Security-first reverse proxy

built to guard the free web

A high-performance, security-focused reverse proxy built on Cloudflare’s Pingora framework. Sleepable ops at the edge with extensible agent architecture.

56+Features

25+Agents

0GC Pauses

100%Memory Safe

Security First

Built in Rust for memory safety by design. WAF capabilities, rate limiting, and threat detection run as isolated agents, keeping the core minimal and auditable.

Blazingly Fast

Rust with no garbage collector, powered by Tokio’s async runtime. Handle millions of requests with minimal latency, predictable performance, and a tiny memory footprint.

Edge Native

Inherits Cloudflare’s battle-tested edge expertise through the Pingora framework. Sleepable operations, intelligent traffic management, and automatic failover built-in.

First-Class Agents

A fundamental shift from traditional proxies. Hook into every request and response phase with isolated agents. Made by builders, for builders.

Observable

Transparency and deterministic behavior above all. Built-in metrics, tracing, and logging with OpenTelemetry. Every decision is testable and explainable.

Human Readable Config

Configured with KDL, a document language that combines the best of JSON, YAML, and XML. Made for human cognition and machine parsing alike.

API Gateway

Route, rate-limit, and secure your APIs. JWT validation, request transformation, and backend load balancing out of the box.

Edge Security

WAF rules, IP denylists, and threat detection at the edge. Block attacks before they reach your infrastructure.

LLM Proxy

Token-based rate limiting, provider failover, and content guardrails. Purpose-built for AI/ML inference workloads.

Static + Dynamic

Serve static files with zero-copy I/O while proxying dynamic requests. SPA routing, compression, and caching built-in.

Fleet Management

Manage Sentinel instances at scale with the control plane. Signed config bundles, rolling deployments, health gates, and audit logging.

Most operational incidents don’t stem from performance limitations. They come from the hidden complexity that accumulates over time: memory growth from unbounded queues, unexpected timeout interactions, concealed retry mechanisms, and security features that degrade under load. These issues surface precisely when troubleshooting is most difficult.

Sentinel takes a different approach. Every significant behavior requires explicit configuration with front-end validation and runtime visibility. There are no silent defaults or hidden policy layers that change how your traffic flows. When something goes wrong, you can reason about it.

Sentinel draws inspiration from River, a reverse proxy initiated by the Memory Safety initiative to bring memory-safe software to the Internet’s most critical infrastructure. When River’s development was halted early on, Sentinel carried forward its best ideas—like the KDL configuration language—while introducing new concepts: first-class agents, a minimal and auditable core, and a focus on sleepable operations.

Bounded by Design

Hard constraints on memory and queues. Consistent timeout behavior. Regulated backpressure. Nothing grows unbounded, so nothing surprises you at 3am.

Minimal Core

Complex and policy-heavy functionality lives in external agents that can be updated, rate-limited, or disabled independently—without touching the proxy itself.

Transparent Security

Reasonable limits, clear decision-making, and measured responses. Security you can understand and explain, not an opaque black box.

Sentinel is built for long-running production systems managed by humans on shared infrastructure. It prioritizes predictability and reasoning over feature breadth or maximum flexibility.

Ready to guard your infrastructure?

Get started in minutes. Explore the docs, try the interactive playground, convert existing configs, or dive into the agent registry.

How does Sentinel compare to nginx or Envoy?

Sentinel takes a fundamentally different approach to reverse proxying. Built in Rust on Cloudflare’s Pingora, it prioritizes memory safety and explicit configuration over hidden defaults.

• Security-first: Isolated agent architecture means a buggy plugin can’t crash your proxy
• No magic: Every behavior requires explicit configuration—no surprise defaults
• Observable: Built-in OpenTelemetry support for metrics, tracing, and logging

See our detailed comparison guide for benchmarks and feature matrices.

Is Sentinel production-ready?

The core proxy is production-ready — routing, upstreams, health checks, TLS, KDL configuration with validation, the agent protocol (auth, WAF, rate limiting), and signed binaries with SBOM and SLSA attestations.

Some features are in beta: hot reload, gRPC proxying, WebSocket long-lived connections, and some community agents (see the agent registry for per-agent status).

A few things are not yet available: Windows support (Linux + macOS only), built-in service mesh / mTLS auto-rotation, and the control plane for fleet management is in early development. Sentinel is not a CDN or edge compute platform.

Check our quick start guide to deploy your first instance.

What platforms are supported?

Pre-built binaries are available for the most common platforms:

• Linux x86_64: glibc 2.17+ (RHEL 7+, Ubuntu 18.04+, Debian 10+)
• macOS: Intel (x86_64) and Apple Silicon (aarch64)
• Containers: Official OCI images for amd64 and arm64

Linux ARM64 users can build from source or use our container images. See the installation guide for all options including Homebrew and cargo.

How do agents work?

Agents are Sentinel’s extension mechanism—isolated processes that hook into request/response phases without risking proxy stability.

• Process isolation: Each agent runs in its own process; crashes don’t affect the proxy
• Language agnostic: Write agents in Rust, Go, Python, or any language with gRPC support
• Phase hooks: Intercept requests at on_request, on_response, or on_error phases

Browse our agent registry for ready-to-use agents like WAF, Auth, and AI Gateway. Or learn to build your own.

Can I migrate from nginx or HAProxy?

Yes—we’ve built tools to make migration straightforward:

• Config Converter: Paste your nginx, HAProxy, or Traefik config and get equivalent KDL
• Playground: Test and validate your converted configuration before deploying
• Migration Guide: Step-by-step instructions for common setups

The converter handles most directives automatically. For complex setups, check our nginx migration or HAProxy migration docs.

Is Sentinel free to use?

Yes, completely. Sentinel is open source under the Apache 2.0 license.

• No usage limits: Run it anywhere, at any scale, forever
• No phone-home: Sentinel never contacts external servers
• Modify freely: Fork it, extend it, embed it in your products

We believe critical infrastructure should be transparent and free from vendor lock-in. Read our manifesto to learn why. Contributions are welcome on GitHub.

The Sentinel Manifesto

Guarding the Free Web

Why we believe in boring infrastructure, explicit security, and building software that respects the humans who operate it.

The web is a commons. Critical infrastructure should be transparent, inspectable, and free from vendor lock-in—run it anywhere, read every line, and sleep at night.

Read the Manifesto