Tachyon

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Tachyon MCP is a Java 21+ server runtime for the Model Context Protocol. It implements MCP 2025-11-25 and 2026-07-28 over Streamable HTTP and passes the official conformance suites for both versions.

Build servers with synchronous Java handlers or a coroutine-first Kotlin DSL. Tachyon runs blocking handlers on virtual threads, keeps them off the Netty event loop, and requires no application framework.

Why Tachyon?

• Simple handlers -- write blocking Java code or suspending Kotlin code without reactive

pipelines or manual thread pools.

• Stable application API -- protocol-version mappers isolate handlers from wire-format changes.
• Java annotations support -- adapt existing mcp-java, LangChain4j, or Spring AI annotated services into Tachyon MCP servers.
• Stateless by default -- opt into sessions only when you need resumable SSE, event replay, and

TTL cleanup.

• Production transport -- Netty backpressure, graceful shutdown, DNS-rebinding protection,

CORS, and native transport auto-detection (io_uring → epoll → kqueue → NIO).

• Built-in OpenTelemetry -- register tachyon-opentelemetry's listener for MCP

semantic-convention spans and metrics, with an opt-in policy for payload capture.

Quickstart

Import the [BOM](tachyon-bom) once to pin the version, then add the core dependency:

    
        
            dev.tachyonmcp
            tachyon-bom
            ${tachyon.version} 
            pom
            import
        
    

    
        dev.tachyonmcp
        tachyon-core
    

Create and start a server:

import dev.tachyonmcp.api.server.features.tools.ToolResult;
import dev.tachyonmcp.core.server.TachyonServer;

public class WeatherMcpServer {
    public static void main(String... args) {
        var server = TachyonServer.builder()
            .name("weather-mcp")
            .withTools(tools -> tools.register(
                tool -> tool.name("get_forecast")
                    .description("Get weather forecast")
                    .inputSchema("""
                        {"type":"object","properties":{"city":{"type":"string"}},"required":["city"]}
                        """),
                (context, request) -> ToolResult.text("☀️ 22°C")))
            .port(8080)
            .build();
        server.start();
    }
}

See the [quickstart](docs/quickstart.md) for Java and Kotlin examples plus a curl test.

Implemented features

| Area | Support | |---|---| | MCP surface | Tools, resources and templates, prompts, completions, logging, sampling, form/URL elicitation, cancellation, subscriptions, pagination, and progress notifications | | Annotations | Optional adapters for [mcp-java, LangChain4j, and Spring AI](docs/annotations.md), mapped onto Tachyon's standard registries | | Tasks | Full tasks/* lifecycle, state validation, status notifications, retention, and TasksExtension for [SEP-1686](docs/tasks.md) | | Agent Skills | SkillsExtension implements the [SEP-2640](docs/extensions/mcp-skills.md) draft: filesystem/classpath registries, skill:// resources, skills/list, skills/get, and directory reads | | Extensions | [SEP-2133](docs/extensions.md) negotiation, custom JSON-RPC methods, capability advertisement, and extension-gated features | | Runtime | Stateless or resumable sessions, Last-Event-ID replay, pluggable stores, virtual-thread handlers, request timeouts, and graceful draining | | Observability | OpenTelemetry spans and metrics via tachyon-opentelemetry, following the MCP semantic conventions, plus an opt-in payload capture policy -- see [docs](docs/observability.md) | | Java and Kotlin | Independent sync/async Java contracts and a coroutine-first [Kotlin DSL](docs/kotlin.md) | | Testing | Official conformance suites plus a [testkit](docs/testkit.md) for dynamic servers and fluent JSON-RPC assertions |

Documentation and examples

• [Configuration](docs/configuration.md) -- network, native I/O, sessions, CORS, and runtime limits
• [Observability](docs/observability.md) -- observation listeners, payload capture policy, and the bundled OpenTelemetry integration
• [Tools](docs/tools.md), [resources](docs/resources.md), and [tasks](docs/tasks.md) -- feature APIs and examples
• [Annotations](docs/annotations.md) -- mcp-java, LangChain4j, and Spring AI providers
• [Extensions](docs/extensions.md) and [MCP Skills](docs/extensions/mcp-skills.md) -- custom protocol methods and SEP support
• [Kotlin DSL](docs/kotlin.md) -- builders, scopes, and suspending handlers
• [Examples](examples/README.md) -- runnable Java and Kotlin servers
• [FAQ](docs/faq.md) -- frameworks, concurrency, deployment, and compatibility

Coding-agent skill

This repository also includes a skill that teaches coding agents how to build Tachyon servers. It is separate from the server-side SkillsExtension described above.

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

Its Java and Kotlin examples are compiled during the project build to keep them current.

License

Tachyon MCP is available under the terms of the [Apache 2.0](LICENSE).

Source & license

This open-source MCP server is cataloged on AgentStack and links to its original source — we do not rehost the code.

• Author: tachyonmcp
• Source: tachyonmcp/tachyon
• License: Apache-2.0
• Homepage: https://deepwiki.com/tachyonmcp/tachyon

Install and usage instructions live in the source repository linked above.