diff --git a/src/calibre/scraper/fetch.py b/src/calibre/scraper/fetch.py
index e00d82f351..78fd2ab5c6 100644
--- a/src/calibre/scraper/fetch.py
+++ b/src/calibre/scraper/fetch.py
@@ -55,7 +55,7 @@ class FakeResponse:
 
 class Browser:
 
-    def __init__(self, user_agent: str = '', headers: tuple[tuple[str, str], ...] = ()):
+    def __init__(self, user_agent: str = '', headers: tuple[tuple[str, str], ...] = (), start_worker: bool = False):
         self.tdir = ''
         self.worker = self.dispatcher = None
         self.dispatch_map = {}
@@ -64,6 +64,8 @@ class Browser:
         self.user_agent = user_agent
         self.lock = Lock()
         self.shutting_down = False
+        if start_worker:
+            self._ensure_state()
 
     def open(self, url_or_request, data=None, timeout=None):
         if data is not None:
diff --git a/src/calibre/scraper/fetch_backend.py b/src/calibre/scraper/fetch_backend.py
index 0e99e0a547..a720972f70 100644
--- a/src/calibre/scraper/fetch_backend.py
+++ b/src/calibre/scraper/fetch_backend.py
@@ -27,7 +27,7 @@ class RequestInterceptor(QWebEngineUrlRequestInterceptor):
         fb: FetchBackend = self.parent()
         if fb:
             key = qurl_to_key(req.requestUrl())
-            if dr := fb.download_requests[key]:
+            if dr := fb.download_requests.get(key):
                 for (name, val) in dr.headers:
                     req.setHttpHeader(name.encode(), val.encode())
 
@@ -36,7 +36,10 @@ def qurl_to_string(url: QUrl | str) -> str:
     return bytes(QUrl(url).toEncoded()).decode()
 
 
-qurl_to_key = qurl_to_string
+def qurl_to_key(url: QUrl | str) -> str:
+    return qurl_to_string(url).rstrip('/')
+
+
 Headers = list[tuple[str, str]]
 
 
@@ -91,6 +94,7 @@ class FetchBackend(QWebEnginePage):
         self.output_dir = output_dir or os.getcwd()
         profile.setDownloadPath(self.output_dir)
         super().__init__(profile, parent)
+        sys.excepthook = self.excepthook
         self.interceptor = RequestInterceptor(self)
         profile.setUrlRequestInterceptor(self.interceptor)
         self.request_download.connect(self.download, type=Qt.ConnectionType.QueuedConnection)
@@ -104,6 +108,11 @@ class FetchBackend(QWebEnginePage):
         t.setInterval(50)
         t.timeout.connect(self.enforce_timeouts)
 
+    def excepthook(self, cls: type, exc: Exception, tb) -> None:
+        if not isinstance(exc, KeyboardInterrupt):
+            sys.__excepthook__(cls, exc, tb)
+        QApplication.instance().exit(1)
+
     def on_input_finished(self, error_msg: str) -> None:
         if error_msg:
             self.send_response({'action': 'input_error', 'error': error_msg})
diff --git a/src/calibre/scraper/test_fetch_backend.py b/src/calibre/scraper/test_fetch_backend.py
index 2f2b12d0fd..cec5cbd70b 100644
--- a/src/calibre/scraper/test_fetch_backend.py
+++ b/src/calibre/scraper/test_fetch_backend.py
@@ -1,14 +1,18 @@
 #!/usr/bin/env python
 # License: GPLv3 Copyright: 2024, Kovid Goyal <kovid at kovidgoyal.net>
 
+import http.server
+import json
 import os
 import re
 import unittest
+from threading import Event, Thread
 
 from lxml.html import fromstring, tostring
 
 from calibre.utils.resources import get_path as P
 
+from .fetch import Browser
 from .simple import Overseer
 
 skip = ''
@@ -43,5 +47,80 @@ class TestSimpleWebEngineScraper(unittest.TestCase):
         self.assertFalse(w)
 
 
+class Handler(http.server.BaseHTTPRequestHandler):
+
+    request_count = 0
+
+    def do_GET(self):
+        h = {}
+        for k, v in self.headers.items():
+            h.setdefault(k, []).append(v)
+        ans = {
+            'path': self.path,
+            'headers': h,
+            'request_count': self.request_count,
+        }
+        data = json.dumps(ans).encode()
+        self.send_response(http.HTTPStatus.OK)
+        self.send_header('Content-type', 'application/json')
+        self.send_header('Content-Length', str(len(data)))
+        self.end_headers()
+        self.flush_headers()
+        self.wfile.write(data)
+
+    def log_request(self, code='-', size='-'):
+        self.request_count += 1
+
+
+@unittest.skipIf(skip, skip)
+class TestFetchBackend(unittest.TestCase):
+
+    ae = unittest.TestCase.assertEqual
+
+    def setUp(self):
+        self.server_started = Event()
+        self.server_thread = Thread(target=self.run_server, daemon=True)
+        self.server_thread.start()
+        self.server_started.wait(5)
+        self.request_count = 0
+
+    def tearDown(self):
+        self.server.shutdown()
+        self.server_thread.join(5)
+
+    def test_recipe_browser(self):
+        def u(path=''):
+            return f'http://localhost:{self.port}{path}'
+        def get(path=''):
+            raw = br.open(u(path)).read()
+            return json.loads(raw)
+        br = Browser(user_agent='test-ua', headers=(('th', '1'),), start_worker=True)
+        try:
+            r = get()
+            self.ae(r['request_count'], 0)
+            print(r)
+            self.ae(r['headers']['th'], ['1'])
+            self.ae(r['headers']['User-Agent'], ['test-ua'])
+            self.assertIn('Accept-Encoding', r['headers'])
+        finally:
+            br.shutdown()
+
+    def run_server(self):
+        import socketserver
+
+        def create_handler(*a):
+            ans = Handler(*a)
+            ans.backend = self
+            return ans
+
+        with socketserver.TCPServer(("", 0), create_handler) as httpd:
+            self.server = httpd
+            self.port = httpd.server_address[1]
+            self.server_started.set()
+            httpd.serve_forever()
+
+
 def find_tests():
-    return unittest.defaultTestLoader.loadTestsFromTestCase(TestSimpleWebEngineScraper)
+    ans = unittest.defaultTestLoader.loadTestsFromTestCase(TestSimpleWebEngineScraper)
+    ans.addTests(iter(unittest.defaultTestLoader.loadTestsFromTestCase(TestFetchBackend)))
+    return ans