Anthropic
Claude Sonnet 5.5
Announced Sep 28, 2026
Faster everyday coding and documents
What could it do?
Anthropic reported improvements in focused tasks, bug fixes and document creation.
What changed?
A faster and lower cost update to Sonnet 5.
Expanded the Claude 5.5 family beyond Opus.
Where it fell short
The launch describes typical cost changes, not a saving guaranteed for every task.
Release facts were checked against the sources below. Performance claims belong to the developers; we have not independently tested these models.
Developer announcement or release logBenchmark results
A benchmark estimate, not a percentage or capability multiplier. Reasoning settings are not specified in this source table. Historical estimates can change in later snapshots.
Epoch AI methodology ↗Download the source snapshotChecked Oct 7, 2026 · CC BY 4.0Selected highest effort variant where available in the current table. Starred partial results are excluded. Claude fallback configurations can use other models when safeguards intervene.
Source: Artificial Analysis Intelligence Index ↗Download selected resultsChecked Oct 8, 2026One explicitly named variant per release. Scores come from the same Overall snapshot; preliminary entries and reported intervals are preserved. These are current ratings of earlier variants, not their launch day ratings.
Source: Text Arena ↗Download selected resultsChecked Oct 8, 2026