Claude 4.5 Opus Soul Document

Introducing Claude Opus 4.6

Claude Opus 4.8: The System Card

Only six weeks after Opus 4.7, we have Opus 4.8.

Claude Opus 5: The System Card

Claude Opus 5 is trying to be the best of both worlds.

AI #165: In Our Image

This was the week of Claude Opus 4.7.

Introducing Claude Opus 5.5

Claude Opus 5.5 leads in agentic coding and knowledge work, and costs 40% less to run than Opus 5 on typical workloads.

Introducing Claude Opus 5

Opus 5 is a step change improvement for the Opus tier powering long-running agents while delivering improvements in coding and professional work.

Claude Opus 4.7 Is Here: Release Confirmed April 16, 2026

Claude Opus 4.7 shipped April 16, 2026. SWE-bench 87.6%, xhigh mode, /ultrareview, 2,576px vision. Read our full first-look review.

Claude's new constitution

A new approach to a foundational document that expresses and shapes who Claude is

Opus 4.7 isn't dumb, it's just lazy — Shimin Zhang

Some follow up experiments with Claude Opus 4.7 based on Simon Willison's Pelican Benchmark Shocker.

Claude Opus 5 Is Highly Capable, But Is No Mythos

Claude Opus 5 is a weirder than usual release to evaluate, for two reasons.

Did Claude 3 Opus align itself via gradient hacking? — LessWrong

> Claude 3 Opus is unusually aligned because it’s a friendly gradient hacker. It’s definitely way more aligned than any explicit optimization targets…

Prompting Claude Opus 5

Behavioral differences and prompting patterns for Claude Opus 5, covering response verbosity, agentic narration, task scoping, subagent delegation, self-correction, and output artifacts when thinking is disabled.

GitHub - simonw/claude-code-transcripts: Tools for publishing transcripts for Claude Code sessions

Tools for publishing transcripts for Claude Code sessions - simonw/claude-code-transcripts