Claude Opus 4.7 changelog

MarginLab tracker measures a five-day Claude Code drop tied to CLI version 2.1.150

MarginLab's daily SWE-Bench-Pro subset run of Claude Code (50 tasks per day) fell from a 65% Opus 4.7 baseline to 50 to 54% from May 22 to May 26, 2026, and recovered to 66% when version 2.1.153 landed. Tool calls per task rose about 60% over the same days, and MarginLab concluded it was a harness issue, not a model regression.

Who is affected:

Claude Code users on CLI versions 2.1.150 to 2.1.152 in late May 2026.

What to do:

No action needed. Later CLI versions recovered.

Claude Code regression: malware reminder makes subagents refuse legitimate edits

A GitHub issue opened April 16, 2026 reported that Claude Code v2.1.111 still injects a malware system reminder into every file read, causing Opus 4.7 subagents to refuse code edits, after an earlier fix in v2.1.92. The thread drew 252 points and 147 comments.

Who is affected:

Claude Code users running subagents that edit code.

What to do:

Update Claude Code and report refusals with /feedback.

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.