Claude Opus 4.6 vs Opus 4.5: What 1M Context Means for Devs

Claude Opus 4.6 is an upgrade to Opus 4.5 with a 1M token context window (up from 200K), improved coding performance, and better long-context retention at the same $5/$25 MTok pricing. This guide compares both models and explains when the larger context window makes a meaningful difference for developers.

TL;DR

• Opus 4.6 expands the context window from 200K to 1M tokens, enabling full large-codebase navigation without chunking.
• Coding quality and long-context retention are improved in 4.6 compared to 4.5.
• Use 4.6 for large codebases, multi-file refactors, and long documentation; 4.5 is fine for typical single-file or small-scope work.
• Longer context typically costs more per request; compare pricing if you are cost-sensitive.
• Opus 4.5 remains available for backward compatibility; 4.6 is rolling out across Claude Code, Cursor, and the Claude API.

Quick Answer

Opus 4.6 adds 1M context (vs 200K in 4.5) and refinements for coding. Use 4.6 for large codebases, multi-file refactors, and long docs. 4.5 remains strong for typical tasks and may be cheaper. Availability depends on your tool (Cursor, Claude Code, API, etc.).

Key Differences

When 4.6 Matters

When 4.5 Is Enough

Where to Use Each

• Claude Code: Check which Opus version is default; switch if needed.
• Cursor: Pro+ and Ultra typically offer latest Claude models; verify in model picker.
• Claude API: Both 4.5 and 4.6 available; choose by context needs.
• Windsurf, Copilot: Model availability varies; see each tool's docs.

Practical Takeaway

For most coding tasks, 4.5 is still excellent. Upgrade to 4.6 when you routinely hit context limits or work with very large codebases. Compare pricing if you are cost-sensitive. See Claude Code and Cursor for integration details.