fix(agent): bound context compression summary stalls (salvage #49905)

[kshitijk4poor]

Summary

Salvage of #49905 by @LeonSGP43 (rebased onto current main + a rebase-follow-up fixing a production gap the rebase exposed). Bounds context-compression summary generation with a hard timeout so a wedged summary call can't block the gateway loop indefinitely (#49768).

The bug

call_llm forwards auxiliary.compression.timeout to the provider client as a socket/read timeout only — it does not bound the caller's wait if the network stack wedges or the SDK ignores it. The synchronous summary call in context_compressor.py was wrapped only in aux_interrupt_protection() (which suppresses interrupts — the opposite of a timeout), so compression summary generation could block the gateway loop forever. Confirmed still present on main.

The fix

@LeonSGP43's fix: run the summary call_llm in a ThreadPoolExecutor(max_workers=1) worker and stop waiting after auxiliary.compression.timeout (future.result(timeout=...), shutdown(wait=False, cancel_futures=True)). On timeout it raises, caught by the existing handler and routed into the deterministic fallback summary path — the gateway stays responsive.

Rebase + production-gap fix (this salvage)

The PR was ~592 commits behind; the compressor drifted (two cosmetic conflicts). Resolved by composing main's aux_interrupt_protection wrapper + defensive message coercion with the PR's timeout call (documented the thread-local interaction honestly: the protection guards caller-thread unpacking, the hard timeout is the stronger guarantee for the wedged-socket case — complementary, not nested).

Fixing the rebase surfaced a real production gap: the hard timeout raises a builtin TimeoutError, but _generate_summary's handler set _is_streaming_closed = _is_connection_error(e) — and _is_connection_error classifies any exception whose type name contains "Timeout" as a network close. That set _last_summary_network_failure=True, making compress() take the network-failure ABORT branch (return messages unchanged) instead of the deterministic fallback — the opposite of the PR's intent. Gated it: _is_streaming_closed = _is_connection_error(e) and not _is_timeout. Mutation-verified against the contributor's own test_compress_hard_timeout_uses_existing_fallback_path (reverting the gate fails it). Genuine streaming-closes don't carry "timeout" wording, so they're unaffected.

Review

Ran hermes-agent-dev + hermes-pr-review Phase 2c — 0 Critical. The executor pattern is correct, the abandoned-thread trade-off is bounded/documented, auxiliary.compression.timeout confirmed in DEFAULT_CONFIG, and the false-suppression edge for the _is_timeout gate was independently checked (genuine mid-stream closes are correctly preserved).

Tests

pytest tests/agent/test_context_compressor.py -q   # 142 passed (CI runs the full suite)

Supersedes #49905. Full credit to @LeonSGP43.

[kshitijk4poor]

Withdrawing this salvage for now — closing per maintainer direction to focus the current batch elsewhere. The underlying #49905 (bound context compression summary stalls) remains open and can be re-salvaged later. No changes merged.