fix(execution): cap isolate memory at 128MB and recycle workers every 200 executions

[waleedlatif1]

Summary

• Revert isolate memoryLimit from 256MB → 128MB in isolated-vm-worker.cjs (both executeCode and executeTask). 256MB was added in improvement(sandbox): upgrade pptx/docx/pdf bootstrap with image helpers, MIME guards, and 256 MB isolate limit #4505 for doc generation; production data (48h) shows zero Reached memory limit errors, so the headroom was unused. Error messages updated accordingly.
• Lower MAX_EXECUTIONS_PER_WORKER default from 500 → 200 in both apps/sim/lib/core/config/env.ts (env schema default) and apps/sim/lib/execution/isolated-vm.ts (fallback). Workers recycle 2.5× more aggressively. All 89 worker retirements in the last 48h hit the 500 ceiling, and MemoryTelemetry shows native context count climbing to 475 with RSS peaks of 15.6GB — only process.kill() reclaims that native memory, so faster recycling caps steady-state RSS.
• Both values remain env-overridable (IVM_MAX_EXECUTIONS_PER_WORKER).

Why

Production app task triggered sim-production-us-east-1-app-task-high-memory alarm, climbing from 1GB → 13.7GB in 30 minutes after the v0.6.72 deploy. Math (13GB ÷ 256MB ≈ 50 isolates) + telemetry (externalMB 11.7GB peak, nativeContexts 475) point at native memory accumulating in the parent across executions faster than workers recycle.

Note on chosen value (200)

Initial fix used 100 (5× reduction). Raised to 200 after weighing tradeoffs:

• 200 still cuts steady-state native memory accumulation by 2.5× vs the prior 500
• Less spawn churn under burst load
• Defensible range from telemetry was 50–250; 200 is the conservative end with most headroom for tail-latency cost
• Env override (IVM_MAX_EXECUTIONS_PER_WORKER) lets us drop to 100 without a code change if post-deploy telemetry shows RSS still climbing

Type of Change

• Bug fix

Testing

Tested manually. Spawn-rate impact at 200 is negligible: peak 74/hr → ~185/hr across the 4-worker pool, distributed via retiring flag (no in-flight interruption).

Checklist

• Code follows project style guidelines
• Self-reviewed my changes
• Tests added/updated and passing
• No new warnings introduced
• I confirm that I have read and agree to the terms outlined in the Contributor License Agreement (CLA)

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1 Skipped Deployment

Project	Deployment	Actions	Updated (UTC)
docs	Skipped		May 10, 2026 1:22am

[cursor]

PR Summary

Medium Risk
Touches the isolated execution sandbox and worker lifecycle limits, which can change runtime behavior and cause more OOMs or process churn under load. Changes are small but affect a performance/stability-critical path.

Overview
Lowers isolated-vmmemoryLimit from 256MB → 128MB for both code and task execution workers, and updates the associated memory-limit error messaging.

Reduces the default IVM_MAX_EXECUTIONS_PER_WORKER / MAX_EXECUTIONS_PER_WORKER from 500 → 200 (still env-overridable), causing worker processes to retire and respawn more frequently to curb memory accumulation.

^{Reviewed by Cursor Bugbot for commit eb6068b. Configure here.}

[greptile-apps]

Greptile Summary

This PR makes two targeted production fixes to address a memory alarm triggered by native heap accumulation in the isolated-vm worker pool: it reverts the isolate memoryLimit from 256 → 128 MB (production telemetry shows zero memory-limit errors, confirming the headroom was unnecessary) and lowers MAX_EXECUTIONS_PER_WORKER from 500 → 200 so workers recycle 2.5× more often, capping steady-state RSS.

• isolated-vm-worker.cjs: memoryLimit reduced to 128 MB in both executeCode and executeTask; error messages updated to match.
• env.ts + isolated-vm.ts: Default and fallback for MAX_EXECUTIONS_PER_WORKER lowered to 200 in both places, keeping them in sync. The env override IVM_MAX_EXECUTIONS_PER_WORKER remains available for further tuning without a code deploy.

Confidence Score: 5/5

Safe to merge — all three files are consistent with each other and the changes are backed by 48h of production telemetry.

The changes are narrow and mutually consistent: the env schema default, the in-code fallback, the isolate memory cap, and the error messages all tell the same story. The 256 → 128 MB revert is validated by zero memory-limit errors in production. The 500 → 200 recycling threshold directly addresses the observed RSS growth (nativeContexts climbing to 475, RSS peaking at 15.6 GB). Both values remain env-overridable, so further tuning requires no code change.

No files require special attention.

Important Files Changed

Filename	Overview
apps/sim/lib/execution/isolated-vm-worker.cjs	Reverts memoryLimit from 256 → 128 MB in both executeCode and executeTask; error messages updated to match. Both sites changed consistently.
apps/sim/lib/core/config/env.ts	Single-line change lowering IVM_MAX_EXECUTIONS_PER_WORKER default from 500 → 200; consistent with isolated-vm.ts fallback.
apps/sim/lib/execution/isolated-vm.ts	Fallback for MAX_EXECUTIONS_PER_WORKER lowered from 500 → 200, matching the env.ts schema default exactly.

Flowchart

%%{init: {'theme': 'neutral'}}%%
flowchart TD
A[New execution request] --> B{Worker available?}
B -- yes --> C[Assign to worker]
B -- no --> D[Queue / spawn new worker]
C --> E[Create ivm.Isolate\nmemoryLimit: 128 MB]
E --> F[Execute code / task]
F --> G{Memory exceeded?}
G -- yes --> H[Return MemoryLimitError\n'128 MB exceeded']
G -- no --> I[Return result]
I --> J[Increment worker.execCount]
J --> K{execCount >= 200?}
K -- yes --> L[Mark worker retiring\nprocess.kill on idle]
K -- no --> M[Worker stays in pool]
L --> N[Spawn replacement worker]

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[waleedlatif1]

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✅ Bugbot reviewed your changes and found no new issues!

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[waleedlatif1]

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[waleedlatif1]

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✅ Bugbot reviewed your changes and found no new issues!

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