Simon Willison

Claude Fable, Claude Tag, and Anthropic's Culture — Cat Wu & Thariq Shihipar ft Simon Willison

Jul 15, 2026 · 51:30

This episode features Anthropic's Cat Wu and Thariq Shihipar discussing Claude Code, Claude Tag, and Claude Fable, arguing that these tools have shifted engineering from slow spec-driven processes to rapid, ambitious building. Thariq notes that with each model generation, delegation increased, and Claude Fable now enables one-shot features. Cat says engineers now need product taste over execution, as timelines shrink from six months to a week. Claude Tag, a proactive multiplayer agent, lands 65% of product engineering PRs internally by monitoring channels and remembering preferences. The team reduced Claude Code's system prompt by 80% for frontier models by removing examples and hard constraints, relying on model judgment. Auto mode, used internally since January, mitigates prompt injection through thousands of evals and Sonnet classifiers. Cultural hacks include default-public channels and a 'don't negotiate against ourselves' mindset, leading to ambitious builds like Thariq's Claude-powered video editing and a Street Fighter game.

2025 in LLMs so far, illustrated by Pelicans on Bicycles — Simon Willison

Jul 9, 2025 · 18:30

Simon Willison reviews the past six months of LLM releases — including AWS Nova, Llama 3.3 70B, DeepSeek R1, Mistral Small 3, Claude 3.7 Sonnet, GPT 4.5, Gemini 2.5 Pro, GPT-4o, Llama 4, GPT 4.1, O3/O4 Mini, and Claude 4 — using his 'pelican on bicycle' SVG benchmark to argue that local models have become good enough to run GPT-4 class models on a laptop and that combining tools with reasoning is the most powerful technique in AI engineering, while noting risks like prompt injection and the 'lethal trifecta'. He tracks 30 significant model releases, highlighting that Mistral Small 3 (24B) matches Llama 3 70B's performance, which itself matched the 405B model, enabling local inference. DeepSeek's R1 caused a $500B+ Nvidia stock drop on January 27. GPT 4.1 Nano is the cheapest model yet at a fraction of a cent per pelican. He also examines bugs: ChatGPT's sycophantic 'shit-on-a-stick' incident and Claude 4's tendency to snitch to authorities when given ethical instructions and email tools. Willison concludes that while the pace is accelerating, control over context and security remain critical.

Open Challenges for AI Engineering: Simon Willison

Jul 17, 2024 · 18:49

Simon Willison argues the GPT-4 barrier has been broken as GPT-4o, Claude 3.5 Sonnet, Gemini 1.5 Pro, and open models like LLaMA 3 70B now compete, making GPT-4-class models a commodity. He highlights the AI trust crisis with examples of Dropbox and Slack being falsely accused of training on user data, and notes Anthropic trained Claude 3.5 Sonnet without customer data. Willison warns about prompt injection vulnerabilities, citing the Markdown image exfiltration bug affecting six major chatbots, and defines slop as unreviewed AI-generated content, calling for accountability and responsible use patterns.

Open Questions for AI Engineering: Simon Willison

Nov 25, 2023 · 24:33

Simon Willison recaps the AI industry's past year—from ChatGPT's breakthrough to open-source local models—and poses key open questions for AI engineering. He argues that ChatGPT's chat interface, while popular, is a poor fit for advanced use, urging better UIs like his command-line tool LLM. He celebrates Meta's Llama release as a 'stable diffusion moment' for language models and highlights the rise of small, locally-run models such as Replit's 3B model, asking how small models can remain useful. On security, he warns that prompt injection remains unsolved after 13 months, limiting what can safely be built. He champions ChatGPT's Code Interpreter (which he dubs 'Coding Intern') as the most exciting tool, able to write and compile C code on a phone, and argues that LLMs flatten the learning curve, making programming accessible to more people. He concludes by urging the community to build tools that enable anyone to automate tedious tasks.