Designing an Organization Model Policy

You administer Claude Code for a 40-person engineering organization on an Enterprise plan. Leadership wants a policy that: (a) prevents anyone from running the most expensive frontier models on routine work, (b) still allows a small number of specifically-approved, complex tasks to use the strongest available model, and (c) ensures that a developer who explicitly picks "Default" in the model picker can't accidentally end up on a restricted model.

1. Design the availableModels configuration (and any companion settings) that satisfies all three requirements. Be specific about which settings you'd use and roughly what they'd contain.
2. A developer on your team runs /model opus and their organization's allowlist permits claude-opus-4-6 but not the newest Opus release. Trace exactly what happens to their request, and what they'll see.
3. Six months later, leadership asks you to loosen the policy so a specific five-person "platform" team (a custom role) can use Fable 5 for their work while the rest of the org stays restricted to Sonnet and Haiku. Explain how you'd implement this without changing the base policy for everyone else.