Anthropic Launches Claude Sonnet 5 at Steep Discount to Its Top Model as the Company Races Toward a Blockbuster IPO

What happened

Anthropic released Claude Sonnet 5 on June 30, 2026 — a new model for coding, reasoning, and agentic workflows with a native 1M-token context window. The model immediately became the default for Free and Pro users and for Claude Code.

Context and impact

Sonnet 5 is part of Anthropic's strategy ahead of a planned IPO, with annualized revenue exceeding $30 billion. Important caveat flagged by Simon Willison: the new tokenizer produces ~30% more tokens for English text, which partially offsets the pricing advantage. Adaptive thinking is on by default and sampling parameters (temperature, top_p, top_k) are no longer supported.

Details

• Promo pricing: $2/$10 per 1M tokens (through Aug 31, 2026)
• Native context: 1 million tokens
• Default model for Free and Pro plans immediately upon launch
• New tokenizer: ~30% more tokens for English text (real costs higher than advertised)
• Adaptive thinking enabled by default
• temperature, top_p, top_k sampling parameters no longer supported