[BUG] Opus 4.6 (1M context) model variant causes immediate "API Error: Rate limit reached" on Pro plan via /model selector

Bug Description
Selecting "Opus (1M context)" (option 4) from the /model menu in Claude Code immediately returns API Error: Rate limit reached, even with ample quota remaining. Standard Opus 4.6 (option 2) works fine on the same account.

Environment

• Plan: Claude Pro
• Tool: Claude Code CLI (latest)
• OS: WSL/Windows

Steps to Reproduce

1. Open Claude Code terminal
2. Type /model
3. Select option 4: "Opus (1M context) ✓ — Opus 4.6 with 1M context [NEW]"
4. Send any message

Expected Behavior
Request succeeds — 1M context should be available on Pro plan per Anthropic's announcement.

Actual Behavior
Immediately returns: API Error: Rate limit reached

Additional Context
This is a known issue reported by multiple users (#27535, #28975, #30163). The error is misleading — it's not actually a quota/rate issue. The model ID claude-opus-4-6[1m] appears to be broken in the /model selector. Selecting standard "Opus" (option 2) works fine.

DONE WITH CLAUDE