Simon Willison's LLM CLI adds a Claude Opus 5.5 option

single source· 1 articles · confidence: low · first seen 2026-09-22 17:14 UTC

What this means for you

If you use llm-anthropic, upgrading to 0.29 gives you the claude-opus-5.5 alias; that is all the release note supports doing. No price or capability is stated, so there is nothing to plan or migrate around yet.

Simon Willison's llm-anthropic plugin, which lets the LLM command-line tool send prompts to Anthropic's models, reached version 0.29 on 22 September 2026 and added support for a model it calls Claude Opus 5.5, invoked as `llm -m claude-opus-5.5`. That is the whole of the release note: no pricing, context limits, evaluation results or availability date are given, and nothing describes how Opus 5.5 differs from earlier Claude models. The post is tagged llm and anthropic.

Models in this story

Key facts

  • ·llm-anthropic 0.29 was released on 22 September 2026. source
  • ·The release adds support for a model named Claude Opus 5.5. source
  • ·The model is selected by passing claude-opus-5.5 to the LLM tool's -m flag. source
  • ·The release note gives no price, context window, evaluation date or availability details for Claude Opus 5.5. source
  • ·The post is tagged llm and anthropic, naming the tool and the model maker. source

What the sources say

  • Simon Willison (press) — A one-line release note recording the plugin version and the model alias it exposes.

Sources

The original reporting. Follow these — they did the work.

← the wire