Claude Sonnet 3.5 is a large language model created by Anthropic, released June 20, 2024 — the first model in the 3.5 generation.

The model was deprecated on 2025-08-13 and retired on 2025-10-28; requests to it via the API now fail.

Details

• Launched alongside Artifacts in the Claude.ai interface.
• Same 200K context as Claude 3, with max output raised to 8,192 tokens.
• Priced identically to Claude 3 Sonnet ($3 / $15 per million tokens) while substantially outperforming Claude 3 Opus on Anthropic’s reported benchmarks.
• The October 22, 2024 “upgraded Claude 3.5 Sonnet” — colloquially Sonnet 3.6 — shipped under the same family but a new snapshot.