Elarion.FeatureFlags.FeatureManagement 0.2.3-preview.45.1

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Module-based handler pipelines, compile-time registration, JSON-RPC hosting, MCP tools for AI agents, and scheduled jobs.

Declare intent next to your code; let source generators do the wiring. No runtime reflection scanning.

AI-native by design: the same handlers that power your API are exposed to AI agents as MCP tools — generated from your code at compile time, with no separate tool definitions or duplicated schemas.

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Elarion's central idea is simple: your application assemblies define modules and handlers; your host assembly only wires infrastructure, transport, and deployment. Everything that can be discovered from your code — handlers, validators, services, scheduled jobs, RPC methods, EF Core DbSets — is emitted by source generators at compile time instead of scanned by reflection at startup.

[Handler("clients.get")]
public sealed class GetClient(AppDbContext db)
    : IHandler<GetClient.Query, Result<GetClient.Response>> {
    public sealed record Query(Guid Id);
    public sealed record Response(Guid Id, string Name);

    public async ValueTask<Result<Response>> HandleAsync(Query query, CancellationToken ct) {
        var client = await db.Clients
            .Where(c => c.Id == query.Id)
            .Select(c => new Response(c.Id, c.Name))
            .FirstOrDefaultAsync(ct);

        return client is null
            ? AppError.NotFound($"Client {query.Id} was not found.")
            : client;
    }
}

That one class is a use case, a registered service, a JSON-RPC method, an MCP tool for AI agents, and (optionally) a schema-exported TypeScript contract — with no entry added to any Program.cs registration list. The operation name is optional: [Handler] alone infers {module}.{operation} by convention (here clients.get), while an explicit name is recommended for stable public/wire contracts.

Why Elarion

• Compile-time, not reflection — handlers, services, validators, modules, RPC maps, and scheduled jobs become ordinary DI code. Startup is deterministic and AOT-friendly; missing wiring is a build error, not a runtime surprise.
• Modules own their surface — a module is a namespace plus an [AppModule] marker. Add a handler under it and the module publishes it automatically.
• Transport-neutral results — handlers return Result<T> with a transport-agnostic AppError; the host maps failures to JSON-RPC, HTTP, or anything else.
• One bus, many surfaces — every handler maps onto a single transport-neutral HandlerDispatcher (Elarion.Abstractions.Dispatch); JSON-RPC and MCP are thin adapters over that one bus, each serving only the operations flagged for it. Define a handler once and choose its surfaces with the Transports flag.
• End-to-end JSON-RPC — mark a handler with [Handler], export a schema at build time, and generate a typed TypeScript + Zod client.
• AI-native, no extra code — expose the same [Handler] handlers to AI agents as an MCP server. MCP is an adapter over the shared HandlerDispatcher, so a tool is just a handler flagged HandlerTransports.Mcp. Tool names, descriptions, and input schemas are generated from your handlers and [Description] attributes at compile time — no separate tool layer, no duplicated schemas, no runtime reflection. Choose a handler's transports with [Handler(Transports = …)] (JSON-RPC, MCP, or both) and rename a tool with [McpHandler].
• Feature flags & variants — gate any handler with [FeatureGate]; a generated decorator evaluates the flag before the handler runs and a closed gate returns 404 Not Found, so a disabled feature is indistinguishable from one that doesn't exist (the name is never leaked). [FeatureVariant] swaps a [Service] implementation per user behind a flag. Both work identically under JSON-RPC, MCP, and HTTP, against any OpenFeature provider.
• Exactly-once command handlers — mark a handler [Idempotent] and the idempotency key commits atomically with the business writes, a retried request replays the stored result, a concurrent duplicate returns 409, and there is no distributed lock.
• In-process scheduling — source-generated scheduled jobs with explicit overlap, misfire, and resilience policies.
• Observable by default — JSON-RPC, scheduling, caching, and resilience emit OpenTelemetry-compatible traces and metrics through System.Diagnostics, with no SDK dependency forced on you.

Install

<ItemGroup>
  <PackageReference Include="Elarion" Version="0.2.2" />
</ItemGroup>

// Turn the generators on, once per assembly
[assembly: UseElarion]

The Quickstart builds a module, a handler, and a working JSON-RPC endpoint end to end.

Packages

Documentation

Full guides live at elarion.wimmesberger.dev and in docs/:

• Introduction · Why Elarion · Installation · Quickstart
• Concepts — source generation, handlers, results & errors, modules, services, validators, pipelines, cross-module communication
• Capabilities — hosting, HTTP endpoints, JSON-RPC, MCP server, authorization, feature flags, identity, scheduling, resilience, events & messaging, EF Core, caching, current user, blob storage, telemetry
• Reference — packages, configuration, troubleshooting

Requirements

• .NET 10 SDK or later
• ASP.NET Core for the JSON-RPC HTTP transport
• Node.js 18+ for the TypeScript client generator

Contributing

Issues and pull requests are welcome. See CONTRIBUTING.md for the development workflow, validation commands, architecture boundaries, and the publishing process. By participating you agree to the Code of Conduct.

Security

Please report vulnerabilities privately — see the security policy.

License

Elarion is licensed under the Apache License 2.0.