Fixes#93022. A short session (protection window >= transcript) hits the
"insufficient messages" / "no compressible window" branches twice and
permanently trips the anti-thrash breaker, even though nothing was
eligible to compress - compression was never attempted, so there is
nothing "ineffective" to score. The session then rides past the
threshold with no compaction possible (recovery probes only soften,
not fix, the misclassification).
Distinguish "nothing eligible right now" from "attempted and
underperformed":
- New transient _structural_no_op_backoff_until (in-memory, 300s)
armed by _record_structural_no_op() at the three structural no-op
sites: insufficient_messages, no_compressible_window,
empty_post_handoff_window. No strikes accumulate; auto-compaction
resumes on its own once the backoff lapses or the transcript outgrows
the protection window.
- The backoff gates should_compress via
_automatic_compression_blocked_locally and surfaces in
_compression_block_reason as "structural_backoff:<seconds>".
- #40803's frozen-CLI guarantee is preserved: a transcript that can
never shrink retries at most once per backoff window instead of
every turn.
- force=True (/compress) clears an active backoff before attempting;
record_completed_compaction() lifts it - both prove the transcript
is compressible/being worked.
- Genuine attempted-but-underperformed verdicts still strike the
durable ineffective counter unchanged.
Tests: new tests/agent/test_context_compressor_structural_backoff.py;
updated the two tests that asserted the old strike-on-noop behavior.
The anti-thrash guard (_ineffective_compression_count) was in-memory
only: a fresh compressor bound to a resumed, already-compacted session
started with compression_count=0 and a disarmed guard, so a
near-threshold session could legally re-compact once per process
restart, forever.
Persist the counter through the durable session-state channel,
mirroring the failure-cooldown (#54465) and fallback-streak (af7dceaf7)
pattern:
- hermes_state.py: sessions.compression_ineffective_count column
(declarative reconciliation adds it on existing DBs) +
get/set_compression_ineffective_count accessors.
- context_compressor.py: every strike/clear verdict routes through
_record_ineffective_compression_verdict() which writes through to the
session row (no-change verdicts skip the DB write);
bind_session_state() loads the persisted value; the compression
rotation boundary carries the counter onto the child row;
update_model()'s reset also clears the durable copy; the
ineffective-only fast path in _automatic_compression_blocked() is
removed because the counter is now durable and another agent's clear
must unblock a stale local snapshot.
- conversation_compression.py: _refresh_persisted_compression_guards
re-reads the counter alongside cooldown + fallback streak.
Reset semantics are unchanged: any real provider reading below the
threshold still clears the counter — and now clears it durably too.
Resolves the residual gap identified in #54923 by @lanyusea (the
second-threshold mechanism was superseded by persisting the existing
guard state).
Co-authored-by: lanyusea <lanyusea@gmail.com>
Aniruddha Adak