Your ghostwriter just started signing its work in a way that you don’t even see.e

Invisible ink, but for LLMs: Anthropic is embedding machine-readable marks in Claude output, per the EU AI Act transparency code.

Two techniques: A text gets an imperceptible watermark woven into the words, so it survives copy-paste and some editing; while generated files like .png and .svg get signed C2PA provenance metadata.

Models launched from August 2 support it at launch, across the API, Claude Code, Cowork, and Tag, worldwide. Older models are being retrofitted.

Here’s the part people keep getting wrong: The mark exists in text Claude generates, not in everything Claude reads.

Ask it to review a doc and get notes back? Your file stays clean. Ask it to rewrite the doc? That output is marked.

And a hit isn’t a confession. Anthropic says detection only signals content may have been processed by Claude, which covers translating or summarizing someone else’s work.

Absence proves less still. Short passages, heavy paraphrasing, format conversion, and screenshots all break the signal. Just saying.

Everyone else is on the same page: Google already watermarks Gemini text with SynthID, and C2PA metadata is common across OpenAI, Meta, and Microsoft image output. Same code, same deadline.

Meanwhile, OpenAI’s ad product is still finding its feet. A 50,006-prompt study found:

• Ads on 25.94% of commercial prompts, but 14.35% land on an unrelated topic.
• 96.37% of advertisers aren’t cited in the answer sitting above their own ad.
• Only Free and Go users see ads, so your B2B buyer probably doesn’t.
• No licensing deal needed to sit in OpenAI’s index, which stores your title plus roughly 200 characters.

Plus, the company’s partnership with Yelp kicked off with Reservations and Waitlist that now complete bookings inside the chat.

Finally, it seems like smaller budgets are the next target for ChatGPT as six live job postings point to a dedicated SMB ads unit, staffed by poaching from Meta, Google, and TikTok.

Despite current underperformance, it seems like OpenAI is determined to make ads work…