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, 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 |
| Cursor | Host | HCP/1.1 | hcpx adopt cursor (rules and skills) | Guide |
| Codex | Host | HCP/1.1 | hcpx adopt codex (Skill, AGENTS.md, one MCP tool) | Guide |
| OpenCode | Host | HCP/1.1 | hcpx adopt opencode (plugin and config) | Guide |
| Grok Bot / Grok Build | Host | HCP/1.1 | hcpx adopt grok (bash + one MCP tool) | Guide |
AI SDK (HarnessAgent) | Host | HCP/1.1 | In-process tool loop | Guide |
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 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.
Claiming conformance#
Your row names the targets, the protocol version, the supported adapters, the sandbox posture and a link to evidence, as §14.6 describes.