diff --git a/core/Makefile b/core/Makefile
index 7cd055e..ca95424 100644
--- a/core/Makefile
+++ b/core/Makefile
@@ -241,8 +241,8 @@
 	BUILD_VERSION_TAGS="$(BUILD_VERSION_TAGS)" \
 	DATE="$(DATE_FROM_FILE)" \
 	PLATFORM_SDK_VERSION="$(PLATFORM_SDK_VERSION)" \
+	PLATFORM_VERSION_LAST_STABLE="$(PLATFORM_VERSION_LAST_STABLE)" \
 	PLATFORM_VERSION="$(PLATFORM_VERSION)" \
-	PLATFORM_VERSION_LAST_STABLE="$(PLATFORM_VERSION)" \
 	TARGET_BUILD_TYPE="$(TARGET_BUILD_VARIANT)" \
 	bash $(BUILDINFO_COMMON_SH) "$(1)" >> $(2)
 endef
@@ -447,7 +447,7 @@
 	        BUILD_NUMBER="$(BUILD_NUMBER_FROM_FILE)" \
 	        BOARD_BUILD_SYSTEM_ROOT_IMAGE="$(BOARD_BUILD_SYSTEM_ROOT_IMAGE)" \
 	        PLATFORM_VERSION="$(PLATFORM_VERSION)" \
-	        PLATFORM_VERSION_LAST_STABLE="$(PLATFORM_VERSION)" \
+	        PLATFORM_VERSION_LAST_STABLE="$(PLATFORM_VERSION_LAST_STABLE)" \
 	        PLATFORM_SECURITY_PATCH="$(PLATFORM_SECURITY_PATCH)" \
 	        PLATFORM_BASE_OS="$(PLATFORM_BASE_OS)" \
 	        PLATFORM_SDK_VERSION="$(PLATFORM_SDK_VERSION)" \
@@ -1121,7 +1121,7 @@
 endif
 
 INTERNAL_MKBOOTIMG_VERSION_ARGS := \
-    --os_version $(PLATFORM_VERSION) \
+    --os_version $(PLATFORM_VERSION_LAST_STABLE) \
     --os_patch_level $(PLATFORM_SECURITY_PATCH)
 
 # Define these only if we are building boot
@@ -3217,22 +3217,22 @@
 
 BOARD_AVB_SYSTEM_ADD_HASHTREE_FOOTER_ARGS += \
     --prop com.android.build.system.fingerprint:$(BUILD_FINGERPRINT_FROM_FILE) \
-    --prop com.android.build.system.os_version:$(PLATFORM_VERSION) \
+    --prop com.android.build.system.os_version:$(PLATFORM_VERSION_LAST_STABLE) \
     --prop com.android.build.system.security_patch:$(PLATFORM_SECURITY_PATCH)
 
 BOARD_AVB_PRODUCT_ADD_HASHTREE_FOOTER_ARGS += \
     --prop com.android.build.product.fingerprint:$(BUILD_FINGERPRINT_FROM_FILE) \
-    --prop com.android.build.product.os_version:$(PLATFORM_VERSION) \
+    --prop com.android.build.product.os_version:$(PLATFORM_VERSION_LAST_STABLE) \
     --prop com.android.build.product.security_patch:$(PLATFORM_SECURITY_PATCH)
 
 BOARD_AVB_SYSTEM_EXT_ADD_HASHTREE_FOOTER_ARGS += \
     --prop com.android.build.system_ext.fingerprint:$(BUILD_FINGERPRINT_FROM_FILE) \
-    --prop com.android.build.system_ext.os_version:$(PLATFORM_VERSION) \
+    --prop com.android.build.system_ext.os_version:$(PLATFORM_VERSION_LAST_STABLE) \
     --prop com.android.build.system_ext.security_patch:$(PLATFORM_SECURITY_PATCH)
 
 BOARD_AVB_BOOT_ADD_HASH_FOOTER_ARGS += \
     --prop com.android.build.boot.fingerprint:$(BUILD_FINGERPRINT_FROM_FILE) \
-    --prop com.android.build.boot.os_version:$(PLATFORM_VERSION)
+    --prop com.android.build.boot.os_version:$(PLATFORM_VERSION_LAST_STABLE)
 
 BOARD_AVB_VENDOR_BOOT_ADD_HASH_FOOTER_ARGS += \
     --prop com.android.build.vendor_boot.fingerprint:$(BUILD_FINGERPRINT_FROM_FILE) \
@@ -3242,11 +3242,11 @@
 
 BOARD_AVB_VENDOR_ADD_HASHTREE_FOOTER_ARGS += \
     --prop com.android.build.vendor.fingerprint:$(BUILD_FINGERPRINT_FROM_FILE) \
-    --prop com.android.build.vendor.os_version:$(PLATFORM_VERSION)
+    --prop com.android.build.vendor.os_version:$(PLATFORM_VERSION_LAST_STABLE)
 
