[Bug]: OpenAILike does not work with Gemini API

[lehoang318]

Bug Description

OpenAILike does not work with Gemini API

Version

0.14.15

Steps to Reproduce

llm = OpenAILike(
    model=LLM_MODEL, # Gemini Model
    api_key=LLM_API_KEY, # Gemini API Key
    api_base=LLM_BASE_URL, # `https://generativelanguage.googleapis.com/v1beta/openai/` as guideline in Gemini API OpenAI compatibility
)

Relevant Logs/Tracbacks

stacktrace.log

[logan-markewich]

Whats the error/issue? Probably best to use the GoogleGenAI class though for gemini?
https://developers.llamaindex.ai/python/framework/integrations/llm/google_genai/

[lehoang318]

Whats the error/issue? Probably best to use the GoogleGenAI class though for gemini? https://developers.llamaindex.ai/python/framework/integrations/llm/google_genai/

1. We do get a situation with Gemini stuffs: issue#20782
2. Personally, I would like to standardize my products with OpenAI Compatible API

[xXMrNidaXx]

OpenAILike + Gemini API has some quirks due to API differences:

Key compatibility issues:

1. Tool calling format differs:

# Gemini expects 'function_declarations' not 'tools'
# May need to transform the request

2. Response structure:

# Gemini returns 'candidates' not 'choices'
# OpenAILike may need response transformation

Workaround - use native Gemini integration:

from llama_index.llms.gemini import Gemini

llm = Gemini(
    model='gemini-pro',
    api_key='...'
)

Or patch OpenAILike for Gemini:

class GeminiCompatibleLLM(OpenAILike):
    def _prepare_request(self, messages):
        # Transform OpenAI format to Gemini format
        ...

The cleanest solution is using the native Gemini LLM class since Gemini's API isn't 100% OpenAI-compatible despite the similar patterns.

[lehoang318]

@xXMrNidaXx Thank you for the explanations & advice.
For the time being, I'll stick with OpenRouter to simplify the work.