fix(compressor): reset cooldown and model-fallback flag on session reset (#16067)

[briandevans]

Summary

• Add self._summary_failure_cooldown_until = 0.0 to on_session_reset()
• Add self._summary_model_fallen_back = False to on_session_reset()

The bug

ContextCompressor.on_session_reset() (called on /new and /reset) was missing two attribute resets:

1. _summary_failure_cooldown_until — when compression summary fails (no aux provider, rate limit, transient error), the compressor sets a cooldown of up to 10 minutes before retrying. This attribute was initialized to 0.0 in __init__ but was never zeroed in on_session_reset(). Result: a compression failure in session A causes summarization to be silently skipped at the start of session B, with the log line "Skipping context summary during cooldown" as the only indication.

2. _summary_model_fallen_back — set to True when the primary summary model fails and a fallback is selected. Also missing from on_session_reset(). Result: session B always skips the primary model and goes straight to the fallback, even though the failure was in a different session entirely.

Both attributes are set to their clean values in __init__ but the reset path was incomplete.

Test plan

• Before: direct Python test confirms both attributes persist across on_session_reset() call — _summary_failure_cooldown_until remains ~600s and _summary_model_fallen_back remains True
• After: TestCompressorSessionReset::test_reset_clears_summary_failure_cooldown and test_reset_clears_summary_model_fallen_back both pass
• All 3 TestCompressorSessionReset tests pass
• Adjacent tests/agent/test_context_engine.py suite unchanged

Related

• Fixes [Bug]: ContextCompressor.on_session_reset() fails to reset _summary_failure_cooldown_until, causing compression summary to be silently skipped in new sessions #16067

🤖 Generated with Claude Code

[alt-glitch]

Likely duplicate of #15549 — same root cause (incomplete on_session_reset), and #15549 is a superset that also resets summary_model.

[Copilot]

Pull request overview

Fixes cross-session leakage in the agent’s ContextCompressor by ensuring additional per-session summarization state is cleared when the user starts a new session (/new) or resets (/reset).

Changes:

• Reset _summary_failure_cooldown_until to 0.0 in ContextCompressor.on_session_reset().
• Reset _summary_model_fallen_back to False in ContextCompressor.on_session_reset().
• Add unit tests asserting both values are cleared by on_session_reset().

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 3 comments.

File	Description
agent/context_compressor.py	Clears summarization cooldown and fallback flag during session reset to prevent state leaking across sessions.
tests/agent/test_context_engine.py	Adds regression tests for session reset clearing cooldown and fallback flag.

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[briandevans]

CI baseline classification

The test job failure is a pre-existing baseline on origin/main, unrelated to this PR:

File	Error	Status
tests/gateway/test_discord_channel_controls.py	AttributeError: 'types.SimpleNamespace' object has no attribute 'guild'	Pre-existing (tracked in #15820)
tools/browser_tool.py	ValueError: I/O operation on closed file	Pre-existing cleanup noise

These failures reproduce on origin/main without my changes. All other checks pass ✅ (check, nix/macos, nix/ubuntu, e2e, supply-chain, attribution).

[briandevans]

Closing as superseded by #15549, which is a more complete fix for the same root cause (incomplete on_session_reset()) — it also restores summary_model from a preserved _summary_model_original value. My patch is a strict subset. Recommend merging #15549 first.