Simon Willison

Dwarf Fortress uses version control now

The article recounts that Dwarf Fortress, once famously not using version control, has now adopted it. It cites quotes from Tarn Adams spanning 2013 to 2023, showing a shift from resistance to acceptance of version control as the project evolved. The change is noted in the context of the game's Steam release and subsequent success.

Simon Willison
Sep 6

There's No Limit to How Bad Code Can Get

Simon Willison discusses the pitfalls of attempting to replace a legacy system with a new one when technical debt is overwhelming. He explains that while the old system continues to evolve, developers lack incentive to improve it, and the new team, initially fast, eventually struggles to understand and deliver the required functionality. The result is often two partially functional systems in production, with the new one abandoned and the old one still running, increasing risk and complexity.

Simon Willison
Sep 17

Be alert: targeted attacks on prominent Rustaceans

The article warns of a targeted campaign against prominent Rust developers and crate owners, aiming to compromise their devices and accounts to publish malware. Attackers use seemingly legitimate video calls to trick targets into installing malicious software or executing commands, such as a fake audio codec or clipboard command. A recent supply‑chain attack on the array‑ref crate illustrates the threat, and the author suggests using dependency cooldowns as a defensive measure.

Simon Willison
Oct 1

pwasm 0.2a0

Release: pwasm 0.2a0 pwasm is one of my folly projects - an entirely vibe-coded pure Python WebAssembly engine that I built in January during my first bout of AI mania. I hadn't touched it sin...

Simon Willison
Sep 1

Python 3.15.0 candidate 2 is here!

Python 3.15.0 candidate 2 has been released, marking the final release candidate for the upcoming 3.15 release scheduled for October. Hugo van Kemenade, the release manager, notes that only clear bug‑fix changes are allowed between this candidate and the final release, and urges third‑party maintainers to prepare wheels on PyPI and test their projects during this phase. The new RC is not yet available for GitHub Actions, but users can add it to their testing matrix using the allow‑prereleases and check‑latest flags to automatically test against the latest RC and then the stable release.

Simon Willison
Sep 1

Quoting Tarn Adams

Simon Willison writes about a situation where letters were taken from him, prompting a discussion on dwarf behavior rather than dwarf AI. He notes that dwarf AI does not exist, and that dwarves sometimes misbehave. The piece is tagged with AI and game-design, referencing Tarn Adams, co‑creator of Dwarf Fortress.

Simon Willison
Sep 2

Quoting Rick Brewster

Paint.NET has added a fully reverse‑engineered rewrite of Direct2D for use on WINE, implemented in PaintDotNet.Windows.Direct2D1.Managed.dll. The rewrite was created by Claude, a generative‑AI coding agent, and is described as largely "vibe coded" with limited review due to its size. The author notes that Claude required significant oversight to ensure proper resource management and to avoid design flaws.

Simon Willison
Aug 28

Just a rumour of a bug is enough to find a security exploit these days

The article reports that rumors of bugs in open‑source projects now trigger rapid security exploits, with automated agents probing for vulnerabilities within minutes of a patch being discussed. Anil Madhavapeddy demonstrates how modern coding agents can exploit even minimal hints, and rclone maintainer Nick Craig‑Wood notes a dramatic spike in security disclosures and delayed CVE assignments. The post highlights the need for new processes to protect open‑source communities from swift exploitation.

Simon Willison
Oct 13

Redesigning source control at Anthropic

Anthropic redesigned its source control system, creating a custom alternative called Scion to replace Git. The change was driven by a dramatic rise in code changes—from about 2,500 per day in May 2026 to over 30,000 per day by September—requiring a system that could handle a 100 GB main‑branch history and 25 million daily checkouts. Scion was built by a seven‑person team, migrated from Git in five months, and includes a new code‑review system named Antique, while offline support was deemed unnecessary due to Claude’s constant online use.

Simon Willison
Sep 11

Feeling sad about AI

Simon Willison reflects on the emotional impact of AI tools that can produce code quickly, noting that many developers experience an initial sense of disheartenment. He argues that recognizing the shift from coding to higher‑level problem solving allows experienced engineers to leverage new tools and add greater value. Willison emphasizes that software engineering has always faced rapid change, so adapting to AI is part of the profession’s ongoing evolution.

Simon Willison
Aug 25

EVE Online: The Move to Python 3 Begins!

EVE Online is beginning its transition to Python 3, a move that will involve using the futurize script on 2.4 million lines of code and a manual review of about 20,000 differences between Python 2 and Python 3. The company has historically run on Stackless Python since 2003, with the last major upgrade in 2010 to Stackless Python 2.7. While the announcement does not detail how Stackless will be replaced, the team previously showcased a shift away from Stackless in their Carbon engine for EVE Frontier, leveraging the open‑source carbonengine/scheduler library.

Simon Willison
Aug 22

Quoting Linus Torvalds

The article recounts a challenging debug session that was significantly aided by an AI assistant. Despite the AI initially claiming the problem was unsolvable and suggesting a report be written instead, it persisted, adding debug code and analyzing it as the author pushed forward. Ultimately, the author credits the AI with writing the commit message for the fix.