Add unit tests for RabbitMq and Udp transport servers and clients

- Implemented comprehensive unit tests for RabbitMqTransportServer, covering constructor, disposal, connection management, event handlers, and exception handling.
- Added configuration tests for RabbitMqTransportServer to validate SSL, durable queues, auto-recovery, and custom virtual host options.
- Created unit tests for UdpFrameProtocol, including frame parsing and serialization, header size validation, and round-trip data preservation.
- Developed tests for UdpTransportClient, focusing on connection handling, event subscriptions, and exception scenarios.
- Established tests for UdpTransportServer, ensuring proper start/stop behavior, connection state management, and event handling.
- Included tests for UdpTransportOptions to verify default values and modification capabilities.
- Enhanced service registration tests for Udp transport services in the dependency injection container.

docs/modules/gateway/openapi.md

@@ -0,0 +1,325 @@
+# Gateway OpenAPI Implementation
+
+This document describes the implementation architecture of OpenAPI document aggregation in the StellaOps Router Gateway.
+
+## Architecture
+
+The Gateway generates OpenAPI 3.1.0 documentation by aggregating schemas and endpoint metadata from connected microservices.
+
+### Component Overview
+
+```
+┌─────────────────────────────────────────────────────────────────────┐
+│                         Gateway                                      │
+├─────────────────────────────────────────────────────────────────────┤
+│                                                                      │
+│  ┌──────────────────┐    ┌────────────────────┐                     │
+│  │ ConnectionManager │───►│ InMemoryRoutingState│                    │
+│  │                   │    │                    │                     │
+│  │ - OnHelloReceived │    │ - Connections[]    │                     │
+│  │ - OnConnClosed    │    │ - Endpoints        │                     │
+│  └──────────────────┘    │ - Schemas          │                     │
+│           │               └─────────┬──────────┘                     │
+│           │                         │                                │
+│           ▼                         ▼                                │
+│  ┌──────────────────┐    ┌────────────────────┐                     │
+│  │ OpenApiDocument  │◄───│ GatewayOpenApi     │                     │
+│  │ Cache            │    │ DocumentCache      │                     │
+│  │                  │    │                    │                     │
+│  │ - Invalidate()   │    │ - TTL expiration   │                     │
+│  └──────────────────┘    │ - ETag generation  │                     │
+│                          └─────────┬──────────┘                     │
+│                                    │                                │
+│                                    ▼                                │
+│                          ┌────────────────────┐                     │
+│                          │ OpenApiDocument    │                     │
+│                          │ Generator          │                     │
+│                          │                    │                     │
+│                          │ - GenerateInfo()   │                     │
+│                          │ - GeneratePaths()  │                     │
+│                          │ - GenerateTags()   │                     │
+│                          │ - GenerateSchemas()│                     │
+│                          └─────────┬──────────┘                     │
+│                                    │                                │
+│                                    ▼                                │
+│                          ┌────────────────────┐                     │
+│                          │ ClaimSecurity      │                     │
+│                          │ Mapper             │                     │
+│                          │                    │                     │
+│                          │ - SecuritySchemes  │                     │
+│                          │ - SecurityRequire  │                     │
+│                          └────────────────────┘                     │
+│                                                                      │
+└─────────────────────────────────────────────────────────────────────┘
+```
+
+### Components
+
+| Component | File | Responsibility |
+|-----------|------|----------------|
+| `IOpenApiDocumentGenerator` | `OpenApi/IOpenApiDocumentGenerator.cs` | Interface for document generation |
+| `OpenApiDocumentGenerator` | `OpenApi/OpenApiDocumentGenerator.cs` | Builds OpenAPI 3.1.0 JSON |
+| `IGatewayOpenApiDocumentCache` | `OpenApi/IGatewayOpenApiDocumentCache.cs` | Interface for document caching |
+| `GatewayOpenApiDocumentCache` | `OpenApi/GatewayOpenApiDocumentCache.cs` | TTL + invalidation caching |
+| `ClaimSecurityMapper` | `OpenApi/ClaimSecurityMapper.cs` | Maps claims to OAuth2 scopes |
+| `OpenApiEndpoints` | `OpenApi/OpenApiEndpoints.cs` | HTTP endpoint handlers |
+| `OpenApiAggregationOptions` | `OpenApi/OpenApiAggregationOptions.cs` | Configuration options |
+
+---
+
+## OpenApiDocumentGenerator
+
+Generates the complete OpenAPI 3.1.0 document from routing state.
+
+### Process Flow
+
+1. **Collect connections** from `IGlobalRoutingState`
+2. **Generate info** section from `OpenApiAggregationOptions`
+3. **Generate paths** by iterating all endpoints across connections
+4. **Generate components** including schemas and security schemes
+5. **Generate tags** from unique service names
+
+### Schema Handling
+
+Schemas are prefixed with service name to avoid naming conflicts:
+
+```csharp
+var prefixedId = $"{conn.Instance.ServiceName}_{schemaId}";
+// billing_CreateInvoiceRequest
+```
+
+### Operation ID Generation
+
+Operation IDs follow a consistent pattern:
+
+```csharp
+var operationId = $"{serviceName}_{path}_{method}";
+// billing_invoices_POST
+```
+
+---
+
+## GatewayOpenApiDocumentCache
+
+Implements caching with TTL expiration and content-based ETags.
+
+### Cache Behavior
+
+| Trigger | Action |
+|---------|--------|
+| First request | Generate and cache document |
+| Subsequent requests (within TTL) | Return cached document |
+| TTL expired | Regenerate document |
+| Connection added/removed | Invalidate cache |
+
+### ETag Generation
+
+ETags are computed from SHA256 hash of document content:
+
+```csharp
+var hash = SHA256.HashData(Encoding.UTF8.GetBytes(documentJson));
+var etag = $"\"{Convert.ToHexString(hash)[..16]}\"";
+```
+
+### Thread Safety
+
+The cache uses locking to ensure thread-safe regeneration:
+
+```csharp
+lock (_lock)
+{
+    if (_cachedDocument is null || IsExpired())
+    {
+        RegenerateDocument();
+    }
+}
+```
+
+---
+
+## ClaimSecurityMapper
+
+Maps endpoint claim requirements to OpenAPI security schemes.
+
+### Security Scheme Generation
+
+Always generates `BearerAuth` scheme. Generates `OAuth2` scheme only when endpoints have claim requirements:
+
+```csharp
+public static JsonObject GenerateSecuritySchemes(
+    IEnumerable<EndpointDescriptor> endpoints,
+    string tokenUrl)
+{
+    var schemes = new JsonObject();
+
+    // Always add BearerAuth
+    schemes["BearerAuth"] = new JsonObject { ... };
+
+    // Collect scopes from all endpoints
+    var scopes = CollectScopes(endpoints);
+
+    // Add OAuth2 only if scopes exist
+    if (scopes.Count > 0)
+    {
+        schemes["OAuth2"] = GenerateOAuth2Scheme(tokenUrl, scopes);
+    }
+
+    return schemes;
+}
+```
+
+### Per-Operation Security
+
+Each endpoint with claims gets a security requirement:
+
+```csharp
+public static JsonArray GenerateSecurityRequirement(EndpointDescriptor endpoint)
+{
+    if (endpoint.RequiringClaims.Count == 0)
+        return new JsonArray(); // No security required
+
+    return new JsonArray
+    {
+        new JsonObject
+        {
+            ["BearerAuth"] = new JsonArray(),
+            ["OAuth2"] = new JsonArray(claims.Select(c => c.Type))
+        }
+    };
+}
+```
+
+---
+
+## Configuration Reference
+
+### OpenApiAggregationOptions
+
+| Property | Type | Default | Description |
+|----------|------|---------|-------------|
+| `Title` | `string` | `"StellaOps Gateway API"` | API title |
+| `Description` | `string` | `"Unified API..."` | API description |
+| `Version` | `string` | `"1.0.0"` | API version |
+| `ServerUrl` | `string` | `"/"` | Base server URL |
+| `CacheTtlSeconds` | `int` | `60` | Cache TTL |
+| `Enabled` | `bool` | `true` | Enable/disable |
+| `LicenseName` | `string` | `"AGPL-3.0-or-later"` | License name |
+| `ContactName` | `string?` | `null` | Contact name |
+| `ContactEmail` | `string?` | `null` | Contact email |
+| `TokenUrl` | `string` | `"/auth/token"` | OAuth2 token URL |
+
+### YAML Configuration
+
+```yaml
+OpenApi:
+  Title: "My Gateway API"
+  Description: "Unified API for all microservices"
+  Version: "2.0.0"
+  ServerUrl: "https://api.example.com"
+  CacheTtlSeconds: 60
+  Enabled: true
+  LicenseName: "AGPL-3.0-or-later"
+  ContactName: "API Team"
+  ContactEmail: "api@example.com"
+  TokenUrl: "/auth/token"
+```
+
+---
+
+## Service Registration
+
+Services are registered via dependency injection in `ServiceCollectionExtensions`:
+
+```csharp
+services.Configure<OpenApiAggregationOptions>(
+    configuration.GetSection("OpenApi"));
+services.AddSingleton<IOpenApiDocumentGenerator, OpenApiDocumentGenerator>();
+services.AddSingleton<IGatewayOpenApiDocumentCache, GatewayOpenApiDocumentCache>();
+```
+
+Endpoints are mapped in `ApplicationBuilderExtensions`:
+
+```csharp
+app.MapGatewayOpenApiEndpoints();
+```
+
+---
+
+## Cache Invalidation
+
+The `ConnectionManager` invalidates the cache on connection changes:
+
+```csharp
+private Task HandleHelloReceivedAsync(ConnectionState state, HelloPayload payload)
+{
+    _routingState.AddConnection(state);
+    _openApiCache?.Invalidate(); // Invalidate on new connection
+    return Task.CompletedTask;
+}
+
+private Task HandleConnectionClosedAsync(string connectionId)
+{
+    _routingState.RemoveConnection(connectionId);
+    _openApiCache?.Invalidate(); // Invalidate on disconnect
+    return Task.CompletedTask;
+}
+```
+
+---
+
+## Extension Points
+
+### Custom Routing Plugins
+
+The Gateway supports custom routing plugins via `IRoutingPlugin`. While not directly related to OpenAPI, routing decisions can affect which endpoints are exposed.
