diff --git a/android/apex.go b/android/apex.go
index 8759905..c0acada 100644
--- a/android/apex.go
+++ b/android/apex.go
@@ -16,6 +16,7 @@
 
 import (
 	"fmt"
+	"slices"
 	"sort"
 	"strconv"
 	"strings"
@@ -108,7 +109,7 @@
 // are configured to have the same alias variation named apex29. Whether platform APIs is allowed
 // or not also matters; if two APEXes don't have the same allowance, they get different names and
 // thus wouldn't be merged.
-func (i ApexInfo) mergedName(ctx PathContext) string {
+func (i ApexInfo) mergedName() string {
 	name := "apex" + strconv.Itoa(i.MinSdkVersion.FinalOrFutureInt())
 	return name
 }
@@ -543,17 +544,10 @@
 	return true
 }
 
-type byApexName []ApexInfo
-
-func (a byApexName) Len() int           { return len(a) }
-func (a byApexName) Swap(i, j int)      { a[i], a[j] = a[j], a[i] }
-func (a byApexName) Less(i, j int) bool { return a[i].ApexVariationName < a[j].ApexVariationName }
-
 // mergeApexVariations deduplicates apex variations that would build identically into a common
 // variation. It returns the reduced list of variations and a list of aliases from the original
 // variation names to the new variation names.
-func mergeApexVariations(ctx PathContext, apexInfos []ApexInfo) (merged []ApexInfo, aliases [][2]string) {
-	sort.Sort(byApexName(apexInfos))
+func mergeApexVariations(apexInfos []ApexInfo) (merged []ApexInfo, aliases [][2]string) {
 	seen := make(map[string]int)
 	for _, apexInfo := range apexInfos {
 		// If this is for a prebuilt apex then use the actual name of the apex variation to prevent this
@@ -567,7 +561,7 @@
 		// this one into it, otherwise create a new merged ApexInfo from this one and save it away so
 		// other ApexInfo instances can be merged into it.
 		variantName := apexInfo.ApexVariationName
-		mergedName := apexInfo.mergedName(ctx)
+		mergedName := apexInfo.mergedName()
 		if index, exists := seen[mergedName]; exists {
 			// Variants having the same mergedName are deduped
 			merged[index].InApexVariants = append(merged[index].InApexVariants, variantName)
@@ -606,18 +600,20 @@
 	// TODO(jiyong): is this the right place?
 	base.checkApexAvailableProperty(mctx)
 
-	var apexInfos []ApexInfo
-	var aliases [][2]string
-	if !mctx.Module().(ApexModule).UniqueApexVariations() && !base.ApexProperties.UniqueApexVariationsForDeps {
-		apexInfos, aliases = mergeApexVariations(mctx, base.apexInfos)
-	} else {
-		apexInfos = base.apexInfos
-	}
+	apexInfos := base.apexInfos
 	// base.apexInfos is only needed to propagate the list of apexes from apexInfoMutator to
 	// apexMutator. It is no longer accurate after mergeApexVariations, and won't be copied to
 	// all but the first created variant. Clear it so it doesn't accidentally get used later.
 	base.apexInfos = nil
-	sort.Sort(byApexName(apexInfos))
+
+	slices.SortFunc(apexInfos, func(a, b ApexInfo) int {
+		return strings.Compare(a.ApexVariationName, b.ApexVariationName)
+	})
+
+	var aliases [][2]string
+	if !mctx.Module().(ApexModule).UniqueApexVariations() && !base.ApexProperties.UniqueApexVariationsForDeps {
+		apexInfos, aliases = mergeApexVariations(apexInfos)
+	}
 
