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Resource limits prevent sandboxed code from running forever or exhausting host memory.

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CPU time limit

Set a CPU time budget in milliseconds. When exceeded, the execution exits with code 124. 
const runtime = new NodeRuntime({
  systemDriver: createNodeDriver(),
  runtimeDriverFactory: createNodeRuntimeDriverFactory(),
  cpuTimeLimitMs: 5000, // 5 seconds
});

const result = await runtime.exec("while (true) {}");
console.log(result.code); // 124
console.log(result.errorMessage); // "CPU time limit exceeded"
You can also override per execution: 
await runtime.exec("while (true) {}", {
  cpuTimeLimitMs: 1000, // tighter limit for this call
});

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Memory limit

Cap isolate memory in MB. Default is 128. 
const runtime = new NodeRuntime({
  systemDriver: createNodeDriver(),
  runtimeDriverFactory: createNodeRuntimeDriverFactory(),
  memoryLimit: 64, // 64 MB
});
Memory limits apply to Node runtimes only. Python runtimes run in a thread and do not support isolate-level memory caps.

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Payload limits

The bridge enforces size limits on data crossing the isolate boundary. Oversized payloads are rejected with ERR_SANDBOX_PAYLOAD_TOO_LARGE instead of exhausting host memory. 
const runtime = new NodeRuntime({
  systemDriver: createNodeDriver(),
  runtimeDriverFactory: createNodeRuntimeDriverFactory(),
  payloadLimits: {
    base64TransferBytes: 10 * 1024 * 1024, // 10 MB for file transfers
    jsonPayloadBytes: 5 * 1024 * 1024,     // 5 MB for JSON payloads
  },
});
Hosts can tune these limits within bounded safe ranges but cannot disable enforcement.

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Timing mitigation

High-resolution timers are frozen by default to mitigate timing side-channel attacks. 
// Default: frozen timers
const secure = new NodeRuntime({
  systemDriver: createNodeDriver(),
  runtimeDriverFactory: createNodeRuntimeDriverFactory(),
  timingMitigation: "freeze", // default
});

// Opt out for Node-compatible advancing clocks
const compatible = new NodeRuntime({
  systemDriver: createNodeDriver(),
  runtimeDriverFactory: createNodeRuntimeDriverFactory(),
  timingMitigation: "off",
});
In "freeze" mode:
  • Date.now() and performance.now() return frozen values within an execution
  • process.hrtime() and process.uptime() follow the hardened path
  • SharedArrayBuffer is unavailable
See the Security Model for more on timing hardening and trust boundaries.