From 16ab90121f7196ae836b537cf2d5016819bbb921 Mon Sep 17 00:00:00 2001
From: charlesedeh021-cell
 <294822331+charlesedeh021-cell@users.noreply.github.com>
Date: Mon, 29 Jun 2026 20:57:05 +0100
Subject: [PATCH] fix: delegate after streamed error responses

---
 backend/src/middleware/error.middleware.ts |  4 ++++
 backend/tests/error.middleware.test.ts     | 11 +++++++++++
 2 files changed, 15 insertions(+)

diff --git a/backend/src/middleware/error.middleware.ts b/backend/src/middleware/error.middleware.ts
index 252cdfb0..af90505b 100644
--- a/backend/src/middleware/error.middleware.ts
+++ b/backend/src/middleware/error.middleware.ts
@@ -14,6 +14,10 @@ export const errorHandler = (
 ) => {
     logger.error('Unhandled error:', err);
 
+    if (res.headersSent) {
+        return next(err);
+    }
+
     // Handle Zod Validation Errors
     if (err instanceof ZodError) {
         return res.status(400).json({
diff --git a/backend/tests/error.middleware.test.ts b/backend/tests/error.middleware.test.ts
index 1d07d72c..a7f497fa 100644
--- a/backend/tests/error.middleware.test.ts
+++ b/backend/tests/error.middleware.test.ts
@@ -44,4 +44,15 @@ describe('Error Middleware', () => {
     errorHandler(error, req as Request, res as Response, next);
     expect(res.status).toHaveBeenCalledWith(500);
   });
+
+  it('should delegate to next when headers were already sent', () => {
+    const error = new Error('Stream failed after headers');
+    res.headersSent = true;
+
+    errorHandler(error, req as Request, res as Response, next);
+
+    expect(next).toHaveBeenCalledWith(error);
+    expect(res.status).not.toHaveBeenCalled();
+    expect(res.json).not.toHaveBeenCalled();
+  });
 });