadline REAL` column (declarative column
reconciliation; SCHEMA_VERSION 26 -> 27) with
`SessionDB.get/set_compression_recovery_deadline`. The compressor loads it
in `bind_session_state()` and writes it on change only via
`_set_anti_thrash_recovery_deadline()`. A fresh compressor with no stored
deadline still starts a full window blocked (#54923 restart contract); one
that loads an armed deadline resumes that window. Backward clock jumps are
bounded to one window. The 300s window is unchanged.
Minimal salvage of #100185 (the probe-lease/fencing state machine and
model_config-blob storage were not carried).
Refs #100185
Co-authored-by: Komzpa <me@komzpa.net>
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