Simon Willison’s Weblog

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Friday, 12th December 2025

LLM 0.28. I released a new version of my LLM Python library and CLI tool for interacting with Large Language Models. Highlights from the release notes:

  • New OpenAI models: gpt-5.1, gpt-5.1-chat-latest, gpt-5.2 and gpt-5.2-chat-latest. #1300, #1317
  • When fetching URLs as fragments using llm -f URL, the request now includes a custom user-agent header: llm/VERSION (https://llm.datasette.io/). #1309
  • Fixed a bug where fragments were not correctly registered with their source when using llm chat. Thanks, Giuseppe Rota. #1316
  • Fixed some file descriptor leak warnings. Thanks, Eric Bloch. #1313
  • Type annotations for the OpenAI Chat, AsyncChat and Completion execute() methods. Thanks, Arjan Mossel. #1315
  • The project now uses uv and dependency groups for development. See the updated contributing documentation. #1318

That last bullet point about uv relates to the dependency groups pattern I wrote about in a recent TIL. I'm currently working through applying it to my other projects - the net result is that running the test suite is as simple as doing:

git clone https://github.com/simonw/llm
cd llm
uv run pytest

The new dev dependency group defined in pyproject.toml is automatically installed by uv run in a new virtual environment which means everything needed to run pytest is available without needing to add any extra commands.

# 8:20 pm / projects, python, ai, annotated-release-notes, generative-ai, llms, llm, uv

OpenAI are quietly adopting skills, now available in ChatGPT and Codex CLI

Visit OpenAI are quietly adopting skills, now available in ChatGPT and Codex CLI

One of the things that most excited me about Anthropic’s new Skills mechanism back in October is how easy it looked for other platforms to implement. A skill is just a folder with a Markdown file and some optional extra resources and scripts, so any LLM tool with the ability to navigate and read from a filesystem should be capable of using them. It turns out OpenAI are doing exactly that, with skills support quietly showing up in both their Codex CLI tool and now also in ChatGPT itself.

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2025 » December

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