plat 539

← chat / reliability

PLAT-539 — A long Codex chat showed its FIRST reply (3 October sandbox test) again after every turn

Field	Value
State	fixed on main
Priority	-
Product	chat
Area	reliability
Summary	fixed on main, not deployed: the sidecar completion path now emits nothing when the turn is no longer tracked.

Coordination	Value
State	fixed on main (2026-10-05); not deployed; owner to check the chat after a restart
Date	2026-10-05
Owner	chat-reliability

Source

Owner, sales-outreach chat (Codex): after "The run finished: 0 messages..." the chat showed "Ran from the CLI runtime directory using only my own shell tools ..." and a sandbox test table. The Codex terminal showed only the real reply (10:06 PM).

Cause (verified)

• The extra text was a second unified_completion (seq 16138, source: coding_agent_sidecar) written one second after the real one (seq 16135, canonical_turn_completion). Its text is the final message of the thread's FIRST turn (3 October 17:35). The same text had been recorded the same way at seq 11055, 12707 and 13030 on 4 October. coding_agent_sidecar is only the label of the server's own retained-turn completion path (emitRetainedMainTurnStreamCompletion, server.go).
• That path re-reads the turn's start time from retainedMainTurns. After the structured completion has settled the turn the entry is gone, so the start time is zero. With a zero start the "already emitted" guard is skipped, and ReadRetainedTurnMessages / readCodexRolloutFinalAssistantText (provider) applies no timestamp filter and keeps the completion of the first task_started turn in the file. The rollout itself was correct (175 turns, in order).
• The chat is one thread since 3 October, so the first turn is old. Any retained Codex chat can show its first reply the same way.

Done

• emitRetainedMainTurnStreamCompletion: with no tracked turn it logs [RETAINED_TURN] No active retained turn, not emitting a completion and emits nothing. Test TestRetainedTurnCompletionEmitsNothingWhenTheTurnIsNoLongerTracked fails with one stale event on the old code.

Left

• Provider hardening (not done): ReadRetainedTurnMessages should return nothing for a zero turn start, as the progress reader already does; it needs a provider commit and a pin bump.
• The stale completions already stored in the sales-outreach chat's history stay (seq 11055, 12707, 13030, 16138); they are old events, not removed.
• Owner check after restart: no extra sandbox reply after the next turn of a long Codex chat; look for the new log line.

Register notes

PLAT-539, fixed on main, not deployed: the sidecar completion path now emits nothing when the turn is no longer tracked.