fix: mcp proxy header (#397)

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##### Checklist
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- [ ] `npm test` passes
- [ ] tests and/or benchmarks are included
- [ ] documentation is changed or added
- [ ] commit message follows commit guidelines

##### Affected core subsystem(s)
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##### Description of change
<!-- Provide a description of the change below this comment. -->

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<!-- This is an auto-generated comment: release notes by coderabbit.ai
-->
## Summary by CodeRabbit

* **Bug Fixes**
* Removed explicit transfer-encoding headers from Server-Sent Events
(SSE) streaming responses to improve protocol compliance and stream
reliability.
* **Tests**
* Added runtime checks validating header consistency (content-length vs
transfer-encoding) and improved fetch handling for streaming transport
tests to catch regressions earlier.

<sub>✏️ Tip: You can customize this high-level summary in your review
settings.</sub>
<!-- end of auto-generated comment: release notes by coderabbit.ai -->

Author: akitaSummer

plugin/controller/lib/impl/mcp/MCPControllerRegister.ts

@@ -219,7 +219,6 @@ export class MCPControllerRegister implements ControllerRegister {
       ctx.respond = false;
       ctx.set({
         'content-type': 'text/event-stream',
-        'transfer-encoding': 'chunked',
       });
       await ctx.app.ctxStorage.run(ctx, async () => {
         await mw(ctx, async () => {
@@ -352,7 +351,6 @@ export class MCPControllerRegister implements ControllerRegister {
 
           ctx.set({
             'content-type': 'text/event-stream',
-            'transfer-encoding': 'chunked',
           });
 
           await mcpServerHelper.server.connect(transport);
@@ -402,7 +400,6 @@ export class MCPControllerRegister implements ControllerRegister {
           ctx.respond = false;
           ctx.set({
             'content-type': 'text/event-stream',
-            'transfer-encoding': 'chunked',
           });
 
           await ctx.app.ctxStorage.run(ctx, async () => {
@@ -471,7 +468,6 @@ export class MCPControllerRegister implements ControllerRegister {
       self.transports[id] = transport;
       ctx.set({
         'content-type': 'text/event-stream',
-        'transfer-encoding': 'chunked',
       });
       ctx.respond = false;
       const mcpServerHelper = self.mcpServerHelperMap[name ?? 'default']();

plugin/controller/test/fixtures/apps/mcp-app/hook-plugin/lib/MCPControllerHook.ts

@@ -6,7 +6,6 @@ export const GetAlipayTeggHook = (app: Application) => {
     ctx.set({
       'content-type': 'text/event-stream',
       'cache-control': 'no-cache',
-      'transfer-encoding': 'chunked',
     });
     try {
       const auth = ctx.get('authorization');

plugin/mcp-proxy/test/fixtures/apps/mcp-proxy/app/controller/app.ts

@@ -166,7 +166,6 @@ export default class App extends Controller {
     this.ctx.set({
       'content-type': 'text/event-stream',
       'cache-control': 'no-cache',
-      'transfer-encoding': 'chunked',
     });
     const self = this;
     const transport = new SSEServerTransport('/message', this.ctx.res);
@@ -255,7 +254,6 @@ export default class App extends Controller {
         this.ctx.set({
           'content-type': 'text/event-stream',
           'cache-control': 'no-cache',
-          'transfer-encoding': 'chunked',
         });
         const eventStore = new InMemoryEventStore();
         const self = this;
@@ -305,7 +303,6 @@ export default class App extends Controller {
         this.ctx.set({
           'content-type': 'text/event-stream',
           'cache-control': 'no-cache',
-          'transfer-encoding': 'chunked',
         });
         const transport = transports[sessionId] as StreamableHTTPServerTransport;
         await transport.handleRequest(this.ctx.req, this.ctx.res);

plugin/mcp-proxy/test/proxy.test.ts

@@ -4,6 +4,7 @@ import { SSEClientTransport } from '@modelcontextprotocol/sdk/client/sse.js';
 import { Client } from '@modelcontextprotocol/sdk/client/index.js';
 import { CallToolRequest, CallToolResultSchema, ListToolsRequest, ListToolsResultSchema, LoggingMessageNotificationSchema } from '@modelcontextprotocol/sdk/types.js';
 import assert from 'assert';
+import { fetch } from 'urllib';
 
 async function listTools(client: Client) {
   const toolsRequest: ListToolsRequest = {
@@ -133,7 +134,17 @@ describe('plugin/mcp-proxy/test/proxy.test.ts', () => {
       });
       const baseUrl = await app.httpRequest()
         .post('/stream').url;
-      const streamableTransport = new StreamableHTTPClientTransport(new URL(baseUrl));
+      const streamableTransport = new StreamableHTTPClientTransport(new URL(baseUrl), {
+        // eslint-disable-next-line @typescript-eslint/ban-ts-comment
+        // @ts-ignore
+        fetch: async (...args) => {
+          // eslint-disable-next-line @typescript-eslint/ban-ts-comment
+          // @ts-ignore
+          const res = await fetch(...args);
+          assert.deepEqual(res.headers.has('content-length'), !res.headers.has('transfer-encoding'));
+          return res;
+        },
+      });
       const streamableNotifications: { level: string, data: string }[] = [];
       streamableClient.setNotificationHandler(LoggingMessageNotificationSchema, notification => {
         streamableNotifications.push({ level: notification.params.level, data: notification.params.data as string });