AI · Anthropic · April 25, 2026
$200 — a string in a git commit silently routed Claude Code billing to extra usage
Vendor
Anthropic
Service
Claude Code plan billing
Amount
$200 (reported)
Timeframe
Silent, until $200 drained
Cause
Billing-routing bug
Outcome
Fixed by vendor
Documented in a public GitHub issue with a minimal reproduction. GitHub: anthropics/claude-code #53262 (by sasha-id)
What happened
A Claude Code user on the Max 20x plan started hitting '400: out of extra usage' errors, even though the plan dashboard showed 86% of weekly capacity still available. Requests that should have drawn from the included plan quota were instead billed to extra usage, and that pool quietly drained to $200.98 before the errors made the problem obvious. Several projects became unusable once extra usage hit zero, while the plan itself sat largely untouched.
Root cause
Claude Code includes recent git commit messages in the system prompt it sends with each request. When a recent commit message contained the case-sensitive string 'HERMES.md', something server-side routed that request to extra-usage billing instead of the plan quota. The trigger was the string in the commit history, not a file on disk. 'hermes.md' in lowercase, 'HERMES' without the extension, 'README.md', and 'AGENTS.md' all billed normally. The user isolated it by binary-searching individual commit strings until 'HERMES.md' stood out as the exact trigger.
How to avoid it
•
Watch the pay-as-you-go pool, not just the plan dashboard. Plan quota and extra usage are separate pools, and only one can silently hit zero.
•
Alert on any spend that lands in extra usage. A shift off plan quota is the real anomaly, and a plan-capacity dashboard will never show it.
•
Treat a vague billing error as a clue, not a verdict. Isolating the variable, here by testing commit strings, is what surfaced the real cause.
CostGoat watches your Anthropic bills, so a surprise like this reaches you as an alert, not an invoice.
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