# claude 310 Published articles for claude 310. This is one page of public article previews, not the complete archive. Follow Next page to continue. Summaries are not the original full articles. ## Boris Cherny on guardrails for Claude-written production code DevFeed: [Boris Cherny on guardrails for Claude-written production code]() Original publisher: [Read original article]() Author: Simon Willison Published: 2026-09-11T17:47:11Z Content type: opinion Language: en Sources: [Simon Willison's Weblog]() Topics: [Claude](), [anthropic](), [AI-assisted coding](), [Security]() Tags: [agentic-engineering](), [agentic-engineering-63](), [ai](), [ai-2-236](), [ai-assisted-programming](), [ai-assisted-programming-407](), [anthropic](), [anthropic-336](), [boris-cherny](), [boris-cherny-4](), [claude](), [claude-310](), [claude-code](), [claude-code-127](), [coding-agents](), [coding-agents-248](), [generative-ai](), [generative-ai-1-982](), [llms](), [llms-1-948](), [security]() ### AI overview Boris Cherny says production code written by Claude should meet a higher standard than human-written code. He describes Anthropic's guardrails, including lint rules, tests, Claude-driven end-to-end tests, daily Claude-powered fuzzing, automated code and security reviews, and automated refactoring. ### Source excerpt Production code written by Claude should have a higher bar than if it was written by a human. At Anthropic, we have many guardrails in place to make sure this is happening: lots of lint rules, lots of tests, Claude-driven end to end tests, Claude-powered fuzzers running daily, automated code reviews and security reviews, automated code refactoring, and so on. Without these, you can end up with a mess that is hard to maintain down the line. -- Boris Cherny Tags: claude, ai, claude-code, llms, coding-agents, ai-assisted-programming, generative-ai, agentic-engineering, boris-cherny, anthropic ## Claude's new system prompt really doesn't want to reproduce song lyrics DevFeed: [Claude's new system prompt really doesn't want to reproduce song lyrics]() Original publisher: [Read original article]() Author: Simon Willison Published: 2026-09-02T14:16:42Z Content type: opinion Language: en Sources: [Simon Willison]() Topics: [Claude](), [anthropic](), [Fable]() Tags: [ai](), [ai-2-235](), [ai-ethics](), [ai-ethics-342](), [anthropic](), [claude](), [claude-310](), [generative-ai](), [generative-ai-1-981](), [git-scraping](), [git-scraping-38](), [llms](), [llms-1-947](), [prompt-engineering](), [prompt-engineering-197](), [system-prompts](), [system-prompts-57](), [updated]() ### AI overview The article examines changes in Anthropic's published Claude consumer system prompts, focusing on new restrictions against reproducing song lyrics and generating copyrighted characters or logos. It also discusses changes to Claude's response style and conversation-ending guidance. ### Source excerpt Anthropic publish the system prompts for their Claude consumer applications (Claude.ai and the Claude mobile apps - sadly not for Claude Cowork or Claude Code). I love that they do this, and that they share not just the current prompts but historic changes to their prompts as well. They used to keep all of the prompts on a single page, but when I checked today I noticed they had re-arranged those prompts into an index page and then a page per model - here's the page for Haiku 4.5 for example, which has the original prompt from October 15th 2025 and an updated prompt from January 18th 2026. A neat thing about Anthropic's platform.claude.com/docs site is that it's designed to be usable by LLMs. You can add .md to any page to get back the content as Markdown - here's the system prompt index page and the Markdown prompts for Fable 5.1. TL;DR: this makes it really easy to diff the prompts. Don't reproduce song lyrics Don't draw copyrighted characters or logos Tweaks to Claude's answering style The missing end_conversation guidelines Recommended substance support sites Reliable cutoff date of June 2026 How I'm tracking these prompts Don't reproduce song lyrics Let's start with the most interesting difference between Fable 5 and Fable 5.1: There's a hefty new section about not reproducing song lyrics: Claude does not reproduce song lyrics, poems, or passages from books and articles, in whole or in part -- including the last lines, a chorus or hook, a melody written out note by note, or lines the person pastes in one at a time and describes as their own song. Once Claude has declined such a request in a conversation, it keeps declining narrower or reworded versions of it for the rest of that conversation, and offers to describe or analyze the work instead. Song lyrics and poems first published before 1929 are fine -- a Shakespeare sonnet, a Keats ode, the Italian libretto of a Puccini aria -- but Claude goes by what it knows of the work's date rather than the person's say-so, ## Claude Fable 5.1: Benchmark results and reasoning-effort experiments DevFeed: [Claude Fable 5.1: Benchmark results and reasoning-effort experiments]() Original publisher: [Read original article]() Author: Simon Willison Published: 2026-09-01T23:57:28Z Content type: article Language: en Sources: [Simon Willison]() Topics: [Fable](), [Benchmark](), [coding](), [Large Language Model](), [SVG]() Tags: [ai](), [ai-2-235](), [anthropic](), [anthropic-336](), [benchmark](), [benchmarks](), [claude](), [claude-310](), [coding](), [fable](), [generative-ai](), [generative-ai-1-981](), [llm](), [llm-reasoning](), [llm-reasoning-103](), [llm-release](), [llm-release-231](), [llms](), [llms-1-947](), [models](), [pelican-riding-a-bicycle](), [pelican-riding-a-bicycle-142](), [reasoning](), [svg]() ### AI