The numbers are in, and they tell a story that Sam Altman does not want to hear.

Ramp, the finance automation platform used by thousands of US businesses, just published its latest AI spending data. In March, 30.6% of its business customers paid for Anthropic products, up from 24.4% in February. That is a 6.3 percentage point jump in a single month. OpenAI? Flat at roughly 35%. At this pace, Ramp says Anthropic will overtake OpenAI within two months.

This is not a survey. This is real credit card data from real companies making real purchasing decisions. And the trend line is brutal for OpenAI.

Claude Code Changed Everything

The biggest driver is Claude Code. Software engineers and developers have been flocking to Anthropic's coding tools, and that is dragging entire companies along with them. When your engineering team refuses to use anything else, the corporate card follows. Anthropic already leads OpenAI in three specific sectors: information, finance and insurance, and professional services. These are not small niches. These are the industries that spend the most on software.

VC-backed companies are the canary in the coal mine for enterprise adoption. They adopt first, and everyone else follows 6 to 12 months later. Among VC-backed businesses, Anthropic already leads. That is the future arriving early.

The Pentagon Paradox

Ramp did not name a specific cause for the surge, but the timing lines up with one of the most effective marketing campaigns in tech history: one that Anthropic did not plan and did not pay for. When the Pentagon tried to blacklist Anthropic in February, consumers and businesses rallied. Claude briefly topped ChatGPT on the App Store. Microsoft publicly backed Anthropic's legal fight. Being the company that stood up to the Defense Department turned out to be worth more than any Super Bowl ad.

The Financial Times reports the same trend: business adoption of Claude surging while OpenAI's growth has stalled. The FT specifically called out Claude Code as the main catalyst, noting Anthropic's models also lead independent benchmarks from Arena.ai.

What OpenAI Does Next Matters

OpenAI still has more total users, more consumer mindshare, and a ChatGPT brand that most people equate with AI itself. But the enterprise market is where the money is. And in the enterprise market, Anthropic is not just catching up. It is accelerating while OpenAI stands still.

The irony is thick. OpenAI swooped in to take Anthropic's Pentagon contract. But while it was celebrating a government deal, Anthropic was quietly winning the market that actually pays the bills: American businesses with corporate credit cards and engineering teams that know what they want.

Two months. That is how long OpenAI has to figure out a response. The clock started ticking in March.

Sources: Ramp AI Spending Index via Business Insider, Financial Times. Ramp data reflects spending by its customer base and may not represent the full market.