# @deepseek-ai/dsh-tasks

English | [中文](README.zh.md)

The background task registry contract (`ctx.tasks`). The abstract `TaskService` and its vocabulary types give long-running producers shared ids, owner isolation, reads, cancellation, waiting, notices, and cleanup under one contract; the process-local registry lives in [`dsh-tasks-local`](../tasks-local/README.md). Producer plugins extend `TaskKindMap` with their opaque id namespace.

## Service contract

- `start(spec): TaskId` validates the control surface, spec, exact live owner, and optional positive `outputLimitBytes` before calling the producer's `run()` once. A starter throw leaves nothing registered; successful return commits without another failable step.
- `get(id, caller?)` and `list(caller?)` return non-consuming snapshots. Listing includes only caller-owned and unowned tasks.
- `read(id, caller?)` consumes the single cursor for stream tasks and reads terminal output idempotently for final-output tasks.
- `kill(id, caller?, reason?)` invokes producer cancellation before changing status. A cancellation throw leaves the task running; success changes it to `stopping` and marks terminal delivery reported.
- `wait(id, timeoutMs, caller?, signal?)` returns a terminal snapshot or the live snapshot at timeout. Aborting stops only the wait; settlement wins once it has committed terminal delivery to that waiter.
- `onTaskDone(listener)` observes each terminal record with the exact owner. Listener throws and rejections are contained; listener work is not awaited.
- `attachSurface(name)` declares a control surface for its effect lifetime. `start()` fails before producer execution when no attached surface serves the spec's owner.

Both registrations are owner-relative, because one registry serves every composition in the process. A surface or listener registered from an unscoped context serves every owner; one registered under an agent composition's scope serves exactly the agents composed under it. So a composition that loads no control surface cannot start background work on the strength of another composition's controls, and one settlement notifies only the listeners its owner's composition registered.

Owned access compares the task's `SessionId` with the caller's. Ids such as `bash-1` are predictable, so this fence is the boundary. Unowned tasks are open to callers and last until service disposal.

`outputLimitBytes` is producer-owned model-presentation policy carried unchanged into snapshots. A control surface applies it after adding status or notice metadata; the registry does not rewrite producer output or invent a default for producers that omit it.

Implementations also owe the lifecycle semantics of the contract: registrations outlive producer and control-surface fibers, owner and service disposal cancel live work and await compliant producers, and settlement is first-wins — one terminal record, one round of contained listener notification, released waiters.

See the [task type catalog](../../../docs/subsystems/tasks.md), the [runtime Agent Note](../../../.agents/notes/implemented/architecture/2026-06-20-generic-long-running-tool-runtime.md), and the [seam Agent Note](../../../.agents/notes/implemented/architecture/2026-07-26-task-registry-seam.md).

## Model Experience

Indirectly, through producer plugins and [`dsh-tool-tasks`](../tool-tasks/README.md), which render task ids, output, status, cancellation, and completion notices.

#### KV Cache effect

No direct invalidation; the named consumer owns any request-prefix changes.

## Known Limitations and Deferred Work

- **Stream output has one consuming cursor** — independent observers need a cursor or snapshot API.
- **Foreground work cannot be promoted** — producers choose foreground or background before starting.
- **The contract is in-process** — `TaskStart.run()` passes callbacks and exact `Agent` objects; a durable or cross-process backend must reshape identity, restart, ownership, and observation semantics before it can implement this seam.
