diff --git a/android/androidmk.go b/android/androidmk.go
index a670656..42c5d00 100644
--- a/android/androidmk.go
+++ b/android/androidmk.go
@@ -12,6 +12,13 @@
 // See the License for the specific language governing permissions and
 // limitations under the License.
 
+// This file offers AndroidMkEntriesProvider, which individual modules implement to output
+// Android.mk entries that contain information about the modules built through Soong. Kati reads
+// and combines them with the legacy Make-based module definitions to produce the complete view of
+// the source tree, which makes this a critical point of Make-Soong interoperability.
+//
+// Naturally, Soong-only builds do not rely on this mechanism.
+
 package android
 
 import (
@@ -36,8 +43,8 @@
 	ctx.RegisterSingletonType("androidmk", AndroidMkSingleton)
 }
 
-// Deprecated: consider using AndroidMkEntriesProvider instead, especially if you're not going to
-// use the Custom function.
+// Deprecated: Use AndroidMkEntriesProvider instead, especially if you're not going to use the
+// Custom function. It's easier to use and test.
 type AndroidMkDataProvider interface {
 	AndroidMk() AndroidMkData
 	BaseModuleName() string
@@ -63,37 +70,82 @@
 
 type AndroidMkExtraFunc func(w io.Writer, outputFile Path)
 
-// Allows modules to customize their Android*.mk output.
+// Interface for modules to declare their Android.mk outputs. Note that every module needs to
+// implement this in order to be included in the final Android-<product_name>.mk output, even if
+// they only need to output the common set of entries without any customizations.
 type AndroidMkEntriesProvider interface {
+	// Returns AndroidMkEntries objects that contain all basic info plus extra customization data
+	// if needed. This is the core func to implement.
+	// Note that one can return multiple objects. For example, java_library may return an additional
+	// AndroidMkEntries object for its hostdex sub-module.
 	AndroidMkEntries() []AndroidMkEntries
+	// Modules don't need to implement this as it's already implemented by ModuleBase.
+	// AndroidMkEntries uses BaseModuleName() instead of ModuleName() because certain modules
+	// e.g. Prebuilts, override the Name() func and return modified names.
+	// If a different name is preferred, use SubName or OverrideName in AndroidMkEntries.
 	BaseModuleName() string
 }
 
+// The core data struct that modules use to provide their Android.mk data.
 type AndroidMkEntries struct {
-	Class           string
-	SubName         string
-	OverrideName    string
-	DistFiles       TaggedDistFiles
-	OutputFile      OptionalPath
-	Disabled        bool
-	Include         string
-	Required        []string
-	Host_required   []string
+	// Android.mk class string, e.g EXECUTABLES, JAVA_LIBRARIES, ETC
+	Class string
+	// Optional suffix to append to the module name. Useful when a module wants to return multiple
+	// AndroidMkEntries objects. For example, when a java_library returns an additional entry for
+	// its hostdex sub-module, this SubName field is set to "-hostdex" so that it can have a
+	// different name than the parent's.
+	SubName string
+	// If set, this value overrides the base module name. SubName is still appended.
+	OverrideName string
+	// Dist files to output
+	DistFiles TaggedDistFiles
+	// The output file for Kati to process and/or install. If absent, the module is skipped.
+	OutputFile OptionalPath
+	// If true, the module is skipped and does not appear on the final Android-<product name>.mk
+	// file. Useful when a module needs to be skipped conditionally.
+	Disabled bool
+	// The postprocessing mk file to include, e.g. $(BUILD_SYSTEM)/soong_cc_prebuilt.mk
+	// If not set, $(BUILD_SYSTEM)/prebuilt.mk is used.
+	Include string
+	// Required modules that need to be built and included in the final build output when building
+	// this module.
+	Required []string
+	// Required host modules that need to be built and included in the final build output when
+	// building this module.
+	Host_required []string
+	// Required device modules that need to be built and included in the final build output when
+	// building this module.
 	Target_required []string
 
 	header bytes.Buffer
 	footer bytes.Buffer
 
+	// Funcs to append additional Android.mk entries or modify the common ones. Multiple funcs are
+	// accepted so that common logic can be factored out as a shared func.
 	ExtraEntries []AndroidMkExtraEntriesFunc
+	// Funcs to add extra lines to the module's Android.mk output. Unlike AndroidMkExtraEntriesFunc,
+	// which simply sets Make variable values, this can be used for anything since it can write any
+	// Make statements directly to the final Android-*.mk file.
+	// Primarily used to call macros or declare/update Make targets.
 	ExtraFooters []AndroidMkExtraFootersFunc
 
-	EntryMap   map[string][]string
+	// A map that holds the up-to-date Make variable values. Can be accessed from tests.
+	EntryMap map[string][]string
+	// A list of EntryMap keys in insertion order. This serves a few purposes:
+	// 1. Prevents churns. Golang map doesn't provide consistent iteration order, so without this,
+	// the outputted Android-*.mk file may change even though there have been no content changes.
+	// 2. Allows modules to refer to other variables, like LOCAL_BAR_VAR := $(LOCAL_FOO_VAR),
+	// without worrying about the variables being mixed up in the actual mk file.
+	// 3. Makes troubleshooting and spotting errors easier.
 	entryOrder []string
 }
 
 type AndroidMkExtraEntriesFunc func(entries *AndroidMkEntries)
 type AndroidMkExtraFootersFunc func(w io.Writer, name, prefix, moduleDir string, entries *AndroidMkEntries)
 
+// Utility funcs to manipulate Android.mk variable entries.
+
+// SetString sets a Make variable with the given name to the given value.
 func (a *AndroidMkEntries) SetString(name, value string) {
 	if _, ok := a.EntryMap[name]; !ok {
 		a.entryOrder = append(a.entryOrder, name)
@@ -101,6 +153,7 @@
 	a.EntryMap[name] = []string{value}
 }
 
+// SetPath sets a Make variable with the given name to the given path string.
 func (a *AndroidMkEntries) SetPath(name string, path Path) {
 	if _, ok := a.EntryMap[name]; !ok {
 		a.entryOrder = append(a.entryOrder, name)
@@ -108,12 +161,15 @@
 	a.EntryMap[name] = []string{path.String()}
 }
 
+// SetOptionalPath sets a Make variable with the given name to the given path string if it is valid.
+// It is a no-op if the given path is invalid.
 func (a *AndroidMkEntries) SetOptionalPath(name string, path OptionalPath) {
 	if path.Valid() {
 		a.SetPath(name, path.Path())
 	}
 }
 
+// AddPath appends the given path string to a Make variable with the given name.
 func (a *AndroidMkEntries) AddPath(name string, path Path) {
 	if _, ok := a.EntryMap[name]; !ok {
 		a.entryOrder = append(a.entryOrder, name)
@@ -121,12 +177,15 @@
 	a.EntryMap[name] = append(a.EntryMap[name], path.String())
 }
 
+// AddOptionalPath appends the given path string to a Make variable with the given name if it is
+// valid. It is a no-op if the given path is invalid.
 func (a *AndroidMkEntries) AddOptionalPath(name string, path OptionalPath) {
 	if path.Valid() {
 		a.AddPath(name, path.Path())
 	}
 }
 
+// SetPaths sets a Make variable with the given name to a slice of the given path strings.
 func (a *AndroidMkEntries) SetPaths(name string, paths Paths) {
 	if _, ok := a.EntryMap[name]; !ok {
 		a.entryOrder = append(a.entryOrder, name)
@@ -134,12 +193,15 @@
 	a.EntryMap[name] = paths.Strings()
 }
 
+// SetOptionalPaths sets a Make variable with the given name to a slice of the given path strings
+// only if there are a non-zero amount of paths.
 func (a *AndroidMkEntries) SetOptionalPaths(name string, paths Paths) {
 	if len(paths) > 0 {
 		a.SetPaths(name, paths)
 	}
 }
 
+// AddPaths appends the given path strings to a Make variable with the given name.
 func (a *AndroidMkEntries) AddPaths(name string, paths Paths) {
 	if _, ok := a.EntryMap[name]; !ok {
 		a.entryOrder = append(a.entryOrder, name)
@@ -147,6 +209,8 @@
 	a.EntryMap[name] = append(a.EntryMap[name], paths.Strings()...)
 }
 
+// SetBoolIfTrue sets a Make variable with the given name to true if the given flag is true.
+// It is a no-op if the given flag is false.
 func (a *AndroidMkEntries) SetBoolIfTrue(name string, flag bool) {
 	if flag {
 		if _, ok := a.EntryMap[name]; !ok {
@@ -156,6 +220,7 @@
 	}
 }
 
+// SetBool sets a Make variable with the given name to if the given bool flag value.
 func (a *AndroidMkEntries) SetBool(name string, flag bool) {
 	if _, ok := a.EntryMap[name]; !ok {
 		a.entryOrder = append(a.entryOrder, name)
@@ -167,6 +232,7 @@
 	}
 }
 
+// AddStrings appends the given strings to a Make variable with the given name.
 func (a *AndroidMkEntries) AddStrings(name string, value ...string) {
 	if len(value) == 0 {
 		return
@@ -368,6 +434,8 @@
 	return generateDistContributionsForMake(distContributions)
 }
 
+// fillInEntries goes through the common variable processing and calls the extra data funcs to
+// generate and fill in AndroidMkEntries's in-struct data, ready to be flushed to a file.
 func (a *AndroidMkEntries) fillInEntries(config Config, bpPath string, mod blueprint.Module) {
 	a.EntryMap = make(map[string][]string)
 	amod := mod.(Module).base()
@@ -431,7 +499,9 @@
 			}
 		}
 
-		a.AddStrings("LOCAL_INIT_RC", amod.commonProperties.Init_rc...)
+		if !amod.InRamdisk() && !amod.InVendorRamdisk() {
+			a.AddStrings("LOCAL_INIT_RC", amod.commonProperties.Init_rc...)
+		}
 		a.AddStrings("LOCAL_VINTF_FRAGMENTS", amod.commonProperties.Vintf_fragments...)
 		a.SetBoolIfTrue("LOCAL_PROPRIETARY_MODULE", Bool(amod.commonProperties.Proprietary))
 		if Bool(amod.commonProperties.Vendor) || Bool(amod.commonProperties.Soc_specific) {
@@ -488,6 +558,8 @@
 	}
 }
 
+// write  flushes the AndroidMkEntries's in-struct data populated by AndroidMkEntries into the
+// given Writer object.
 func (a *AndroidMkEntries) write(w io.Writer) {
 	if a.Disabled {
 		return
@@ -508,6 +580,8 @@
 	return strings.Split(string(a.footer.Bytes()), "\n")
 }
 
+// AndroidMkSingleton is a singleton to collect Android.mk data from all modules and dump them into
+// the final Android-<product_name>.mk file output.
 func AndroidMkSingleton() Singleton {
 	return &androidMkSingleton{}
 }
@@ -515,6 +589,7 @@
 type androidMkSingleton struct{}
 
 func (c *androidMkSingleton) GenerateBuildActions(ctx SingletonContext) {
+	// Skip if Soong wasn't invoked from Make.
 	if !ctx.Config().KatiEnabled() {
 		return
 	}
@@ -525,6 +600,8 @@
 		androidMkModulesList = append(androidMkModulesList, module)
 	})
 
+	// Sort the module list by the module names to eliminate random churns, which may erroneously
+	// invoke additional build processes.
 	sort.SliceStable(androidMkModulesList, func(i, j int) bool {
 		return ctx.ModuleName(androidMkModulesList[i]) < ctx.ModuleName(androidMkModulesList[j])
 	})
@@ -617,6 +694,8 @@
 	}
 }
 
+// A simple, special Android.mk entry output func to make it possible to build blueprint tools using
+// m by making them phony targets.
 func translateGoBinaryModule(ctx SingletonContext, w io.Writer, mod blueprint.Module,
 	goBinary bootstrap.GoBinaryTool) error {
 
@@ -649,6 +728,8 @@
 	data.Target_required = data.Entries.Target_required
 }
 
+// A support func for the deprecated AndroidMkDataProvider interface. Use AndroidMkEntryProvider
+// instead.
 func translateAndroidModule(ctx SingletonContext, w io.Writer, mod blueprint.Module,
 	provider AndroidMkDataProvider) error {
 
@@ -695,6 +776,8 @@
 	return nil
 }
 
+// A support func for the deprecated AndroidMkDataProvider interface. Use AndroidMkEntryProvider
+// instead.
 func WriteAndroidMkData(w io.Writer, data AndroidMkData) {
 	if data.Disabled {
 		return
@@ -742,11 +825,14 @@
 		module.Os() == LinuxBionic
 }
 
+// A utility func to format LOCAL_TEST_DATA outputs. See the comments on DataPath to understand how
+// to use this func.
 func AndroidMkDataPaths(data []DataPath) []string {
 	var testFiles []string
 	for _, d := range data {
 		rel := d.SrcPath.Rel()
 		path := d.SrcPath.String()
+		// LOCAL_TEST_DATA requires the rel portion of the path to be removed from the path.
 		if !strings.HasSuffix(path, rel) {
 			panic(fmt.Errorf("path %q does not end with %q", path, rel))
 		}
diff --git a/android/arch.go b/android/arch.go
index df407d4..34f9b29 100644
--- a/android/arch.go
+++ b/android/arch.go
@@ -1337,17 +1337,6 @@
 		addTarget(BuildOs, *variables.HostSecondaryArch, nil, nil, nil, NativeBridgeDisabled, nil, nil)
 	}
 
-	// An optional host target that uses the Bionic glibc runtime.
-	if Bool(config.Host_bionic) {
-		addTarget(LinuxBionic, "x86_64", nil, nil, nil, NativeBridgeDisabled, nil, nil)
-	}
-
-	// An optional cross-compiled host target that uses the Bionic glibc runtime on an arm64
-	// architecture.
-	if Bool(config.Host_bionic_arm64) {
-		addTarget(LinuxBionic, "arm64", nil, nil, nil, NativeBridgeDisabled, nil, nil)
-	}
-
 	// Optional cross-compiled host targets, generally Windows.
 	if String(variables.CrossHost) != "" {
 		crossHostOs := osByName(*variables.CrossHost)
@@ -1437,53 +1426,6 @@
 	abi         []string
 }
 
-// getMegaDeviceConfig returns a list of archConfigs for every architecture simultaneously.
-func getMegaDeviceConfig() []archConfig {
-	return []archConfig{
-		{"arm", "armv7-a", "generic", []string{"armeabi-v7a"}},
-		{"arm", "armv7-a-neon", "generic", []string{"armeabi-v7a"}},
-		{"arm", "armv7-a-neon", "cortex-a7", []string{"armeabi-v7a"}},
-		{"arm", "armv7-a-neon", "cortex-a8", []string{"armeabi-v7a"}},
-		{"arm", "armv7-a-neon", "cortex-a9", []string{"armeabi-v7a"}},
-		{"arm", "armv7-a-neon", "cortex-a15", []string{"armeabi-v7a"}},
-		{"arm", "armv7-a-neon", "cortex-a53", []string{"armeabi-v7a"}},
-		{"arm", "armv7-a-neon", "cortex-a53.a57", []string{"armeabi-v7a"}},
-		{"arm", "armv7-a-neon", "cortex-a72", []string{"armeabi-v7a"}},
-		{"arm", "armv7-a-neon", "cortex-a73", []string{"armeabi-v7a"}},
-		{"arm", "armv7-a-neon", "cortex-a75", []string{"armeabi-v7a"}},
-		{"arm", "armv7-a-neon", "cortex-a76", []string{"armeabi-v7a"}},
-		{"arm", "armv7-a-neon", "krait", []string{"armeabi-v7a"}},
-		{"arm", "armv7-a-neon", "kryo", []string{"armeabi-v7a"}},
-		{"arm", "armv7-a-neon", "kryo385", []string{"armeabi-v7a"}},
-		{"arm", "armv7-a-neon", "exynos-m1", []string{"armeabi-v7a"}},
-		{"arm", "armv7-a-neon", "exynos-m2", []string{"armeabi-v7a"}},
-		{"arm64", "armv8-a", "cortex-a53", []string{"arm64-v8a"}},
-		{"arm64", "armv8-a", "cortex-a72", []string{"arm64-v8a"}},
-		{"arm64", "armv8-a", "cortex-a73", []string{"arm64-v8a"}},
-		{"arm64", "armv8-a", "kryo", []string{"arm64-v8a"}},
-		{"arm64", "armv8-a", "exynos-m1", []string{"arm64-v8a"}},
-		{"arm64", "armv8-a", "exynos-m2", []string{"arm64-v8a"}},
-		{"arm64", "armv8-2a", "kryo385", []string{"arm64-v8a"}},
-		{"arm64", "armv8-2a-dotprod", "cortex-a55", []string{"arm64-v8a"}},
-		{"arm64", "armv8-2a-dotprod", "cortex-a75", []string{"arm64-v8a"}},
-		{"arm64", "armv8-2a-dotprod", "cortex-a76", []string{"arm64-v8a"}},
-		{"x86", "", "", []string{"x86"}},
-		{"x86", "atom", "", []string{"x86"}},
-		{"x86", "haswell", "", []string{"x86"}},
-		{"x86", "ivybridge", "", []string{"x86"}},
-		{"x86", "sandybridge", "", []string{"x86"}},
-		{"x86", "silvermont", "", []string{"x86"}},
-		{"x86", "stoneyridge", "", []string{"x86"}},
-		{"x86", "x86_64", "", []string{"x86"}},
-		{"x86_64", "", "", []string{"x86_64"}},
-		{"x86_64", "haswell", "", []string{"x86_64"}},
-		{"x86_64", "ivybridge", "", []string{"x86_64"}},
-		{"x86_64", "sandybridge", "", []string{"x86_64"}},
-		{"x86_64", "silvermont", "", []string{"x86_64"}},
-		{"x86_64", "stoneyridge", "", []string{"x86_64"}},
-	}
-}
-
 // getNdkAbisConfig returns a list of archConfigs for the ABIs supported by the NDK.
 func getNdkAbisConfig() []archConfig {
 	return []archConfig{
diff --git a/android/config.go b/android/config.go
index 04c9129..9882d55 100644
--- a/android/config.go
+++ b/android/config.go
@@ -54,28 +54,9 @@
 	isPreview: true,
 }
 
-// configFileName is the name the file containing FileConfigurableOptions from
-// soong_ui for the soong_build primary builder.
-const configFileName = "soong.config"
-
-// productVariablesFileName contain the product configuration variables from soong_ui for the
-// soong_build primary builder and Kati.
+// The product variables file name, containing product config from Kati.
 const productVariablesFileName = "soong.variables"
 
-// A FileConfigurableOptions contains options which can be configured by the
-// config file. These will be included in the config struct.
-type FileConfigurableOptions struct {
-	Mega_device       *bool `json:",omitempty"`
-	Host_bionic       *bool `json:",omitempty"`
-	Host_bionic_arm64 *bool `json:",omitempty"`
-}
-
-// SetDefaultConfig resets the receiving FileConfigurableOptions to default
-// values.
-func (f *FileConfigurableOptions) SetDefaultConfig() {
-	*f = FileConfigurableOptions{}
-}
-
 // A Config object represents the entire build configuration for Android.
 type Config struct {
 	*config
@@ -97,12 +78,8 @@
 type VendorConfig soongconfig.SoongConfig
 
 // Definition of general build configuration for soong_build. Some of these
-// configuration values are generated from soong_ui for soong_build,
-// communicated over JSON files like soong.config or soong.variables.
+// product configuration values are read from Kati-generated soong.variables.
 type config struct {
-	// Options configurable with soong.confg
-	FileConfigurableOptions
-
 	// Options configurable with soong.variables
 	productVariables productVariables
 
@@ -113,7 +90,6 @@
 	// purposes.
 	BazelContext BazelContext
 
-	ConfigFileName           string
 	ProductVariablesFileName string
 
 	Targets                  map[OsType][]Target
@@ -170,11 +146,6 @@
 }
 
 func loadConfig(config *config) error {
-	err := loadFromConfigFile(&config.FileConfigurableOptions, absolutePath(config.ConfigFileName))
-	if err != nil {
-		return err
-	}
-
 	return loadFromConfigFile(&config.productVariables, absolutePath(config.ProductVariablesFileName))
 }
 
@@ -384,7 +355,6 @@
 func NewConfig(srcDir, buildDir string, moduleListFile string) (Config, error) {
 	// Make a config with default options.
 	config := &config{
-		ConfigFileName:           filepath.Join(buildDir, configFileName),
 		ProductVariablesFileName: filepath.Join(buildDir, productVariablesFileName),
 
 		env: originalEnv,
@@ -439,9 +409,7 @@
 	targets[CommonOS] = []Target{commonTargetMap[CommonOS.Name]}
 
 	var archConfig []archConfig
-	if Bool(config.Mega_device) {
-		archConfig = getMegaDeviceConfig()
-	} else if config.NdkAbis() {
+	if config.NdkAbis() {
 		archConfig = getNdkAbisConfig()
 	} else if config.AmlAbis() {
 		archConfig = getAmlAbisConfig()
@@ -864,11 +832,6 @@
 	return c.Targets[Android][0].Arch.ArchType
 }
 
-func (c *config) SkipMegaDeviceInstall(path string) bool {
-	return Bool(c.Mega_device) &&
-		strings.HasPrefix(path, filepath.Join(c.buildDir, "target", "product"))
-}
-
 func (c *config) SanitizeHost() []string {
 	return append([]string(nil), c.productVariables.SanitizeHost...)
 }
@@ -1321,6 +1284,14 @@
 	return Bool(c.productVariables.EnforceProductPartitionInterface)
 }
 
+func (c *config) EnforceInterPartitionJavaSdkLibrary() bool {
+	return Bool(c.productVariables.EnforceInterPartitionJavaSdkLibrary)
+}
+
+func (c *config) InterPartitionJavaLibraryAllowList() []string {
+	return c.productVariables.InterPartitionJavaLibraryAllowList
+}
+
 func (c *config) InstallExtraFlattenedApexes() bool {
 	return Bool(c.productVariables.InstallExtraFlattenedApexes)
 }
diff --git a/android/config_test.go b/android/config_test.go
index 68f68a0..7bfc800 100644
--- a/android/config_test.go
+++ b/android/config_test.go
@@ -78,11 +78,6 @@
 	if err != nil {
 		t.Errorf(err.Error())
 	}
-
-	validateConfigAnnotations(&FileConfigurableOptions{})
-	if err != nil {
-		t.Errorf(err.Error())
-	}
 }
 
 func TestMissingVendorConfig(t *testing.T) {
diff --git a/android/defs.go b/android/defs.go
index 631dfe8..f5bd362 100644
--- a/android/defs.go
+++ b/android/defs.go
@@ -15,6 +15,7 @@
 package android
 
 import (
+	"fmt"
 	"strings"
 	"testing"
 
@@ -97,7 +98,7 @@
 	// content to file.
 	writeFile = pctx.AndroidStaticRule("writeFile",
 		blueprint.RuleParams{
-			Command:     `/bin/bash -c 'echo -e "$$0" > $out' $content`,
+			Command:     `/bin/bash -c 'echo -e -n "$$0" > $out' $content`,
 			Description: "writing file $out",
 		},
 		"content")
@@ -133,9 +134,7 @@
 	shellUnescaper = strings.NewReplacer(`'\''`, `'`)
 )
 
-// WriteFileRule creates a ninja rule to write contents to a file.  The contents will be escaped
-// so that the file contains exactly the contents passed to the function, plus a trailing newline.
-func WriteFileRule(ctx BuilderContext, outputFile WritablePath, content string) {
+func buildWriteFileRule(ctx BuilderContext, outputFile WritablePath, content string) {
 	content = echoEscaper.Replace(content)
 	content = proptools.ShellEscape(content)
 	if content == "" {
@@ -151,6 +150,31 @@
 	})
 }
 
+// WriteFileRule creates a ninja rule to write contents to a file.  The contents will be escaped
+// so that the file contains exactly the contents passed to the function, plus a trailing newline.
+func WriteFileRule(ctx BuilderContext, outputFile WritablePath, content string) {
+	// This is MAX_ARG_STRLEN subtracted with some safety to account for shell escapes
+	const SHARD_SIZE = 131072 - 10000
+
+	content += "\n"
+	if len(content) > SHARD_SIZE {
+		var chunks WritablePaths
+		for i, c := range ShardString(content, SHARD_SIZE) {
+			tempPath := outputFile.ReplaceExtension(ctx, fmt.Sprintf("%s.%d", outputFile.Ext(), i))
+			buildWriteFileRule(ctx, tempPath, c)
+			chunks = append(chunks, tempPath)
+		}
+		ctx.Build(pctx, BuildParams{
+			Rule:        Cat,
+			Inputs:      chunks.Paths(),
+			Output:      outputFile,
+			Description: "Merging to " + outputFile.Base(),
+		})
+		return
+	}
+	buildWriteFileRule(ctx, outputFile, content)
+}
+
 // shellUnescape reverses proptools.ShellEscape
 func shellUnescape(s string) string {
 	// Remove leading and trailing quotes if present
diff --git a/android/module.go b/android/module.go
index d680baa..b6729c0 100644
--- a/android/module.go
+++ b/android/module.go
@@ -2399,10 +2399,6 @@
 		if m.Config().KatiEnabled() && !m.InstallBypassMake() {
 			return true
 		}
-
-		if m.Config().SkipMegaDeviceInstall(fullInstallPath.String()) {
-			return true
-		}
 	}
 
 	return false
diff --git a/android/packaging.go b/android/packaging.go
index ea59888..09432e6 100644
--- a/android/packaging.go
+++ b/android/packaging.go
@@ -153,15 +153,9 @@
 
 // See PackageModule.CopyDepsToZip
 func (p *PackagingBase) CopyDepsToZip(ctx ModuleContext, zipOut OutputPath) (entries []string) {
-	var supportedArches []string
-	for _, t := range p.getSupportedTargets(ctx) {
-		supportedArches = append(supportedArches, t.Arch.ArchType.String())
-	}
 	m := make(map[string]PackagingSpec)
 	ctx.WalkDeps(func(child Module, parent Module) bool {
-		// Don't track modules with unsupported arch
-		// TODO(jiyong): remove this when aosp/1501613 lands.
-		if !InList(child.Target().Arch.ArchType.String(), supportedArches) {
+		if !IsInstallDepNeeded(ctx.OtherModuleDependencyTag(child)) {
 			return false
 		}
 		for _, ps := range child.PackagingSpecs() {
@@ -172,7 +166,7 @@
 		return true
 	})
 
-	builder := NewRuleBuilder()
+	builder := NewRuleBuilder(pctx, ctx)
 
 	dir := PathForModuleOut(ctx, ".zip").OutputPath
 	builder.Command().Text("rm").Flag("-rf").Text(dir.String())
@@ -199,13 +193,13 @@
 	}
 
 	builder.Command().
-		BuiltTool(ctx, "soong_zip").
+		BuiltTool("soong_zip").
 		FlagWithOutput("-o ", zipOut).
 		FlagWithArg("-C ", dir.String()).
 		Flag("-L 0"). // no compression because this will be unzipped soon
 		FlagWithArg("-D ", dir.String())
 	builder.Command().Text("rm").Flag("-rf").Text(dir.String())
 
-	builder.Build(pctx, ctx, "zip_deps", fmt.Sprintf("Zipping deps for %s", ctx.ModuleName()))
+	builder.Build("zip_deps", fmt.Sprintf("Zipping deps for %s", ctx.ModuleName()))
 	return entries
 }
diff --git a/android/packaging_test.go b/android/packaging_test.go
index 2acd15c..7269bfb 100644
--- a/android/packaging_test.go
+++ b/android/packaging_test.go
@@ -29,6 +29,12 @@
 	}
 }
 
