perf(agent): skip session JSONL sanitize when file is unchanged - #76791
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Every reconnect re-runs sanitizeSessionJsonl, which reads and JSON-parses every line of the native Claude transcript. For long sessions that file reaches tens of MB, adding seconds to each resume. Remember the file stat of the last clean pass and skip the read when it matches. The SDK only appends, which changes size and mtime, so any real change forces a re-parse; staleness only ever causes extra work, not a skipped heal. Generated-By: PostHog Code Task-Id: 5d24ea17-aec0-4334-884e-c2639867e260
Same swap as the conversation caches in #3976: lru-cache v11 is already a workspace dependency, so the hand-rolled capped Map goes away. Generated-By: PostHog Code Task-Id: 5d24ea17-aec0-4334-884e-c2639867e260
The healed path recorded the stat of the renamed file, taken after the rename, so bytes appended by a concurrent writer in that window would have been certified clean and skipped by every later pass. Record the tmp file's stat instead: rename preserves it, and any post-rename append already mismatches it, forcing a re-parse. Generated-By: PostHog Code Task-Id: 47cdc119-1c24-42ec-ac36-74c43cdd7f4e
Not run in CI (test globs only match *.test.*). Numbers land in the PR description; rerun with pnpm vitest bench in packages/agent. Generated-By: PostHog Code Task-Id: 47cdc119-1c24-42ec-ac36-74c43cdd7f4e
Regenerated for the new packages/agent dependency; same resolution the source PR locked (11.2.5). Generated-By: PostHog Code Task-Id: 96e133e1-f570-432f-b8ff-bce4202f5b7f
arnohillen
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This was referenced Aug 3, 2026
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Reviews (1): Last reviewed commit: "chore(agent): add lru-cache to the agent..." | Re-trigger Greptile |
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This PR hasn't seen activity in a week! Should it be merged, closed, or further worked on? If you want to keep it open, please remove the |
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React Doctor found no issues in the changed files. 🎉 Reviewed by React Doctor for commit |
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dmarticus
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Aug 20, 2026
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/trunk merge |
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Ports PostHog/code#3977 onto
products/desktop/after the desktop import (the code repo'smainis frozen). Original commits and authorship are preserved viagit am.Problem
Part 2 of the task re-open latency work (see #76788). Every agent reconnect runs
sanitizeSessionJsonlover the native Claude transcript (~/.claude/projects/.../<sessionId>.jsonl): a full read plus aJSON.parseper line. These files grow to tens of MB on long sessions, so every re-open of a cold task pays seconds of parse work before the session can resume, even when the file was already verified clean moments earlier.Changes
lru-cache, already a workspace dependency), and return early when the current stat matches.Compared to the source PR, the only monorepo-specific change is the lockfile: instead of carrying the source
pnpm-lock.yamlhunk blindly, theproducts/desktop/pnpm-lock.yamlimporter entry was regenerated for the newpackages/agentdependency (same resolution,lru-cache@11.2.5).How did you test this code?
products/desktop/:pnpm install --frozen-lockfile,pnpm typecheck(24/24 packages), and the full@posthog/agentvitest suite (100 files, 1771 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#3977, 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), source lockfile hunk excluded and re-derived against the monorepo lockfile instead. Part 2 of 3 ported PRs on task re-open latency.Created with PostHog Code