[MODEL] Title: CLI resets to Sonnet on new session despite paying for Opus — no visible warning

Preflight Checklist

• [x] I have searched existing issues for similar behavior reports
• [x] This report does NOT contain sensitive information (API keys, passwords, etc.)

Type of Behavior Issue

Claude modified files I didn't ask it to modify

What You Asked Claude to Do

Description:
When starting a new Claude CLI session, the model silently defaults to Sonnet instead of retaining the previously selected model (Opus 4.6). There is no clear indication of which model is active, making it easy to work for days with the wrong model without realizing it.
Impact:
I worked for 4 days straight using Sonnet without knowing, on a large codebase that exceeds Sonnet's context handling capabilities. This resulted in numerous bugs and regressions that will now take several days to fix. As a paying Pro subscriber specifically using Opus for its larger context window and superior reasoning, this silent downgrade caused significant lost time and productivity.
Expected behavior:

The selected model should persist across sessions, OR
There should be a clear, prominent indicator of the active model at session start
Ideally, allow setting a permanent default model via claude config set --global model

Suggested fix:

Add a persistent model preference in CLI configuration
Display the active model name prominently when starting a new session
Warn the user if the session model differs from their configured preference

Environment: Claude CLI on Debian, Pro subscription

What Claude Actually Did

It run claude sonnet for 4 days.

Expected Behavior

Run Claude Opus 4.6

Files Affected

Permission Mode

Accept Edits was ON (auto-accepting changes)

Can You Reproduce This?

Yes, every time with the same prompt

Steps to Reproduce

_No response_

Claude Model

Sonnet

Relevant Conversation

Impact

Critical - Data loss or corrupted project

Claude Code Version

4.6

Platform

Anthropic API

Additional Context

_No response_