+
+### Future Enhancements
+
+Potential extension points for future development:
+
+- **Schema Transformers**: Modify schemas before aggregation
+- **Tag Customization**: Custom tag generation logic
+- **Response Examples**: Include example responses from connected services
+- **Webhooks**: Notify external systems on document changes
+
+---
+
+## Testing
+
+Unit tests are located in `src/Gateway/__Tests/StellaOps.Gateway.WebService.Tests/OpenApi/`:
+
+| Test File | Coverage |
+|-----------|----------|
+| `OpenApiDocumentGeneratorTests.cs` | Document structure, schema merging, tag generation |
+| `GatewayOpenApiDocumentCacheTests.cs` | TTL expiry, invalidation, ETag consistency |
+| `ClaimSecurityMapperTests.cs` | Security scheme generation from claims |
+
+### Test Patterns
+
+```csharp
+[Fact]
+public void GenerateDocument_WithConnections_GeneratesPaths()
+{
+    // Arrange
+    var endpoint = new EndpointDescriptor { ... };
+    var connection = CreateConnection("inventory", "1.0.0", endpoint);
+    _routingState.Setup(x => x.GetAllConnections()).Returns([connection]);
+
+    // Act
+    var document = _sut.GenerateDocument();
+
+    // Assert
+    var doc = JsonDocument.Parse(document);
+    doc.RootElement.GetProperty("paths")
+        .TryGetProperty("/api/items", out _)
+        .Should().BeTrue();
+}
+```
+
+---
+
+## See Also
+
+- [Schema Validation](../router/schema-validation.md) - JSON Schema validation in microservices
+- [OpenAPI Aggregation](../router/openapi-aggregation.md) - Configuration and usage guide
+- [API Overview](../../api/overview.md) - General API conventions

docs/modules/router/README.md

@@ -0,0 +1,165 @@
+# Router Module
+
+The StellaOps Router is the internal communication infrastructure that enables microservices to communicate through a central gateway using efficient binary protocols.
+
+## Why Another Gateway?
+
+StellaOps already has HTTP-based services. The Router exists because:
+
+1. **Performance**: Binary framing eliminates HTTP overhead for internal traffic
+2. **Streaming**: First-class support for large payloads (SBOMs, scan results, evidence bundles)
+3. **Cancellation**: Request abortion propagates across service boundaries
+4. **Health-aware Routing**: Automatic failover based on heartbeat and latency
+5. **Claims-based Auth**: Unified authorization via Authority integration
+6. **Transport Flexibility**: UDP for small payloads, TCP/TLS for streams, RabbitMQ for queuing
+
+The Router replaces the Serdica HTTP-to-RabbitMQ pattern with a simpler, generic design.
+
+## Architecture Overview
+
+```
+                                   ┌─────────────────────────────────┐
+                                   │     StellaOps.Gateway.WebService│
+  HTTP Clients ────────────────────►  (HTTP ingress)                 │
+                                   │                                 │
+                                   │  ┌─────────────────────────────┐│
+                                   │  │ Endpoint Resolution         ││
+                                   │  │ Authorization (Claims)      ││
+                                   │  │ Routing Decision            ││
+                                   │  │ Transport Dispatch          ││
+                                   │  └─────────────────────────────┘│
+                                   └──────────────┬──────────────────┘
+                                                  │
+                        ┌─────────────────────────┼─────────────────────────┐
+                        │                         │                         │
+                        ▼                         ▼                         ▼
+              ┌─────────────────┐       ┌─────────────────┐       ┌─────────────────┐
+              │ Billing         │       │ Inventory       │       │ Scanner         │
+              │ Microservice    │       │ Microservice    │       │ Microservice    │
+              │                 │       │                 │       │                 │
+              │ TCP/TLS         │       │ InMemory        │       │ RabbitMQ        │
+              └─────────────────┘       └─────────────────┘       └─────────────────┘
+```
+
+## Components
+
+| Component | Project | Purpose |
+|-----------|---------|---------|
+| Gateway | `StellaOps.Gateway.WebService` | HTTP ingress, routing, authorization |
+| Microservice SDK | `StellaOps.Microservice` | SDK for building microservices |
+| Source Generator | `StellaOps.Microservice.SourceGen` | Compile-time endpoint discovery |
+| Common | `StellaOps.Router.Common` | Shared types, frames, interfaces |
+| Config | `StellaOps.Router.Config` | Configuration models, YAML binding |
+| InMemory Transport | `StellaOps.Router.Transport.InMemory` | Testing transport |
+| TCP Transport | `StellaOps.Router.Transport.Tcp` | Production TCP transport |
+| TLS Transport | `StellaOps.Router.Transport.Tls` | Encrypted TCP transport |
+| UDP Transport | `StellaOps.Router.Transport.Udp` | Small payload transport |
+| RabbitMQ Transport | `StellaOps.Router.Transport.RabbitMQ` | Message queue transport |
+
+## Solution Structure
+
+```
+StellaOps.Router.slnx
+├── src/__Libraries/
+│   ├── StellaOps.Router.Common/
+│   ├── StellaOps.Router.Config/
+│   ├── StellaOps.Router.Transport.InMemory/
+│   ├── StellaOps.Router.Transport.Tcp/
+│   ├── StellaOps.Router.Transport.Tls/
+│   ├── StellaOps.Router.Transport.Udp/
+│   ├── StellaOps.Router.Transport.RabbitMQ/
+│   ├── StellaOps.Microservice/
+│   └── StellaOps.Microservice.SourceGen/
+├── src/Gateway/
+│   └── StellaOps.Gateway.WebService/
+└── tests/
+    └── (test projects)
+```
+
+## Key Documents
+
+| Document | Purpose |
+|----------|---------|
+| [architecture.md](architecture.md) | Canonical specification and requirements |
+| [schema-validation.md](schema-validation.md) | JSON Schema validation feature |
+| [openapi-aggregation.md](openapi-aggregation.md) | OpenAPI document generation |
+| [migration-guide.md](migration-guide.md) | WebService to Microservice migration |
+
+## Quick Start
+
+### Gateway
+
+```csharp
+var builder = WebApplication.CreateBuilder(args);
+
+// Add router services
+builder.Services.AddGatewayServices(builder.Configuration);
+builder.Services.AddInMemoryTransport(); // or TCP, TLS, etc.
+
+var app = builder.Build();
+
+// Configure pipeline
+app.UseGatewayMiddleware();
+
+await app.RunAsync();
+```
+
+### Microservice
+
+```csharp
+var builder = Host.CreateApplicationBuilder(args);
+
+builder.Services.AddStellaMicroservice(options =>
+{
+    options.ServiceName = "billing";
+    options.Version = "1.0.0";
+    options.Region = "us-east-1";
+});
+
+builder.Services.AddInMemoryTransportClient();
+
+await builder.Build().RunAsync();
+```
+
+### Endpoint Definition
+
+```csharp
+[StellaEndpoint("POST", "/invoices")]
+[ValidateSchema(Summary = "Create invoice")]
+public sealed class CreateInvoiceEndpoint : IStellaEndpoint<CreateInvoiceRequest, CreateInvoiceResponse>
+{
+    public Task<CreateInvoiceResponse> HandleAsync(
+        CreateInvoiceRequest request,
+        CancellationToken ct)
+    {
+        return Task.FromResult(new CreateInvoiceResponse
+        {
+            InvoiceId = Guid.NewGuid().ToString()
+        });
+    }
+}
+```
+
+## Invariants
+
+These are non-negotiable design constraints:
+
+- **Method + Path** is the endpoint identity
+- **Strict semver** for version matching
+- **Region from GatewayNodeConfig** (not headers/host)
+- **No HTTP transport** between gateway and microservices
+- **RequiringClaims** (not AllowedRoles) for authorization
+- **Opaque body handling** (router doesn't interpret payloads)
+
+## Building
+
+```bash
+# Build router solution
+dotnet build StellaOps.Router.slnx
+
+# Run tests
+dotnet test StellaOps.Router.slnx
+
+# Run gateway
+dotnet run --project src/Gateway/StellaOps.Gateway.WebService
+```

docs/modules/router/architecture.md

@@ -0,0 +1,519 @@
+# Router Architecture
+
+This document is the canonical specification for the StellaOps Router system.
