diff --git a/.changeset/required-judge-tool-choice.md b/.changeset/required-judge-tool-choice.md
new file mode 100644
index 000000000..f16afc13b
--- /dev/null
+++ b/.changeset/required-judge-tool-choice.md
@@ -0,0 +1,5 @@
+---
+'@livekit/agents': patch
+---
+
+Use required tool choice for message judge LLM calls.
diff --git a/agents/src/voice/testing/run_result.test.ts b/agents/src/voice/testing/run_result.test.ts
index 60e1f27f2..0d31e178c 100644
--- a/agents/src/voice/testing/run_result.test.ts
+++ b/agents/src/voice/testing/run_result.test.ts
@@ -4,8 +4,15 @@
 import { ReadableStream } from 'node:stream/web';
 import { describe, expect, it } from 'vitest';
 import { z } from 'zod';
-import { FunctionCall } from '../../llm/chat_context.js';
-import { ToolContext, tool } from '../../llm/tool_context.js';
+import { type ChatContext, ChatMessage, FunctionCall } from '../../llm/chat_context.js';
+import { type ChatChunk, LLM, LLMStream } from '../../llm/llm.js';
+import {
+  type ToolChoice,
+  ToolContext,
+  type ToolContextLike,
+  tool,
+} from '../../llm/tool_context.js';
+import { type APIConnectOptions, DEFAULT_API_CONNECT_OPTIONS } from '../../types.js';
 import { Agent } from '../agent.js';
 import { performToolExecutions } from '../generation.js';
 import { SpeechHandle } from '../speech_handle.js';
@@ -23,6 +30,66 @@ class AgentB extends Agent {
   }
 }
 
+class CapturingLLM extends LLM {
+  toolChoice?: ToolChoice;
+
+  constructor(private readonly toolCall: FunctionCall) {
+    super();
+  }
+
+  label(): string {
+    return 'capturing';
+  }
+
+  chat({
+    chatCtx,
+    toolCtx,
+    connOptions = DEFAULT_API_CONNECT_OPTIONS,
+    toolChoice,
+  }: Parameters<LLM['chat']>[0]): LLMStream {
+    this.toolChoice = toolChoice;
+    return new CapturingStream(this, {
+      chatCtx,
+      toolCtx,
+      connOptions,
+      toolCall: this.toolCall,
+    });
+  }
+}
+
+class CapturingStream extends LLMStream {
+  constructor(
+    llm: LLM,
+    {
+      chatCtx,
+      toolCtx,
+      connOptions,
+      toolCall,
+    }: {
+      chatCtx: ChatContext;
+      toolCtx?: ToolContextLike;
+      connOptions: APIConnectOptions;
+      toolCall: FunctionCall;
+    },
+  ) {
+    super(llm, { chatCtx, toolCtx, connOptions });
+    this.toolCall = toolCall;
+  }
+
+  private readonly toolCall: FunctionCall;
+
+  protected async run(): Promise<void> {
+    const chunk: ChatChunk = {
+      id: 'test',
+      delta: {
+        role: 'assistant',
+        toolCalls: [this.toolCall],
+      },
+    };
+    this.queue.put(chunk);
+  }
+}
+
 describe('withMockTools', () => {
   it('sets the mock registry for the given agent inside the block', () => {
     const mock = () => 'mocked';
@@ -205,3 +272,26 @@ describe('RunResult speech handle error propagation', () => {
     await expect(run.wait()).resolves.toBe(run);
   });
 });
+
+describe('MessageAssert judge', () => {
+  it('uses required tool choice', async () => {
+    const llmInstance = new CapturingLLM(
+      FunctionCall.create({
+        callId: 'call_1',
+        name: 'check_intent',
+        args: JSON.stringify({ success: true, reason: 'ok' }),
+      }),
+    );
+    const result = new RunResult();
+    result.events.push({
+      type: 'message',
+      item: ChatMessage.create({ role: 'assistant', content: 'Hello there' }),
+    });
+
+    await result.expect.at(0).isMessage({ role: 'assistant' }).judge(llmInstance, {
+      intent: 'greets the user',
+    });
+
+    expect(llmInstance.toolChoice).toBe('required');
+  });
+});
diff --git a/agents/src/voice/testing/run_result.ts b/agents/src/voice/testing/run_result.ts
index e43e63502..a23e28757 100644
--- a/agents/src/voice/testing/run_result.ts
+++ b/agents/src/voice/testing/run_result.ts
@@ -938,7 +938,7 @@ export class MessageAssert extends EventAssert {
     const stream = llm.chat({
       chatCtx,
       toolCtx: [checkIntentTool],
-      toolChoice: { type: 'function', function: { name: 'check_intent' } },
+      toolChoice: 'required',
       extraKwargs: { temperature: 0 },
     });