+// dep tag used in this test. All dependencies are considered as installable.
+type installDepTag struct {
+	blueprint.BaseDependencyTag
+	InstallAlwaysNeededDependencyTag
+}
+
 func componentTestModuleFactory() Module {
 	m := &componentTestModule{}
 	m.AddProperties(&m.props)
@@ -37,7 +43,7 @@
 }
 
 func (m *componentTestModule) DepsMutator(ctx BottomUpMutatorContext) {
-	ctx.AddDependency(ctx.Module(), nil, m.props.Deps...)
+	ctx.AddDependency(ctx.Module(), installDepTag{}, m.props.Deps...)
 }
 
 func (m *componentTestModule) GenerateAndroidBuildActions(ctx ModuleContext) {
@@ -63,7 +69,7 @@
 }
 
 func (m *packageTestModule) DepsMutator(ctx BottomUpMutatorContext) {
-	m.AddDeps(ctx, struct{ blueprint.BaseDependencyTag }{})
+	m.AddDeps(ctx, installDepTag{})
 }
 
 func (m *packageTestModule) GenerateAndroidBuildActions(ctx ModuleContext) {
diff --git a/android/paths.go b/android/paths.go
index b7117a3..5a41cf1 100644
--- a/android/paths.go
+++ b/android/paths.go
@@ -138,6 +138,8 @@
 	// the writablePath method doesn't directly do anything,
 	// but it allows a struct to distinguish between whether or not it implements the WritablePath interface
 	writablePath()
+
+	ReplaceExtension(ctx PathContext, ext string) OutputPath
 }
 
 type genPathProvider interface {
@@ -1249,6 +1251,10 @@
 	return p.config.buildDir
 }
 
+func (p InstallPath) ReplaceExtension(ctx PathContext, ext string) OutputPath {
+	panic("Not implemented")
+}
+
 var _ Path = InstallPath{}
 var _ WritablePath = InstallPath{}
 
@@ -1511,6 +1517,10 @@
 	return p.config.buildDir
 }
 
+func (p PhonyPath) ReplaceExtension(ctx PathContext, ext string) OutputPath {
+	panic("Not implemented")
+}
+
 var _ Path = PhonyPath{}
 var _ WritablePath = PhonyPath{}
 
diff --git a/android/proto.go b/android/proto.go
index b712258..0be7893 100644
--- a/android/proto.go
+++ b/android/proto.go
@@ -122,7 +122,7 @@
 	} `android:"arch_variant"`
 }
 
-func ProtoRule(ctx ModuleContext, rule *RuleBuilder, protoFile Path, flags ProtoFlags, deps Paths,
+func ProtoRule(rule *RuleBuilder, protoFile Path, flags ProtoFlags, deps Paths,
 	outDir WritablePath, depFile WritablePath, outputs WritablePaths) {
 
 	var protoBase string
@@ -134,7 +134,7 @@
 	}
 
 	rule.Command().
-		BuiltTool(ctx, "aprotoc").
+		BuiltTool("aprotoc").
 		FlagWithArg(flags.OutTypeFlag+"=", strings.Join(flags.OutParams, ",")+":"+outDir.String()).
 		FlagWithDepFile("--dependency_out=", depFile).
 		FlagWithArg("-I ", protoBase).
@@ -144,5 +144,5 @@
 		ImplicitOutputs(outputs)
 
 	rule.Command().
-		BuiltTool(ctx, "dep_fixer").Flag(depFile.String())
+		BuiltTool("dep_fixer").Flag(depFile.String())
 }
diff --git a/android/rule_builder.go b/android/rule_builder.go
index 3efe9f8..e2d8187 100644
--- a/android/rule_builder.go
+++ b/android/rule_builder.go
@@ -37,6 +37,9 @@
 // RuleBuilder provides an alternative to ModuleContext.Rule and ModuleContext.Build to add a command line to the build
 // graph.
 type RuleBuilder struct {
+	pctx PackageContext
+	ctx  BuilderContext
+
 	commands         []*RuleBuilderCommand
 	installs         RuleBuilderInstalls
 	temporariesSet   map[WritablePath]bool
@@ -44,14 +47,16 @@
 	sbox             bool
 	highmem          bool
 	remoteable       RemoteRuleSupports
-	sboxOutDir       WritablePath
+	outDir           WritablePath
 	sboxManifestPath WritablePath
 	missingDeps      []string
 }
 
 // NewRuleBuilder returns a newly created RuleBuilder.
-func NewRuleBuilder() *RuleBuilder {
+func NewRuleBuilder(pctx PackageContext, ctx BuilderContext) *RuleBuilder {
 	return &RuleBuilder{
+		pctx:           pctx,
+		ctx:            ctx,
 		temporariesSet: make(map[WritablePath]bool),
 	}
 }
@@ -130,7 +135,7 @@
 		panic("Sbox() is not compatible with Restat()")
 	}
 	r.sbox = true
-	r.sboxOutDir = outputDir
+	r.outDir = outputDir
 	r.sboxManifestPath = manifestPath
 	return r
 }
@@ -146,8 +151,7 @@
 // race with any call to Build.
 func (r *RuleBuilder) Command() *RuleBuilderCommand {
 	command := &RuleBuilderCommand{
-		sbox:   r.sbox,
-		outDir: r.sboxOutDir,
+		rule: r,
 	}
 	r.commands = append(r.commands, command)
 	return command
@@ -395,19 +399,19 @@
 var _ BuilderContext = ModuleContext(nil)
 var _ BuilderContext = SingletonContext(nil)
 
-func (r *RuleBuilder) depFileMergerCmd(ctx PathContext, depFiles WritablePaths) *RuleBuilderCommand {
+func (r *RuleBuilder) depFileMergerCmd(depFiles WritablePaths) *RuleBuilderCommand {
 	return r.Command().
-		BuiltTool(ctx, "dep_fixer").
+		BuiltTool("dep_fixer").
 		Inputs(depFiles.Paths())
 }
 
 // Build adds the built command line to the build graph, with dependencies on Inputs and Tools, and output files for
 // Outputs.
-func (r *RuleBuilder) Build(pctx PackageContext, ctx BuilderContext, name string, desc string) {
+func (r *RuleBuilder) Build(name string, desc string) {
 	name = ninjaNameEscape(name)
 
 	if len(r.missingDeps) > 0 {
-		ctx.Build(pctx, BuildParams{
+		r.ctx.Build(pctx, BuildParams{
 			Rule:        ErrorRule,
 			Outputs:     r.Outputs(),
 			OrderOnly:   r.OrderOnlys(),
@@ -426,13 +430,13 @@
 		depFormat = blueprint.DepsGCC
 		if len(depFiles) > 1 {
 			// Add a command locally that merges all depfiles together into the first depfile.
-			r.depFileMergerCmd(ctx, depFiles)
+			r.depFileMergerCmd(depFiles)
 
 			if r.sbox {
 				// Check for Rel() errors, as all depfiles should be in the output dir.  Errors
 				// will be reported to the ctx.
 				for _, path := range depFiles[1:] {
-					Rel(ctx, r.sboxOutDir.String(), path.String())
+					Rel(r.ctx, r.outDir.String(), path.String())
 				}
 			}
 		}
@@ -468,7 +472,7 @@
 		// to the output directory.
 		sboxOutputs := make([]string, len(outputs))
 		for i, output := range outputs {
-			rel := Rel(ctx, r.sboxOutDir.String(), output.String())
+			rel := Rel(r.ctx, r.outDir.String(), output.String())
 			sboxOutputs[i] = filepath.Join(sboxOutDir, rel)
 			command.CopyAfter = append(command.CopyAfter, &sbox_proto.Copy{
 				From: proto.String(filepath.Join(sboxOutSubDir, rel)),
@@ -483,23 +487,27 @@
 
 		// Verify that the manifest textproto is not inside the sbox output directory, otherwise
 		// it will get deleted when the sbox rule clears its output directory.
-		_, manifestInOutDir := MaybeRel(ctx, r.sboxOutDir.String(), r.sboxManifestPath.String())
+		_, manifestInOutDir := MaybeRel(r.ctx, r.outDir.String(), r.sboxManifestPath.String())
 		if manifestInOutDir {
-			ReportPathErrorf(ctx, "sbox rule %q manifestPath %q must not be in outputDir %q",
-				name, r.sboxManifestPath.String(), r.sboxOutDir.String())
+			ReportPathErrorf(r.ctx, "sbox rule %q manifestPath %q must not be in outputDir %q",
+				name, r.sboxManifestPath.String(), r.outDir.String())
 		}
 
 		// Create a rule to write the manifest as a the textproto.
-		WriteFileRule(ctx, r.sboxManifestPath, proto.MarshalTextString(&manifest))
+		WriteFileRule(r.ctx, r.sboxManifestPath, proto.MarshalTextString(&manifest))
 
 		// Generate a new string to use as the command line of the sbox rule.  This uses
 		// a RuleBuilderCommand as a convenience method of building the command line, then
 		// converts it to a string to replace commandString.
-		sboxCmd := &RuleBuilderCommand{}
-		sboxCmd.Text("rm -rf").Output(r.sboxOutDir)
+		sboxCmd := &RuleBuilderCommand{
+			rule: &RuleBuilder{
+				ctx: r.ctx,
+			},
+		}
+		sboxCmd.Text("rm -rf").Output(r.outDir)
 		sboxCmd.Text("&&")
-		sboxCmd.BuiltTool(ctx, "sbox").
-			Flag("--sandbox-path").Text(shared.TempDirForOutDir(PathForOutput(ctx).String())).
+		sboxCmd.BuiltTool("sbox").
+			Flag("--sandbox-path").Text(shared.TempDirForOutDir(PathForOutput(r.ctx).String())).
 			Flag("--manifest").Input(r.sboxManifestPath)
 
 		// Replace the command string, and add the sbox tool and manifest textproto to the
@@ -528,19 +536,19 @@
 	}
 
 	var pool blueprint.Pool
-	if ctx.Config().UseGoma() && r.remoteable.Goma {
+	if r.ctx.Config().UseGoma() && r.remoteable.Goma {
 		// When USE_GOMA=true is set and the rule is supported by goma, allow jobs to run outside the local pool.
-	} else if ctx.Config().UseRBE() && r.remoteable.RBE {
+	} else if r.ctx.Config().UseRBE() && r.remoteable.RBE {
 		// When USE_RBE=true is set and the rule is supported by RBE, use the remotePool.
 		pool = remotePool
 	} else if r.highmem {
 		pool = highmemPool
-	} else if ctx.Config().UseRemoteBuild() {
+	} else if r.ctx.Config().UseRemoteBuild() {
 		pool = localPool
 	}
 
-	ctx.Build(pctx, BuildParams{
-		Rule: ctx.Rule(pctx, name, blueprint.RuleParams{
+	r.ctx.Build(r.pctx, BuildParams{
+		Rule: r.ctx.Rule(pctx, name, blueprint.RuleParams{
 			Command:        commandString,
 			CommandDeps:    tools.Strings(),
 			Restat:         r.restat,
@@ -564,6 +572,8 @@
 // RuleBuilderCommand, so they can be used chained or unchained.  All methods that add text implicitly add a single
 // space as a separator from the previous method.
 type RuleBuilderCommand struct {
+	rule *RuleBuilder
+
 	buf            strings.Builder
 	inputs         Paths
 	implicits      Paths
@@ -576,16 +586,11 @@
 
 	// spans [start,end) of the command that should not be ninja escaped
 	unescapedSpans [][2]int
-
-	sbox bool
-	// outDir is the directory that will contain the output files of the rules.  sbox will copy
-	// the output files from the sandbox directory to this directory when it finishes.
-	outDir WritablePath
 }
 
 func (c *RuleBuilderCommand) addInput(path Path) string {
-	if c.sbox {
-		if rel, isRel, _ := maybeRelErr(c.outDir.String(), path.String()); isRel {
+	if c.rule.sbox {
+		if rel, isRel, _ := maybeRelErr(c.rule.outDir.String(), path.String()); isRel {
 			return filepath.Join(sboxOutDir, rel)
 		}
 	}
@@ -594,8 +599,8 @@
 }
 
 func (c *RuleBuilderCommand) addImplicit(path Path) string {
-	if c.sbox {
-		if rel, isRel, _ := maybeRelErr(c.outDir.String(), path.String()); isRel {
+	if c.rule.sbox {
+		if rel, isRel, _ := maybeRelErr(c.rule.outDir.String(), path.String()); isRel {
 			return filepath.Join(sboxOutDir, rel)
 		}
 	}
@@ -607,22 +612,19 @@
 	c.orderOnlys = append(c.orderOnlys, path)
 }
 
-func (c *RuleBuilderCommand) outputStr(path WritablePath) string {
-	if c.sbox {
-		return SboxPathForOutput(path, c.outDir)
+// PathForOutput takes an output path and returns the appropriate path to use on the command
+// line.  If sbox was enabled via a call to RuleBuilder.Sbox(), it returns a path with the
+// placeholder prefix used for outputs in sbox.  If sbox is not enabled it returns the
+// original path.
+func (c *RuleBuilderCommand) PathForOutput(path WritablePath) string {
+	if c.rule.sbox {
+		// Errors will be handled in RuleBuilder.Build where we have a context to report them
+		rel, _, _ := maybeRelErr(c.rule.outDir.String(), path.String())
+		return filepath.Join(sboxOutDir, rel)
 	}
 	return path.String()
 }
 
-// SboxPathForOutput takes an output path and the out directory passed to RuleBuilder.Sbox(),
-// and returns the corresponding path for the output in the sbox sandbox.  This can be used
-// on the RuleBuilder command line to reference the output.
-func SboxPathForOutput(path WritablePath, outDir WritablePath) string {
-	// Errors will be handled in RuleBuilder.Build where we have a context to report them
-	rel, _, _ := maybeRelErr(outDir.String(), path.String())
-	return filepath.Join(sboxOutDir, rel)
-}
-
 // Text adds the specified raw text to the command line.  The text should not contain input or output paths or the
 // rule will not have them listed in its dependencies or outputs.
 func (c *RuleBuilderCommand) Text(text string) *RuleBuilderCommand {
@@ -699,8 +701,8 @@
 //
 // It is equivalent to:
 //  cmd.Tool(ctx.Config().HostToolPath(ctx, tool))
-func (c *RuleBuilderCommand) BuiltTool(ctx PathContext, tool string) *RuleBuilderCommand {
-	return c.Tool(ctx.Config().HostToolPath(ctx, tool))
+func (c *RuleBuilderCommand) BuiltTool(tool string) *RuleBuilderCommand {
+	return c.Tool(c.rule.ctx.Config().HostToolPath(c.rule.ctx, tool))
 }
 
 // PrebuiltBuildTool adds the specified tool path from prebuils/build-tools.  The path will be also added to the
@@ -768,7 +770,7 @@
 // RuleBuilder.Outputs.
 func (c *RuleBuilderCommand) Output(path WritablePath) *RuleBuilderCommand {
 	c.outputs = append(c.outputs, path)
-	return c.Text(c.outputStr(path))
+	return c.Text(c.PathForOutput(path))
 }
 
 // Outputs adds the specified output paths to the command line, separated by spaces.  The paths will also be added to
@@ -783,7 +785,7 @@
 // OutputDir adds the output directory to the command line. This is only available when used with RuleBuilder.Sbox,
 // and will be the temporary output directory managed by sbox, not the final one.
 func (c *RuleBuilderCommand) OutputDir() *RuleBuilderCommand {
-	if !c.sbox {
+	if !c.rule.sbox {
 		panic("OutputDir only valid with Sbox")
 	}
 	return c.Text(sboxOutDir)
@@ -794,7 +796,7 @@
 // commands in a single RuleBuilder then RuleBuilder.Build will add an extra command to merge the depfiles together.
 func (c *RuleBuilderCommand) DepFile(path WritablePath) *RuleBuilderCommand {
 	c.depFiles = append(c.depFiles, path)
-	return c.Text(c.outputStr(path))
+	return c.Text(c.PathForOutput(path))
 }
 
 // ImplicitOutput adds the specified output path to the dependencies returned by RuleBuilder.Outputs without modifying
@@ -885,14 +887,14 @@
 // will also be added to the outputs returned by RuleBuilder.Outputs.
 func (c *RuleBuilderCommand) FlagWithOutput(flag string, path WritablePath) *RuleBuilderCommand {
 	c.outputs = append(c.outputs, path)
-	return c.Text(flag + c.outputStr(path))
+	return c.Text(flag + c.PathForOutput(path))
 }
 
 // FlagWithDepFile adds the specified flag and depfile path to the command line, with no separator between them.  The path
 // will also be added to the outputs returned by RuleBuilder.Outputs.
 func (c *RuleBuilderCommand) FlagWithDepFile(flag string, path WritablePath) *RuleBuilderCommand {
 	c.depFiles = append(c.depFiles, path)
-	return c.Text(flag + c.outputStr(path))
+	return c.Text(flag + c.PathForOutput(path))
 }
 
 // FlagWithRspFileInputList adds the specified flag and path to an rspfile to the command line, with no separator
@@ -987,3 +989,21 @@
 	h.Write([]byte(srcFileList))
 	return fmt.Sprintf("%x", h.Sum(nil))
 }
+
+// BuilderContextForTesting returns a BuilderContext for the given config that can be used for tests
+// that need to call methods that take a BuilderContext.
+func BuilderContextForTesting(config Config) BuilderContext {
+	pathCtx := PathContextForTesting(config)
+	return builderContextForTests{
+		PathContext: pathCtx,
+	}
+}
+
+type builderContextForTests struct {
+	PathContext
+}
+
+func (builderContextForTests) Rule(PackageContext, string, blueprint.RuleParams, ...string) blueprint.Rule {
+	return nil
+}
+func (builderContextForTests) Build(PackageContext, BuildParams) {}
diff --git a/android/rule_builder_test.go b/android/rule_builder_test.go
index dc360c3..e676e4a 100644
--- a/android/rule_builder_test.go
+++ b/android/rule_builder_test.go
@@ -27,8 +27,8 @@
 	"android/soong/shared"
 )
 
-func pathContext() PathContext {
-	return PathContextForTesting(TestConfig("out", nil, "", map[string][]byte{
+func builderContext() BuilderContext {
+	return BuilderContextForTesting(TestConfig("out", nil, "", map[string][]byte{
 		"ld":      nil,
 		"a.o":     nil,
 		"b.o":     nil,
@@ -44,9 +44,9 @@
 }
 
 func ExampleRuleBuilder() {
-	rule := NewRuleBuilder()
+	ctx := builderContext()
 
-	ctx := pathContext()
+	rule := NewRuleBuilder(pctx, ctx)
 
 	rule.Command().
 		Tool(PathForSource(ctx, "ld")).
@@ -55,7 +55,7 @@
 	rule.Command().Text("echo success")
 
 	// To add the command to the build graph:
-	// rule.Build(pctx, ctx, "link", "link")
+	// rule.Build("link", "link")
 
 	fmt.Printf("commands: %q\n", strings.Join(rule.Commands(), " && "))
 	fmt.Printf("tools: %q\n", rule.Tools())
@@ -70,9 +70,9 @@
 }
 
 func ExampleRuleBuilder_SymlinkOutputs() {
-	rule := NewRuleBuilder()
+	ctx := builderContext()
 
-	ctx := pathContext()
+	rule := NewRuleBuilder(pctx, ctx)
 
 	rule.Command().
 		Tool(PathForSource(ctx, "ln")).
@@ -96,9 +96,9 @@
 }
 
 func ExampleRuleBuilder_Temporary() {
-	rule := NewRuleBuilder()
+	ctx := builderContext()
 
-	ctx := pathContext()
+	rule := NewRuleBuilder(pctx, ctx)
 
 	rule.Command().
 		Tool(PathForSource(ctx, "cp")).
@@ -123,9 +123,9 @@
 }
 
 func ExampleRuleBuilder_DeleteTemporaryFiles() {
-	rule := NewRuleBuilder()
+	ctx := builderContext()
 
-	ctx := pathContext()
+	rule := NewRuleBuilder(pctx, ctx)
 
 	rule.Command().
 		Tool(PathForSource(ctx, "cp")).
@@ -151,9 +151,9 @@
 }
 
 func ExampleRuleBuilder_Installs() {
-	rule := NewRuleBuilder()
+	ctx := builderContext()
 
-	ctx := pathContext()
+	rule := NewRuleBuilder(pctx, ctx)
 
 	out := PathForOutput(ctx, "linked")
 
@@ -171,9 +171,9 @@
 }
 
 func ExampleRuleBuilderCommand() {
-	rule := NewRuleBuilder()
+	ctx := builderContext()
 
-	ctx := pathContext()
+	rule := NewRuleBuilder(pctx, ctx)
 
 	// chained
 	rule.Command().
@@ -194,24 +194,24 @@
 }
 
 func ExampleRuleBuilderCommand_Flag() {
-	ctx := pathContext()
-	fmt.Println(NewRuleBuilder().Command().
+	ctx := builderContext()
+	fmt.Println(NewRuleBuilder(pctx, ctx).Command().
 		Tool(PathForSource(ctx, "ls")).Flag("-l"))
 	// Output:
 	// ls -l
 }
 
 func ExampleRuleBuilderCommand_Flags() {
-	ctx := pathContext()
-	fmt.Println(NewRuleBuilder().Command().
+	ctx := builderContext()
+	fmt.Println(NewRuleBuilder(pctx, ctx).Command().
 		Tool(PathForSource(ctx, "ls")).Flags([]string{"-l", "-a"}))
 	// Output:
 	// ls -l -a
 }
 
 func ExampleRuleBuilderCommand_FlagWithArg() {
-	ctx := pathContext()
-	fmt.Println(NewRuleBuilder().Command().
+	ctx := builderContext()
+	fmt.Println(NewRuleBuilder(pctx, ctx).Command().
 		Tool(PathForSource(ctx, "ls")).
 		FlagWithArg("--sort=", "time"))
 	// Output:
@@ -219,8 +219,8 @@
 }
 
 func ExampleRuleBuilderCommand_FlagForEachArg() {
-	ctx := pathContext()
-	fmt.Println(NewRuleBuilder().Command().
+	ctx := builderContext()
+	fmt.Println(NewRuleBuilder(pctx, ctx).Command().
 		Tool(PathForSource(ctx, "ls")).
 		FlagForEachArg("--sort=", []string{"time", "size"}))
 	// Output:
@@ -228,8 +228,8 @@
 }
 
 func ExampleRuleBuilderCommand_FlagForEachInput() {
-	ctx := pathContext()
-	fmt.Println(NewRuleBuilder().Command().
+	ctx := builderContext()
+	fmt.Println(NewRuleBuilder(pctx, ctx).Command().
 		Tool(PathForSource(ctx, "turbine")).
 		FlagForEachInput("--classpath ", PathsForTesting("a.jar", "b.jar")))
 	// Output:
@@ -237,8 +237,8 @@
 }
 
 func ExampleRuleBuilderCommand_FlagWithInputList() {
-	ctx := pathContext()
-	fmt.Println(NewRuleBuilder().Command().
+	ctx := builderContext()
+	fmt.Println(NewRuleBuilder(pctx, ctx).Command().
 		Tool(PathForSource(ctx, "java")).
 		FlagWithInputList("-classpath=", PathsForTesting("a.jar", "b.jar"), ":"))
 	// Output:
@@ -246,8 +246,8 @@
 }
 
 func ExampleRuleBuilderCommand_FlagWithInput() {
-	ctx := pathContext()
-	fmt.Println(NewRuleBuilder().Command().
+	ctx := builderContext()
+	fmt.Println(NewRuleBuilder(pctx, ctx).Command().
 		Tool(PathForSource(ctx, "java")).
 		FlagWithInput("-classpath=", PathForSource(ctx, "a")))
 	// Output:
@@ -255,8 +255,8 @@
 }
 
 func ExampleRuleBuilderCommand_FlagWithList() {
-	ctx := pathContext()
-	fmt.Println(NewRuleBuilder().Command().
+	ctx := builderContext()
+	fmt.Println(NewRuleBuilder(pctx, ctx).Command().
 		Tool(PathForSource(ctx, "ls")).
 		FlagWithList("--sort=", []string{"time", "size"}, ","))
 	// Output:
@@ -264,8 +264,8 @@
 }
 
 func ExampleRuleBuilderCommand_FlagWithRspFileInputList() {
-	ctx := pathContext()
-	fmt.Println(NewRuleBuilder().Command().
+	ctx := builderContext()
+	fmt.Println(NewRuleBuilder(pctx, ctx).Command().
 		Tool(PathForSource(ctx, "javac")).
 		FlagWithRspFileInputList("@", PathsForTesting("a.java", "b.java")).
 		NinjaEscapedString())
@@ -274,7 +274,8 @@
 }
 
 func ExampleRuleBuilderCommand_String() {
-	fmt.Println(NewRuleBuilder().Command().
+	ctx := builderContext()
+	fmt.Println(NewRuleBuilder(pctx, ctx).Command().
 		Text("FOO=foo").
 		Text("echo $FOO").
 		String())
@@ -283,7 +284,8 @@
 }
 
 func ExampleRuleBuilderCommand_NinjaEscapedString() {
-	fmt.Println(NewRuleBuilder().Command().
+	ctx := builderContext()
+	fmt.Println(NewRuleBuilder(pctx, ctx).Command().
 		Text("FOO=foo").
 		Text("echo $FOO").
 		NinjaEscapedString())
@@ -305,7 +307,10 @@
 		"input3":     nil,
 	}
 
-	ctx := PathContextForTesting(TestConfig("out", nil, "", fs))
+	pathCtx := PathContextForTesting(TestConfig("out", nil, "", fs))
+	ctx := builderContextForTests{
+		PathContext: pathCtx,
+	}
 
 	addCommands := func(rule *RuleBuilder) {
 		cmd := rule.Command().
@@ -355,7 +360,7 @@
 	wantSymlinkOutputs := PathsForOutput(ctx, []string{"ImplicitSymlinkOutput", "SymlinkOutput"})
 
 	t.Run("normal", func(t *testing.T) {
-		rule := NewRuleBuilder()
+		rule := NewRuleBuilder(pctx, ctx)
 		addCommands(rule)
 
 		wantCommands := []string{
@@ -389,13 +394,13 @@
 			t.Errorf("\nwant rule.OrderOnlys() = %#v\n                got %#v", w, g)
 		}
 
-		if g, w := rule.depFileMergerCmd(ctx, rule.DepFiles()).String(), wantDepMergerCommand; g != w {
+		if g, w := rule.depFileMergerCmd(rule.DepFiles()).String(), wantDepMergerCommand; g != w {
 			t.Errorf("\nwant rule.depFileMergerCmd() = %#v\n                   got %#v", w, g)
 		}
 	})
 
 	t.Run("sbox", func(t *testing.T) {
-		rule := NewRuleBuilder().Sbox(PathForOutput(ctx, ""),
+		rule := NewRuleBuilder(pctx, ctx).Sbox(PathForOutput(ctx, ""),
 			PathForOutput(ctx, "sbox.textproto"))
 		addCommands(rule)
 
@@ -427,7 +432,7 @@
 			t.Errorf("\nwant rule.OrderOnlys() = %#v\n                got %#v", w, g)
 		}
 
-		if g, w := rule.depFileMergerCmd(ctx, rule.DepFiles()).String(), wantDepMergerCommand; g != w {
+		if g, w := rule.depFileMergerCmd(rule.DepFiles()).String(), wantDepMergerCommand; g != w {
 			t.Errorf("\nwant rule.depFileMergerCmd() = %#v\n                   got %#v", w, g)
 		}
 	})
@@ -476,7 +481,7 @@
 }
 
 func testRuleBuilder_Build(ctx BuilderContext, in Paths, out, outDep, outDir, manifestPath WritablePath, restat, sbox bool) {
-	rule := NewRuleBuilder()
+	rule := NewRuleBuilder(pctx, ctx)
 
 	if sbox {
 		rule.Sbox(outDir, manifestPath)
@@ -488,7 +493,7 @@
 		rule.Restat()
 	}
 
-	rule.Build(pctx, ctx, "rule", "desc")
+	rule.Build("rule", "desc")
 }
 
 func TestRuleBuilder_Build(t *testing.T) {
diff --git a/android/test_suites.go b/android/test_suites.go
index 19444a8..7ecb8d2 100644
--- a/android/test_suites.go
+++ b/android/test_suites.go
@@ -63,13 +63,13 @@
 	testCasesDir := pathForInstall(ctx, BuildOs, X86, "testcases", false).ToMakePath()
 
 	outputFile := PathForOutput(ctx, "packaging", "robolectric-tests.zip")
-	rule := NewRuleBuilder()
-	rule.Command().BuiltTool(ctx, "soong_zip").
+	rule := NewRuleBuilder(pctx, ctx)
+	rule.Command().BuiltTool("soong_zip").
 		FlagWithOutput("-o ", outputFile).
 		FlagWithArg("-P ", "host/testcases").
 		FlagWithArg("-C ", testCasesDir.String()).
 		FlagWithRspFileInputList("-r ", installedPaths.Paths())
-	rule.Build(pctx, ctx, "robolectric_tests_zip", "robolectric-tests.zip")
+	rule.Build("robolectric_tests_zip", "robolectric-tests.zip")
 
 	return outputFile
 }
diff --git a/android/util.go b/android/util.go
index 8e4c0f4..0f940fa 100644
--- a/android/util.go
+++ b/android/util.go
@@ -401,6 +401,23 @@
 	return ret
 }
 
