[BUG] /usage stats - missing months of usage

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?

I started using claude code every day since April 2026 and I'm missing June and part of September even tho I was very active every day (6-14h a day with claude on multiple project at once).

Important note: I noticed the june issue back in august already so it's not a recent change.

Can provide my account id in private if needed

<img width="709" height="559" alt="Image" src="https://github.com/user-attachments/assets/1022491a-80e4-4457-be5c-8f93657e64de" />

What Should Happen?

Stats correctly showing each month usage

Error Messages/Logs

Steps to Reproduce

1. /usage
2. TAB to Stats

Claude Model

None

Is this a regression?

No, this never worked

Last Working Version

_No response_

Claude Code Version

2.1.295 (Claude Code)

Platform

Anthropic API

Operating System

Windows

Terminal/Shell

IntelliJ IDEA terminal

Additional Information

_No response_