Reddit sued the Artificial Intelligence (AI) startup Anthropic on Wednesday, accusing it of stealing data from the social media discussion website to train its AI models despite publicly assuring it wouldn't.

The complaint filed in San Francisco Superior Court is the latest battle over AI companies' alleged unauthorised use of third-party content. Anthropic's backers include Amazon.com and Google parent Alphabet.

"We disagree with Reddit's claims and will defend ourselves vigorously," an Anthropic spokesperson said.

According to the complaint, Anthropic has resisted entering a licensing agreement even as it trained its Claude chatbot on Reddit content, despite assuring last July it had blocked its bots from accessing Reddit's platform.

Reddit quoted Claude admitting it was "trained on at least some Reddit data" and did not know if that content was deleted.

It also said Anthropic's bots have accessed or tried to access Reddit content more than 100,000 times, undermining the company's allegedly styling itself as an AI "white knight" committed to trust and honesty.

"Anthropic refuses to respect Reddit's guardrails and enter into a license agreement," unlike Google and OpenAI, the complaint said.

By scraping content and using it for commercial purposes, Anthropic violated Reddit's user policy and "enriched itself to the tune of tens of billions of dollars," the complaint added.

In a statement, Reddit Chief Legal Officer Ben Lee said "we believe in an open internet," but AI companies need "clear limitations" on how they use content they scrape.

Reddit and Anthropic are based in San Francisco, about a 10-minute walk from each other.

The lawsuit seeks unspecified restitution and punitive damages, and an injunction prohibiting Anthropic from using Reddit content for commercial purposes.

Anthropic introduced its newest Claude models, Opus 4 and Sonnet 4, on May 22. Overall annualized revenue has reached $3 billion (roughly Rs. 25,732 crore), two people familiar with the matter said last week.

The case is Reddit Inc v Anthropic PBC, California Superior Court, San Francisco County, No. CGC-25-524892.

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