opus[1m] model setting reverts to standard Opus 4.6 after session start on MAC

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?

Description

After updating Claude Code, the opus[1m] model (1M extended context) briefly appears on session start but then silently reverts to standard Opus 4.6 (200k context) within seconds.

Steps to Reproduce

1. Set "model": "opus[1m]" in ~/.claude/settings.json
2. Quit Claude Code completely
3. Restart Claude Code
4. Observe the model indicator — it briefly shows opus[1m] then flips to standard Opus 4.6

Expected Behavior

The model should remain opus[1m] for the entire session, as configured in settings.json.

Actual Behavior

The model shows opus[1m] momentarily on startup, then reverts to standard Opus 4.6 without user action. The settings.json file still correctly contains "model": "opus[1m]". No project-level settings override the model.

Environment

• Claude Code version: 1.1.7714
• Plan: Max
• OS: macOS (Darwin 25.3.0)
• Global settings.json: Contains "model": "opus[1m]" (verified)
• Project settings.local.json: No model key present (verified — only permissions)

Notes

• Using /model to manually reselect opus[1m] after startup works as a workaround
• The issue appeared after a recent update
• Multiple MCP servers are connected — the revert may coincide with MCP server initialization completing

What Should Happen?

The opus[1m] model setting in settings.json should persist for the entire session. The model should not silently revert to standard Opus 4.6 after initialization.

Error Messages/Logs

Steps to Reproduce

1. Set "model": "opus[1m]" in ~/.claude/settings.json
2. Quit Claude Code completely
3. Restart Claude Code
4. Watch the model indicator in the status bar — it briefly shows opus[1m] then reverts to standard Opus 4.6

No project-level settings override the model (verified — only permissions in project settings.local.json).

Claude Model

Opus

Is this a regression?

Yes, this worked in a previous version

Last Working Version

1.1.7714

Claude Code Version

1.1.7714

Platform

Anthropic API

Operating System

macOS

Terminal/Shell

Terminal.app (macOS)

Additional Information

_No response_