+
+## System Architecture
+
+### Scope
+
+- A single HTTP ingress service (`StellaOps.Gateway.WebService`) handles all external HTTP traffic
+- Microservices communicate with the Gateway using binary transports (TCP, TLS, UDP, RabbitMQ)
+- HTTP is not used for internal microservice-to-gateway traffic
+- Request/response bodies are opaque to the router (raw bytes/streams)
+
+### Transport Architecture
+
+Each transport connection carries:
+
+- Initial registration (HELLO) and endpoint configuration
+- Ongoing heartbeats
+- Request/response data frames
+- Streaming data frames
+- Cancellation frames
+
+```
+┌─────────────────┐                           ┌─────────────────┐
+│   Microservice  │                           │     Gateway     │
+│                 │         HELLO             │                 │
+│   Endpoints:    │ ─────────────────────────►│   Routing       │
+│   - POST /items │         HEARTBEAT         │   State         │
+│   - GET /items  │ ◄────────────────────────►│                 │
+│                 │                           │   Connections[] │
+│                 │  REQUEST / RESPONSE       │                 │
+│                 │ ◄────────────────────────►│                 │
+│                 │                           │                 │
+│                 │  STREAM_DATA / CANCEL     │                 │
+│                 │ ◄────────────────────────►│                 │
+└─────────────────┘                           └─────────────────┘
+```
+
+---
+
+## Service Identity
+
+### Instance Identity
+
+Each microservice instance is identified by:
+
+| Field | Type | Description |
+|-------|------|-------------|
+| `ServiceName` | string | Logical service name (e.g., "billing") |
+| `Version` | string | Semantic version (`major.minor.patch`) |
+| `Region` | string | Deployment region (e.g., "us-east-1") |
+| `InstanceId` | string | Unique instance identifier |
+
+### Version Matching
+
+- Version matching is strict semver equality
+- Router only routes to instances with exact version match
+- Default version used when client doesn't specify
+
+### Region Configuration
+
+Gateway region comes from `GatewayNodeConfig`:
+
+```csharp
+public sealed class GatewayNodeConfig
+{
+    public required string Region { get; init; }     // e.g., "eu1"
+    public required string NodeId { get; init; }     // e.g., "gw-eu1-01"
+    public required string Environment { get; init; } // e.g., "prod"
+}
+```
+
+Region is never derived from HTTP headers or URL hostnames.
+
+---
+
+## Endpoint Model
+
+### Endpoint Identity
+
+Endpoint identity is `(HTTP Method, Path)`:
+
+| Field | Example |
+|-------|---------|
+| Method | `GET`, `POST`, `PUT`, `PATCH`, `DELETE` |
+| Path | `/invoices`, `/items/{id}`, `/users/{userId}/orders` |
+
+### Endpoint Descriptor
+
+Each endpoint includes:
+
+```csharp
+public sealed class EndpointDescriptor
+{
+    public required string Method { get; init; }
+    public required string Path { get; init; }
+    public required string ServiceName { get; init; }
+    public required string Version { get; init; }
+    public TimeSpan DefaultTimeout { get; init; }
+    public bool SupportsStreaming { get; init; }
+    public IReadOnlyList<ClaimRequirement> RequiringClaims { get; init; } = [];
+    public EndpointSchemaInfo? SchemaInfo { get; init; }
+}
+```
+
+### Path Matching
+
+- ASP.NET-style route templates
+- Parameter segments: `{id}`, `{userId}`
+- Case sensitivity and trailing slash handling follow ASP.NET conventions
+
+---
+
+## Routing Algorithm
+
+### Instance Selection
+
+Given `(ServiceName, Version, Method, Path)`:
+
+1. **Filter candidates**:
+   - Match `ServiceName` exactly
+   - Match `Version` exactly (strict semver)
+   - Health status in acceptable set (`Healthy` or `Degraded`)
+
+2. **Region preference**:
+   - Prefer instances where `Region == GatewayNodeConfig.Region`
+   - Fall back to configured neighbor regions
+   - Fall back to all other regions
+
+3. **Within region tier**:
+   - Prefer lower `AveragePingMs`
+   - If tied, prefer more recent `LastHeartbeatUtc`
+   - If still tied, use round-robin balancing
+
+### Instance Health
+
+```csharp
+public enum InstanceHealthStatus
+{
+    Unknown,
+    Healthy,
+    Degraded,
+    Draining,
+    Unhealthy
+}
+```
+
+Health metadata per connection:
+
+| Field | Type | Description |
+|-------|------|-------------|
+| `Status` | enum | Current health status |
+| `LastHeartbeatUtc` | DateTime | Last heartbeat timestamp |
+| `AveragePingMs` | double | Average round-trip latency |
+
+---
+
+## Transport Layer
+
+### Transport Types
+
+| Transport | Use Case | Streaming | Notes |
+|-----------|----------|-----------|-------|
+| InMemory | Testing | Yes | In-process channels |
+| TCP | Production | Yes | Length-prefixed frames |
+| TLS | Secure | Yes | Certificate-based encryption |
+| UDP | Small payloads | No | Single datagram per frame |
+| RabbitMQ | Queuing | Yes | Exchange/queue routing |
+
+### Transport Plugin Interface
+
+```csharp
+public interface ITransportServer
+{
+    Task StartAsync(CancellationToken ct);
+    Task StopAsync(CancellationToken ct);
+    event Func<ConnectionState, HelloPayload, Task> OnHelloReceived;
+    event Func<ConnectionState, HeartbeatPayload, Task> OnHeartbeatReceived;
+    event Func<string, Task> OnConnectionClosed;
+}
+
+public interface ITransportClient
+{
+    Task ConnectAsync(CancellationToken ct);
+    Task DisconnectAsync(CancellationToken ct);
+    Task SendFrameAsync(Frame frame, CancellationToken ct);
+}
+```
+
+### Frame Types
+
+```csharp
+public enum FrameType : byte
+{
+    Hello = 1,
+    Heartbeat = 2,
+    Request = 3,
+    Response = 4,
+    RequestStreamData = 5,
+    ResponseStreamData = 6,
+    Cancel = 7
+}
+```
+
+---
+
+## Gateway Pipeline
+
+### HTTP Middleware Stack
+
+```
+Request ─►│ ForwardedHeaders        │
+          │ RequestLogging          │
+          │ ErrorHandling           │
+          │ Authentication          │
+          │ EndpointResolution      │  ◄── (Method, Path) → EndpointDescriptor
+          │ Authorization           │  ◄── RequiringClaims check
+          │ RoutingDecision         │  ◄── Select connection/instance
+          │ TransportDispatch       │  ◄── Send to microservice
+          ▼
+```
+
+### Connection State
+
+Per-connection state maintained by Gateway:
+
+```csharp
+public sealed class ConnectionState
+{
+    public required string ConnectionId { get; init; }
+    public required InstanceDescriptor Instance { get; init; }
+    public InstanceHealthStatus Status { get; set; }
+    public DateTime? LastHeartbeatUtc { get; set; }
+    public double AveragePingMs { get; set; }
+    public TransportType TransportType { get; init; }
+    public Dictionary<(string Method, string Path), EndpointDescriptor> Endpoints { get; } = new();
+    public IReadOnlyDictionary<string, SchemaDefinition> Schemas { get; init; } = new Dictionary<string, SchemaDefinition>();
+}
+```
+
+### Payload Handling
+
+The Gateway treats bodies as opaque byte sequences:
+
+- No deserialization or schema interpretation
+- Headers and bytes forwarded as-is
+- Schema validation is microservice responsibility
+
+### Payload Limits
+
+Configurable limits protect against resource exhaustion:
+
+| Limit | Scope |
+|-------|-------|
+| `MaxRequestBytesPerCall` | Single request |
+| `MaxRequestBytesPerConnection` | All requests on connection |
+| `MaxAggregateInflightBytes` | All in-flight across gateway |
+
+Exceeded limits result in:
+- Early rejection (HTTP 413) if `Content-Length` known
+- Mid-stream abort with CANCEL frame
+- Appropriate error response (413 or 503)
+
+---
+
+## Microservice SDK
+
+### Configuration
+
+```csharp
+services.AddStellaMicroservice(options =>
+{
+    options.ServiceName = "billing";
+    options.Version = "1.0.0";
+    options.Region = "us-east-1";
+    options.InstanceId = Guid.NewGuid().ToString();
+    options.ServiceDescription = "Invoice processing service";
+});
+```
+
+### Endpoint Declaration
+
+Attributes:
+
+```csharp
+[StellaEndpoint("POST", "/invoices")]
+public sealed class CreateInvoiceEndpoint : IStellaEndpoint<CreateInvoiceRequest, CreateInvoiceResponse>
+```
+
+### Handler Interfaces
+
+**Typed handler** (JSON serialization):
+
+```csharp
+public interface IStellaEndpoint<TRequest, TResponse>
+{
+    Task<TResponse> HandleAsync(TRequest request, CancellationToken ct);
+}
+
+public interface IStellaEndpoint<TResponse>
+{
+    Task<TResponse> HandleAsync(CancellationToken ct);
+}
+```
+
+**Raw handler** (streaming):
+
+```csharp
+public interface IRawStellaEndpoint
+{
+    Task<RawResponse> HandleAsync(RawRequestContext ctx, CancellationToken ct);
+}
+```
+
+### Endpoint Discovery
+
+Two mechanisms:
+
+1. **Source Generator** (preferred): Compile-time discovery via Roslyn
+2. **Reflection** (fallback): Runtime assembly scanning
+
+### Connection Behavior
+
+On connection:
+1. Send HELLO with instance info and endpoints
+2. Start heartbeat timer
+3. Listen for REQUEST frames
+
+HELLO payload:
+
+```csharp
+public sealed class HelloPayload
+{
+    public required InstanceDescriptor Instance { get; init; }
+    public required IReadOnlyList<EndpointDescriptor> Endpoints { get; init; }
+    public IReadOnlyDictionary<string, SchemaDefinition> Schemas { get; init; } = new Dictionary<string, SchemaDefinition>();
+    public ServiceOpenApiInfo? OpenApiInfo { get; init; }
+}
+```
+
+---
+
+## Authorization
+
+### Claims-based Model
+
+Authorization uses `RequiringClaims`, not roles:
+
+```csharp
