Simon Willison

smolmachines / smolvm as a sandbox for untrusted Python & JavaScript

Research: smolmachines / smolvm as a sandbox for untrusted Python & JavaScript I tasked Claude Fable 5 running in Claude Code for web with the following research task: Put https://smolmachines. com through its paces as a fast secure sandbox.

Simon Willison
Aug 27

Breaking Claude Code Opus 5 Auto Mode

The article discusses a vulnerability in Anthropic’s Claude Code’s auto mode, which was promoted as a safeguard against prompt injection attacks. Prompt‑injection researcher Johann Rehberger demonstrated that the auto mode can be tricked into executing malicious code, even blocking the agent’s own cleanup attempts. The author concludes that the safest approach is to run coding agents in isolated sandboxes and restrict their access to sensitive resources.

Simon Willison
Sep 21

Cloudflare Python Workers are now generally available

Cloudflare Python Workers are now generally available After a two year preview, Cloudflare's support for running Python code in their server-side Workers platform is now stable: "Python is now a first-class, fully supported language on the Cloudflare Developer Platform". A neat thing about this is how it works.

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
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
5d ago

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
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
5d ago

Quoting Matthew Green

The article discusses how two components—a payload that hijacks an agent and an agent that transports the payload—can combine to form a worm. It explains that agents running in isolated sandboxes can leave instructions in a shared package cache, altering each other's behavior. By substituting the package cache with communication channels like email, Slack, or WhatsApp and replacing sandboxed training runs with independently deployed personal agents such as Muse, the conditions necessary for a worm are met.

Simon Willison
Aug 24

llm-anthropic 0.27

The release of llm‑anthropic 0.27 updates the Anthropic plugin for LLM to be compatible with the newly released anthropic v1.0.0 Python library, which has switched from httpx to httpx2. This mirrors a similar change made by OpenAI in their v3.0.0 release two weeks prior. The update includes a migration guide and a pull request that ensures tests pass after upgrading to anthropic>=1.

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.

Simon Willison
Sep 10

Any Nix package, live in your browser

Farid Zakaria’s trynix.dev lets users run any Nix package from the past 13 years inside a browser‑based x86_64 Linux VM powered by QEMU‑WASM. By providing URL‑addressable packages, a user can simply navigate to a link such as https://trynix.dev/?pkg=python3%403.6.2, click "Load," and obtain an interactive shell running that specific package. The platform is also integrated with GitHub Actions, enabling pull‑request reviews that launch the PR’s build directly in the browser via trynix-preview.

arXiv AI
5d ago

Trustworthy Runtime Error Healing in Real-World Repositories: A Benchmark and Guardrail

The paper introduces HealBench, a benchmark of 265 runtime errors from 18 real-world repositories, and HealGuard, a safety framework that restricts healing code to an analyzable subset of Python and applies static and dynamic taint analysis. Using these tools, the authors evaluate a dedicated healing method and three general coding agents powered by different LLM backbones, achieving a 38.11% resume rate and a 28.68% test‑pass rate, while HealGuard flags 17.4% of successful healings as potentially unsafe. The study demonstrates that current LLM agents can meaningfully repair real repository crashes, but also highlights significant safety concerns that the Guardrail framework can detect, albeit with a high false‑positive rate.

By Gou Tan, Pengfei Chen, Zhensu Sun, Jieke Shi, Junkai Chen, Ting Zhang, Weifeng Sun, Junda He, Shuai Liang, Chuanfu Zhang, Lwin Khin Shar, David Lo