Generating expressions

Expression images ship on transparent PNGs (we green-screen the generation and key it out) so they blend into any host surface. They drive the face is the product value proposition — a static chatbot icon defeats the point of ASMI.

One route, src/app/api/asmi/generate-expression/route.ts, handles three modes:

1. Base mode — text → first frame of an expression.
2. Animation frame mode — take a reference frame + an animationHint ("eyes quarter-closed", "head tilted 5° left") → produce a second frame with that change applied, everything else pixel-perfect identical.
3. Blend (mid-frame) mode — given two frames (base + peak), generate the exact visual midpoint for a smooth interpolation.

Model: gemini-2.5-flash-image (nano-banana). Rate-limited to 10 generations per minute per user. Billing pipeline is tagged generate_expression / generate_expression_frame.