Fix streaming tool call nil arguments

[afurm]

What this does

Fixes a streaming crash when tool-call deltas omit function.arguments by normalizing nil/empty fragments during accumulation, and adds a regression spec to cover the case.

Type of change

• Bug fix
• New feature
• Breaking change
• Documentation
• Performance improvement

Scope check

• I read the Contributing Guide
• This aligns with RubyLLM's focus on LLM communication
• This isn't application-specific logic that belongs in user code
• This benefits most users, not just my specific use case

Required for new features

• I opened an issue before writing code and received maintainer approval
• Linked issue: #___

PRs for new features or enhancements without a prior approved issue will be closed.

Quality check

• I ran overcommit --install and all hooks pass
• I tested my changes thoroughly
  • For provider changes: Re-recorded VCR cassettes with bundle exec rake vcr:record[provider_name]
  • All tests pass: bundle exec rspec
• I updated documentation if needed
• I didn't modify auto-generated files manually (models.json, aliases.json)

AI-generated code

• I used AI tools to help write this code
• I have reviewed and understand all generated code (required if above is checked)

API changes

• Breaking change
• New public methods/classes
• Changed method signatures
• No API changes

[aka-nez]

Faced exactly the same issue with openrouter provider

[smerickson]

I had been running into issues using Haiku 4.5 at AWS Bedrock while streaming and using tool calls. The way it manifested was the model calling a tool with incorrect parameters. I always had a sneaking suspicion that it wasn't model hallucination because I had never experienced that when I was using the AWS SDK directly instead of RubyLLM. I just applied this patch to my system and my sreaming issues with Haiku seen to have been resolved. this would be great to get merged into core.

[afurm]

Thanks for confirming and for testing this.

[KieranP]

Is this error I've just started seeing on local/Ollama related to this PR? I wasn't seeing this about a month ago, maybe a recent Ollama update changed something? If not related, shall I open a new issue?

