From dd1484106d7d774d9e6a99017c0eaf10f1789866 Mon Sep 17 00:00:00 2001
From: Manoel Aranda Neto <marandaneto@gmail.com>
Date: Thu, 18 Jun 2026 10:55:20 +0200
Subject: [PATCH 1/2] fix: send batch sent_at in snake case

---
 .changeset/sweet-ravens-tap.md |  5 +++++
 posthog/request.py             |  2 +-
 posthog/test/test_request.py   | 18 ++++++++++++++++++
 3 files changed, 24 insertions(+), 1 deletion(-)
 create mode 100644 .changeset/sweet-ravens-tap.md

diff --git a/.changeset/sweet-ravens-tap.md b/.changeset/sweet-ravens-tap.md
new file mode 100644
index 00000000..8138f288
--- /dev/null
+++ b/.changeset/sweet-ravens-tap.md
@@ -0,0 +1,5 @@
+---
+'pypi/posthog': patch
+---
+
+Send batch `sent_at` using the backend-supported snake_case field.
diff --git a/posthog/request.py b/posthog/request.py
index b45f9011..6d38ee0b 100644
--- a/posthog/request.py
+++ b/posthog/request.py
@@ -228,7 +228,7 @@ def post(
     """Post the `kwargs` to the API"""
     log = logging.getLogger("posthog")
     body = kwargs
-    body["sentAt"] = datetime.now(tz=timezone.utc).isoformat()
+    body["sent_at"] = datetime.now(tz=timezone.utc).isoformat()
     trimmed_host = remove_trailing_slash(normalize_host(host))
     url = trimmed_host + cast(str, path)
     body["api_key"] = api_key
diff --git a/posthog/test/test_request.py b/posthog/test/test_request.py
index 21d67c98..5348133f 100644
--- a/posthog/test/test_request.py
+++ b/posthog/test/test_request.py
@@ -111,6 +111,24 @@ def test_post_sends_string_payload_without_gzip(self):
         self.assertEqual(url, "https://test.posthog.com/batch/")
         self.assertIsInstance(data, str)
 
+    def test_post_sends_snake_case_sent_at(self):
+        mock_response = requests.Response()
+        mock_response.status_code = 200
+        mock_session = mock.MagicMock()
+        mock_session.post.return_value = mock_response
+
+        request_module.post(
+            TEST_API_KEY,
+            host="https://test.posthog.com",
+            path="/batch/",
+            session=mock_session,
+            batch=[],
+        )
+
+        data = json.loads(mock_session.post.call_args.kwargs["data"])
+        self.assertIn("sent_at", data)
+        self.assertNotIn("sentAt", data)
+
     def test_post_sends_bytes_payload_with_gzip(self):
         mock_response = requests.Response()
         mock_response.status_code = 200

From e027111b09a3358eaf6c1f65ee941645cbbc7004 Mon Sep 17 00:00:00 2001
From: Manoel Aranda Neto <marandaneto@gmail.com>
Date: Thu, 18 Jun 2026 11:07:14 +0200
Subject: [PATCH 2/2] address pr review feedback

---
 posthog/test/test_request.py | 43 +++++++++++++++++++++---------------
 1 file changed, 25 insertions(+), 18 deletions(-)

diff --git a/posthog/test/test_request.py b/posthog/test/test_request.py
index 5348133f..d14e2dd7 100644
--- a/posthog/test/test_request.py
+++ b/posthog/test/test_request.py
@@ -59,6 +59,31 @@ def test_mask_tokens_in_url(url, expected):
     assert _mask_tokens_in_url(url) == expected
 
 
+@pytest.mark.parametrize(
+    "key, expected_present",
+    [
+        ("sent_at", True),
+        ("sentAt", False),
+    ],
+)
+def test_post_sends_snake_case_sent_at(key, expected_present):
+    mock_response = requests.Response()
+    mock_response.status_code = 200
+    mock_session = mock.MagicMock()
+    mock_session.post.return_value = mock_response
+
+    request_module.post(
+        TEST_API_KEY,
+        host="https://test.posthog.com",
+        path="/batch/",
+        session=mock_session,
+        batch=[],
+    )
+
+    data = json.loads(mock_session.post.call_args.kwargs["data"])
+    assert (key in data) is expected_present
+
+
 class TestRequests(unittest.TestCase):
     def test_valid_request(self):
         res = batch_post(
@@ -111,24 +136,6 @@ def test_post_sends_string_payload_without_gzip(self):
         self.assertEqual(url, "https://test.posthog.com/batch/")
         self.assertIsInstance(data, str)
 
-    def test_post_sends_snake_case_sent_at(self):
-        mock_response = requests.Response()
-        mock_response.status_code = 200
-        mock_session = mock.MagicMock()
-        mock_session.post.return_value = mock_response
-
-        request_module.post(
-            TEST_API_KEY,
-            host="https://test.posthog.com",
-            path="/batch/",
-            session=mock_session,
-            batch=[],
-        )
-
-        data = json.loads(mock_session.post.call_args.kwargs["data"])
-        self.assertIn("sent_at", data)
-        self.assertNotIn("sentAt", data)
-
     def test_post_sends_bytes_payload_with_gzip(self):
         mock_response = requests.Response()
         mock_response.status_code = 200