7. Model routing

Models are routed by tier (AI-15). Each tier is a setting holding a Claude Code model alias or a full model name; aliases follow new releases without an extension update.

Tier	Setting	Default	Used for
Design	ud.ai.models.design	opus	generating screens (AI-6), from code (AI-7), implement (AI-8), design-system work, review (AI-9)
Assistant	ud.ai.models.assistant	sonnet	chat in the panel, edits of the selection, follow-up turns, variants and auto-layout quick actions
Quick	ud.ai.models.quick	haiku	rename layers, realistic content, translate, descriptions, alt text

The panel picks the tier from the request: a prompt with no selection, or that asks for a new screen, uses Design; a prompt with a selection uses Assistant; quick actions use the tier in §8. The user can override the tier per turn from the model chip in the prompt box. The chosen model is passed as --model and shown in the result line.

With the vscode.lm backend (§10.3), each tier maps to a model selector setting (ud.ai.lm.design|assistant|quick, e.g. {"vendor":"copilot","family":"claude-sonnet-4"}).