[BUG] [1M] "Long context beta is not yet available for this subscription" error on Max plan ($200/mo)

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 Claude Code attempts to use the extended context window, the API returns:

API Error: 400 {"type":"error","error":{"type":"invalid_request_error","message":"The long context beta is not yet available for this subbscription."},"request_id":"req_011CXqcQZGUZMEZKxosRVajr"}

This affects both Opus and Sonnet models — not just Opus as previously reported.

Expected Behavior

Max plan subscribers ($200/mo) should have access to the long context beta, as advertised.

Context

This has been a recurring request for ~4 months (see #8381). Paying $200/month and not having access to a feature that's available via the API with the right beta header feels like an oversight that should be prioritized.

Real-World Impact

I regularly work with codebases exceeding 1M LOC, re-engineering efforts of 100K+ LOC, and scientific project contexts that routinely surpass 100K tokens. These are exactly the workflows that justify a Max subscription — and exactly the workflows that are currently broken without long context support.
This has been requested for ~4 months now (see #8381, #23714, #15057, #23700). For $200/month, this shouldn't still be an open gap.

Environment

• Plan: Max ($200/mo)
• Models affected: Claude Sonnet 4.5, Claude Opus 4.6

What Should Happen?

Max plan subscribers ($200/mo) should have full access to the long context beta (1M tokens) for all supported models (Sonnet 4.5, Opus) without requiring manual beta header configuration. The feature should work out of the box in Claude Code.

Error Messages/Logs

Steps to Reproduce

/model opus[1m]

Claude Model

Opus

Is this a regression?

No, this never worked

Last Working Version

_No response_

Claude Code Version

2.1.34

Platform

Other

Operating System

Windows

Terminal/Shell

PowerShell

Additional Information

_No response_