fix(sync): fail loud when uvc rebuild disappears

Cargo.lock

@@ -1642,7 +1642,7 @@ checksum = "09edd9e8b54e49e587e4f6295a7d29c3ea94d469cb40ab8ca70b288248a81db2"
 
 [[package]]
 name = "lesavka_client"
-version = "0.14.22"
+version = "0.14.23"
 dependencies = [
  "anyhow",
  "async-stream",
@@ -1676,7 +1676,7 @@ dependencies = [
 
 [[package]]
 name = "lesavka_common"
-version = "0.14.22"
+version = "0.14.23"
 dependencies = [
  "anyhow",
  "base64",
@@ -1688,7 +1688,7 @@ dependencies = [
 
 [[package]]
 name = "lesavka_server"
-version = "0.14.22"
+version = "0.14.23"
 dependencies = [
  "anyhow",
  "base64",

client/Cargo.toml

@@ -4,7 +4,7 @@ path                    = "src/main.rs"
 
 [package]
 name                    = "lesavka_client"
-version                 = "0.14.22"
+version                 = "0.14.23"
 edition                 = "2024"
 
 [dependencies]

common/Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name                    = "lesavka_common"
-version                 = "0.14.22"
+version                 = "0.14.23"
 edition                 = "2024"
 build                   = "build.rs"
 

scripts/install/server.sh

@@ -38,6 +38,57 @@ LESAVKA_UVC_MAXBURST=${LESAVKA_UVC_MAXBURST:-0}
 EOF
 }
 
+find_uvc_output_node() {
+  local by_path_root=/dev/v4l/by-path
+  local ctrl=""
+  ctrl=$(ls /sys/class/udc 2>/dev/null | head -n1 || true)
+  if [[ -n $ctrl && -e "$by_path_root/platform-$ctrl-video-index0" ]]; then
+    printf '%s\n' "$by_path_root/platform-$ctrl-video-index0"
+    return 0
+  fi
+
+  local candidate
+  shopt -s nullglob
+  for candidate in "$by_path_root"/platform-*-video-index0; do
+    printf '%s\n' "$candidate"
+    shopt -u nullglob
+    return 0
+  done
+  shopt -u nullglob
+  return 1
+}
+
+wait_for_uvc_output_node() {
+  local node=""
+  for _ in {1..50}; do
+    if node=$(find_uvc_output_node); then
+      printf '%s\n' "$node"
+      return 0
+    fi
+    sleep 0.1
+  done
+  return 1
+}
+
+validate_uvc_gadget_ready() {
+  if [[ -n ${LESAVKA_DISABLE_UVC:-} ]]; then
+    return 0
+  fi
+
+  if [[ ! -d /sys/kernel/config/usb_gadget/lesavka/functions/uvc.usb0 ]]; then
+    echo "❌ UVC gadget function is missing after rebuild; refusing to continue with a half-applied install." >&2
+    return 1
+  fi
+
+  local node=""
+  if ! node=$(wait_for_uvc_output_node); then
+    echo "❌ UVC gadget video-output node did not appear after rebuild; refusing to continue." >&2
+    return 1
+  fi
+
+  echo "✅  UVC gadget output ready at ${node}"
+}
+
 udc_state() {
   local udc=""
   udc=$(ls /sys/class/udc 2>/dev/null | head -n1 || true)
@@ -603,7 +654,7 @@ if [[ -n ${LESAVKA_ALLOW_GADGET_RESET:-} ]] || [[ "$FORCE_GADGET_REBUILD" == "1"
     LESAVKA_ATTACH_WRITE_UDC=1 \
     LESAVKA_DETACH_CLEAR_UDC=1 \
     LESAVKA_RELOAD_UVCVIDEO=1 \
-    LESAVKA_UVC_FALLBACK=1 \
+    LESAVKA_UVC_FALLBACK=0 \
     LESAVKA_UVC_CODEC="${LESAVKA_UVC_CODEC:-mjpeg}" \
     /usr/local/bin/lesavka-core.sh
   sudo systemctl restart lesavka-core
@@ -656,6 +707,8 @@ else
   echo "⚠️  lesavka-uvc is not active; start via lesavka-core dependency path."
 fi
 
+validate_uvc_gadget_ready
+
 sudo systemctl restart lesavka-server
 INSTALLED_VERSION=$(manifest_package_version "$SRC_DIR/server/Cargo.toml" 2>/dev/null || true)
 INSTALLED_SHA=$(git -C "$SCRIPT_REPO_ROOT" rev-parse --short HEAD 2>/dev/null || true)

server/Cargo.toml

@@ -10,7 +10,7 @@ bench                   = false
 
 [package]
 name                    = "lesavka_server"
-version                 = "0.14.22"
+version                 = "0.14.23"
 edition                 = "2024"
 autobins                = false
 

testing/tests/server_install_script_contract.rs

@@ -57,6 +57,18 @@ fn server_install_pins_hdmi_camera_and_display_defaults() {
         !SERVER_INSTALL.contains("Environment=LESAVKA_UVC_CODEC=mjpeg"),
         "install script should not pin UVC codec to mjpeg in the systemd units"
     );
+    assert!(
+        SERVER_INSTALL.contains("LESAVKA_UVC_FALLBACK=0"),
+        "forced gadget rebuilds should fail loud instead of silently dropping UVC"
+    );
+    assert!(
+        SERVER_INSTALL.contains("validate_uvc_gadget_ready"),
+        "install script should verify that the UVC gadget comes back before declaring success"
+    );
+    assert!(
+        SERVER_INSTALL.contains("video-output node did not appear after rebuild"),
+        "install script should explain why it refuses a half-applied UVC install"
+    );
 }
 
 #[test]