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?

I created a super simple demo here: https://github.com/finbarr/multi-tool-demo

If the LLM returns multiple tool calls with a single message, RubyLLM tries to execute each sequentially but makes intermediate calls back to the LLM after each one, rather than running them all and then making a callback to the LLM. Somewhere along the way it breaks with

'RubyLLM::ErrorMiddleware.parse_error': messages: text content blocks must be non-empty (RubyLLM::BadRequestError)

How to reproduce

• clone https://github.com/finbarr/multi-tool-demo. It's a basic rails app with the 3 models needed by RubyLLM and the gem added with basic config.
• run ./script/demo.rb
• see the error

Expected behavior

• RubyLLM should call each tool, aggregate the results, then make a callback to the LLM with all of the tool results.
• It shouldn't break.

What actually happened

• RubyLLM calls the tools one at a time and tries to return the results individually to the LLM.
• It breaks.

Environment

• ruby 3.4.3
• rails 8.0.2
• ruby_llm 1.3.0