Code Runtime
The code-execution seam — a capability seam whose Service Definition (dsh-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. Backends differ by execution substrate and source language, both readonly descriptors on the service; the worker-thread Service Provider and tool-registry Consumer are specified by the Code Mode foundation and typed-return contract.
Source: packages/code-runtime/code-runtime/src/types.ts
The run: request in, result out
A CodeRunRequest carries everything the runtime acts on — per the "explicit > implicit at package boundaries" rule, defaulting (time budgets, output caps) is the implementation's validated config, never a hidden ?? inside run():
/**
* One run: the program source plus everything the runtime acts on. Per the
* explicit-over-implicit convention, defaulting (time budgets, output caps)
* is the implementation's validated config — a request carries no optional
* tuning knobs for a hidden `??` to fill in.
*/
interface CodeRunRequest {
/**
* The program source, in the runtime's {@link ../index.ts | language}. It
* runs as the body of an async function: top-level `await` and `return`
* are available, and the completion value becomes
* {@link CodeRunResult.value}.
*/
program: string
/** Host functions exposed to the program, one global object per namespace. */
bindings: CodeBindingNamespace[]
/**
* Abort the run: the runtime stops the program (hard, even mid-loop) and
* resolves with a {@link CodeRunFailure} of kind `'abort'`. In-flight
* binding calls are the CALLER's to settle — the runtime only stops asking.
*/
signal?: AbortSignal
}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 (matching ShellExecutor.run's resolve-on-failure contract):
/**
* The outcome of one run. An error is a FIELD on a resolved result, never a
* rejection of `run()` — reporting a failed program is the caller's job, not
* an exception path.
*/
interface CodeRunResult {
/**
* The program's completion value (its top-level `return`), when it ran to
* completion and the value crossed the runtime's lossless-JSON boundary.
* Invalid or over-limit completions fail the run instead of substituting a
* rendered string; a failed or value-less run leaves this absent.
*/
value?: CodeJsonValue
/** Text the program emitted, in order, bounded only as part of the outer result. */
logs: string[]
/** Present iff the run failed; see {@link CodeRunFailure} for the taxonomy. */
error?: CodeRunFailure
}Bindings: host functions as program globals
Each CodeBindingNamespace becomes one global object of async callables inside the program (the Code Mode consumer passes one: tools). Arguments and resolutions must be lossless JSON and cross without a seam-level byte cap; the runtime may bridge them through structured clone. A namespace may declare a program-visible error class without making the runtime know the consumer's names: the runtime injects the real constructor and turns rejected calls into its instances. A runtime also treats binding names as hostile input (__proto__ is an ordinary own property, never a prototype collision):
/**
* Program-visible typed rejection for one binding namespace. The runtime
* injects a real error constructor under `name`; rejected member calls become
* its instances and expose the exact member name through
* `memberNameProperty`. Both strings are runtime data rather than knowledge
* of a particular consumer such as Code Mode.
*/
interface CodeBindingErrorClass {
/** Constructor global and resulting `Error.name`; same portable identifier rule as {@link CodeBindingNamespace.global}. */
name: string
/**
* Non-empty own property for the member name. The portable exclusion set is
* `RESERVED_ERROR_MEMBERS` plus dunder-form names (`__x__`, non-empty
* middle), enforced identically by every backend; any other name —
* identifiers or not — is accepted everywhere.
*/
memberNameProperty: string
}/**
* A named group of {@link CodeBindingFunction}s the runtime exposes to the
* program as one global object (e.g. `tools`). Function names are arbitrary
* strings — a runtime must treat names like `__proto__` or `constructor` as
* ordinary own properties (null-prototype construction), never as prototype
* collisions.
*/
interface CodeBindingNamespace {
/**
* The global identifier the program sees. Must match the LANGUAGE-PORTABLE
* identifier subset `[A-Za-z_][A-Za-z0-9_]*` and no language's reserved
* words, so the same namespace list works against every backend regardless
* of `language` — a JS-only spelling like `$tools` is rejected by design,
* not just by the Python backend. Names that satisfy the identifier rule but
* name a backend-owned slot (`RESERVED_BINDING_GLOBALS`, e.g. `console`,
* `__dsh_main__`) are also refused everywhere; see its declaration for the
* exact set and why each entry is reserved.
