How often does Anthropic update Claude Sonnet?

Based on the public history through early 2026, Anthropic has shipped Sonnet snapshots roughly every 4–6 months. Known dated releases: claude-3-sonnet-20240229 (Feb 29 2024), claude-3-5-sonnet-20240620 (Jun 20 2024), claude-3-5-sonnet-20241022 (Oct 22 2024 — the "new Sonnet"), with the Claude 3.7 / 4 family arriving in 2025. Between named snapshots, Anthropic occasionally updates the claude-3-5-sonnet-latest alias and the underlying serving stack — these changes don't get new dated snapshots but can shift behavior measurably.

What "update" means specifically: (a) major snapshots — new dated model, sometimes a new model number, accompanied by a release post and benchmark numbers. These are the big, intentional capability jumps. (b) alias re-points — *-latest moves to a new snapshot without code changes on your end. (c) silent serving updates — same snapshot string, but safety classifiers, system-prompt defaults, or infrastructure quantization changes. Anthropic is more explicit than OpenAI about (a) and (b); (c) is documented at the policy level but not on specific change dates.

To track all three, subscribe to docs.anthropic.com/changelog, watch the deprecation page, and run dated eval baselines on both the pinned snapshot and the *-latest alias. ModelWatch does this automatically for every Anthropic model.