fix(artifacts): one parsed sidecar per project — the read side of the #318 OOM fix - #335
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…318 OOM fix Destin's live app died 2026-08-27 01:01:56 after 12h32m (and 2026-08-23 after 60h): V8 heap OOM at 2,801/2,825 MB. The core dump held 477 parsed copies of youcoded-dev/.youcoded/artifacts.json (6.4 MB, 21,311 versions) ≈ 3.0 GB. PR #318 queued the sidecar WRITER; all 20 read sites stayed unguarded, and one Edit costs ~11 full parses (LIST_SESSION, artifacts:get per visible card, check-existence, the watcher's id map, every open tab at startup). readSidecarShared: one parsed copy per project, validated by size + mtime, concurrent callers share one in-flight parse, a committed writeSidecar seeds it with the object just written, idle copies drop after 60 s. Read-only handlers use it; the five mutate-and-write paths keep the private readSidecar. casWrite: the CAS comparand is read from a 4 KB head probe (regex, no parse) with a whole-file fallback — the old extractor JSON.parsed 6.4 MB to read one timestamp on every write. Reproduced against Destin's real file (now 6.9 MB / 22,017 versions), one process, --max-old-space-size=2800: old N=60: 60 parses, peak heap 1,188 MB old N=477: FATAL ERROR: Ineffective mark-compacts near heap limit new N=477: 1 parse, peak heap 25 MB Guards: tests/artifacts/sidecar-cache.test.ts (burst = one parse, seeded after write, external change re-parses, corrupt backed up once, idle drop), cas-write.test.ts (head probe, fallback), artifact-store.test.ts (zero JSON.parse on the CAS path). verify.sh green: tsc, full suite, knip, eslint, ast-grep. Investigation: docs/active/investigations/2026-08-27-artifacts-sidecar-oom-crash.md The rest of the bug class (transcript replay, Android's missing write queue) is specced and paused: docs/active/specs/2026-08-27-paged-history-and-read-hardening-design.md Co-Authored-By: Claude Fable 5 <noreply@anthropic.com> Claude-Session: https://claude.ai/code/session_01H7YhBJVwWP2iwohNEUSmyY
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docs(artifacts): the shared sidecar read (PR #335) — depth paragraph under Concurrency
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Destin's live app died 2026-08-27 01:01:56 after 12h32m (and 2026-08-23 after
60h): V8 heap OOM at 2,801/2,825 MB. The core dump held 477 parsed copies of
youcoded-dev/.youcoded/artifacts.json (6.4 MB, 21,311 versions) ≈ 3.0 GB.
PR #318 queued the sidecar WRITER; all 20 read sites stayed unguarded, and
one Edit costs ~11 full parses (LIST_SESSION, artifacts:get per visible card,
check-existence, the watcher's id map, every open tab at startup).
readSidecarShared: one parsed copy per project, validated by size + mtime,
concurrent callers share one in-flight parse, a committed writeSidecar seeds
it with the object just written, idle copies drop after 60 s. Read-only
handlers use it; the five mutate-and-write paths keep the private readSidecar.
casWrite: the CAS comparand is read from a 4 KB head probe (regex, no parse)
with a whole-file fallback — the old extractor JSON.parsed 6.4 MB to read one
timestamp on every write.
Reproduced against Destin's real file (now 6.9 MB / 22,017 versions), one
process, --max-old-space-size=2800:
old N=60: 60 parses, peak heap 1,188 MB
old N=477: FATAL ERROR: Ineffective mark-compacts near heap limit
new N=477: 1 parse, peak heap 25 MB
Guards: tests/artifacts/sidecar-cache.test.ts (burst = one parse, seeded
after write, external change re-parses, corrupt backed up once, idle drop),
cas-write.test.ts (head probe, fallback), artifact-store.test.ts (zero
JSON.parse on the CAS path). verify.sh green: tsc, full suite, knip, eslint,
ast-grep.
Investigation: docs/active/investigations/2026-08-27-artifacts-sidecar-oom-crash.md
The rest of the bug class (transcript replay, Android's missing write queue)
is specced and paused: docs/active/specs/2026-08-27-paged-history-and-read-hardening-design.md
🤖 Generated with Claude Code
https://claude.ai/code/session_01H7YhBJVwWP2iwohNEUSmyY