fix: handle Azure filter stream chunks

src/lib/ChatCompletionStream.ts

@@ -205,27 +205,28 @@ export class ChatCompletionStream<ParsedT = null>
 
     for (const choice of chunk.choices) {
       const choiceSnapshot = completion.choices[choice.index]!;
+      const { delta } = choice;
 
       if (
-        choice.delta.content != null &&
+        delta?.content != null &&
         choiceSnapshot.message?.role === 'assistant' &&
         choiceSnapshot.message?.content
       ) {
-        this._emit('content', choice.delta.content, choiceSnapshot.message.content);
+        this._emit('content', delta.content, choiceSnapshot.message.content);
         this._emit('content.delta', {
-          delta: choice.delta.content,
+          delta: delta.content,
           snapshot: choiceSnapshot.message.content,
           parsed: choiceSnapshot.message.parsed,
         });
       }
 
       if (
-        choice.delta.refusal != null &&
+        delta?.refusal != null &&
         choiceSnapshot.message?.role === 'assistant' &&
         choiceSnapshot.message?.refusal
       ) {
         this._emit('refusal.delta', {
-          delta: choice.delta.refusal,
+          delta: delta.refusal,
           snapshot: choiceSnapshot.message.refusal,
         });
       }
@@ -254,7 +255,7 @@ export class ChatCompletionStream<ParsedT = null>
         }
       }
 
-      for (const toolCall of choice.delta.tool_calls ?? []) {
+      for (const toolCall of delta?.tool_calls ?? []) {
         if (state.current_tool_call_index !== toolCall.index) {
           this.#emitContentDoneEvents(choiceSnapshot);
 
@@ -267,7 +268,7 @@ export class ChatCompletionStream<ParsedT = null>
         state.current_tool_call_index = toolCall.index;
       }
 
-      for (const toolCallDelta of choice.delta.tool_calls ?? []) {
+      for (const toolCallDelta of delta?.tool_calls ?? []) {
         const toolCallSnapshot = choiceSnapshot.message.tool_calls?.[toolCallDelta.index];
         if (!toolCallSnapshot?.type) {
           continue;
@@ -401,13 +402,13 @@ export class ChatCompletionStream<ParsedT = null>
     const stream = Stream.fromReadableStream<ChatCompletionChunk>(readableStream, this.controller);
     let chatId;
     for await (const chunk of stream) {
-      if (chatId && chatId !== chunk.id) {
+      if (chatId && chunk.id && chatId !== chunk.id) {
         // A new request has been made.
         this._addChatCompletion(this.#endRequest());
       }
 
       this.#addChunk(chunk);
-      chatId = chunk.id;
+      if (chunk.id) chatId = chunk.id;
     }
     if (stream.controller.signal?.aborted) {
       throw new APIUserAbortError();
@@ -432,7 +433,7 @@ export class ChatCompletionStream<ParsedT = null>
         ...rest,
         choices: [],
       };
-    } else {
+    } else if (chunk.id) {
       Object.assign(snapshot, rest);
     }
 

tests/lib/ChatCompletionStream.test.ts

@@ -1,7 +1,9 @@
 import OpenAI from 'openai';
 import { zodResponseFormat } from 'openai/helpers/zod';
 import { ChatCompletionStream } from 'openai/lib/ChatCompletionStream';
+import { ChatCompletionStreamingRunner } from 'openai/lib/ChatCompletionStreamingRunner';
 import { ChatCompletionTokenLogprob } from 'openai/resources';
+import { Stream } from 'openai/streaming';
 import { z } from 'zod/v4';
 import { makeStreamSnapshotRequest } from '../utils/mock-snapshots';
 
@@ -58,6 +60,64 @@ describe('.stream()', () => {
     expect(removeEventListenerSpy).toHaveBeenCalledWith('abort', abortListener);
   });
 
+  it('handles Azure async filter chunks without deltas', async () => {
+    const chunks: OpenAI.Chat.ChatCompletionChunk[] = [
+      {
+        id: 'chatcmpl-test',
+        object: 'chat.completion.chunk',
+        created: 1,
+        model: 'gpt-test',
+        choices: [
+          {
+            index: 0,
+            delta: { role: 'assistant', content: 'hello' },
+            finish_reason: null,
+            logprobs: null,
+          },
+        ],
+      },
+      {
+        id: 'chatcmpl-test',
+        object: 'chat.completion.chunk',
+        created: 1,
+        model: 'gpt-test',
+        choices: [
+          {
+            index: 0,
+            delta: {},
+            finish_reason: 'stop',
+            logprobs: null,
+          },
+        ],
+      },
+      {
+        id: '',
+        object: '',
+        created: 0,
+        model: '',
+        choices: [
+          {
+            index: 0,
+            finish_reason: null,
+            content_filter_results: {},
+          },
+        ],
+      } as unknown as OpenAI.Chat.ChatCompletionChunk,
+    ];
+    const readable = new Stream(async function* () {
+      for (const chunk of chunks) yield chunk;
+    }, new AbortController()).toReadableStream();
+
+    const stream = ChatCompletionStreamingRunner.fromReadableStream(readable);
+
+    await expect(stream.finalChatCompletion()).resolves.toMatchObject({
+      id: 'chatcmpl-test',
+      created: 1,
+      model: 'gpt-test',
+      choices: [{ message: { content: 'hello' } }],
+    });
+  });
+
   it('works', async () => {
     const stream = await makeStreamSnapshotRequest((openai) =>
       openai.chat.completions.stream({