[BUG]

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?

Title: [BUG] Opus 4.6 opus[1m] displays "1M context" in banner but 400s on every request — Max 20x

Preflight Checklist

• [x] I have searched existing issues and this hasn't been reported yet
• [x] This is a single bug report
• [x] I am using the latest version of Claude Code

What's Wrong?

Claude Code accepts /model opus[1m], displays Opus 4.6 (1M context) · Claude Max in the welcome banner, then returns HTTP 400 on every request:

API Error: 400 {"type":"error","error":{"type":"invalid_request_error","message":"The long context beta is not yet available for this subscription."},"request_id":"req_011CXtThqJKPF8RrkeSmh6U8"}

The UI should not offer and confirm a model configuration that the server will reject.

Steps to Reproduce

1. Max 20x subscription ($200/month)
2. Claude Code v2.1.34
3. /model opus[1m]
4. Banner confirms: Opus 4.6 (1M context) · Claude Max
5. Send any message → 400 error

Also tested:

• With ANTHROPIC_API_KEY set (Console Tier 1) → same 400
• With Extra Usage enabled + £37.50 balance → same 400
• Fresh session, new tab → same 400
• sonnet[1m] → "Model not found"

Expected Behavior

Either:

• A) Enable 1M context for Max 20x subscribers (it's the headline Opus 4.6 feature and we're the highest individual tier)
• B) Don't allow /model opus[1m] selection on Max subscriptions, or at minimum don't display "1M context" in the banner if the server will reject it

Related Issues

• #15057 — sonnet[1m] regression on Max 20x (same error, same root cause)
• #10219 — sonnet[1m] doesn't work on Max 20x
• #6871 — Long context beta not available for subscription

All three report the same server-side gate. This is now affecting Opus 4.6's flagship feature 2 days after launch.

Environment Info

• Platform: Linux (Ubuntu 24.04)
• Claude Code: v2.1.34
• Subscription: Max 20x
• Model: opus[1m] (claude-opus-4-6[1m])
• Extra Usage: Enabled with active balance
• Node: v22.x

<img width="1920" height="1080" alt="Image" src="https://github.com/user-attachments/assets/8685b114-cf0d-4d47-b78d-fea5b24ba4f0" />

What Should Happen?

Claude should work as normal

Error Messages/Logs

Steps to Reproduce

See original message

Claude Model

Opus

Is this a regression?

Yes, this worked in a previous version

Last Working Version

_No response_

Claude Code Version

4.6

Platform

Anthropic API

Operating System

Ubuntu/Debian Linux

Terminal/Shell

Other

Additional Information

_No response_