diff --git a/core/Makefile b/core/Makefile
index 79c8a17..09c815e 100644
--- a/core/Makefile
+++ b/core/Makefile
@@ -1167,13 +1167,16 @@
 .PHONY: bootimage_16k
 
 BUILT_BOOT_OTA_PACKAGE_16K := $(PRODUCT_OUT)/boot_ota_16k.zip
-$(BUILT_BOOT_OTA_PACKAGE_16K): $(OTA_FROM_RAW_IMG) $(BUILT_BOOTIMAGE_16K_TARGET) $(DEFAULT_SYSTEM_DEV_CERTIFICATE).pk8
+$(BUILT_BOOT_OTA_PACKAGE_16K): $(OTA_FROM_RAW_IMG) $(BUILT_BOOTIMAGE_16K_TARGET) $(INSTALLED_BOOTIMAGE_TARGET) $(DEFAULT_SYSTEM_DEV_CERTIFICATE).pk8
 	$(OTA_FROM_RAW_IMG) --package_key $(DEFAULT_SYSTEM_DEV_CERTIFICATE) \
                       --max_timestamp `cat $(BUILD_DATETIME_FILE)` \
                       --path $(HOST_OUT) \
                       --partition_name boot \
                       --output $@ \
-                      $(BUILT_BOOTIMAGE_16K_TARGET)
+                      $(if $(BOARD_16K_OTA_USE_INCREMENTAL),\
+                        $(INSTALLED_BOOTIMAGE_TARGET):$(BUILT_BOOTIMAGE_16K_TARGET),\
+                        $(BUILT_BOOTIMAGE_16K_TARGET)\
+                      )
 
 boototapackage_16k: $(BUILT_BOOT_OTA_PACKAGE_16K)
 .PHONY: boototapackage_16k
@@ -1503,13 +1506,16 @@
 
 ifneq ($(BOARD_KERNEL_PATH_16K),)
 BUILT_BOOT_OTA_PACKAGE_4K := $(PRODUCT_OUT)/boot_ota_4k.zip
-$(BUILT_BOOT_OTA_PACKAGE_4K): $(OTA_FROM_RAW_IMG) $(INSTALLED_BOOTIMAGE_TARGET) $(DEFAULT_SYSTEM_DEV_CERTIFICATE).pk8
+$(BUILT_BOOT_OTA_PACKAGE_4K): $(OTA_FROM_RAW_IMG) $(INSTALLED_BOOTIMAGE_TARGET) $(BUILT_BOOTIMAGE_16K_TARGET) $(DEFAULT_SYSTEM_DEV_CERTIFICATE).pk8
 	$(OTA_FROM_RAW_IMG) --package_key $(DEFAULT_SYSTEM_DEV_CERTIFICATE) \
                       --max_timestamp `cat $(BUILD_DATETIME_FILE)` \
                       --path $(HOST_OUT) \
                       --partition_name boot \
                       --output $@ \
-                      $(INSTALLED_BOOTIMAGE_TARGET)
+                      $(if $(BOARD_16K_OTA_USE_INCREMENTAL),\
+                        $(BUILT_BOOTIMAGE_16K_TARGET):$(INSTALLED_BOOTIMAGE_TARGET),\
+                        $(INSTALLED_BOOTIMAGE_TARGET)\
+                      )
 
 boototapackage_4k: $(BUILT_BOOT_OTA_PACKAGE_4K)
 .PHONY: boototapackage_4k
diff --git a/core/envsetup.mk b/core/envsetup.mk
index 7ddbf32..cfb8a66 100644
--- a/core/envsetup.mk
+++ b/core/envsetup.mk
@@ -371,6 +371,8 @@
 TARGET_BUILD_TYPE := release
 endif
 
+include $(BUILD_SYSTEM)/product_validation_checks.mk
+
 # ---------------------------------------------------------------
 # figure out the output directories
 
diff --git a/core/product.mk b/core/product.mk
index 39c9eb7..07719e1 100644
--- a/core/product.mk
+++ b/core/product.mk
@@ -449,6 +449,8 @@
 
