/usage command shows 'only available for subscription plans' for authenticated subscriber

Bug Description

/usage command returns "only available for subscription plans" despite being authenticated with a valid subscription via claudeAiOauth.

Environment

• Claude Code version: 2.1.89
• OS: macOS (Darwin 25.4.0, arm64)
• Auth method: claudeAiOauth (confirmed via credentials file)
• Shell: zsh

Steps to Reproduce

1. Authenticate with Claude subscription account (claudeAiOauth)
2. Run /usage command
3. Receive: /usage is only available for subscription plans.

Expected Behavior

Should display usage information for the current billing period.

Additional Context

• /status and /doctor work correctly
• /config shows subscription is active
• Authentication type confirmed as claudeAiOauth (not API key)

Related Issues (all closed)

• #16646
• #16725
• #16655
• #16711
• #11915

These were previously fixed but the issue appears to have regressed.