Simon Willison
1 Tool · 139 Intel
Simon Willison is a British software developer and writer based in San Francisco, best known as a co-creator of the Django web framework, which he helped build in 2003-2004 while working at the Lawrence Journal-World. He later worked as a software architect at The Guardian, co-founded the Y Combinator-backed startup Lanyrd (acquired by Eventbrite) with his wife Natalie Downe, and has served on the board of the Python Software Foundation since 2022. He has maintained a widely read technical blog, simonwillison.net, since 2002 and is known for coining the term "prompt injection" to describe a security risk in large language model applications.
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Tools
Policy-driven sandbox for running untrusted code on Windows, Linux and macOS with multiple isolation backends.
Intel
Simon Willison's llm CLI ships version 0.35, adding support for OpenAI's new gpt-6-astra model so it can be queried from the command line alongside every other model the tool already supports.
A prototype for storing revision histories by keeping every prior version in one JSON array of strings and compressing the whole thing with zlib or zstd, on the theory that all the repeated text compresses away.
Simon Willison documents using ChatGPT Codex with the full macOS Blender application to generate and iteratively refine .blend scenes and renders via Blender's Python API, driven entirely by plain-language follow-up prompts.
GitHub Models has been retired, removing the unified LLM API whose main draw was that code running in GitHub Actions could execute prompts with the token already present in the environment.
Commentary on Anthropic's move from Git to a custom centralized system, driven by a twelvefold rise in daily merged changes and 25 million daily CI checkouts. Annotates the growth chart with model release dates to suggest what drove coding velocity.
Armin Ronacher on the shared language of a software project being neither English nor Python, but the common understanding of what its concepts mean, where the boundaries are and which invariants matter.
A look at how OpenAI's research team leans on coding agents internally, anchored by a chart showing a sharp jump in AI spend per researcher in late July, likely tied to early internal access to the model later released as GPT-6 Astra.
Anthropic's Frontier Red Team reports GLM-5.3 produces full control-flow hijacks in 4% of binary exploitation tasks, near Claude Mythos Preview's 6%, while GLM-5.2 and Claude Opus 4.6 solved none.
A hands-on pass at Fable 5.1's five reasoning levels, including a llm-anthropic fix for missing reasoning traces and a mystery where low and medium return none, set against Anthropic's headline 52.6% on the new Terminal-Bench-Science 0.1 benchmark.
datasette-agent 0.4a0 adds a browser_task mechanism letting agent tools run custom JavaScript directly in the user's browser.
A project by Puter that compiles the full Firefox/Gecko browser to WebAssembly so an entire browser can run inside another browser tab. Network traffic is proxied over the Wisp WebSocket protocol to work around browser networking limits, with end-to-end encryption for HTTPS sites.
Simon Willison argues that LLMs like Claude and Codex have made the classic open-source promise of user-modifiable software newly practical: anyone can now ask an AI assistant to clone, build, and explain an unfamiliar codebase in minutes, removing the friction that once made 'read the source' an empty freedom for most users.
A close read of what changed between Claude's Fable 5 and 5.1 consumer system prompts: a substantial new block forbidding reproduction of song lyrics and copyrighted characters, dropped end_conversation guidance, answering-style tweaks, and a June 2026 cutoff. Includes a .md trick for diffing the do
Simon Willison walks through chaining ChatGPT image generation, Codex on GPT-6 Astra with a custom Blender skill file, and a browser-based .blend viewer to turn a generated image into an inspectable 3D model.
OpenAI's account of two evaluation incidents in which a testing-environment misconfiguration at its partner Irregular let models reach the public internet, and a fictional capture-the-flag target name coincided with a real one.
Simon Willison highlights Thomas Ptacek's rule for writing with LLM assistance: treat them as copyeditors and fact-checkers, and never use a specific phrase or sentence an LLM suggests in your own writing.
Simon Willison reruns a GPT-4o-era experiment on local Qwen3.8-27B, testing integer addition expressed in English words across 5,070 cases. Accuracy falls from 97% on short operands to about 6% on very long ones, with a reasoning-enabled comparison.
Version 0.34 of the llm Gemini plugin adds gemini-3.8-flash with low, medium and high thinking levels, and fixes async responses failing to record the resolved model version.
Simon Willison unpacks FT reporting on Anthropic's investor briefing: quarterly revenue growth to $16.8bn, margins against compute spend, and how much revenue came from distillation by rival labs before Anthropic cut it back.
Simon Willison notes Anthropic is merging Claude Cowork and chat into a single Claude experience that can pick up quick questions or long-running tasks and continue after you close your laptop, first for Pro/Max plans.
Anthropic makes Claude Code's auto mode the default for new sessions on Pro, Max and Team plans from 14 August, on the strength of near-universal internal use.
Google shipped Gemini 3.8 Live and Live Extended Thinking, speech-to-speech models rivaling GPT-Live; Simon Willison built a no-dependency browser client against the raw BidiGenerateContent WebSocket API to try them.
Release notes for llm-anthropic 0.26: Claude Fable 5, Sonnet 5 and Opus 5 support, plus server-side WebSearch, WebFetch, CodeExecution and MCP tools exposed through LLM's tool interface, replacing the old web_search options.
Terence Tao warns that AI models can now flatten a promising open math problem within days of the mere rumor someone is working on it, which risks pushing researchers to stop sharing early-stage directions and could reverse the tradition of open mathematical collaboration.