Simon Willison, Datasette creator, interviews Anthropic's Claude Code team
Newer models like Claude Fable require fewer prompt constraints.
I interviewed @trq212 and @_catwu from the Claude Code team at @aiDotEngineer a couple of weeks ago - the video is now out, so I've published an annotated transcript of our conversation https://simonwillison.net/2026/Jul/21/cat-and-thariq/
Combined views
367.2K
10 posts, first seen 34d ago
Reactions
8 postsDF 
Danielle Fong 🔆@DanielleFongI shrunk the system prompt and tool definitions from 40k to 4k minimum tokens and i quite prefer it https://twitter.com/simonw/status/2079553486568800405
- likes: 30
- replies: 6
- bookmarks: 5
- reposts: 1
SW Simon Willison@simonwWe talked about Claude Code, Claude Tag, Fable, coding agent security, evals, tool design, and how Anthropic use these tools themselves Claude Tag (Claude Code via Slack) is already landing 65% of the product engineering PRs for the Claude Code team!
- likes: 26
- replies: 8
- bookmarks: 6
- reposts: 1
SW Simon Willison@simonwI got some really useful Claude prompting tips from @_catwu and @trq212 - it's time to stop overloading our prompts with examples and lists of things not to do, Fable works better without those Claude Code's own system prompt recently shrunk by 80%!
- likes: 1.4K
- replies: 105
- bookmarks: 1K
- reposts: 76
SW Simon Willison@simonwHere's my full write-up of our conversation - or jump straight to 21:24 in the YouTube video here: https://www.youtube.com/watch?v=uU5Gv2h8-9g&t=1284s https://twitter.com/simonw/status/2079551159514411437
- likes: 146
- replies: 7
- bookmarks: 191
- reposts: 4
PY Peter Yang@petergyang- likes: 7
- replies: 1
- bookmarks: 0
- reposts: 1
EM Ethan Mollick@emollickA big thing about Fable (and Sol, though a little bit less) is that you need to be really careful about treating it the way you would a less capable model. Skills that worked well for Opus often make Fable outputs worse, and too many lists of negative instructions can do the…
- likes: 596
- replies: 37
- bookmarks: 213
- reposts: 29