fix(sdk): count cron turns as replay turn boundaries - #3605
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RealKai42 merged 1 commit intoSep 7, 2026
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Resuming a session dominated by cron-fired turns mounted an unbounded transcript: limitAgentReplayByTurns only counted human-typed prompts as turn boundaries, so the replay limit never engaged (10,478 records for 11 'turns' on an affected session). The mounted transcript made every render frame O(total lines), starving the event loop during streaming and collapsing client-side drain throughput. Treat cron_job and cron_missed replay records as turn boundaries, matching the TUI transcript window's own boundary rule.
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Related Issue
No linked issue — reported via internal user feedback and root-caused from the affected session data.
Problem
After resuming a session whose history is dominated by cron-fired turns, response streaming collapses to 30–50 tok/s in the TUI even though the server streams at ~200 tok/s, and it reproduces on every resume of that session (a fresh session on the same machine streams at full speed).
Root cause:
limitAgentReplayByTurnsonly counted human-typed prompts as turn boundaries —cron_job/cron_missedrecords were not turns. On the affected session (4,280 cron turns vs 63 real user turns) the "last 11 turns" replay fetch therefore returned 10,478 records (~9 MB, ~45% of the whole history), all of which the TUI mounts and keeps mounted for the process lifetime. Every render frame then walks ~100k mounted transcript lines; during streaming (20 fps flush) that saturates the event loop on modest hardware, so the client cannot drain the socket and the measured server-decode window stretches (the debug split attributes this starvation to "server", which is misleading).Verified against the real session data: print mode (no TUI) streams at full speed; the mock-server drain of 4,000 tokens takes 10 ms once the transcript is bounded.
What changed
packages/node-sdk/src/replay.ts: treatcron_jobandcron_missedreplay records as turn boundaries. This mirrors the TUI transcript window's own boundary rule (CronMessageComponentis already a fold-segment boundary there). The resumed replay on the affected session drops from 10,478 to 137 records; end-to-end resume output shrinks from 31 MB to 351 KB.packages/node-sdk/test/replay.test.ts(new): bounds replay volume when cron turns dominate (failed before the fix), treatscron_missedas a boundary, verifies injection bursts do not shrink the window, and pins the existing user-turn semantics.Validation: node-sdk 138 tests, apps/kimi-code 2452 TUI tests, typecheck, oxlint — all green.
Checklist
/approve).gen-changesetsskill, or this PR needs no changeset.gen-docsskill, or this PR needs no doc update.