diff --git a/.changeset/bumpy-cats-run.md b/.changeset/bumpy-cats-run.md
new file mode 100644
index 00000000..47f2894c
--- /dev/null
+++ b/.changeset/bumpy-cats-run.md
@@ -0,0 +1,5 @@
+---
+'@openai/agents-realtime': patch
+---
+
+fix: #552 WebSocket Realtime Agent: invalid_request_error with decimal audio_end_ms data
diff --git a/packages/agents-realtime/src/openaiRealtimeWebsocket.ts b/packages/agents-realtime/src/openaiRealtimeWebsocket.ts
index de1e9dcc..3c4e7935 100644
--- a/packages/agents-realtime/src/openaiRealtimeWebsocket.ts
+++ b/packages/agents-realtime/src/openaiRealtimeWebsocket.ts
@@ -426,7 +426,8 @@ export class OpenAIRealtimeWebSocket
     }
 
     const length = this._audioLengthMs ?? Number.POSITIVE_INFINITY;
-    const audio_end_ms = Math.max(0, Math.min(Math.floor(elapsedTime), length));
+    // audio_end_ms must be an integer
+    const audio_end_ms = Math.max(0, Math.floor(Math.min(elapsedTime, length)));
 
     this.emit('audio_interrupted');
     this.sendEvent({
diff --git a/packages/agents-realtime/test/openaiRealtimeWebsocket.test.ts b/packages/agents-realtime/test/openaiRealtimeWebsocket.test.ts
index 75b2b8bf..db135648 100644
--- a/packages/agents-realtime/test/openaiRealtimeWebsocket.test.ts
+++ b/packages/agents-realtime/test/openaiRealtimeWebsocket.test.ts
@@ -205,6 +205,22 @@ describe('OpenAIRealtimeWebSocket', () => {
     expect(baseSpy).toHaveBeenCalled();
   });
 
+  it('_interrupt floors fractional audio length when clamping', () => {
+    const ws = new OpenAIRealtimeWebSocket();
+    const sendSpy = vi
+      .spyOn(OpenAIRealtimeWebSocket.prototype as any, 'sendEvent')
+      .mockImplementation(() => {});
+    // @ts-expect-error - testing protected field.
+    ws._audioLengthMs = 42.8;
+    ws._interrupt(100, false);
+    const call = sendSpy.mock.calls.find(
+      (c: unknown[]) => (c[0] as any).type === 'conversation.item.truncate',
+    );
+    expect((call?.[0] as any).audio_end_ms).toBe(42);
+    expect(Number.isInteger((call?.[0] as any).audio_end_ms)).toBe(true);
+    sendSpy.mockRestore();
+  });
+
   it('_interrupt quantizes and clamps elapsedTime', () => {
     const ws = new OpenAIRealtimeWebSocket();
     const sendSpy = vi