Claude Code changelog

Every change to Claude Code that Modelpeers has recorded, newest first, each with the source it came from. The record starts Jul 17, 2025.

All (40)Breaking changes (9)Prices/limits (18)Quality (10)Benchmarks (3)

October 2026

Claude Opus 5.5 and Claude Code

2 products from Anthropic

Benchmark3w

Opus 5.5 in Claude Code tops the official Terminal-Bench 4.0 leaderboard at 64.8%

Claude Code with Opus 5.5 at max effort resolved 64.85% of Terminal-Bench 4.0 tasks (plus or minus 3.1, 330 trials, $4,718.65 total cost), ranked first. The entry was posted October 6, 2026.

Claude Sonnet 5.5 and Claude Code

2 products from Anthropic

Benchmark3w

Sonnet 5.5 in Claude Code scores 61.8% on Terminal-Bench 4.0

Claude Code with Sonnet 5.5 at max effort resolved 61.82% (plus or minus 2.9, 330 trials, $7,333.64 total cost), second on the leaderboard. Posted October 6, 2026.

September 2026

Claude Opus 5 and Claude Code

2 products from Anthropic

BenchmarkSep 17, 2026

Opus 5 in Claude Code scores 53.9% on Terminal-Bench 4.0 at xhigh effort

Claude Code with Opus 5 scored 53.94% at xhigh, 51.82% at max (posted August 27), 50.3% at high, 44.85% at medium and 34.85% at low, each over 330 trials.

Who is affected:: Teams still on Opus 5 deciding whether to move to Opus 5.5.
What to do:: Compare against Opus 5.5 (64.85%) before upgrading.

43 incidents are listed on the Claude Code page. Get this changelog in a feed reader with the RSS feed.