Claude Code Bug: HERMES.md in Commit Messages Triggers Unexpected Extra Usage Billing

Key Takeaways

• Specific Trigger: The case-sensitive string "HERMES.md" in recent git commit history triggers the routing error.
• Billing Mismanagement: API requests are incorrectly routed to "extra usage" billing instead of the user's included Max plan quota.
• Financial Impact: A user reported a silent drain of $200 in extra usage credits despite having significant remaining capacity on their $200/month Max 20x plan.
• Affected Environment: The bug is confirmed in Claude Code v2.1.119 on macOS (Apple Silicon) using claude-opus-4-6[1m] and claude-opus-4-7 models.
• Reproducibility: The issue can be reproduced with a simple git initialization and a commit message containing the specific string.

In-Depth Analysis

The HERMES.md Routing Anomaly

The core of the issue lies in a highly specific and seemingly arbitrary trigger: the presence of the string "HERMES.md" in a repository's git commit history. According to the report filed under Issue #53262 in the anthropics/claude-code repository, this string causes the Claude Code CLI to alter its request routing logic. Under normal circumstances, users on a "Max" plan—specifically the Max 20x plan costing $200 per month—should have their requests deducted from their included plan quota. However, when the string "HERMES.md" is detected in the recent commit history, the system shifts these requests to "extra usage" billing.

This shift is particularly problematic because it occurs silently. In the reported case, the user's Max plan capacity was only at 13% weekly usage, yet the system exhausted $200 in additional credits. The error only becomes visible to the user once the extra usage credits are fully depleted, resulting in an "API Error: 400" stating that the user is out of extra usage. This suggests that the billing logic within Claude Code may be scanning repository metadata or commit messages and incorrectly interpreting the "HERMES" string as a signal to change the billing tier or account routing.

Technical Environment and Reproduction Steps

The bug has been documented on macOS systems running Apple Silicon, specifically using Claude Code version 2.1.119. The user who identified the bug, sasha-id, noted that the issue persists across different versions of the Claude-Opus model, including claude-opus-4-6[1m] and claude-opus-4-7. The specificity of the environment suggests that the bug might be tied to how the macOS version of the Claude Code CLI interacts with git logs or how the Anthropic backend processes requests originating from this specific environment.

A minimal reproduction of the bug was provided, demonstrating that no complex project files are required to trigger the error. By simply creating a new directory, initializing a git repository, and committing any file with the message "add HERMES.md", the subsequent call to Claude Code (e.g., claude -p "say hello") fails with a billing error. This indicates that the CLI is likely performing a git log or similar operation and parsing the output before sending the API request, and the logic for this parsing contains a flaw that misidentifies the "HERMES.md" string.

Industry Impact

Reliability of AI Billing Systems

This incident underscores a significant challenge in the rapidly evolving AI developer tool market: the reliability of automated billing systems. As AI tools become more integrated into developer workflows, they often require access to repository metadata to provide context. If this metadata is used to determine billing routing without robust validation, it can lead to significant financial discrepancies. The fact that a specific string in a commit message can trigger a $200 charge highlights the need for more transparent and fail-safe billing architectures in AI services.

Trust in Developer Tools

For professional developers and enterprises, the "silent" nature of this credit drain is a major concern. Tools that manage their own billing quotas must provide clear feedback when they switch from included plans to paid extras. The failure of Claude Code to respect the Max plan quota while it was still 87% available could damage user trust in the platform's cost-management features. As companies increasingly rely on AI-assisted coding, the accuracy of usage tracking and the prevention of "phantom" charges will become critical benchmarks for tool adoption.

Frequently Asked Questions

Question: What exactly triggers the billing error in Claude Code?

The error is triggered when the case-sensitive string "HERMES.md" appears in the recent git commit history of a repository where Claude Code is being used. This causes the tool to route requests to "extra usage" billing instead of the user's plan quota.

Question: How much did this bug cost the user who reported it?

The user reported that the bug silently consumed $200 in extra usage credits, even though their Max 20x plan had only reached 13% of its weekly capacity.

Question: Which versions of Claude Code and models are affected?

The bug was reported in Claude Code v2.1.119 on macOS (Apple Silicon). It was confirmed to occur when using both the claude-opus-4-6[1m] and claude-opus-4-7 models.