From 8d7b068545a906503a4e6d92884b534ec01135ea Mon Sep 17 00:00:00 2001
From: "sentry[bot]" <39604003+sentry[bot]@users.noreply.github.com>
Date: Sat, 12 Sep 2026 10:42:19 +0000
Subject: [PATCH 1/2] fix(uptime): Prevent Environment.DoesNotExist on monitor
 update

---
 src/sentry/uptime/endpoints/validators.py     | 14 +++++++------
 .../test_project_uptime_alert_details.py      | 20 +++++++++++++++++++
 2 files changed, 28 insertions(+), 6 deletions(-)

diff --git a/src/sentry/uptime/endpoints/validators.py b/src/sentry/uptime/endpoints/validators.py
index 8c619a85da74..f925a78bcf8b 100644
--- a/src/sentry/uptime/endpoints/validators.py
+++ b/src/sentry/uptime/endpoints/validators.py
@@ -417,14 +417,16 @@ def update(self, instance: Detector, data):
         )
 
         if "environment" in data:
+            env_name = data["environment"]
+        else:
+            env_name = instance.config["environment"]
+
+        if env_name is None:
+            environment = None
+        else:
             environment = Environment.get_or_create(
                 project=self.context["project"],
-                name=data["environment"],
-            )
-        else:
-            environment = Environment.objects.get(
-                projects=self.context["project"],
-                name=instance.config["environment"],
+                name=env_name,
             )
 
         if "mode" in data:
diff --git a/tests/sentry/uptime/endpoints/test_project_uptime_alert_details.py b/tests/sentry/uptime/endpoints/test_project_uptime_alert_details.py
index d8d5b5ae36f0..f254784d9dab 100644
--- a/tests/sentry/uptime/endpoints/test_project_uptime_alert_details.py
+++ b/tests/sentry/uptime/endpoints/test_project_uptime_alert_details.py
@@ -125,6 +125,26 @@ def test_enviroment(self) -> None:
         assert detector.name == "test"
         assert detector.config.get("environment") == "uptime-prod"
 
+    def test_update_without_environment_when_monitor_has_none(self) -> None:
+        """Regression test: updating a monitor created without an environment
+        must not raise Environment.DoesNotExist when environment is omitted from
+        the PUT payload."""
+        detector = self.create_uptime_detector()
+        # Confirm the monitor has no environment set
+        assert detector.config.get("environment") is None
+
+        resp = self.get_success_response(
+            self.organization.slug,
+            detector.linked_project.slug,
+            detector.id,
+            name="updated-name",
+        )
+        detector.refresh_from_db()
+        assert resp.data == serialize(detector, self.user, UptimeDetectorSerializer())
+        assert detector.name == "updated-name"
+        # Environment should remain None
+        assert detector.config.get("environment") is None
+
     def test_user(self) -> None:
         detector = self.create_uptime_detector()
 

From 612ed00dccde1aaa6cb264775bc1549e25f8acac Mon Sep 17 00:00:00 2001
From: "sentry[bot]" <39604003+sentry[bot]@users.noreply.github.com>
Date: Sat, 12 Sep 2026 11:02:01 +0000
Subject: [PATCH 2/2] fix(uptime): Prevent Environment.DoesNotExist on monitor
 update

---
 .../uptime/endpoints/test_project_uptime_alert_details.py    | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/tests/sentry/uptime/endpoints/test_project_uptime_alert_details.py b/tests/sentry/uptime/endpoints/test_project_uptime_alert_details.py
index f254784d9dab..0b7d1147ad2f 100644
--- a/tests/sentry/uptime/endpoints/test_project_uptime_alert_details.py
+++ b/tests/sentry/uptime/endpoints/test_project_uptime_alert_details.py
@@ -130,7 +130,10 @@ def test_update_without_environment_when_monitor_has_none(self) -> None:
         must not raise Environment.DoesNotExist when environment is omitted from
         the PUT payload."""
         detector = self.create_uptime_detector()
-        # Confirm the monitor has no environment set
+        # Simulate a monitor that was created without an environment by clearing
+        # the environment from the config (mirrors the pre-existing bug scenario).
+        detector.config["environment"] = None
+        detector.save(update_fields=["config"])
         assert detector.config.get("environment") is None
 
         resp = self.get_success_response(