diff --git a/core/soong_config.mk b/core/soong_config.mk
index cdd2896..fea0465 100644
--- a/core/soong_config.mk
+++ b/core/soong_config.mk
@@ -34,7 +34,8 @@
 	echo '    "Make_suffix": "-$(TARGET_PRODUCT)",'; \
 	echo ''; \
 	echo '    "Platform_sdk_version": $(PLATFORM_SDK_VERSION),'; \
-	echo '    "Platform_version_all_codenames": $(call csv_to_json_list,$(PLATFORM_VERSION_ALL_CODENAMES)),'; \
+	echo '    "Platform_version_active_codenames": $(call csv_to_json_list,$(PLATFORM_VERSION_ALL_CODENAMES)),'; \
+	echo '    "Platform_version_future_codenames": $(call csv_to_json_list,$(PLATFORM_VERSION_FUTURE_CODENAMES)),'; \
 	echo '    "Unbundled_build": $(if $(TARGET_BUILD_APPS),true,false),'; \
 	echo '    "Brillo": $(if $(BRILLO),true,false),'; \
 	echo '    "Malloc_not_svelte": $(if $(filter true,$(MALLOC_SVELTE)),false,true),'; \
diff --git a/core/version_defaults.mk b/core/version_defaults.mk
index 3506fff..083e01b 100644
--- a/core/version_defaults.mk
+++ b/core/version_defaults.mk
@@ -129,14 +129,17 @@
     PLATFORM_VERSION_CODENAME := $(TARGET_PLATFORM_VERSION)
   endif
 
-  # This is all of the development codenames that are active.  Should be either
-  # the same as PLATFORM_VERSION_CODENAME or a comma-separated list of additional
-  # codenames after PLATFORM_VERSION_CODENAME.
+  # This is all of the *active* development codenames. There are future
+  # codenames not included in this list. This confusing name is needed because
+  # all_codenames has been baked into build.prop for ages.
+  #
+  # Should be either the same as PLATFORM_VERSION_CODENAME or a comma-separated
+  # list of additional codenames after PLATFORM_VERSION_CODENAME.
   PLATFORM_VERSION_ALL_CODENAMES :=
 
-  # Build a list of all possible code names. Avoid duplicates, and stop when we
+  # Build a list of all active code names. Avoid duplicates, and stop when we
   # reach a codename that matches PLATFORM_VERSION_CODENAME (anything beyond
-  # that is not included in our build.
+  # that is not included in our build).
   _versions_in_target := \
     $(call find_and_earlier,$(ALL_VERSIONS),$(TARGET_PLATFORM_VERSION))
   $(foreach version,$(_versions_in_target),\
@@ -144,9 +147,23 @@
     $(if $(filter $(_codename),$(PLATFORM_VERSION_ALL_CODENAMES)),,\
       $(eval PLATFORM_VERSION_ALL_CODENAMES += $(_codename))))
 
+  # This is all of the inactive development codenames. Available to be targeted
+  # in this branch but in the future relative to our current target.
+  PLATFORM_VERSION_FUTURE_CODENAMES :=
+
+  # Build a list of all untargeted code names. Avoid duplicates.
+  _versions_not_in_target := \
+    $(filter-out $(PLATFORM_VERSION_ALL_CODENAMES),$(ALL_VERSIONS))
+  $(foreach version,$(_versions_not_in_target),\
+    $(eval _codename := $(PLATFORM_VERSION_CODENAME.$(version)))\
+    $(if $(filter $(_codename),$(PLATFORM_VERSION_FUTURE_CODENAMES)),,\
+      $(eval PLATFORM_VERSION_FUTURE_CODENAMES += $(_codename))))
+
   # And convert from space separated to comma separated.
   PLATFORM_VERSION_ALL_CODENAMES := \
     $(subst $(space),$(comma),$(strip $(PLATFORM_VERSION_ALL_CODENAMES)))
+  PLATFORM_VERSION_FUTURE_CODENAMES := \
+    $(subst $(space),$(comma),$(strip $(PLATFORM_VERSION_FUTURE_CODENAMES)))
 
 endif