Anthropic cuts off OpenAI's Claude access amidst GPT-5 development controversy

In a dramatic escalation of the competitive landscape in artificial intelligence, Anthropic has revoked OpenAI's API access to its highly-regarded Claude AI models. The move, confirmed by an Anthropic spokesperson, comes amidst allegations that OpenAI engineers were leveraging Claude's coding tools in violation of Anthropic's terms of service, specifically to aid in the development of OpenAI's upcoming GPT-5 model.

According to Anthropic spokesperson Christopher Nulty, "Claude Code has become the go-to choice for coders everywhere, and so it was no surprise to learn OpenAI's own technical staff were also using our coding tools ahead of the launch of GPT-5. Unfortunately, this is a direct violation of our terms of service." Nulty unequivocally stated,

Anthropic's commercial terms of service explicitly prohibit customers from using its services to "build a competing product or service, including to train competing AI models" or to "reverse engineer or duplicate" its offerings.

Sources familiar with the situation indicate that OpenAI was not merely using Claude's public chat interface, but rather integrating Claude directly into its internal development tools via special API access. This allowed OpenAI to conduct extensive evaluations of Claude's capabilities in areas like coding and creative writing, as well as test its responses to safety-related prompts concerning sensitive categories.

The results, it is believed, were then used to benchmark OpenAI's own models and make adjustments for GPT-5.

OpenAI, in a statement through its Chief Communications Officer, Hannah Wong, expressed disappointment, asserting that "it's industry standard to evaluate other AI systems to benchmark progress and improve safety." Wong added, "While we respect Anthropic's decision to cut off our API access, it's disappointing considering our API remains available to them."

This isn't the first instance of Anthropic restricting access to its AI models for competitors. Earlier this year, Anthropic reportedly limited access for AI coding startup Windsurf amidst rumors of its potential acquisition by OpenAI.

The incident underscores the increasingly fierce competition and intellectual property concerns within the rapidly evolving AI sector. As AI models become more sophisticated and valuable, companies are taking more aggressive measures to protect their proprietary technology and maintain their competitive edge.