+// ShardString takes a string and returns a slice of strings where the length of each one is
+// at most shardSize.
+func ShardString(s string, shardSize int) []string {
+	if len(s) == 0 {
+		return nil
+	}
+	ret := make([]string, 0, (len(s)+shardSize-1)/shardSize)
+	for len(s) > shardSize {
+		ret = append(ret, s[0:shardSize])
+		s = s[shardSize:]
+	}
+	if len(s) > 0 {
+		ret = append(ret, s)
+	}
+	return ret
+}
+
 // ShardStrings takes a slice of strings, and returns a slice of slices of strings where each one has at most shardSize
 // elements.
 func ShardStrings(s []string, shardSize int) [][]string {
diff --git a/android/variable.go b/android/variable.go
index a9a9c87..0df5272 100644
--- a/android/variable.go
+++ b/android/variable.go
@@ -347,6 +347,9 @@
 
 	EnforceProductPartitionInterface *bool `json:",omitempty"`
 
+	EnforceInterPartitionJavaSdkLibrary *bool    `json:",omitempty"`
+	InterPartitionJavaLibraryAllowList  []string `json:",omitempty"`
+
 	InstallExtraFlattenedApexes *bool `json:",omitempty"`
 
 	BoardUsesRecoveryAsBoot *bool `json:",omitempty"`
diff --git a/apex/apex.go b/apex/apex.go
index f8fb355..72f3db1 100644
--- a/apex/apex.go
+++ b/apex/apex.go
@@ -353,6 +353,9 @@
 	lintReports android.Paths
 
 	prebuiltFileToDelete string
+
+	// Path of API coverage generate file
+	coverageOutputPath android.ModuleOutPath
 }
 
 // apexFileClass represents a type of file that can be included in APEX.
diff --git a/apex/apex_test.go b/apex/apex_test.go
index a94e3b4..cc05fd4 100644
--- a/apex/apex_test.go
+++ b/apex/apex_test.go
@@ -2831,18 +2831,18 @@
 	// non-APEX variant does not have __ANDROID_APEX__ defined
 	mylibCFlags := ctx.ModuleForTests("mylib", "android_arm64_armv8-a_static").Rule("cc").Args["cFlags"]
 	ensureNotContains(t, mylibCFlags, "-D__ANDROID_APEX__")
-	ensureNotContains(t, mylibCFlags, "-D__ANDROID_SDK_VERSION__")
+	ensureNotContains(t, mylibCFlags, "-D__ANDROID_APEX_MIN_SDK_VERSION__")
 
 	// APEX variant has __ANDROID_APEX__ and __ANDROID_APEX_SDK__ defined
 	mylibCFlags = ctx.ModuleForTests("mylib", "android_arm64_armv8-a_static_apex10000").Rule("cc").Args["cFlags"]
 	ensureContains(t, mylibCFlags, "-D__ANDROID_APEX__")
-	ensureContains(t, mylibCFlags, "-D__ANDROID_SDK_VERSION__=10000")
+	ensureContains(t, mylibCFlags, "-D__ANDROID_APEX_MIN_SDK_VERSION__=10000")
 	ensureNotContains(t, mylibCFlags, "-D__ANDROID_APEX_MYAPEX__")
 
 	// APEX variant has __ANDROID_APEX__ and __ANDROID_APEX_SDK__ defined
 	mylibCFlags = ctx.ModuleForTests("mylib", "android_arm64_armv8-a_static_apex29").Rule("cc").Args["cFlags"]
 	ensureContains(t, mylibCFlags, "-D__ANDROID_APEX__")
-	ensureContains(t, mylibCFlags, "-D__ANDROID_SDK_VERSION__=29")
+	ensureContains(t, mylibCFlags, "-D__ANDROID_APEX_MIN_SDK_VERSION__=29")
 	ensureNotContains(t, mylibCFlags, "-D__ANDROID_APEX_OTHERAPEX__")
 
 	// When a cc_library sets use_apex_name_macro: true each apex gets a unique variant and
@@ -2864,10 +2864,10 @@
 	ensureNotContains(t, mylibCFlags, "-D__ANDROID_APEX_MYAPEX__")
 	ensureContains(t, mylibCFlags, "-D__ANDROID_APEX_OTHERAPEX__")
 
-	// recovery variant does not set __ANDROID_SDK_VERSION__
+	// recovery variant does not set __ANDROID_APEX_MIN_SDK_VERSION__
 	mylibCFlags = ctx.ModuleForTests("mylib3", "android_recovery_arm64_armv8-a_static").Rule("cc").Args["cFlags"]
 	ensureNotContains(t, mylibCFlags, "-D__ANDROID_APEX__")
-	ensureNotContains(t, mylibCFlags, "-D__ANDROID_SDK_VERSION__")
+	ensureNotContains(t, mylibCFlags, "-D__ANDROID_APEX_MIN_SDK_VERSION__")
 
 	// When a dependency of a cc_library sets use_apex_name_macro: true each apex gets a unique
 	// variant.
@@ -2888,10 +2888,10 @@
 	ensureNotContains(t, mylibCFlags, "-D__ANDROID_APEX_MYAPEX__")
 	ensureNotContains(t, mylibCFlags, "-D__ANDROID_APEX_OTHERAPEX__")
 
-	// recovery variant does not set __ANDROID_SDK_VERSION__
+	// recovery variant does not set __ANDROID_APEX_MIN_SDK_VERSION__
 	mylibCFlags = ctx.ModuleForTests("mylib2", "android_recovery_arm64_armv8-a_static").Rule("cc").Args["cFlags"]
 	ensureNotContains(t, mylibCFlags, "-D__ANDROID_APEX__")
-	ensureNotContains(t, mylibCFlags, "-D__ANDROID_SDK_VERSION__")
+	ensureNotContains(t, mylibCFlags, "-D__ANDROID_APEX_MIN_SDK_VERSION__")
 }
 
 func TestHeaderLibsDependency(t *testing.T) {
diff --git a/apex/builder.go b/apex/builder.go
index b858135..66eaff1 100644
--- a/apex/builder.go
+++ b/apex/builder.go
@@ -37,6 +37,7 @@
 
 func init() {
 	pctx.Import("android/soong/android")
+	pctx.Import("android/soong/cc/config")
 	pctx.Import("android/soong/java")
 	pctx.HostBinToolVariable("apexer", "apexer")
 	// ART minimal builds (using the master-art manifest) do not have the "frameworks/base"
@@ -65,6 +66,7 @@
 	pctx.HostBinToolVariable("extract_apks", "extract_apks")
 	pctx.HostBinToolVariable("make_f2fs", "make_f2fs")
 	pctx.HostBinToolVariable("sload_f2fs", "sload_f2fs")
+	pctx.SourcePathVariable("genNdkUsedbyApexPath", "build/soong/scripts/gen_ndk_usedby_apex.sh")
 }
 
 var (
@@ -176,6 +178,12 @@
 		Description: "Diff ${image_content_file} and ${allowed_files_file}",
 	}, "image_content_file", "allowed_files_file", "apex_module_name")
 
+	generateAPIsUsedbyApexRule = pctx.StaticRule("generateAPIsUsedbyApexRule", blueprint.RuleParams{
+		Command:     "$genNdkUsedbyApexPath ${image_dir} ${readelf} ${out}",
+		CommandDeps: []string{"${genNdkUsedbyApexPath}"},
+		Description: "Generate symbol list used by Apex",
+	}, "image_dir", "readelf")
+
 	// Don't add more rules here. Consider using android.NewRuleBuilder instead.
 )
 
@@ -262,7 +270,7 @@
 	}
 
 	output := android.PathForModuleOut(ctx, "file_contexts")
-	rule := android.NewRuleBuilder()
+	rule := android.NewRuleBuilder(pctx, ctx)
 
 	switch a.properties.ApexType {
 	case imageApex:
@@ -294,7 +302,7 @@
 		panic(fmt.Errorf("unsupported type %v", a.properties.ApexType))
 	}
 
-	rule.Build(pctx, ctx, "file_contexts."+a.Name(), "Generate file_contexts")
+	rule.Build("file_contexts."+a.Name(), "Generate file_contexts")
 	return output.OutputPath
 }
 
@@ -329,14 +337,14 @@
 // included in the APEX without actually downloading and extracting it.
 func (a *apexBundle) buildInstalledFilesFile(ctx android.ModuleContext, builtApex android.Path, imageDir android.Path) android.OutputPath {
 	output := android.PathForModuleOut(ctx, "installed-files.txt")
-	rule := android.NewRuleBuilder()
+	rule := android.NewRuleBuilder(pctx, ctx)
 	rule.Command().
 		Implicit(builtApex).
 		Text("(cd " + imageDir.String() + " ; ").
 		Text("find . \\( -type f -o -type l \\) -printf \"%s %p\\n\") ").
 		Text(" | sort -nr > ").
 		Output(output)
-	rule.Build(pctx, ctx, "installed-files."+a.Name(), "Installed files")
+	rule.Build("installed-files."+a.Name(), "Installed files")
 	return output.OutputPath
 }
 
@@ -675,6 +683,22 @@
 			Description: "apex proto convert",
 		})
 
+		implicitInputs = append(implicitInputs, unsignedOutputFile)
+
+		// Run coverage analysis
+		apisUsedbyOutputFile := android.PathForModuleOut(ctx, a.Name()+".txt")
+		ctx.Build(pctx, android.BuildParams{
+			Rule:        generateAPIsUsedbyApexRule,
+			Implicits:   implicitInputs,
+			Description: "coverage",
+			Output:      apisUsedbyOutputFile,
+			Args: map[string]string{
+				"image_dir": imageDir.String(),
+				"readelf":   "${config.ClangBin}/llvm-readelf",
+			},
+		})
+		a.coverageOutputPath = apisUsedbyOutputFile
+
 		bundleConfig := a.buildBundleConfig(ctx)
 
 		var abis []string
diff --git a/cc/binary.go b/cc/binary.go
index fbd293e..fa3966f 100644
--- a/cc/binary.go
+++ b/cc/binary.go
@@ -373,7 +373,7 @@
 	if String(binary.Properties.Prefix_symbols) != "" {
 		afterPrefixSymbols := outputFile
 		outputFile = android.PathForModuleOut(ctx, "unprefixed", fileName)
-		TransformBinaryPrefixSymbols(ctx, String(binary.Properties.Prefix_symbols), outputFile,
+		transformBinaryPrefixSymbols(ctx, String(binary.Properties.Prefix_symbols), outputFile,
 			builderFlags, afterPrefixSymbols)
 	}
 
@@ -428,13 +428,13 @@
 	linkerDeps = append(linkerDeps, flags.LdFlagsDeps...)
 
 	// Register link action.
-	TransformObjToDynamicBinary(ctx, objs.objFiles, sharedLibs, deps.StaticLibs,
+	transformObjToDynamicBinary(ctx, objs.objFiles, sharedLibs, deps.StaticLibs,
 		deps.LateStaticLibs, deps.WholeStaticLibs, linkerDeps, deps.CrtBegin, deps.CrtEnd, true,
 		builderFlags, outputFile, nil)
 
 	objs.coverageFiles = append(objs.coverageFiles, deps.StaticLibObjs.coverageFiles...)
 	objs.coverageFiles = append(objs.coverageFiles, deps.WholeStaticLibObjs.coverageFiles...)
-	binary.coverageOutputFile = TransformCoverageFilesToZip(ctx, objs, binary.getStem(ctx))
+	binary.coverageOutputFile = transformCoverageFilesToZip(ctx, objs, binary.getStem(ctx))
 
 	// Need to determine symlinks early since some targets (ie APEX) need this
 	// information but will not call 'install'
diff --git a/cc/builder.go b/cc/builder.go
index 81c09b1..439e372 100644
--- a/cc/builder.go
+++ b/cc/builder.go
@@ -19,7 +19,6 @@
 // functions.
 
 import (
-	"fmt"
 	"path/filepath"
 	"runtime"
 	"strings"
@@ -40,6 +39,7 @@
 var (
 	pctx = android.NewPackageContext("android/soong/cc")
 
+	// Rule to invoke gcc with given command, flags, and dependencies. Outputs a .d depfile.
 	cc = pctx.AndroidRemoteStaticRule("cc", android.RemoteRuleSupports{Goma: true, RBE: true},
 		blueprint.RuleParams{
 			Depfile:     "${out}.d",
@@ -49,6 +49,7 @@
 		},
 		"ccCmd", "cFlags")
 
+	// Rule to invoke gcc with given command and flags, but no dependencies.
 	ccNoDeps = pctx.AndroidStaticRule("ccNoDeps",
 		blueprint.RuleParams{
 			Command:     "$relPwd $ccCmd -c $cFlags -o $out $in",
@@ -56,6 +57,8 @@
 		},
 		"ccCmd", "cFlags")
 
+	// Rules to invoke ld to link binaries. Uses a .rsp file to list dependencies, as there may
+	// be many.
 	ld, ldRE = remoteexec.StaticRules(pctx, "ld",
 		blueprint.RuleParams{
 			Command: "$reTemplate$ldCmd ${crtBegin} @${out}.rsp " +
@@ -76,6 +79,7 @@
 			Platform:        map[string]string{remoteexec.PoolKey: "${config.RECXXLinksPool}"},
 		}, []string{"ldCmd", "crtBegin", "libFlags", "crtEnd", "ldFlags", "extraLibFlags"}, []string{"implicitInputs", "implicitOutputs"})
 
+	// Rules for .o files to combine to other .o files, using ld partial linking.
 	partialLd, partialLdRE = remoteexec.StaticRules(pctx, "partialLd",
 		blueprint.RuleParams{
 			// Without -no-pie, clang 7.0 adds -pie to link Android files,
@@ -91,6 +95,7 @@
 			Platform:        map[string]string{remoteexec.PoolKey: "${config.RECXXLinksPool}"},
 		}, []string{"ldCmd", "ldFlags"}, []string{"implicitInputs", "inCommaList", "implicitOutputs"})
 
+	// Rule to invoke `ar` with given cmd and flags, but no static library depenencies.
 	ar = pctx.AndroidStaticRule("ar",
 		blueprint.RuleParams{
 			Command:        "rm -f ${out} && $arCmd $arFlags $out @${out}.rsp",
@@ -100,6 +105,8 @@
 		},
 		"arCmd", "arFlags")
 
+	// Rule to invoke `ar` with given cmd, flags, and library dependencies. Generates a .a
+	// (archive) file from .o files.
 	arWithLibs = pctx.AndroidStaticRule("arWithLibs",
 		blueprint.RuleParams{
 			Command:        "rm -f ${out} && $arCmd $arObjFlags $out @${out}.rsp && $arCmd $arLibFlags $out $arLibs",
@@ -109,12 +116,7 @@
 		},
 		"arCmd", "arObjFlags", "arObjs", "arLibFlags", "arLibs")
 
-	darwinStrip = pctx.AndroidStaticRule("darwinStrip",
-		blueprint.RuleParams{
-			Command:     "${config.MacStripPath} -u -r -o $out $in",
-			CommandDeps: []string{"${config.MacStripPath}"},
-		})
-
+	// Rule to run objcopy --prefix-symbols (to prefix all symbols in a file with a given string).
 	prefixSymbols = pctx.AndroidStaticRule("prefixSymbols",
 		blueprint.RuleParams{
 			Command:     "$objcopyCmd --prefix-symbols=${prefix} ${in} ${out}",
@@ -125,6 +127,24 @@
 	_ = pctx.SourcePathVariable("stripPath", "build/soong/scripts/strip.sh")
 	_ = pctx.SourcePathVariable("xzCmd", "prebuilts/build-tools/${config.HostPrebuiltTag}/bin/xz")
 
+	// Rule to invoke `strip` (to discard symbols and data from object files).
+	strip = pctx.AndroidStaticRule("strip",
+		blueprint.RuleParams{
+			Depfile:     "${out}.d",
+			Deps:        blueprint.DepsGCC,
+			Command:     "CROSS_COMPILE=$crossCompile XZ=$xzCmd CLANG_BIN=${config.ClangBin} $stripPath ${args} -i ${in} -o ${out} -d ${out}.d",
+			CommandDeps: []string{"$stripPath", "$xzCmd"},
+			Pool:        darwinStripPool,
+		},
+		"args", "crossCompile")
+
+	// Rule to invoke `strip` (to discard symbols and data from object files) on darwin architecture.
+	darwinStrip = pctx.AndroidStaticRule("darwinStrip",
+		blueprint.RuleParams{
+			Command:     "${config.MacStripPath} -u -r -o $out $in",
+			CommandDeps: []string{"${config.MacStripPath}"},
+		})
+
 	// b/132822437: objcopy uses a file descriptor per .o file when called on .a files, which runs the system out of
 	// file descriptors on darwin.  Limit concurrent calls to 5 on darwin.
 	darwinStripPool = func() blueprint.Pool {
@@ -137,18 +157,9 @@
 		}
 	}()
 
-	strip = pctx.AndroidStaticRule("strip",
-		blueprint.RuleParams{
-			Depfile:     "${out}.d",
-			Deps:        blueprint.DepsGCC,
-			Command:     "CROSS_COMPILE=$crossCompile XZ=$xzCmd CLANG_BIN=${config.ClangBin} $stripPath ${args} -i ${in} -o ${out} -d ${out}.d",
-			CommandDeps: []string{"$stripPath", "$xzCmd"},
-			Pool:        darwinStripPool,
-		},
-		"args", "crossCompile")
-
 	_ = pctx.SourcePathVariable("archiveRepackPath", "build/soong/scripts/archive_repack.sh")
 
+	// Rule to repack an archive (.a) file with a subset of object files.
 	archiveRepack = pctx.AndroidStaticRule("archiveRepack",
 		blueprint.RuleParams{
 			Depfile:     "${out}.d",
@@ -158,6 +169,7 @@
 		},
 		"objects")
 
+	// Rule to create an empty file at a given path.
 	emptyFile = pctx.AndroidStaticRule("emptyFile",
 		blueprint.RuleParams{
 			Command: "rm -f $out && touch $out",
@@ -165,6 +177,7 @@
 
 	_ = pctx.SourcePathVariable("tocPath", "build/soong/scripts/toc.sh")
 
+	// A rule for extracting a table of contents from a shared library (.so).
 	toc = pctx.AndroidStaticRule("toc",
 		blueprint.RuleParams{
 			Depfile:     "${out}.d",
@@ -175,6 +188,7 @@
 		},
 		"crossCompile", "format")
 
+	// Rule for invoking clang-tidy (a clang-based linter).
 	clangTidy, clangTidyRE = remoteexec.StaticRules(pctx, "clangTidy",
 		blueprint.RuleParams{
 			Command:     "rm -f $out && $reTemplate${config.ClangBin}/clang-tidy $tidyFlags $in -- $cFlags && touch $out",
@@ -193,6 +207,7 @@
 
 	_ = pctx.SourcePathVariable("yasmCmd", "prebuilts/misc/${config.HostPrebuiltTag}/yasm/yasm")
 
+	// Rule for invoking yasm to compile .asm assembly files.
 	yasm = pctx.AndroidStaticRule("yasm",
 		blueprint.RuleParams{
 			Command:     "$yasmCmd $asFlags -o $out $in && $yasmCmd $asFlags -M $in >$out.d",
@@ -202,6 +217,7 @@
 		},
 		"asFlags")
 
+	// Rule to invoke windres, for interaction with Windows resources.
 	windres = pctx.AndroidStaticRule("windres",
 		blueprint.RuleParams{
 			Command:     "$windresCmd $flags -I$$(dirname $in) -i $in -o $out --preprocessor \"${config.ClangBin}/clang -E -xc-header -DRC_INVOKED\"",
@@ -220,13 +236,15 @@
 			Labels:       map[string]string{"type": "abi-dump", "tool": "header-abi-dumper"},
 			ExecStrategy: "${config.REAbiDumperExecStrategy}",
 			Platform: map[string]string{
-				remoteexec.PoolKey:      "${config.RECXXPool}",
+				remoteexec.PoolKey: "${config.RECXXPool}",
 			},
 		}, []string{"cFlags", "exportDirs"}, nil)
 
 	_ = pctx.SourcePathVariable("sAbiLinker", "prebuilts/clang-tools/${config.HostPrebuiltTag}/bin/header-abi-linker")
 	_ = pctx.SourcePathVariable("sAbiLinkerLibs", "prebuilts/clang-tools/${config.HostPrebuiltTag}/lib64")
 
+	// Rule to combine .dump sAbi dump files from multiple source files into a single .ldump
+	// sAbi dump file.
 	sAbiLink, sAbiLinkRE = remoteexec.StaticRules(pctx, "sAbiLink",
 		blueprint.RuleParams{
 			Command:        "$reTemplate$sAbiLinker -o ${out} $symbolFilter -arch $arch  $exportedHeaderFlags @${out}.rsp ",
@@ -245,6 +263,7 @@
 
 	_ = pctx.SourcePathVariable("sAbiDiffer", "prebuilts/clang-tools/${config.HostPrebuiltTag}/bin/header-abi-diff")
 
+	// Rule to compare linked sAbi dump files (.ldump).
 	sAbiDiff = pctx.RuleFunc("sAbiDiff",
 		func(ctx android.PackageRuleContext) blueprint.RuleParams {
 			commandStr := "($sAbiDiffer ${extraFlags} -lib ${libName} -arch ${arch} -o ${out} -new ${in} -old ${referenceDump})"
@@ -258,11 +277,13 @@
 		},
 		"extraFlags", "referenceDump", "libName", "arch", "createReferenceDumpFlags")
 
+	// Rule to unzip a reference abi dump.
 	unzipRefSAbiDump = pctx.AndroidStaticRule("unzipRefSAbiDump",
 		blueprint.RuleParams{
 			Command: "gunzip -c $in > $out",
 		})
 
+	// Rule to zip files.
 	zip = pctx.AndroidStaticRule("zip",
 		blueprint.RuleParams{
 			Command:        "${SoongZipCmd} -o ${out} -C $$OUT_DIR -r ${out}.rsp",
@@ -278,6 +299,8 @@
 		func(ctx android.PackageVarContext) string { return ctx.Config().XrefCorpusName() })
 	_ = pctx.VariableFunc("kytheCuEncoding",
 		func(ctx android.PackageVarContext) string { return ctx.Config().XrefCuEncoding() })
+
+	// Rule to use kythe extractors to generate .kzip files, used to build code cross references.
 	kytheExtract = pctx.StaticRule("kythe",
 		blueprint.RuleParams{
 			Command: `rm -f $out && ` +
@@ -310,7 +333,11 @@
 	pctx.Import("android/soong/remoteexec")
 }
 
+// builderFlags contains various types of command line flags (and settings) for use in building
+// build statements related to C++.
 type builderFlags struct {
+	// Global flags (which build system or toolchain is responsible for). These are separate from
+	// local flags because they should appear first (so that they may be overridden by local flags).
 	globalCommonFlags     string
 	globalAsFlags         string
 	globalYasmFlags       string
@@ -321,6 +348,7 @@
 	globalCppFlags        string
 	globalLdFlags         string
 
+	// Local flags (which individual modules are responsible for). These may override global flags.
 	localCommonFlags     string
 	localAsFlags         string
 	localYasmFlags       string
@@ -331,32 +359,37 @@
 	localCppFlags        string
 	localLdFlags         string
 
-	libFlags      string
-	extraLibFlags string
-	tidyFlags     string
-	sAbiFlags     string
-	aidlFlags     string
-	rsFlags       string
+	libFlags      string // Flags to add to the linker directly after specifying libraries to link.
+	extraLibFlags string // Flags to add to the linker last.
+	tidyFlags     string // Flags that apply to clang-tidy
+	sAbiFlags     string // Flags that apply to header-abi-dumps
+	aidlFlags     string // Flags that apply to aidl source files
+	rsFlags       string // Flags that apply to renderscript source files
 	toolchain     config.Toolchain
-	tidy          bool
-	gcovCoverage  bool
-	sAbiDump      bool
-	emitXrefs     bool
 
-	assemblerWithCpp bool
+	// True if these extra features are enabled.
+	tidy         bool
+	gcovCoverage bool
+	sAbiDump     bool
+	emitXrefs    bool
+
+	assemblerWithCpp bool // True if .s files should be processed with the c preprocessor.
 
 	systemIncludeFlags string
 
+	// True if static libraries should be grouped (using `-Wl,--start-group` and `-Wl,--end-group`).
 	groupStaticLibs bool
 
 	proto            android.ProtoFlags
-	protoC           bool
-	protoOptionsFile bool
+	protoC           bool // If true, compile protos as `.c` files. Otherwise, output as `.cc`.
+	protoOptionsFile bool // If true, output a proto options file.
 
 	yacc *YaccProperties
 	lex  *LexProperties
 }
 
+// StripFlags represents flags related to stripping. This is separate from builderFlags, as these
+// flags are useful outside of this package (such as for Rust).
 type StripFlags struct {
 	Toolchain                     config.Toolchain
 	StripKeepSymbols              bool
@@ -367,6 +400,7 @@
 	StripUseGnuStrip              bool
 }
 
+// Objects is a collection of file paths corresponding to outputs for C++ related build statements.
 type Objects struct {
 	objFiles      android.Paths
 	tidyFiles     android.Paths
@@ -396,9 +430,10 @@
 }
 
 // Generate rules for compiling multiple .c, .cpp, or .S files to individual .o files
-func TransformSourceToObj(ctx android.ModuleContext, subdir string, srcFiles android.Paths,
+func transformSourceToObj(ctx android.ModuleContext, subdir string, srcFiles android.Paths,
 	flags builderFlags, pathDeps android.Paths, cFlagsDeps android.Paths) Objects {
 
+	// Source files are one-to-one with tidy, coverage, or kythe files, if enabled.
 	objFiles := make(android.Paths, len(srcFiles))
 	var tidyFiles android.Paths
 	if flags.tidy {
@@ -468,6 +503,7 @@
 
 		objFiles[i] = objFile
 
+		// Register compilation build statements. The actual rule used depends on the source file type.
 		switch srcFile.Ext() {
 		case ".asm":
 			ctx.Build(pctx, android.BuildParams{
@@ -562,6 +598,7 @@
 			},
 		})
 
+		// Register post-process build statements (such as for tidy or kythe).
 		if emitXref {
 			kytheFile := android.ObjPathWithExt(ctx, subdir, srcFile, "kzip")
 			ctx.Build(pctx, android.BuildParams{
@@ -639,7 +676,7 @@
 }
 
 // Generate a rule for compiling multiple .o files to a static library (.a)
-func TransformObjToStaticLib(ctx android.ModuleContext,
+func transformObjToStaticLib(ctx android.ModuleContext,
 	objFiles android.Paths, wholeStaticLibs android.Paths,
 	flags builderFlags, outputFile android.ModuleOutPath, deps android.Paths) {
 
@@ -682,7 +719,7 @@
 
 // Generate a rule for compiling multiple .o files, plus static libraries, whole static libraries,
 // and shared libraries, to a shared library (.so) or dynamic executable
-func TransformObjToDynamicBinary(ctx android.ModuleContext,
+func transformObjToDynamicBinary(ctx android.ModuleContext,
 	objFiles, sharedLibs, staticLibs, lateStaticLibs, wholeStaticLibs, deps android.Paths,
 	crtBegin, crtEnd android.OptionalPath, groupLate bool, flags builderFlags, outputFile android.WritablePath, implicitOutputs android.WritablePaths) {
 
