[BUG] No auto-fallback or clear error when Opus 4 limit reached - shows generic "usage limit" error

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?

When the Opus 4 model usage limit is reached, Claude Code shows a generic "usage limit reached, resets at 7am UTC"
error. However:

1. The limit is model-specific (Opus 4), not account-wide
2. Switching to Sonnet manually works fine
3. No auto-fallback to available models
4. Error message doesn't indicate it's a model-specific limit

This is confusing because other models are still available, but the error suggests the entire account is blocked.

What Should Happen?

When a specific model's limit is reached:

• Auto-fallback to next available model (Opus 4 → Sonnet), OR
• Clear error message: "Opus 4 limit reached. Switch to Sonnet or wait until 7am UTC reset"
• Allow users to continue with available models

Error Messages/Logs

Claude usage limit reached. Your limit will reset at 7am (UTC).
 • /upgrade to increase your usage limit.

Steps to Reproduce

1. Use Claude Code with default model settings (Opus 4)
2. Continue using until Opus 4 usage limit is reached
3. Observe the error message shown:

Claude usage limit reached. Your limit will reset at 7am (UTC).
• /upgrade to increase your usage limit.

1. Wait past the 7am UTC reset time
2. Try any command - error persists
3. Manually switch model to Sonnet using /model command
4. Claude Code works immediately

Expected: Should auto-fallback to Sonnet or show clear error about Opus 4 specifically

Actual: Shows generic "usage limit" error that doesn't mention it's model-specific, and doesn't auto-fallback
to available models (Sonnet)

Additional Context:

• Same account on local machine still works fine (hasn't hit Opus 4 limit yet)
• Manually switching to Sonnet on remote server resolves the issue immediately
• Error message is misleading - suggests entire account is blocked when only one model is limited

This makes it clear that:

• It's a model-specific quota issue
• The error message is confusing/unhelpful
• Auto-fallback doesn't work
• Manual workaround exists but isn't obvious

Claude Model

Sonnet (default)

Is this a regression?

I don't know

Last Working Version

_No response_

Claude Code Version

1.0.35 (Claude Code)

Platform

Anthropic API

Operating System

macOS

Terminal/Shell

Terminal.app (macOS)

Additional Information

<img width="583" height="134" alt="Image" src="https://github.com/user-attachments/assets/e1bd2cad-96d1-476d-94ed-e0e57fad1278" />