Claude Desktop extension (.mcpb)

Beta

The .mcpb extension format is currently in beta. It works well for most users, but report any issues to GitHub Issues. For the most stable experience, use Homebrew or npm/npx.

Recommended for Claude Desktop

The simplest, no-terminal way to add devcoach to Claude Desktop — one click, runs on Desktop's built-in runtime.

Every GitHub release ships a prebuilt devcoach-<version>.mcpb — a single bundle that runs on Claude Desktop's built-in Node runtime, so no Node install or terminal is required:

1. Download devcoach-<version>.mcpb from the latest release.
2. In Claude Desktop open Settings → Extensions → Install Extension… and pick the downloaded file.

That's it — the devcoach tools, resources, and the devcoach_instructions prompt are available in your next conversation, and the database is created at ~/.devcoach/coaching.db on first use.

Unverified publisher

The bundle is self-signed, so Claude Desktop shows it as coming from an unverified publisher. A verified signature needs a real code-signing certificate, which isn't configured — the label is expected. Every release also publishes SHASUMS256.txt next to the .mcpb if you want to verify the download.

From source

npm run mcpb        # → dist-mcpb/devcoach-<version>.mcpb
npm run mcpb:sign   # self-sign it — installs with the same "unverified publisher" label

Then install the resulting file through the same Settings → Extensions → Install Extension… dialog.

When devcoach does not start

This applies to every way devcoach reaches Claude Desktop: the extension above, or an entry that devcoach install wrote in claude_desktop_config.json (Homebrew, npm).

Read the log first. Claude Desktop keeps one log per MCP server:

OS	Log
macOS	~/Library/Logs/Claude/mcp-server-devcoach.log
Windows	%APPDATA%\Claude\logs\mcp-server-devcoach.log

Each time devcoach starts it writes one line there, then one more once Claude Desktop is connected:

devcoach 2.6.3 mcp · node 26.5.0 via homebrew (/opt/homebrew/Cellar/node/26.5.0/bin/node) · homebrew (/opt/homebrew/Cellar/devcoach/2.6.3/…/dist/bin.js) · data ~/.devcoach (schema 6)
devcoach 2.6.3 mcp · client claude-ai 0.1.0

That is which devcoach ran, on which Node, installed how. Your home directory is shown as ~, so the log can be shared as is.

Failed to spawn process: No such file or directory means devcoach never ran: there is no line of its own after it. The operating system could not execute the command in Claude Desktop's config, for one of two reasons:

• the command is not there — devcoach was uninstalled, or a bare devcoach is not on the PATH Claude Desktop uses (it prints that PATH in the log, next to Using MCP server command);
• the command is there, but the Node it names in its first line is not — e.g. Homebrew's Node was removed while Homebrew's devcoach still points at it.

Run devcoach doctor: its Claude Desktop section resolves the command on the PATH from Claude Desktop's log, checks the Node behind it, and says which case it is. Then devcoach install --claude-desktop --force writes an absolute command, which does not depend on Claude Desktop's PATH. Restart Claude Desktop.

Ignore Server started and connected successfully while reading: Claude Desktop writes it before the process starts, so it also appears right before a failure.

nvm, fnm, volta, asdf, mise

A devcoach installed with npm i -g under a Node version manager lives inside one Node version's directory (~/.nvm/versions/node/v26.5.0/…). Removing or switching that version removes devcoach with it, and Claude Desktop starts failing with the message above. devcoach install warns when it writes such a path, and devcoach doctor names the version it depends on: run devcoach install --force again after changing Node.

→ Next: Coaching in your agent.