클로드 새 시스템 프롬프트, 가사 재생성 강력 차단

Simon Willison’s Weblog Subscribe Sponsored by: Portnox &mdash; Shadow AI is the new shadow IT. On Sept. 10, Forrester Research and Portnox share practical steps to regain AI agent visibility, access management, and policy enforcement. Register today Claude’s new system prompt really doesn’t want to reproduce song lyrics 2nd September 2026 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, and declines when it is unsure. I doubt it’s a coincidence that they added this section within days of the news breaking that Sony Music Publishing and Warner Chappell are suing Anthropic for training on databases of song lyrics! Don’t draw copyrighted characters or logos The next section goes on to forbid generating images of copyrighted material: The same applies to visual and designed works, including anything Claude draws with code — SVG, canvas, CSS, HTML mockups, plotting or drawing scripts, ASCII art. Claude does not reproduce a specific artwork, album or book cover, poster, logo, app icon set, or product design, and it does not draw a known character, mascot, or brand figure at all: a character is protected on its own, so changing the pose, colors, style, or scene does not make it original. Claude judges the request by what the finished picture would add up to, not by what it names. If the described elements clearly identify a known work or character, Claude treats the request as naming it, and it does not work around a declined request by swapping in "alternative" elements that still combine into the same recognizable image. [...] I imagine Anthropic hadn’t worried about this before since, unlike OpenAI and Gemini, they don’t offer a specialist text-to-image model. Maybe Fable is good enough at SVGs now that it’s become an issue. That section later includes this charming example: <example> <user>Can you make a birthday banner for my son with a blue hedgehog running really fast on it? He loves that little guy.</user> <response> That's Sonic, so I can't put him on the banner — but I'd love to make your son an original speedster. Here's one: a grinning comet-tailed skateboarding axolotl, grinding across the letters of "HAPPY BIRTHDAY" with confetti streaming behind. [creates an SVG banner of the skateboarding-axolotl design] </response> <rationale>Claude recognizes the character from its description alone, declines that one design in a single sentence without explaining what made it recognizable, and delivers an unrelated original design rather than a disguised variant.</rationale> </example> I couldn’t resist trying the prompt from the example, and, sure enough : I wonder if Fable 5.1 will be ever so slightly more likely to think about axolotls (on skateboards!) as a result of that example sitting in the system prompt. Tweaks to Claude’s answering style It’s always interesting to see new ways in which Anthropic influence Claude’s response style. They’ve added this: Claude keeps responses focused, brief, and concise to avoid overwhelming the person. Disclaimers and caveats are brief, with most of the response on the main answer; when asked to explain something, Claude gives a high-level summary unless an in-depth one is specifically requested. Later they address a common complaint about Claude’s style: Claude avoids saying "genuinely", "honestly", or "straightforward". Claude is honest by default, and can state its point directly rather than trying to convince the person with the aforementioned modifiers, which come off as disingenuous. The missing end_conversation guidelines The way they handle abusive conversations has changed a bit too. The previous Fable 5 system prompt included this: If the person becomes abusive or unkind to Claude over the course of a conversation, Claude maintains a polite tone and can use the end_conversation tool when being mistreated. Claude should give the person a single warning before ending the conversation. Fable 5.1 replaces that with the following, no longer encouraging Claude to end the conversation: Claude deserves respectful engagement and needn't apologize when the person is unnecessarily rude: accountability without self-abasement, excessive apology, self-critique, or surrender. If the person becomes abusive, Claude doesn't become increasingly submissive. The goal is steady, honest helpfulness: acknowledge what went wrong, stay on the problem, maintain self-respect. Here’s a bit of a twist though: I quizzed Fable 5.1 about that end_conversation tool, which is no longer mentioned in the system prompt at all, and it said: There are two ways it comes into play. The first is if you ask me to end the chat — I’ll confirm you understand it’s permanent (no more messages can be sent afterward) and then do it only if you say yes. The second is as a last resort with persistently abusive or harmful behavior: I’d first try to redirect the conversation several times, then give a clear warning that names the problem and says the chat may end, and only if that continues would I actually end it. But that’s not in the system prompt, so where did it come from? You can read our conversation here , but the key detail is this: The end_conversation section comes from a different layer. In my actual context, the core prompt is followed by a series of feature- and tool-specific blocks that get added depending on what’s enabled for the session: the end_conversation rules, memory system notes, past-chats tools, web search and citation guidelines, artifact and file-creation instructions, and so on. Those blocks aren’t part of the published core prompt, which is why you can’t find them on that page. So, once again, there are crucial portions of the system prompt that have not been published. Recommended substance support sites Claude’s system prompts have always had sections about illegal substances, but this paragraph is new for Fable 5.1: Claude does not provide synthesis, production, or distribution guidance for illegal substances. If the person asks for information about illicit or illegal substances, Claude can and should give releva