 _product_list_vars += PRODUCT_RELEASE_CONFIG_MAPS
 
+_product_list_vars += PRODUCT_VALIDATION_CHECKS
+
 .KATI_READONLY := _product_single_value_vars _product_list_vars
 _product_var_list :=$= $(_product_single_value_vars) $(_product_list_vars)
 
diff --git a/core/product_config.mk b/core/product_config.mk
index b475d75..3ee9654 100644
--- a/core/product_config.mk
+++ b/core/product_config.mk
@@ -420,6 +420,8 @@
 PRODUCT_EXTRA_OTA_KEYS := $(sort $(PRODUCT_EXTRA_OTA_KEYS))
 PRODUCT_EXTRA_RECOVERY_KEYS := $(sort $(PRODUCT_EXTRA_RECOVERY_KEYS))
 
+PRODUCT_VALIDATION_CHECKS := $(sort $(PRODUCT_VALIDATION_CHECKS))
+
 # Resolve and setup per-module dex-preopt configs.
 DEXPREOPT_DISABLED_MODULES :=
 # If a module has multiple setups, the first takes precedence.
diff --git a/core/product_validation_checks.mk b/core/product_validation_checks.mk
new file mode 100644
index 0000000..e0d976f
--- /dev/null
+++ b/core/product_validation_checks.mk
@@ -0,0 +1,72 @@
+# PRODUCT_VALIDATION_CHECKS allows you to enforce that your product config variables follow some
+# rules. To use it, add the paths to starlark configuration language (scl) files in
+# PRODUCT_VALIDATION_CHECKS. A validate_product_variables function in those files will be called
+# with a single "context" object.
+#
+# The context object currently 2 attributes:
+#   - product_variables: This has all the product variables. All the variables are either of type
+#                        string or list, more accurate typing (like bool) isn't known.
+#   - board_variables: This only has a small subset of the board variables, because there isn't a
+#                      known list of board variables. Feel free to expand the subset if you need a
+#                      new variable.
+#
+# You can then inspect (but not modify) these variables and fail() if they don't meet your
+# requirements. Example:
+#
+# In a product config file: PRODUCT_VALIDATION_CHECKS += //path/to/my_validations.scl
+# In my_validations.scl:
+# def validate_product_variables(ctx):
+#     for dir in ctx.board_variables.BOARD_SEPOLICY_DIRS:
+#         if not dir.startswith('system/sepolicy/'):
+#             fail('Only sepolicies in system/seplicy are allowed, found: ' + dir)
+
+ifdef PRODUCT_VALIDATION_CHECKS
+
+$(if $(filter-out //%.scl,$(PRODUCT_VALIDATION_CHECKS)), \
+	$(error All PRODUCT_VALIDATION_CHECKS files must start with // and end with .scl, exceptions: $(filter-out //%.scl,$(PRODUCT_VALIDATION_CHECKS))))
+
+known_board_variables := \
+  BOARD_VENDOR_SEPOLICY_DIRS BOARD_SEPOLICY_DIRS \
+  SYSTEM_EXT_PRIVATE_SEPOLICY_DIRS \
+  SYSTEM_EXT_PUBLIC_SEPOLICY_DIRS \
+  PRODUCT_PUBLIC_SEPOLICY_DIRS \
+  PRODUCT_PRIVATE_SEPOLICY_DIRS
+
+known_board_list_variables := \
+  BOARD_VENDOR_SEPOLICY_DIRS BOARD_SEPOLICY_DIRS \
+  SYSTEM_EXT_PRIVATE_SEPOLICY_DIRS \
+  SYSTEM_EXT_PUBLIC_SEPOLICY_DIRS \
+  PRODUCT_PUBLIC_SEPOLICY_DIRS \
+  PRODUCT_PRIVATE_SEPOLICY_DIRS
+
+escape_starlark_string=$(subst ",\",$(subst \,\\,$(1)))
+product_variable_starlark_value=$(if $(filter $(1),$(_product_list_vars) $(known_board_list_variables)),[$(foreach w,$($(1)),"$(call escape_starlark_string,$(w))", )],"$(call escape_starlark_string,$(1))")
+filename_to_starlark=$(subst -,_,$(subst /,_,$(subst .,_,$(1))))
+_c:=$(foreach f,$(PRODUCT_VALIDATION_CHECKS),$(newline)load("$(f)", validate_product_variables_$(call filename_to_starlark,$(f)) = "validate_product_variables"))
+# TODO: we should freeze the context because it contains mutable lists, so that validation checks can't affect each other
+_c+=$(newline)_ctx = struct(
+_c+=$(newline)product_variables = struct(
+_c+=$(foreach v,$(_product_var_list),$(newline)  $(v) = $(call product_variable_starlark_value,$(v)),)
+_c+=$(newline)),
+_c+=$(newline)board_variables = struct(
+_c+=$(foreach v,$(known_board_variables),$(newline)  $(v) = $(call product_variable_starlark_value,$(v)),)
+_c+=$(newline))
+_c+=$(newline))
+_c+=$(foreach f,$(PRODUCT_VALIDATION_CHECKS),$(newline)validate_product_variables_$(call filename_to_starlark,$(f))(_ctx))
+_c+=$(newline)variables_to_export_to_make = {}
+$(KATI_file_no_rerun >$(OUT_DIR)/product_validation_checks_entrypoint.scl,$(_c))
+filename_to_starlark:=
+escape_starlark_string:=
+product_variable_starlark_value:=
+known_board_variables :=
+known_board_list_variables :=
+
+# Exclude the entrypoint file as a dependency (by passing it as the 2nd argument) so that we don't
+# rerun kati every build. Even though we're using KATI_file_no_rerun, product config is run every
+# build, so the file will still be rewritten.
+#
+# We also need to pass --allow_external_entrypoint to rbcrun in case the OUT_DIR is set to something
+# outside of the source tree.
+$(call run-starlark,$(OUT_DIR)/product_validation_checks_entrypoint.scl,$(OUT_DIR)/product_validation_checks_entrypoint.scl,--allow_external_entrypoint)
+
+endif # ifdef PRODUCT_VALIDATION_CHECKS
diff --git a/core/release_config.bzl b/core/release_config.bzl
new file mode 120000
index 0000000..ffb70a3
--- /dev/null
+++ b/core/release_config.bzl
@@ -0,0 +1 @@
+release_config.scl
\ No newline at end of file
diff --git a/core/release_config.mk b/core/release_config.mk
index 5993e85..e1e0726 100644
--- a/core/release_config.mk
+++ b/core/release_config.mk
@@ -82,16 +82,6 @@
 )
 FLAG_DECLARATION_FILES :=
 
