Anthropic Billing Bug Overcharges $200, Refunds Denied Initially Before Compensation

According to Motion AI Beating monitoring, Claude Code had a billing bug: as long as the commit history of a Git repository contained the uppercase string `HERMES.md`, all API requests would bypass the Max subscription quota and incur charges for extra usage. A Max 20x user (monthly fee $200) was silently charged $200.98 for extra usage, even though only 13% of their subscription quota was used.

The trigger condition was extremely precise: it had to be the uppercase `HERMES.md`, with case sensitivity and the `.md` suffix. Lowercase `hermes.md` was safe, as well as `HERMES` without the suffix, and `HERMES.txt`. The trigger was not based on the presence of the file on disk; rather, when Claude Code stuffed the git log commit message into a system prompt, the server's abuse prevention system matched that text string. HERMES is the configuration file name of Nous Research's open-source AI agent framework Hermes Agent. Anthropic's abuse prevention system likely detected users attempting to access the API through unofficial clients but mistakenly affected all regular users who mentioned this file name in their commit messages.

The reporter used a binary search to locate the issue after several hours: first cloning the repository to test in an isolated branch, then iteratively narrowing down the commit range, finally pinpointing the triggering string. Another user independently reproduced the issue and wrote an automated detection script. Claude Code's head Boris Cherny confirmed it was an "overzealous abuse prevention system" and fixed it the same day.

However, the refund process went awry. After users submitted refund requests, Anthropic's AI customer service responded, stating they "cannot compensate for downgraded services or billing route technical errors" and outright denied the requests. This response sparked a storm on GitHub and Hacker News, making the front page of HN. The core of the community's anger was not just about the $200: the abuse prevention system should not disguise a misjudgment as "quota exhausted" error, and certainly should not refuse refunds after acknowledging the bug. Claude Code team member Thariq subsequently announced that all affected users would receive full refunds plus equivalent points compensation.