@@ -763,7 +800,7 @@
 
 // Generate a rule to combine .dump sAbi dump files from multiple source files
 // into a single .ldump sAbi dump file
-func TransformDumpToLinkedDump(ctx android.ModuleContext, sAbiDumps android.Paths, soFile android.Path,
+func transformDumpToLinkedDump(ctx android.ModuleContext, sAbiDumps android.Paths, soFile android.Path,
 	baseName, exportedHeaderFlags string, symbolFile android.OptionalPath,
 	excludedSymbolVersions, excludedSymbolTags []string) android.OptionalPath {
 
@@ -810,7 +847,8 @@
 	return android.OptionalPathForPath(outputFile)
 }
 
-func UnzipRefDump(ctx android.ModuleContext, zippedRefDump android.Path, baseName string) android.Path {
+// unzipRefDump registers a build statement to unzip a reference abi dump.
+func unzipRefDump(ctx android.ModuleContext, zippedRefDump android.Path, baseName string) android.Path {
 	outputFile := android.PathForModuleOut(ctx, baseName+"_ref.lsdump")
 	ctx.Build(pctx, android.BuildParams{
 		Rule:        unzipRefSAbiDump,
@@ -821,7 +859,8 @@
 	return outputFile
 }
 
-func SourceAbiDiff(ctx android.ModuleContext, inputDump android.Path, referenceDump android.Path,
+// sourceAbiDiff registers a build statement to compare linked sAbi dump files (.ldump).
+func sourceAbiDiff(ctx android.ModuleContext, inputDump android.Path, referenceDump android.Path,
 	baseName, exportedHeaderFlags string, checkAllApis, isLlndk, isNdk, isVndkExt bool) android.OptionalPath {
 
 	outputFile := android.PathForModuleOut(ctx, baseName+".abidiff")
@@ -872,7 +911,7 @@
 }
 
 // Generate a rule for extracting a table of contents from a shared library (.so)
-func TransformSharedObjectToToc(ctx android.ModuleContext, inputFile android.Path,
+func transformSharedObjectToToc(ctx android.ModuleContext, inputFile android.Path,
 	outputFile android.WritablePath, flags builderFlags) {
 
 	var format string
@@ -901,7 +940,7 @@
 }
 
 // Generate a rule for compiling multiple .o files to a .o using ld partial linking
-func TransformObjsToObj(ctx android.ModuleContext, objFiles android.Paths,
+func transformObjsToObj(ctx android.ModuleContext, objFiles android.Paths,
 	flags builderFlags, outputFile android.WritablePath, deps android.Paths) {
 
 	ldCmd := "${config.ClangBin}/clang++"
@@ -926,8 +965,8 @@
 	})
 }
 
-// Generate a rule for runing objcopy --prefix-symbols on a binary
-func TransformBinaryPrefixSymbols(ctx android.ModuleContext, prefix string, inputFile android.Path,
+// Generate a rule for running objcopy --prefix-symbols on a binary
+func transformBinaryPrefixSymbols(ctx android.ModuleContext, prefix string, inputFile android.Path,
 	flags builderFlags, outputFile android.WritablePath) {
 
 	objcopyCmd := gccCmd(flags.toolchain, "objcopy")
@@ -944,7 +983,8 @@
 	})
 }
 
-func TransformStrip(ctx android.ModuleContext, inputFile android.Path,
+// Registers a build statement to invoke `strip` (to discard symbols and data from object files).
+func transformStrip(ctx android.ModuleContext, inputFile android.Path,
 	outputFile android.WritablePath, flags StripFlags) {
 
 	crossCompile := gccCmd(flags.Toolchain, "")
@@ -980,7 +1020,8 @@
 	})
 }
 
-func TransformDarwinStrip(ctx android.ModuleContext, inputFile android.Path,
+// Registers build statement to invoke `strip` on darwin architecture.
+func transformDarwinStrip(ctx android.ModuleContext, inputFile android.Path,
 	outputFile android.WritablePath) {
 
 	ctx.Build(pctx, android.BuildParams{
@@ -991,7 +1032,8 @@
 	})
 }
 
-func TransformCoverageFilesToZip(ctx android.ModuleContext,
+// Registers build statement to zip one or more coverage files.
+func transformCoverageFilesToZip(ctx android.ModuleContext,
 	inputs Objects, baseName string) android.OptionalPath {
 
 	if len(inputs.coverageFiles) > 0 {
@@ -1010,7 +1052,8 @@
 	return android.OptionalPath{}
 }
 
-func TransformArchiveRepack(ctx android.ModuleContext, inputFile android.Path,
+// Rule to repack an archive (.a) file with a subset of object files.
+func transformArchiveRepack(ctx android.ModuleContext, inputFile android.Path,
 	outputFile android.WritablePath, objects []string) {
 
 	ctx.Build(pctx, android.BuildParams{
@@ -1027,33 +1070,3 @@
 func gccCmd(toolchain config.Toolchain, cmd string) string {
 	return filepath.Join(toolchain.GccRoot(), "bin", toolchain.GccTriple()+"-"+cmd)
 }
-
-func splitListForSize(list android.Paths, limit int) (lists []android.Paths, err error) {
-	var i int
-
-	start := 0
-	bytes := 0
-	for i = range list {
-		l := len(list[i].String())
-		if l > limit {
-			return nil, fmt.Errorf("list element greater than size limit (%d)", limit)
-		}
-		if bytes+l > limit {
-			lists = append(lists, list[start:i])
-			start = i
-			bytes = 0
-		}
-		bytes += l + 1 // count a space between each list element
-	}
-
-	lists = append(lists, list[start:])
-
-	totalLen := 0
-	for _, l := range lists {
-		totalLen += len(l)
-	}
-	if totalLen != len(list) {
-		panic(fmt.Errorf("Failed breaking up list, %d != %d", len(list), totalLen))
-	}
-	return lists, nil
-}
diff --git a/cc/cc.go b/cc/cc.go
index 5f028b8..f62df3c 100644
--- a/cc/cc.go
+++ b/cc/cc.go
@@ -91,6 +91,14 @@
 	ctx.RegisterSingletonType("kythe_extract_all", kytheExtractAllFactory)
 }
 
+// Deps is a struct containing module names of dependencies, separated by the kind of dependency.
+// Mutators should use `AddVariationDependencies` or its sibling methods to add actual dependency
+// edges to these modules.
+// This object is constructed in DepsMutator, by calling to various module delegates to set
+// relevant fields. For example, `module.compiler.compilerDeps()` may append type-specific
+// dependencies.
+// This is then consumed by the same DepsMutator, which will call `ctx.AddVariationDependencies()`
+// (or its sibling methods) to set real dependencies on the given modules.
 type Deps struct {
 	SharedLibs, LateSharedLibs                  []string
 	StaticLibs, LateStaticLibs, WholeStaticLibs []string
@@ -103,6 +111,7 @@
 	// Used by DepsMutator to pass system_shared_libs information to check_elf_file.py.
 	SystemSharedLibs []string
 
+	// If true, statically link the unwinder into native libraries/binaries.
 	StaticUnwinderIfLegacy bool
 
 	ReexportSharedLibHeaders, ReexportStaticLibHeaders, ReexportHeaderLibHeaders []string
@@ -122,6 +131,11 @@
 	DynamicLinker   string
 }
 
+// PathDeps is a struct containing file paths to dependencies of a module.
+// It's constructed in depsToPath() by traversing the direct dependencies of the current module.
+// It's used to construct flags for various build statements (such as for compiling and linking).
+// It is then passed to module decorator functions responsible for registering build statements
+// (such as `module.compiler.compile()`).`
 type PathDeps struct {
 	// Paths to .so files
 	SharedLibs, EarlySharedLibs, LateSharedLibs android.Paths
@@ -182,8 +196,12 @@
 	LdFlags         []string // Flags that apply to linker command lines
 }
 
+// Flags contains various types of command line flags (and settings) for use in building build
+// statements related to C++.
 type Flags struct {
-	Local  LocalOrGlobalFlags
+	// Local flags (which individual modules are responsible for). These may override global flags.
+	Local LocalOrGlobalFlags
+	// Global flags (which build system or toolchain is responsible for).
 	Global LocalOrGlobalFlags
 
 	aidlFlags     []string // Flags that apply to aidl source files
@@ -198,19 +216,23 @@
 	SystemIncludeFlags []string
 
 	Toolchain    config.Toolchain
-	Tidy         bool
-	GcovCoverage bool
-	SAbiDump     bool
+	Tidy         bool // True if clang-tidy is enabled.
+	GcovCoverage bool // True if coverage files should be generated.
+	SAbiDump     bool // True if header abi dumps should be generated.
 	EmitXrefs    bool // If true, generate Ninja rules to generate emitXrefs input files for Kythe
 
+	// The instruction set required for clang ("arm" or "thumb").
 	RequiredInstructionSet string
-	DynamicLinker          string
+	// The target-device system path to the dynamic linker.
+	DynamicLinker string
 
 	CFlagsDeps  android.Paths // Files depended on by compiler flags
 	LdFlagsDeps android.Paths // Files depended on by linker flags
 
+	// True if .s files should be processed with the c preprocessor.
 	AssemblerWithCpp bool
-	GroupStaticLibs  bool
+	// True if static libraries should be grouped (using `-Wl,--start-group` and `-Wl,--end-group`).
+	GroupStaticLibs bool
 
 	proto            android.ProtoFlags
 	protoC           bool // Whether to use C instead of C++
@@ -358,6 +380,10 @@
 	Double_loadable *bool
 }
 
+// ModuleContextIntf is an interface (on a module context helper) consisting of functions related
+// to understanding  details about the type of the current module.
+// For example, one might call these functions to determine whether the current module is a static
+// library and/or is installed in vendor directories.
 type ModuleContextIntf interface {
 	static() bool
 	staticBinary() bool
@@ -412,6 +438,8 @@
 	ModuleContextIntf
 }
 
+// feature represents additional (optional) steps to building cc-related modules, such as invocation
+// of clang-tidy.
 type feature interface {
 	begin(ctx BaseModuleContext)
 	deps(ctx DepsContext, deps Deps) Deps
@@ -419,6 +447,9 @@
 	props() []interface{}
 }
 
+// compiler is the interface for a compiler helper object. Different module decorators may implement
+// this helper differently. For example, compiling a `cc_library` may use a different build
+// statement than building a `toolchain_library`.
 type compiler interface {
 	compilerInit(ctx BaseModuleContext)
 	compilerDeps(ctx DepsContext, deps Deps) Deps
@@ -430,6 +461,9 @@
 	compile(ctx ModuleContext, flags Flags, deps PathDeps) Objects
 }
 
+// linker is the interface for a linker decorator object. Individual module types can provide
+// their own implementation for this decorator, and thus specify custom logic regarding build
+// statements pertaining to linking.
 type linker interface {
 	linkerInit(ctx BaseModuleContext)
 	linkerDeps(ctx DepsContext, deps Deps) Deps
@@ -445,15 +479,19 @@
 	coverageOutputFilePath() android.OptionalPath
 
 	// Get the deps that have been explicitly specified in the properties.
-	// Only updates the
 	linkerSpecifiedDeps(specifiedDeps specifiedDeps) specifiedDeps
 }
 
+// specifiedDeps is a tuple struct representing dependencies of a linked binary owned by the linker.
 type specifiedDeps struct {
-	sharedLibs       []string
-	systemSharedLibs []string // Note nil and [] are semantically distinct.
+	sharedLibs []string
+	// Note nil and [] are semantically distinct. [] prevents linking against the defaults (usually
+	// libc, libm, etc.)
+	systemSharedLibs []string
 }
 
+// installer is the interface for an installer helper object. This helper is responsible for
+// copying build outputs to the appropriate locations so that they may be installed on device.
 type installer interface {
 	installerProps() []interface{}
 	install(ctx ModuleContext, path android.Path)
@@ -584,7 +622,7 @@
 	genHeaderExportDepTag = dependencyTag{name: "gen header export"}
 	objDepTag             = dependencyTag{name: "obj"}
 	linkerFlagsDepTag     = dependencyTag{name: "linker flags file"}
-	dynamicLinkerDepTag   = dependencyTag{name: "dynamic linker"}
+	dynamicLinkerDepTag   = installDependencyTag{name: "dynamic linker"}
 	reuseObjTag           = dependencyTag{name: "reuse objects"}
 	staticVariantTag      = dependencyTag{name: "static variant"}
 	vndkExtDepTag         = dependencyTag{name: "vndk extends"}
@@ -626,7 +664,18 @@
 
 // Module contains the properties and members used by all C/C++ module types, and implements
 // the blueprint.Module interface.  It delegates to compiler, linker, and installer interfaces
-// to construct the output file.  Behavior can be customized with a Customizer interface
+// to construct the output file.  Behavior can be customized with a Customizer, or "decorator",
+// interface.
+//
+// To define a C/C++ related module, construct a new Module object and point its delegates to
+// type-specific structs. These delegates will be invoked to register module-specific build
+// statements which may be unique to the module type. For example, module.compiler.compile() should
+// be defined so as to register build statements which are responsible for compiling the module.
+//
+// Another example: to construct a cc_binary module, one can create a `cc.binaryDecorator` struct
+// which implements the `linker` and `installer` interfaces, and points the `linker` and `installer`
+// members of the cc.Module to this decorator. Thus, a cc_binary module has custom linker and
+// installer logic.
 type Module struct {
 	android.ModuleBase
 	android.DefaultableModuleBase
@@ -643,18 +692,23 @@
 	// Allowable SdkMemberTypes of this module type.
 	sdkMemberTypes []android.SdkMemberType
 
-	// delegates, initialize before calling Init
-	features  []feature
+	// decorator delegates, initialize before calling Init
+	// these may contain module-specific implementations, and effectively allow for custom
+	// type-specific logic. These members may reference different objects or the same object.
+	// Functions of these decorators will be invoked to initialize and register type-specific
+	// build statements.
 	compiler  compiler
 	linker    linker
 	installer installer
-	stl       *stl
-	sanitize  *sanitize
-	coverage  *coverage
-	sabi      *sabi
-	vndkdep   *vndkdep
-	lto       *lto
-	pgo       *pgo
+
+	features []feature
+	stl      *stl
+	sanitize *sanitize
+	coverage *coverage
+	sabi     *sabi
+	vndkdep  *vndkdep
+	lto      *lto
+	pgo      *pgo
 
 	library libraryInterface
 
diff --git a/cc/cc_test.go b/cc/cc_test.go
index 7c98585..af9b943 100644
--- a/cc/cc_test.go
+++ b/cc/cc_test.go
@@ -2913,114 +2913,6 @@
 	}
 }
 
-var (
-	str11 = "01234567891"
-	str10 = str11[:10]
-	str9  = str11[:9]
-	str5  = str11[:5]
-	str4  = str11[:4]
-)
-
-var splitListForSizeTestCases = []struct {
-	in   []string
-	out  [][]string
-	size int
-}{
-	{
-		in:   []string{str10},
-		out:  [][]string{{str10}},
-		size: 10,
-	},
-	{
-		in:   []string{str9},
-		out:  [][]string{{str9}},
-		size: 10,
-	},
-	{
-		in:   []string{str5},
-		out:  [][]string{{str5}},
-		size: 10,
-	},
-	{
-		in:   []string{str11},
-		out:  nil,
-		size: 10,
-	},
-	{
-		in:   []string{str10, str10},
-		out:  [][]string{{str10}, {str10}},
-		size: 10,
-	},
-	{
-		in:   []string{str9, str10},
-		out:  [][]string{{str9}, {str10}},
-		size: 10,
-	},
-	{
-		in:   []string{str10, str9},
-		out:  [][]string{{str10}, {str9}},
-		size: 10,
-	},
-	{
-		in:   []string{str5, str4},
-		out:  [][]string{{str5, str4}},
-		size: 10,
-	},
-	{
-		in:   []string{str5, str4, str5},
-		out:  [][]string{{str5, str4}, {str5}},
-		size: 10,
-	},
-	{
-		in:   []string{str5, str4, str5, str4},
-		out:  [][]string{{str5, str4}, {str5, str4}},
-		size: 10,
-	},
-	{
-		in:   []string{str5, str4, str5, str5},
-		out:  [][]string{{str5, str4}, {str5}, {str5}},
-		size: 10,
-	},
-	{
-		in:   []string{str5, str5, str5, str4},
-		out:  [][]string{{str5}, {str5}, {str5, str4}},
-		size: 10,
-	},
-	{
-		in:   []string{str9, str11},
-		out:  nil,
-		size: 10,
-	},
-	{
-		in:   []string{str11, str9},
-		out:  nil,
-		size: 10,
-	},
-}
-
-func TestSplitListForSize(t *testing.T) {
-	for _, testCase := range splitListForSizeTestCases {
-		out, _ := splitListForSize(android.PathsForTesting(testCase.in...), testCase.size)
-
-		var outStrings [][]string
-
-		if len(out) > 0 {
-			outStrings = make([][]string, len(out))
-			for i, o := range out {
-				outStrings[i] = o.Strings()
-			}
-		}
-
-		if !reflect.DeepEqual(outStrings, testCase.out) {
-			t.Errorf("incorrect output:")
-			t.Errorf("     input: %#v", testCase.in)
-			t.Errorf("      size: %d", testCase.size)
-			t.Errorf("  expected: %#v", testCase.out)
-			t.Errorf("       got: %#v", outStrings)
-		}
-	}
-}
-
 var staticLinkDepOrderTestCases = []struct {
 	// This is a string representation of a map[moduleName][]moduleDependency .
 	// It models the dependencies declared in an Android.bp file.
diff --git a/cc/cflag_artifacts.go b/cc/cflag_artifacts.go
index 855ff25..be46fc0 100644
--- a/cc/cflag_artifacts.go
+++ b/cc/cflag_artifacts.go
@@ -68,7 +68,7 @@
 
 	cleanedName := strings.Replace(flag, "=", "_", -1)
 	filename, filepath := s.incrementFile(ctx, cleanedName, part)
-	rule := android.NewRuleBuilder()
+	rule := android.NewRuleBuilder(pctx, ctx)
 	rule.Command().Textf("rm -f %s", filepath.String())
 
 	if using {
@@ -84,7 +84,7 @@
 	length := len(modules)
 
 	if length == 0 {
-		rule.Build(pctx, ctx, filename, "gen "+filename)
+		rule.Build(filename, "gen "+filename)
 		part++
 	}
 
@@ -98,11 +98,11 @@
 				strings.Join(proptools.ShellEscapeList(shard), " ")).
 			FlagWithOutput(">> ", filepath).
 			Text("; done")
-		rule.Build(pctx, ctx, filename, "gen "+filename)
+		rule.Build(filename, "gen "+filename)
 
 		if index+1 != len(moduleShards) {
 			filename, filepath = s.incrementFile(ctx, cleanedName, part+index+1)
-			rule = android.NewRuleBuilder()
+			rule = android.NewRuleBuilder(pctx, ctx)
 			rule.Command().Textf("rm -f %s", filepath.String())
 		}
 	}
@@ -121,14 +121,14 @@
 	for _, flag := range TrackedCFlags {
 		// Generate build rule to combine related intermediary files into a
 		// C Flag artifact
-		rule := android.NewRuleBuilder()
+		rule := android.NewRuleBuilder(pctx, ctx)
 		filename := s.genFlagFilename(flag)
 		outputpath := android.PathForOutput(ctx, "cflags", filename)
 		rule.Command().
 			Text("cat").
 			Inputs(s.interOutputs[flag].Paths()).
 			FlagWithOutput("> ", outputpath)
-		rule.Build(pctx, ctx, filename, "gen "+filename)
+		rule.Build(filename, "gen "+filename)
 		s.outputs = append(s.outputs, outputpath)
 	}
 }
diff --git a/cc/compiler.go b/cc/compiler.go
index 04ed80d..b78bb6c 100644
--- a/cc/compiler.go
+++ b/cc/compiler.go
@@ -366,7 +366,7 @@
 		}
 		if ctx.Device() {
 			flags.Global.CommonFlags = append(flags.Global.CommonFlags,
-				fmt.Sprintf("-D__ANDROID_SDK_VERSION__=%d",
+				fmt.Sprintf("-D__ANDROID_APEX_MIN_SDK_VERSION__=%d",
 					ctx.apexSdkVersion().FinalOrFutureInt()))
 		}
 	}
@@ -649,7 +649,7 @@
 func compileObjs(ctx android.ModuleContext, flags builderFlags,
 	subdir string, srcFiles, pathDeps android.Paths, cFlagsDeps android.Paths) Objects {
 
-	return TransformSourceToObj(ctx, subdir, srcFiles, flags, pathDeps, cFlagsDeps)
+	return transformSourceToObj(ctx, subdir, srcFiles, flags, pathDeps, cFlagsDeps)
 }
 
 var thirdPartyDirPrefixExceptions = []*regexp.Regexp{
diff --git a/cc/fuzz.go b/cc/fuzz.go
index dddfe94..6b17c48 100644
--- a/cc/fuzz.go
+++ b/cc/fuzz.go
@@ -246,25 +246,25 @@
 	fuzz.binaryDecorator.baseInstaller.install(ctx, file)
 
 	fuzz.corpus = android.PathsForModuleSrc(ctx, fuzz.Properties.Corpus)
-	builder := android.NewRuleBuilder()
+	builder := android.NewRuleBuilder(pctx, ctx)
 	intermediateDir := android.PathForModuleOut(ctx, "corpus")
 	for _, entry := range fuzz.corpus {
 		builder.Command().Text("cp").
 			Input(entry).
 			Output(intermediateDir.Join(ctx, entry.Base()))
 	}
-	builder.Build(pctx, ctx, "copy_corpus", "copy corpus")
+	builder.Build("copy_corpus", "copy corpus")
 	fuzz.corpusIntermediateDir = intermediateDir
 
 	fuzz.data = android.PathsForModuleSrc(ctx, fuzz.Properties.Data)
-	builder = android.NewRuleBuilder()
+	builder = android.NewRuleBuilder(pctx, ctx)
 	intermediateDir = android.PathForModuleOut(ctx, "data")
 	for _, entry := range fuzz.data {
 		builder.Command().Text("cp").
 			Input(entry).
 			Output(intermediateDir.Join(ctx, entry.Rel()))
 	}
-	builder.Build(pctx, ctx, "copy_data", "copy data")
+	builder.Build("copy_data", "copy data")
 	fuzz.dataIntermediateDir = intermediateDir
 
 	if fuzz.Properties.Dictionary != nil {
@@ -419,12 +419,12 @@
 		sharedLibraries := collectAllSharedDependencies(ctx, module)
 
 		var files []fileToZip
-		builder := android.NewRuleBuilder()
+		builder := android.NewRuleBuilder(pctx, ctx)
 
 		// Package the corpora into a zipfile.
 		if fuzzModule.corpus != nil {
 			corpusZip := archDir.Join(ctx, module.Name()+"_seed_corpus.zip")
-			command := builder.Command().BuiltTool(ctx, "soong_zip").
+			command := builder.Command().BuiltTool("soong_zip").
 				Flag("-j").
 				FlagWithOutput("-o ", corpusZip)
 			command.FlagWithRspFileInputList("-r ", fuzzModule.corpus)
@@ -434,7 +434,7 @@
 		// Package the data into a zipfile.
 		if fuzzModule.data != nil {
 			dataZip := archDir.Join(ctx, module.Name()+"_data.zip")
-			command := builder.Command().BuiltTool(ctx, "soong_zip").
+			command := builder.Command().BuiltTool("soong_zip").
 				FlagWithOutput("-o ", dataZip)
 			for _, f := range fuzzModule.data {
 				intermediateDir := strings.TrimSuffix(f.String(), f.Rel())
@@ -492,7 +492,7 @@
 		}
 
 		fuzzZip := archDir.Join(ctx, module.Name()+".zip")
-		command := builder.Command().BuiltTool(ctx, "soong_zip").
+		command := builder.Command().BuiltTool("soong_zip").
 			Flag("-j").
 			FlagWithOutput("-o ", fuzzZip)
 		for _, file := range files {
@@ -504,7 +504,7 @@
 			command.FlagWithInput("-f ", file.SourceFilePath)
 		}
 
-		builder.Build(pctx, ctx, "create-"+fuzzZip.String(),
+		builder.Build("create-"+fuzzZip.String(),
 			"Package "+module.Name()+" for "+archString+"-"+hostOrTargetString)
 
 		// Don't add modules to 'make haiku' that are set to not be exported to the
@@ -531,11 +531,11 @@
 		filesToZip := archDirs[archOs]
 		arch := archOs.arch
 		hostOrTarget := archOs.hostOrTarget
-		builder := android.NewRuleBuilder()
+		builder := android.NewRuleBuilder(pctx, ctx)
 		outputFile := android.PathForOutput(ctx, "fuzz-"+hostOrTarget+"-"+arch+".zip")
 		s.packages = append(s.packages, outputFile)
 
-		command := builder.Command().BuiltTool(ctx, "soong_zip").
+		command := builder.Command().BuiltTool("soong_zip").
 			Flag("-j").
 			FlagWithOutput("-o ", outputFile).
 			Flag("-L 0") // No need to try and re-compress the zipfiles.
@@ -549,7 +549,7 @@
 			command.FlagWithInput("-f ", fileToZip.SourceFilePath)
 		}
 
-		builder.Build(pctx, ctx, "create-fuzz-package-"+arch+"-"+hostOrTarget,
+		builder.Build("create-fuzz-package-"+arch+"-"+hostOrTarget,
 			"Create fuzz target packages for "+arch+"-"+hostOrTarget)
 	}
 }
diff --git a/cc/gen.go b/cc/gen.go
index 5895b31..75b9e49 100644
--- a/cc/gen.go
+++ b/cc/gen.go
@@ -75,10 +75,9 @@
 	cmd := rule.Command()
 
 	// Fix up #line markers to not use the sbox temporary directory
-	// android.SboxPathForOutput(outDir, outDir) returns the sbox placeholder for the out
+	// android.sboxPathForOutput(outDir, outDir) returns the sbox placeholder for the out
 	// directory itself, without any filename appended.
-	// TODO(ccross): make this cmd.PathForOutput(outDir) instead.
-	sboxOutDir := android.SboxPathForOutput(outDir, outDir)
+	sboxOutDir := cmd.PathForOutput(outDir)
 	sedCmd := "sed -i.bak 's#" + sboxOutDir + "#" + outDir.String() + "#'"
 	rule.Command().Text(sedCmd).Input(outFile)
 	rule.Command().Text(sedCmd).Input(headerFile)
@@ -137,7 +136,7 @@
 	}
 
 	cmd := rule.Command()
-	cmd.BuiltTool(ctx, "aidl-cpp").
+	cmd.BuiltTool("aidl-cpp").
 		FlagWithDepFile("-d", depFile).
 		Flag("--ninja").
 		Flag(aidlFlags).
@@ -232,7 +231,7 @@
 	var yaccRule_ *android.RuleBuilder
 	yaccRule := func() *android.RuleBuilder {
 		if yaccRule_ == nil {
-			yaccRule_ = android.NewRuleBuilder().Sbox(android.PathForModuleGen(ctx, "yacc"),
+			yaccRule_ = android.NewRuleBuilder(pctx, ctx).Sbox(android.PathForModuleGen(ctx, "yacc"),
 				android.PathForModuleGen(ctx, "yacc.sbox.textproto"))
 		}
 		return yaccRule_
@@ -262,7 +261,7 @@
 			deps = append(deps, headerFile)
 		case ".aidl":
 			if aidlRule == nil {
-				aidlRule = android.NewRuleBuilder().Sbox(android.PathForModuleGen(ctx, "aidl"),
+				aidlRule = android.NewRuleBuilder(pctx, ctx).Sbox(android.PathForModuleGen(ctx, "aidl"),
 					android.PathForModuleGen(ctx, "aidl.sbox.textproto"))
 			}
 			cppFile := android.GenPathWithExt(ctx, "aidl", srcFile, "cpp")
@@ -285,11 +284,11 @@
 	}
 
 	if aidlRule != nil {
-		aidlRule.Build(pctx, ctx, "aidl", "gen aidl")
+		aidlRule.Build("aidl", "gen aidl")
 	}
 
 	if yaccRule_ != nil {
-		yaccRule_.Build(pctx, ctx, "yacc", "gen yacc")
+		yaccRule_.Build("yacc", "gen yacc")
 	}
 
 	if len(rsFiles) > 0 {
diff --git a/cc/library.go b/cc/library.go
index 7ae75f2..c626b03 100644
--- a/cc/library.go
+++ b/cc/library.go
@@ -897,9 +897,9 @@
 		}
 	}
 
-	TransformObjToStaticLib(ctx, library.objects.objFiles, deps.WholeStaticLibsFromPrebuilts, builderFlags, outputFile, objs.tidyFiles)
+	transformObjToStaticLib(ctx, library.objects.objFiles, deps.WholeStaticLibsFromPrebuilts, builderFlags, outputFile, objs.tidyFiles)
 
-	library.coverageOutputFile = TransformCoverageFilesToZip(ctx, library.objects, ctx.ModuleName())
+	library.coverageOutputFile = transformCoverageFilesToZip(ctx, library.objects, ctx.ModuleName())
 
 	ctx.CheckbuildFile(outputFile)
 
@@ -974,7 +974,7 @@
 	// depending on a table of contents file instead of the library itself.
 	tocFile := outputFile.ReplaceExtension(ctx, flags.Toolchain.ShlibSuffix()[1:]+".toc")
 	library.tocFile = android.OptionalPathForPath(tocFile)
-	TransformSharedObjectToToc(ctx, outputFile, tocFile, builderFlags)
+	transformSharedObjectToToc(ctx, outputFile, tocFile, builderFlags)
 
 	stripFlags := flagsToStripFlags(flags)
 	if library.stripper.NeedsStrip(ctx) {
@@ -1019,7 +1019,7 @@
 
 	if Bool(library.Properties.Sort_bss_symbols_by_size) {
 		unsortedOutputFile := android.PathForModuleOut(ctx, "unsorted", fileName)
-		TransformObjToDynamicBinary(ctx, objs.objFiles, sharedLibs,
+		transformObjToDynamicBinary(ctx, objs.objFiles, sharedLibs,
 			deps.StaticLibs, deps.LateStaticLibs, deps.WholeStaticLibs,
 			linkerDeps, deps.CrtBegin, deps.CrtEnd, false, builderFlags, unsortedOutputFile, implicitOutputs)
 
@@ -1029,7 +1029,7 @@
 		linkerDeps = append(linkerDeps, symbolOrderingFile)
 	}
 
-	TransformObjToDynamicBinary(ctx, objs.objFiles, sharedLibs,
+	transformObjToDynamicBinary(ctx, objs.objFiles, sharedLibs,
 		deps.StaticLibs, deps.LateStaticLibs, deps.WholeStaticLibs,
 		linkerDeps, deps.CrtBegin, deps.CrtEnd, false, builderFlags, outputFile, implicitOutputs)
 
@@ -1039,7 +1039,7 @@
 	objs.sAbiDumpFiles = append(objs.sAbiDumpFiles, deps.StaticLibObjs.sAbiDumpFiles...)
 	objs.sAbiDumpFiles = append(objs.sAbiDumpFiles, deps.WholeStaticLibObjs.sAbiDumpFiles...)
 