 BOARD_AVB_ODM_ADD_HASHTREE_FOOTER_ARGS += \
     --prop com.android.build.odm.fingerprint:$(BUILD_FINGERPRINT_FROM_FILE) \
-    --prop com.android.build.odm.os_version:$(PLATFORM_VERSION)
+    --prop com.android.build.odm.os_version:$(PLATFORM_VERSION_LAST_STABLE)
 
 BOARD_AVB_DTBO_ADD_HASH_FOOTER_ARGS += \
     --prop com.android.build.dtbo.fingerprint:$(BUILD_FINGERPRINT_FROM_FILE)
diff --git a/core/version_defaults.mk b/core/version_defaults.mk
index c32cab8..a989895 100644
--- a/core/version_defaults.mk
+++ b/core/version_defaults.mk
@@ -84,38 +84,17 @@
 # generate the range of allowed SDK versions, so it must have an entry for every
 # unreleased API level targetable by this branch, not just those that are valid
 # lunch targets for this branch.
-PLATFORM_VERSION.RP1A := R
+
+# The last stable version name of the platform that was released.  During
+# development, this stays at that previous version, while the codename indicates
+# further work based on the previous version.
+PLATFORM_VERSION_LAST_STABLE := 10
+.KATI_READONLY := PLATFORM_VERSION_LAST_STABLE
 
 # These are the current development codenames, if the build is not a final
 # release build.  If this is a final release build, it is simply "REL".
 PLATFORM_VERSION_CODENAME.RP1A := R
 
-ifndef PLATFORM_VERSION
-  PLATFORM_VERSION := $(PLATFORM_VERSION.$(TARGET_PLATFORM_VERSION))
-  ifndef PLATFORM_VERSION
-    # PLATFORM_VERSION falls back to TARGET_PLATFORM_VERSION
-    PLATFORM_VERSION := $(TARGET_PLATFORM_VERSION)
-  endif
-endif
-.KATI_READONLY := PLATFORM_VERSION
-
-ifndef PLATFORM_SDK_VERSION
-  # This is the canonical definition of the SDK version, which defines
-  # the set of APIs and functionality available in the platform.  It
-  # is a single integer that increases monotonically as updates to
-  # the SDK are released.  It should only be incremented when the APIs for
-  # the new release are frozen (so that developers don't write apps against
-  # intermediate builds).  During development, this number remains at the
-  # SDK version the branch is based on and PLATFORM_VERSION_CODENAME holds
-  # the code-name of the new development work.
-
-  # When you increment the PLATFORM_SDK_VERSION please ensure you also
-  # clear out the following text file of all older PLATFORM_VERSION's:
-  # cts/tests/tests/os/assets/platform_versions.txt
-  PLATFORM_SDK_VERSION := 29
-endif
-.KATI_READONLY := PLATFORM_SDK_VERSION
-
 ifndef PLATFORM_VERSION_CODENAME
   PLATFORM_VERSION_CODENAME := $(PLATFORM_VERSION_CODENAME.$(TARGET_PLATFORM_VERSION))
   ifndef PLATFORM_VERSION_CODENAME
@@ -165,6 +144,32 @@
   PLATFORM_VERSION_ALL_CODENAMES \
   PLATFORM_VERSION_FUTURE_CODENAMES
 
+ifndef PLATFORM_VERSION
+  ifeq (REL,$(PLATFORM_VERSION_CODENAME))
+      PLATFORM_VERSION := $(PLATFORM_VERSION_LAST_STABLE)
+  else
+      PLATFORM_VERSION := $(PLATFORM_VERSION_CODENAME)
+  endif
+endif
+.KATI_READONLY := PLATFORM_VERSION
+
+ifndef PLATFORM_SDK_VERSION
+  # This is the canonical definition of the SDK version, which defines
+  # the set of APIs and functionality available in the platform.  It
+  # is a single integer that increases monotonically as updates to
+  # the SDK are released.  It should only be incremented when the APIs for
+  # the new release are frozen (so that developers don't write apps against
+  # intermediate builds).  During development, this number remains at the
+  # SDK version the branch is based on and PLATFORM_VERSION_CODENAME holds
+  # the code-name of the new development work.
+
+  # When you increment the PLATFORM_SDK_VERSION please ensure you also
+  # clear out the following text file of all older PLATFORM_VERSION's:
+  # cts/tests/tests/os/assets/platform_versions.txt
+  PLATFORM_SDK_VERSION := 29
+endif
+.KATI_READONLY := PLATFORM_SDK_VERSION
+
 ifeq (REL,$(PLATFORM_VERSION_CODENAME))
   PLATFORM_PREVIEW_SDK_VERSION := 0
 else