perf(sessions): extend transcript eviction grace from 20s to 3min - #76792
perf(sessions): extend transcript eviction grace from 20s to 3min#76792arnohillen wants to merge 5 commits into
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Twenty seconds after navigating away from a settled task, its parsed transcript is freed and the next visit pays a full log read and re-parse. That turns ordinary task flipping into repeated multi-second reloads. Three minutes keeps recently viewed transcripts warm while still freeing memory for genuinely backgrounded sessions. Generated-By: PostHog Code Task-Id: 5d24ea17-aec0-4334-884e-c2639867e260
Reconciling a task with a log_url but no workspace path hydrated the full transcript into the store without arming the idle-session eviction that connectToTask and the cloud reconcile branch run, so logs-only residency was bounded by time alone. With the grace now at 3 minutes that gap would let a triage pass over many logs-only tasks stack unbounded transcripts; evict on this path like the others. Generated-By: PostHog Code Task-Id: 47cdc119-1c24-42ec-ac36-74c43cdd7f4e
Quantifies the store-side parse a task flip re-pays after eviction, which is the cost the longer grace avoids. Not run in CI (test globs only match *.test.*); rerun with pnpm vitest bench in packages/core. Generated-By: PostHog Code Task-Id: 47cdc119-1c24-42ec-ac36-74c43cdd7f4e
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Keeps the 3 min transcript eviction grace alongside the new resident background transcript cap from master. Generated-By: PostHog Desktop Task-Id: 341e450d-132c-42dd-abf2-52b22f99c3f6
🤖 CI report✅ Trunk lane — non-backend laneThis PR is assigned to the non-backend lane. It does not run backend Python tests and may merge in parallel with PRs in other lanes. |
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Approved.
Contained perf tuning to a desktop session-eviction timer plus a bounded-budget fix on the logs-only reconcile path, with new/updated tests covering both; no risky territory (no auth, billing, API, CI, deps, or data migration) so no independent assurance is required despite cross-team authorship.
- 👍 on the PR from greptile-apps[bot].
Gate mechanics and policy version
| Gate | Result | |
|---|---|---|
| prerequisites | ✓ | all clear |
| deny-list | ✓ | no deny categories matched |
| size | ✓ | 91L, 2F substantive, 125L/4F incl. docs/generated/snapshots — within ceiling |
| tier | ✓ | T1-agent / T1c-medium (125L, 4F, single-area, perf) |
| stamphog 2.0.0b4 | .stamphog/policy.yml @ 49406a2 · reviewed head 49406a2 |
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Ports PostHog/code#3978 onto
products/desktop/after the desktop import (the code repo'smainis frozen). Original commits and authorship are preserved viagit am.Problem
Part 3 of the task re-open latency work (see #76788, #76791). A settled task's parsed transcript is evicted 20 seconds after its view unmounts. Anyone flipping between a few tasks slower than that pays a full disk read plus a three-pass re-parse of the log on every return, which is seconds of main-thread work for large transcripts.
Changes
SESSION_EVENT_EVICT_GRACE_MSgoes from 20s to 3 minutes. Eligibility is unchanged: only disconnected, settled sessions with no pending prompt are evicted, and the eviction/rehydration machinery is untouched.The memory tradeoff is bounded: only transcripts viewed in the last 3 minutes stay warm, and everything else about the residency system (rehydrate on return, retry after failed reads) behaves exactly as before.
How did you test this code?
products/desktop/:pnpm install --frozen-lockfile,pnpm typecheck(24/24 packages), and the full@posthog/corevitest suite (247 files, 2970 tests passing).Automatic notifications
Docs update
Not applicable (desktop app internals),
skip-inkeep-docslabel applied.🤖 Agent context
Autonomy: Human-driven (agent-assisted)
This PR is a port of PostHog/code#3978, recreated here by PostHog Code following the /porting-code-prs skill: patch series applied with
git am --directory=products/desktop/(original authorship and commit messages preserved; no lockfile changes in this one). Part 3 of 3 ported PRs on task re-open latency.Created with PostHog Code