+public sealed class ClaimRequirement
+{
+    public required string Type { get; init; }
+    public string? Value { get; init; }
+}
+```
+
+### Precedence
+
+1. Microservice provides defaults in HELLO
+2. Authority can override centrally
+3. Gateway enforces final effective claims
+
+### Enforcement
+
+Gateway `AuthorizationMiddleware`:
+- Validates user principal has all required claims
+- Empty claims list = authenticated access only
+- Missing claim = 403 Forbidden
+
+---
+
+## Cancellation
+
+### CANCEL Frame
+
+```csharp
+public sealed class CancelPayload
+{
+    public required string Reason { get; init; }
+    // Values: "ClientDisconnected", "Timeout", "PayloadLimitExceeded", "Shutdown"
+}
+```
+
+### Gateway sends CANCEL when:
+
+- HTTP client disconnects (`HttpContext.RequestAborted`)
+- Request timeout elapses
+- Payload limit exceeded
+- Gateway shutdown
+
+### Microservice handles CANCEL:
+
+- Maps correlation ID to `CancellationTokenSource`
+- Calls `Cancel()` on the source
+- Handler receives cancellation via `CancellationToken`
+
+---
+
+## Streaming
+
+### Buffered vs Streaming
+
+| Mode | Request Body | Response Body | Use Case |
+|------|--------------|---------------|----------|
+| Buffered | Full in memory | Full in memory | Small payloads |
+| Streaming | Chunked frames | Chunked frames | Large payloads |
+
+### Frame Flow (Streaming)
+
+```
+Gateway                              Microservice
+   │                                      │
+   │  REQUEST (headers only)              │
+   │ ────────────────────────────────────►│
+   │                                      │
+   │  REQUEST_STREAM_DATA (chunk 1)       │
+   │ ────────────────────────────────────►│
+   │                                      │
+   │  REQUEST_STREAM_DATA (chunk n)       │
+   │ ────────────────────────────────────►│
+   │                                      │
+   │  REQUEST_STREAM_DATA (final=true)    │
+   │ ────────────────────────────────────►│
+   │                                      │
+   │                   RESPONSE           │
+   │◄────────────────────────────────────│
+   │                                      │
+   │         RESPONSE_STREAM_DATA         │
+   │◄────────────────────────────────────│
+```
+
+---
+
+## Heartbeat & Health
+
+### Heartbeat Frame
+
+Sent at regular intervals over the same connection as requests:
+
+```csharp
+public sealed class HeartbeatPayload
+{
+    public required InstanceHealthStatus Status { get; init; }
+    public int InflightRequests { get; init; }
+    public double ErrorRate { get; init; }
+}
+```
+
+### Health Tracking
+
+Gateway tracks:
+- `LastHeartbeatUtc` per connection
+- Derives status from heartbeat recency
+- Marks stale instances as Unhealthy
+- Uses health in routing decisions
+
+---
+
+## Configuration
+
+### Router YAML
+
+```yaml
+# router.yaml
+Gateway:
+  Region: "us-east-1"
+  NodeId: "gw-east-01"
+  Environment: "production"
+
+PayloadLimits:
+  MaxRequestBytesPerCall: 10485760        # 10 MB
+  MaxRequestBytesPerConnection: 104857600  # 100 MB
+  MaxAggregateInflightBytes: 1073741824    # 1 GB
+
+Services:
+  - ServiceName: billing
+    DefaultVersion: "1.0.0"
+    DefaultTransport: Tcp
+    Endpoints:
+      - Method: POST
+        Path: /invoices
+        TimeoutSeconds: 30
+        RequiringClaims:
+          - Type: "invoices:write"
+
+OpenApi:
+  Title: "StellaOps Gateway API"
+  CacheTtlSeconds: 60
+```
+
+### Hot Reload
+
+- YAML changes picked up at runtime
+- Routing state updated without restart
+- New services/endpoints added dynamically
+
+---
+
+## Error Mapping
+
+| Condition | HTTP Status |
+|-----------|-------------|
+| Version not found | 404 Not Found |
+| No healthy instance | 503 Service Unavailable |
+| Request timeout | 504 Gateway Timeout |
+| Payload too large | 413 Payload Too Large |
+| Unauthorized | 401 Unauthorized |
+| Missing claims | 403 Forbidden |
+| Validation error | 422 Unprocessable Entity |
+| Internal error | 500 Internal Server Error |
+
+---
+
+## See Also
+
+- [schema-validation.md](schema-validation.md) - JSON Schema validation
+- [openapi-aggregation.md](openapi-aggregation.md) - OpenAPI document generation
+- [migration-guide.md](migration-guide.md) - WebService to Microservice migration

docs/modules/router/migration-guide.md

@@ -0,0 +1,462 @@
+# StellaOps Router Migration Guide
+
+This guide describes how to migrate existing `StellaOps.*.WebService` projects to the new microservice pattern with the StellaOps Router.
+
+## Overview
+
+The router provides a transport-agnostic communication layer between services, replacing direct HTTP calls with efficient binary protocols (TCP, TLS, UDP, RabbitMQ). Benefits include:
+
+- **Performance**: Binary framing vs HTTP overhead
+- **Streaming**: First-class support for large payloads
+- **Cancellation**: Propagated across service boundaries
+- **Claims**: Authority-integrated authorization
+- **Health**: Automatic heartbeat and failover
+
+## Prerequisites
+
+Before migrating, ensure:
+
+1. Router infrastructure is deployed (Gateway, transports)
+2. Authority is configured with endpoint claims
+3. Local development environment has router.yaml configured
+
+## Migration Strategies
+
+### Strategy A: In-Place Adaptation
+
+Best for services that need to maintain HTTP compatibility during transition.
+
+```
+┌─────────────────────────────────────┐
+│  StellaOps.*.WebService             │
+│  ┌─────────────────────────────────┐│
+│  │  Existing HTTP Controllers      ││◄── HTTP clients (legacy)
+│  └─────────────────────────────────┘│
+│  ┌─────────────────────────────────┐│
+│  │  [StellaEndpoint] Handlers      ││◄── Router (new)
+│  └─────────────────────────────────┘│
+│  ┌─────────────────────────────────┐│
+│  │  Shared Domain Logic            ││
+│  └─────────────────────────────────┘│
+└─────────────────────────────────────┘
+```
+
+**Steps:**
+
+1. Add `StellaOps.Microservice` package reference
+2. Create handler classes for each HTTP route
+3. Handlers call existing service layer
+4. Register with router alongside HTTP
+5. Test via router
+6. Shift traffic gradually
+7. Remove HTTP controllers when ready
+
+**Pros:**
+- Gradual migration
+- No downtime
+- Can roll back easily
+
+**Cons:**
+- Dual maintenance during transition
+- May delay cleanup
+
+### Strategy B: Clean Split
+
+Best for major refactoring or when HTTP compatibility is not needed.
+
+```
+┌─────────────────────────────────────┐
+│  StellaOps.*.Domain                 │  ◄── Shared library
+│  (extracted business logic)         │
+└─────────────────────────────────────┘
+          ▲                 ▲
+          │                 │
+┌─────────┴───────┐ ┌───────┴─────────┐
+│ (Legacy)        │ │ (New)           │
+│ *.WebService    │ │ *.Microservice  │
+│ HTTP only       │ │ Router only     │
+└─────────────────┘ └─────────────────┘
+```
+
+**Steps:**
+
+1. Extract domain logic to `.Domain` library
+2. Create new `.Microservice` project
+3. Implement handlers using domain library
+4. Deploy alongside WebService
+5. Shift traffic to router
+6. Deprecate WebService
+
+**Pros:**
+- Clean architecture
+- No legacy code in new project
+- Clear separation of concerns
+
+**Cons:**
+- More upfront work
+- Requires domain extraction
+
+## Controller to Handler Mapping
+
+### Before (ASP.NET Controller)
+
+```csharp
+[ApiController]
+[Route("api/invoices")]
+public class InvoicesController : ControllerBase
+{
+    private readonly IInvoiceService _service;
+
+    [HttpPost]
+    [Authorize(Roles = "billing-admin")]
+    public async Task<IActionResult> Create(
+        [FromBody] CreateInvoiceRequest request,
+        CancellationToken ct)
+    {
+        var invoice = await _service.CreateAsync(request);
+        return Ok(new { invoice.Id });
+    }
+
+    [HttpGet("{id}")]
+    public async Task<IActionResult> Get(string id)
+    {
+        var invoice = await _service.GetAsync(id);
+        if (invoice == null) return NotFound();
+        return Ok(invoice);
+    }
+}
+```
+
+### After (Microservice Handler)
+
+```csharp
+// Handler for POST /api/invoices
+[StellaEndpoint("POST", "/api/invoices", RequiredClaims = ["invoices:write"])]
+public sealed class CreateInvoiceEndpoint : IStellaEndpoint<CreateInvoiceRequest, CreateInvoiceResponse>
+{
+    private readonly IInvoiceService _service;
+
+    public CreateInvoiceEndpoint(IInvoiceService service) => _service = service;
+
+    public async Task<CreateInvoiceResponse> HandleAsync(
+        CreateInvoiceRequest request,
+        CancellationToken ct)
+    {
+        var invoice = await _service.CreateAsync(request, ct);
+        return new CreateInvoiceResponse { InvoiceId = invoice.Id };
+    }
+}
+
+// Handler for GET /api/invoices/{id}
+[StellaEndpoint("GET", "/api/invoices/{id}", RequiredClaims = ["invoices:read"])]
+public sealed class GetInvoiceEndpoint : IStellaEndpoint<GetInvoiceRequest, GetInvoiceResponse>
+{
+    private readonly IInvoiceService _service;
+
+    public GetInvoiceEndpoint(IInvoiceService service) => _service = service;
+
+    public async Task<GetInvoiceResponse> HandleAsync(
+        GetInvoiceRequest request,
+        CancellationToken ct)
+    {
+        var invoice = await _service.GetAsync(request.Id, ct);
+        return new GetInvoiceResponse
+        {
+            InvoiceId = invoice?.Id,
+            Found = invoice != null
+        };
+    }
+}
+```
+
+## CancellationToken Wiring
+
+**This is the #1 source of migration bugs.** Every async operation must receive and respect the cancellation token.
