diff --git a/ci/main.go b/ci/main.go
index a7b8423..b167724 100644
--- a/ci/main.go
+++ b/ci/main.go
@@ -539,7 +539,7 @@ func (m *Ci) TestBackend(ctx context.Context) (string, error) {
 	return m.WithStalwart(m.setup(m.backendSrc())).
 		WithExec([]string{"/bin/bash", "-c",
 			`tmp=$(mktemp); trap 'rm -f "$tmp"' EXIT; ` +
-				`flutter test --concurrency=1 --reporter expanded --no-pub test/backend >"$tmp" 2>&1 || { cat "$tmp"; exit 1; }; ` +
+				`flutter test --concurrency=1 --reporter expanded --no-pub --exclude-tags=nightly test/backend >"$tmp" 2>&1 || { cat "$tmp"; exit 1; }; ` +
 				`grep -E '^All [0-9]+ tests passed' "$tmp" || tail -1 "$tmp"`}).
 		Stdout(ctx)
 }
@@ -570,7 +570,7 @@ func (m *Ci) ChaosMonkeyBackend(ctx context.Context) (string, error) {
 	return m.WithStalwart(m.setup(m.backendSrc())).
 		WithExec([]string{"/bin/bash", "-c",
 			`tmp=$(mktemp); trap 'rm -f "$tmp"' EXIT; ` +
-				`flutter test test/backend/chaos_monkey_test.dart --reporter expanded --concurrency=1 --no-pub >"$tmp" 2>&1 || { cat "$tmp"; exit 1; }; ` +
+				`flutter test test/backend/chaos_monkey_test.dart --reporter expanded --concurrency=1 --no-pub --tags=nightly >"$tmp" 2>&1 || { cat "$tmp"; exit 1; }; ` +
 				`grep -E '^All [0-9]+ tests passed' "$tmp" || tail -1 "$tmp"`}).
 		Stdout(ctx)
 }
diff --git a/test/backend/chaos_monkey_test.dart b/test/backend/chaos_monkey_test.dart
index f6715a4..94e1285 100644
--- a/test/backend/chaos_monkey_test.dart
+++ b/test/backend/chaos_monkey_test.dart
@@ -10,6 +10,9 @@
 //   CHAOS_ROUNDS  (default: 30) — number of random operations to perform
 //   CHAOS_SEED    (default: current epoch ms) — seed for reproducibility
 
+@Tags(['nightly'])
+library;
+
 import 'dart:io';
 import 'dart:math';