Originally published on the Cosmic blog.
Anthropic shipped Claude Sonnet 5 on June 30, 2026 and Claude Opus 5 on July 24, 2026. Both are excellent. The expensive mistake is picking one, wiring it into every code path, and then either overpaying on trivial work or under-resourcing the work that actually matters.
This is the practical breakdown: what each model is measurably good at, what the same job costs on each once you account for tokenization, and a routing rule you can ship this week.
The short answer
Your workload
