Anthropic releases Sonnet 5.5, which it calls a significantly cheaper, faster work partner

Practical AI: Tools, Models & Frameworks

What changed

As the AI model wars continue, Anthropic has released the newest version of Sonnet, the company’s mid-tier model, which it says will work much faster (and for significantly less) than its predecessor. Sonnet 5, 5.5’s predecessor, was announced about three months ago. Just last week, OpenAI released a number of new models — including enhanced versions of Sol and Luna, its mid-tier and budget-friendly models.

Why it matters

A concrete addition to Practical AI: Tools, Models & Frameworks: it changes what's available to builders today rather than being general commentary.

How it compares

Related prior coverage to compare against:

  • Binary and Scalar Embedding Quantization for Significantly Faster & Cheaper Retrieval
  • Faster Gemma 4 on MLX with multi-token prediction
  • Claude Code with Anthropic API compatibility

Sources