Claude's New System Prompt Bans Song Lyrics and Copyrighted Characters

Anthropic has quietly updated the system prompt for its consumer Claude apps (Claude.ai and mobile), adding strict new rules about song lyrics and copyrighted characters. The changes come days after Sony Music Publishing and Warner Chappell filed lawsuits over training data containing song lyrics.

What changed

As Simon Willison highlights, Anthropic publishes system prompts for its consumer apps on a per-model page—now with an index. The update applies to Fable 5.1 (a model not previously covered on this site). The most significant additions:

• No song lyrics, poems, or book passages — Claude must refuse to reproduce any part of lyrics, poems, or prose, including the last line, a chorus, or a melody written note-by-note. It also declines when a user pastes lines one at a time claiming they are original.
• Date based cutoff — Works first published before 1929 are fine (e.g., Shakespeare sonnets, Keats odes, Puccini librettos). But Claude judges by what it knows, not the user's claim, and declines when unsure.
• No copyrighted characters or logos in generated images — This extends to any visual output: SVG, canvas, CSS, HTML mockups, plotting scripts, ASCII art. Even changing pose, colors, or style does not make it original.

Example from the system prompt

The system prompt includes a concrete example that reads almost like a joke:

<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>

Simon Willison couldn't resist testing it — and confirmed Claude does correctly refuse and offer the axolotl substitute.

Response style tweaks

Beyond copyright restrictions, Anthropic also refined Claude's answering style — the prompt now pushes for more concise, direct responses. No word on whether it now secretly dreams of skateboarding axolotls.

Why it matters

Anthropic publishes these prompts on a docs page that supports Markdown — just append .md to any URL. That makes them easy to diff over time, letting you track behavioral changes. This particular update is a direct legal response, but it also means agentic coding via Claude Code or Cowork won't be affected — those use different system prompts.

If you're building on top of Claude's API, note these rules apply only to the consumer apps — not the API. Still, they give insight into Anthropic's risk posture and may be a preview of what's coming to API model behavior.