-	library.coverageOutputFile = TransformCoverageFilesToZip(ctx, objs, library.getLibName(ctx))
+	library.coverageOutputFile = transformCoverageFilesToZip(ctx, objs, library.getLibName(ctx))
 	library.linkSAbiDumpFiles(ctx, objs, fileName, unstrippedOutputFile)
 
 	var staticAnalogue *StaticLibraryInfo
@@ -1115,7 +1115,7 @@
 		return refAbiDumpTextFile.Path()
 	}
 	if refAbiDumpGzipFile.Valid() {
-		return UnzipRefDump(ctx, refAbiDumpGzipFile.Path(), fileName)
+		return unzipRefDump(ctx, refAbiDumpGzipFile.Path(), fileName)
 	}
 	return nil
 }
@@ -1141,7 +1141,7 @@
 			SourceAbiFlags = append(SourceAbiFlags, "-I"+reexportedInclude)
 		}
 		exportedHeaderFlags := strings.Join(SourceAbiFlags, " ")
-		library.sAbiOutputFile = TransformDumpToLinkedDump(ctx, objs.sAbiDumpFiles, soFile, fileName, exportedHeaderFlags,
+		library.sAbiOutputFile = transformDumpToLinkedDump(ctx, objs.sAbiDumpFiles, soFile, fileName, exportedHeaderFlags,
 			android.OptionalPathForModuleSrc(ctx, library.symbolFileForAbiCheck(ctx)),
 			library.Properties.Header_abi_checker.Exclude_symbol_versions,
 			library.Properties.Header_abi_checker.Exclude_symbol_tags)
@@ -1150,7 +1150,7 @@
 
 		refAbiDumpFile := getRefAbiDumpFile(ctx, vndkVersion, fileName)
 		if refAbiDumpFile != nil {
-			library.sAbiDiff = SourceAbiDiff(ctx, library.sAbiOutputFile.Path(),
+			library.sAbiDiff = sourceAbiDiff(ctx, library.sAbiOutputFile.Path(),
 				refAbiDumpFile, fileName, exportedHeaderFlags,
 				Bool(library.Properties.Header_abi_checker.Check_all_apis),
 				ctx.isLlndk(ctx.Config()), ctx.isNdk(ctx.Config()), ctx.isVndkExt())
@@ -1754,13 +1754,13 @@
 		hashedOutputfile := outputFile
 		outputFile = android.PathForModuleOut(ctx, "unhashed", fileName)
 
-		rule := android.NewRuleBuilder()
+		rule := android.NewRuleBuilder(pctx, ctx)
 		rule.Command().
-			BuiltTool(ctx, "bssl_inject_hash").
+			BuiltTool("bssl_inject_hash").
 			Flag("-sha256").
 			FlagWithInput("-in-object ", outputFile).
 			FlagWithOutput("-o ", hashedOutputfile)
-		rule.Build(pctx, ctx, "injectCryptoHash", "inject crypto hash")
+		rule.Build("injectCryptoHash", "inject crypto hash")
 	}
 
 	return outputFile
diff --git a/cc/object.go b/cc/object.go
index ab2672b..3ce7676 100644
--- a/cc/object.go
+++ b/cc/object.go
@@ -124,7 +124,7 @@
 
 		if String(object.Properties.Prefix_symbols) != "" {
 			output := android.PathForModuleOut(ctx, ctx.ModuleName()+objectExtension)
-			TransformBinaryPrefixSymbols(ctx, String(object.Properties.Prefix_symbols), outputFile,
+			transformBinaryPrefixSymbols(ctx, String(object.Properties.Prefix_symbols), outputFile,
 				builderFlags, output)
 			outputFile = output
 		}
@@ -134,12 +134,12 @@
 
 		if String(object.Properties.Prefix_symbols) != "" {
 			input := android.PathForModuleOut(ctx, "unprefixed", ctx.ModuleName()+objectExtension)
-			TransformBinaryPrefixSymbols(ctx, String(object.Properties.Prefix_symbols), input,
+			transformBinaryPrefixSymbols(ctx, String(object.Properties.Prefix_symbols), input,
 				builderFlags, output)
 			output = input
 		}
 
-		TransformObjsToObj(ctx, objs.objFiles, builderFlags, output, flags.LdFlagsDeps)
+		transformObjsToObj(ctx, objs.objFiles, builderFlags, output, flags.LdFlagsDeps)
 	}
 
 	ctx.CheckbuildFile(outputFile)
diff --git a/cc/prebuilt.go b/cc/prebuilt.go
index 8873883..37df4ba 100644
--- a/cc/prebuilt.go
+++ b/cc/prebuilt.go
@@ -146,7 +146,7 @@
 			// depending on a table of contents file instead of the library itself.
 			tocFile := android.PathForModuleOut(ctx, libName+".toc")
 			p.tocFile = android.OptionalPathForPath(tocFile)
-			TransformSharedObjectToToc(ctx, outputFile, tocFile, builderFlags)
+			transformSharedObjectToToc(ctx, outputFile, tocFile, builderFlags)
 
 			if ctx.Windows() && p.properties.Windows_import_lib != nil {
 				// Consumers of this library actually links to the import library in build
diff --git a/cc/proto.go b/cc/proto.go
index 9c102a2..4466144 100644
--- a/cc/proto.go
+++ b/cc/proto.go
@@ -50,11 +50,11 @@
 	depFile := ccFile.ReplaceExtension(ctx, "d")
 	outputs := android.WritablePaths{ccFile, headerFile}
 
-	rule := android.NewRuleBuilder()
+	rule := android.NewRuleBuilder(pctx, ctx)
 
-	android.ProtoRule(ctx, rule, protoFile, flags.proto, protoDeps, outDir, depFile, outputs)
+	android.ProtoRule(rule, protoFile, flags.proto, protoDeps, outDir, depFile, outputs)
 
-	rule.Build(pctx, ctx, "protoc_"+protoFile.Rel(), "protoc "+protoFile.Rel())
+	rule.Build("protoc_"+protoFile.Rel(), "protoc "+protoFile.Rel())
 
 	return ccFile, headerFile
 }
diff --git a/cc/sanitize.go b/cc/sanitize.go
index dbc52a5..22ee25f 100644
--- a/cc/sanitize.go
+++ b/cc/sanitize.go
@@ -169,14 +169,14 @@
 		Cfi              *bool    `android:"arch_variant"`
 		Integer_overflow *bool    `android:"arch_variant"`
 		Misc_undefined   []string `android:"arch_variant"`
-		No_recover       []string
-	}
+		No_recover       []string `android:"arch_variant"`
+	} `android:"arch_variant"`
 
 	// Sanitizers to run with flag configuration specified
 	Config struct {
 		// Enables CFI support flags for assembly-heavy libraries
 		Cfi_assembly_support *bool `android:"arch_variant"`
-	}
+	} `android:"arch_variant"`
 
 	// value to pass to -fsanitize-recover=
 	Recover []string
diff --git a/cc/strip.go b/cc/strip.go
index e9aec91..1f10a74 100644
--- a/cc/strip.go
+++ b/cc/strip.go
@@ -54,7 +54,7 @@
 func (stripper *Stripper) strip(actx android.ModuleContext, in android.Path, out android.ModuleOutPath,
 	flags StripFlags, isStaticLib bool) {
 	if actx.Darwin() {
-		TransformDarwinStrip(actx, in, out)
+		transformDarwinStrip(actx, in, out)
 	} else {
 		if Bool(stripper.StripProperties.Strip.Keep_symbols) {
 			flags.StripKeepSymbols = true
@@ -68,7 +68,7 @@
 		if actx.Config().Debuggable() && !flags.StripKeepMiniDebugInfo && !isStaticLib {
 			flags.StripAddGnuDebuglink = true
 		}
-		TransformStrip(actx, in, out, flags)
+		transformStrip(actx, in, out, flags)
 	}
 }
 
diff --git a/cc/toolchain_library.go b/cc/toolchain_library.go
index 0c934ad..bda73ea 100644
--- a/cc/toolchain_library.go
+++ b/cc/toolchain_library.go
@@ -90,7 +90,7 @@
 	if library.Properties.Repack_objects_to_keep != nil {
 		fileName := ctx.ModuleName() + staticLibraryExtension
 		repackedPath := android.PathForModuleOut(ctx, fileName)
-		TransformArchiveRepack(ctx, outputFile, repackedPath, library.Properties.Repack_objects_to_keep)
+		transformArchiveRepack(ctx, outputFile, repackedPath, library.Properties.Repack_objects_to_keep)
 		outputFile = repackedPath
 	}
 
diff --git a/cc/vendor_snapshot.go b/cc/vendor_snapshot.go
index 6563f6e..3ef0b62 100644
--- a/cc/vendor_snapshot.go
+++ b/cc/vendor_snapshot.go
@@ -339,7 +339,7 @@
 		// depending on a table of contents file instead of the library itself.
 		tocFile := android.PathForModuleOut(ctx, libName+".toc")
 		p.tocFile = android.OptionalPathForPath(tocFile)
-		TransformSharedObjectToToc(ctx, in, tocFile, builderFlags)
+		transformSharedObjectToToc(ctx, in, tocFile, builderFlags)
 
 		ctx.SetProvider(SharedLibraryInfoProvider, SharedLibraryInfo{
 			SharedLibrary:           in,
@@ -1124,7 +1124,7 @@
 		ctx,
 		snapshotDir,
 		c.name+"-"+ctx.Config().DeviceName()+".zip")
-	zipRule := android.NewRuleBuilder()
+	zipRule := android.NewRuleBuilder(pctx, ctx)
 
 	// filenames in rspfile from FlagWithRspFileInputList might be single-quoted. Remove it with tr
 	snapshotOutputList := android.PathForOutput(
@@ -1140,12 +1140,12 @@
 	zipRule.Temporary(snapshotOutputList)
 
 	zipRule.Command().
-		BuiltTool(ctx, "soong_zip").
+		BuiltTool("soong_zip").
 		FlagWithOutput("-o ", zipPath).
 		FlagWithArg("-C ", android.PathForOutput(ctx, snapshotDir).String()).
 		FlagWithInput("-l ", snapshotOutputList)
 
-	zipRule.Build(pctx, ctx, zipPath.String(), c.name+" snapshot "+zipPath.String())
+	zipRule.Build(zipPath.String(), c.name+" snapshot "+zipPath.String())
 	zipRule.DeleteTemporaryFiles()
 	c.snapshotZipFile = android.OptionalPathForPath(zipPath)
 }
diff --git a/cc/vndk.go b/cc/vndk.go
index 4a005f3..d57cdf7 100644
--- a/cc/vndk.go
+++ b/cc/vndk.go
@@ -727,7 +727,7 @@
 		var txtBuilder strings.Builder
 		for idx, k := range android.SortedStringKeys(m) {
 			if idx > 0 {
-				txtBuilder.WriteString("\\n")
+				txtBuilder.WriteString("\n")
 			}
 			txtBuilder.WriteString(k)
 			txtBuilder.WriteString(" ")
@@ -762,7 +762,7 @@
 	})
 
 	zipPath := android.PathForOutput(ctx, snapshotDir, "android-vndk-"+ctx.DeviceConfig().DeviceArch()+".zip")
-	zipRule := android.NewRuleBuilder()
+	zipRule := android.NewRuleBuilder(pctx, ctx)
 
 	// filenames in rspfile from FlagWithRspFileInputList might be single-quoted. Remove it with xargs
 	snapshotOutputList := android.PathForOutput(ctx, snapshotDir, "android-vndk-"+ctx.DeviceConfig().DeviceArch()+"_list")
@@ -775,12 +775,12 @@
 	zipRule.Temporary(snapshotOutputList)
 
 	zipRule.Command().
-		BuiltTool(ctx, "soong_zip").
+		BuiltTool("soong_zip").
 		FlagWithOutput("-o ", zipPath).
 		FlagWithArg("-C ", android.PathForOutput(ctx, snapshotDir).String()).
 		FlagWithInput("-l ", snapshotOutputList)
 
-	zipRule.Build(pctx, ctx, zipPath.String(), "vndk snapshot "+zipPath.String())
+	zipRule.Build(zipPath.String(), "vndk snapshot "+zipPath.String())
 	zipRule.DeleteTemporaryFiles()
 	c.vndkSnapshotZipFile = android.OptionalPathForPath(zipPath)
 }
diff --git a/cc/vndk_prebuilt.go b/cc/vndk_prebuilt.go
index c0320eb..e6e2ad8 100644
--- a/cc/vndk_prebuilt.go
+++ b/cc/vndk_prebuilt.go
@@ -154,7 +154,7 @@
 		// depending on a table of contents file instead of the library itself.
 		tocFile := android.PathForModuleOut(ctx, libName+".toc")
 		p.tocFile = android.OptionalPathForPath(tocFile)
-		TransformSharedObjectToToc(ctx, in, tocFile, builderFlags)
+		transformSharedObjectToToc(ctx, in, tocFile, builderFlags)
 
 		p.androidMkSuffix = p.NameSuffix()
 
diff --git a/cmd/soong_build/main.go b/cmd/soong_build/main.go
index b88803a..d758de2 100644
--- a/cmd/soong_build/main.go
+++ b/cmd/soong_build/main.go
@@ -79,7 +79,7 @@
 	srcDir := filepath.Dir(flag.Arg(0))
 	var ctx *android.Context
 	configuration := newConfig(srcDir)
-	extraNinjaDeps := []string{configuration.ConfigFileName, configuration.ProductVariablesFileName}
+	extraNinjaDeps := []string{configuration.ProductVariablesFileName}
 
 	// Read the SOONG_DELVE again through configuration so that there is a dependency on the environment variable
 	// and soong_build will rerun when it is set for the first time.
diff --git a/dexpreopt/dexpreopt.go b/dexpreopt/dexpreopt.go
index 65380fe..b0a684e 100644
--- a/dexpreopt/dexpreopt.go
+++ b/dexpreopt/dexpreopt.go
@@ -51,7 +51,7 @@
 
 // GenerateDexpreoptRule generates a set of commands that will preopt a module based on a GlobalConfig and a
 // ModuleConfig.  The produced files and their install locations will be available through rule.Installs().
-func GenerateDexpreoptRule(ctx android.PathContext, globalSoong *GlobalSoongConfig,
+func GenerateDexpreoptRule(ctx android.BuilderContext, globalSoong *GlobalSoongConfig,
 	global *GlobalConfig, module *ModuleConfig) (rule *android.RuleBuilder, err error) {
 
 	defer func() {
@@ -67,7 +67,7 @@
 		}
 	}()
 
-	rule = android.NewRuleBuilder()
+	rule = android.NewRuleBuilder(pctx, ctx)
 
 	generateProfile := module.ProfileClassListing.Valid() && !global.DisableGenerateProfile
 	generateBootProfile := module.ProfileBootListing.Valid() && !global.DisableGenerateProfile
diff --git a/dexpreopt/dexpreopt_gen/dexpreopt_gen.go b/dexpreopt/dexpreopt_gen/dexpreopt_gen.go
index e89f045..32c4f84 100644
--- a/dexpreopt/dexpreopt_gen/dexpreopt_gen.go
+++ b/dexpreopt/dexpreopt_gen/dexpreopt_gen.go
@@ -27,6 +27,7 @@
 	"android/soong/android"
 	"android/soong/dexpreopt"
 
+	"github.com/google/blueprint"
 	"github.com/google/blueprint/pathtools"
 )
 
@@ -38,12 +39,16 @@
 	outDir                = flag.String("out_dir", "", "path to output directory")
 )
 
-type pathContext struct {
+type builderContext struct {
 	config android.Config
 }
 
-func (x *pathContext) Config() android.Config     { return x.config }
-func (x *pathContext) AddNinjaFileDeps(...string) {}
+func (x *builderContext) Config() android.Config                            { return x.config }
+func (x *builderContext) AddNinjaFileDeps(...string)                        {}
+func (x *builderContext) Build(android.PackageContext, android.BuildParams) {}
+func (x *builderContext) Rule(android.PackageContext, string, blueprint.RuleParams, ...string) blueprint.Rule {
+	return nil
+}
 
 func main() {
 	flag.Parse()
@@ -76,7 +81,7 @@
 		usage("--module configuration file is required")
 	}
 
-	ctx := &pathContext{android.NullConfig(*outDir)}
+	ctx := &builderContext{android.NullConfig(*outDir)}
 
 	globalSoongConfigData, err := ioutil.ReadFile(*globalSoongConfigPath)
 	if err != nil {
@@ -133,7 +138,7 @@
 	writeScripts(ctx, globalSoongConfig, globalConfig, moduleConfig, *dexpreoptScriptPath)
 }
 
-func writeScripts(ctx android.PathContext, globalSoong *dexpreopt.GlobalSoongConfig,
+func writeScripts(ctx android.BuilderContext, globalSoong *dexpreopt.GlobalSoongConfig,
 	global *dexpreopt.GlobalConfig, module *dexpreopt.ModuleConfig, dexpreoptScriptPath string) {
 	dexpreoptRule, err := dexpreopt.GenerateDexpreoptRule(ctx, globalSoong, global, module)
 	if err != nil {
diff --git a/dexpreopt/dexpreopt_test.go b/dexpreopt/dexpreopt_test.go
index feabd70..59278fd 100644
--- a/dexpreopt/dexpreopt_test.go
+++ b/dexpreopt/dexpreopt_test.go
@@ -60,7 +60,7 @@
 
 func TestDexPreopt(t *testing.T) {
 	config := android.TestConfig("out", nil, "", nil)
-	ctx := android.PathContextForTesting(config)
+	ctx := android.BuilderContextForTesting(config)
 	globalSoong := GlobalSoongConfigForTests(config)
 	global := GlobalConfigForTests(ctx)
 	module := testSystemModuleConfig(ctx, "test")
@@ -82,7 +82,7 @@
 
 func TestDexPreoptSystemOther(t *testing.T) {
 	config := android.TestConfig("out", nil, "", nil)
-	ctx := android.PathContextForTesting(config)
+	ctx := android.BuilderContextForTesting(config)
 	globalSoong := GlobalSoongConfigForTests(config)
 	global := GlobalConfigForTests(ctx)
 	systemModule := testSystemModuleConfig(ctx, "Stest")
@@ -142,7 +142,7 @@
 
 func TestDexPreoptProfile(t *testing.T) {
 	config := android.TestConfig("out", nil, "", nil)
-	ctx := android.PathContextForTesting(config)
+	ctx := android.BuilderContextForTesting(config)
 	globalSoong := GlobalSoongConfigForTests(config)
 	global := GlobalConfigForTests(ctx)
 	module := testSystemModuleConfig(ctx, "test")
diff --git a/filesystem/filesystem.go b/filesystem/filesystem.go
index ac33b76..c6181bc 100644
--- a/filesystem/filesystem.go
+++ b/filesystem/filesystem.go
@@ -63,9 +63,9 @@
 	f.CopyDepsToZip(ctx, zipFile)
 
 	rootDir := android.PathForModuleOut(ctx, "root").OutputPath
-	builder := android.NewRuleBuilder()
+	builder := android.NewRuleBuilder(pctx, ctx)
 	builder.Command().
-		BuiltTool(ctx, "zipsync").
+		BuiltTool("zipsync").
 		FlagWithArg("-d ", rootDir.String()). // zipsync wipes this. No need to clear.
 		Input(zipFile)
 
@@ -81,14 +81,14 @@
 		Implicit(mkuserimg)
 
 	f.output = android.PathForModuleOut(ctx, "filesystem.img").OutputPath
-	builder.Command().BuiltTool(ctx, "build_image").
+	builder.Command().BuiltTool("build_image").
 		Text(rootDir.String()). // input directory
 		Input(propFile).
 		Output(f.output).
 		Text(rootDir.String()) // directory where to find fs_config_files|dirs
 
 	// rootDir is not deleted. Might be useful for quick inspection.
-	builder.Build(pctx, ctx, "build_filesystem_image", fmt.Sprintf("Creating filesystem %s", f.BaseModuleName()))
+	builder.Build("build_filesystem_image", fmt.Sprintf("Creating filesystem %s", f.BaseModuleName()))
 
 	f.installDir = android.PathForModuleInstall(ctx, "etc")
 	ctx.InstallFile(f.installDir, f.installFileName(), f.output)
diff --git a/genrule/genrule.go b/genrule/genrule.go
index e5ee3fc..93938c9 100644
--- a/genrule/genrule.go
+++ b/genrule/genrule.go
@@ -342,8 +342,27 @@
 			return
 		}
 
+		// Pick a unique path outside the task.genDir for the sbox manifest textproto,
+		// a unique rule name, and the user-visible description.
+		manifestName := "genrule.sbox.textproto"
+		desc := "generate"
+		name := "generator"
+		if task.shards > 0 {
+			manifestName = "genrule_" + strconv.Itoa(task.shard) + ".sbox.textproto"
+			desc += " " + strconv.Itoa(task.shard)
+			name += strconv.Itoa(task.shard)
+		} else if len(task.out) == 1 {
+			desc += " " + task.out[0].Base()
+		}
+
+		manifestPath := android.PathForModuleOut(ctx, manifestName)
+
+		// Use a RuleBuilder to create a rule that runs the command inside an sbox sandbox.
+		rule := android.NewRuleBuilder(pctx, ctx).Sbox(task.genDir, manifestPath)
+		cmd := rule.Command()
+
 		for _, out := range task.out {
-			addLocationLabel(out.Rel(), []string{android.SboxPathForOutput(out, task.genDir)})
+			addLocationLabel(out.Rel(), []string{cmd.PathForOutput(out)})
 		}
 
 		referencedDepfile := false
@@ -374,7 +393,7 @@
 			case "out":
 				var sandboxOuts []string
 				for _, out := range task.out {
-					sandboxOuts = append(sandboxOuts, android.SboxPathForOutput(out, task.genDir))
+					sandboxOuts = append(sandboxOuts, cmd.PathForOutput(out))
 				}
 				return strings.Join(sandboxOuts, " "), nil
 			case "depfile":
@@ -384,7 +403,7 @@
 				}
 				return "__SBOX_DEPFILE__", nil
 			case "genDir":
-				return android.SboxPathForOutput(task.genDir, task.genDir), nil
+				return cmd.PathForOutput(task.genDir), nil
 			default:
 				if strings.HasPrefix(name, "location ") {
 					label := strings.TrimSpace(strings.TrimPrefix(name, "location "))
@@ -426,24 +445,6 @@
 		}
 		g.rawCommands = append(g.rawCommands, rawCommand)
 
-		// Pick a unique path outside the task.genDir for the sbox manifest textproto,
-		// a unique rule name, and the user-visible description.
-		manifestName := "genrule.sbox.textproto"
-		desc := "generate"
-		name := "generator"
-		if task.shards > 0 {
-			manifestName = "genrule_" + strconv.Itoa(task.shard) + ".sbox.textproto"
-			desc += " " + strconv.Itoa(task.shard)
-			name += strconv.Itoa(task.shard)
-		} else if len(task.out) == 1 {
-			desc += " " + task.out[0].Base()
-		}
-
-		manifestPath := android.PathForModuleOut(ctx, manifestName)
-
-		// Use a RuleBuilder to create a rule that runs the command inside an sbox sandbox.
-		rule := android.NewRuleBuilder().Sbox(task.genDir, manifestPath)
-		cmd := rule.Command()
 		cmd.Text(rawCommand)
 		cmd.ImplicitOutputs(task.out)
 		cmd.Implicits(task.in)
@@ -454,7 +455,7 @@
 		}
 
 		// Create the rule to run the genrule command inside sbox.
-		rule.Build(pctx, ctx, name, desc)
+		rule.Build(name, desc)
 
 		if len(task.copyTo) > 0 {
 			// If copyTo is set, multiple shards need to be copied into a single directory.
@@ -612,6 +613,10 @@
 			}
 
 			genDir := android.PathForModuleGen(ctx, genSubDir)
+			// TODO(ccross): this RuleBuilder is a hack to be able to call
+			// rule.Command().PathForOutput.  Replace this with passing the rule into the
+			// generator.
+			rule := android.NewRuleBuilder(pctx, ctx).Sbox(genDir, nil)
 
 			for _, in := range shard {
 				outFile := android.GenPathWithExt(ctx, finalSubDir, in, String(properties.Output_extension))
@@ -634,11 +639,11 @@
 					case "in":
 						return in.String(), nil
 					case "out":
-						return android.SboxPathForOutput(outFile, genDir), nil
+						return rule.Command().PathForOutput(outFile), nil
 					case "depfile":
 						// Generate a depfile for each output file.  Store the list for
 						// later in order to combine them all into a single depfile.
-						depFile := android.SboxPathForOutput(outFile.ReplaceExtension(ctx, "d"), genDir)
+						depFile := rule.Command().PathForOutput(outFile.ReplaceExtension(ctx, "d"))
 						commandDepFiles = append(commandDepFiles, depFile)
 						return depFile, nil
 					default:
@@ -703,7 +708,7 @@
 	Shard_size *int64
 }
 
-const defaultShardSize = 100
+const defaultShardSize = 50
 
 func NewGenRule() *Module {
 	properties := &genRuleProperties{}
diff --git a/java/Android.bp b/java/Android.bp
index 9e8dc78..39502b3 100644
--- a/java/Android.bp
+++ b/java/Android.bp
@@ -48,6 +48,7 @@
         "robolectric.go",
         "sdk.go",
         "sdk_library.go",
+        "sdk_library_external.go",
         "support_libraries.go",
         "sysprop.go",
         "system_modules.go",
diff --git a/java/aapt2.go b/java/aapt2.go
index 04e4de5..5346ddf 100644
--- a/java/aapt2.go
+++ b/java/aapt2.go
@@ -25,12 +25,9 @@
 	"android/soong/android"
 )
 
-const AAPT2_SHARD_SIZE = 100
-
 // Convert input resource file path to output file path.
 // values-[config]/<file>.xml -> values-[config]_<file>.arsc.flat;
-// For other resource file, just replace the last "/" with "_" and
-// add .flat extension.
+// For other resource file, just replace the last "/" with "_" and add .flat extension.
 func pathToAapt2Path(ctx android.ModuleContext, res android.Path) android.WritablePath {
 
 	name := res.Base()
@@ -43,6 +40,7 @@
 	return android.PathForModuleOut(ctx, "aapt2", subDir, name)
 }
 
+// pathsToAapt2Paths Calls pathToAapt2Path on each entry of the given Paths, i.e. []Path.
 func pathsToAapt2Paths(ctx android.ModuleContext, resPaths android.Paths) android.WritablePaths {
 	outPaths := make(android.WritablePaths, len(resPaths))
 
@@ -53,6 +51,9 @@
 	return outPaths
 }
 
+// Shard resource files for efficiency. See aapt2Compile for details.
+const AAPT2_SHARD_SIZE = 100
+
 var aapt2CompileRule = pctx.AndroidStaticRule("aapt2Compile",
 	blueprint.RuleParams{
 		Command:     `${config.Aapt2Cmd} compile -o $outDir $cFlags $in`,
@@ -60,14 +61,26 @@
 	},
 	"outDir", "cFlags")
 
+// aapt2Compile compiles resources and puts the results in the requested directory.
 func aapt2Compile(ctx android.ModuleContext, dir android.Path, paths android.Paths,
 	flags []string) android.WritablePaths {
 
+	// Shard the input paths so that they can be processed in parallel. If we shard them into too
+	// small chunks, the additional cost of spinning up aapt2 outweighs the performance gain. The
+	// current shard size, 100, seems to be a good balance between the added cost and the gain.
+	// The aapt2 compile actions are trivially short, but each action in ninja takes on the order of
+	// ~10 ms to run. frameworks/base/core/res/res has >10k resource files, so compiling each one
+	// with an individual action could take 100 CPU seconds. Sharding them reduces the overhead of
+	// starting actions by a factor of 100, at the expense of recompiling more files when one
+	// changes.  Since the individual compiles are trivial it's a good tradeoff.
 	shards := android.ShardPaths(paths, AAPT2_SHARD_SIZE)
 
 	ret := make(android.WritablePaths, 0, len(paths))
 
 	for i, shard := range shards {
+		// This should be kept in sync with pathToAapt2Path. The aapt2 compile command takes an
+		// output directory path, but not output file paths. So, outPaths is just where we expect
+		// the output files will be located.
 		outPaths := pathsToAapt2Paths(ctx, shard)
 		ret = append(ret, outPaths...)
 