-# Make sure that the flag definitions are included for vendor/google builds.
-# This decouples the change in vendor/google/release/release_config_map.mk
-# from this logic change.
-# TODO: Remove this once the vendor/google FLAG_DECLARATION_FILES change is there.
-$(if $(wildcard vendor/google/release/release_config_map.mk),\
-  $(if $(filter vendor/google/release/build_flags.bzl,$(_flag_declaration_files)),,\
-    $(eval _flag_declaration_files := vendor/google/release/build_flags.bzl $(_flag_declaration_files)) \
-  ) \
-)
-
 # If TARGET_RELEASE is set, fail if there is no matching release config
 # If it isn't set, no release config files will be included and all flags
 # will get their default values.
diff --git a/core/release_config.bzl b/core/release_config.scl
similarity index 98%
rename from core/release_config.bzl
rename to core/release_config.scl
index a29f3f2..101f119 100644
--- a/core/release_config.bzl
+++ b/core/release_config.scl
@@ -15,7 +15,7 @@
 Export build flags (with values) to make.
 """
 
-load("//build/bazel/utils:schema_validation.bzl", "validate")
+load("//build/bazel/utils:schema_validation.scl", "validate")
 
 # Partitions that get build system flag summaries
 _flag_partitions = [
diff --git a/core/soong_config.mk b/core/soong_config.mk
index be6a795..e39f2fa 100644
--- a/core/soong_config.mk
+++ b/core/soong_config.mk
@@ -169,6 +169,11 @@
 $(call add_json_bool, VndkUseCoreVariant,                $(TARGET_VNDK_USE_CORE_VARIANT))
 $(call add_json_bool, VndkSnapshotBuildArtifacts,        $(VNDK_SNAPSHOT_BUILD_ARTIFACTS))
 
