Statusline model data not updated after /model switch

Description

The statusline command receives stale model data after switching models mid-session with /model. The JSON input to the statusline script continues to report the original session model, not the newly selected one.

Steps to Reproduce

1. Start a Claude Code session (defaults to Sonnet 4.5 in my case)
2. Configure a custom statusline that displays model info:

``json
"statusLine": {
"type": "command",
"command": "jq -r '.model.id'"
}
``

1. Run /model and switch to Opus
2. Send a message to trigger a statusline refresh
3. Observe the statusline still shows the previous model

Expected Behavior

After /model switch, the statusline JSON input should reflect the new model:

{
  "model": {
    "id": "claude-opus-4-6",
    "display_name": "Opus"
  }
}

Actual Behavior

The statusline JSON input still contains the pre-switch model:

{
  "model": {
    "id": "claude-sonnet-4-5-20250929",
    "display_name": "Sonnet 4.5"
  }
}

Confirmed by dumping the raw JSON stdin to a file — Claude Code is sending the stale data, not a statusline script bug.

Environment

• Claude Code v1.0.34
• macOS (Darwin 25.3.0)
• Model switched from Sonnet 4.5 → Opus 4.6 via /model