Claude's 1 Million Token Context Window: Analyzing Entire Codebases in a Single Prompt

The Entire Codebase in One Prompt

Claude Opus 4.6 launched with a 1 million token context window on February 5, 2026, with Sonnet 4.6 following on February 17 (in beta). This is a game-changer for developers and researchers working with large documents and codebases.

What 1 Million Tokens Means

For reference, 1 million tokens is approximately:

• ~750,000 words of text
• ~15,000 pages of documentation
• An entire medium-sized codebase loaded at once

Retrieval Quality

On MRCR v2, a needle-in-a-haystack benchmark testing information retrieval in vast text:

Model	Score
Claude Opus 4.6	76%
Claude Sonnet 4.5	18.5%

Opus 4.6 is 4x better at finding specific information buried in massive context — critical for codebase-wide searches and long-document analysis.

Practical Applications

• Full codebase review — Load an entire project for comprehensive analysis
• Legal document processing — Analyze complete contract sets simultaneously
• Research synthesis — Process dozens of papers in a single conversation
• Code migration — Understand source and target codebases at once

Pricing

The 1M context window is available at standard per-token pricing:

• Opus 4.6: $15/$75 per million tokens
• Sonnet 4.6: $3/$15 per million tokens (beta)

This matches Google's Gemini 3 Pro, which also offers 1 million token context.

Source: Anthropic | philippdubach.com | Claude API Docs