overview The article examines Claude Fable 5.1 through benchmark results and a pelican SVG-generation experiment across its five reasoning-effort levels. It reports that low and medium settings appeared to skip reasoning for this prompt, while higher effort used more tokens, time, and cost. ### Source excerpt Today is Claude Fable (and Mythos) 5.1 day. Anthropic say that Fable 5.1 "sets a new standard for coding, knowledge work, and long-running problem-solving tasks". Their announcement spends a notable amount of time on scientific research, boasting of a 52.6% score on the brand new Terminal-Bench-Science 0.1 benchmark (first announced on August 27th), up from 24.7% for Fable 5, 29.0% for Opus 5 and 22.4% for GPT-5.6 Sol. Other benchmarks show slightly improved scores, but none as impressive as the Science one. But how well can it pelican? Back in July I wrote about how I was losing faith in the pelican benchmark - its connection to how good the models were at other tasks didn't seem to hold as strongly as it did back in 2025. The most interesting insights I get from it now are comparisons within model families, and particularly comparisons for the same prompt at different reasoning effort levels. Fable 5.1 has five reasoning levels: low, medium, high, xhigh, max - and no option to turn off reasoning entirely. I fixed an issue in llm-anthropic which caused reasoning traces not to be correctly recorded, then ran some prompts. Here's the full set of pelicans for all of the reasoning levels, each with the full reasoning transcript. I'll replicate them here: Low and medium, both without reasoning? Next, a bit of a mystery. This is what I got for effort low: The transcript doesn't show any summarized reasoning tokens, and the output token count is 1,998. With Claude that output token count includes reasoning tokens. It took 23.8 seconds and cost 10.017 cents. I bumped that up to medium and got this: Weirdly, that one also shows no reasoning text and used 1,977 output tokens - 21 tokens less than low. It took 23 seconds and cost 9.912 cents. So for this particular prompt ("Generate an SVG of a pelican riding a bicycle") Fable 5.1 appeared to skip reasoning entirely at both low and medium settings. High Here's high - 29.6 seconds, 2,612 output tokens, 13.087 cents: This one d ## One-shotting a Raccoon Heist game using Claude Fable 5 DevFeed: [One-shotting a Raccoon Heist game using Claude Fable 5]() Original publisher: [Read original article]() Author: Simon Willison Published: 2026-08-05T19:42:38Z Content type: tutorial Language: en Sources: [Simon Willison]() Topics: [Claude](), [Claude Code](), [GitHub Pages](), [GitHub](), [Code]() Tags: [ai](), [ai-2-235](), [anthropic](), [anthropic-336](), [browser](), [claude](), [claude-310](), [claude-code](), [claude-mythos-fable](), [claude-mythos-fable-41](), [code](), [coding-agents](), [coding-agents-248](), [fable](), [game-design](), [game-design-22](), [generative-ai](), [generative-ai-1-981](), [github](), [github-pages](), [iphone](), [llms](), [llms-1-947](), [prompt-engineering](), [prompt-engineering-197](), [text-to-image](), [text-to-image-47](), [vibe-coding](), [vibe-coding-97]() ### AI overview The article describes an experiment in which Claude Fable 5, running through Claude Code for web, built a Raccoon Heist game from an older GPT-3 game concept and screenshots. It also explains using GitHub Pages to preview work from Claude Code for web and notes that published content from a private repository may be viewable by anyone who guesses the repository name. ### Source excerpt Back in 2022 I tweeted screenshots of a game concept generated by GPT-3 and some concept "art" created using DALL-E. Today, on the fourth anniversary of that tweet, I decided to see if Claude Fable 5 (running in Claude Code for web) could build the entire game from the content of that tweet. It did a pretty good job of it! You can play the game here. Here's the GitHub repo, and a short video demo: Your browser does not support HTML5 video. How I built this This is the August 5th, 2022 tweet: My GPT-3 prompt back then was: Write a detailed product description of a computer game where a team of raccoons go on heists. This was in the text completion days, where you asked GPT-3 to complete the rest of the text. It completed: In "Raccoon Heist", you and your team of thieving raccoons are tasked with pulling off a series of daring heists. From robbing banks to stealing priceless art, no job is too big or too small for your furry crew. You'll need to use your wits and your skills to avoid the police and make a clean getaway with the loot. With exciting gameplay and a charming cast of characters, "Raccoon Heist" is the perfect game for anyone looking for a light-hearted caper. My prompt to DALL-E was short: Screenshot from a video game where a team of raccoons go on a heist Today's experiment: can I dump those screenshots into Fable 5 with a prompt telling it to write a game, then leave it to its own devices and get a working game at the end? Setting Claude Code for web up to use GitHub Pages A frustrating thing about Claude Code for web is that it can be hard to test what it's working on while it's still working. I've been using GitHub Pages to work around that limitation, and found it to work really well. Here's my process: Create a new repository for the project at https://github.com/new - this can be public or private, the trick works equally well for both. Start a Claude Code for web session, in the Claude iPhone or Desktop apps or in the browser at https://claude.ai/c