>
/Users/kieran/.asdf/installs/ruby/4.0.0/lib/ruby/gems/4.0.0/gems/ruby_llm-1.11.0/lib/ruby_llm/error.rb:52:in 'RubyLLM::ErrorMiddleware.parse_error': invalid message content type: <nil> (RubyLLM::BadRequestError)
        from /Users/kieran/.asdf/installs/ruby/4.0.0/lib/ruby/gems/4.0.0/gems/ruby_llm-1.11.0/lib/ruby_llm/streaming.rb:126:in 'RubyLLM::Streaming#handle_parsed_error'
        from /Users/kieran/.asdf/installs/ruby/4.0.0/lib/ruby/gems/4.0.0/gems/ruby_llm-1.11.0/lib/ruby_llm/streaming.rb:86:in 'RubyLLM::Streaming#handle_failed_response'
        from /Users/kieran/.asdf/installs/ruby/4.0.0/lib/ruby/gems/4.0.0/gems/ruby_llm-1.11.0/lib/ruby_llm/streaming.rb:50:in 'block in RubyLLM::Streaming#build_on_data_handler'
        from /Users/kieran/.asdf/installs/ruby/4.0.0/lib/ruby/gems/4.0.0/gems/ruby_llm-1.11.0/lib/ruby_llm/streaming.rb:169:in 'block in RubyLLM::Streaming::FaradayHandlers.v2_on_data'
        from /Users/kieran/.asdf/installs/ruby/4.0.0/lib/ruby/gems/4.0.0/gems/faraday-2.14.0/lib/faraday/options/env.rb:176:in 'block in Faraday::Env#stream_response'
        from /Users/kieran/.asdf/installs/ruby/4.0.0/lib/ruby/4.0.0/net/protocol.rb:540:in 'Net::ReadAdapter#call_block'
        from /Users/kieran/.asdf/installs/ruby/4.0.0/lib/ruby/4.0.0/net/protocol.rb:531:in 'Net::ReadAdapter#<<'
        from /Users/kieran/.asdf/installs/ruby/4.0.0/lib/ruby/4.0.0/net/protocol.rb:172:in 'Net::BufferedIO#read'
        from /Users/kieran/.asdf/installs/ruby/4.0.0/lib/ruby/gems/4.0.0/gems/net-http-0.9.1/lib/net/http/response.rb:604:in 'block in Net::HTTPResponse#read_body_0'
        from /Users/kieran/.asdf/installs/ruby/4.0.0/lib/ruby/gems/4.0.0/gems/net-http-0.9.1/lib/net/http/response.rb:589:in 'Net::HTTPResponse#inflater'
        from /Users/kieran/.asdf/installs/ruby/4.0.0/lib/ruby/gems/4.0.0/gems/net-http-0.9.1/lib/net/http/response.rb:594:in 'Net::HTTPResponse#read_body_0'
        from /Users/kieran/.asdf/installs/ruby/4.0.0/lib/ruby/gems/4.0.0/gems/net-http-0.9.1/lib/net/http/response.rb:364:in 'Net::HTTPResponse#read_body'
        from /Users/kieran/.asdf/installs/ruby/4.0.0/lib/ruby/gems/4.0.0/gems/faraday-net_http-3.4.2/lib/faraday/adapter/net_http.rb:116:in 'block (2 levels) in Faraday::Adapter::NetHttp#request_with_wrapped_block'
        from /Users/kieran/.asdf/installs/ruby/4.0.0/lib/ruby/gems/4.0.0/gems/net-http-0.9.1/lib/net/http.rb:2461:in 'block in Net::HTTP#transport_request'
        from /Users/kieran/.asdf/installs/ruby/4.0.0/lib/ruby/gems/4.0.0/gems/net-http-0.9.1/lib/net/http/response.rb:321:in 'Net::HTTPResponse#reading_body'
        from /Users/kieran/.asdf/installs/ruby/4.0.0/lib/ruby/gems/4.0.0/gems/net-http-0.9.1/lib/net/http.rb:2458:in 'Net::HTTP#transport_request'
        from /Users/kieran/.asdf/installs/ruby/4.0.0/lib/ruby/gems/4.0.0/gems/net-http-0.9.1/lib/net/http.rb:2410:in 'Net::HTTP#request'
        from /Users/kieran/.asdf/installs/ruby/4.0.0/lib/ruby/gems/4.0.0/gems/faraday-net_http-3.4.2/lib/faraday/adapter/net_http.rb:113:in 'block in Faraday::Adapter::NetHttp#request_with_wrapped_block'
        from /Users/kieran/.asdf/installs/ruby/4.0.0/lib/ruby/gems/4.0.0/gems/net-http-0.9.1/lib/net/http.rb:1630:in 'Net::HTTP#start'
        from /Users/kieran/.asdf/installs/ruby/4.0.0/lib/ruby/gems/4.0.0/gems/faraday-net_http-3.4.2/lib/faraday/adapter/net_http.rb:112:in 'Faraday::Adapter::NetHttp#request_with_wrapped_block'
        from /Users/kieran/.asdf/installs/ruby/4.0.0/lib/ruby/gems/4.0.0/gems/faraday-net_http-3.4.2/lib/faraday/adapter/net_http.rb:98:in 'block in Faraday::Adapter::NetHttp#perform_request'
