OpenClaw Test Heap Leaks

Use this skill for test-memory investigations. Do not guess from RSS alone when heap snapshots are available. Treat snapshot-name deltas as triage evidence, not proof, until retainers or dominators support the call.

For runtime fixes (e.g., closure leaks in long-running services like the gateway), see Validating runtime fixes below — that uses a dedicated harness, not the test-parallel snapshot machinery.

Workflow

1. Reproduce the failing shape first.

   • Match the real entrypoint if possible. For Linux CI-style unit failures, start with:
   • pnpm canvas:a2ui:bundle && OPENCLAW_TEST_MEMORY_TRACE=1 OPENCLAW_TEST_HEAPSNAPSHOT_INTERVAL_MS=60000 OPENCLAW_TEST_HEAPSNAPSHOT_DIR=.tmp/heapsnap OPENCLAW_TEST_WORKERS=2 OPENCLAW_TEST_MAX_OLD_SPACE_SIZE_MB=6144 pnpm test
   • Keep OPENCLAW_TEST_MEMORY_TRACE=1 enabled so the wrapper prints per-file RSS summaries alongside the snapshots.
   • If the report is about a specific shard or worker budget, preserve that shape.
   • Before you analyze snapshots, identify the real lane names from [test-parallel] start ... lines or pnpm test --plan. Do not assume a single unit-fast lane; local plans often split into unit-fast-batch-*.

2. Wait for repeated snapshots before concluding anything.

   • Take at least two intervals from the same lane.
   • Compare snapshots from the same PID inside the real lane directory such as .tmp/heapsnap/unit-fast-batch-2/.
   • Use .agents/skills/openclaw-test-heap-leaks/scripts/heapsnapshot-delta.mjs to compare either two files directly or the earliest/latest pair per PID in one lane directory.
   • If the helper suggests transformed-module retention, confirm the top entries in DevTools retainers/dominators before calling it solved.

3. Classify the growth before choosing a fix.

   • If growth is dominated by Vite/Vitest transformed source strings, Module, system / Context, bytecode, descriptor arrays, or property maps, treat it as likely retained module graph growth in long-lived workers.
   • If growth is dominated by app objects, caches, buffers, server handles, timers, mock state, sqlite state, or similar runtime objects, treat it as a likely cleanup or lifecycle leak.
   • If the names are ambiguous, stop short of a confident label and inspect retainers/dominators in DevTools for the top deltas.

4. Fix the right layer.

   • For likely retained transformed-module growth in shared workers:
   • Prefer timing and hotspot-driven scheduling fixes first. Check whether the file is already represented in test/fixtures/test-timings.unit.json and whether scripts/test-update-memory-hotspots.mjs should refresh the measured hotspot manifest before hand-editing behavior overrides.
   • Move hotspot files out of the real shared lane by updating test/fixtures/test-parallel.behavior.json only when timing-driven peeling is insufficient.
   • Prefer singletonIsolated for files that are safe alone but inflate shared worker heaps.
   • If the file should already have been peeled out by timings but is absent from test/fixtures/test-timings.unit.json, call that out explicitly. Missing timings are a scheduling blind spot.
   • For real leaks:
   • Patch the implicated test or runtime cleanup path.
   • Look for missing afterEach/afterAll, module-reset gaps, retained global state, unreleased DB handles, or listeners/timers that survive the file.

5. Verify with the most direct proof.

   • Re-run the targeted lane or file with heap snapshots enabled if the suite still finishes in reasonable time.
   • If snapshot overhead pushes tests over Vitest timeouts, fall back to the same lane without snapshots and confirm the RSS trend or OOM is reduced.
   • For wrapper-only changes, at minimum verify the expected lanes start and the snapshot files are written.

Heuristics

• Do not call everything a leak. In this repo, large unit-fast or unit-fast-batch-* growth can be a worker-lifetime problem rather than an application object leak.
• scripts/test-parallel.mjs and scripts/test-parallel-memory.mjs are the primary control points for wrapper diagnostics.
• The lane names printed by [test-parallel] start ... and [test-parallel][mem] summary ... tell you where to focus.
• When one or two files account for most of the delta and they are missing from timings, reducing impact by isolating them is usually the first pragmatic fix.
• When the same retained object families grow across multiple intervals in the same worker PID, trust the snapshots over intuition, then confirm ambiguous calls with retainer evidence.

Snapshot Comparison

• Direct comparison:
  • node .agents/skills/openclaw-test-heap-leaks/scripts/heapsnapshot-delta.mjs before.heapsnapshot after.heapsnapshot
• Auto-select earliest/latest snapshots per PID within one lane:
  • node .agents/skills/openclaw-test-heap-leaks/scripts/heapsnapshot-delta.mjs --lane-dir .tmp/heapsnap/unit-fast-batch-2
• Useful flags:
  • --top 40
  • --min-kb 32
  • --pid 16133

Read the top positive deltas first. Large positive growth in module-transform artifacts suggests lane isolation; large positive growth in runtime objects suggests a real leak. If the names alone do not settle it, open the same snapshot pair in DevTools and inspect retainers/dominators for the top rows before declaring root cause.

Validating runtime fixes (not test-memory)

The workflow above is for diagnosing Vitest worker memory growth. For validating that a runtime/closure fix actually releases captured state, use the dedicated harness:

• pnpm leak:embedded-run — runs scripts/embedded-run-abort-leak.ts. Loops N aborted runs in a function-shaped scope mimicking runEmbeddedAttempt, writes heap snapshots, and reports a PASS/FAIL verdict on retention growth using FinalizationRegistry for tracked-instance counting plus RSS delta.

Modes:

• closure-extracted (default) — production fix shape (helper at module scope).
• closure-inline — pre-fix shape (closure inside the runner scope). Use as a sensitivity check: if it passes you've broken the harness, not fixed a bug.
• synthetic-leak — deliberately retains via a module-level bucket. Use to confirm the harness can detect leaks before trusting a PASS on a real fix.

Snapshots land in .tmp/embedded-run-abort-leak/. Diff with the same script as above:

node .agents/skills/openclaw-test-heap-leaks/scripts/heapsnapshot-delta.mjs \
  .tmp/embedded-run-abort-leak/baseline-*.heapsnapshot \
  .tmp/embedded-run-abort-leak/batch-N-*.heapsnapshot --top 30

When fixing a different runtime leak, add a new harness alongside this one rather than retrofitting it. The fixture function should mimic the lexical scope of the function where the leak lives, not be a generic abort-loop.

Output Expectations

When using this skill, report:

• The exact reproduce command.
• Which lane and PID were compared.
• The dominant retained object families from the snapshot delta.
• Whether the issue is a likely real leak or likely shared-worker retained module growth, plus whether retainers/dominators confirmed it.
• The concrete fix or impact-reduction patch.
• What you verified, and what snapshot overhead prevented you from verifying.