[BUG] RubyLLM::Content missing #empty? method causes NoMethodError in Anthropic provider

[judy]

Description

RubyLLM::Content does not implement #empty?, but several Anthropic provider code paths call msg.content.empty? on message content. When a message has ActiveStorage attachments, extract_content (in active_record/message_methods.rb) wraps the content in a Content object instead of returning a plain String. This causes a NoMethodError when the message is later formatted for the Anthropic API.

Steps to reproduce

1. Create a message with ActiveStorage attachments (e.g., via has_many_attached :attachments on the message model)
2. Have the agent respond with tool calls in the same conversation
3. On the next turn, extract_content returns a RubyLLM::Content for the user message with attachments
4. The Anthropic provider calls msg.content.empty? during format_tool_call_with_thinking or format_tool_result
5. NoMethodError: undefined method 'empty?' for an instance of RubyLLM::Content

Affected code paths

• lib/ruby_llm/providers/anthropic/chat.rb:179 — msg.content.nil? || msg.content.empty?
• lib/ruby_llm/providers/anthropic/tools.rb:19 — msg.content.nil? || msg.content.empty?

Expected behavior

RubyLLM::Content should respond to #empty? (returning true when text is nil and attachments are empty), consistent with how String and Array respond to it.

Workaround

RubyLLM::Content.class_eval do
  def empty?
    text.nil? && attachments.empty?
  end
end

Environment

• ruby_llm 1.14.0
• Rails 8.1 with ActiveStorage
• Anthropic provider (Claude models)