ActualLab.Fusion in Brief

ActualLab.Fusion is an end-to-end reactivity framework for .NET and TypeScript applications. It combines automatic caching, dependency tracking, precise invalidation, RPC, and reactive client state so an application can propagate changes from its database and backend services to every affected UI without hand-written subscription protocols.

The Mental Model

A Fusion compute service exposes intercepted methods marked with [ComputeMethod]. A unique service-method-argument call produces a cached, immutable Computed<T>. While computing, Fusion records every other computed value it reads and forms a dependency graph automatically. Calling the same input reuses its current consistent result.

When application data changes, command handlers enter invalidation mode and call the affected compute methods with the same arguments. Fusion marks those computed values invalid and immediately propagates invalidation to their live dependants. Values are normally recomputed lazily when requested again, so only data that is both affected and still in use consumes work.

ComputedState<T> and Fusion's UI components turn invalidation into reactive updates. Fusion RPC carries compute calls, results, and invalidation messages across process and network boundaries, extending the same dependency graph to Blazor, MAUI, browser, and TypeScript clients. The Operations Framework can record completed commands transactionally and replay their invalidation phase on every backend host.

What Is Available

• Compute services and computed values — caching, dependency graphs, invalidation, consistency, update delays, and memory management.
• Reactive state and UI — mutable and computed states, snapshots, Blazor components, loading, and error handling.
• ActualLab.Rpc — reconnectable RPC, routing, streaming, serialization, peer references, and remote compute services.
• CommandR and Operations Framework — command pipelines, transactional operation logs, distributed invalidation, events, and transient-error reprocessing.
• Authentication and Entity Framework integration — session-aware computed APIs, database hubs, batching, sharding, and operation scopes.
• ActualLab.Core and serialization — reusable concurrency, caching, collections, identifiers, results, workers, and serializer abstractions.
• TypeScript packages — ports of the core, Fusion, RPC, Fusion RPC, and React integration layers.
• API and terminology references — the full public-type index and Fusion glossary.

Use search when you need candidate documentation anchors, get for the text at a known anchor (small sections are returned in full including their sub-sections; large ones return the immediate text plus links to their sub-headings), and search_expanded when you need complete matched sections including their nested subsections.