[BUG] Claude CLI Subscription Type Modification / Plan Escalation Issue

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?

Path:~/.claude/.credentials.json

Description: An issue was identified where manually changing the subscription tier in the local credentials file grants unauthorized access to higher-tier features (Max plan with Opus 4.8 and 1M token context window) upon restarting the Claude CLI tool.

What Should Happen?

Observed Result: The Claude CLI tool successfully registered the user under the "Max" plan, granting access to Opus 4.8 with a 1M token context window without performing server-side subscription validation.

Steps to Reproduce

Navigate to the Claude configuration directory on a Windows machine: C:\Users\<User>\.claude\

1. Open the .credentials.json file.
2. Locate the subscription_type field (originally set to the $20 Pro plan).
3. Modify the field value from pro to max.
4. Save the file and restart/reopen the Claude CLI tool.

Claude Model

Opus

Claude Code Version

2.1.183

Platform

Anthropic API

Operating System

Windows

Terminal/Shell

PowerShell