Migrated sessions imported by pre-0.40.0 migrator never heal on ≥0.40.1: turn-clock reset collides new turns with imported transcript (live UI shows only old content)

Summary

Sessions imported from legacy Python kimi-cli by a pre-0.40.0 migrator carry no turn records in wire.jsonl (only metadata + context.append_message). PR #3446 (shipped in 0.40.0) fixed the migration writer to synthesize turn.prompt/turn.ended for new migrations, and 0.40.0 briefly shipped an in-place repair (repair-imported.ts) for sessions already broken by the old migrator. PR #3467 (0.40.1) removed that repair path entirely. As a result, on any ≥0.40.1 build (including current 0.41.0), previously migrated sessions stay broken forever: every new turn is fully processed by the backend but never rendered in the Web UI.

Reproduction

1. Have a session imported by the old migrator (state.json: custom.imported_from_kimi_cli=true, kimi_cli_wire_protocol="1.10"; wire.jsonl contains no turn.prompt/turn.ended records).
2. Open it in the Web UI (0.41.0) and send any message.
3. Observe: neither the user bubble nor the assistant reply appears. The sidebar title/activity updates correctly (separate channel).

Backend is healthy throughout: wire.jsonl records prompt.accepted, assistant content.part text, turn.ended, prompt.completed. Nothing is lost — it is a live-transcript rendering defect.

Evidence from an affected production session (redacted)

{"type":"metadata","protocol_version":"1.5","created_at":1787620582752}
{"type":"context.append_message","message":{"role":"user","content":[{"type":"text","text":"<imported legacy user text, redacted>"}],"toolCalls":[]}}

// … 50 imported legacy records total, all shaped like the line above:
// no "agentId", no "time", and no turn records anywhere in the imported segment …

{"type":"turn.prompt","agentId":"main","input":[{"type":"text","text":"hello"}],"origin":{"kind":"user"},"promptId":"msg_01M1SC9KEB8TXWA1WQ0DGXMSV2","time":1788631895605}
{"type":"turn.ended","agentId":"main","turnId":0,"reason":"completed","durationMs":18779,"time":1788631914385}
{"type":"turn.prompt","agentId":"main","input":[{"type":"text","text":"hello"}],"origin":{"kind":"user"},"promptId":"msg_01M1SCAEWZWXDV2A9RRH5NZHKN","time":1788631923623}
{"type":"turn.ended","agentId":"main","turnId":1,"reason":"completed","durationMs":5985,"time":1788631929609}

Note the turn clock restarting at turnId 0 for the first post-import turn.

Root cause (verified against 0.38.0 source and production wire data)

• On resume, the engine's turn clock (turnKey.nextTurnId) is rebuilt only from turn.prompt / context.append_loop_event records. Imported wires contain none, so the clock restarts at 0.
• The transcript backfill numbers all imported messages sequentially as turns t0..t(k-1). New live turns get turnId 0, 1, … and are projected as t0, t1 — colliding with imported turns at the top of history, outside the default last-N-turns window.
• healEndedTurns then processes only the terminal ordinals {0,1} and lets the imported snapshot win, so the live store converges back to "old content only" after every turn. This repeats on every send until a server restart forces a cold rebuild (which renumbers sequentially and displays correctly until the next send).

Why ≥0.40.1 cannot recover

• #3446 only fixes future migrations.
• The 0.40.0-only in-place repair (which preserved live history added after import) was deleted by #3467. There is currently no code path that repairs an already-imported session, so upgrading never heals existing installs.

Requested fix

Restore a repair path for sessions imported by pre-0.40.0 migrators, e.g.:

• a one-shot startup/resume check: custom.imported_from_kimi_cli=true and wire lacks turn records → synthesize turn structure in place (the #3446 buildTurnRecords logic is reusable), preserving any live turns added after import; or
• an explicit kimi migrate --repair-imported command.

Environment

• kimi-code 0.41.0 (win32-x64), Web UI served by the app server.
• Session imported 2026-08-25 by migrator 0.1.1 from Python kimi-cli 1.49.

References

• PR #3446 (writer fix, 0.40.0): https://github.com/MoonshotAI/kimi-code/pull/3446
• PR #3467 (removed the in-place repair, 0.40.1): https://github.com/MoonshotAI/kimi-code/pull/3467

Start with the removed repair-imported.ts path and the buildTurnRecords logic from PR #3446, then trace the session startup/resume flow that rebuilds turnKey.nextTurnId. Reproduce with an affected wire.jsonl containing context.append_message records but no turn records. Done means pre-0.40.0 imports are repaired without losing post-import turns, and new messages render instead of colliding with imported turns.