[BUG] "model" setting in settings.json not respected on session start — must manually run /model each time

Description

The "model" key in ~/.claude/settings.json is set to "opus[1m]" (Opus 4.6 with 1M context), but new sessions do not consistently start with this model/context configuration. The user has to manually run /model and re-select Opus 4.6 (1M context) at the start of many sessions.

This has happened repeatedly across multiple sessions despite the setting being correctly configured.

Steps to Reproduce

1. Set "model": "opus[1m]" in ~/.claude/settings.json
2. Start a new Claude Code session
3. Observe that the model is not always Opus 4.6 with 1M context
4. Must run /model and manually select it

Expected Behavior

Every new session should start with the model specified in settings.json — in this case, Opus 4.6 with 1M context window. The /model command should never be needed if the setting is configured.

Actual Behavior

Sessions frequently start without the 1M context window despite the setting being present. User must manually run /model to switch.

Relevant config

// ~/.claude/settings.json (line 45)
"model": "opus[1m]"

No project-level settings.json exists that could override this.

Environment

• Claude Code version: 2.1.97
• Platform: macOS (Darwin 25.4.0)
• Shell: zsh
• Model: claude-opus-4-6 with 1M context (when manually selected)