Claude Opus 5.5 changelog

Every change to Claude Opus 5.5 that Modelpeers has recorded, newest first, each with the source it came from. The record starts Sep 1, 2026.

All (22)Releases (5)Breaking changes (4)Prices/limits (2)Quality (4)Benchmarks (7)

October 2026

Perplexity Agent API and Claude Opus 5.5

2 products from Perplexity AI and Anthropic

Limits change3d

Perplexity Agent API xhigh effort raises max steps from 100 to 300

The xhigh level stays on Claude Opus 5.5 with GPT-6.1 Sol as fallback. Context compaction starts at 150,000 tokens, and it no longer sends a system prompt.

Before

100 max steps

After

300 max steps

Who is affected:: Agent API users on xhigh effort or frozen configurations.
What to do:: Copy the updated values if you use a frozen configuration.

September 2026

Claude Opus 5.5 and Claude Code

2 products from Anthropic

Limits changeSep 22, 2026

Five-hour usage limits raised with Opus 5.5, plus a saved limit reset

Alongside Opus 5.5, Anthropic raised five-hour usage limits on Pro, Max, Team and seat-based Enterprise plans and gave subscribers one rate limit reset they can use when they choose.

3 incidents are listed on the Claude Opus 5.5 page. Get this changelog in a feed reader with the RSS feed.