Simon Willison
Independent developer
- 9 articles
- Last published
- Publishes in English
Creator of Datasette and co-creator of Django. Writes about software, open source and large language models.
Latest from Simon Willison
9 items
Redesigning source control at Anthropic
In 2026 Anthropic’s code merge rate exploded from 2,500 to over 30,000 per day, overwhelming Git’s capacity. To cope, a seven‑person team built Scion, a centralized system capable of handling 100 GB history and 25 million daily checkouts. The migration finished in five months. The article links the surge to new model classes and discusses design choices like offline support and adversarial review.
Llm-gemini 0.35
The Gemini 4 Argon model is now available via the Gemini API and a $100/month subscription. Its launch price—$2 per million input tokens and $10 per million output tokens—positions it as half the cost of Claude Opus 5.5 and a fifth of Claude Fable 5.1 and GPT‑6 Astra. A December 1 price increase will bring it to Opus 5.5’s level, yet it will still out‑price GPT‑6 Astra. Benchmark data from Artificial Analysis shows Argon costing $2,407 to run, close to GLM‑5.3 and cheaper than OpenAI, Anthropic, and Meta’s latest models. The article highlights the model’s SVG generation and other creative outputs.
Hello Python 3.15, goodbye 3.10, and now I can use 3.11
Python 3.15, released on 12 October 2026, brings several new language and library features. It introduces explicit lazy imports (PEP 810), unpacking syntax for lists, sets, and dicts (PEP 798), and a new sampling profiler called Tachyon (profiling.sampling). Performance remains close to 3.14, with an experimental JIT giving a 1.2× boost. The release also ends support for Python 3.10 and unlocks Python 3.11 features such as tomllib, TaskGroup, datetime.UTC, and SQLite enhancements. The author demonstrates how to upgrade uv and use the new profiler, highlighting practical benefits for open‑source projects.
Dwarf Fortress uses version control now
After years of avoiding version control, Dwarf Fortress developers have begun using it, according to Tarn Adams. He cited a shift in 2023, coinciding with the Steam release that made the team millionaires. The change reflects a broader trend toward adopting modern development practices in complex projects.
Deno is joining Cloudflare
Cloudflare is acquiring Deno and plans to build on celld, Deno's open-source implementation of the Durable Objects pattern, to make self-hosting workerd a supported way to build and run Workers-style applications. Cloudflare says it will maintain the Deno runtime with monthly bug-fix and security releases for one year, then stop development; Deno will remain open source. Creator Ryan Dahl supports the decision, arguing that Node.js compatibility limited Deno's differentiation and that celld represents a more novel approach to server development. The article also compares Deno and Node.js permissions, noting that Node.js does not yet allow network access to be restricted to specific hosts.
A new feature for my blog, built using my voice
In October 2026, Simon Willison demonstrated that ChatGPT’s Codex voice mode can build a functional Django feature—a newsletters index page—within about half an hour of voice commands while cooking dinner. He guided the model to create a new Django model, migrations, imports from Substack and GitHub, and UI tweaks, then reviewed and finalized the code with minimal typing. The post highlights voice‑driven coding as a powerful multitasking tool, though the author notes it is not a daily driver and prefers typing for detail work.
Quoting Ben Affleck
In his blog post, Simon Willison reflects on his long interest in computers and film, noting how the shift from analog to digital film spurred the adoption of machine learning in visual effects. He describes how convolutional neural networks analyze image tensors—numerical representations of pixels—to detect edges and extract features, enabling efficient green screen removal and replacement. The piece highlights the computational power behind these techniques and their role in contemporary VFX production.
Claude Haiku 5.5
Anthropic released Claude Haiku 5.5, a fast, low‑cost model that matches GPT‑6 Luna’s pricing for prompts up to 100,000 tokens and outperforms it on benchmarks. The new model uses a less generous tokenizer, increasing token counts by about 1.25×, which raises costs for larger prompts. Anthropic also halved cache‑read prices for Sonnet 5.5 and introduced API credits that match subscription costs, easing billing concerns. OpenAI’s Codex subscription remains a better deal for heavy API users. The article presents these changes as a competitive pricing strategy aimed at attracting cost‑sensitive customers.
Quoting Jake Boggan
The author, a former graph theory enthusiast who spent 24 years working on Barnette's Conjecture, learns that the conjecture has been proven in problem 180. He expresses a mix of sadness and reflection, noting that the news evokes emotions similar to hearing a personal loss. The post is a personal reflection rather than a technical analysis.