[Bug] Regression: Claude Opus context window downgraded from 1M to 200K on Max plan

Bug Description
Regression: 1M context window downgraded to 200K on Max plan
Account UUID: b5528b50-f238-408a-93de-a79cfb421978
Org UUID: 06738b21-4799-4ac6-94b1-c476fb559153
Email: gonzalez.ulises@gmail.com
Plan: max_20x_monthly, hasExtraUsageEnabled: true
Claude Code: v2.1.92, Opus 4.6
GrowthBook flag tengu_hawthorn_window returns 200000 server-side. Previously had 1M working — confirmed by claude-opus-4-6[1m] in lastModelUsage across multiple projects (climalab, dotfiles, clima-dashboard, forma-talent, etc.).
All client-side causes ruled out: no API key override, cache cleared multiple times, re-authenticated, no agent teams, tested multiple directories. Flag consistently returns 200000 from server.

Environment Info

• Platform: darwin
• Terminal: ghostty
• Version: 2.1.92
• Feedback ID: 331d326e-6c3f-4205-a435-be66003144d9

Errors

[{"error":"Error: NON-FATAL: Lock acquisition failed for /Users/ulisesgonzalez/.local/share/claude/versions/2.1.92 (expected in multi-process scenarios)\n    at im_ (/$bunfs/root/src/entrypoints/cli.js:1884:2153)\n    at An6 (/$bunfs/root/src/entrypoints/cli.js:1884:1233)\n    at processTicksAndRejections (native:7:39)","timestamp":"2026-04-06T21:14:25.561Z"}]