Design the object model and core APIs for composing configurable product bundles (kits, combos, build-your-own) from component products, validating a shopper's selection, and computing the bundle's price and availability, for a single catalogue.

Operating context. A bundle is made of slots: fixed components, choose-N-of-M option groups, quantity ranges, and optional add-ons, with cross-option compatibility constraints (choosing A forbids B, requires C). A slot may itself be filled by another bundle, so bundles nest. Building a bundle validates the proposed configuration against its slots and constraints, rolls up the price from the selected components (with a possible bundle-level discount), and derives availability from the components' stock. Configuration reads are heavy and concurrent, while stock is a shared resource behind a port. The whole thing is a single in-process component.

Out of scope. Checkout and payment, the inventory system of record (place it behind a stock port), the 3D/AR configurator UI, and persistence.

What to produce. The class hierarchy (Bundle, Slot/OptionGroup, Component, Constraint, Configuration, the pricer, and the service facade), the public API each exposes, and the flows for validation, price roll-up, and availability roll-up. Be explicit about: how nesting is handled by composition, how a new compatibility constraint is added without editing the validator, and how an invalid configuration is rejected before it can be priced.