Anthropic has cut off OpenAI’s access to its Claude API. The move came after Anthropic discovered that OpenAI had violated its terms by accessing Anthropic’s tools using prohibited methods.
“Claude Code has become the go-to choice for coders everywhere, and so it was no surprise to learn OpenAI’s 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,” Christopher Nulty, an Anthropic spokesperson, said in a statement.
Under its commercial terms, Anthropic specifically states that customers may not develop another product or service, create their AI models using Anthropic’s platform, or attempt to dissect or copy its technology. This adjustment to Claude’s availability coincides with OpenAI’s internal preparations for GPT-5, the forthcoming model touted for enhanced coding capabilities.
Anthropic announces weekly usage cap on Claude codes
According to insiders, OpenAI integrated Claude into its proprietary toolchain via custom APIs rather than the usual chat portal. This arrangement enabled OpenAI to assess Claude’s performance on programming and writing tasks, and to evaluate its responses to safety-related queries regarding areas such as CSAM, self-harm, and defamatory content. The findings were then used to measure Claude against the in-house models of OpenAI and to tune OpenAI’s system accordingly.
Responding to the development, Hannah Wong, chief communications officer at OpenAI, said, “It’s industry standard to evaluate other AI systems to benchmark progress and improve safety. While we respect Anthropic’s decision to cut off our API access, it’s disappointing considering our API remains available to them.”
Nulty also added that granting API access for purposes like benchmarking and safety reviews is still important for the industry. The company is yet to clarify how the current restrictions on Claude might affect its ongoing evaluation. API restrictions have long been wielded as leverage in the tech sector. For instance, Facebook previously cut off Vine (owned by Twitter), and more recently, Salesforce imposed constraints on rival Slack integrations.
Anthropic recently revealed plans to introduce weekly caps on Claude Code to reduce continuous background consumption by users. The company said in an email and on X that the new limits will start on August 28. These restrictions will affect users on the $20 Pro tier as well as those on the $100 and $200 Max tiers. Existing five-hourly usage quotas will remain unchanged.
In addition, the update is expected to include two separate weekly quotas: a general usage cap and a model-specific allowance for Claude Opus 4. Max-tier subscribers will have the option to purchase additional capacity at Anthropic’s standard API pricing once they exceed the weekly thresholds. This adjustment builds on a subdued deployment of usage ceilings for Claude Code implemented earlier this summer.
