perf(desktop): make session resume incremental (salvage of #62799) - #87522
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Follow-up to the #62799 salvage: Desktop sends both defer_history and omit_messages on a cold resume. Make explicit in the deferred branch that defer_history supersedes omit_messages — the single history read happens in the background hydration worker and the synchronous omit_messages read on the cold-resume default path is skipped entirely, so the transcript is never loaded twice for one resume.
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૮ >ﻌ< ა ci reviewran on cfcaee1 — docs(tui): document defer_history vs omit_messages precedenc
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This was referenced Aug 16, 2026
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Salvage of #62799 by @embwl0x — Desktop cold resume now returns its
session.resumeacknowledgement in <1ms by deferring the transcript read off the RPC path (measured 19x faster RPC-critical section on a real 1175-message production session).Infographic
What this is
Rebase/salvage of #62799 (perf(desktop): make session resume incremental) by @embwl0x onto current
main, with authorship preserved via cherry-pick. The original branch predates themethods_session.pysplit-out and several resume-path changes on main; the cherry-picks landed cleanly on top of them and the integration was re-verified against main's current resume machinery (profile-scoped DB ownership,assert_resume_safe,resolve_resume_session_id, deferred agent build, lazy watch resumes,omit_messages).Carried vs dropped
Carried (main lacks all of this):
defer_history: trueopt-in onsession.resume: gateway registers the runtime and returns the descriptor immediately (hydrating: true, emptymessages), then loads replay/display history on a background worker (_schedule_resume_hydrationintui_gateway/server.py).session.resume_progressevents (loading/complete/failed)._start_agent_buildgates on history readiness (resume_history_ready) and rechecks runtime ownership before building;_finalize_sessioncancels a waiting build on close.tests/tui_gateway/test_session_resume_db_ownership.pytest).defer_historyon cold resumes (use-session-actions), keeps REST as the transcript authority, and paints the bounded latest page as it arrives;hydrating?added toSessionResumeResponse.Dropped as redundant (already on main):
_schedule_agent_build).methods_session.pylayout is kept; the deferred branch slots in between the lazy/watch branch and the cold-resume default.Follow-up (own commit, not folded into contributor's):
docs(tui): explicit precedence comment —defer_historySUPERSEDESomit_messages; the single history read happens in the background worker, the synchronousomit_messagesread is skipped, so the transcript is never loaded twice for one resume.Validation
E2E against a real 297MB production
state.dbcopy (session20260812_162043_803c70, 1175 messages), SessionDB imported from this branch:Tests (targeted, this branch):
tests/test_tui_gateway_server.py+tests/tui_gateway/test_session_resume_db_ownership.py+tests/tui_gateway/test_protocol.py: 640 passed, 0 failedtests/test_tui_gateway_server.py tests/tui_gateway/sweep: 1049 passed, 2 skipped, 2 failed — both failures (test_cold_start_gil_stall,test_iso_certify_seam) reproduce identically on bareorigin/mainwith the same interpreter: pre-existing minimal-venv env gaps, not introduced here (verified by running the same test ids on detached origin/main).vitest run use-session-actions.test.tsx— 54 passed (includes the new bounded deferred-resume test);npm run check:lint— 0 errors (108 pre-existing warnings).Notes