diff --git a/src/sentry/seer/signed_seer_api.py b/src/sentry/seer/signed_seer_api.py
index ffe8718d0daa..0ba8fb954f90 100644
--- a/src/sentry/seer/signed_seer_api.py
+++ b/src/sentry/seer/signed_seer_api.py
@@ -117,7 +117,9 @@ def _resolve_viewer_context(
         org_id = explicit_org_id
 
     if explicit_user_id is not None:
-        if user_id is not None and user_id != explicit_user_id:
+        # A service account is its own principal; never re-attribute it to a human.
+        is_service_account = actor.type == ActorType.SERVICE_ACCOUNT
+        if (user_id is not None or is_service_account) and user_id != explicit_user_id:
             logger.warning(
                 "seer.viewer_context_mismatch",
                 extra={
@@ -132,7 +134,7 @@ def _resolve_viewer_context(
             actor = replace(actor, actor_id=explicit_user_id)
         elif actor.type == ActorType.AGENT:
             actor = replace(actor, delegated_user_id=explicit_user_id)
-        else:
+        elif not is_service_account:
             actor = Actor(type=ActorType.USER, actor_id=explicit_user_id)
 
     metrics.incr(
diff --git a/tests/sentry/seer/test_signed_seer_api.py b/tests/sentry/seer/test_signed_seer_api.py
index bc663e930b8d..f80fc3c70e2e 100644
--- a/tests/sentry/seer/test_signed_seer_api.py
+++ b/tests/sentry/seer/test_signed_seer_api.py
@@ -350,6 +350,28 @@ def test_agent_mismatch_warns_and_keeps_agent(self, mock_logger: MagicMock) -> N
             "user_id",
         }
 
+    @patch("sentry.seer.signed_seer_api.logger")
+    def test_service_account_is_not_reattributed_to_user(self, mock_logger: MagicMock) -> None:
+        ctx = ViewerContext(
+            actor=Actor(
+                type=ActorType.SERVICE_ACCOUNT,
+                actor_id=5,
+                superuser=SuperuserAccess(expires_at=1234567890),
+            ),
+            organization_id=42,
+            project_id=3,
+        )
+        with viewer_context_scope(ctx):
+            result = _resolve_viewer_context(SeerViewerContext(organization_id=42, user_id=99))
+
+        assert isinstance(result, ViewerContext)
+        assert result.actor.type == ActorType.SERVICE_ACCOUNT
+        assert result.actor.actor_id == 5
+        assert result.actor.superuser is None
+        assert result.project_id is None
+        mock_logger.warning.assert_called_once()
+        assert mock_logger.warning.call_args[1]["extra"]["field"] == "user_id"
+
     @patch("sentry.seer.signed_seer_api.metrics")
     def test_match_emits_metric_with_project_id(self, mock_metrics: MagicMock) -> None:
         ctx = ViewerContext(