GitHub - kpavlov/tachyon: 💫 Tachyon MCP Runtime for JVM - a Java Model Context Protocol (MCP) server with Streamable HTTP, native Netty transports, tasks, resources, prompts, resumable sessions, and stateless deployment support.

Tachyon MCP is a Java 21 Model Context Protocol (MCP) server built on Netty. It implements the 2025-11-25 Streamable HTTP transport, passes all official conformance tests, and runs stateless by default.

💫 Why Tachyon?

🧵 Synchronous code, asynchronous runtime — write blocking handlers; Java 21 virtual threads run them off the Netty event loop. No thread pools, reactive pipelines, or CompletableFuture boilerplate. Coroutine-first Kotlin DSL included.

🛡️ Stable APIs across spec changes — domain types (ToolHandler, ResourceHandler, PromptHandler, tasks) sit behind an internal protocol mapper. Spec upgrades change the mapper, not your handlers.

☁️ Serverless by default — stateless request handling works out of the box on AWS Lambda and similar. Opt into sessions (.session(s -> s.enabled(true))) for SSE resumability, Last-Event-ID replay, and TTL cleanup.

🚄 Production transport — Netty with backpressure, graceful shutdown, DNS rebinding protection, and native transport auto-detection (io_uring → epoll → kqueue → NIO).

TL;DR

1. Add dependency:

   <dependency>
       <groupId>dev.tachyonmcp</groupId>
       <artifactId>tachyon-server</artifactId>
       <version>1.0.0-beta.8</version>
   </dependency>

2. Create MCP server:

   import dev.tachyonmcp.server.TachyonServer;
   import dev.tachyonmcp.server.features.tools.ToolHandler;
   import dev.tachyonmcp.server.features.tools.ToolResult;
   
   void main() {
       TachyonServer.builder()
           .name("weather-mcp")
           .tool(ToolHandler.of(
               b -> b.name("get_forecast")
                   .description("Get weather forecast")
                   .inputSchema("""
                   {"type":"object","properties":{"city":{"type":"string"}},"required":["city"]}
                   """),
               (ctx, args) -> ToolResult.text("☀️ 22°C")))
           .port(8080)
           .start();
   }

Documentation

Agent Skill

Add agent skill to write better code using this SDK:

npx skills add kpavlov/tachyon --skill tachyon-mcp

The skill includes compilable Java and Kotlin example sources under .agents/skills/tachyon-mcp/resources/. They are compiled as extra source roots of the e2e module during mvn test to keep them valid.

Check out Skills CLI for more options.

Features

Full 2025-11-25 MCP surface over Streamable HTTP, verified by the official conformance suite:

Quick Start

See docs/quickstart.md for a full walkthrough with Java and Kotlin examples, curl test, and next-step links.

TasksExtension (SEP-1686)

var handle = TachyonServer.builder()
    .extension(TasksExtension.instance())  // exposes create_task tool + task://{id} resource
    .port(8080)
    .start();

Clients that include "extensions": {"io.modelcontextprotocol/tasks": {}} in their initialize capabilities receive the extension's tool and resource template. Clients that don't negotiate it see standard tasks/* methods. See docs/tasks.md.

Protocol isolation

Handler interfaces (ToolHandler, ResourceHandler, PromptHandler) and descriptor types use stable domain types. When Tachyon upgrades to a new protocol version, only the internal mapper layer changes; handler implementations are unaffected. Domain types track the 2026-07-28 spec shape where it improves on 2025-11-25 (e.g. Annotations.lastModified, ResourceLink in ContentBlock).

Performance

• Native transports — io_uring → epoll → kqueue → NIO auto-detect
• Write-buffer watermarks — 32 KB low / 128 KB high, backpressure wired end to end
• Batch flushing — ctx.write() accumulates, one ctx.flush() per boundary
• Sharable handlers — @Sharable pipeline handlers, no per-request allocation
• Virtual threads — handlers offloaded from the event loop, no manual pools
• Streaming JSON-RPC — Jackson streaming codec, no or limited ObjectMapper tree round-trips

Not yet supported

• HTTP/2 — transport is HTTP/1.1
• Rate limiting
• 2026-07-28 protocol version — domain types already track its shape; negotiation pending

FAQ

Can I deploy to AWS Lambda?

Yes. Servers are stateless by default, so each invocation processes one request independently. Enable sessions with .session(cfg -> cfg.enabled(true)) when you need SSE resumability or replay.

How do I write a tool?

See docs/tools.md — covers lambda and class-based handlers, input schema, and ToolResult factories.

How do I expose a resource?

See docs/resources.md — covers static URIs, dynamic handlers, URI templates, and subscriptions.

License

Tachyon MCP is available under the terms of the Apache 2.0.