[Feature Request] Add opt-in toggle for 1M context in Cowork — Max users lost access after feature flag rollback

Problem

I'm a Max plan subscriber. Previously, my Cowork sessions automatically used claude-opus-4-6[1m] (1M context window), which worked great for long-horizon tasks. After a recent update (around mid-March 2026, Claude Desktop v1.1.7714), all new Cowork sessions now use claude-opus-4-6 (200K context) with no way to switch back.

I verified this by inspecting the session JSON files under:

~/Library/Application Support/Claude/local-agent-mode-sessions/<org>/<project>/local_*.json

• 8 older sessions: "model": "claude-opus-4-6[1m]" ✅
• 26 newer sessions: "model": "claude-opus-4-6" ❌

Root Cause

By examining the Claude Desktop app source (app.asar), I found the 1M context is controlled by a server-side feature flag (3885610113):

function GEe(t) {
  return /\[1m\]/i.test(t) || !Vr("3885610113") || !/sonnet-4-6|opus-4-6/i.test(t)
    ? t
    : `${t}[1m]`
}

When this flag is enabled, Opus/Sonnet 4.6 models automatically get [1m] appended. It appears this flag was rolled back (likely in response to rate limit complaints in #33154), which also removed 1M access for Max users who had no rate limit issues.

Request

1. Add a user-facing toggle in Cowork settings (or claude_desktop_config.json) to opt in/out of 1M context, rather than controlling it entirely via a server-side flag
2. Or at minimum, keep 1M enabled for Max/Team/Enterprise plans as stated in the 1M context GA announcement — these plans should have 1M included at standard pricing

Environment

• OS: macOS (Darwin 25.4.0, Apple Silicon)
• Claude Desktop version: 1.1.7714
• Plan: Max
• Claude Code version bundled: 2.1.78

Related Issues

• #33154 — Cowork forces 1M causing rate limits (opposite problem, but same root cause)
• #31923 — Request to persist model variant settings including extended context
• #34790 — Model selector shows wrong billing label for 1M on Max plan
• #30163 — Opus/Sonnet 1M broken on Pro 20x