Auto-Parallel Technologies, Inc.

PAGI (Perl Asynchronous Gateway Interface) is an async-first standard interface between Perl servers, frameworks, and applications. It is the spiritual successor to PSGI, designed for streaming and long-lived connections where classic request/response is not enough.

PAGI unifies multiple protocol types under one application model: an async handler receives a scope plus receive/send functions, and all IO is explicit via Futures. Core interface stability is the goal; higher-level convenience layers continue to evolve.

Key capabilities of PAGI include:

• One interface for HTTP, WebSocket, SSE, and lifespan (startup/shutdown)
• Event-based messaging for streaming responses and real-time apps
• Explicit backpressure via Futures, for predictable performance under load
• Reference server plus routers, middleware, and bundled apps
• Bridge for legacy sync applications via WrapPSGI

The PAGI distribution ships a full reference stack: 36 middleware modules, 17 bundled apps, plus extensive tests and examples to help teams start building quickly.

The included compliance report documents concrete results as of December 2025: 10/10 HTTP/1.1 compliance tests passed, 49/49 protocol fuzzing tests passed, and 215/301 WebSocket Autobahn cases passed (71% overall).

A PAGI application is a simple async handler: it receives $scope, $receive, and $send. Both $receive and $send return Futures, so you can await and naturally apply backpressure instead of buffering unbounded data.

The screenshot links to the Raw PAGI example with explicit UTF-8 handling from the PAGI POD. The same model applies across http, websocket, and sse scope types.

Developer-focused docs:

• PAGI::Tutorial - runnable examples and patterns
• PAGI::Endpoint::Router - route HTTP, WebSocket, and SSE endpoints
• PAGI::Middleware - middleware stack and common integrations

Deep-dive MetaCPAN documentation:

• PAGI - core interface and spec overview
• PAGI::Server - reference server
• PAGI::Server::Compliance - compliance numbers and methodology
• PAGI::App::WrapPSGI - legacy PSGI bridge
• Distribution on MetaCPAN

PAGI includes PAGI::Server, an IO::Async-based reference server implementation for HTTP/1.1, WebSocket, and SSE, with optional TLS support. It is designed to be clear, testable, and practical - and it is often deployed behind a reverse proxy for production.

Operational highlights:

• HTTP/1.1 keepalive, streaming responses, and resource limits
• WebSocket and SSE support for real-time applications
• Multi-worker mode with graceful restarts and signal control
• Explicit backpressure on send/receive paths via Futures
• Security-focused middleware such as SecurityHeaders