The workflow seam lets an agent run a model-written orchestration SCRIPT that starts subagents. Like [subagent](subagent.md) it is **one optional capability**, not part of the agent loop, so its types and operations live here rather than in [core.md](core.md). Like bash, it permits ONE engine implementation per context to provide `ctx.workflows`; there is no named-provider registry (a second engine replaces the first through plugin configuration rather than running beside it).
Service Definition: [dsh-workflow](../../packages/workflow/workflow) (`ctx.workflows` + the vocabulary below). The Service provider is [dsh-workflow-workerthread](../../packages/workflow/workflow-workerthread) (a `node:worker_threads` engine — one worker per run, the script's vm context inside it); the model-facing Consumer is [dsh-tool-workflow](../../packages/workflow/tool-workflow). The proposal and rationale: [the dynamic-workflows Agent Note](../../.agents/notes/implemented/feature/2026-07-05-dynamic-workflows.md).
What a caller asks for when starting a run. The ordinary workflow tool builds this from the model's `{ script, meta, args }` call plus the calling agent; specialized consumers may also select one engine-wide `subagentProvider` and lower `maxTotalAgents` for the run, but the script cannot observe or replace either policy. `meta` and `args` are plain JSON DATA (the engine validates `meta` against its schema and rejects loud BEFORE anything runs — no script text is ever evaluated to obtain it). `parent` is REQUIRED — every child the script starts is attributed to it, and cwd, lineage, and depth pass through the [subagent seam](subagent.md).
The identity block carried as data on the start request (the tool's `meta` parameter; the field vocabulary matches the Claude Code dynamic-workflows meta block). `phases` is progress vocabulary only: `phase()` calls match titles for observers; no execution structure is implied.
The outcome of one run, resolved by `WorkflowRun.result`. `value` is the script's materialized return value — plain host-realm JSON data (`null` when the script returned nothing) — meaningful only for `completed`. `stopReason` is a CLOSED union (engine-owned; consumers may exhaust it): `completed` | `cancelled` | `error`. A non-`completed` reason carries the failure in `error`, and the consumer maps it to an `isError` tool result rather than reporting partial output as success.
The handle the consumer holds while a script executes. The consumer awaits `result`, may `cancel` mid-flight, and MUST `dispose` on every path. `result` does NOT reject — a script failure resolves with `stopReason: 'error'` — and once the run is cancelled it SETTLES within the engine's bounded grace even if the script itself never settles (the engine force-settles `cancelled`; the worker-thread engine then terminates the script's worker), so a consumer awaiting `result` is never wedged past a cancellation. `dispose()` = cancel + that bounded settle + child quiescence; it never hangs on a stuck script.
Hook misuse inside a script — bad arguments, unknown/deferred `agent()` options, a schema outside the [structured-output subset](../../packages/core/tools/README.md), a tripped cap, a seam start failure, cancellation — throws a `WorkflowError` with `fatal: true`. The `parallel()`/`pipeline()` combinators RE-THROW fatal errors instead of mapping the item to `null`: a typo'd option must kill the script loudly, never dissolve into something that reads as an ordinary child failure. The per-item `null` is reserved for child-run failures (a non-`completed` stop reason) and ordinary in-stage script errors.
The `workflow/*` events (`workflow/start`, `workflow/phase`, `workflow/log`, `workflow/agent-start`, `workflow/agent-end`, `workflow/end` — see the [events catalog](#cordis-surface)) are **observe-only** emits carrying DATA SNAPSHOTS: every payload starts with `WorkflowRunInfo` (id + meta), never the live `WorkflowRun`, so a subscriber cannot gain `cancel`/`dispose`, and `workflow/end` deliberately omits the result value (a listener observing outcomes must not receive a mutable alias of the caller's result). Every emit is per-listener contained — a throwing subscriber is logged, never propagated, and cannot starve the listeners registered after it — and every listener receives its own payload clone, so mutating it corrupts neither the engine nor other listeners; the containment mirrors `subagent/start`/`subagent/end`.
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## Cordis surface
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](../cordis-primer.md#dispatch-modes), and the framework-inherited `ctx` surface lives in [cordis-api/inherited.md](../cordis-api/inherited.md).
Workflow Service Definition contract. Invalid requests throw before publication; a live run is holder-owned, its result never rejects, cancellation and disposal are bounded, and disposal waits for child cleanup within that bound. Lifecycle listener failures are contained, and `workflow/end` fires exactly once as the result settles.
One `agent()` call settled (clean result, child failure, or run cancellation). Paired with Events['workflow/agent-start'] by `agent.seq`, exactly once per started call on every stop path — on an engine termination path (a worker killed past its grace) the end is engine-synthesized with outcome `'cancelled'`.
```ts cordis-catalog
/**
* One `agent()` call settled (clean result, child failure, or run
* cancellation). Paired with {@link Events['workflow/agent-start']} by
* `agent.seq`, exactly once per started call on every stop path — on an
* engine termination path (a worker killed past its grace) the end is
* engine-synthesized with outcome `'cancelled'`.
* @param info - the run's identity snapshot.
* @param agent - the call identity plus its outcome.
One `agent()` call established a published child run. Paired with Events['workflow/agent-end'] by `agent.seq`. A call that never receives a published run from the provider emits neither event in this pair.
```ts cordis-catalog
/**
* One `agent()` call established a published child run. Paired with
* {@link Events['workflow/agent-end']} by `agent.seq`. A call that never
* receives a published run from the provider emits neither
* event in this pair.
* @param info - the run's identity snapshot.
* @param agent - the call's sequence number, label, phase, and child id.
