Project: The portable, versioned workspace containing model definitions, assets, scenarios, experiments, and references to results.Canonical Model: BeforeMetal's backend-independent, unit-aware, frame-aware representation of robot and world definitions.Asset: An immutable or revisioned source or derived artifact such as a mesh, texture, controller, dataset, or imported model file.Robot: A modeled physical system composed of bodies, joints, materials, devices, sensors, and controller interfaces.World: The spatial setting containing terrain, objects, fields, atmosphere, weather, and global conventions.Scenario: A reusable pairing of robot, world, initial state, mission, and supported disturbances; it does not select a sweep or create results.Experiment: A versioned plan that selects a scenario, parameters or distributions, controllers, fidelity, seeds, metrics, stop conditions, and execution policy.Compiled Scenario: The immutable, capability-checked execution description produced from an experiment before a run.World Instance: One live mutable execution state created from a compiled scenario.Run: One attempted execution of one compiled scenario with one realized parameter set and seed, whether completed, failed, or cancelled.Batch: A finite set of runs generated by a sweep, repetitions, sampling plan, or explicit run list.Entity: A stable-identity object in the canonical model or committed simulation state.Component: Typed state and behavior attached to or referenced by an entity.Port: A typed, directed connection point with declared units, frame, timing, causality, and cardinality where applicable.Model: A declared mathematical or behavioral approximation with parameters, assumptions, validity limits, and evidence.Solver: An algorithm that advances or resolves the state of a model.Backend: A replaceable implementation of a BeforeMetal subsystem contract, such as a mechanics solver implementation.Adapter: A boundary that maps an external format, protocol, process, device, or solver to canonical BeforeMetal contracts.Sidecar: An adapter or external tool executed in a separately supervised operating-system process.Extension: User- or third-party-supplied behavior attached only through a declared Extension Host capability.Capability: A stable, machine-readable statement of supported behavior, limits, fidelity, and required resources.Fidelity Profile: A named selection of models, solver settings, approximations, and evidence expectations.Fidelity Card: The pre-run or completed-run record of the fidelity actually requested and used, including limitations and out-of-envelope conditions.Calibration: Estimation of model parameters using designated observations.Validation: Comparison of predictions with independent evidence for named observables and operating conditions; the evidence source class is explicit, and physical evidence is optional.Verification: Evidence that equations, algorithms, schemas, and implementations behave as specified.Metric: A versioned, unit-bearing calculation over run state, events, or results.Trace: Timestamped recorded state, signal, event, or diagnostic data from a run.Checkpoint: A restorable state artifact whose completeness and compatibility are explicitly declared.Input Re-execution: A new execution driven by recorded causal inputs and compared with the original under a declared criterion.Checkpoint Resume: Continued execution from a compatible checkpoint after all stateful participants restore their declared state.Recorded-State Playback: Visualization or analysis of stored states without rerunning any solver.Portable product: The default installation and workflow that remains useful without optional engineering integrations.Pure-Rust default: First-party runtime logic and mandatory simulation dependencies are Rust; ordinary operating-system APIs and drivers are not reimplemented, and foreign engineering runtimes are not required.