fix: preserve runtime option defaults (#38118)

packages/core/src/models-dev.ts

@@ -552,7 +552,7 @@ export const layer = (options?: Options) => Layer.effect(
       ),
     )
 
-    const source = options?.url ?? "https://models.dev"
+    const source = options?.url || "https://models.dev"
     const fetch = options?.fetch ?? true
     const userAgent = `opencode/${InstallationChannel}/${InstallationVersion}/${options?.client ?? "cli"}`
     const filepath = path.join(

packages/core/test/models.test.ts

@@ -236,6 +236,16 @@ describe("ModelsDev Service", () => {
     }),
   )
 
+  it.live("uses the default models URL when the configured URL is empty", () =>
+    Effect.gen(function* () {
+      const state = yield* Ref.make(initialState)
+      yield* ModelsDev.Service.use((service) => service.get()).pipe(
+        Effect.provide(buildLayer(state, { url: "", fetch: true })),
+      )
+      expect((yield* Ref.get(state)).calls[0]?.url).toBe("https://models.dev/api.json")
+    }),
+  )
+
   it.live("get() is single-flight under concurrent calls", () =>
     Effect.gen(function* () {
       yield* writeCache(fixture)