@@ -82,6 +95,12 @@
 			Inputs:      shard,
 			Outputs:     outPaths,
 			Args: map[string]string{
+				// The aapt2 compile command takes an output directory path, but not output file paths.
+				// outPaths specified above is only used for dependency management purposes. In order for
+				// the outPaths values to match the actual outputs from aapt2, the dir parameter value
+				// must be a common prefix path of the paths values, and the top-level path segment used
+				// below, "aapt2", must always be kept in sync with the one in pathToAapt2Path.
+				// TODO(b/174505750): Make this easier and robust to use.
 				"outDir": android.PathForModuleOut(ctx, "aapt2", dir.String()).String(),
 				"cFlags": strings.Join(flags, " "),
 			},
@@ -104,6 +123,8 @@
 		},
 	}, "cFlags", "resZipDir", "zipSyncFlags")
 
+// Unzips the given compressed file and compiles the resource source files in it. The zipPrefix
+// parameter points to the subdirectory in the zip file where the resource files are located.
 func aapt2CompileZip(ctx android.ModuleContext, flata android.WritablePath, zip android.Path, zipPrefix string,
 	flags []string) {
 
@@ -163,6 +184,7 @@
 	var inFlags []string
 
 	if len(compiledRes) > 0 {
+		// Create a file that contains the list of all compiled resource file paths.
 		resFileList := android.PathForModuleOut(ctx, "aapt2", "res.list")
 		// Write out file lists to files
 		ctx.Build(pctx, android.BuildParams{
@@ -174,10 +196,12 @@
 
 		deps = append(deps, compiledRes...)
 		deps = append(deps, resFileList)
+		// aapt2 filepath arguments that start with "@" mean file-list files.
 		inFlags = append(inFlags, "@"+resFileList.String())
 	}
 
 	if len(compiledOverlay) > 0 {
+		// Compiled overlay files are processed the same way as compiled resources.
 		overlayFileList := android.PathForModuleOut(ctx, "aapt2", "overlay.list")
 		ctx.Build(pctx, android.BuildParams{
 			Rule:        fileListToFileRule,
@@ -188,9 +212,11 @@
 
 		deps = append(deps, compiledOverlay...)
 		deps = append(deps, overlayFileList)
+		// Compiled overlay files are passed over to aapt2 using -R option.
 		inFlags = append(inFlags, "-R", "@"+overlayFileList.String())
 	}
 
+	// Set auxiliary outputs as implicit outputs to establish correct dependency chains.
 	implicitOutputs := append(splitPackages, proguardOptions, genJar, rTxt, extraPackages)
 	linkOutput := packageRes
 
@@ -212,6 +238,10 @@
 		Implicits:       deps,
 		Output:          linkOutput,
 		ImplicitOutputs: implicitOutputs,
+		// Note the absence of splitPackages. The caller is supposed to compose and provide --split flag
+		// values via the flags parameter when it wants to split outputs.
+		// TODO(b/174509108): Perhaps we can process it in this func while keeping the code reasonably
+		// tidy.
 		Args: map[string]string{
 			"flags":           strings.Join(flags, " "),
 			"inFlags":         strings.Join(inFlags, " "),
@@ -230,6 +260,8 @@
 		CommandDeps: []string{"${config.Aapt2Cmd}"},
 	})
 
+// Converts xml files and resource tables (resources.arsc) in the given jar/apk file to a proto
+// format. The proto definition is available at frameworks/base/tools/aapt2/Resources.proto.
 func aapt2Convert(ctx android.ModuleContext, out android.WritablePath, in android.Path) {
 	ctx.Build(pctx, android.BuildParams{
 		Rule:        aapt2ConvertRule,
diff --git a/java/app.go b/java/app.go
index 3384bbd..4bf9d33 100755
--- a/java/app.go
+++ b/java/app.go
@@ -1115,8 +1115,8 @@
 	}
 
 	fixedConfig := android.PathForModuleOut(ctx, "test_config_fixer", "AndroidTest.xml")
-	rule := android.NewRuleBuilder()
-	command := rule.Command().BuiltTool(ctx, "test_config_fixer").Input(testConfig).Output(fixedConfig)
+	rule := android.NewRuleBuilder(pctx, ctx)
+	command := rule.Command().BuiltTool("test_config_fixer").Input(testConfig).Output(fixedConfig)
 	fixNeeded := false
 
 	if ctx.ModuleName() != a.installApkName {
@@ -1131,7 +1131,7 @@
 	}
 
 	if fixNeeded {
-		rule.Build(pctx, ctx, "fix_test_config", "fix test config")
+		rule.Build("fix_test_config", "fix test config")
 		return fixedConfig
 	}
 	return testConfig
@@ -1440,15 +1440,15 @@
 		})
 		return
 	}
-	rule := android.NewRuleBuilder()
+	rule := android.NewRuleBuilder(pctx, ctx)
 	rule.Command().
 		Textf(`if (zipinfo %s 'lib/*.so' 2>/dev/null | grep -v ' stor ' >/dev/null) ; then`, inputPath).
-		BuiltTool(ctx, "zip2zip").
+		BuiltTool("zip2zip").
 		FlagWithInput("-i ", inputPath).
 		FlagWithOutput("-o ", outputPath).
 		FlagWithArg("-0 ", "'lib/**/*.so'").
 		Textf(`; else cp -f %s %s; fi`, inputPath, outputPath)
-	rule.Build(pctx, ctx, "uncompress-embedded-jni-libs", "Uncompress embedded JIN libs")
+	rule.Build("uncompress-embedded-jni-libs", "Uncompress embedded JIN libs")
 }
 
 // Returns whether this module should have the dex file stored uncompressed in the APK.
@@ -1467,15 +1467,15 @@
 
 func (a *AndroidAppImport) uncompressDex(
 	ctx android.ModuleContext, inputPath android.Path, outputPath android.OutputPath) {
-	rule := android.NewRuleBuilder()
+	rule := android.NewRuleBuilder(pctx, ctx)
 	rule.Command().
 		Textf(`if (zipinfo %s '*.dex' 2>/dev/null | grep -v ' stor ' >/dev/null) ; then`, inputPath).
-		BuiltTool(ctx, "zip2zip").
+		BuiltTool("zip2zip").
 		FlagWithInput("-i ", inputPath).
 		FlagWithOutput("-o ", outputPath).
 		FlagWithArg("-0 ", "'classes*.dex'").
 		Textf(`; else cp -f %s %s; fi`, inputPath, outputPath)
-	rule.Build(pctx, ctx, "uncompress-dex", "Uncompress dex files")
+	rule.Build("uncompress-dex", "Uncompress dex files")
 }
 
 func (a *AndroidAppImport) GenerateAndroidBuildActions(ctx android.ModuleContext) {
@@ -2015,8 +2015,8 @@
 func (u *usesLibrary) verifyUsesLibrariesManifest(ctx android.ModuleContext, manifest android.Path) android.Path {
 	outputFile := android.PathForModuleOut(ctx, "manifest_check", "AndroidManifest.xml")
 
-	rule := android.NewRuleBuilder()
-	cmd := rule.Command().BuiltTool(ctx, "manifest_check").
+	rule := android.NewRuleBuilder(pctx, ctx)
+	cmd := rule.Command().BuiltTool("manifest_check").
 		Flag("--enforce-uses-libraries").
 		Input(manifest).
 		FlagWithOutput("-o ", outputFile)
@@ -2029,7 +2029,7 @@
 		cmd.FlagWithArg("--optional-uses-library ", lib)
 	}
 
-	rule.Build(pctx, ctx, "verify_uses_libraries", "verify <uses-library>")
+	rule.Build("verify_uses_libraries", "verify <uses-library>")
 
 	return outputFile
 }
@@ -2039,7 +2039,7 @@
 func (u *usesLibrary) verifyUsesLibrariesAPK(ctx android.ModuleContext, apk android.Path) android.Path {
 	outputFile := android.PathForModuleOut(ctx, "verify_uses_libraries", apk.Base())
 
-	rule := android.NewRuleBuilder()
+	rule := android.NewRuleBuilder(pctx, ctx)
 	aapt := ctx.Config().HostToolPath(ctx, "aapt")
 	rule.Command().
 		Textf("aapt_binary=%s", aapt.String()).Implicit(aapt).
@@ -2048,7 +2048,7 @@
 		Tool(android.PathForSource(ctx, "build/make/core/verify_uses_libraries.sh")).Input(apk)
 	rule.Command().Text("cp -f").Input(apk).Output(outputFile)
 
-	rule.Build(pctx, ctx, "verify_uses_libraries", "verify <uses-library>")
+	rule.Build("verify_uses_libraries", "verify <uses-library>")
 
 	return outputFile
 }
diff --git a/java/boot_jars.go b/java/boot_jars.go
index e706547..823275b 100644
--- a/java/boot_jars.go
+++ b/java/boot_jars.go
@@ -85,8 +85,8 @@
 
 	timestamp := android.PathForOutput(ctx, "boot-jars-package-check/stamp")
 
-	rule := android.NewRuleBuilder()
-	checkBootJars := rule.Command().BuiltTool(ctx, "check_boot_jars").
+	rule := android.NewRuleBuilder(pctx, ctx)
+	checkBootJars := rule.Command().BuiltTool("check_boot_jars").
 		Input(ctx.Config().HostToolPath(ctx, "dexdump")).
 		Input(android.PathForSource(ctx, "build/soong/scripts/check_boot_jars/package_allowed_list.txt"))
 
@@ -109,7 +109,7 @@
 	}
 
 	checkBootJars.Text("&& touch").Output(timestamp)
-	rule.Build(pctx, ctx, "boot_jars_package_check", "check boot jar packages")
+	rule.Build("boot_jars_package_check", "check boot jar packages")
 
 	// The check-boot-jars phony target depends on the timestamp created if the check succeeds.
 	ctx.Phony("check-boot-jars", timestamp)
diff --git a/java/dexpreopt.go b/java/dexpreopt.go
index a21fb76..67738d4 100644
--- a/java/dexpreopt.go
+++ b/java/dexpreopt.go
@@ -216,7 +216,7 @@
 		return dexJarFile
 	}
 
-	dexpreoptRule.Build(pctx, ctx, "dexpreopt", "dexpreopt")
+	dexpreoptRule.Build("dexpreopt", "dexpreopt")
 
 	d.builtInstalled = dexpreoptRule.Installs().String()
 
diff --git a/java/dexpreopt_bootjars.go b/java/dexpreopt_bootjars.go
index 5df5845..f16ddf1 100644
--- a/java/dexpreopt_bootjars.go
+++ b/java/dexpreopt_bootjars.go
@@ -539,14 +539,14 @@
 	}
 
 	if image.zip != nil {
-		rule := android.NewRuleBuilder()
+		rule := android.NewRuleBuilder(pctx, ctx)
 		rule.Command().
-			BuiltTool(ctx, "soong_zip").
+			BuiltTool("soong_zip").
 			FlagWithOutput("-o ", image.zip).
 			FlagWithArg("-C ", image.dir.Join(ctx, android.Android.String()).String()).
 			FlagWithInputList("-f ", zipFiles, " -f ")
 
-		rule.Build(pctx, ctx, "zip_"+image.name, "zip "+image.name+" image")
+		rule.Build("zip_"+image.name, "zip "+image.name+" image")
 	}
 
 	return image
@@ -568,7 +568,7 @@
 	oatLocation := dexpreopt.PathToLocation(outputPath, arch)
 	imagePath := outputPath.ReplaceExtension(ctx, "art")
 
-	rule := android.NewRuleBuilder()
+	rule := android.NewRuleBuilder(pctx, ctx)
 	rule.MissingDeps(missingDeps)
 
 	rule.Command().Text("mkdir").Flag("-p").Flag(symbolsDir.String())
@@ -689,7 +689,7 @@
 			android.RuleBuilderInstall{unstrippedOat, filepath.Join(installDir, unstrippedOat.Base())})
 	}
 
-	rule.Build(pctx, ctx, image.name+"JarsDexpreopt_"+image.target.String(), "dexpreopt "+image.name+" jars "+arch.String())
+	rule.Build(image.name+"JarsDexpreopt_"+image.target.String(), "dexpreopt "+image.name+" jars "+arch.String())
 
 	// save output and installed files for makevars
 	image.installs = rule.Installs()
@@ -713,7 +713,7 @@
 	profile := ctx.Config().Once(bootImageProfileRuleKey, func() interface{} {
 		defaultProfile := "frameworks/base/config/boot-image-profile.txt"
 
-		rule := android.NewRuleBuilder()
+		rule := android.NewRuleBuilder(pctx, ctx)
 		rule.MissingDeps(missingDeps)
 
 		var bootImageProfile android.Path
@@ -744,7 +744,7 @@
 
 		rule.Install(profile, "/system/etc/boot-image.prof")
 
-		rule.Build(pctx, ctx, "bootJarsProfile", "profile boot jars")
+		rule.Build("bootJarsProfile", "profile boot jars")
 
 		image.profileInstalls = rule.Installs()
 
@@ -766,7 +766,7 @@
 		return nil
 	}
 	return ctx.Config().Once(bootFrameworkProfileRuleKey, func() interface{} {
-		rule := android.NewRuleBuilder()
+		rule := android.NewRuleBuilder(pctx, ctx)
 		rule.MissingDeps(missingDeps)
 
 		// Some branches like master-art-host don't have frameworks/base, so manually
@@ -794,7 +794,7 @@
 			FlagWithOutput("--reference-profile-file=", profile)
 
 		rule.Install(profile, "/system/etc/boot-image.bprof")
-		rule.Build(pctx, ctx, "bootFrameworkProfile", "profile boot framework jars")
+		rule.Build("bootFrameworkProfile", "profile boot framework jars")
 		image.profileInstalls = append(image.profileInstalls, rule.Installs()...)
 
 		return profile
@@ -839,7 +839,7 @@
 		// WriteFileRule automatically adds the last end-of-line.
 		android.WriteFileRule(ctx, updatableBcpPackages, strings.Join(updatablePackages, "\n"))
 
-		rule := android.NewRuleBuilder()
+		rule := android.NewRuleBuilder(pctx, ctx)
 		rule.MissingDeps(missingDeps)
 		rule.Install(updatableBcpPackages, "/system/etc/"+updatableBcpPackagesName)
 		// TODO: Rename `profileInstalls` to `extraInstalls`?
@@ -863,25 +863,25 @@
 		}
 		// Create a rule to call oatdump.
 		output := android.PathForOutput(ctx, "boot."+suffix+".oatdump.txt")
-		rule := android.NewRuleBuilder()
+		rule := android.NewRuleBuilder(pctx, ctx)
 		rule.Command().
 			// TODO: for now, use the debug version for better error reporting
-			BuiltTool(ctx, "oatdumpd").
+			BuiltTool("oatdumpd").
 			FlagWithInputList("--runtime-arg -Xbootclasspath:", image.dexPathsDeps.Paths(), ":").
 			FlagWithList("--runtime-arg -Xbootclasspath-locations:", image.dexLocationsDeps, ":").
 			FlagWithArg("--image=", strings.Join(image.imageLocations(), ":")).Implicits(image.imagesDeps.Paths()).
 			FlagWithOutput("--output=", output).
 			FlagWithArg("--instruction-set=", arch.String())
-		rule.Build(pctx, ctx, "dump-oat-boot-"+suffix, "dump oat boot "+arch.String())
+		rule.Build("dump-oat-boot-"+suffix, "dump oat boot "+arch.String())
 
 		// Create a phony rule that depends on the output file and prints the path.
 		phony := android.PathForPhony(ctx, "dump-oat-boot-"+suffix)
-		rule = android.NewRuleBuilder()
+		rule = android.NewRuleBuilder(pctx, ctx)
 		rule.Command().
 			Implicit(output).
 			ImplicitOutput(phony).
 			Text("echo").FlagWithArg("Output in ", output.String())
-		rule.Build(pctx, ctx, "phony-dump-oat-boot-"+suffix, "dump oat boot "+arch.String())
+		rule.Build("phony-dump-oat-boot-"+suffix, "dump oat boot "+arch.String())
 
 		allPhonies = append(allPhonies, phony)
 	}
diff --git a/java/droiddoc.go b/java/droiddoc.go
index da8489a..9c88a3c 100644
--- a/java/droiddoc.go
+++ b/java/droiddoc.go
@@ -671,7 +671,7 @@
 
 	j.stubsSrcJar = nil
 
-	rule := android.NewRuleBuilder()
+	rule := android.NewRuleBuilder(pctx, ctx)
 
 	rule.Command().Text("rm -rf").Text(outDir.String())
 	rule.Command().Text("mkdir -p").Text(outDir.String())
@@ -689,7 +689,7 @@
 		Flag("-Xdoclint:none")
 
 	rule.Command().
-		BuiltTool(ctx, "soong_zip").
+		BuiltTool("soong_zip").
 		Flag("-write_if_changed").
 		Flag("-d").
 		FlagWithOutput("-o ", j.docZip).
@@ -700,7 +700,7 @@
 
 	zipSyncCleanupCmd(rule, srcJarDir)
 
-	rule.Build(pctx, ctx, "javadoc", "javadoc")
+	rule.Build("javadoc", "javadoc")
 }
 
 //
@@ -845,7 +845,7 @@
 	outDir, srcJarDir, srcJarList android.Path, sourcepaths android.Paths) *android.RuleBuilderCommand {
 
 	cmd := rule.Command().
-		BuiltTool(ctx, "soong_javac_wrapper").Tool(config.JavadocCmd(ctx)).
+		BuiltTool("soong_javac_wrapper").Tool(config.JavadocCmd(ctx)).
 		Flag(config.JavacVmFlags).
 		FlagWithArg("-encoding ", "UTF-8").
 		FlagWithRspFileInputList("@", srcs).
@@ -914,7 +914,7 @@
 	dokkaClasspath := append(bootclasspath.Paths(), classpath.Paths()...)
 
 	return rule.Command().
-		BuiltTool(ctx, "dokka").
+		BuiltTool("dokka").
 		Flag(config.JavacVmFlags).
 		Flag(srcJarDir.String()).
 		FlagWithInputList("-classpath ", dokkaClasspath, ":").
@@ -934,7 +934,7 @@
 	outDir := android.PathForModuleOut(ctx, "out")
 	srcJarDir := android.PathForModuleOut(ctx, "srcjars")
 
-	rule := android.NewRuleBuilder()
+	rule := android.NewRuleBuilder(pctx, ctx)
 
 	srcJarList := zipSyncCmd(ctx, rule, srcJarDir, d.Javadoc.srcJars)
 
@@ -968,7 +968,7 @@
 	}
 
 	rule.Command().
-		BuiltTool(ctx, "soong_zip").
+		BuiltTool("soong_zip").
 		Flag("-write_if_changed").
 		Flag("-d").
 		FlagWithOutput("-o ", d.docZip).
@@ -979,7 +979,7 @@
 
 	zipSyncCleanupCmd(rule, srcJarDir)
 
-	rule.Build(pctx, ctx, "javadoc", desc)
+	rule.Build("javadoc", desc)
 }
 
 //
@@ -1278,7 +1278,7 @@
 		}).NoVarTemplate(ctx.Config()))
 	}
 
-	cmd.BuiltTool(ctx, "metalava").
+	cmd.BuiltTool("metalava").
 		Flag(config.JavacVmFlags).
 		Flag("-J--add-opens=java.base/java.util=ALL-UNNAMED").
 		FlagWithArg("-encoding ", "UTF-8").
@@ -1333,7 +1333,7 @@
 
 	srcJarDir := android.PathForModuleOut(ctx, "srcjars")
 
-	rule := android.NewRuleBuilder()
+	rule := android.NewRuleBuilder(pctx, ctx)
 
 	if BoolDefault(d.properties.High_mem, false) {
 		// This metalava run uses lots of memory, restrict the number of metalava jobs that can run in parallel.
@@ -1480,19 +1480,19 @@
 		cmd.FlagWithArg("--error-message:compatibility:released ", msg)
 	}
 
-	impRule := android.NewRuleBuilder()
+	impRule := android.NewRuleBuilder(pctx, ctx)
 	impCmd := impRule.Command()
 	// An action that copies the ninja generated rsp file to a new location. This allows us to
 	// add a large number of inputs to a file without exceeding bash command length limits (which
 	// would happen if we use the WriteFile rule). The cp is needed because RuleBuilder sets the
 	// rsp file to be ${output}.rsp.
 	impCmd.Text("cp").FlagWithRspFileInputList("", cmd.GetImplicits()).Output(implicitsRsp)
-	impRule.Build(pctx, ctx, "implicitsGen", "implicits generation")
+	impRule.Build("implicitsGen", "implicits generation")
 	cmd.Implicit(implicitsRsp)
 
 	if generateStubs {
 		rule.Command().
-			BuiltTool(ctx, "soong_zip").
+			BuiltTool("soong_zip").
 			Flag("-write_if_changed").
 			Flag("-jar").
 			FlagWithOutput("-o ", d.Javadoc.stubsSrcJar).
@@ -1503,7 +1503,7 @@
 	if Bool(d.properties.Write_sdk_values) {
 		d.metadataZip = android.PathForModuleOut(ctx, ctx.ModuleName()+"-metadata.zip")
 		rule.Command().
-			BuiltTool(ctx, "soong_zip").
+			BuiltTool("soong_zip").
 			Flag("-write_if_changed").
 			Flag("-d").
 			FlagWithOutput("-o ", d.metadataZip).
@@ -1524,7 +1524,7 @@
 
 	zipSyncCleanupCmd(rule, srcJarDir)
 
-	rule.Build(pctx, ctx, "metalava", "metalava merged")
+	rule.Build("metalava", "metalava merged")
 
 	if apiCheckEnabled(ctx, d.properties.Check_api.Current, "current") {
 
@@ -1542,7 +1542,7 @@
 
 		d.checkCurrentApiTimestamp = android.PathForModuleOut(ctx, "check_current_api.timestamp")
 
-		rule := android.NewRuleBuilder()
+		rule := android.NewRuleBuilder(pctx, ctx)
 
 		// Diff command line.
 		// -F matches the closest "opening" line, such as "package android {"
@@ -1564,7 +1564,7 @@
 			`   1. You can add '@hide' javadoc comments (and remove @SystemApi/@TestApi/etc)\n`+
 			`      to the new methods, etc. shown in the above diff.\n\n`+
 			`   2. You can update current.txt and/or removed.txt by executing the following command:\n`+
-			`         make %s-update-current-api\n\n`+
+			`         m %s-update-current-api\n\n`+
 			`      To submit the revised current.txt to the main Android repository,\n`+
 			`      you will need approval.\n`+
 			`******************************\n`, ctx.ModuleName())
@@ -1576,12 +1576,12 @@
 			Text("; exit 38").
 			Text(")")
 
-		rule.Build(pctx, ctx, "metalavaCurrentApiCheck", "check current API")
+		rule.Build("metalavaCurrentApiCheck", "check current API")
 
 		d.updateCurrentApiTimestamp = android.PathForModuleOut(ctx, "update_current_api.timestamp")
 
 		// update API rule
-		rule = android.NewRuleBuilder()
+		rule = android.NewRuleBuilder(pctx, ctx)
 
 		rule.Command().Text("( true")
 
@@ -1602,7 +1602,7 @@
 			Text("; exit 38").
 			Text(")")
 
-		rule.Build(pctx, ctx, "metalavaCurrentApiUpdate", "update current API")
+		rule.Build("metalavaCurrentApiUpdate", "update current API")
 	}
 
 	if String(d.properties.Check_nullability_warnings) != "" {
@@ -1625,7 +1625,7 @@
 			`       and submitting the updated file as part of your change.`,
 			d.nullabilityWarningsFile, checkNullabilityWarnings)
 
-		rule := android.NewRuleBuilder()
+		rule := android.NewRuleBuilder(pctx, ctx)
 
 		rule.Command().
 			Text("(").
@@ -1637,7 +1637,7 @@
 			Text("; exit 38").
 			Text(")")
 
-		rule.Build(pctx, ctx, "nullabilityWarningsCheck", "nullability warnings check")
+		rule.Build("nullabilityWarningsCheck", "nullability warnings check")
 	}
 }
 
@@ -1722,7 +1722,7 @@
 
 	rule.Temporary(srcJarList)
 
-	rule.Command().BuiltTool(ctx, "zipsync").
+	rule.Command().BuiltTool("zipsync").
 		FlagWithArg("-d ", srcJarDir.String()).
 		FlagWithOutput("-l ", srcJarList).
 		FlagWithArg("-f ", `"*.java"`).
@@ -1783,9 +1783,9 @@
 	srcGlob := localSrcDir + "/**/*"
 	srcPaths := android.PathsForModuleSrc(ctx, []string{srcGlob})
 
-	rule := android.NewRuleBuilder()
+	rule := android.NewRuleBuilder(pctx, ctx)
 	rule.Command().
-		BuiltTool(ctx, "soong_zip").
+		BuiltTool("soong_zip").
 		Flag("-write_if_changed").
 		Flag("-jar").
 		FlagWithOutput("-o ", p.stubsSrcJar).
@@ -1794,7 +1794,7 @@
 
 	rule.Restat()
 
