MCP Planned

Progress and cancellation

Report progress and cancel active MCP executions.

> **Optional transport features are not advertised.** MCP execution currently
> returns a completed result or a pending job ID. The server selects JSON rather
> than SSE, so request-scoped progress and disconnect cancellation do not apply.

## Intended outcome

Clients should use bounded polling and stop polling when they no longer need the
result. Stopping polling does not cancel the worker job. Adding SSE later would
require cancellation to stop work safely without changing REST/MCP credit or
idempotency semantics.

Cancellation must define whether work is merely no longer awaited or is actually stopped in the worker plane. Documentation must not use those meanings interchangeably.

Optional transport features are not advertised. MCP execution currently returns a completed result or a pending job ID. The server selects JSON rather than SSE, so request-scoped progress and disconnect cancellation do not apply.

Intended outcome

Clients should use bounded polling and stop polling when they no longer need the result. Stopping polling does not cancel the worker job. Adding SSE later would require cancellation to stop work safely without changing REST/MCP credit or idempotency semantics.

Cancellation must define whether work is merely no longer awaited or is actually stopped in the worker plane. Documentation must not use those meanings interchangeably.