Anthropic has cut off xAI’s access to its Claude AI models, according to an email sent this week by xAI cofounder Tony Wu to his staff.
In the email, as first reported by tech journalist Kylie Robison, Wu wrote: “Hi team, I believe many of you have already discovered that Anthropic models are not responding on Cursor. According to Cursor, this is a new policy Anthropic is enforcing for all its major competitors.”
The move followed xAI employees using Claude models through Cursor, a popular AI-powered coding tool, to speed up their development work, according to the Times of India. Wu admitted the decision would hurt productivity in the short term, but said it should push xAI to build its own tools. “We will get a hit on productivity, but it rly (sic) pushes us to develop our own coding product / models. We're at a time in which Al is now a critical technology for our own productivity.”
Anthropic’s action appears to be based on its commercial terms, which ban customers from using it to create competing products or services, including training rival AI models. Although Cursor is a legitimate development platform, xAI’s use of Claude through the tool seems to have triggered Anthropic’s enforcement of these rules.
Nikita Bier, head of X, reacted to the ban saying: “Time to ban Anthropic from X.”
This is not the first time Anthropic has taken action against competitors. In August last year, it withdrew OpenAI’s API access for similar reasons. In June 2025, it also restricted access for the AI-assisted coding platform Windsurf after reports surfaced about a possible sale to OpenAI.
This latest development comes just as Anthropic strengthened technical measures to stop third-party tools from imitating its Claude Code client to access models at cheaper prices than its standard API rates. Thariq Shihipar, who works on Claude Code at Anthropic, said the company had “tightened safeguards against spoofing the Claude Code harness” after some accounts were banned for triggering its abuse detection systems.
In other news, Elon Musk on Sunday announced that X will soon open-source its latest recommendation algorithm. Musk said: “We will make the new X algorithm, including all code used to determine what organic and advertising posts are recommended to users, open source in 7 days. This will be repeated every 4 weeks, with comprehensive developer notes, to help you understand what changed.”
In the email, as first reported by tech journalist Kylie Robison, Wu wrote: “Hi team, I believe many of you have already discovered that Anthropic models are not responding on Cursor. According to Cursor, this is a new policy Anthropic is enforcing for all its major competitors.”
The move followed xAI employees using Claude models through Cursor, a popular AI-powered coding tool, to speed up their development work, according to the Times of India. Wu admitted the decision would hurt productivity in the short term, but said it should push xAI to build its own tools. “We will get a hit on productivity, but it rly (sic) pushes us to develop our own coding product / models. We're at a time in which Al is now a critical technology for our own productivity.”
Anthropic’s action appears to be based on its commercial terms, which ban customers from using it to create competing products or services, including training rival AI models. Although Cursor is a legitimate development platform, xAI’s use of Claude through the tool seems to have triggered Anthropic’s enforcement of these rules.
Nikita Bier, head of X, reacted to the ban saying: “Time to ban Anthropic from X.”
This is not the first time Anthropic has taken action against competitors. In August last year, it withdrew OpenAI’s API access for similar reasons. In June 2025, it also restricted access for the AI-assisted coding platform Windsurf after reports surfaced about a possible sale to OpenAI.
This latest development comes just as Anthropic strengthened technical measures to stop third-party tools from imitating its Claude Code client to access models at cheaper prices than its standard API rates. Thariq Shihipar, who works on Claude Code at Anthropic, said the company had “tightened safeguards against spoofing the Claude Code harness” after some accounts were banned for triggering its abuse detection systems.
In other news, Elon Musk on Sunday announced that X will soon open-source its latest recommendation algorithm. Musk said: “We will make the new X algorithm, including all code used to determine what organic and advertising posts are recommended to users, open source in 7 days. This will be repeated every 4 weeks, with comprehensive developer notes, to help you understand what changed.”