Elon Musk has fired a warning shot at Anthropic after the AI company blocked his startup xAI from accessing its Claude coding models. The Tesla CEO called the move “not good for their karma” while simultaneously praising Anthropic for doing “something special with coding.“The public rebuke came after Anthropic cut off xAI’s access to Claude through Cursor, a popular AI-powered coding platform that developers use to write software. According to an internal email from xAI cofounder Tony Wu that was viewed by tech journalist Kylie Robison, Anthropic is now enforcing this restriction across all major competitors, not just Musk’s company.“I believe many of you have already discovered that Anthropic models are not responding on Cursor,” Wu wrote to his team on Wednesday. “According to Cursor, this is a new policy Anthropic is enforcing for all its major competitors.”
xAI employees were using Claude internally, Anthropic cites policy violation
The block stems from Anthropic’s terms of service, which explicitly prohibit customers from using its AI models to build competing products or train rival systems. xAI staff had been relying on Claude through Cursor to speed up their development work, but this apparently crossed the line into competitive usage that Anthropic wasn’t willing to tolerate.Wu acknowledged the productivity hit in his message to the team but framed it as motivation. “We will get a hit on productivity, but it really pushes us to develop our own coding product/models,” he wrote. The timing is particularly pointed since Musk recently promised a “major upgrade to Grok Code” coming next month that will “one-shot many complex coding tasks.”Musk’s response on X mixed competitive fire with genuine respect. He admitted that while the upcoming Grok 4.2 might outperform Anthropic’s Claude Opus 4.5 in several areas, coding won’t be one of them—at least not immediately.
Anthropic has history of blocking rivals, Claude Code demand explodes
This isn’t Anthropic’s first move to restrict competitor access. The company previously revoked OpenAI’s API access in August after discovering the ChatGPT maker was using Claude to develop its upcoming GPT-5 model. Anthropic also limited access for coding platform Windsurf last year after acquisition rumors involving OpenAI surfaced.The restrictions come as demand for Claude Code has exploded, with Anthropic recently announcing new rate limits due to unprecedented usage. The company cited cases of users consuming tens of thousands of dollars in model usage on basic subscription plans, with some running Claude Code continuously in the background around the clock.With Claude currently leading multiple coding benchmarks and outperforming xAI’s Grok models in programming tasks, Anthropic seems determined to protect its technical edge—even if it means burning bridges with one of tech’s most prominent figures.
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