Modal (GPU lane)

Modal is not a general sandbox in Zap: it is the GPU lane target (sandbox.modal plugin plus the lanes.gpu dispatcher).

acquire() accepts purpose: "lane" only — anything else throws MODAL_LANE_ONLY, so a CPU runtime can never mount it by accident.
Capabilities: gpu: true, isolation: "container"; sizes are the GPU classes priced in pricing.json.
Mounting: the lane dispatcher routes to Modal only when Runtime.md lanes includes gpu:<class> or a media step declares gpu. Without a declared lane, Modal never mounts.
Pricing: pricing.json carries the gpu_second SKU per class (USD/s). estimateGpuCost(class, seconds, pricing) is the plan-only estimator.

import { createGpuLaneExecutor } from "@wzrdtech/zap-runtime/lanes/gpu";

const lanes = createGpuLaneExecutor({
  cpu: cpuLaneExecutor,
  lanes: runtimeMd.lanes ?? [], // e.g. ["gpu:L40S"]
  mount: () => modalLaneTarget, // lazy: never called without a gpu lane
});

zap doctor reports first-party (gpu lane only) and verifies that pricing.json classes match the supported GPU classes — drift fails.

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Modal (GPU lane)