Middleware

Argus MCP processes every MCP request through a composable middleware chain. Each middleware wraps the next, forming an onion-style pipeline that handles cross-cutting concerns -- authentication, authorization, telemetry, audit logging, and error recovery -- without coupling them to business logic.

Pipeline at a Glance

     Client Request
           |
           v
+----------------------+
|  AuthMiddleware      |  <-- Validates tokens, injects UserIdentity
+----------------------+
|  AuthzMiddleware     |  <-- RBAC policy evaluation
+----------------------+
|  TelemetryMiddleware |  <-- OTel spans + metrics
+----------------------+
|  AuditMiddleware     |  <-- Structured audit logging (NIST SP 800-53)
+----------------------+
|  RecoveryMiddleware  |  <-- Exception safety net
+----------------------+
|  RoutingMiddleware   |  <-- Resolve capability -> backend, forward
+----------------------+
           |
           v
    Backend MCP Server

Execution order is outermost-first for requests, innermost-first for responses. The first middleware in the list wraps all others.

Sections

• Overview -- Pipeline architecture, request context, chain construction, and writing custom middleware
• Built-in Plugins -- Reference for all built-in middleware: Auth, Authz, Telemetry, Audit, Recovery, and Routing