Anthropic cracks down on unauthorized Claude usage by third-party harnesses and rivals

Anthropic has confirmed the implementation of strict new technical safeguards preventing third-party applications from spoofing its official coding client, Claude Code, in order to access the underlying Claude AI models for more favorably pricing and limits — a move that has disrupted workflows for users of popular open source coding agent OpenCode.

Simultaneously but separately, it has restricted usage of its AI models by rival labs including xAI (through the integrated developer environment Cursor) to train competing systems to Claude Code.

The former action was clarified on Friday by Thariq Shihipar, a Member of Technical Staff at Anthropic working on Claude Code.

Writing on the social network X (formerly Twitter), Shihipar stated that the company had "tightened our safeguards against spoofing the Claude Code harness."

He acknowledged that the rollout had unintended collateral damage, noting that some user accounts were automatically banned for triggering abuse filters—an error the company is ...