From faffecaacf9bd01f4f5758b642a5375537c78d4c Mon Sep 17 00:00:00 2001
From: "xuping.wang" <2232455931@qq.com>
Date: Sun, 30 Aug 2026 00:52:33 +0800
Subject: [PATCH] fix(eio): report oversized polling payloads

Emit the existing transport error after a polling request exceeds maxHttpBufferSize so server-side disconnect handlers receive an actionable description.

Assisted-by: OpenAI Codex:gpt-5

Signed-off-by: xuping.wang <2232455931@qq.com>
---
 packages/engine.io/lib/transports/polling.ts |  1 +
 packages/engine.io/test/server.js            | 12 ++++++++----
 2 files changed, 9 insertions(+), 4 deletions(-)

diff --git a/packages/engine.io/lib/transports/polling.ts b/packages/engine.io/lib/transports/polling.ts
index f48f0cd6b..a465f0042 100644
--- a/packages/engine.io/lib/transports/polling.ts
+++ b/packages/engine.io/lib/transports/polling.ts
@@ -153,6 +153,7 @@ export class Polling extends Transport {
         exceededMaxHttpBufferSize = true;
         res.writeHead(413).end();
         cleanup();
+        this.onError("payload too large");
         return;
       }
 
diff --git a/packages/engine.io/test/server.js b/packages/engine.io/test/server.js
index bbfa86068..bc7245f59 100644
--- a/packages/engine.io/test/server.js
+++ b/packages/engine.io/test/server.js
@@ -1823,7 +1823,7 @@ describe("server", () => {
       });
     });
 
-    it("should not be receiving data when getting a message longer than maxHttpBufferSize when polling", (done) => {
+    it("should report a message longer than maxHttpBufferSize when polling", (done) => {
       const opts = {
         allowUpgrades: false,
         transports: ["polling"],
@@ -1837,13 +1837,17 @@ describe("server", () => {
               new Error("Test invalidation (message is longer than allowed)"),
             );
           });
+          conn.on("close", (reason, description) => {
+            expect(reason).to.be("transport error");
+            expect(description).to.be.an(Error);
+            expect(description.type).to.be("TransportError");
+            expect(description.message).to.be("payload too large");
+            done();
+          });
         });
         socket.on("open", () => {
           socket.send("aasdasdakjhasdkjhasdkjhasdkjhasdkjhasdkjhasdkjha");
         });
-        socket.on("close", () => {
-          done();
-        });
       });
     });