+$(call add_json_map,  BuildFlags)
+$(foreach flag,$(_ALL_RELEASE_FLAGS),\
+  $(call add_json_str,$(flag),$(_ALL_RELEASE_FLAGS.$(flag).VALUE)))
+$(call end_json_map)
+
 $(call add_json_bool, DirectedVendorSnapshot,            $(DIRECTED_VENDOR_SNAPSHOT))
 $(call add_json_map,  VendorSnapshotModules)
 $(foreach module,$(VENDOR_SNAPSHOT_MODULES),\
diff --git a/tools/rbcrun/host.go b/tools/rbcrun/host.go
index 1d68d43..7f5e332 100644
--- a/tools/rbcrun/host.go
+++ b/tools/rbcrun/host.go
@@ -31,11 +31,11 @@
 type ExecutionMode int
 const (
 	ExecutionModeRbc ExecutionMode = iota
-	ExecutionModeMake ExecutionMode = iota
+	ExecutionModeScl ExecutionMode = iota
 )
 
 const allowExternalEntrypointKey = "allowExternalEntrypoint"
-const callerDirKey = "callerDir"
+const callingFileKey = "callingFile"
 const executionModeKey = "executionMode"
 const shellKey = "shell"
 
@@ -58,7 +58,7 @@
 	"rblf_wildcard": starlark.NewBuiltin("rblf_wildcard", wildcard),
 }
 
-var makeBuiltins starlark.StringDict = starlark.StringDict{
+var sclBuiltins starlark.StringDict = starlark.StringDict{
 	"struct":   starlark.NewBuiltin("struct", starlarkstruct.Make),
 	"json": starlarkjson.Module,
 }
@@ -128,7 +128,8 @@
 			module = module[:pipePos]
 		}
 	}
-	modulePath, err := cleanModuleName(module, thread.Local(callerDirKey).(string), allowExternalEntrypoint)
+	callingFile := thread.Local(callingFileKey).(string)
+	modulePath, err := cleanModuleName(module, filepath.Dir(callingFile), allowExternalEntrypoint)
 	if err != nil {
 		return nil, err
 	}
@@ -150,6 +151,13 @@
 
 		// Load or return default
 		if mustLoad {
+			if strings.HasSuffix(callingFile, ".scl") && !strings.HasSuffix(modulePath, ".scl") {
+				return nil, fmt.Errorf(".scl files can only load other .scl files: %q loads %q", callingFile, modulePath)
+			}
+			// Switch into scl mode from here on
+			if strings.HasSuffix(modulePath, ".scl") {
+				mode = ExecutionModeScl
+			}
 			childThread := &starlark.Thread{Name: "exec " + module, Load: thread.Load}
 			// Cheating for the sake of testing:
 			// propagate starlarktest's Reporter key, otherwise testing
@@ -161,14 +169,14 @@
 
 			// Only the entrypoint starlark file allows external loads.
 			childThread.SetLocal(allowExternalEntrypointKey, false)
-			childThread.SetLocal(callerDirKey, filepath.Dir(modulePath))
+			childThread.SetLocal(callingFileKey, modulePath)
 			childThread.SetLocal(executionModeKey, mode)
 			childThread.SetLocal(shellKey, thread.Local(shellKey))
 			if mode == ExecutionModeRbc {
 				globals, err := starlark.ExecFile(childThread, modulePath, nil, rbcBuiltins)
 				e = &modentry{globals, err}
-			} else if mode == ExecutionModeMake {
-				globals, err := starlark.ExecFile(childThread, modulePath, nil, makeBuiltins)
+			} else if mode == ExecutionModeScl {
+				globals, err := starlark.ExecFile(childThread, modulePath, nil, sclBuiltins)
 				e = &modentry{globals, err}
 			} else {
 				return nil, fmt.Errorf("unknown executionMode %d", mode)
@@ -338,7 +346,7 @@
 			if mode == ExecutionModeRbc {
 				// In rbc mode, rblf_log is used to print to stderr
 				fmt.Println(msg)
-			} else if mode == ExecutionModeMake {
+			} else if mode == ExecutionModeScl {
 				fmt.Fprintln(os.Stderr, msg)
 			}
 		},
@@ -365,13 +373,13 @@
 