-	rule.Build(pctx, ctx, "zip src", "Create srcjar from prebuilt source")
+	rule.Build("zip src", "Create srcjar from prebuilt source")
 }
 
 func (p *PrebuiltStubsSources) Prebuilt() *android.Prebuilt {
diff --git a/java/gen.go b/java/gen.go
index d50a665..5766a94 100644
--- a/java/gen.go
+++ b/java/gen.go
@@ -57,7 +57,7 @@
 
 		outDir := srcJarFile.ReplaceExtension(ctx, "tmp")
 
-		rule := android.NewRuleBuilder()
+		rule := android.NewRuleBuilder(pctx, ctx)
 
 		rule.Command().Text("rm -rf").Flag(outDir.String())
 		rule.Command().Text("mkdir -p").Flag(outDir.String())
@@ -98,7 +98,7 @@
 			ruleDesc += " " + strconv.Itoa(i)
 		}
 
-		rule.Build(pctx, ctx, ruleName, ruleDesc)
+		rule.Build(ruleName, ruleDesc)
 	}
 
 	return srcJarFiles
diff --git a/java/hiddenapi.go b/java/hiddenapi.go
index 63b801a..71f1e57 100644
--- a/java/hiddenapi.go
+++ b/java/hiddenapi.go
@@ -135,12 +135,12 @@
 	})
 	h.metadataCSVPath = metadataCSV
 
-	rule := android.NewRuleBuilder()
+	rule := android.NewRuleBuilder(pctx, ctx)
 	rule.Command().
-		BuiltTool(ctx, "merge_csv").
+		BuiltTool("merge_csv").
 		FlagWithInput("--zip_input=", classesJar).
 		FlagWithOutput("--output=", indexCSV)
-	rule.Build(pctx, ctx, "merged-hiddenapi-index", "Merged Hidden API index")
+	rule.Build("merged-hiddenapi-index", "Merged Hidden API index")
 	h.indexCSVPath = indexCSV
 }
 
diff --git a/java/hiddenapi_singleton.go b/java/hiddenapi_singleton.go
index 8f0e09c..ce8410e 100644
--- a/java/hiddenapi_singleton.go
+++ b/java/hiddenapi_singleton.go
@@ -189,7 +189,7 @@
 	}
 
 	// Singleton rule which applies hiddenapi on all boot class path dex files.
-	rule := android.NewRuleBuilder()
+	rule := android.NewRuleBuilder(pctx, ctx)
 
 	outputPath := hiddenAPISingletonPaths(ctx).stubFlags
 	tempPath := android.PathForOutput(ctx, outputPath.Rel()+".tmp")
@@ -208,7 +208,7 @@
 
 	commitChangeForRestat(rule, tempPath, outputPath)
 
-	rule.Build(pctx, ctx, "hiddenAPIStubFlagsFile", "hiddenapi stub flags")
+	rule.Build("hiddenAPIStubFlagsFile", "hiddenapi stub flags")
 }
 
 // flagsRule creates a rule to build hiddenapi-flags.csv out of flags.csv files generated for boot image modules and
@@ -236,7 +236,7 @@
 		ctx.Errorf("Failed to find combined-removed-dex.")
 	}
 
-	rule := android.NewRuleBuilder()
+	rule := android.NewRuleBuilder(pctx, ctx)
 
 	outputPath := hiddenAPISingletonPaths(ctx).flags
 	tempPath := android.PathForOutput(ctx, outputPath.Rel()+".tmp")
@@ -266,7 +266,7 @@
 
 	commitChangeForRestat(rule, tempPath, outputPath)
 
-	rule.Build(pctx, ctx, "hiddenAPIFlagsFile", "hiddenapi flags")
+	rule.Build("hiddenAPIFlagsFile", "hiddenapi flags")
 
 	return outputPath
 }
@@ -274,14 +274,14 @@
 // emptyFlagsRule creates a rule to build an empty hiddenapi-flags.csv, which is needed by master-art-host builds that
 // have a partial manifest without frameworks/base but still need to build a boot image.
 func emptyFlagsRule(ctx android.SingletonContext) android.Path {
-	rule := android.NewRuleBuilder()
+	rule := android.NewRuleBuilder(pctx, ctx)
 
 	outputPath := hiddenAPISingletonPaths(ctx).flags
 
 	rule.Command().Text("rm").Flag("-f").Output(outputPath)
 	rule.Command().Text("touch").Output(outputPath)
 
-	rule.Build(pctx, ctx, "emptyHiddenAPIFlagsFile", "empty hiddenapi flags")
+	rule.Build("emptyHiddenAPIFlagsFile", "empty hiddenapi flags")
 
 	return outputPath
 }
@@ -299,16 +299,16 @@
 		}
 	})
 
-	rule := android.NewRuleBuilder()
+	rule := android.NewRuleBuilder(pctx, ctx)
 
 	outputPath := hiddenAPISingletonPaths(ctx).metadata
 
 	rule.Command().
-		BuiltTool(ctx, "merge_csv").
+		BuiltTool("merge_csv").
 		FlagWithOutput("--output=", outputPath).
 		Inputs(metadataCSV)
 
-	rule.Build(pctx, ctx, "hiddenAPIGreylistMetadataFile", "hiddenapi greylist metadata")
+	rule.Build("hiddenAPIGreylistMetadataFile", "hiddenapi greylist metadata")
 
 	return outputPath
 }
@@ -399,13 +399,13 @@
 		}
 	})
 
-	rule := android.NewRuleBuilder()
+	rule := android.NewRuleBuilder(pctx, ctx)
 	rule.Command().
-		BuiltTool(ctx, "merge_csv").
+		BuiltTool("merge_csv").
 		FlagWithArg("--header=", "signature,file,startline,startcol,endline,endcol,properties").
 		FlagWithOutput("--output=", hiddenAPISingletonPaths(ctx).index).
 		Inputs(indexes)
-	rule.Build(pctx, ctx, "singleton-merged-hiddenapi-index", "Singleton merged Hidden API index")
+	rule.Build("singleton-merged-hiddenapi-index", "Singleton merged Hidden API index")
 
 	h.index = hiddenAPISingletonPaths(ctx).index
 }
diff --git a/java/java.go b/java/java.go
index 8738e00..3d121cc 100644
--- a/java/java.go
+++ b/java/java.go
@@ -772,6 +772,37 @@
 	libDeps := ctx.AddVariationDependencies(nil, libTag, rewriteSyspropLibs(j.properties.Libs, "libs")...)
 	ctx.AddVariationDependencies(nil, staticLibTag, rewriteSyspropLibs(j.properties.Static_libs, "static_libs")...)
 
+	if ctx.DeviceConfig().VndkVersion() != "" && ctx.Config().EnforceInterPartitionJavaSdkLibrary() {
+		// Require java_sdk_library at inter-partition java dependency to ensure stable
+		// interface between partitions. If inter-partition java_library dependency is detected,
+		// raise build error because java_library doesn't have a stable interface.
+		//
+		// Inputs:
+		//    PRODUCT_ENFORCE_INTER_PARTITION_JAVA_SDK_LIBRARY
+		//      if true, enable enforcement
+		//    PRODUCT_INTER_PARTITION_JAVA_LIBRARY_ALLOWLIST
+		//      exception list of java_library names to allow inter-partition dependency
+		for idx, lib := range j.properties.Libs {
+			if libDeps[idx] == nil {
+				continue
+			}
+
+			if _, ok := syspropPublicStubs[lib]; ok {
+				continue
+			}
+
+			if javaDep, ok := libDeps[idx].(javaSdkLibraryEnforceContext); ok {
+				// java_sdk_library is always allowed at inter-partition dependency.
+				// So, skip check.
+				if _, ok := javaDep.(*SdkLibrary); ok {
+					continue
+				}
+
+				j.checkPartitionsForJavaDependency(ctx, "libs", javaDep)
+			}
+		}
+	}
+
 	// For library dependencies that are component libraries (like stubs), add the implementation
 	// as a dependency (dexpreopt needs to be against the implementation library, not stubs).
 	for _, dep := range libDeps {
@@ -1415,6 +1446,9 @@
 		kotlincFlags := j.properties.Kotlincflags
 		CheckKotlincFlags(ctx, kotlincFlags)
 
+		// Dogfood the JVM_IR backend.
+		kotlincFlags = append(kotlincFlags, "-Xuse-ir")
+
 		// If there are kotlin files, compile them first but pass all the kotlin and java files
 		// kotlinc will use the java files to resolve types referenced by the kotlin files, but
 		// won't emit any classes for them.
@@ -3049,21 +3083,21 @@
 	dexOutputFile := android.PathForModuleOut(ctx, ctx.ModuleName()+".jar")
 
 	if j.dexpreopter.uncompressedDex {
-		rule := android.NewRuleBuilder()
+		rule := android.NewRuleBuilder(pctx, ctx)
 
 		temporary := android.PathForModuleOut(ctx, ctx.ModuleName()+".jar.unaligned")
 		rule.Temporary(temporary)
 
 		// use zip2zip to uncompress classes*.dex files
 		rule.Command().
-			BuiltTool(ctx, "zip2zip").
+			BuiltTool("zip2zip").
 			FlagWithInput("-i ", inputJar).
 			FlagWithOutput("-o ", temporary).
 			FlagWithArg("-0 ", "'classes*.dex'")
 
 		// use zipalign to align uncompressed classes*.dex files
 		rule.Command().
-			BuiltTool(ctx, "zipalign").
+			BuiltTool("zipalign").
 			Flag("-f").
 			Text("4").
 			Input(temporary).
@@ -3071,7 +3105,7 @@
 
 		rule.DeleteTemporaryFiles()
 
-		rule.Build(pctx, ctx, "uncompress_dex", "uncompress dex")
+		rule.Build("uncompress_dex", "uncompress dex")
 	} else {
 		ctx.Build(pctx, android.BuildParams{
 			Rule:   android.Cp,
diff --git a/java/java_test.go b/java/java_test.go
index 83db443..f7cf03f 100644
--- a/java/java_test.go
+++ b/java/java_test.go
@@ -805,6 +805,165 @@
 	})
 }
 
+func TestJavaSdkLibraryEnforce(t *testing.T) {
+	partitionToBpOption := func(partition string) string {
+		switch partition {
+		case "system":
+			return ""
+		case "vendor":
+			return "soc_specific: true,"
+		case "product":
+			return "product_specific: true,"
+		default:
+			panic("Invalid partition group name: " + partition)
+		}
+	}
+
+	type testConfigInfo struct {
+		libraryType                string
+		fromPartition              string
+		toPartition                string
+		enforceVendorInterface     bool
+		enforceProductInterface    bool
+		enforceJavaSdkLibraryCheck bool
+		allowList                  []string
+	}
+
+	createTestConfig := func(info testConfigInfo) android.Config {
+		bpFileTemplate := `
+			java_library {
+				name: "foo",
+				srcs: ["foo.java"],
+				libs: ["bar"],
+				sdk_version: "current",
+				%s
+			}
+
+			%s {
+				name: "bar",
+				srcs: ["bar.java"],
+				sdk_version: "current",
+				%s
+			}
+		`
+
+		bpFile := fmt.Sprintf(bpFileTemplate,
+			partitionToBpOption(info.fromPartition),
+			info.libraryType,
+			partitionToBpOption(info.toPartition))
+
+		config := testConfig(nil, bpFile, nil)
+		configVariables := config.TestProductVariables
+
+		configVariables.EnforceProductPartitionInterface = proptools.BoolPtr(info.enforceProductInterface)
+		if info.enforceVendorInterface {
+			configVariables.DeviceVndkVersion = proptools.StringPtr("current")
+		}
+		configVariables.EnforceInterPartitionJavaSdkLibrary = proptools.BoolPtr(info.enforceJavaSdkLibraryCheck)
+		configVariables.InterPartitionJavaLibraryAllowList = info.allowList
+
+		return config
+	}
+
+	isValidDependency := func(configInfo testConfigInfo) bool {
+		if configInfo.enforceVendorInterface == false {
+			return true
+		}
+
+		if configInfo.enforceJavaSdkLibraryCheck == false {
+			return true
+		}
+
+		if inList("bar", configInfo.allowList) {
+			return true
+		}
+
+		if configInfo.libraryType == "java_library" {
+			if configInfo.fromPartition != configInfo.toPartition {
+				if !configInfo.enforceProductInterface &&
+					((configInfo.fromPartition == "system" && configInfo.toPartition == "product") ||
+						(configInfo.fromPartition == "product" && configInfo.toPartition == "system")) {
+					return true
+				}
+				return false
+			}
+		}
+
+		return true
+	}
+
+	errorMessage := "is not allowed across the partitions"
+
+	allPartitionCombinations := func() [][2]string {
+		var result [][2]string
+		partitions := []string{"system", "vendor", "product"}
+
+		for _, fromPartition := range partitions {
+			for _, toPartition := range partitions {
+				result = append(result, [2]string{fromPartition, toPartition})
+			}
+		}
+
+		return result
+	}
+
+	allFlagCombinations := func() [][3]bool {
+		var result [][3]bool
+		flagValues := [2]bool{false, true}
+
+		for _, vendorInterface := range flagValues {
+			for _, productInterface := range flagValues {
+				for _, enableEnforce := range flagValues {
+					result = append(result, [3]bool{vendorInterface, productInterface, enableEnforce})
+				}
+			}
+		}
+
+		return result
+	}
+
+	for _, libraryType := range []string{"java_library", "java_sdk_library"} {
+		for _, partitionValues := range allPartitionCombinations() {
+			for _, flagValues := range allFlagCombinations() {
+				testInfo := testConfigInfo{
+					libraryType:                libraryType,
+					fromPartition:              partitionValues[0],
+					toPartition:                partitionValues[1],
+					enforceVendorInterface:     flagValues[0],
+					enforceProductInterface:    flagValues[1],
+					enforceJavaSdkLibraryCheck: flagValues[2],
+				}
+
+				if isValidDependency(testInfo) {
+					testJavaWithConfig(t, createTestConfig(testInfo))
+				} else {
+					testJavaErrorWithConfig(t, errorMessage, createTestConfig(testInfo))
+				}
+			}
+		}
+	}
+
+	testJavaWithConfig(t, createTestConfig(testConfigInfo{
+		libraryType:                "java_library",
+		fromPartition:              "vendor",
+		toPartition:                "system",
+		enforceVendorInterface:     true,
+		enforceProductInterface:    true,
+		enforceJavaSdkLibraryCheck: true,
+		allowList:                  []string{"bar"},
+	}))
+
+	testJavaErrorWithConfig(t, errorMessage, createTestConfig(testConfigInfo{
+		libraryType:                "java_library",
+		fromPartition:              "vendor",
+		toPartition:                "system",
+		enforceVendorInterface:     true,
+		enforceProductInterface:    true,
+		enforceJavaSdkLibraryCheck: true,
+		allowList:                  []string{"foo"},
+	}))
+}
+
 func TestDefaults(t *testing.T) {
 	ctx, _ := testJava(t, `
 		java_defaults {
diff --git a/java/kotlin.go b/java/kotlin.go
index e8c030a..8067ad5 100644
--- a/java/kotlin.go
+++ b/java/kotlin.go
@@ -63,9 +63,9 @@
 		// we can't use the rsp file because it is already being used for srcs.
 		// Insert a second rule to write out the list of resources to a file.
 		commonSrcsList := android.PathForModuleOut(ctx, "kotlinc_common_srcs.list")
-		rule := android.NewRuleBuilder()
+		rule := android.NewRuleBuilder(pctx, ctx)
 		rule.Command().Text("cp").FlagWithRspFileInputList("", commonSrcFiles).Output(commonSrcsList)
-		rule.Build(pctx, ctx, "kotlin_common_srcs_list", "kotlin common_srcs list")
+		rule.Build("kotlin_common_srcs_list", "kotlin common_srcs list")
 		return android.OptionalPathForPath(commonSrcsList)
 	}
 	return android.OptionalPath{}
diff --git a/java/lint.go b/java/lint.go
index 11f92e5..cd2a904 100644
--- a/java/lint.go
+++ b/java/lint.go
@@ -176,9 +176,9 @@
 		// we can't use the rsp file because it is already being used for srcs.
 		// Insert a second rule to write out the list of resources to a file.
 		resourcesList = android.PathForModuleOut(ctx, "lint", "resources.list")
-		resListRule := android.NewRuleBuilder()
+		resListRule := android.NewRuleBuilder(pctx, ctx)
 		resListRule.Command().Text("cp").FlagWithRspFileInputList("", l.resources).Output(resourcesList)
-		resListRule.Build(pctx, ctx, "lint_resources_list", "lint resources list")
+		resListRule.Build("lint_resources_list", "lint resources list")
 		deps = append(deps, l.resources...)
 	}
 
@@ -192,7 +192,7 @@
 	srcJarList := zipSyncCmd(ctx, rule, srcJarDir, l.srcJars)
 
 	cmd := rule.Command().
-		BuiltTool(ctx, "lint-project-xml").
+		BuiltTool("lint-project-xml").
 		FlagWithOutput("--project_out ", projectXMLPath).
 		FlagWithOutput("--config_out ", configXMLPath).
 		FlagWithArg("--name ", ctx.ModuleName())
@@ -284,7 +284,7 @@
 		}
 	}
 
-	rule := android.NewRuleBuilder()
+	rule := android.NewRuleBuilder(pctx, ctx)
 
 	if l.manifest == nil {
 		manifest := l.generateManifest(ctx, rule)
@@ -347,7 +347,7 @@
 
 	rule.Command().Text("rm -rf").Flag(cacheDir.String()).Flag(homeDir.String())
 
-	rule.Build(pctx, ctx, "lint", "lint")
+	rule.Build("lint", "lint")
 
 	l.outputs = lintOutputs{
 		html: html,
@@ -511,12 +511,12 @@
 		return paths[i].String() < paths[j].String()
 	})
 
-	rule := android.NewRuleBuilder()
+	rule := android.NewRuleBuilder(pctx, ctx)
 
-	rule.Command().BuiltTool(ctx, "soong_zip").
+	rule.Command().BuiltTool("soong_zip").
 		FlagWithOutput("-o ", outputPath).
 		FlagWithArg("-C ", android.PathForIntermediates(ctx).String()).
 		FlagWithRspFileInputList("-r ", paths)
 
-	rule.Build(pctx, ctx, outputPath.Base(), outputPath.Base())
+	rule.Build(outputPath.Base(), outputPath.Base())
 }
diff --git a/java/platform_compat_config.go b/java/platform_compat_config.go
index cb8e684..9bc821d 100644
--- a/java/platform_compat_config.go
+++ b/java/platform_compat_config.go
@@ -86,15 +86,15 @@
 		return
 	}
 
-	rule := android.NewRuleBuilder()
+	rule := android.NewRuleBuilder(pctx, ctx)
 	outputPath := platformCompatConfigPath(ctx)
 
 	rule.Command().
-		BuiltTool(ctx, "process-compat-config").
+		BuiltTool("process-compat-config").
 		FlagForEachInput("--xml ", compatConfigMetadata).
 		FlagWithOutput("--merged-config ", outputPath)
 
-	rule.Build(pctx, ctx, "merged-compat-config", "Merge compat config")
+	rule.Build("merged-compat-config", "Merge compat config")
 
 	p.metadata = outputPath
 }
@@ -106,7 +106,7 @@
 }
 
 func (p *platformCompatConfig) GenerateAndroidBuildActions(ctx android.ModuleContext) {
-	rule := android.NewRuleBuilder()
+	rule := android.NewRuleBuilder(pctx, ctx)
 
 	configFileName := p.Name() + ".xml"
 	metadataFileName := p.Name() + "_meta.xml"
@@ -115,13 +115,13 @@
 	path := android.PathForModuleSrc(ctx, String(p.properties.Src))
 
 	rule.Command().
-		BuiltTool(ctx, "process-compat-config").
+		BuiltTool("process-compat-config").
 		FlagWithInput("--jar ", path).
 		FlagWithOutput("--device-config ", p.configFile).
 		FlagWithOutput("--merged-config ", p.metadataFile)
 
 	p.installDirPath = android.PathForModuleInstall(ctx, "etc", "compatconfig")
-	rule.Build(pctx, ctx, configFileName, "Extract compat/compat_config.xml and install it")
+	rule.Build(configFileName, "Extract compat/compat_config.xml and install it")
 
 }
 
diff --git a/java/proto.go b/java/proto.go
index 4d735eb..cc9abbe 100644
--- a/java/proto.go
+++ b/java/proto.go
@@ -34,7 +34,7 @@
 
 		outDir := srcJarFile.ReplaceExtension(ctx, "tmp")
 
-		rule := android.NewRuleBuilder()
+		rule := android.NewRuleBuilder(pctx, ctx)
 
 		rule.Command().Text("rm -rf").Flag(outDir.String())
 		rule.Command().Text("mkdir -p").Flag(outDir.String())
@@ -42,13 +42,13 @@
 		for _, protoFile := range shard {
 			depFile := srcJarFile.InSameDir(ctx, protoFile.String()+".d")
 			rule.Command().Text("mkdir -p").Flag(filepath.Dir(depFile.String()))
-			android.ProtoRule(ctx, rule, protoFile, flags, flags.Deps, outDir, depFile, nil)
+			android.ProtoRule(rule, protoFile, flags, flags.Deps, outDir, depFile, nil)
 		}
 
 		// Proto generated java files have an unknown package name in the path, so package the entire output directory
 		// into a srcjar.
 		rule.Command().
-			BuiltTool(ctx, "soong_zip").
+			BuiltTool("soong_zip").
 			Flag("-jar").
 			Flag("-write_if_changed").
 			FlagWithOutput("-o ", srcJarFile).
@@ -66,7 +66,7 @@
 			ruleDesc += " " + strconv.Itoa(i)
 		}
 
-		rule.Build(pctx, ctx, ruleName, ruleDesc)
+		rule.Build(ruleName, ruleDesc)
 	}
 
 	return srcJarFiles
diff --git a/java/robolectric.go b/java/robolectric.go
index 62d1d99..419efda 100644
--- a/java/robolectric.go
+++ b/java/robolectric.go
@@ -199,7 +199,7 @@
 
 func generateRoboTestConfig(ctx android.ModuleContext, outputFile android.WritablePath,
 	instrumentedApp *AndroidApp) {
-	rule := android.NewRuleBuilder()
+	rule := android.NewRuleBuilder(pctx, ctx)
 
 	manifest := instrumentedApp.mergedManifestFile
 	resourceApk := instrumentedApp.outputFile
@@ -213,11 +213,11 @@
 		Implicit(manifest).
 		Implicit(resourceApk)
 
-	rule.Build(pctx, ctx, "generate_test_config", "generate test_config.properties")
+	rule.Build("generate_test_config", "generate test_config.properties")
 }
 
 func generateSameDirRoboTestConfigJar(ctx android.ModuleContext, outputFile android.ModuleOutPath) {
-	rule := android.NewRuleBuilder()
+	rule := android.NewRuleBuilder(pctx, ctx)
 
 	outputDir := outputFile.InSameDir(ctx)
 	configFile := outputDir.Join(ctx, "com/android/tools/test_config.properties")
@@ -230,12 +230,12 @@
 		Textf(`echo "android_resource_apk=%s.apk"`, ctx.ModuleName()).
 		Text(") >>").Output(configFile)
 	rule.Command().
-		BuiltTool(ctx, "soong_zip").
+		BuiltTool("soong_zip").
 		FlagWithArg("-C ", outputDir.String()).
 		FlagWithInput("-f ", configFile).
 		FlagWithOutput("-o ", outputFile)
 
-	rule.Build(pctx, ctx, "generate_test_config_samedir", "generate test_config.properties")
+	rule.Build("generate_test_config_samedir", "generate test_config.properties")
 }
 
 func (r *robolectricTest) generateRoboSrcJar(ctx android.ModuleContext, outputFile android.WritablePath,
diff --git a/java/sdk.go b/java/sdk.go
index 971791f..32a4b5a 100644
--- a/java/sdk.go
+++ b/java/sdk.go
@@ -544,7 +544,7 @@
 
 	commitChangeForRestat(rule, tempPath, combinedAidl)
 
-	rule.Build(pctx, ctx, "framework_aidl", "generate framework.aidl")
+	rule.Build("framework_aidl", "generate framework.aidl")
 }
 
 // Creates a version of framework.aidl for the non-updatable part of the platform.
@@ -558,7 +558,7 @@
 
 	commitChangeForRestat(rule, tempPath, combinedAidl)
 
-	rule.Build(pctx, ctx, "framework_non_updatable_aidl", "generate framework_non_updatable.aidl")
+	rule.Build("framework_non_updatable_aidl", "generate framework_non_updatable.aidl")
 }
 
 func createFrameworkAidl(stubsModules []string, path android.OutputPath, ctx android.SingletonContext) *android.RuleBuilder {
@@ -586,7 +586,7 @@
 		}
 	}
 
-	rule := android.NewRuleBuilder()
+	rule := android.NewRuleBuilder(pctx, ctx)
 	rule.MissingDeps(missingDeps)
 
 	var aidls android.Paths
@@ -597,7 +597,7 @@
 			rule.Command().
 				Text("rm -f").Output(aidl)
 			rule.Command().
-				BuiltTool(ctx, "sdkparcelables").
+				BuiltTool("sdkparcelables").
 				Input(jar).
 				Output(aidl)
 
@@ -632,7 +632,7 @@
 func createAPIFingerprint(ctx android.SingletonContext) {
 	out := ApiFingerprintPath(ctx)
 
-	rule := android.NewRuleBuilder()
+	rule := android.NewRuleBuilder(pctx, ctx)
 
 	rule.Command().
 		Text("rm -f").Output(out)
@@ -659,7 +659,7 @@
 			Output(out)
 	}
 
-	rule.Build(pctx, ctx, "api_fingerprint", "generate api_fingerprint.txt")
+	rule.Build("api_fingerprint", "generate api_fingerprint.txt")
 }
 
 func ApiFingerprintPath(ctx android.PathContext) android.OutputPath {
diff --git a/java/sdk_library.go b/java/sdk_library.go
index 32bc077..4e33d74 100644
--- a/java/sdk_library.go
+++ b/java/sdk_library.go
@@ -2176,12 +2176,12 @@
 	xmlContent := fmt.Sprintf(permissionsTemplate, libName, module.implPath(ctx))
 
 	module.outputFilePath = android.PathForModuleOut(ctx, libName+".xml").OutputPath
-	rule := android.NewRuleBuilder()
+	rule := android.NewRuleBuilder(pctx, ctx)
 	rule.Command().
 		Text("/bin/bash -c \"echo -e '" + xmlContent + "'\" > ").
 		Output(module.outputFilePath)
 
