Profile a three.js page

After open, perf measures the frame against a budget (desktop by default; site for a 3D website, which also times the first scene frame and counts script and asset megabytes):

• costs: true lists triangles, shadow casters, draw calls and texture megabytes by named group.
• variants measures each change on a fresh page against the baseline, in one call: { label: "no trees", hide: ["trees"] }, a pixelRatio, code run with renderer and scene (shadows off, a material swapped), or a query the page reads at load.
• throttle: 4 slows the page's JavaScript as on a weak laptop.

perf with optimize: true is for a frame perf says is over budget, or a user who asks about performance: it tries the @paprika3d/three-runtime switches, keeps those that help without changing the picture and writes game-runtime.json (../threejs-game/references/optimize.md). A page that opens with no Slow start line and stays within budget needs neither.

If open and perf are not among your tools, the paprika3d MCP server is not installed: it runs as npx -y paprika3d serve (stdio), and https://paprika3d.com/docs/install has each agent's line.