diff --git a/core/board_config.mk b/core/board_config.mk
index b7ca3a4..f29f760 100644
--- a/core/board_config.mk
+++ b/core/board_config.mk
@@ -989,6 +989,21 @@
 endif
 
 ###########################################
+# BOARD_API_LEVEL for vendor API surface
+ifdef RELEASE_BOARD_API_LEVEL
+  ifdef BOARD_API_LEVEL
+    $(error BOARD_API_LEVEL must not set manully. The build system automatically sets this value.)
+  endif
+  BOARD_API_LEVEL := $(RELEASE_BOARD_API_LEVEL)
+  .KATI_READONLY := BOARD_API_LEVEL
+
+  ifdef RELEASE_BOARD_API_LEVEL_FROZEN
+    BOARD_API_LEVEL_FROZEN := true
+    .KATI_READONLY := BOARD_API_LEVEL_FROZEN
+  endif
+endif
+
+###########################################
 # Handle BUILD_BROKEN_USES_BUILD_*
 
 $(foreach m,$(DEFAULT_WARNING_BUILD_MODULE_TYPES),\
diff --git a/core/main.mk b/core/main.mk
index 3f5f766..7b52f82 100644
--- a/core/main.mk
+++ b/core/main.mk
@@ -293,16 +293,22 @@
 
 # Vendors with GRF must define BOARD_SHIPPING_API_LEVEL for the vendor API level.
 # This must not be defined for the non-GRF devices.
+# The values of the GRF properties will be verified by post_process_props.py
 ifdef BOARD_SHIPPING_API_LEVEL
 ADDITIONAL_VENDOR_PROPERTIES += \
     ro.board.first_api_level=$(BOARD_SHIPPING_API_LEVEL)
+endif
 
-# To manually set the vendor API level of the vendor modules, BOARD_API_LEVEL can be used.
-# The values of the GRF properties will be verified by post_process_props.py
+# Build system set BOARD_API_LEVEL to show the api level of the vendor API surface.
+# This must not be altered outside of build system.
 ifdef BOARD_API_LEVEL
 ADDITIONAL_VENDOR_PROPERTIES += \
     ro.board.api_level=$(BOARD_API_LEVEL)
 endif
+# BOARD_API_LEVEL_FROZEN is true when the vendor API surface is frozen.
+ifdef BOARD_API_LEVEL_FROZEN
+ADDITIONAL_VENDOR_PROPERTIES += \
+    ro.board.api_frozen=$(BOARD_API_LEVEL_FROZEN)
 endif
 
 # Set build prop. This prop is read by ota_from_target_files when generating OTA,