Add configurable Anthropic API base URL

[ericproulx]

Summary

Adds support for configurable Anthropic API base URL through a new anthropic_api_base configuration option. This allows users to point to custom endpoints such as proxies, custom deployments, or alternative Anthropic-compatible services.

Changes

• Configuration: Added anthropic_api_base configuration attribute
• Provider: Modified Anthropic provider to use custom base URL when configured, with fallback to default https://api.anthropic.com
• URL Fixes: Removed leading slashes from API endpoint paths in chat and models modules for proper URL construction
• Console: Updated bin/console to support ANTHROPIC_BASE_URL environment variable
• Tests: Added comprehensive test coverage for the new configuration option

Use Cases

This enhancement enables:

• Using proxy servers for Anthropic API requests
• Custom deployments of Anthropic-compatible services
• Testing against mock servers
• Regional or enterprise-specific endpoints

Configuration Example

RubyLLM.configure do |config|
  config.anthropic_api_key = "your-api-key"
  config.anthropic_api_base = "https://custom-anthropic-endpoint.example.com"
end

Or via environment variable:

export ANTHROPIC_BASE_URL="https://custom-anthropic-endpoint.example.com"

Backward Compatibility

✅ Fully backward compatible - defaults to official Anthropic API endpoint when not configured

[michaelwapp]

Is there an ETA when this feature will be merged?

[ericproulx]

@michaelwapp I've just rebased it. Hopefully, someone will pick it up.

[codecov]

Codecov Report

❌ Patch coverage is 66.66667% with 1 line in your changes missing coverage. Please review.
✅ Project coverage is 80.89%. Comparing base (18c6e13) to head (f6d1925).
⚠️ Report is 3 commits behind head on main.

Files with missing lines	Patch %	Lines
lib/ruby_llm/providers/anthropic/models.rb	0.00%	1 Missing ⚠️

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #589   +/-   ##
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  Coverage   80.89%   80.89%           
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  Files         113      113           
  Lines        5098     5098           
  Branches     1309     1309           
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  Hits         4124     4124           
  Misses        974      974           

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[crmne]

Thanks for the contribution. I’m going to move this forward to keep momentum and handle the small docs/process follow-up on maintainer side.

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