 	var results starlark.StringDict
 	mainThread.SetLocal(allowExternalEntrypointKey, allowExternalEntrypoint)
-	mainThread.SetLocal(callerDirKey, filepath.Dir(filename))
+	mainThread.SetLocal(callingFileKey, filename)
 	mainThread.SetLocal(executionModeKey, mode)
 	mainThread.SetLocal(shellKey, shellPath)
 	if mode == ExecutionModeRbc {
 		results, err = starlark.ExecFile(mainThread, filename, src, rbcBuiltins)
-	} else if mode == ExecutionModeMake {
-		results, err = starlark.ExecFile(mainThread, filename, src, makeBuiltins)
+	} else if mode == ExecutionModeScl {
+		results, err = starlark.ExecFile(mainThread, filename, src, sclBuiltins)
 	} else {
 		return results, nil, fmt.Errorf("unknown executionMode %d", mode)
 	}
diff --git a/tools/rbcrun/host_test.go b/tools/rbcrun/host_test.go
index 10ce55e..468a620 100644
--- a/tools/rbcrun/host_test.go
+++ b/tools/rbcrun/host_test.go
@@ -19,6 +19,7 @@
 	"os"
 	"path/filepath"
 	"runtime"
+	"strings"
 	"testing"
 
 	"go.starlark.net/resolve"
@@ -126,7 +127,7 @@
 		t.Fatal(err)
 	}
 	thread.SetLocal(allowExternalEntrypointKey, false)
-	thread.SetLocal(callerDirKey, dir)
+	thread.SetLocal(callingFileKey, "testdata/load.star")
 	thread.SetLocal(executionModeKey, ExecutionModeRbc)
 	if _, err := starlark.ExecFile(thread, "testdata/load.star", nil, rbcBuiltins); err != nil {
 		if err, ok := err.(*starlark.EvalError); ok {
@@ -136,6 +137,55 @@
 	}
 }
 
+func TestBzlLoadsScl(t *testing.T) {
+	moduleCache = make(map[string]*modentry)
+	dir := dataDir()
+	if err := os.Chdir(filepath.Dir(dir)); err != nil {
+		t.Fatal(err)
+	}
+	vars, _, err := Run("testdata/bzl_loads_scl.bzl", nil, ExecutionModeScl, false)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if val, ok := vars["foo"]; !ok {
+		t.Fatalf("Failed to load foo variable")
+	} else if val.(starlark.String) != "bar" {
+		t.Fatalf("Expected \"bar\", got %q", val)
+	}
+}
+
+func TestNonEntrypointBzlLoadsScl(t *testing.T) {
+	moduleCache = make(map[string]*modentry)
+	dir := dataDir()
+	if err := os.Chdir(filepath.Dir(dir)); err != nil {
+		t.Fatal(err)
+	}
+	vars, _, err := Run("testdata/bzl_loads_scl_2.bzl", nil, ExecutionModeScl, false)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if val, ok := vars["foo"]; !ok {
+		t.Fatalf("Failed to load foo variable")
+	} else if val.(starlark.String) != "bar" {
+		t.Fatalf("Expected \"bar\", got %q", val)
+	}
+}
+
+func TestSclLoadsBzl(t *testing.T) {
+	moduleCache = make(map[string]*modentry)
+	dir := dataDir()
+	if err := os.Chdir(filepath.Dir(dir)); err != nil {
+		t.Fatal(err)
+	}
+	_, _, err := Run("testdata/scl_incorrectly_loads_bzl.scl", nil, ExecutionModeScl, false)
+	if err == nil {
+		t.Fatal("Expected failure")
+	}
+	if !strings.Contains(err.Error(), ".scl files can only load other .scl files") {
+		t.Fatalf("Expected error to contain \".scl files can only load other .scl files\": %q", err.Error())
+	}
+}
+
 func TestShell(t *testing.T) {
 	exerciseStarlarkTestFile(t, "testdata/shell.star")
 }
diff --git a/tools/rbcrun/rbcrun/rbcrun.go b/tools/rbcrun/rbcrun/rbcrun.go
index a15b867..8c372c7 100644
--- a/tools/rbcrun/rbcrun/rbcrun.go
+++ b/tools/rbcrun/rbcrun/rbcrun.go
@@ -55,13 +55,13 @@
 	case "rbc":
 		return rbcrun.ExecutionModeRbc
 	case "make":
-		return rbcrun.ExecutionModeMake
+		return rbcrun.ExecutionModeScl
 	case "":
 		quit("-mode flag is required.")
 	default:
 		quit("Unknown -mode value %q, expected 1 of \"rbc\", \"make\"", *modeFlag)
 	}
-	return rbcrun.ExecutionModeMake
+	return rbcrun.ExecutionModeScl
 }
 
