[spark-compete] fix(spawner-ui): return 400 for empty/malformed JSON body on MCP endpoints

src/routes/api/mcp/+server.ts

@@ -39,7 +39,12 @@ export const POST: RequestHandler = async (event) => {
 
 	try {
 		const { request } = event;
-		const body = await request.json();
+		let body: any;
+		try {
+			body = await request.json();
+		} catch {
+			return json({ error: 'Invalid or missing JSON body' }, { status: 400 });
+		}
 		const { instanceId, mcpId, config, npmPackage, defaultArgs, envVars, command, args } = body as {
 			instanceId: string;
 			mcpId?: string;
@@ -150,7 +155,12 @@ export const DELETE: RequestHandler = async (event) => {
 
 	try {
 		const { request } = event;
-		const body = await request.json();
+		let body: any;
+		try {
+			body = await request.json();
+		} catch {
+			return json({ error: 'Invalid or missing JSON body' }, { status: 400 });
+		}
 		const { instanceId } = body as { instanceId: string };
 
 		if (!instanceId) {

src/routes/api/mcp/call/+server.ts

@@ -19,7 +19,12 @@ export const POST: RequestHandler = async (event) => {
 
 	try {
 		const { request } = event;
-		const body = await request.json();
+		let body: any;
+		try {
+			body = await request.json();
+		} catch {
+			return json({ error: 'Invalid or missing JSON body' }, { status: 400 });
+		}
 		const { instanceId, toolName, args, requestId } = body as {
 			instanceId: string;
 			toolName: string;

src/routes/api/mcp/mcp.integration.test.ts

@@ -149,4 +149,36 @@ describe('/api/mcp', () => {
 		expect(body.authority.reasonCodes).toContain('native_governor_required');
 		expect(connectMCP).not.toHaveBeenCalled();
 	});
+
+	it('returns 400 for empty request body instead of 500', async () => {
+		const response = await POST({
+			request: new Request('http://127.0.0.1/api/mcp', {
+				method: 'POST',
+				headers: { 'content-type': 'application/json', 'x-api-key': 'mcp-test-secret' },
+				body: ''
+			}),
+			url: new URL('http://127.0.0.1/api/mcp'),
+			getClientAddress: () => '127.0.0.1'
+		} as never);
+
+		expect(response.status).toBe(400);
+		expect(await response.json()).toMatchObject({ error: expect.stringContaining('JSON body') });
+		expect(connectMCP).not.toHaveBeenCalled();
+	});
+
+	it('returns 400 for malformed JSON body instead of 500', async () => {
+		const response = await POST({
+			request: new Request('http://127.0.0.1/api/mcp', {
+				method: 'POST',
+				headers: { 'content-type': 'application/json', 'x-api-key': 'mcp-test-secret' },
+				body: '{not valid json'
+			}),
+			url: new URL('http://127.0.0.1/api/mcp'),
+			getClientAddress: () => '127.0.0.1'
+		} as never);
+
+		expect(response.status).toBe(400);
+		expect(await response.json()).toMatchObject({ error: expect.stringContaining('JSON body') });
+		expect(connectMCP).not.toHaveBeenCalled();
+	});
 });