Fix MCP handler for JSON-RPC notifications

The handler now properly handles notifications (no 'id' field) by
returning 202 No Content instead of rejecting with method-not-found.
Fixes "sending notifications/initialized: Bad Request" error.

- Added notifications/initialized and notifications/cancelled handlers
- Unknown notifications silently ignored per JSON-RPC spec
- API route returns 202 for notifications

💘 Generated with Crush

Assisted-by: Crush:deepseek-v4-flash-free

src/api.js

@@ -209,7 +209,12 @@ export async function startServer(port = 9876) {
       // MCP JSON-RPC endpoint
       if (path === "/mcp" && req.method === "POST") {
         const body = await parseBody(req);
-        const mcpResp = await handleMCP(body);
+        const { response: mcpResp, isNotification } = await handleMCP(body);
+        if (isNotification || !mcpResp) {
+          res.writeHead(202, { "Content-Type": "application/json" });
+          res.end();
+          return;
+        }
         const status = mcpResp.error ? 400 : 200;
         res.writeHead(status, { "Content-Type": "application/json" });
         res.end(JSON.stringify(mcpResp));

src/mcp.js

@@ -32,24 +32,25 @@ const TOOLS = [
 export function createMCPHandler(runner) {
   return async function handleMCP(body) {
     if (!body || body.jsonrpc !== "2.0") {
-      return mcpError(null, -32600, "Invalid Request: must be JSON-RPC 2.0");
+      return { response: mcpError(null, -32600, "Invalid Request: must be JSON-RPC 2.0"), isNotification: false };
     }
 
     const { id, method, params } = body;
+    const isNotification = id === undefined || id === null;
 
     switch (method) {
       case "tools/list":
         return {
-          jsonrpc: "2.0",
+          response: { jsonrpc: "2.0", id, result: { tools: TOOLS } },
-          id,
+          isNotification: false
-          result: { tools: TOOLS }
         };
 
       case "tools/call":
-        return handleToolCall(id, params, runner);
+        return { response: await handleToolCall(id, params, runner), isNotification: false };
 
       case "initialize":
         return {
+          response: {
             jsonrpc: "2.0",
             id,
             result: {
@@ -57,10 +58,21 @@ export function createMCPHandler(runner) {
               capabilities: { tools: {} },
               serverInfo: { name: "polysearch", version: "2.0.0" }
             }
+          },
+          isNotification: false
         };
 
+      case "notifications/initialized":
+      case "notifications/cancelled":
+        log.debug({ method }, "notification received, no response");
+        return { response: null, isNotification: true };
+
       default:
-        return mcpError(id, -32601, `Method not found: ${method}`);
+        if (isNotification) {
+          log.debug({ method }, "unknown notification, silently ignored");
+          return { response: null, isNotification: true };
+        }
+        return { response: mcpError(id, -32601, `Method not found: ${method}`), isNotification: false };
     }
   };
 }