GET STARTED
Install the local extension
The MCPB extension connects Claude Desktop to Kelvin.app on the same Mac. It is the local alpha path: no Kelvin account and no OAuth.
Install step by step
- Open the latest release and download the file with the .mcpb extension.Open releases
- Double-click the file to open it in Claude Desktop.
- Confirm the installation and keep Kelvin.app open when using the tools.
What needs to be installed
- Kelvin.app, open on the same Mac. The extension is a bridge; it does not carry the simulator or engine inside the package.
- Claude Desktop on macOS.
- No Kelvin account is required for this local connection. Your Claude account plan remains subject to Anthropic's own rules.
Alpha languages and locales
Interface language, human intent and protocol are different surfaces. The Alpha's green support is this matrix:
| surface | green support |
|---|---|
| App inside the Simulator | en_US and pt_BR. |
| Intent written by a person | Brazilian Portuguese and English. The text arrives intact and remains untrusted data. |
| Internal model instructions | Canonical English: system prompts, tool names, schemas, error codes and events do not vary by language. |
| Contracts, IDs and protocol | Stable English. Field names and wire values are not translated. |
| Other iOS locales | They may work, but remain outside declared support and do not receive green status. |
The bridge boundary
Claude receives only the MCP actions Kelvin publishes for capsules, interaction, validation and evidence. The extension grants neither a shell nor general access to your Mac or the rest of the simulator.
Kelvin sends no sessions to Kelvin servers on this path. Claude Desktop and the model provider you choose may process the inputs and outputs that you or the agent request, such as a capture returned by an action; that processing follows the provider's terms and privacy settings.
When to use Remote MCP
Remote MCP with OAuth is another, separate way to work with Kelvin Code Cloud projects, runs and rooms. It remains available and is not required by the local extension.
Read about the remote connector