+
+### Checklist
+
+For each migrated handler, verify:
+
+- [ ] Handler accepts CancellationToken parameter (automatic with IStellaEndpoint)
+- [ ] Token passed to all database calls
+- [ ] Token passed to all HTTP client calls
+- [ ] Token passed to all file I/O operations
+- [ ] Long-running loops check `ct.IsCancellationRequested`
+- [ ] Token passed to `Task.Delay`, `WaitAsync`, etc.
+
+### Example: Before (missing tokens)
+
+```csharp
+public async Task<Invoice> CreateAsync(CreateInvoiceRequest request)
+{
+    var invoice = new Invoice(request);
+    await _db.Invoices.AddAsync(invoice);  // Missing token!
+    await _db.SaveChangesAsync();          // Missing token!
+    await _notifier.SendAsync(invoice);    // Missing token!
+    return invoice;
+}
+```
+
+### Example: After (proper wiring)
+
+```csharp
+public async Task<Invoice> CreateAsync(CreateInvoiceRequest request, CancellationToken ct)
+{
+    ct.ThrowIfCancellationRequested();
+
+    var invoice = new Invoice(request);
+    await _db.Invoices.AddAsync(invoice, ct);
+    await _db.SaveChangesAsync(ct);
+    await _notifier.SendAsync(invoice, ct);
+    return invoice;
+}
+```
+
+## Streaming Migration
+
+### File Upload: Before
+
+```csharp
+[HttpPost("upload")]
+public async Task<IActionResult> Upload(IFormFile file)
+{
+    using var stream = file.OpenReadStream();
+    await _storage.SaveAsync(stream);
+    return Ok();
+}
+```
+
+### File Upload: After
+
+```csharp
+[StellaEndpoint("POST", "/upload", SupportsStreaming = true)]
+public sealed class UploadEndpoint : IRawStellaEndpoint
+{
+    private readonly IStorageService _storage;
+
+    public UploadEndpoint(IStorageService storage) => _storage = storage;
+
+    public async Task<RawResponse> HandleAsync(RawRequestContext ctx, CancellationToken ct)
+    {
+        // ctx.Body is already a stream - no buffering needed
+        var path = await _storage.SaveAsync(ctx.Body, ct);
+        return RawResponse.Ok($"{{\"path\":\"{path}\"}}");
+    }
+}
+```
+
+### File Download: Before
+
+```csharp
+[HttpGet("download/{id}")]
+public async Task<IActionResult> Download(string id)
+{
+    var stream = await _storage.GetAsync(id);
+    return File(stream, "application/octet-stream");
+}
+```
+
+### File Download: After
+
+```csharp
+[StellaEndpoint("GET", "/download/{id}", SupportsStreaming = true)]
+public sealed class DownloadEndpoint : IRawStellaEndpoint
+{
+    private readonly IStorageService _storage;
+
+    public DownloadEndpoint(IStorageService storage) => _storage = storage;
+
+    public async Task<RawResponse> HandleAsync(RawRequestContext ctx, CancellationToken ct)
+    {
+        var id = ctx.PathParameters["id"];
+        var stream = await _storage.GetAsync(id, ct);
+        return RawResponse.Stream(stream, "application/octet-stream");
+    }
+}
+```
+
+## Authorization Migration
+
+### Before: [Authorize] Attribute
+
+```csharp
+[Authorize(Roles = "admin,billing-manager")]
+public async Task<IActionResult> Delete(string id) { ... }
+```
+
+### After: RequiredClaims
+
+```csharp
+[StellaEndpoint("DELETE", "/invoices/{id}", RequiredClaims = ["invoices:delete"])]
+public sealed class DeleteInvoiceEndpoint : IStellaEndpoint<...> { ... }
+```
+
+Claims are configured in Authority and enforced by the Gateway's AuthorizationMiddleware.
+
+## Migration Checklist Template
+
+Use this checklist for each service migration:
+
+```markdown
+# Migration Checklist: [ServiceName]
+
+## Inventory
+- [ ] List all HTTP routes (Method + Path)
+- [ ] Identify streaming endpoints
+- [ ] Identify authorization requirements
+- [ ] Document external dependencies
+
+## Preparation
+- [ ] Add StellaOps.Microservice package
+- [ ] Add StellaOps.Router.Transport.* package(s)
+- [ ] Configure router connection in Program.cs
+- [ ] Set up local gateway for testing
+
+## Per-Route Migration
+For each route:
+- [ ] Create [StellaEndpoint] handler class
+- [ ] Define request/response record types
+- [ ] Map path parameters
+- [ ] Wire CancellationToken throughout
+- [ ] Convert to IRawStellaEndpoint if streaming
+- [ ] Add RequiredClaims
+- [ ] Write unit tests
+- [ ] Write integration tests
+
+## Cutover
+- [ ] Deploy alongside existing WebService
+- [ ] Verify via router routing
+- [ ] Shift percentage of traffic
+- [ ] Monitor for errors
+- [ ] Full cutover
+- [ ] Remove WebService HTTP listeners
+
+## Cleanup
+- [ ] Remove unused controller code
+- [ ] Remove HTTP pipeline configuration
+- [ ] Update OpenAPI documentation
+- [ ] Update client SDKs
+```
+
+## Service Inventory
+
+| Module | WebService Project | Priority | Complexity | Notes |
+|--------|-------------------|----------|------------|-------|
+| Gateway | StellaOps.Gateway.WebService | N/A | N/A | IS the router |
+| Concelier | StellaOps.Concelier.WebService | High | Medium | Advisory ingestion |
+| Scanner | StellaOps.Scanner.WebService | High | High | Streaming scans |
+| Attestor | StellaOps.Attestor.WebService | Medium | Medium | Attestation gen |
+| Excititor | StellaOps.Excititor.WebService | Medium | Low | VEX processing |
+| Orchestrator | StellaOps.Orchestrator.WebService | Medium | Medium | Job coordination |
+| Scheduler | StellaOps.Scheduler.WebService | Low | Low | Job scheduling |
+| Notify | StellaOps.Notify.WebService | Low | Low | Notifications |
+| Notifier | StellaOps.Notifier.WebService | Low | Low | Alert dispatch |
+| Signer | StellaOps.Signer.WebService | Medium | Low | Crypto signing |
+| Findings | StellaOps.Findings.Ledger.WebService | Medium | Medium | Results storage |
+| EvidenceLocker | StellaOps.EvidenceLocker.WebService | Low | Medium | Blob storage |
+| ExportCenter | StellaOps.ExportCenter.WebService | Low | Medium | Report generation |
+| IssuerDirectory | StellaOps.IssuerDirectory.WebService | Low | Low | Issuer lookup |
+| PacksRegistry | StellaOps.PacksRegistry.WebService | Low | Low | Pack management |
+| RiskEngine | StellaOps.RiskEngine.WebService | Medium | Medium | Risk calculation |
+| TaskRunner | StellaOps.TaskRunner.WebService | Low | Medium | Task execution |
+| TimelineIndexer | StellaOps.TimelineIndexer.WebService | Low | Low | Event indexing |
+| AdvisoryAI | StellaOps.AdvisoryAI.WebService | Low | Medium | AI assistance |
+
+## Testing During Migration
+
+### Unit Tests
+
+Test handlers in isolation using mocked dependencies:
+
+```csharp
+[Fact]
+public async Task CreateInvoice_ValidRequest_ReturnsInvoiceId()
+{
+    // Arrange
+    var mockService = new Mock<IInvoiceService>();
+    mockService.Setup(s => s.CreateAsync(It.IsAny<CreateInvoiceRequest>(), It.IsAny<CancellationToken>()))
+        .ReturnsAsync(new Invoice { Id = "INV-123" });
+
+    var endpoint = new CreateInvoiceEndpoint(mockService.Object);
+
+    // Act
+    var response = await endpoint.HandleAsync(
+        new CreateInvoiceRequest { Amount = 100 },
+        CancellationToken.None);
+
+    // Assert
+    response.InvoiceId.Should().Be("INV-123");
+}
+```
+
+### Integration Tests
+
+Use WebApplicationFactory for the Gateway and actual microservice instances:
+
+```csharp
+public sealed class InvoiceTests : IClassFixture<GatewayFixture>
+{
+    private readonly GatewayFixture _fixture;
+
+    [Fact]
+    public async Task CreateAndGetInvoice_WorksEndToEnd()
+    {
+        var createResponse = await _fixture.Client.PostAsJsonAsync("/api/invoices",
+            new { Amount = 100 });
+        createResponse.StatusCode.Should().Be(HttpStatusCode.OK);
+
+        var created = await createResponse.Content.ReadFromJsonAsync<CreateInvoiceResponse>();
+
+        var getResponse = await _fixture.Client.GetAsync($"/api/invoices/{created.InvoiceId}");
+        getResponse.StatusCode.Should().Be(HttpStatusCode.OK);
+    }
+}
+```
+
+## Common Migration Issues
+
+### 1. Missing CancellationToken Propagation
+
+**Symptom:** Requests continue processing after client disconnects.
+
+**Fix:** Pass `CancellationToken` to all async operations.
+
+### 2. IFormFile Not Available
+
+**Symptom:** Compilation error on `IFormFile` parameter.
+
+**Fix:** Convert to `IRawStellaEndpoint` for streaming.
