In Anthropic 3 API, Response body is not showing in stacktrace if ChatModel.stream() fails

[jombidev]

Bug description

on call of AnthropicChatModel.stream (method signature: org.springframework.ai.anthropic.AnthropicChatModel#stream(Lorg/springframework/ai/chat/prompt/Prompt;)Lreactor/core/publisher/Flux;), thrown exception's response body is not displaying correctly.

At the AnthropicApi#110, ClientResponse#bodyToMono is never used as Publisher. I don't think it's intentional. It should display the body of error request, instead of Mono<T>#toString().

Environment

Amazon Corretto 17 (OpenJDK 17)
Spring Boot - 3.3.0
Spring AI - 1.0.0-M3

Minimal Complete Reproducible example

Here is simple java code to reproduce:

AnthropicApi api = new AnthropicApi("LEAVING_IT_EMPTY");
StreamingChatModel model = new AnthropicChatModel(api, new AnthropicChatOptions());

model.stream(new Prompt("Hello, world!"))
        .doOnEach((res) -> System.out.println(res.get()))
        .blockLast();

Expected behavior

It can be displayed by passing WebClient builder in constructor of AnthropicApi, but it should display at default.
Await the mono variable. we can get body as String properly.

changing Mono.just~~ to below code:

resp
.bodyToMono(java.lang.String.class)
.map((body) -> new RuntimeException("Response exception, Status: [" + resp.statusCode() +
                  "], Body:[" + body + "]"))

Will work as expected.