[BUG] /effort auto setting is lost when switching models — silently reset to a fixed level (Fable 5 → low)

Summary

A saved /effort auto setting does not survive a /model switch. After changing models, running /effort with no args reports that the effort level was reset to a fixed level ("low") and saved as the new default — without the user asking for it.

Steps to reproduce

1. /model → select Opus 4.8 (1M context)
2. /effort auto → confirms "Effort level set to auto"
3. /model → select Fable 5
4. /effort (no args)

Actual behavior

Step 4 outputs:

Set effort level to low (saved as your default for new sessions): Quick, straightforward implementation with minimal overhead

So the model switch discarded the auto setting and a bare /effort (which should just display the current level) instead set and persisted "low" as the default.

Expected behavior

• /effort auto should persist across model switches (or at minimum, the reset should be surfaced at switch time, not silently).
• /effort with no arguments should report the current level, not mutate and save a new default.

Environment

• Platform: macOS (Darwin 24.6.0), zsh
• Models involved: claude-opus-4-8 (1M) → claude-fable-5[1m]

Related

• #60200 (/effort auto resolves to a static default rather than being adaptive)
• #50328 / #53716 (earlier /effort arg-handling bugs)