Claude Sonnet 5.6

Tracked as: Claude Sonnet 5.6 / Sonnet 5.7

Estimated release

Dec 15, 2026

Mid Dec 2026

Details

Status: Not announced; Sonnet 5.5 shipped Sept 28
Current model: Claude Sonnet 5.5, 56 on the Intelligence Index, released Sep 28, 2026 ()
Projected score: About 59 (+3)
Typical cycle: About 90 days between releases

Sonnet ships less often than Opus: 4.5 (Sept 29, 2025), 4.6 (Feb 17), 5 (Jun 30) and 5.5 (Sept 28), so every 3 to 5 months
Sonnet usually lands within about two weeks of the matching Opus (Opus 4.6 Feb 5 then Sonnet Feb 17; Opus 5.5 Sept 22 then Sonnet Sept 28), so this follows the Opus 5.6 forecast
Sonnet skipped Opus 4.7 and 4.8, so it may skip 5.6 too and wait for a later version, which would push this into 2027
Sonnet 5.5 (56, $2/$10) is only 1.6 points under Opus 5.5 and runs about 50% faster; the projection assumes about +3

Source: Anthropic Sonnet 5.5 launch (Sept 28, 2026) & release history (Artificial Analysis API v2)