What causes "Unknown server type: ${serverType}" in can1357/oh-my-pi?

Fix the server's 'type' in the MCP config to one of: stdio, http, or sse.

can1357/oh-my-pi · error · Error

Unknown server type: ${serverType}

Error message

Unknown server type: ${serverType}

What it means

createTransport dispatches on the MCP server config's type field ('stdio' | 'http' | 'sse'); any other value reaches the default branch and throws 'Unknown server type: <type>'. It guards the transport factory against misconfigured or future-unknown server type strings.

Source

Thrown at packages/coding-agent/src/mcp/client.ts:84

			throw Object.assign(new Error(`Unsupported server request: ${method}`), { code: -32601 });
	}
}

/**
 * Create a transport for the given server config.
 */
async function createTransport(config: MCPServerConfig): Promise<MCPTransport> {
	const serverType = config.type ?? "stdio";

	switch (serverType) {
		case "stdio":
			return createStdioTransport(config as MCPStdioServerConfig);
		case "http":
			return createHttpTransport(config as MCPHttpServerConfig);
		case "sse":
			return createSseTransport(config as MCPSseServerConfig);
		default:
			throw new Error(`Unknown server type: ${serverType}`);
	}
}

/**
 * Initialize connection with MCP server.
 */
async function initializeConnection(
	transport: MCPTransport,
	options?: {
		signal?: AbortSignal;
		/** Called after notifications/initialized succeeds. */
		onInitialized?: () => void | Promise<void>;
	},
): Promise<MCPInitializeResult> {
	const params: MCPInitializeParams = {
		protocolVersion: MCP_PROTOCOL_VERSION,
		capabilities: {
			roots: { listChanged: false },

View on GitHub (pinned to 9690622007)

Solutions

Fix the server's 'type' in the MCP config to one of: stdio, http, or sse.
Check for typos/whitespace in the type string and validate the JSON config.
Update the CLI if the config was authored by a newer tool using a new transport type.
Use the /mcp add wizard, which writes valid types instead of hand-editing.

Example fix

// before (MCP config JSON)
{ "myserver": { "type": "websocket", "url": "http://localhost:3000" } }
// after
{ "myserver": { "type": "http", "url": "http://localhost:3000" } }

Defensive patterns

Strategy: validation

Validate before calling

const TRANSPORT_TYPES = new Set(["stdio", "http", "sse"]);
function assertValidTransportType(cfg: { type: string }): void {
  if (!TRANSPORT_TYPES.has(cfg.type)) {
    throw new Error(`Config pre-check: unknown MCP server type '${cfg.type}' (expected stdio|http|sse)`);
  }
}

Type guard

function isKnownServerType(t: string): t is "stdio" | "http" | "sse" {
  return t === "stdio" || t === "http" || t === "sse";
}

Try / catch

try {
  await connectToServer(name, config);
} catch (err) {
  if (err instanceof Error && err.message.startsWith("Unknown server type:")) {
    console.error(`${err.message} — fix 'type' in the MCP config (stdio|http|sse)`);
    return;
  }
  throw err;
}

Prevention

Validate MCP config JSON against a schema before loading.
Use the /mcp add wizard instead of hand-editing type fields.
Trim/normalize the type string when reading third-party configs.
Keep the client updated for newly introduced transport types.

When it happens

Trigger: connect() → createTransport() with a config whose type is misspelled (e.g. 'websocket', 'http2', or with stray whitespace) or from a newer config schema the client doesn't recognize.

Common situations: Hand-edited MCP config with a wrong 'type' value; config copied from another tool using different transport names; config written by a newer client version introducing an unsupported type.

Related errors

AI-assisted analysis of can1357/oh-my-pi@9690622007 (2026-08-31). Data as JSON: /api/errors/8ca229c7f6639ed8. Report an issue: GitHub.