diff --git a/tests/quickshell/settings-commit-reset-contract.sh b/tests/quickshell/settings-commit-reset-contract.sh
index a1e4352..21bf264 100755
--- a/tests/quickshell/settings-commit-reset-contract.sh
+++ b/tests/quickshell/settings-commit-reset-contract.sh
@@ -61,6 +61,26 @@ restore() {
 }
 trap restore EXIT
 
+# This contract shares its harness file with settings-hyprland-write-contract,
+# and Quickshell identifies an instance by config path -- so if that run's
+# instance is still alive, the IPC wait below is satisfied by ITS target. That
+# direction is the dangerous one: this contract believes the compositor seam is
+# stubbed, so it would happily drive the DAILY DESKTOP's real compositor while
+# reporting isolation. Refuse to start rather than find out.
+harness_instances() {
+    # rg -c prints nothing when there are no matches, so an unguarded
+    # substitution yields "" rather than "0".
+    local count
+    count="$(qs list 2>/dev/null | rg -c "^  Config path: $harness\$" || true)"
+    printf '%s' "${count:-0}"
+}
+for _ in $(seq 1 50); do
+    [[ "$(harness_instances)" == "0" ]] && break
+    sleep 0.1
+done
+[[ "$(harness_instances)" == "0" ]] \
+    || fail 'another instance of the settings harness is still running -- this contract would drive it instead of its own isolated one, and that instance may be writing to the real compositor'
+
 XDG_CONFIG_HOME="$config_home" XDG_STATE_HOME="$state_home" \
     PANAMA_SETTINGS_TEST_ISOLATE_COMPOSITOR=1 qs -p "$harness" --daemonize >/dev/null
 for _ in $(seq 1 40); do
diff --git a/tests/quickshell/settings-hyprland-write-contract.sh b/tests/quickshell/settings-hyprland-write-contract.sh
index 9fa9ad0..d69846f 100755
--- a/tests/quickshell/settings-hyprland-write-contract.sh
+++ b/tests/quickshell/settings-hyprland-write-contract.sh
@@ -77,6 +77,32 @@ target_auto_hdr_int=$([[ "$target_auto_hdr" == true ]] && printf 1 || printf 0)
 target_vrr=$([[ "$original_vrr" == 3 ]] && printf 0 || printf 3)
 target_direct=$([[ "$original_direct" == 2 ]] && printf 0 || printf 2)
 
+# settings-commit-reset-contract drives the SAME harness file with
+# PANAMA_SETTINGS_TEST_ISOLATE_COMPOSITOR=1, where the compositor write seam is
+# stubbed out. Quickshell identifies an instance by its config path, so if that
+# run's instance has not fully exited, the `ipc show` wait below is satisfied by
+# ITS target -- and every write in this contract lands on the isolated instance
+# and never reaches the compositor. That is exactly what "a typed batch did not
+# reach the compositor" looks like when this fails in a full suite run but
+# passes on its own.
+#
+# So wait for the harness to be clear first, and say so plainly if it is not,
+# rather than silently talking to the wrong shell.
+harness_instances() {
+    # rg -c prints nothing at all when there are no matches, so an unguarded
+    # substitution yields "" rather than "0" and every comparison against a
+    # count fails.
+    local count
+    count="$(qs list 2>/dev/null | rg -c "^  Config path: $harness\$" || true)"
+    printf '%s' "${count:-0}"
+}
+for _ in $(seq 1 50); do
+    [[ "$(harness_instances)" == "0" ]] && break
+    sleep 0.1
+done
+[[ "$(harness_instances)" == "0" ]] \
+    || fail 'another instance of the settings harness is still running -- this contract would talk to it instead of its own, and its writes may be deliberately stubbed'
+
 XDG_CONFIG_HOME="$config_home" qs -p "$harness" --daemonize >/dev/null
 for _ in $(seq 1 40); do
     if qs_for_harness ipc show 2>/dev/null | rg -q '^target settings-system-test$'; then