Gemini API error: empty text content causes 'required oneof field data must have one initialized field'

[Darley-Wey]

Description

When a Claude API request contains an assistant message with empty text content, the Antigravity/Gemini translator produces an invalid request that causes the Gemini API to return a 400 error.

Error Message

{
  "error": {
    "code": 400,
    "message": "* GenerateContentRequest.contents[1].parts[0].data: required oneof field 'data' must have one initialized field",
    "status": "INVALID_ARGUMENT"
  }
}

Reproduction

Send a Claude API request with an assistant message containing empty text:

{
  "messages": [
    {"role": "user", "content": [{"type": "text", "text": "你好"}]},
    {"role": "assistant", "content": [{"type": "text", "text": ""}]},
    {"role": "user", "content": [{"type": "text", "text": "..."}]}
  ]
}

Root Cause

In internal/translator/antigravity/claude/antigravity_claude_request.go, when processing text content, if the text is empty, a part object {} is still created and added to the parts array. The Gemini API requires every part to have at least one data field initialized.

Expected Behavior

Empty text parts should be skipped during translation to avoid sending invalid requests to the Gemini API.

Environment

• Route: /api/provider/anthropic/v1/messages
• Backend: Antigravity (Gemini)
• Version: v6.7.26-0-plus