+
+### 3. HttpContext Not Available
+
+**Symptom:** Code references `HttpContext` for headers, claims.
+
+**Fix:** Use `RawRequestContext` for raw endpoints, or inject claims via Authority.
+
+### 4. Return Type Mismatch
+
+**Symptom:** Handler returns `IActionResult`.
+
+**Fix:** Define proper response record type, return that instead.
+
+### 5. Route Parameter Not Extracted
+
+**Symptom:** Path parameters like `{id}` not populated.
+
+**Fix:** For `IStellaEndpoint`, add property to request type. For `IRawStellaEndpoint`, use `ctx.PathParameters["id"]`.
+
+## Next Steps
+
+1. Choose a low-risk service for pilot migration (Scheduler recommended)
+2. Follow the Migration Checklist
+3. Document lessons learned
+4. Proceed with higher-priority services
+5. Eventually merge all to use router exclusively
+
+---
+
+## See Also
+
+- [Router Architecture](architecture.md) - System specification
+- [Schema Validation](schema-validation.md) - JSON Schema validation
+- [OpenAPI Aggregation](openapi-aggregation.md) - OpenAPI document generation

docs/modules/router/openapi-aggregation.md

@@ -0,0 +1,503 @@
+# OpenAPI Aggregation
+
+This document describes how the StellaOps Gateway aggregates OpenAPI documentation from connected microservices into a unified specification.
+
+## Overview
+
+The Gateway automatically generates a single OpenAPI 3.1.0 document that aggregates all endpoints from connected microservices. This provides:
+
+- **Unified API documentation**: All services documented in one place
+- **Dynamic updates**: Document regenerates when services connect/disconnect
+- **Standard compliance**: OpenAPI 3.1.0 with native JSON Schema draft 2020-12 support
+- **Multiple formats**: Available as JSON or YAML
+- **Efficient caching**: ETag-based caching with configurable TTL
+
+### How It Works
+
+```
+┌──────────────┐    HELLO     ┌──────────────┐    GET /openapi.json    ┌──────────────┐
+│  Billing     │ ──────────►  │              │  ◄─────────────────────  │   Client     │
+│  Service     │   + schemas  │   Gateway    │                          │              │
+└──────────────┘              │              │    OpenAPI 3.1.0         │              │
+                              │              │  ─────────────────────►  │              │
+┌──────────────┐    HELLO     │              │    unified document      └──────────────┘
+│  Inventory   │ ──────────►  │              │
+│  Service     │   + schemas  └──────────────┘
+└──────────────┘
+```
+
+1. Microservices send schemas and endpoint metadata via HELLO payload
+2. Gateway stores this information in routing state
+3. OpenAPI generator aggregates all connected services
+4. Document is cached and served via HTTP endpoints
+
+---
+
+## Configuration
+
+### OpenApiAggregationOptions
+
+Configure OpenAPI aggregation in your Gateway configuration:
+
+```yaml
+# router.yaml or appsettings.yaml
+OpenApi:
+  Title: "My API Gateway"
+  Description: "Unified API for all microservices"
+  Version: "2.0.0"
+  ServerUrl: "https://api.example.com"
+  CacheTtlSeconds: 60
+  Enabled: true
+  LicenseName: "AGPL-3.0-or-later"
+  ContactName: "API Team"
+  ContactEmail: "api@example.com"
+  TokenUrl: "/auth/token"
+```
+
+### Configuration Reference
+
+| Property | Type | Default | Description |
+|----------|------|---------|-------------|
+| `Title` | `string` | `"StellaOps Gateway API"` | API title in OpenAPI info section |
+| `Description` | `string` | `"Unified API aggregating all connected microservices."` | API description |
+| `Version` | `string` | `"1.0.0"` | API version number |
+| `ServerUrl` | `string` | `"/"` | Base server URL |
+| `CacheTtlSeconds` | `int` | `60` | Cache time-to-live in seconds |
+| `Enabled` | `bool` | `true` | Enable/disable OpenAPI aggregation |
+| `LicenseName` | `string` | `"AGPL-3.0-or-later"` | License name in OpenAPI info |
+| `ContactName` | `string?` | `null` | Contact name (optional) |
+| `ContactEmail` | `string?` | `null` | Contact email (optional) |
+| `TokenUrl` | `string` | `"/auth/token"` | OAuth2 token endpoint URL |
+
+### Disabling OpenAPI
+
+To disable OpenAPI aggregation entirely:
+
+```yaml
+OpenApi:
+  Enabled: false
+```
+
+---
+
+## Endpoints
+
+### Discovery Endpoint
+
+```http
+GET /.well-known/openapi
+```
+
+Returns metadata about the OpenAPI document:
+
+**Response:**
+```json
+{
+  "openapi_json": "/openapi.json",
+  "openapi_yaml": "/openapi.yaml",
+  "etag": "\"5d41402abc4b2a76b9719d911017c592\"",
+  "generated_at": "2025-01-15T10:30:00.0000000Z"
+}
+```
+
+### OpenAPI JSON
+
+```http
+GET /openapi.json
+```
+
+Returns the full OpenAPI 3.1.0 specification in JSON format.
+
+**Headers:**
+- `Cache-Control: public, max-age=60`
+- `ETag: "<content-hash>"`
+- `Content-Type: application/json; charset=utf-8`
+
+**Conditional Request:**
+```http
+GET /openapi.json
+If-None-Match: "5d41402abc4b2a76b9719d911017c592"
+```
+
+Returns `304 Not Modified` if content unchanged.
+
+### OpenAPI YAML
+
+```http
+GET /openapi.yaml
+```
+
+Returns the full OpenAPI 3.1.0 specification in YAML format.
+
+**Headers:**
+- `Cache-Control: public, max-age=60`
+- `ETag: "<content-hash>"`
+- `Content-Type: application/yaml; charset=utf-8`
+
+---
+
+## Security Mapping
+
+The Gateway automatically maps claim requirements to OpenAPI security schemes.
+
+### Claim to Scope Mapping
+
+When endpoints define `RequiringClaims`, these are converted to OAuth2 scopes:
+
+```csharp
+// Endpoint with claim requirements
+[StellaEndpoint("POST", "/invoices")]
+[RequireClaim("billing:write")]
+public sealed class CreateInvoiceEndpoint : IStellaEndpoint<...>
+```
+
+Becomes in OpenAPI:
+
+```json
+{
+  "paths": {
+    "/invoices": {
+      "post": {
+        "security": [
+          {
+            "BearerAuth": [],
+            "OAuth2": ["billing:write"]
+          }
+        ]
+      }
+    }
+  }
+}
+```
+
+### Security Schemes
+
+The Gateway generates two security schemes:
+
+#### BearerAuth
+
+HTTP Bearer token authentication (always present):
+
+```json
+{
+  "BearerAuth": {
+    "type": "http",
+    "scheme": "bearer",
+    "bearerFormat": "JWT",
+    "description": "JWT Bearer token authentication"
+  }
+}
+```
+
+#### OAuth2
+
+Client credentials flow with collected scopes (only if endpoints have claims):
+
+```json
+{
+  "OAuth2": {
+    "type": "oauth2",
+    "flows": {
+      "clientCredentials": {
+        "tokenUrl": "/auth/token",
+        "scopes": {
+          "billing:write": "Access scope: billing:write",
+          "billing:read": "Access scope: billing:read",
+          "inventory:read": "Access scope: inventory:read"
+        }
+      }
+    }
+  }
+}
+```
+
+### Scope Collection
+
+Scopes are automatically collected from all connected services. If multiple endpoints require the same claim, it appears only once in the scopes list.
