Two integration bugs found during review of #74522, both confirmed with
empirical probes against the production message-repair path:
1. Alternation: the summary marker was role="user" and an exchange was a
single assistant+tools group, so splicing between two user turns produced
user -> marker(user) -> user. The pre-request repair_message_sequence pass
(conversation_loop.py, runs before EVERY API call) then merged the marker
into the neighbouring real user message: metadata gone, cursor
unrecoverable on resume, and the summary text duplicated into the
transcript on every later pass (the transcript GREW every turn).
Fix: an exchange is now a full agent turn (assistant + tools + follow-up
assistant iterations, bounded by user messages), the marker is
assistant-role, and superseding an old marker deliberately merges the two
adjacent real user turns (plain-text \n\n-join, identical to repair
pass 2) so the returned transcript is alternation-valid by construction.
Probe result: repairs 0 (was 2), marker survives, no summary leakage.
2. Defrag destroyed user messages: _defrag_rolling_summary serialized the
whole remaining middle (user turns included) and spliced it away —
8 of 10 user prompts destroyed in one pass, contradicting the feature's
"your messages are never compacted" invariant. Fix: defrag now
re-summarizes only the rolling summary TEXT and rewrites the marker
content in place; transcript shape, cursor, and user turns untouched.
Probe result: 10 of 10 user prompts survive.
Also: marker provenance is now COMPRESSED_SUMMARY_HAS_USER_TURN_KEY=False —
micro markers absorb only assistant/tool content (#64650 invariant), and
real user turns remain in the transcript for provenance detection.
Adds 5 regression tests (repair-pass integration, alternation on
multi-iteration tool turns, defrag user survival, defrag input scope,
marker provenance); updates the two existing tests and the design doc to
the corrected semantics. 28 tests pass.
b8bfd68af1