[BUG] Current session" usage shows high % on a fresh session despite ~12h of prior inactivity; confirmed at account level (claude.ai), not just local CLI display

### Preflight Checklist

- [x] I have searched [existing issues](https://github.com/anthropics/claude-code/issues?q=is%3Aissue%20state%3Aopen%20label%3Abug) 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?

Opened a brand-new Claude Code terminal session. The local /usage screen immediately showed:

Current session: 70% used
Resets 2:50pm (Europe/Berlin)

But the same /usage screen's own local session stats for that terminal instance read:

Total cost: $0.0000
Total duration (wall): 8s
Total code changes: 0 lines added, 0 lines removed

So this specific terminal instance had done essentially nothing, yet the session bar was already at 70%.

Last actual Claude usage before opening this session was approximately 12 hours earlier. Since the "current session" is documented as a rolling 5-hour window starting from the first message, a gap of ~12h should mean any prior window had already closed, and a new message should start a fresh window near 0%.

To rule out a purely local/CLI display bug, I checked claude.ai > Settings > Usage independently. It also shows elevated session usage (89% used at time of screenshot, "Resets in 2 hr 15 min"), confirming this is not just a stale/local counter in the CLI, the account-wide usage endpoint agrees.

### What Should Happen?

A fresh 5-hour rolling session window should start near 0% usage when there has been no activity in the preceding 5+ hours.

Actual Behavior
Session shows substantial usage (70%, later 89%) despite the described multi-hour gap in activity.

Environment
- Plan: Max (5x)
- Timezone: Europe/Berlin
- Claude Code (local /usage) and claude.ai web (Settings > Usage) both checked

### Error Messages/Logs

```shell

```

### Steps to Reproduce

1. Use Claude (any surface: claude.ai, Claude Code, etc.) normally, then stop using it entirely.
2. Wait approximately 12 hours with no further usage on any device or surface.
3. Open a brand-new Claude Code terminal session and run any command (e.g. a trivial prompt).
4. Immediately check `/usage` in the CLI.

Expected: Since the "current session" is a rolling 5-hour window starting from the first message, and it's been ~12h since any activity, the new window should start near 0%.

Observed: The CLI /usage screen showed "Current session: 70% used" immediately, despite this terminal instance's own local stats showing:
Total cost: $0.0000
Total duration (wall): 8s
Total code changes: 0 lines added, 0 lines removed

5. To rule out a local/CLI-only display bug, independently checked claude.ai > Settings > Usage on the same account.
Result: also showed elevated session usage (89% used, "Resets in 2 hr 15 min"), confirming the discrepancy exists at the account level, not just in the local CLI display.

### Claude Model

None

### Is this a regression?

Yes, this worked in a previous version

### Last Working Version

_No response_

### Claude Code Version

Current version: 2.1.258

### Platform

Anthropic API

### Operating System

macOS

### Terminal/Shell

Terminal.app (macOS)

### Additional Information

_No response_

Reproduce the report by waiting through the stated inactivity period, opening a new Claude Code terminal, and checking /usage. Compare those results with claude.ai > Settings > Usage to determine whether both surfaces show the same session state. Done means the new rolling session reports near-zero usage after the inactive period, consistently across both surfaces.

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