The newest Claude Sonnet model is Claude Sonnet 5.5, released on September 28, 2026. It shipped 26 days ago, and the line's usual gap is about 130 days.
How long it has been since the last release against the line's usual gap and its recent ones — the rhythm, not a date.
Latest: Claude Sonnet 5.5 · Sep 28, 2026
Every Monday, only when something shipped: the AI models that came out, what each one changed, and which lines are due next.
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Newest first — what each version changed versus the one before, in Anthropic's own numbers.
Scores 18 points higher than Sonnet 5 on the all-round intelligence index and runs over 30% faster, at the same $2 / $10 price per 1M tokens.
Compared with Claude Sonnet 5 · the model it replaces
Makes the right code edits more than half the time inside an editor
CursorBench 4.0 — editing code the way developers do in an IDE
55.5%
▲ up from 34.1% · +21.4 points
Scores 18 points higher on the all-round intelligence index
Artificial Analysis Intelligence Index v4.3.2 — one score averaging 10 hard tests
56
▲ max effort (Artificial Analysis: max with fallback) · up from 38 · +18 points
Costs the same as the model it replaces
Price per 1M tokens — what developers pay, input / output
$2 / $10
same as Claude Sonnet 5
Replaced Sonnet 4.6 as the default model on Anthropic's Free and Pro plans, priced at $2 per million input tokens and $10 per million output tokens.
Claude Sonnet 4.5 completes 61.4% of OSWorld computer tasks, up from 42.2% for Claude Sonnet 4, at the same $3 / $15 price per 1M tokens.
Compared with Claude Sonnet 4 · the model it replaces
Fixes more than 3 in 4 real software bugs
SWE-bench Verified — fixing real bugs in real software projects
77.2%
▲ up from 72.7% · +4.5 points · Sonnet 4.5 with a 200K thinking budget and a short extra prompt, Sonnet 4 without extended thinking
Costs the same as the model it replaces
Price per 1M tokens — what developers pay, input / output
$3 / $15
same as Claude Sonnet 4
Anthropic's upgrade to Claude Sonnet 3.7 for coding and reasoning, 65% less likely to take shortcuts on agentic tasks, made available to free users at the same API price.
The first Claude model that can either answer at once or think step by step first, with developers setting a thinking budget in the API, at the same price as Claude 3.5 Sonnet.
The middle model of the Claude 3 family, available in the API on launch day with a 200K-token context window.
Costs developers $3 per million input tokens
Price per 1M tokens — what developers pay, input / output
$3 / $15
✦ launch price — nothing earlier to compare