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Claude Sonnet

Anthropic

Anthropic's mid-tier Claude model and its production default for coding, positioned between Haiku (small/fast) and Opus (heavy reasoning). Tracked as a tier rather than a point release, so the generation currently shipping is scored and the measured release is named in the score note. Generations to date are Sonnet 4 (May 2025), Sonnet 4.5 (Sept 2025), Sonnet 4.6 (Feb 2026) and Sonnet 5 (June 2026). Closed weights, available through the Anthropic API and the Claude apps.

Tier product. Anthropic ships a new Sonnet roughly every few months, so a versioned entry goes stale faster than it can be reviewed; the slug is stable and the score carries the release it was measured against. Supersedes the separate claude-sonnet-4 and claude-sonnet-4-6 entries.

Openness

1 high confidence
1.0
weights
closed
data
closed
code
closed
license
Proprietary(API-only)

Closed by construction and stable across generations - no Sonnet release has ever shipped weights, so this axis does not move when the tier advances. Measured against Claude Sonnet 4.6 (released 2026-02-17), Anthropic's production default coding tier at the time of scoring.

Adoption

5 medium confidence
5.0

Highest-adoption tier of the three Claude model tiers - Sonnet is the production default for coding and the model most API traffic lands on. Directional rather than measured; no per-model usage figure is published, so this is a reported-traction judgment.

Capability

4 medium confidence
4.0

Sonnet 4.6 posts 79.6% on SWE-bench Verified, strong for a mid-tier model but below the Opus and Fable tiers, which is why this sits at 4 rather than 5. Confidence is medium because SWE-bench Verified's public leaderboard has had no submissions since 2025-12-15, so recent figures are vendor-reported.

Unchanged since 2026-07-29 (last edited, not re-checked)