 var makeStringReplacer = strings.NewReplacer("#", "\\#", "$", "$$")
@@ -175,7 +175,7 @@
 			quit("%s\n", err)
 		}
 	}
-	if mode == rbcrun.ExecutionModeMake {
+	if mode == rbcrun.ExecutionModeScl {
 		if err := printVarsInMakeFormat(variables); err != nil {
 			quit("%s\n", err)
 		}
diff --git a/tools/rbcrun/testdata/bzl_loads_scl.bzl b/tools/rbcrun/testdata/bzl_loads_scl.bzl
new file mode 100644
index 0000000..e8deca3
--- /dev/null
+++ b/tools/rbcrun/testdata/bzl_loads_scl.bzl
@@ -0,0 +1,3 @@
+load(":test_scl.scl", _foo = "foo")
+
+foo = _foo
diff --git a/tools/rbcrun/testdata/bzl_loads_scl_2.bzl b/tools/rbcrun/testdata/bzl_loads_scl_2.bzl
new file mode 100644
index 0000000..9a680ed
--- /dev/null
+++ b/tools/rbcrun/testdata/bzl_loads_scl_2.bzl
@@ -0,0 +1,3 @@
+load(":bzl_loads_scl.bzl", _foo = "foo")
+
+foo = _foo
diff --git a/tools/rbcrun/testdata/scl_incorrectly_loads_bzl.scl b/tools/rbcrun/testdata/scl_incorrectly_loads_bzl.scl
new file mode 100644
index 0000000..9a680ed
--- /dev/null
+++ b/tools/rbcrun/testdata/scl_incorrectly_loads_bzl.scl
@@ -0,0 +1,3 @@
+load(":bzl_loads_scl.bzl", _foo = "foo")
+
+foo = _foo
diff --git a/tools/rbcrun/testdata/test_scl.scl b/tools/rbcrun/testdata/test_scl.scl
new file mode 100644
index 0000000..6360ccb
--- /dev/null
+++ b/tools/rbcrun/testdata/test_scl.scl
@@ -0,0 +1,2 @@
+
+foo = "bar"
diff --git a/tools/releasetools/ota_from_raw_img.py b/tools/releasetools/ota_from_raw_img.py
index 0c1c05a..c186940 100644
--- a/tools/releasetools/ota_from_raw_img.py
+++ b/tools/releasetools/ota_from_raw_img.py
@@ -68,6 +68,11 @@
   if args.verbose:
     logger.setLevel(logging.INFO)
   logger.info(args)
+  old_imgs = [""] * len(args.images)
+  for (i, img) in enumerate(args.images):
+    if ":" in img:
+      old_imgs[i], args.images[i] = img.split(":", maxsplit=1)
+
   if not args.partition_names:
     args.partition_names = [os.path.os.path.splitext(os.path.basename(path))[
         0] for path in args.images]
@@ -79,6 +84,7 @@
     cmd.append("--partition_names=" + ",".join(args.partition_names))
     cmd.append("--dynamic_partition_info_file=" +
                dynamic_partition_info_file.name)
+    cmd.append("--old_partitions=" + ",".join(old_imgs))
     cmd.append("--new_partitions=" + ",".join(args.images))
     cmd.append("--out_file=" + unsigned_payload.name)
     cmd.append("--is_partial_update")