Modelpeers

Claude Sonnet 4.6 changelog

Every change to Claude Sonnet 4.6 that Modelpeers has recorded, newest first, each with the source it came from. The record starts Apr 23, 2026.

All (1)Quality (1)

April 2026

Claude Code character

Claude Code, Opus 4.6, Sonnet 4.6

4 products from Anthropic

Quality report · Confirmed by the lab

Anthropic confirms three changes degraded Claude Code quality

Anthropic traced user reports of worse Claude Code answers to a lower default effort (March 4 to April 7), a bug that dropped older reasoning every turn (March 26 to April 10) and a verbosity prompt change (April 16 to 20). The API was not affected, and Anthropic reset usage limits for all subscribers on April 23.

Who is affected:
Claude Code, Agent SDK and Cowork users on Sonnet 4.6, Opus 4.6 and Opus 4.7 between March and April 2026.
Action needed:
Update Claude Code to 2.1.116 or later.

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