When context compaction's summary generation fails, the compressor's default
path (abort_on_summary_failure=False) drops the middle window and inserts a
static 'summary unavailable' marker — destroying the compacted turns. #29559
reported the field impact: a Connection error at the compaction moment dropped
124->15 messages (110 lost) for a long browser-automation task; #25585 is the
same failure mode (failed summary commits a destructive compaction anyway).
compress() already has an EXCEPTION to the historical drop default: auth
failures (401/403) ALWAYS abort and preserve the session, because rotating into
a placeholder-summary child on a broken credential strands the user. A transient
network/connection error is the same situation in reverse: it WILL recover, and
retrying then is strictly better than discarding context for a momentary blip.
Extend the always-abort carve-out to terminal connection/network failures:
- new _last_summary_network_failure flag, set in _generate_summary's terminal
failure branch when _is_connection_error(e) (reached only after any main-model
fallback is exhausted), reset alongside the auth flag;
- compress() aborts when it's set (returns messages unchanged,
_last_compress_aborted=True), independent of abort_on_summary_failure;
- a network-specific operator warning (distinct from the auth + config-flag
messages).
Scoped to connection errors only: a generic 500/400 still takes the historical
fallback-drop path (test_non_auth_failure_still_uses_fallback_path stays green).
Tests: network-failure detection + abort-despite-flag-false, both mutation-checked
(removing the flag-set fails detection; removing the carve-out fails the abort).
ac822e4d36