+
+---
+
+## Generated Document Structure
+
+The aggregated OpenAPI document follows this structure:
+
+```json
+{
+  "openapi": "3.1.0",
+  "info": {
+    "title": "StellaOps Gateway API",
+    "version": "1.0.0",
+    "description": "Unified API aggregating all connected microservices.",
+    "license": {
+      "name": "AGPL-3.0-or-later"
+    },
+    "contact": {
+      "name": "API Team",
+      "email": "api@example.com"
+    }
+  },
+  "servers": [
+    {
+      "url": "/"
+    }
+  ],
+  "paths": {
+    "/invoices": {
+      "post": {
+        "operationId": "billing_invoices_POST",
+        "tags": ["billing"],
+        "summary": "Create invoice",
+        "description": "Creates a new draft invoice",
+        "security": [
+          {
+            "BearerAuth": [],
+            "OAuth2": ["billing:write"]
+          }
+        ],
+        "requestBody": {
+          "required": true,
+          "content": {
+            "application/json": {
+              "schema": {
+                "$ref": "#/components/schemas/billing_CreateInvoiceRequest"
+              }
+            }
+          }
+        },
+        "responses": {
+          "200": {
+            "description": "Success",
+            "content": {
+              "application/json": {
+                "schema": {
+                  "$ref": "#/components/schemas/billing_CreateInvoiceResponse"
+                }
+              }
+            }
+          },
+          "400": { "description": "Bad Request" },
+          "401": { "description": "Unauthorized" },
+          "404": { "description": "Not Found" },
+          "422": { "description": "Validation Error" },
+          "500": { "description": "Internal Server Error" }
+        }
+      }
+    },
+    "/items": {
+      "get": {
+        "operationId": "inventory_items_GET",
+        "tags": ["inventory"],
+        "summary": "List items",
+        "responses": {
+          "200": { "description": "Success" }
+        }
+      }
+    }
+  },
+  "components": {
+    "schemas": {
+      "billing_CreateInvoiceRequest": {
+        "type": "object",
+        "required": ["customerId", "amount"],
+        "properties": {
+          "customerId": { "type": "string" },
+          "amount": { "type": "number" },
+          "description": { "type": ["string", "null"] },
+          "lineItems": {
+            "type": "array",
+            "items": { "$ref": "#/components/schemas/billing_LineItem" }
+          }
+        }
+      },
+      "billing_CreateInvoiceResponse": {
+        "type": "object",
+        "required": ["invoiceId", "createdAt", "status"],
+        "properties": {
+          "invoiceId": { "type": "string" },
+          "createdAt": { "type": "string", "format": "date-time" },
+          "status": { "type": "string" }
+        }
+      },
+      "billing_LineItem": {
+        "type": "object",
+        "required": ["description", "amount"],
+        "properties": {
+          "description": { "type": "string" },
+          "amount": { "type": "number" },
+          "quantity": { "type": "integer", "default": 1 }
+        }
+      }
+    },
+    "securitySchemes": {
+      "BearerAuth": {
+        "type": "http",
+        "scheme": "bearer",
+        "bearerFormat": "JWT",
+        "description": "JWT Bearer token authentication"
+      },
+      "OAuth2": {
+        "type": "oauth2",
+        "flows": {
+          "clientCredentials": {
+            "tokenUrl": "/auth/token",
+            "scopes": {
+              "billing:write": "Access scope: billing:write"
+            }
+          }
+        }
+      }
+    }
+  },
+  "tags": [
+    {
+      "name": "billing",
+      "description": "billing microservice (v1.0.0)"
+    },
+    {
+      "name": "inventory",
+      "description": "inventory microservice (v2.0.0)"
+    }
+  ]
+}
+```
+
+### Schema Prefixing
+
+Schemas are prefixed with the service name to prevent naming conflicts:
+
+| Service | Original Type | Prefixed Schema ID |
+|---------|--------------|-------------------|
+| `billing` | `CreateInvoiceRequest` | `billing_CreateInvoiceRequest` |
+| `inventory` | `GetItemResponse` | `inventory_GetItemResponse` |
+
+### Tag Generation
+
+Tags are automatically generated from connected services:
+
+- Tag name: Service name (lowercase)
+- Tag description: Service description from `OpenApiInfo` or auto-generated
+
+### Operation IDs
+
+Operation IDs follow the pattern: `{serviceName}_{path}_{method}`
+
+Example: `billing_invoices_POST`
+
+---
+
+## Cache Behavior
+
+### TTL-Based Expiration
+
+The document cache expires based on `CacheTtlSeconds` (default: 60 seconds):
+
+```yaml
+OpenApi:
+  CacheTtlSeconds: 30  # More frequent regeneration
+```
+
+Setting `CacheTtlSeconds: 0` regenerates the document on every request (not recommended for production).
+
+### Connection-Based Invalidation
+
+The cache is automatically invalidated when:
+
+1. A new microservice connects (HELLO received)
+2. A microservice disconnects (connection closed)
+
+This ensures the OpenAPI document always reflects currently connected services.
+
+### ETag Consistency
+
+The ETag is computed from the document content hash (SHA256). This ensures:
+
+- Same content = same ETag
+- Content changes = new ETag
+- Clients can use conditional requests to avoid re-downloading unchanged documents
+
+### Recommended Client Strategy
+
+```javascript
+// Store ETag from previous response
+let cachedETag = localStorage.getItem('openapi-etag');
+
+const response = await fetch('/openapi.json', {
+  headers: cachedETag ? { 'If-None-Match': cachedETag } : {}
+});
+
+if (response.status === 304) {
+  // Use cached document
+  return getCachedDocument();
+}
+
+// Store new ETag and document
+localStorage.setItem('openapi-etag', response.headers.get('ETag'));
+const document = await response.json();
+cacheDocument(document);
+return document;
+```
+
+---
+
+## Service Registration
+
+### Microservice Options
+
+Configure service metadata that appears in OpenAPI:
+
+```csharp
+services.AddStellaMicroservice(options =>
+{
+    options.ServiceName = "billing";
+    options.ServiceDescription = "Invoice and payment processing service";
+    options.ContactInfo = "billing-team@example.com";
+});
+```
+
+### Service OpenAPI Info
+
+The `ServiceOpenApiInfo` is sent in the HELLO payload:
+
+```json
+{
+  "instance": { ... },
+  "endpoints": [ ... ],
+  "schemas": { ... },
+  "openApiInfo": {
+    "title": "billing",
+    "description": "Invoice and payment processing service"
+  }
+}
+```
+
+This description appears in the tag entry for the service.
+
+---
+
+## Troubleshooting
+
+### Document Not Updating
+
+1. Check `CacheTtlSeconds` - may need to wait for TTL expiration
+2. Verify service connected successfully (check Gateway logs)
+3. Force refresh by restarting the Gateway
+
+### Missing Schemas
+
+1. Ensure `[ValidateSchema]` attribute is applied to endpoints
+2. Check for schema parsing errors in Gateway logs
+3. Verify endpoint implements `IStellaEndpoint<TRequest, TResponse>`
+
+### Security Schemes Not Appearing
+
+1. OAuth2 scheme only appears if endpoints have claim requirements
+2. Check `RequiringClaims` is populated on endpoint descriptors
+3. Verify claim types are being transmitted correctly
+
+---
+
+## See Also
+
+- [Schema Validation](schema-validation.md) - JSON Schema validation reference
+- [API Overview](../../api/overview.md) - General API conventions
+- [Gateway OpenAPI](../gateway/openapi.md) - Gateway OpenAPI implementation details

docs/modules/router/schema-validation.md

@@ -0,0 +1,426 @@
+# JSON Schema Validation
+
+This document describes the JSON Schema validation feature in the StellaOps Router/Microservice SDK.
+
+## Overview
+
+The StellaOps Microservice SDK provides compile-time JSON Schema generation and runtime request/response validation. Schemas are automatically generated from your C# types using a source generator, then transmitted to the Gateway via the HELLO payload where they power both runtime validation and OpenAPI documentation.
+
+### Key Features
+
+- **Compile-time schema generation**: JSON Schema draft 2020-12 generated from C# types
+- **Runtime validation**: Request bodies validated against schema before reaching handlers
+- **OpenAPI 3.1.0 compatibility**: Native JSON Schema support in OpenAPI 3.1.0
+- **Automatic documentation**: Schemas flow to Gateway for unified OpenAPI documentation
+- **External schema support**: Override generated schemas with embedded resource files
+
+### Benefits
+
+| Benefit | Description |
+|---------|-------------|
+| Type safety | Contract enforcement between clients and services |
+| Early error detection | Invalid requests rejected with 422 before handler execution |
+| Documentation automation | No manual schema maintenance required |
+| Interoperability | Standard JSON Schema works with any tooling |
+
+---
+
+## Quick Start
+
+### 1. Add the ValidateSchema Attribute
+
+```csharp
+using StellaOps.Microservice;
+
+[StellaEndpoint("POST", "/invoices")]
+[ValidateSchema]
+public sealed class CreateInvoiceEndpoint : IStellaEndpoint<CreateInvoiceRequest, CreateInvoiceResponse>
+{
+    public Task<CreateInvoiceResponse> HandleAsync(
+        CreateInvoiceRequest request,
+        CancellationToken cancellationToken)
+    {
+        // Request is already validated against JSON Schema
+        return Task.FromResult(new CreateInvoiceResponse
+        {
+            InvoiceId = Guid.NewGuid().ToString(),
+            CreatedAt = DateTime.UtcNow,
+            Status = "draft"
+        });
+    }
+}
+```
+
+### 2. Define Your Request/Response Types
+
+```csharp
+public sealed record CreateInvoiceRequest
+{
+    public required string CustomerId { get; init; }
+    public required decimal Amount { get; init; }
+    public string? Description { get; init; }
+    public List<LineItem> LineItems { get; init; } = [];
+}
+
+public sealed record CreateInvoiceResponse
+{
+    public required string InvoiceId { get; init; }
+    public required DateTime CreatedAt { get; init; }
+    public required string Status { get; init; }
+}
+```
+
+### 3. Build Your Project
+
+The source generator automatically creates JSON Schema definitions at compile time. These schemas are included in the HELLO payload when your microservice connects to the Gateway.
+
+---
+
+## Attribute Reference
+
+### ValidateSchemaAttribute
+
+Enables JSON Schema validation for an endpoint.
+
+```csharp
+[AttributeUsage(AttributeTargets.Class, AllowMultiple = false, Inherited = false)]
+public sealed class ValidateSchemaAttribute : Attribute
+```
+
+### Properties
+
+| Property | Type | Default | Description |
+|----------|------|---------|-------------|
+| `ValidateRequest` | `bool` | `true` | Enable request body validation |
+| `ValidateResponse` | `bool` | `false` | Enable response body validation |
+| `RequestSchemaResource` | `string?` | `null` | Embedded resource path to external request schema |
+| `ResponseSchemaResource` | `string?` | `null` | Embedded resource path to external response schema |
+| `Summary` | `string?` | `null` | OpenAPI operation summary |
+| `Description` | `string?` | `null` | OpenAPI operation description |
+| `Tags` | `string[]?` | `null` | OpenAPI tags for grouping endpoints |
+| `Deprecated` | `bool` | `false` | Mark endpoint as deprecated in OpenAPI |
+
+### Validation Properties
+
+#### ValidateRequest (default: true)
+
+Controls whether incoming request bodies are validated against the generated schema.
+
+```csharp
+// Request validation enabled (default)
+[ValidateSchema(ValidateRequest = true)]
+
+// Disable request validation
+[ValidateSchema(ValidateRequest = false)]
+```
+
+#### ValidateResponse (default: false)
+
+Enables response body validation. Useful for debugging or strict contract enforcement, but adds overhead.
