Simon Willison’s Weblog

22nd September 2026

Release llm-anthropic 0.29 — LLM access to models by Anthropic, including the Claude series

Adds support for Claude Opus 5.5:

llm -m claude-opus-5.5 "prompt goes here"

Posted 22nd September 2026 at 5:14 pm

Recent articles

Claude Opus 5.5, GPT-6 Sol, GPT-6 Luna, and a new price war - 22nd September 2026
Jev introduces a new shape of LLM - System One, aka Decision Models - 21st September 2026
Generating running routes with GPT-6 Astra and ChatGPT Work - 12th September 2026

This is a beat by Simon Willison, posted on 22nd September 2026.

llm 635 anthropic 340

Monthly briefing

Sponsor me for $10/month and get a curated email digest of the month's most important LLM developments.

Pay me to send you less!

Sponsor & subscribe