Implements a Future class with combinators (any_of, all_of, try_any_of, try_all_of) for coordinating asynchronous workflow operations. Each future wraps a Fiber that yields, and combinators create new futures that complete when any or all of their children complete. This is a clean, reusable implementation of the promise/future pattern adapted for Ruby's Fiber-based concurrency in a deterministic workflow context.

Provides a Cancellation token with parent-child derivation, callback registration, shielding (to temporarily ignore cancellation), and waiting for cancellation. The token can be cancelled with an optional reason. This is a textbook implementation of the Cancellation Token pattern, fully isolated and reusable for any Ruby application needing cooperative cancellation.

Uses Ruby's TracePoint to intercept method calls on classes like Time, Thread, Mutex, Random, and IO during workflow execution, raising errors if non-deterministic calls are made outside of allowed contexts. It provides an Unsafe escape hatch to bypass checks when needed. This is a clever, self-contained mechanism for enforcing deterministic constraints in a dynamic language, reusable for any Ruby code requiring deterministic replay.

Implements a custom Fiber::Scheduler that provides deterministic concurrency for workflow instances. It handles fiber lifecycle, wait conditions, timers, thread-blocking fiber support, and deadlock detection with timeout. The scheduler uses a priority queue for timers and a condition variable for signaling. This is a sophisticated, self-contained scheduler that could be extracted and adapted for other Ruby applications needing controlled concurrency.