Initial notes on GPT-5.2 - I'm excited to see the knowledge cut-off bump up to August 2025, interesting that it's priced at 1.4x over GPT-5.1

Simon Willison’s Weblog

GPT-5.2

OpenAI reportedly declared a “code red” on the 1st of December in response to increasingly credible competition from the likes of Google’s Ge...

I put together a detailed collection of useful patterns I've collected after vibe-coding 150 different single-file HTML tools over the past couple of years

Simon Willison’s Weblog

Useful patterns for building HTML tools

I’ve started using the term HTML tools to refer to HTML applications that I’ve been building which combine HTML, JavaScript, and CSS in a singl...

I've never been particularly invested in light mode v.s. dark mode but I got enough complaints from people that my blog was "blinding" that I had Claude Code knock out a dark mode theme for it, and it seems to work pretty well

Simon Willison’s Weblog

Dark mode

I've never been particularly invested dark v.s. light mode but I get enough people complaining that this site is "blinding" that I decided to see i...

Put together some notes on Mistral Vibe, Mistral's new CLI coding agent (think Claude Code / OpenAI Codex) which is Apache 2 licensed, written in Python+Pydantic+Textual and has a neat set of system and tool definition prompts that are fun to read

Simon Willison’s Weblog

mistralai/mistral-vibe

Here's the Apache 2.0 licensed source code for Mistral's new "Vibe" CLI coding agent, released today alongside Devstral 2. It's a neat implementati...