Chat Completions Web - AgentScope Java

agentscope-extensions-chat-completions-web exposes an AgentScope Agent behind an OpenAI Chat Completions-compatible API, so OpenAI SDKs, LangChain, LlamaIndex, ChatBox, etc. can connect as if they were talking to OpenAI.

When to use

You want to expose your Agent as a “standard LLM” without modifying clients.
You need streaming with tool-call events that match the OpenAI SSE format.

Add the dependency

<dependency>
    <groupId>io.agentscope</groupId>
    <artifactId>agentscope-extensions-chat-completions-web</artifactId>
    <version>${agentscope.version}</version>
</dependency>

Note: this module ships only the framework-agnostic core adapter — wire HTTP/SSE through the matching Spring Boot Starter (recommended) or your own controller.

Core adapter

import io.agentscope.core.chat.completions.streaming.ChatCompletionsStreamingAdapter;
import io.agentscope.core.chat.completions.model.ChatCompletionsRequest;
import io.agentscope.core.chat.completions.model.ChatCompletionsChunk;
import reactor.core.publisher.Flux;

ChatCompletionsStreamingAdapter adapter = new ChatCompletionsStreamingAdapter();

// Convert OpenAI-style request → Agent invocation, and Agent events → OpenAI chunks
Flux<ChatCompletionsChunk> stream = adapter.stream(agent, request);

The adapter converts AgentScope’s Event stream (including REASONING and TOOL_RESULT) into OpenAI-compatible ChatCompletionsChunk objects:

Text deltas → delta.content
Tool calls → delta.tool_calls[]
Stream end → a chunk with finish_reason

Expose as SSE in Spring Boot

Easiest is the starter — it registers the controller. To do it manually:

@RestController
public class ChatController {
    private final ChatCompletionsStreamingAdapter adapter = new ChatCompletionsStreamingAdapter();
    @Autowired private Agent agent;

    @PostMapping(value = "/v1/chat/completions",
                 produces = MediaType.TEXT_EVENT_STREAM_VALUE)
    public Flux<String> chat(@RequestBody ChatCompletionsRequest req) {
        return adapter.stream(agent, req)
            .map(this::toSseLine);  // serialize and wrap "data: ..."
    }
}

Model routing

OpenAI clients send a model field; route at the controller layer:

String model = req.getModel();   // e.g. "gpt-4o"; route to different Agents
Agent target = agentRegistry.lookup(model);
return adapter.stream(target, req);

Pairs well with

AG-UI for fine-grained UI rendering with event semantics.
Chat Completions Web for plain LLM-style integrations focused on OpenAI compatibility.