+
+```csharp
+// Enable response validation
+[ValidateSchema(ValidateResponse = true)]
+```
+
+#### External Schema Files
+
+Override generated schemas with embedded resource files when you need custom schema definitions:
+
+```csharp
+[ValidateSchema(RequestSchemaResource = "Schemas.create-order.json")]
+public sealed class CreateOrderEndpoint : IStellaEndpoint<CreateOrderRequest, CreateOrderResponse>
+```
+
+The schema file must be embedded as a resource in your assembly.
+
+### Documentation Properties
+
+#### Summary and Description
+
+Provide OpenAPI documentation for the operation:
+
+```csharp
+[ValidateSchema(
+    Summary = "Create a new invoice",
+    Description = "Creates a draft invoice for the specified customer. The invoice must be finalized before it can be sent.")]
+public sealed class CreateInvoiceEndpoint : IStellaEndpoint<CreateInvoiceRequest, CreateInvoiceResponse>
+```
+
+#### Tags
+
+Override the default service-based tag grouping:
+
+```csharp
+[ValidateSchema(Tags = ["Billing", "Invoices"])]
+public sealed class CreateInvoiceEndpoint : IStellaEndpoint<CreateInvoiceRequest, CreateInvoiceResponse>
+```
+
+#### Deprecated
+
+Mark an endpoint as deprecated in OpenAPI documentation:
+
+```csharp
+[ValidateSchema(Deprecated = true, Description = "Use /v2/invoices instead")]
+public sealed class CreateInvoiceV1Endpoint : IStellaEndpoint<CreateInvoiceRequest, CreateInvoiceResponse>
+```
+
+---
+
+## Schema Discovery Endpoints
+
+The Gateway exposes endpoints to discover and retrieve schemas from connected microservices.
+
+### Discovery Endpoint
+
+```http
+GET /.well-known/openapi
+```
+
+Returns metadata about the OpenAPI document including available format URLs:
+
+```json
+{
+  "openapi_json": "/openapi.json",
+  "openapi_yaml": "/openapi.yaml",
+  "etag": "\"a1b2c3d4\"",
+  "generated_at": "2025-01-15T10:30:00.000Z"
+}
+```
+
+### OpenAPI Document (JSON)
+
+```http
+GET /openapi.json
+Accept: application/json
+```
+
+Returns the full OpenAPI 3.1.0 specification in JSON format. Supports ETag-based caching:
+
+```http
+GET /openapi.json
+If-None-Match: "a1b2c3d4"
+```
+
+Returns `304 Not Modified` if the document hasn't changed.
+
+### OpenAPI Document (YAML)
+
+```http
+GET /openapi.yaml
+Accept: application/yaml
+```
+
+Returns the full OpenAPI 3.1.0 specification in YAML format.
+
+### Caching Behavior
+
+All OpenAPI endpoints support HTTP caching:
+
+| Header | Value | Description |
+|--------|-------|-------------|
+| `Cache-Control` | `public, max-age=60` | Client-side caching for 60 seconds |
+| `ETag` | `"<hash>"` | Content hash for conditional requests |
+
+---
+
+## Examples
+
+### Basic Endpoint with Validation
+
+```csharp
+[StellaEndpoint("POST", "/invoices")]
+[ValidateSchema]
+public sealed class CreateInvoiceEndpoint : IStellaEndpoint<CreateInvoiceRequest, CreateInvoiceResponse>
+{
+    private readonly ILogger<CreateInvoiceEndpoint> _logger;
+
+    public CreateInvoiceEndpoint(ILogger<CreateInvoiceEndpoint> logger)
+    {
+        _logger = logger;
+    }
+
+    public Task<CreateInvoiceResponse> HandleAsync(
+        CreateInvoiceRequest request,
+        CancellationToken cancellationToken)
+    {
+        _logger.LogInformation(
+            "Creating invoice for customer {CustomerId} with amount {Amount}",
+            request.CustomerId,
+            request.Amount);
+
+        return Task.FromResult(new CreateInvoiceResponse
+        {
+            InvoiceId = $"INV-{Guid.NewGuid():N}"[..16].ToUpperInvariant(),
+            CreatedAt = DateTime.UtcNow,
+            Status = "draft"
+        });
+    }
+}
+```
+
+### Endpoint with Full Documentation
+
+```csharp
+[StellaEndpoint("POST", "/invoices", TimeoutSeconds = 30)]
+[ValidateSchema(
+    Summary = "Create invoice",
+    Description = "Creates a new draft invoice for the specified customer. Line items are optional but recommended for itemized billing.",
+    Tags = ["Billing", "Invoices"])]
+public sealed class CreateInvoiceEndpoint : IStellaEndpoint<CreateInvoiceRequest, CreateInvoiceResponse>
+{
+    // Implementation...
+}
+```
+
+### Deprecated Endpoint
+
+```csharp
+[StellaEndpoint("POST", "/v1/invoices")]
+[ValidateSchema(
+    Deprecated = true,
+    Summary = "Create invoice (deprecated)",
+    Description = "This endpoint is deprecated. Use POST /v2/invoices instead.")]
+public sealed class CreateInvoiceV1Endpoint : IStellaEndpoint<CreateInvoiceRequest, CreateInvoiceResponse>
+{
+    // Implementation...
+}
+```
+
+### Request with Complex Types
+
+```csharp
+public sealed record CreateInvoiceRequest
+{
+    /// <summary>
+    /// The customer identifier.
+    /// </summary>
+    public required string CustomerId { get; init; }
+
+    /// <summary>
+    /// The invoice amount in the default currency.
+    /// </summary>
+    public required decimal Amount { get; init; }
+
+    /// <summary>
+    /// Optional description for the invoice.
+    /// </summary>
+    public string? Description { get; init; }
+
+    /// <summary>
+    /// Line items for itemized billing.
+    /// </summary>
+    public List<LineItem> LineItems { get; init; } = [];
+}
+
+public sealed record LineItem
+{
+    public required string Description { get; init; }
+    public required decimal Amount { get; init; }
+    public int Quantity { get; init; } = 1;
+}
+```
+
+The source generator produces JSON Schema that includes:
+- Required property validation (`required` keyword)
+- Type validation (`type` keyword)
+- Nullable property handling (`null` in type union)
+- Nested object schemas
+
+---
+
+## Architecture
+
+### Schema Flow Diagram
+
+```
+┌─────────────────────────────────────────────────────────────────────┐
+│                        COMPILE TIME                                  │
+├─────────────────────────────────────────────────────────────────────┤
+│                                                                      │
+│  C# Types              Source Generator         Generated Code       │
+│  ─────────             ────────────────         ──────────────       │
+│  CreateInvoice    ──►  Analyzes types      ──►  JSON Schema defs    │
+│  Request               Extracts metadata        GetSchemaDefinitions│
+│  CreateInvoice         Generates schemas        EndpointDescriptor  │
+│  Response                                       with SchemaInfo     │
+│                                                                      │
+└─────────────────────────────────────────────────────────────────────┘
+                                │
+                                ▼
+┌─────────────────────────────────────────────────────────────────────┐
+│                         RUNTIME                                      │
+├─────────────────────────────────────────────────────────────────────┤
+│                                                                      │
+│  Microservice Start    HELLO Payload            Gateway Storage      │
+│  ─────────────────     ─────────────            ───────────────      │
+│  RouterConnection  ──► Instance info        ──► ConnectionState      │
+│  Manager               Endpoints[]              Schemas dictionary   │
+│                        Schemas{}                OpenApiInfo          │
+│                        OpenApiInfo                                   │
+│                                                                      │
+└─────────────────────────────────────────────────────────────────────┘
+                                │
+                                ▼
+┌─────────────────────────────────────────────────────────────────────┐
+│                      HTTP EXPOSURE                                   │
+├─────────────────────────────────────────────────────────────────────┤
+│                                                                      │
+│  OpenApiDocument       Document Cache           HTTP Endpoints       │
+│  Generator             ─────────────            ──────────────       │
+│  ──────────────                                                      │
+│  Aggregates all    ──► TTL-based cache     ──► GET /openapi.json    │
+│  connected services    ETag generation          GET /openapi.yaml   │
+│  Prefixes schemas      Invalidation on          GET /.well-known/   │
+│  by service name       connection change            openapi         │
+│                                                                      │
+└─────────────────────────────────────────────────────────────────────┘
+```
+
+### Schema Naming Convention
+
+Schemas are prefixed with the service name to avoid conflicts:
+
+- Service: `Billing`
+- Type: `CreateInvoiceRequest`
+- Schema ID: `Billing_CreateInvoiceRequest`
+
+This allows multiple services to define types with the same name without collisions.
+
+---
+
+## Error Handling
+
+### Validation Errors
+
+When request validation fails, the endpoint returns a `422 Unprocessable Entity` response with details:
+
+```json
+{
+  "type": "https://tools.ietf.org/html/rfc4918#section-11.2",
+  "title": "Validation Error",
+  "status": 422,
+  "errors": [
+    {
+      "path": "$.customerId",
+      "message": "Required property 'customerId' is missing"
+    },
+    {
+      "path": "$.amount",
+      "message": "Value must be a number"
+    }
+  ]
+}
+```
+
+### Invalid Schemas
+
+If a schema cannot be parsed (e.g., malformed JSON in external schema file), the schema is skipped and a warning is logged. The endpoint will still function but without schema validation.
+
+---
+
+## See Also
+
+- [OpenAPI Aggregation](openapi-aggregation.md) - How schemas become OpenAPI documentation
+- [API Overview](../../api/overview.md) - General API conventions
+- [Router Architecture](architecture.md) - Router system overview