---
title: "Implementations"
description: "The runtimes, hosts, SDKs and packs known to implement HCP, with the protocol version and conformance target each one claims."
canonical: https://harnesscontextprotocol.io/docs/community/implementations
---

# Implementations

> The runtimes, hosts, SDKs and packs known to implement HCP, with the protocol version and conformance target each one claims.

Every row here is a self-attestation against
[§14 Conformance](/docs/specification/conformance), and the reference SDK,
runtime and CLI are a private preview on GitHub Packages today. To add your
implementation, open a PR to `hcp-docs` with a row that links your vector run
or test suite.

## Runtimes

| Name | Target | Version | Adapters | Sandbox | Notes |
|------|--------|---------|----------|---------|-------|
| Reference local runtime (`@harnesscontextprotocol/sdk`) | Runtime | HCP/1.1 | wrap, composite | allow-list + jail; native-local opt-in | Passes all reference vectors |
| Proprietary stub (`createProprietaryStubRuntime`) | Runtime (pipeline only) | HCP/1.1 | none | none | Authorization pipeline for hosted runtimes to extend |
| First hosted runtime | Runtime | HCP/1.1 | wrap | container | Private; first production deployment of a gated-write pack family with a local credential hub |

## Hosts

| Name | Target | Version | Integration | Notes |
|------|--------|---------|-------------|-------|
| Claude Code | Host | HCP/1.1 | `hcpx adopt claude` (Skill, one MCP tool, settings) | [Guide](/docs/hosts/coding-agents#claude-code) |
| Cursor | Host | HCP/1.1 | `hcpx adopt cursor` (rules and skills) | [Guide](/docs/hosts/coding-agents#cursor) |
| Codex | Host | HCP/1.1 | `hcpx adopt codex` (Skill, `AGENTS.md`, one MCP tool) | [Guide](/docs/hosts/coding-agents#codex) |
| OpenCode | Host | HCP/1.1 | `hcpx adopt opencode` (plugin and config) | [Guide](/docs/hosts/coding-agents#opencode) |
| Grok Bot / Grok Build | Host | HCP/1.1 | `hcpx adopt grok` (bash + one MCP tool) | [Guide](/docs/hosts/coding-agents#grok-bot) |
| AI SDK (`HarnessAgent`) | Host | HCP/1.1 | In-process tool loop | [Guide](/docs/hosts/ai-sdk) |

## SDKs and tools

| Name | Language | Version | Notes |
|------|----------|---------|-------|
| `@harnesscontextprotocol/sdk` | TypeScript | 0.3.0 | Reference SDK |
| `@harnesscontextprotocol/runtime` | TypeScript | 0.3.0 | The embeddable runtime surface of the SDK |
| `@harnesscontextprotocol/cli` (`hcpx`, also `hcp`) | TypeScript | 0.2.0 | Reference CLI and bootstrap Invoker |

## Packs

Gold packs ship with the SDK, and [Examples](/docs/packs/examples) walks
through them.

| Pack | Class | Adapter | Binding | Proves |
|------|-------|---------|---------|--------|
| `transit` | Public read | wrap | public | Five commands, twin face, `cli[]` rendering |
| `ledger` | Gated write | wrap | local | `confirm: "always"`, write grant, denial envelope, a declared approval `preview` |
| `echo` | Minimal | composite | public | Smallest valid pack |
| `hcp-cli` | Bootstrap | composite | local | The CLI's own commands as a pack |

They also scaffold from the CLI (`hcpx init transit --template transit`) and
appear in the [catalog](/docs/packs/share#catalog).

## Claiming conformance

Your row names the targets, the protocol version, the supported adapters, the
sandbox posture and a link to evidence, as
[§14.6](/docs/specification/conformance#146-claiming-conformance) describes.

## Sitemap

- [Documentation](https://harnesscontextprotocol.io/docs)
- [Packs](https://harnesscontextprotocol.io/packs)
- [Glossary](https://harnesscontextprotocol.io/docs/reference/glossary)
- [llms.txt](https://harnesscontextprotocol.io/llms.txt)
- [llms-full.txt](https://harnesscontextprotocol.io/llms-full.txt)
- [OpenAPI](https://harnesscontextprotocol.io/openapi.json)
- [MCP](https://harnesscontextprotocol.io/mcp)