-	rule.Build(pctx, ctx, "java_sdk_xml", "Permission XML")
+	rule.Build("java_sdk_xml", "Permission XML")
 
 	module.installDirPath = android.PathForModuleInstall(ctx, "etc", module.SubDir())
 }
diff --git a/java/sdk_library_external.go b/java/sdk_library_external.go
new file mode 100644
index 0000000..2934936
--- /dev/null
+++ b/java/sdk_library_external.go
@@ -0,0 +1,109 @@
+// Copyright 2020 Google Inc. All rights reserved.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package java
+
+import (
+	"android/soong/android"
+)
+
+type partitionGroup int
+
+// Representation of partition group for checking inter-partition library dependencies.
+// Between system and system_ext, there are no restrictions of dependencies,
+// so we can treat these partitions as the same in terms of inter-partition dependency.
+// Same policy is applied between vendor and odm partiton.
+const (
+	partitionGroupNone partitionGroup = iota
+	// group for system, and system_ext partition
+	partitionGroupSystem
+	// group for vendor and odm partition
+	partitionGroupVendor
+	// product partition
+	partitionGroupProduct
+)
+
+func (g partitionGroup) String() string {
+	switch g {
+	case partitionGroupSystem:
+		return "system"
+	case partitionGroupVendor:
+		return "vendor"
+	case partitionGroupProduct:
+		return "product"
+	}
+
+	return ""
+}
+
+// Get partition group of java module that can be used at inter-partition dependency check.
+// We currently have three groups
+//   (system, system_ext) => system partition group
+//   (vendor, odm) => vendor partition group
+//   (product) => product partition group
+func (j *Module) partitionGroup(ctx android.EarlyModuleContext) partitionGroup {
+	// system and system_ext partition can be treated as the same in terms of inter-partition dependency.
+	if j.Platform() || j.SystemExtSpecific() {
+		return partitionGroupSystem
+	}
+
+	// vendor and odm partition can be treated as the same in terms of inter-partition dependency.
+	if j.SocSpecific() || j.DeviceSpecific() {
+		return partitionGroupVendor
+	}
+
+	// product partition is independent.
+	if j.ProductSpecific() {
+		return partitionGroupProduct
+	}
+
+	panic("Cannot determine partition type")
+}
+
+func (j *Module) allowListedInterPartitionJavaLibrary(ctx android.EarlyModuleContext) bool {
+	return inList(j.Name(), ctx.Config().InterPartitionJavaLibraryAllowList())
+}
+
+type javaSdkLibraryEnforceContext interface {
+	Name() string
+	allowListedInterPartitionJavaLibrary(ctx android.EarlyModuleContext) bool
+	partitionGroup(ctx android.EarlyModuleContext) partitionGroup
+}
+
+var _ javaSdkLibraryEnforceContext = (*Module)(nil)
+
+func (j *Module) checkPartitionsForJavaDependency(ctx android.EarlyModuleContext, propName string, dep javaSdkLibraryEnforceContext) {
+	if dep.allowListedInterPartitionJavaLibrary(ctx) {
+		return
+	}
+
+	// If product interface is not enforced, skip check between system and product partition.
+	// But still need to check between product and vendor partition because product interface flag
+	// just represents enforcement between product and system, and vendor interface enforcement
+	// that is enforced here by precondition is representing enforcement between vendor and other partitions.
+	if !ctx.Config().EnforceProductPartitionInterface() {
+		productToSystem := j.partitionGroup(ctx) == partitionGroupProduct && dep.partitionGroup(ctx) == partitionGroupSystem
+		systemToProduct := j.partitionGroup(ctx) == partitionGroupSystem && dep.partitionGroup(ctx) == partitionGroupProduct
+
+		if productToSystem || systemToProduct {
+			return
+		}
+	}
+
+	// If module and dependency library is inter-partition
+	if j.partitionGroup(ctx) != dep.partitionGroup(ctx) {
+		errorFormat := "dependency on java_library (%q) is not allowed across the partitions (%s -> %s), use java_sdk_library instead"
+		ctx.PropertyErrorf(propName, errorFormat, dep.Name(), j.partitionGroup(ctx), dep.partitionGroup(ctx))
+	}
+}
diff --git a/linkerconfig/linkerconfig.go b/linkerconfig/linkerconfig.go
index 623c9dd..d538ce4 100644
--- a/linkerconfig/linkerconfig.go
+++ b/linkerconfig/linkerconfig.go
@@ -68,13 +68,13 @@
 	inputFile := android.PathForModuleSrc(ctx, android.String(l.properties.Src))
 	l.outputFilePath = android.PathForModuleOut(ctx, "linker.config.pb").OutputPath
 	l.installDirPath = android.PathForModuleInstall(ctx, "etc")
-	linkerConfigRule := android.NewRuleBuilder()
+	linkerConfigRule := android.NewRuleBuilder(pctx, ctx)
 	linkerConfigRule.Command().
-		BuiltTool(ctx, "conv_linker_config").
+		BuiltTool("conv_linker_config").
 		Flag("proto").
 		FlagWithInput("-s ", inputFile).
 		FlagWithOutput("-o ", l.outputFilePath)
-	linkerConfigRule.Build(pctx, ctx, "conv_linker_config",
+	linkerConfigRule.Build("conv_linker_config",
 		"Generate linker config protobuf "+l.outputFilePath.String())
 
 	if proptools.BoolDefault(l.properties.Installable, true) {
diff --git a/python/proto.go b/python/proto.go
index b71e047..53ebb58 100644
--- a/python/proto.go
+++ b/python/proto.go
@@ -24,17 +24,17 @@
 	outDir := srcsZipFile.ReplaceExtension(ctx, "tmp")
 	depFile := srcsZipFile.ReplaceExtension(ctx, "srcszip.d")
 
-	rule := android.NewRuleBuilder()
+	rule := android.NewRuleBuilder(pctx, ctx)
 
 	rule.Command().Text("rm -rf").Flag(outDir.String())
 	rule.Command().Text("mkdir -p").Flag(outDir.String())
 
-	android.ProtoRule(ctx, rule, protoFile, flags, flags.Deps, outDir, depFile, nil)
+	android.ProtoRule(rule, protoFile, flags, flags.Deps, outDir, depFile, nil)
 
 	// Proto generated python files have an unknown package name in the path, so package the entire output directory
 	// into a srcszip.
 	zipCmd := rule.Command().
-		BuiltTool(ctx, "soong_zip").
+		BuiltTool("soong_zip").
 		FlagWithOutput("-o ", srcsZipFile)
 	if pkgPath != "" {
 		zipCmd.FlagWithArg("-P ", pkgPath)
@@ -44,7 +44,7 @@
 
 	rule.Command().Text("rm -rf").Flag(outDir.String())
 
-	rule.Build(pctx, ctx, "protoc_"+protoFile.Rel(), "protoc "+protoFile.Rel())
+	rule.Build("protoc_"+protoFile.Rel(), "protoc "+protoFile.Rel())
 
 	return srcsZipFile
 }
diff --git a/rust/protobuf.go b/rust/protobuf.go
index 235b4ad..0e79089 100644
--- a/rust/protobuf.go
+++ b/rust/protobuf.go
@@ -93,7 +93,7 @@
 	// stemFile must be first here as the first path in BaseSourceProvider.OutputFiles is the library entry-point.
 	outputs := android.WritablePaths{stemFile}
 
-	rule := android.NewRuleBuilder()
+	rule := android.NewRuleBuilder(pctx, ctx)
 	for _, protoFile := range protoFiles {
 		protoName := strings.TrimSuffix(protoFile.Base(), ".proto")
 		protoNames = append(protoNames, protoName)
@@ -108,7 +108,7 @@
 
 		depFile := android.PathForModuleOut(ctx, protoName+".d")
 
-		android.ProtoRule(ctx, rule, protoFile, protoFlags, protoFlags.Deps, outDir, depFile, ruleOutputs)
+		android.ProtoRule(rule, protoFile, protoFlags, protoFlags.Deps, outDir, depFile, ruleOutputs)
 		outputs = append(outputs, ruleOutputs...)
 	}
 
@@ -117,7 +117,7 @@
 		Text("printf '" + proto.genModFileContents(ctx, protoNames) + "' >").
 		Output(stemFile)
 
-	rule.Build(pctx, ctx, "protoc_"+ctx.ModuleName(), "protoc "+ctx.ModuleName())
+	rule.Build("protoc_"+ctx.ModuleName(), "protoc "+ctx.ModuleName())
 
 	proto.BaseSourceProvider.OutputFiles = outputs.Paths()
 
diff --git a/scripts/conv_linker_config.py b/scripts/conv_linker_config.py
index fca71ad..22fe9f6 100644
--- a/scripts/conv_linker_config.py
+++ b/scripts/conv_linker_config.py
@@ -64,6 +64,21 @@
     f.write(pb.SerializeToString())
 
 
+def Append(args):
+  pb = linker_config_pb2.LinkerConfig()
+  with open(args.source, 'rb') as f:
+    pb.ParseFromString(f.read())
+
+  if getattr(type(pb), args.key).DESCRIPTOR.label == FieldDescriptor.LABEL_REPEATED:
+    for value in args.value.split():
+      getattr(pb, args.key).append(value)
+  else:
+    setattr(pb, args.key, args.value)
+
+  with open(args.output, 'wb') as f:
+    f.write(pb.SerializeToString())
+
+
 def GetArgParser():
   parser = argparse.ArgumentParser()
   subparsers = parser.add_subparsers()
@@ -120,6 +135,32 @@
       help='Path of the system image.')
   system_provide_libs.set_defaults(func=SystemProvide)
 
+  append = subparsers.add_parser(
+      'append', help='Append value(s) to given key.')
+  append.add_argument(
+      '-s',
+      '--source',
+      required=True,
+      type=str,
+      help='Source linker configuration file in protobuf.')
+  append.add_argument(
+      '-o',
+      '--output',
+      required=True,
+      type=str,
+      help='Target linker configuration file to write in protobuf.')
+  append.add_argument(
+      '--key',
+      required=True,
+      type=str,
+      help='.')
+  append.add_argument(
+      '--value',
+      required=True,
+      type=str,
+      help='Values of the libraries to append. If there are more than one it should be separated by empty space')
+  append.set_defaults(func=Append)
+
   return parser
 
 
diff --git a/scripts/gen_ndk_usedby_apex.sh b/scripts/gen_ndk_usedby_apex.sh
new file mode 100755
index 0000000..f143161
--- /dev/null
+++ b/scripts/gen_ndk_usedby_apex.sh
@@ -0,0 +1,72 @@
+#!/bin/bash -e
+
+# Copyright 2020 Google Inc. All rights reserved.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+# Generates NDK API txt file used by Mainline modules. NDK APIs would have value
+# "UND" in Ndx column and have suffix "@LIB_NAME" in Name column.
+# For example, current line llvm-readelf output is:
+# 1: 00000000     0     FUNC      GLOBAL  DEFAULT   UND   dlopen@LIBC
+# After the parse function below "dlopen" would be write to the output file.
+printHelp() {
+    echo "**************************** Usage Instructions ****************************"
+    echo "This script is used to generate the Mainline modules used-by NDK symbols."
+    echo ""
+    echo "To run this script use: ./ndk_usedby_module.sh \$BINARY_IMAGE_DIRECTORY \$BINARY_LLVM_PATH \$OUTPUT_FILE_PATH"
+    echo "For example: If all the module image files that you would like to run is under directory '/myModule' and output write to /myModule.txt then the command would be:"
+    echo "./ndk_usedby_module.sh /myModule \$BINARY_LLVM_PATH /myModule.txt"
+}
+
+parseReadelfOutput() {
+  while IFS= read -r line
+  do
+      if [[ $line = *FUNC*GLOBAL*UND*@* ]] ;
+      then
+          echo "$line" | sed -r 's/.*UND (.*)@.*/\1/g' >> "$2"
+      fi
+  done < "$1"
+  echo "" >> "$2"
+}
+
+unzipJarAndApk() {
+  tmpUnzippedDir="$1"/tmpUnzipped
+  [[ -e "$tmpUnzippedDir" ]] && rm -rf "$tmpUnzippedDir"
+  mkdir -p "$tmpUnzippedDir"
+  find "$1" -name "*.jar" -exec unzip -o {} -d "$tmpUnzippedDir" \;
+  find "$1" -name "*.apk" -exec unzip -o {} -d "$tmpUnzippedDir" \;
+  find "$tmpUnzippedDir" -name "*.MF" -exec rm {} \;
+}
+
+lookForExecFile() {
+  dir="$1"
+  readelf="$2"
+  find "$dir" -type f -name "*.so"  -exec "$2" --dyn-symbols {} >> "$dir"/../tmpReadelf.txt \;
+  find "$dir" -type f -perm /111 ! -name "*.so"  -exec "$2" --dyn-symbols {} >> "$dir"/../tmpReadelf.txt \;
+}
+
+if [[ "$1" == "help" ]]
+then
+  printHelp
+elif [[ "$#" -ne 3 ]]
+then
+  echo "Wrong argument length. Expecting 3 argument representing image file directory, llvm-readelf tool path, output path."
+else
+  unzipJarAndApk "$1"
+  lookForExecFile "$1" "$2"
+  tmpReadelfOutput="$1/../tmpReadelf.txt"
+  [[ -e "$3" ]] && rm "$3"
+  parseReadelfOutput "$tmpReadelfOutput" "$3"
+  [[ -e "$tmpReadelfOutput" ]] && rm "$tmpReadelfOutput"
+  rm -rf "$1/tmpUnzipped"
+fi
\ No newline at end of file
diff --git a/sdk/update.go b/sdk/update.go
index ba63542..377aaae 100644
--- a/sdk/update.go
+++ b/sdk/update.go
@@ -92,7 +92,7 @@
 }
 
 func (gf *generatedFile) build(pctx android.PackageContext, ctx android.BuilderContext, implicits android.Paths) {
-	rb := android.NewRuleBuilder()
+	rb := android.NewRuleBuilder(pctx, ctx)
 
 	content := gf.content.String()
 
@@ -108,7 +108,7 @@
 		Text("| sed 's/\\\\n/\\n/g' >").Output(gf.path)
 	rb.Command().
 		Text("chmod a+x").Output(gf.path)
-	rb.Build(pctx, ctx, gf.path.Base(), "Build "+gf.path.Base())
+	rb.Build(gf.path.Base(), "Build "+gf.path.Base())
 }
 
 // Collect all the members.
diff --git a/sysprop/sysprop_library.go b/sysprop/sysprop_library.go
index 828d1cf..6a53414 100644
--- a/sysprop/sysprop_library.go
+++ b/sysprop/sysprop_library.go
@@ -247,16 +247,16 @@
 	m.latestApiFile = android.PathForSource(ctx, ctx.ModuleDir(), "api", baseModuleName+"-latest.txt")
 
 	// dump API rule
-	rule := android.NewRuleBuilder()
+	rule := android.NewRuleBuilder(pctx, ctx)
 	m.dumpedApiFile = android.PathForModuleOut(ctx, "api-dump.txt")
 	rule.Command().
-		BuiltTool(ctx, "sysprop_api_dump").
+		BuiltTool("sysprop_api_dump").
 		Output(m.dumpedApiFile).
 		Inputs(android.PathsForModuleSrc(ctx, m.properties.Srcs))
-	rule.Build(pctx, ctx, baseModuleName+"_api_dump", baseModuleName+" api dump")
+	rule.Build(baseModuleName+"_api_dump", baseModuleName+" api dump")
 
 	// check API rule
-	rule = android.NewRuleBuilder()
+	rule = android.NewRuleBuilder(pctx, ctx)
 
 	// 1. compares current.txt to api-dump.txt
 	// current.txt should be identical to api-dump.txt.
@@ -284,7 +284,7 @@
 
 	rule.Command().
 		Text("( ").
-		BuiltTool(ctx, "sysprop_api_checker").
+		BuiltTool("sysprop_api_checker").
 		Input(m.latestApiFile).
 		Input(m.currentApiFile).
 		Text(" || ( echo").Flag("-e").
@@ -297,7 +297,7 @@
 		Text("touch").
 		Output(m.checkApiFileTimeStamp)
 
-	rule.Build(pctx, ctx, baseModuleName+"_check_api", baseModuleName+" check api")
+	rule.Build(baseModuleName+"_check_api", baseModuleName+" check api")
 }
 
 func (m *syspropLibrary) AndroidMk() android.AndroidMkData {
diff --git a/ui/build/build.go b/ui/build/build.go
index cfd0b83..e8f0fc4 100644
--- a/ui/build/build.go
+++ b/ui/build/build.go
@@ -28,7 +28,7 @@
 func SetupOutDir(ctx Context, config Config) {
 	ensureEmptyFileExists(ctx, filepath.Join(config.OutDir(), "Android.mk"))
 	ensureEmptyFileExists(ctx, filepath.Join(config.OutDir(), "CleanSpec.mk"))
-	if !config.SkipMake() {
+	if !config.SkipKati() {
 		// Run soong_build with Kati for a hybrid build, e.g. running the
 		// AndroidMk singleton and postinstall commands. Communicate this to
 		// soong_build by writing an empty .soong.kati_enabled marker file in the
@@ -44,7 +44,7 @@
 	ensureEmptyFileExists(ctx, filepath.Join(config.OutDir(), ".out-dir"))
 
 	if buildDateTimeFile, ok := config.environ.Get("BUILD_DATETIME_FILE"); ok {
-		err := ioutil.WriteFile(buildDateTimeFile, []byte(config.buildDateTime), 0777)
+		err := ioutil.WriteFile(buildDateTimeFile, []byte(config.buildDateTime), 0666) // a+rw
 		if err != nil {
 			ctx.Fatalln("Failed to write BUILD_DATETIME to file:", err)
 		}
@@ -67,8 +67,8 @@
 `))
 
 func createCombinedBuildNinjaFile(ctx Context, config Config) {
-	// If we're in SkipMake mode, skip creating this file if it already exists
-	if config.SkipMake() {
+	// If we're in SkipKati mode, skip creating this file if it already exists
+	if config.SkipKati() {
 		if _, err := os.Stat(config.CombinedNinjaFile()); err == nil || !os.IsNotExist(err) {
 			return
 		}
@@ -85,6 +85,7 @@
 	}
 }
 
+// These are bitmasks which can be used to check whether various flags are set e.g. whether to use Bazel.
 const (
 	BuildNone          = iota
 	BuildProductConfig = 1 << iota
@@ -97,6 +98,7 @@
 	BuildAllWithBazel  = BuildProductConfig | BuildSoong | BuildKati | BuildBazel
 )
 
+// checkProblematicFiles fails the build if existing Android.mk or CleanSpec.mk files are found at the root of the tree.
 func checkProblematicFiles(ctx Context) {
 	files := []string{"Android.mk", "CleanSpec.mk"}
 	for _, file := range files {
@@ -108,6 +110,7 @@
 	}
 }
 
+// checkCaseSensitivity issues a warning if a case-insensitive file system is being used.
 func checkCaseSensitivity(ctx Context, config Config) {
 	outDir := config.OutDir()
 	lowerCase := filepath.Join(outDir, "casecheck.txt")
@@ -115,13 +118,11 @@
 	lowerData := "a"
 	upperData := "B"
 
-	err := ioutil.WriteFile(lowerCase, []byte(lowerData), 0777)
-	if err != nil {
+	if err := ioutil.WriteFile(lowerCase, []byte(lowerData), 0666); err != nil { // a+rw
 		ctx.Fatalln("Failed to check case sensitivity:", err)
 	}
 
-	err = ioutil.WriteFile(upperCase, []byte(upperData), 0777)
-	if err != nil {
+	if err := ioutil.WriteFile(upperCase, []byte(upperData), 0666); err != nil { // a+rw
 		ctx.Fatalln("Failed to check case sensitivity:", err)
 	}
 
@@ -139,18 +140,15 @@
 	}
 }
 
-func help(ctx Context, config Config, what int) {
+// help prints a help/usage message, via the build/make/help.sh script.
+func help(ctx Context, config Config) {
 	cmd := Command(ctx, config, "help.sh", "build/make/help.sh")
 	cmd.Sandbox = dumpvarsSandbox
 	cmd.RunAndPrintOrFatal()
 }
 
-// Build the tree. The 'what' argument can be used to chose which components of
-// the build to run.
-func Build(ctx Context, config Config, what int) {
-	ctx.Verboseln("Starting build with args:", config.Arguments())
-	ctx.Verboseln("Environment:", config.Environment().Environ())
-
+// checkRAM warns if there probably isn't enough RAM to complete a build.
+func checkRAM(ctx Context, config Config) {
 	if totalRAM := config.TotalRAM(); totalRAM != 0 {
 		ram := float32(totalRAM) / (1024 * 1024 * 1024)
 		ctx.Verbosef("Total RAM: %.3vGB", ram)
@@ -166,24 +164,24 @@
 			ctx.Println("-j value.")
 			ctx.Println("************************************************************")
 		} else if ram <= float32(config.Parallel()) {
+			// Want at least 1GB of RAM per job.
 			ctx.Printf("Warning: high -j%d count compared to %.3vGB of RAM", config.Parallel(), ram)
 			ctx.Println("If you run into segfaults or other errors, try a lower -j value")
 		}
 	}
+}
+
+// Build the tree. The 'what' argument can be used to chose which components of
+// the build to run, via checking various bitmasks.
+func Build(ctx Context, config Config, what int) {
+	ctx.Verboseln("Starting build with args:", config.Arguments())
+	ctx.Verboseln("Environment:", config.Environment().Environ())
 
 	ctx.BeginTrace(metrics.Total, "total")
 	defer ctx.EndTrace()
 
-	if config.SkipMake() {
-		ctx.Verboseln("Skipping Make/Kati as requested")
-		what = what & (BuildSoong | BuildNinja)
-	}
-
 	if inList("help", config.Arguments()) {
-		help(ctx, config, what)
-		return
-	} else if inList("clean", config.Arguments()) || inList("clobber", config.Arguments()) {
-		clean(ctx, config)
+		help(ctx, config)
 		return
 	}
 
@@ -191,16 +189,35 @@
 	buildLock := BecomeSingletonOrFail(ctx, config)
 	defer buildLock.Unlock()
 
+	if inList("clean", config.Arguments()) || inList("clobber", config.Arguments()) {
+		clean(ctx, config)
+		return
+	}
+
+	// checkProblematicFiles aborts the build if Android.mk or CleanSpec.mk are found at the root of the tree.
 	checkProblematicFiles(ctx)
 
+	checkRAM(ctx, config)
+
 	SetupOutDir(ctx, config)
 
+	// checkCaseSensitivity issues a warning if a case-insensitive file system is being used.
 	checkCaseSensitivity(ctx, config)
 
 	ensureEmptyDirectoriesExist(ctx, config.TempDir())
 
 	SetupPath(ctx, config)
 
+	if config.SkipConfig() {
+		ctx.Verboseln("Skipping Config as requested")
+		what = what &^ BuildProductConfig
+	}
+
+	if config.SkipKati() {
+		ctx.Verboseln("Skipping Kati as requested")
+		what = what &^ BuildKati
+	}
+
 	if config.StartGoma() {
 		// Ensure start Goma compiler_proxy
 		startGoma(ctx, config)
@@ -216,12 +233,16 @@
 		runMakeProductConfig(ctx, config)
 	}
 
+	// Everything below here depends on product config.
+
 	if inList("installclean", config.Arguments()) ||
 		inList("install-clean", config.Arguments()) {
 		installClean(ctx, config)
 		ctx.Println("Deleted images and staging directories.")
 		return
-	} else if inList("dataclean", config.Arguments()) ||
+	}
+
+	if inList("dataclean", config.Arguments()) ||
 		inList("data-clean", config.Arguments()) {
 		dataClean(ctx, config)
 		ctx.Println("Deleted data files.")
@@ -240,7 +261,7 @@
 		runKatiBuild(ctx, config)
 		runKatiPackage(ctx, config)
 
-		ioutil.WriteFile(config.LastKatiSuffixFile(), []byte(config.KatiSuffix()), 0777)
+		ioutil.WriteFile(config.LastKatiSuffixFile(), []byte(config.KatiSuffix()), 0666) // a+rw
 	} else {
 		// Load last Kati Suffix if it exists
 		if katiSuffix, err := ioutil.ReadFile(config.LastKatiSuffixFile()); err == nil {
@@ -259,7 +280,7 @@
 	}
 
 	if what&BuildNinja != 0 {
-		if !config.SkipMake() {
+		if what&BuildKati != 0 {
 			installCleanIfNecessary(ctx, config)
 		}
 
@@ -267,6 +288,7 @@
 		runNinja(ctx, config)
 	}
 
+	// Currently, using Bazel requires Kati and Soong to run first, so check whether to run Bazel last.
 	if what&BuildBazel != 0 {
 		runBazel(ctx, config)
 	}
@@ -282,14 +304,11 @@
 	subDir := filepath.Join(subDirs...)
 	destDir := filepath.Join(config.DistDir(), "soong_ui", subDir)
 
-	err := os.MkdirAll(destDir, 0777)
-	if err != nil {
+	if err := os.MkdirAll(destDir, 0777); err != nil { // a+rwx
 		ctx.Printf("failed to mkdir %s: %s", destDir, err.Error())
-
 	}
 
-	err = gzipFileToDir(src, destDir)
-	if err != nil {
+	if err := gzipFileToDir(src, destDir); err != nil {
 		ctx.Printf("failed to dist %s: %s", filepath.Base(src), err.Error())
 	}
 }
@@ -304,14 +323,11 @@
 	subDir := filepath.Join(subDirs...)
 	destDir := filepath.Join(config.DistDir(), "soong_ui", subDir)
 
-	err := os.MkdirAll(destDir, 0777)
-	if err != nil {
+	if err := os.MkdirAll(destDir, 0777); err != nil { // a+rwx
 		ctx.Printf("failed to mkdir %s: %s", destDir, err.Error())
-
 	}
 
-	_, err = copyFile(src, filepath.Join(destDir, filepath.Base(src)))
-	if err != nil {
+	if _, err := copyFile(src, filepath.Join(destDir, filepath.Base(src))); err != nil {
 		ctx.Printf("failed to dist %s: %s", filepath.Base(src), err.Error())
 	}
 }
diff --git a/ui/build/config.go b/ui/build/config.go
index 229bd5c..c9911f3 100644
--- a/ui/build/config.go
+++ b/ui/build/config.go
@@ -46,7 +46,8 @@
 	verbose        bool
 	checkbuild     bool
 	dist           bool
-	skipMake       bool
+	skipConfig     bool
+	skipKati       bool
 	skipSoongTests bool
 
 	// From the product config
@@ -536,7 +537,10 @@
 		} else if arg == "showcommands" {
 			c.verbose = true
 		} else if arg == "--skip-make" {
-			c.skipMake = true
+			c.skipConfig = true
+			c.skipKati = true
+		} else if arg == "--skip-kati" {
+			c.skipKati = true
 		} else if arg == "--skip-soong-tests" {
 			c.skipSoongTests = true
 		} else if len(arg) > 0 && arg[0] == '-' {
@@ -697,7 +701,7 @@
 }
 
 func (c *configImpl) NinjaArgs() []string {
-	if c.skipMake {
+	if c.skipKati {
 		return c.arguments
 	}
 	return c.ninjaArgs
@@ -740,8 +744,12 @@
 	return c.verbose
 }
 
-func (c *configImpl) SkipMake() bool {
-	return c.skipMake
+func (c *configImpl) SkipKati() bool {
+	return c.skipKati
+}
+
+func (c *configImpl) SkipConfig() bool {
+	return c.skipConfig
 }
 
 func (c *configImpl) TargetProduct() string {
diff --git a/ui/build/soong.go b/ui/build/soong.go
index bb5cbf0..08c2ee1 100644
--- a/ui/build/soong.go
+++ b/ui/build/soong.go
@@ -30,16 +30,33 @@
 	"android/soong/ui/status"
 )
 
+// This uses Android.bp files and various tools to generate <builddir>/build.ninja.
+//
+// However, the execution of <builddir>/build.ninja happens later in build/soong/ui/build/build.go#Build()
+//
+// We want to rely on as few prebuilts as possible, so there is some bootstrapping here.
+//
+// "Microfactory" is a tool for compiling Go code. We use it to build two other tools:
+// - minibp, used to generate build.ninja files. This is really build/blueprint/bootstrap/command.go#Main()
+// - bpglob, used during incremental builds to identify files in a glob that have changed
+//
+// In reality, several build.ninja files are generated and/or used during the bootstrapping and build process.
+// See build/blueprint/bootstrap/doc.go for more information.
+//
 func runSoong(ctx Context, config Config) {
 	ctx.BeginTrace(metrics.RunSoong, "soong")
 	defer ctx.EndTrace()
 
+	// Use an anonymous inline function for tracing purposes (this pattern is used several times below).
 	func() {
 		ctx.BeginTrace(metrics.RunSoong, "blueprint bootstrap")
 		defer ctx.EndTrace()
 
+		// Use validations to depend on tests.
 		args := []string{"-n"}
+
 		if !config.skipSoongTests {
+			// Run tests.
 			args = append(args, "-t")
 		}
 
@@ -145,7 +162,10 @@
 		cmd.RunAndStreamOrFatal()
 	}
 
+	// This build generates .bootstrap/build.ninja, which is used in the next step.
 	ninja("minibootstrap", ".minibootstrap/build.ninja")
+
+	// This build generates <builddir>/build.ninja, which is used later by build/soong/ui/build/build.go#Build().
 	ninja("bootstrap", ".bootstrap/build.ninja")
 
 	soongBuildMetrics := loadSoongBuildMetrics(ctx, config)
@@ -153,7 +173,7 @@
 
 	distGzipFile(ctx, config, config.SoongNinjaFile(), "soong")
 
-	if !config.SkipMake() {
+	if !config.SkipKati() {
 		distGzipFile(ctx, config, config.SoongAndroidMk(), "soong")
 		distGzipFile(ctx, config, config.SoongMakeVarsMk(), "soong")
 	}