It lets a test drive ctx.subagents and the model-facing dsh-tool-subagent through the real cordis Loader / export path, exercising provider registration, start-time capability validation, the run lifecycle (result / cancel / dispose), and the structured-output branch — all deterministically and keylessly.

Model Experience

Context surface	What the model sees	Token effect
Deterministic test result	No child model runs. When exercised through `dsh-tool-subagent`, the parent sees the mock provider's configured reply or stop-reason error, and structured tests receive the configured object.	Zero child-model tokens. Only the scripted final result is added to the parent test history.

Usage

Load it as a plugin (functional shape: name/inject/Config/apply, no default). Config (all optional):

Key	Default	Meaning
`name`	`mock`	Registry name to register the provider under.
`reply`	`mock subagent reply`	The scripted child's final answer text.
`stopReason`	`completed`	The stop reason `result` settles with.
`capabilities`	all `true`	Which start-time capabilities (`outputSchema`/`depthLimit`/`toolFilter`) the provider advertises.
`inheritsParentContext`	`false`	The context contract to declare; `true` exercises the fork-shaped tool wording in consumer tests.
`structured`	`{ reply }`	Structured value surfaced when a request carries an `outputSchema` and the capability is on.

A cancel() issued before result settles flips the stop reason to aborted, so the cancellation path is observable.