Code Execution

Execution state machine and the host’s contract with environments

This page collects the execution-related shapes and state machine that sit between the host and an environment module.

ExecutionInput

interface ExecutionInput {
  eid: number;
  code: string;
  envConfig: Record<string, unknown>;
}

What the host hands to EnvironmentModule.execute:

• eid is the execution id. It is the same number as the process pid. Treat it as opaque; just feed it back to every binding.
• code is exactly what the client submitted via POST /processes.
• envConfig is a generic bag of environment-level configuration set by the host. The host guarantees at minimum a timeoutMs key, resolved against DEFAULT_EXECUTION_TIMEOUT_MS (30000) before dispatch. The environment should treat this as authoritative and pluck the values it recognises.

Host-side States

The host’s ProcessService runs the public-facing state machine. From the API’s perspective, a process is always in one of four states:

• idle: Not executing. Either pre-run, or post-run with an exit state.
• queued: Accepted, waiting for the environment.
• running: Environment is executing the code.
• terminating: A kill is in flight.

Environment-reported States

EnvironmentBindings.setState(eid, data) accepts only the environment states:

const EXECUTION_STATES = ["queued", "running"] as const;
type ExecutionState = "queued" | "running";

The host maps these to its own state machine. idle and terminating are host-only; the environment never reports them.

Exit States

const EXECUTION_EXIT_STATES = [
  "failed",
  "success",
  "timeout",
  "canceled",
] as const;
type ExecutionExitState = "failed" | "success" | "timeout" | "canceled";

The environment’s execute returns one of these. The host stores it as process.exitState:

Exit	When
success	The code completed normally.
failed	The code threw, or the environment couldn’t run it. process.error is populated.
timeout	The environment terminated the execution because it exceeded envConfig.timeoutMs.
canceled	The host called kill(eid), or the environment is shutting down.

The host also accepts null as a transient pre-execution value, but environment code never returns null.

Timeout Contract

The host hands the environment a timeoutMs within envConfig and expects the environment to enforce it. The host does not run a wall clock of its own; if the environment lies about exit state, the process record lies too.

• The bundled typescript-ivm enforces the timeout by racing the isolate against a setTimeout, then disposing the isolate.
• Custom environments are free to use any mechanism, process group signals, worker thread interrupts, whatever fits the runtime.

Cancellation Contract

EnvironmentModule.kill(eid) is the only way the host asks for cancellation. The environment should:

1. Stop whatever is executing for eid promptly.
2. Resolve the outstanding execute(eid) promise with "canceled".
3. Be safe to call with an eid it does not know about.

There is no “soft kill” channel. If you need cooperative shutdown for long-running tools, model it inside the runtime (e.g. an AbortController exposed to user code).

What the host owns

Concern	Owner
Generating eid / pid	Host (ProcessService.createPid).
Default timeoutMs	Host (DEFAULT_EXECUTION_TIMEOUT_MS).
stdout/stderr decoding	Host (StringDecoder("utf8") per stream).
Output merging	Host (Object.assign(process.output, data)).
state transitions to idle / terminating	Host.
Routing tool invocations to adapters	Host (ModuleService.invoke).

What the environment owns

Concern	Owner
Transpiling / parsing input.code	Environment.
Running the code in a sandbox	Environment.
Enforcing timeoutMs	Environment.
Reporting queued / running / exit state	Environment.
Emitting stdout, stderr, output	Environment.
Surfacing tool calls from user code back through bindings.invokeTool	Environment.