[rekram1-node]

Problem

EvaluationModel<Options> was invariant in Options because _Options used (options: Options) => Options and EvaluationRoute.evaluate used a contravariant function property signature. As a result, EvaluationModel<SpecificOptions> was not assignable to EvaluationModel:

• EvaluationRequestInput had to constrain Model extends object with a conditional intersection check (Model extends EvaluationModel<EvaluationModelOptions<Model>> ? unknown : never).
• request() had to cast input.model as unknown as EvaluationModel.
• run() had to duplicate input instanceof EvaluationRequest ? input : request(input) and cast request as EvaluationRequestFor<EvaluationOptions, EvaluationQuestions>.

Change

Make EvaluationModel<Options> covariant in Options (matching LanguageModel and MediaModel) and allow request() to accept EvaluationRequest | EvaluationRequestInput directly so run() delegates normalization to request(input) without casts.

 export interface EvaluationRoute<Options extends EvaluationOptions = EvaluationOptions> {
   readonly id: string
-  readonly evaluate: (
-    request: EvaluationRequestFor<Options>,
-    execute: Execute,
-  ) => Effect.Effect<EvaluationResponse, AIError>
+  evaluate(request: EvaluationRequestFor<Options>, execute: Execute): Effect.Effect<EvaluationResponse, AIError>
 }

 export class EvaluationModel<Options extends EvaluationOptions = EvaluationOptions> {
-  declare protected readonly _Options: (options: Options) => Options
+  declare protected readonly _Options: Options

 run(input)
   Effect.try
-    input instanceof EvaluationRequest ? input : request(input)
+    request(input)
-  Effect.flatMap(req => EvaluationClient.evaluate(req as EvaluationRequestFor<...>))
+  Effect.flatMap(EvaluationClient.evaluate)

Out of scope

• Runtime evaluation client validation or provider route behavior.

[opencode-agent]

Looks sound. Type checking for packages/ai, including the evaluation type tests in test/evaluation.types.ts, passes on both the base and this PR, and test/evaluation.test.ts passes. The per-model option types are still enforced after the covariance change, and passing EvaluationClient.evaluate straight to flatMap is fine. There's nothing to run, since runtime behaviour doesn't change.

Public API: only the experimental evaluation types in @opencode/ai change, and existing callers keep working. EvaluationRoute.evaluate changes from a function property to a method signature. EvaluationModel is now covariant in Options. The Model constraint on EvaluationRequestInput, request and run changes from object (plus a conditional check) to EvaluationModel. request gets a new EvaluationRequest | EvaluationRequestInput overload. Runtime behaviour, the CLI, the server, the SDK and config are untouched.

No concerns.