*/
global: string
/** The callable members, keyed by the exact name the program calls. */
functions: Record<string, CodeBindingFunction>
/** Optional program-visible typed rejection contract for this namespace. */
errorClass?: CodeBindingErrorClass
}/** A lossless JSON value transferable through the dependency-light Service Definition. */
type CodeJsonValue = null | boolean | number | string | CodeJsonValue[] | { [key: string]: CodeJsonValue }/**
* One host-side function exposed to the program as an async callable. The
* runtime bridges calls to it (possibly across a serialization boundary), so
* `args` and the resolution value MUST be lossless JSON. A runtime rejects a
* lossy or non-cloneable value with a descriptive error rather than corrupting
* the run. No seam-level byte cap applies to a binding resolution. A rejection
* of this function surfaces inside the program as a rejection of the
* corresponding call.
*/
type CodeBindingFunction = (args: unknown) => Promise<CodeJsonValue>Captured output and the failure taxonomy
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 serialized outer log-array plus completion-value or failure-message payload; fixed result-envelope syntax and consumer presentation whitespace are not part of that variable-payload ledger. Overflow is an explicit failure rather than in-band value substitution.
Failure kinds are orthogonal outcomes reported independently (per defensive-patterns): a budget expiry is not an exception, an abort is not a timeout, and a substrate death (e.g. OOM) is neither:
/**
* Why a run failed. The kinds are orthogonal outcomes reported independently
* (per docs/defensive-patterns.md): a budget expiry is not an exception, an
* abort is not a timeout, and a substrate death is neither.
*
* - `'exception'` — the program threw or failed to parse/transform.
* - `'timeout'` — an implementation-owned budget expired; the message says which.
* - `'abort'` — {@link CodeRunRequest.signal} fired.
* - `'worker-exit'` — the execution substrate died without settling (e.g. OOM).
* - `'invalid-output'` — the completion value was not lossless JSON.
* - `'output-limit'` — the serialized outer logs/value/diagnostic exceeded the configured cap.
*/
interface CodeRunFailure {
/** The failure class (see the interface doc for each kind's meaning). */
kind: 'exception' | 'timeout' | 'abort' | 'worker-exit' | 'invalid-output' | 'output-limit'
/** Human-readable detail, suitable for feeding back to a model to self-correct. */
message: string
}The service
CodeRuntime (ctx.codeRuntime, abstract — defined in packages/code-runtime/code-runtime/src/index.ts) is run(request) plus two readonly descriptors: language (what the program must be written in — 'typescript' and 'python' are the well-known values, those dsh-tools presents, and only 'typescript' has a published backend; 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.
Cordis API
Generated from source by scripts/gen-cordis-catalog.ts (verified fresh by pnpm run verify-cordis-catalog in doc-sync; regenerate with pnpm run gen-cordis-catalog) — this section is byte-identical in both language sides of the page. Signature blocks use a ts cordis-catalog fence and keep the original source JSDoc; dispatch modes are defined in the primer, and the framework-inherited ctx API lives in cordis-api/inherited.md.
ctx.codeRuntime — CodeRuntime (abstract seam)
Registers one ctx.codeRuntime implementation. Program, budget, abort, and substrate failures resolve in CodeRunResult; only Service Definition contract misuse rejects. Implementations bridge structured-cloneable bindings, materialize each declared namespace rejection class, treat programs as hostile peers, isolate runs from one another, and terminate and await in-flight runs during disposal.
/**
* Execute one program against the request's bindings and capture what it
* emitted. See the class doc for the resolution contract (error is a result
* field; rejection means Service Definition contract misuse only).
* @param request - the program, its bindings, and the abort signal; the
* request carries everything the runtime acts on, with no hidden defaults.
* @returns the run's outcome: completion value (when transferable), the
* ordered log capture, and the failure (if any).
*/
abstract run(request: CodeRunRequest): Promise<CodeRunResult>