Problem to solve

As a GitLab Duo user, I want to leverage the full 1M context window now available for Claude Opus 4.6 and Sonnet 4.6, so I can work with larger codebases and documents in a single conversation without context truncation.

Anthropic announced general availability of 1M context window (March 13, 2026) with:

• Standard pricing across full 1M window (no long-context premium)
• Full rate limits at every context length
• No beta header required for requests over 200K tokens

Proposal

Update AI Gateway to support the full 1M context window for Claude Opus 4.6 and Sonnet 4.6 models.

Implementation Plan

1. Update Model Configuration

   • Update models.yml to reflect 1M (1,000,000) token context window for Claude Opus 4.6 and Sonnet 4.6
   • Remove any 200K context limit restrictions

2. Remove Beta Header Requirements

   • Identify and remove any anthropic-beta header logic for long-context requests
   • Requests over 200K tokens should work automatically

3. Testing

   • Add/update tests for 1M context window support
   • Verify no regression in existing functionality

Further details

Benefits:

• Users can process entire codebases in a single session
• Improved accuracy for large document analysis (Opus 4.6 scores 78.3% on MRCR v2)
• No additional cost for long-context requests

Acceptance Criteria:

• Claude Opus 4.6 and Sonnet 4.6 accept up to 1M tokens in context
• No beta headers required for long-context requests
• All existing tests pass

Links / references

• Anthropic announcement: https://claude.com/blog/1m-context-ga