What is the difference between Claude 4 Sonnet and Claude Sonnet 4.6?

Claude Sonnet 4.6 is the official successor to Claude 4 Sonnet. It costs the same ($3/$15 per 1M tokens) but has a 5x larger context window (200K vs 40K tokens) and improved performance. The API format is identical.

Is Claude 4 Sonnet still available?

No. Claude 4 Sonnet was retired on June 15, 2026. All API calls return 410 Gone errors. You must migrate to Claude Sonnet 4.6 or another alternative.

How do I migrate from Claude 4 Sonnet to Sonnet 4.6?

Replace 'claude-4-sonnet' with 'claude-sonnet-4-6' in your code. No other changes needed — same API, same SDK, same parameters. Takes 15-30 minutes.

Claude 4 Sonnet vs Claude Sonnet 4.6 — What Changed?

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