84 lines
4.9 KiB
Markdown
84 lines
4.9 KiB
Markdown
# Code Runtime
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The code-execution seam — a [capability seam](../rfc/implemented/architecture/2026-06-13-capability-seams.md) whose interface ([dsh-code-runtime](../../packages/code-runtime/code-runtime), `ctx.codeRuntime`) runs one model-written program against host-provided async bindings and reports what it printed and returned. Code execution is **one optional capability**, not part of the agent-loop spine — so its vocabulary lives here, not in [core.md](core.md). Backends differ by execution substrate and source language, both readonly descriptors on the service; the worker-thread backend and the tool-registry consumer (Code Mode) are specified in the [Code Mode RFC](../rfc/implemented/feature/2026-06-15-code-mode.md).
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Source: [`packages/code-runtime/code-runtime/src/types.ts`](../../packages/code-runtime/code-runtime/src/types.ts)
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## The run: request in, result out
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A `CodeRunRequest` carries **everything the runtime acts on** — per the "explicit > implicit at package seams" rule, defaulting (time budgets, output caps) is the implementation's validated config, never a hidden `??` inside `run()`:
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```ts type-equiv
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interface CodeRunRequest {
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/**
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* The program source, in the runtime's {@link ../index.ts | language}. It
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* runs as the body of an async function: top-level `await` and `return`
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* are available, and the completion value becomes
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* {@link CodeRunResult.value}.
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*/
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program: string
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/** Host functions exposed to the program, one global object per namespace. */
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bindings: CodeBindingNamespace[]
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/**
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* Abort the run: the runtime stops the program (hard, even mid-loop) and
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* resolves with a {@link CodeRunFailure} of kind `'abort'`. In-flight
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* binding calls are the CALLER's to settle — the runtime only stops asking.
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*/
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signal?: AbortSignal
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}
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```
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The result reports an error as a **field**, never a rejection of `run()` — reporting a failed program is the caller's job, not an exception path (mirroring `BashExecutor.run`'s resolve-on-failure contract):
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```ts type-equiv
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interface CodeRunResult {
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/**
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* The program's completion value (its top-level `return`), when it ran to
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* completion and the value survived the runtime's serialization boundary;
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* a non-transferable value is replaced by a string rendering, and a failed
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* or value-less run leaves this absent.
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*/
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value?: unknown
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/** Text the program emitted, in order (capped by the implementation). */
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logs: string[]
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/** Present iff the run failed; see {@link CodeRunFailure} for the taxonomy. */
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error?: CodeRunFailure
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}
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```
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## Bindings: host functions as program globals
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Each `CodeBindingNamespace` becomes one global object of async callables inside the program (the Code Mode consumer passes one: `tools`). Arguments and resolutions must be structured-cloneable — a runtime may bridge calls across a serialization boundary — and a runtime treats binding names as hostile input (`__proto__` is an ordinary own property, never a prototype collision):
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```ts type-equiv
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interface CodeBindingNamespace {
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/** The global identifier the program sees (must be a valid JS identifier). */
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global: string
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/** The callable members, keyed by the exact name the program calls. */
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functions: Record<string, CodeBindingFunction>
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}
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```
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```ts type-equiv
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type CodeBindingFunction = (args: unknown) => Promise<unknown>
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```
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## Captured output and the failure taxonomy
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Logs are plain strings in emission order. The runtime captures the program's console and stream output, but channel and console-method metadata are not part of the seam because consumers render only the text. Implementations cap the aggregate output and mark truncation in-band.
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Failure kinds are **orthogonal outcomes reported independently** (per [defensive-patterns](../defensive-patterns.md)): a budget expiry is not an exception, an abort is not a timeout, and a substrate death (e.g. OOM) is neither:
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```ts type-equiv
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interface CodeRunFailure {
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/** The failure class (see the interface doc for each kind's meaning). */
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kind: 'exception' | 'timeout' | 'abort' | 'worker-exit'
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/** Human-readable detail, suitable for feeding back to a model to self-correct. */
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message: string
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}
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```
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## The service
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`CodeRuntime` (`ctx.codeRuntime`, abstract — defined in [`packages/code-runtime/code-runtime/src/index.ts`](../../packages/code-runtime/code-runtime/src/index.ts)) is `run(request)` plus two readonly descriptors: `language` (what the program must be written in — `'typescript'` is the well-known value; a consumer generating language-specific presentation switches on it and fails loud on one it cannot present) and `isolation` (the execution substrate — `'worker-thread'`, `'process'`, `'container'`; a diagnostic label, **not a security claim**). Implementations must keep runs isolated from each other (no cross-run state) and dispose to quiescence: in-flight runs are terminated and awaited before teardown completes.
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