Anthropic ships Sonnet 5.5, claiming 30% speedup and lower token burn
The mid-tier model is pitched on speed and cost and, for the first time, sits under flagship-grade cyber safeguards; independent benchmarks are still pending.
Original event 2026-09-28
Anthropic released Claude Sonnet 5.5, its mid-tier model, on September 28 — about three months after its predecessor, Sonnet 5.
The company says the new model is 30 percent faster than its predecessor with significantly slower token burn, and its own benchmarks show it beating the flagship Opus 5.5 on agentic coding, which Anthropic attributes to spawning multiple agents without exceeding cost limits. These figures are Anthropic's own; no independent testing is cited.
One structural change: Anthropic says 5.5 is the first Sonnet model subject to the same cyber safeguards that apply to Opus, after claiming its cyber capabilities are now "comparable" to Opus 5. A new version of the smallest model, Haiku, is planned in the coming weeks, with no date given.