feat(realtime): add changePeerConnection option (#66)

* feat(realtime): add changePeerConnection option

* feat(realtime): finalize changePeerConnection hook

* Update change-peer-connection.md

Author: dkundel-openai

.changeset/change-peer-connection.md

@@ -0,0 +1,6 @@
+---
+'@openai/agents-realtime': patch
+---
+
+Add `changePeerConnection` option to `OpenAIRealtimeWebRTC` allowing interception
+and replacement of the created `RTCPeerConnection` before the offer is made.

packages/agents-realtime/src/openaiRealtimeWebRtc.ts

@@ -61,6 +61,14 @@ export type OpenAIRealtimeWebRTCOptions = {
    * @see https://platform.openai.com/docs/guides/realtime#creating-an-ephemeral-token
    */
   useInsecureApiKey?: boolean;
+  /**
+   * Optional hook invoked with the freshly created peer connection. Returning a
+   * different connection will override the one created by the transport layer.
+   * This is called right before the offer is created and can be asynchronous.
+   */
+  changePeerConnection?: (
+    peerConnection: RTCPeerConnection,
+  ) => RTCPeerConnection | Promise<RTCPeerConnection>;
 } & OpenAIRealtimeBaseOptions;
 
 /**
@@ -158,7 +166,7 @@ export class OpenAIRealtimeWebRTC
 
         const connectionUrl = new URL(baseUrl);
 
-        const peerConnection = new RTCPeerConnection();
+        let peerConnection: RTCPeerConnection = new RTCPeerConnection();
         const dataChannel = peerConnection.createDataChannel('oai-events');
 
         this.#state = {
@@ -226,6 +234,12 @@ export class OpenAIRealtimeWebRTC
           }));
         peerConnection.addTrack(stream.getAudioTracks()[0]);
 
+        if (this.options.changePeerConnection) {
+          peerConnection =
+            await this.options.changePeerConnection(peerConnection);
+          this.#state = { ...this.#state, peerConnection };
+        }
+
         const offer = await peerConnection.createOffer();
         await peerConnection.setLocalDescription(offer);
 

packages/agents-realtime/test/openaiRealtimeWebRtc.test.ts

@@ -195,4 +195,14 @@ describe('OpenAIRealtimeWebRTC.interrupt', () => {
     const rtc = new OpenAIRealtimeWebRTC();
     expect(() => rtc.sendEvent({ type: 'test' } as any)).toThrow();
   });
+
+  it('allows overriding the peer connection', async () => {
+    class NewPeerConnection extends FakeRTCPeerConnection {}
+    const custom = new NewPeerConnection();
+    const rtc = new OpenAIRealtimeWebRTC({
+      changePeerConnection: async () => custom as any,
+    });
+    await rtc.connect({ apiKey: 'ek_test' });
+    expect(rtc.connectionState.peerConnection).toBe(custom as any);
+  });
 });