Summary

Add an <HttpServer> algebraic effect that allows Vera programs to handle incoming HTTP requests with verified contracts.

Design

Vera's algebraic effect system maps naturally to HTTP server patterns. An incoming request is an effect operation; the handler provides the routing and response logic:

effect HttpServer {
  op on_request(HttpRequest -> HttpResponse);
}

handle[HttpServer] {
  on_request(@HttpRequest) -> {
    // route, process, build response
    resume(response)
  }
} in {
  serve(8080)
}

Contracts on handler operations can verify:

• Response status codes match expected patterns
• Required headers are present
• Response body conforms to a schema

Dependencies

• Network access effect (<Http>) #57 — HTTP client (shared HttpRequest/HttpResponse types)
• WASI 0.2 compliance #237 — WASI 0.2 compliance (wasi:http/incoming-handler)
• Component Model (WIT) interop #238 — Component Model (WIT interop for host bindings)

Implementation notes

• Maps to WASI wasi:http/incoming-handler interface
• The handle[HttpServer] pattern models request routing as an effect handler
• Long-running server loop requires the Diverge effect (already supported)
• Real concurrency requires WASI 0.3 / handle[Async] (handle[Async] — custom scheduling strategies #270)