[BUG] Spurious Usage Spikes and 100% Weekly Limit Lockout After Plan Upgrade

Preflight Checklist

• [x] I have searched existing issues and this hasn't been reported yet
• [x] This is a single bug report (please file separate reports for different bugs)
• [x] I am using the latest version of Claude Code

What's Wrong?

We experienced a critical bug with the usage calculation system that resulted in a complete account lockout. Session limits spiked unexpectedly without underlying activity, and subsequent upgrading of our plan caused our weekly limit to falsely jump to 100%.

Actual Behavior:
The system falsely flagged weekly usage at 100% immediately after the upgrade, blocking all access to the service until March 26th.

Impact: Critical / Blocker. This completely halted production and caused us to miss an urgent sprint delivery.

What Should Happen?

Session usage should accurately reflect active queries. Upgrading a plan should either proportionally adjust the weekly usage against the new, higher limits or maintain the previous true usage (20%). It should not trigger an artificial 100% cap.

Error Messages/Logs

Current session
                                                     0% used

  Current week (all models)
  ██████████████████████████████████████████████████ 100% used
  Resets Mar 26, 11pm (America/New_York)

  Current week (Sonnet only)
  ██████████████████████████████████████             76% used
  Resets Mar 26, 11pm (America/New_York)

  Extra usage
  Extra usage not enabled • /extra-usage to enable

Steps to Reproduce

Operate on the "Max 5x" plan.

Usage was stable at ~70% Session and 20% Weekly around 15:00 UTC.

Session usage suddenly spiked to 100% despite low active session volume.

Upgraded the account to the "Max 20x" plan to unblock usage.

Upon upgrading, Session usage correctly reset to 0%, but Weekly usage erroneously jumped from 20% to 100%.

Claude Model

None

Is this a regression?

I don't know

Last Working Version

2.1.73

Claude Code Version

2.1.76

Platform

Anthropic API

Operating System

Ubuntu/Debian Linux

Terminal/Shell

WSL (Windows Subsystem for Linux)

Additional Information

high financial impact, workflow blockage, loss of contract.