[BUG] NoMethodError: undefined method 'empty?' for nil in OpenRouter parse_completion_response

[edomaia-dentero]

Basic checks

• I searched existing issues - this hasn't been reported
• I can reproduce this consistently
• This is a RubyLLM bug, not my application code

What's broken?

RubyLLM::Providers::OpenRouter::Chat#parse_completion_response calls .empty? on data without guarding for nil. When OpenRouter returns a response where data is absent (nil), this raises a NoMethodError and the entire request fails.

How to reproduce

1. Configure RubyLLM with the OpenRouter provider (ruby_llm 1.14.1).
2. Create a chat with tools/schema enabled (tool-calling flow).
3. Call chat.ask(...).
4. Intermittently, OpenRouter returns a response where parsed data is nil.
5. RubyLLM crashes in RubyLLM::Providers::OpenRouter::Chat#parse_completion_response when it calls data.empty?.

Note: this is intermittent in production; we cannot reproduce deterministically on every request.

Expected behavior

RubyLLM should handle missing or nil response data safely in OpenRouter parsing (e.g. nil guard before .empty?) and return a controlled error/result instead of raising NoMethodError.

What actually happened

We get this runtime error from ruby_llm:

NoMethodError: undefined method 'empty?' for nil

# lib/ruby_llm/providers/openrouter/chat.rb:55
return if data.empty?

Backtrace top:

RubyLLM::Providers::OpenRouter::Chat#parse_completion_response (lib/ruby_llm/providers/openrouter/chat.rb:55)
RubyLLM::Provider#sync_response (lib/ruby_llm/provider.rb:262)
RubyLLM::Provider#complete (lib/ruby_llm/provider.rb:62)
RubyLLM::Chat#complete / #handle_tool_calls (lib/ruby_llm/chat.rb)
This happens in production background jobs (Rails app) calling RubyLLM.chat(...).ask(...) through OpenRouter.

Environment

• Ruby version: 3.4.6
• RubyLLM version: 1.14.1
• Provider (OpenAI, Google, etc.): OpenRouter
• OS: Linux (production), macOS locally
• Framework: Rails 8.1

[kplawver]

@edomaia-dentero I ran into this today too - the fix seems pretty simple so I threw a PR. If you want to grab the fix (it's literally a one liner in a single method) and monkey patch it until it's merged, that'll get you past it for now.

[edomaia-dentero]

@kplawver, will do thanks!