diff --git a/scripts/install/server.sh b/scripts/install/server.sh
index df269af..d145402 100755
--- a/scripts/install/server.sh
+++ b/scripts/install/server.sh
@@ -251,6 +251,44 @@ run_as_user() {
   sudo -u "$ORIG_USER" env HOME="$USER_HOME" SSH_AUTH_SOCK="${SSH_AUTH_SOCK:-}" "$@"
 }
 
+CAPTURE_DISCOVERY_RELAY_PRESENT=0
+CAPTURE_DISCOVERY_RELAY_WAS_ACTIVE=0
+CAPTURE_DISCOVERY_POWER_BORROWED=0
+
+prepare_capture_power_for_discovery() {
+  if ! systemctl list-unit-files | grep -q '^relay.service'; then
+    return 0
+  fi
+
+  CAPTURE_DISCOVERY_RELAY_PRESENT=1
+  if systemctl is-active --quiet relay.service; then
+    CAPTURE_DISCOVERY_RELAY_WAS_ACTIVE=1
+    return 0
+  fi
+
+  echo "   ↪ borrowing relay GPIO power for capture discovery"
+  sudo systemctl start relay.service
+  CAPTURE_DISCOVERY_POWER_BORROWED=1
+  sudo udevadm settle --timeout=10 || true
+  sleep 2
+}
+
+restore_capture_power_after_discovery() {
+  if [ "${CAPTURE_DISCOVERY_RELAY_PRESENT:-0}" -eq 0 ]; then
+    return 0
+  fi
+  if [ "${CAPTURE_DISCOVERY_POWER_BORROWED:-0}" -eq 0 ]; then
+    return 0
+  fi
+  if [ "${CAPTURE_DISCOVERY_RELAY_WAS_ACTIVE:-0}" -ne 0 ]; then
+    return 0
+  fi
+
+  echo "   ↪ returning relay GPIO power control to Lesavka auto mode"
+  sudo systemctl stop relay.service || true
+  CAPTURE_DISCOVERY_POWER_BORROWED=0
+}
+
 while [[ $# -gt 0 ]]; do
   case $1 in
     -r|--ref) REF="$2"; shift 2 ;;
@@ -314,11 +352,8 @@ EOF
 prepare_hdmi_detection_boot_state
 
 echo "==> 2b. Predictable /dev names for each capture card"
-# ensure relay (GPIO power) is on if present
-if systemctl list-unit-files | grep -q '^relay.service'; then
-  sudo systemctl enable --now relay.service
-  sleep 2
-fi
+prepare_capture_power_for_discovery
+trap restore_capture_power_after_discovery EXIT
 
 discover_gc_capture_pairs() {
     for dev in /dev/video*; do
@@ -378,6 +413,8 @@ EOF
         sudo udevadm settle
     fi
 fi
+restore_capture_power_after_discovery
+trap - EXIT
 
 echo "==> 3. Rust toolchain"
 sudo rustup default stable
diff --git a/testing/tests/server_install_script_contract.rs b/testing/tests/server_install_script_contract.rs
index 58ee426..97b4f51 100644
--- a/testing/tests/server_install_script_contract.rs
+++ b/testing/tests/server_install_script_contract.rs
@@ -74,6 +74,18 @@ fn server_install_builds_eye_links_from_capture_nodes_only() {
         SERVER_INSTALL.contains("for _ in {1..20}; do"),
         "install script should wait briefly for both GC311 capture nodes to finish enumerating"
     );
+    assert!(
+        SERVER_INSTALL.contains("borrowing relay GPIO power for capture discovery"),
+        "install script should temporarily power capture cards for discovery when relay GPIO is available"
+    );
+    assert!(
+        SERVER_INSTALL.contains("returning relay GPIO power control to Lesavka auto mode"),
+        "install script should restore relay power control after capture discovery"
+    );
+    assert!(
+        SERVER_INSTALL.contains("trap restore_capture_power_after_discovery EXIT"),
+        "install script should restore borrowed capture power even if discovery exits early"
+    );
     assert!(
         SERVER_INSTALL.contains("[ \"$LEFT_TAG\" = \"$RIGHT_TAG\" ]"),
         "install script should refuse duplicated path tags instead of assigning both eyes to one card"