Claude Haiku 5.5 and Sonnet 5.5 — capabilities, prices, and which model to choose?

The most expensive model does not have to be the best choice for every task.

In a well-designed system, a difficult decision and quick classification can go to different performers.

Haiku 5.5 and Sonnet 5.5 should be compared as roles in a process, rather than participants in a duel where one must eliminate the other.

Two releases, different tasks Sonnet 5.5 was announced on September 28, 2026.

Anthropic positions it as a model for daily work, code correction, and document preparation.

The manufacturer reports 70.6% in Terminal-Bench 4.0, but notes the superiority of Opus in complex tasks requiring prolonged judgment.

We did not conduct our own benchmark.

Source: Sonnet 5.5 launch .