LLMClient.prepare(request) returned a PreparedRequest with target: unknown.
Callers building debug UIs / request previews / plan rendering had to cast
target to the adapter's native shape at every read.
Adds PreparedRequestOf<Target> in schema and a generic Target = unknown
parameter on LLMClient.prepare so callers can opt in to a typed view:
const prepared = yield* client.prepare<OpenAIChatTarget>(request)
prepared.target.model // typed
prepared.target.messages // typed
The runtime payload is unchanged — the adapter still emits target: unknown
and the consumer asserts the shape they expect from the configured adapter.
The cast lives at the public boundary in adapter.ts; everything else stays
honest about runtime types.
Existing callers without the type argument still get target: unknown and
nothing breaks. Test in openai-chat.test.ts proves the narrowing at the
type level.
Kit Langton
75f467bae3