Effort level prompt appears every session despite configuration

Description

Every time a new Claude Code session starts, a prompt appears asking to select the effort level for Opus 4.6:

Effort in Opus 4.6

Effort lets you control the trade off between response thoroughness and token efficiency for Opus 4.6...

❯ 1. Use high effort (current)  For complex reasoning and difficult agentic tasks.
  2. Use medium effort          For tasks that require a balance of speed, cost, and performance.

There is no way to persist this choice. It asks every single session.

What I've tried

1. Setting CLAUDE_CODE_EFFORT_LEVEL=high in settings.json env block — no effect
2. .claude.json already has "effortCalloutDismissed": true — doesn't prevent the prompt
3. Selecting "high effort" in the prompt — does not persist to next session

Expected behavior

The effort selection should persist across sessions, or there should be a settings.json key (e.g., "effort": "high") to set it permanently.

Environment

• Claude Code version: 2.1.45
• Model: Opus 4.6
• OS: macOS (running via Docker container on Mac Mini M2)
• settings.json has "model": "opus"

Impact

This is a UX friction issue. For users who always want high effort, being asked every session adds unnecessary interaction before they can start working.