Hosting

A thin Microsoft.Extensions.DependencyInjection integration seam: extension methods that register the engine's top-level singletons (resource registry, allocator, epoch manager, timer, watchdog, paged MMF, database engine) and bind their option types via IOptions<T>, giving an application a single canonical chain to bootstrap a working DatabaseEngine. Singleton/Scoped/Transient twins let test and tooling hosts scope an engine instance per DI scope, an injectable IWalFileIO seam swaps the WAL's disk backend for an in-memory one, and small conveniences (AddTyphonProfiler, EnsureFileDeleted) round out startup/teardown for tests and tooling.

🔬 Recommended: Hosting doesn't have its own in-depth-overview chapter — read in-depth-overview/01-foundation.md §9 (Chapter 01: Foundation, alongside the primitives it wires up) first to understand the overall design and concepts behind this category, before diving into the specific features below.

Public Features

Feature	Summary	Status	Level
DI Engine Bootstrap Chain	Add*() extension methods on IServiceCollection that register and wire the engine's top-level singletons into a working DatabaseEngine	✅ Implemented	🟢 Start Here
↳ Singleton/Scoped/Transient Lifetime Variants	Every Add* with a lifetime choice ships as Add.../AddScoped.../AddTransient... twins sharing one factory delegate	✅ Implemented	🔵 Core
Engine Options Configuration Surface	IOptions<T>-based configuration for engine services, set via configure delegates on each Add*() DI call	✅ Implemented	🔵 Core
↳ Options Validation Hooks	AddOptions<T>().Validate(...) is wired on every options type but its predicate is a no-op stub today; ResourceOptions.Validate() / PagedMMFOptions.IsValid are the real, directly-callable fail-fast checks	🚧 Partial	🟣 Advanced
Database Seeding	TyphonOptions.Seed(revision, tx => …) registers revision-stepped, crash-safe seed steps applied automatically at engine open — a fresh database runs them all, an existing one catches up on new ones; DatabaseEngine.IsNewlyCreated is the low-level primitive	✅ Implemented	🟢 Start Here
Clean-Slate Database File Deletion	EnsureFileDeleted<TO>(IServiceProvider) resolves IOptions<TO> in a fresh scope and deletes the backing database file it points at — the supported way to start test/tooling runs from a clean slate	✅ Implemented	🔵 Core
Profiler Launch Override Hook	AddTyphonProfiler(Func<ProfilerLaunchConfig,ProfilerLaunchConfig>) lets a host adjust the profiler launch config (resolved from typhon.telemetry.json + env) in code, e.g. to layer CLI args on top; zero-code default self-wiring is unaffected if not called	✅ Implemented	🟣 Advanced

Internal Features

Feature	Summary	Status
Pluggable WAL I/O Backend (IWalFileIO seam)	AddDatabaseEngine resolves an optional internal IWalFileIO from the container so tests/benchmarks can register InMemoryWalFileIO and run the full WAL + checkpoint pipeline with zero disk I/O; production falls back to the disk-backed WalFileIO — the interface and both implementations are internal, not reachable from application code	✅ Implemented