diff --git a/.config/nextest.toml b/.config/nextest.toml
index 4645eb725f..bfebd1bc86 100644
--- a/.config/nextest.toml
+++ b/.config/nextest.toml
@@ -1,11 +1,22 @@
 [test-groups.navigation-child-browser-runtime]
 max-threads = 1
 
+# These cases intentionally exercise the process-level OS resolver. Running
+# several together can make the external resolver exceed their existing
+# contract timeout even though each request completes promptly in isolation.
+[test-groups.external-dns-failure-runtime]
+max-threads = 1
+
 [[profile.default.overrides]]
 filter = 'package(moli-core) & binary(wpt_compat) & test(/navigation_child_browsing_context/)'
 test-group = 'navigation-child-browser-runtime'
 threads-required = "num-test-threads"
 
+[[profile.default.overrides]]
+filter = 'package(moli-renderer-v8) & test(/dns_failure/)'
+test-group = 'external-dns-failure-runtime'
+threads-required = "num-test-threads"
+
 [profile.ci]
 fail-fast = false
 retries = 2
@@ -17,3 +28,8 @@ success-output = "never"
 filter = 'package(moli-core) & binary(wpt_compat) & test(/navigation_child_browsing_context/)'
 test-group = 'navigation-child-browser-runtime'
 threads-required = "num-test-threads"
+
+[[profile.ci.overrides]]
+filter = 'package(moli-renderer-v8) & test(/dns_failure/)'
+test-group = 'external-dns-failure-runtime'
+threads-required = "num-test-threads"