Enable required tool choice for structured output tests

packages/opencode/test/provider/provider.test.ts

@@ -2048,16 +2048,32 @@ test("models.dev normalization fills required response fields", () => {
           output: 128_000,
         },
       },
+      "deepseek-reasoner": {
+        id: "deepseek-reasoner",
+        name: "DeepSeek Reasoner",
+        family: "deepseek",
+        tool_choice_required: false,
+        cost: {
+          input: 0.5,
+          output: 2,
+        },
+        limit: {
+          context: 64_000,
+          output: 8_000,
+        },
+      },
     },
   } as unknown as ModelsDev.Provider
 
   const model = Provider.fromModelsDevProvider(provider).models["gpt-5.4"]
+  const reasoner = Provider.fromModelsDevProvider(provider).models["deepseek-reasoner"]
   expect(model.api.url).toBe("")
   expect(model.capabilities.temperature).toBe(false)
   expect(model.capabilities.reasoning).toBe(false)
   expect(model.capabilities.attachment).toBe(false)
   expect(model.capabilities.toolcall).toBe(true)
   expect(model.capabilities.toolChoiceRequired).toBe(true)
+  expect(reasoner.capabilities.toolChoiceRequired).toBe(false)
   expect(model.release_date).toBe("")
 })
 

packages/opencode/test/session/prompt.test.ts

@@ -548,6 +548,38 @@ it.instance("structured output uses auto tool choice and errors when the model i
   }),
 )
 
+it.instance("structured output uses required tool choice by default", () =>
+  Effect.gen(function* () {
+    const { llm } = yield* useServerConfig(providerCfg)
+    const prompt = yield* SessionPrompt.Service
+    const sessions = yield* Session.Service
+    const chat = yield* sessions.create({
+      title: "Pinned",
+      permission: [{ permission: "*", pattern: "*", action: "allow" }],
+    })
+    yield* llm.text("plain text")
+
+    yield* prompt.prompt({
+      sessionID: chat.id,
+      agent: "build",
+      model: { providerID: ProviderID.make("test"), modelID: ModelID.make("test-model") },
+      parts: [{ type: "text", text: "say hello" }],
+      format: {
+        type: "json_schema",
+        schema: {
+          type: "object",
+          properties: { answer: { type: "string" } },
+          required: ["answer"],
+        },
+      },
+    })
+
+    const inputs = yield* llm.inputs
+    expect(inputs).toHaveLength(1)
+    expect(inputs[0].tool_choice).toBe("required")
+  }),
+)
+
 noLLMServer.instance(
   "prompt emits v2 prompted and synthetic events",
   () =>