Event payload validation

src/sentry/seer/code_review/webhooks/task.py

@@ -61,6 +61,30 @@ def schedule_task(
         )
         return
 
+    # Validate payload before scheduling to catch schema mismatches early
+    try:
+        request_type = transformed_event.get("request_type")
+        if request_type == "pr-closed":
+            SeerCodeReviewTaskRequestForPrClosed.parse_obj(transformed_event)
+        else:
+            SeerCodeReviewTaskRequestForPrReview.parse_obj(transformed_event)
+    except Exception as e:
+        logger.warning(
+            "%s.validation_failed_before_scheduling",
+            PREFIX,
+            extra={
+                "error": str(e),
+                "github_event": github_event.value,
+                "github_event_action": github_event_action,
+                "organization_id": organization.id,
+                "repo_id": repo.id,
+            },
+        )
+        record_webhook_filtered(
+            github_event, github_event_action, WebhookFilteredReason.INVALID_PAYLOAD
+        )
+        return
+
     # Convert enum to string for Celery serialization
     process_github_webhook_event.delay(
         github_event=github_event.value,

tests/sentry/seer/code_review/webhooks/test_pull_request.py

@@ -381,3 +381,61 @@ def test_pull_request_closed_draft_still_sends_to_seer(self) -> None:
             call_kwargs = self.mock_seer.call_args[1]
             payload = call_kwargs["payload"]
             assert payload["request_type"] == SeerCodeReviewRequestType.PR_CLOSED.value
+
+    def test_validation_happens_before_task_scheduling_pr_closed(self) -> None:
+        """Test that invalid pr-closed payloads are caught before scheduling the Celery task."""
+        with (
+            self.code_review_setup(),
+            self.tasks(),
+            patch(
+                "sentry.seer.code_review.webhooks.task.transform_webhook_to_codegen_request"
+            ) as mock_transform,
+        ):
+            # Return an invalid payload missing required fields for pr-closed
+            mock_transform.return_value = {
+                "request_type": "pr-closed",
+                "data": {
+                    # Missing required fields like repo, pr_id, etc.
+                    "invalid": "payload"
+                },
+            }
+
+            event = orjson.loads(PULL_REQUEST_OPENED_EVENT_EXAMPLE)
+            event["action"] = "closed"
+
+            self._send_webhook_event(
+                GithubWebhookType.PULL_REQUEST,
+                orjson.dumps(event),
+            )
+
+            # Task should NOT be scheduled due to validation failure
+            self.mock_seer.assert_not_called()
+
+    def test_validation_happens_before_task_scheduling_pr_review(self) -> None:
+        """Test that invalid pr-review payloads are caught before scheduling the Celery task."""
+        with (
+            self.code_review_setup(),
+            self.tasks(),
+            patch(
+                "sentry.seer.code_review.webhooks.task.transform_webhook_to_codegen_request"
+            ) as mock_transform,
+        ):
+            # Return an invalid payload missing required fields for pr-review
+            mock_transform.return_value = {
+                "request_type": "pr-review",
+                "data": {
+                    # Missing required fields
+                    "invalid": "payload"
+                },
+            }
+
+            event = orjson.loads(PULL_REQUEST_OPENED_EVENT_EXAMPLE)
+            event["action"] = "opened"
+
+            self._send_webhook_event(
+                GithubWebhookType.PULL_REQUEST,
+                orjson.dumps(event),
+            )
+
+            # Task should NOT be scheduled due to validation failure
+            self.mock_seer.assert_not_called()