        from /Users/kieran/.asdf/installs/ruby/4.0.0/lib/ruby/gems/4.0.0/gems/faraday-2.14.0/lib/faraday/options/env.rb:172:in 'Faraday::Env#stream_response'
        from /Users/kieran/.asdf/installs/ruby/4.0.0/lib/ruby/gems/4.0.0/gems/faraday-net_http-3.4.2/lib/faraday/adapter/net_http.rb:97:in 'Faraday::Adapter::NetHttp#perform_request'
        from /Users/kieran/.asdf/installs/ruby/4.0.0/lib/ruby/gems/4.0.0/gems/faraday-net_http-3.4.2/lib/faraday/adapter/net_http.rb:66:in 'block in Faraday::Adapter::NetHttp#call'
        from /Users/kieran/.asdf/installs/ruby/4.0.0/lib/ruby/gems/4.0.0/gems/faraday-2.14.0/lib/faraday/adapter.rb:45:in 'Faraday::Adapter#connection'
        from /Users/kieran/.asdf/installs/ruby/4.0.0/lib/ruby/gems/4.0.0/gems/faraday-net_http-3.4.2/lib/faraday/adapter/net_http.rb:65:in 'Faraday::Adapter::NetHttp#call'
        from /Users/kieran/.asdf/installs/ruby/4.0.0/lib/ruby/gems/4.0.0/gems/ruby_llm-1.11.0/lib/ruby_llm/error.rb:39:in 'RubyLLM::ErrorMiddleware#call'
        from /Users/kieran/.asdf/installs/ruby/4.0.0/lib/ruby/gems/4.0.0/gems/faraday-2.14.0/lib/faraday/middleware.rb:56:in 'Faraday::Middleware#call'
        from /Users/kieran/.asdf/installs/ruby/4.0.0/lib/ruby/gems/4.0.0/gems/faraday-2.14.0/lib/faraday/middleware.rb:56:in 'Faraday::Middleware#call'
        from /Users/kieran/.asdf/installs/ruby/4.0.0/lib/ruby/gems/4.0.0/gems/faraday-multipart-1.2.0/lib/faraday/multipart/middleware.rb:27:in 'Faraday::Multipart::Middleware#call'
        from /Users/kieran/.asdf/installs/ruby/4.0.0/lib/ruby/gems/4.0.0/gems/faraday-retry-2.4.0/lib/faraday/retry/middleware.rb:171:in 'block in Faraday::Retry::Middleware#call'
        from /Users/kieran/.asdf/installs/ruby/4.0.0/lib/ruby/gems/4.0.0/gems/faraday-retry-2.4.0/lib/faraday/retry/retryable.rb:7:in 'Faraday::Retryable#with_retries'
        from /Users/kieran/.asdf/installs/ruby/4.0.0/lib/ruby/gems/4.0.0/gems/faraday-retry-2.4.0/lib/faraday/retry/middleware.rb:167:in 'Faraday::Retry::Middleware#call'
        from /Users/kieran/.asdf/installs/ruby/4.0.0/lib/ruby/gems/4.0.0/gems/faraday-2.14.0/lib/faraday/middleware.rb:56:in 'Faraday::Middleware#call'
        from /Users/kieran/.asdf/installs/ruby/4.0.0/lib/ruby/gems/4.0.0/gems/faraday-2.14.0/lib/faraday/response/logger.rb:25:in 'Faraday::Response::Logger#call'
        from /Users/kieran/.asdf/installs/ruby/4.0.0/lib/ruby/gems/4.0.0/gems/faraday-2.14.0/lib/faraday/rack_builder.rb:153:in 'Faraday::RackBuilder#build_response'
        from /Users/kieran/.asdf/installs/ruby/4.0.0/lib/ruby/gems/4.0.0/gems/faraday-2.14.0/lib/faraday/connection.rb:452:in 'Faraday::Connection#run_request'
        from /Users/kieran/.asdf/installs/ruby/4.0.0/lib/ruby/gems/4.0.0/gems/faraday-2.14.0/lib/faraday/connection.rb:280:in 'Faraday::Connection#post'
        from /Users/kieran/.asdf/installs/ruby/4.0.0/lib/ruby/gems/4.0.0/gems/ruby_llm-1.11.0/lib/ruby_llm/connection.rb:37:in 'RubyLLM::Connection#post'
        from /Users/kieran/.asdf/installs/ruby/4.0.0/lib/ruby/gems/4.0.0/gems/ruby_llm-1.11.0/lib/ruby_llm/streaming.rb:11:in 'RubyLLM::Streaming#stream_response'
        from /Users/kieran/.asdf/installs/ruby/4.0.0/lib/ruby/gems/4.0.0/gems/ruby_llm-1.11.0/lib/ruby_llm/provider.rb:57:in 'RubyLLM::Provider#complete'
        from /Users/kieran/.asdf/installs/ruby/4.0.0/lib/ruby/gems/4.0.0/gems/ruby_llm-1.11.0/lib/ruby_llm/chat.rb:133:in 'RubyLLM::Chat#complete'
        from /Users/kieran/.asdf/installs/ruby/4.0.0/lib/ruby/gems/4.0.0/gems/ruby_llm-1.11.0/lib/ruby_llm/chat.rb:36:in 'RubyLLM::Chat#ask'
        from 3_query_database.rb:38:in '<main>'