Fix extraBody serialization by adding @JsonProperty annotation

[CorgiBoyG]

Description

Fixes the issue where extraBody parameters are lost during ModelOptionsUtils.merge() operation due to missing @JsonProperty annotation.

Changes

• Added @JsonProperty("extra_body") annotation to extraBody parameter in ChatCompletionRequest constructor
• Added test case testMergeWithExtraBody() to verify extraBody is correctly merged from OpenAiChatOptions to ChatCompletionRequest

Related Issue

Fixes #4966

Checklist

• Code follows project style
• Commit messages include DCO sign-off
• Added unit tests
• All tests pass locally

[quaff]

It's not a correct fix, see #4936

[CorgiBoyG]

It's not a correct fix, see #4936

@quaff Thanks for the feedback! I appreciate you pointing to PR #4936.

However, I respectfully disagree that this PR is "not a correct fix." Let me explain why both approaches have their merits:

Why PR #4975 (this PR) is a valid fix

1. Root Cause Analysis

The issue occurs because ModelOptionsUtils.merge() filters fields based on @JsonProperty annotations:

private static List<String> getJsonPropertyValues(Class<?> clazz) { return Arrays.stream(clazz.getDeclaredFields()) .map(field -> field.getAnnotation(JsonProperty.class)) // Only @JsonProperty fields .filter(Objects::nonNull) .map(JsonProperty::value) .toList(); }

Problem: ChatCompletionRequest.extraBody parameter lacked @JsonProperty("extra_body"), causing it to be filtered out during merge.
Solution: Add @JsonProperty("extra_body") → merge preserves the field ✅

2. Serialization is NOT affected

@JsonAnyGetter takes precedence over @JsonProperty, so the JSON output remains flat:

@JsonAnyGetter public Map<String, Object> extraBody() { return this.extraBody; }

This ensures backward compatibility - the HTTP request body is still flattened as expected.

Why PR #4936 is also valuable (but different scope)

PR #4936's @MergeableField annotation is an architectural improvement that:

• ✅ Provides explicit control over merge behavior
• ✅ Decouples merge logic from serialization annotations
• ✅ Could benefit future development

However, it:

• ⚠️ Changes core merge infrastructure
• ⚠️ Requires more extensive testing
• ⚠️ Better suited for a feature release (1.2.0) rather than a patch

Proposed Path Forward

I suggest we:

1. Merge PR Fix extraBody serialization by adding @JsonProperty annotation #4975 into 1.1.1 as an urgent hotfix (users currently cannot use Qwen3's thinking chain feature)
2. Continue discussing PR Fix extraBody loss during ModelOptionsUtils.merge() #4936 as a separate architectural improvement for 1.2.0+
3. Both PRs can coexist - Fix extraBody loss during ModelOptionsUtils.merge() #4936 can build upon Fix extraBody serialization by adding @JsonProperty annotation #4975's fix

This way:

• ✅ Users get immediate relief
• ✅ We have more time to properly evaluate the architectural changes in Fix extraBody loss during ModelOptionsUtils.merge() #4936
• ✅ Both contributors' work is valued

@quaff @deejay1 What are your thoughts on this approach? Thanks!