Add async iterable support to ChatClient.completeStreamingChat()

[Copilot]

completeStreamingChat() only accepted a callback, causing confusing runtime errors when developers used the OpenAI SDK's familiar for await pattern. This adds async iterable support while keeping the callback overloads for backward compatibility.

API changes

Two new overloads return AsyncIterable<any> when no callback is passed:

// New: async iterable (consistent with OpenAI SDK)
for await (const chunk of chatClient.completeStreamingChat(messages)) {
  process.stdout.write(chunk.choices?.[0]?.delta?.content ?? '');
}

// New: with tools
for await (const chunk of chatClient.completeStreamingChat(messages, tools)) { ... }

// Existing: callback pattern — unchanged
await chatClient.completeStreamingChat(messages, (chunk) => { ... });
await chatClient.completeStreamingChat(messages, tools, (chunk) => { ... });

Implementation

• _streamChat() — private async generator that bridges executeCommandStreaming's native callback to an async iterable via a chunk queue + wakeConsumer notify pattern. await streamPromise in the finally block ensures native resources are cleaned up even on early iterator exit.
• _completeStreamingChatWithCallback() — extracted from the original implementation; behavior unchanged.
• Public completeStreamingChat() dispatches to the appropriate implementation based on whether a callback argument is present.

Other

• Tests: added async iterable integration test; updated validation tests to cover both patterns.
• Docs (ChatClient.md) and sample app updated to reflect all four overloads.

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Original prompt

---

This section details on the original issue you should resolve

<issue_title>JavaScript ChatClient Streaming Uses Callbacks, Not Async Iterators</issue_title>
<issue_description>

JavaScript ChatClient Streaming Uses Callbacks, Not Async Iterators

Severity: Documentation gap
Component: foundry-local-sdk JavaScript v0.9.x — ChatClient.completeStreamingChat()

The ChatClient returned by model.createChatClient() provides a completeStreamingChat() method, but it uses a callback pattern rather than returning an async iterable:

// ❌ This does NOT work — throws "stream is not async iterable"
for await (const chunk of chatClient.completeStreamingChat(messages)) { ... }

// ✅ Correct pattern — pass a callback
await chatClient.completeStreamingChat(messages, (chunk) => {
  process.stdout.write(chunk.choices?.[0]?.delta?.content ?? "");
});

Impact: Developers familiar with the OpenAI SDK's async iteration pattern (for await) will encounter confusing errors. The callback must be a valid function or the SDK throws "Callback must be a valid function."

Expected: Document the callback pattern in the SDK reference. Alternatively, support the async iterable pattern for consistency with the OpenAI SDK.

---</issue_description>

<agent_instructions>Can you update the JS SDK to support openai sdk's async iteration pattern in the js sdk instead of the current way of using callbacks?</agent_instructions>

Comments on the Issue (you are @copilot in this section)

• Fixes JavaScript ChatClient Streaming Uses Callbacks, Not Async Iterators #507

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Project	Deployment	Actions	Updated (UTC)
foundry-local	Ready	Preview, Comment	Mar 12, 2026 4:46pm