 	var inApex ApexMembership
 	for _, a := range apexInfos {
diff --git a/android/apex_test.go b/android/apex_test.go
index ddc730d..347bf7d 100644
--- a/android/apex_test.go
+++ b/android/apex_test.go
@@ -33,10 +33,22 @@
 		{
 			name: "single",
 			in: []ApexInfo{
-				{"foo", FutureApiLevel, false, false, []string{"foo"}, []string{"foo"}, nil, NotForPrebuiltApex, nil},
+				{
+					ApexVariationName: "foo",
+					MinSdkVersion:     FutureApiLevel,
+					InApexVariants:    []string{"foo"},
+					InApexModules:     []string{"foo"},
+					ForPrebuiltApex:   NotForPrebuiltApex,
+				},
 			},
 			wantMerged: []ApexInfo{
-				{"apex10000", FutureApiLevel, false, false, []string{"foo"}, []string{"foo"}, nil, NotForPrebuiltApex, nil},
+				{
+					ApexVariationName: "apex10000",
+					MinSdkVersion:     FutureApiLevel,
+					InApexVariants:    []string{"foo"},
+					InApexModules:     []string{"foo"},
+					ForPrebuiltApex:   NotForPrebuiltApex,
+				},
 			},
 			wantAliases: [][2]string{
 				{"foo", "apex10000"},
@@ -45,98 +57,231 @@
 		{
 			name: "merge",
 			in: []ApexInfo{
-				{"foo", FutureApiLevel, false, false, []string{"foo"}, []string{"foo"}, nil, NotForPrebuiltApex, nil},
-				{"bar", FutureApiLevel, false, false, []string{"bar"}, []string{"bar"}, nil, NotForPrebuiltApex, nil},
+				{
+					ApexVariationName: "foo",
+					MinSdkVersion:     FutureApiLevel,
+					InApexVariants:    []string{"foo"},
+					InApexModules:     []string{"foo"},
+					ForPrebuiltApex:   NotForPrebuiltApex,
+				},
+				{
+					ApexVariationName: "bar",
+					MinSdkVersion:     FutureApiLevel,
+					InApexVariants:    []string{"bar"},
+					InApexModules:     []string{"bar"},
+					ForPrebuiltApex:   NotForPrebuiltApex,
+				},
 			},
 			wantMerged: []ApexInfo{
-				{"apex10000", FutureApiLevel, false, false, []string{"bar", "foo"}, []string{"bar", "foo"}, nil, false, nil}},
+				{
+					ApexVariationName: "apex10000",
+					MinSdkVersion:     FutureApiLevel,
+					InApexVariants:    []string{"foo", "bar"},
+					InApexModules:     []string{"foo", "bar"},
+				}},
 			wantAliases: [][2]string{
-				{"bar", "apex10000"},
 				{"foo", "apex10000"},
+				{"bar", "apex10000"},
 			},
 		},
 		{
 			name: "don't merge version",
 			in: []ApexInfo{
-				{"foo", FutureApiLevel, false, false, []string{"foo"}, []string{"foo"}, nil, NotForPrebuiltApex, nil},
-				{"bar", uncheckedFinalApiLevel(30), false, false, []string{"bar"}, []string{"bar"}, nil, NotForPrebuiltApex, nil},
+				{
+					ApexVariationName: "foo",
+					MinSdkVersion:     FutureApiLevel,
+					InApexVariants:    []string{"foo"},
+					InApexModules:     []string{"foo"},
+					ForPrebuiltApex:   NotForPrebuiltApex,
+				},
+				{
+					ApexVariationName: "bar",
+					MinSdkVersion:     uncheckedFinalApiLevel(30),
+					InApexVariants:    []string{"bar"},
+					InApexModules:     []string{"bar"},
+					ForPrebuiltApex:   NotForPrebuiltApex,
+				},
 			},
 			wantMerged: []ApexInfo{
-				{"apex30", uncheckedFinalApiLevel(30), false, false, []string{"bar"}, []string{"bar"}, nil, NotForPrebuiltApex, nil},
-				{"apex10000", FutureApiLevel, false, false, []string{"foo"}, []string{"foo"}, nil, NotForPrebuiltApex, nil},
+				{
+					ApexVariationName: "apex10000",
+					MinSdkVersion:     FutureApiLevel,
+					InApexVariants:    []string{"foo"},
+					InApexModules:     []string{"foo"},
+					ForPrebuiltApex:   NotForPrebuiltApex,
+				},
+				{
+					ApexVariationName: "apex30",
+					MinSdkVersion:     uncheckedFinalApiLevel(30),
+					InApexVariants:    []string{"bar"},
+					InApexModules:     []string{"bar"},
+					ForPrebuiltApex:   NotForPrebuiltApex,
+				},
 			},
 			wantAliases: [][2]string{
-				{"bar", "apex30"},
 				{"foo", "apex10000"},
+				{"bar", "apex30"},
 			},
 		},
 		{
 			name: "merge updatable",
 			in: []ApexInfo{
-				{"foo", FutureApiLevel, false, false, []string{"foo"}, []string{"foo"}, nil, NotForPrebuiltApex, nil},
-				{"bar", FutureApiLevel, true, false, []string{"bar"}, []string{"bar"}, nil, NotForPrebuiltApex, nil},
+				{
+					ApexVariationName: "foo",
+					MinSdkVersion:     FutureApiLevel,
+					InApexVariants:    []string{"foo"},
+					InApexModules:     []string{"foo"},
+					ForPrebuiltApex:   NotForPrebuiltApex,
+				},
+				{
+					ApexVariationName: "bar",
+					MinSdkVersion:     FutureApiLevel,
+					Updatable:         true,
+					InApexVariants:    []string{"bar"},
+					InApexModules:     []string{"bar"},
+					ForPrebuiltApex:   NotForPrebuiltApex,
+				},
 			},
 			wantMerged: []ApexInfo{
-				{"apex10000", FutureApiLevel, true, false, []string{"bar", "foo"}, []string{"bar", "foo"}, nil, NotForPrebuiltApex, nil},
+				{
+					ApexVariationName: "apex10000",
+					MinSdkVersion:     FutureApiLevel,
+					Updatable:         true,
+					InApexVariants:    []string{"foo", "bar"},
+					InApexModules:     []string{"foo", "bar"},
+					ForPrebuiltApex:   NotForPrebuiltApex,
+				},
 			},
 			wantAliases: [][2]string{
-				{"bar", "apex10000"},
 				{"foo", "apex10000"},
+				{"bar", "apex10000"},
 			},
 		},
 		{
 			name: "don't merge when for prebuilt_apex",
 			in: []ApexInfo{
-				{"foo", FutureApiLevel, false, false, []string{"foo"}, []string{"foo"}, nil, NotForPrebuiltApex, nil},
-				{"bar", FutureApiLevel, true, false, []string{"bar"}, []string{"bar"}, nil, NotForPrebuiltApex, nil},
+				{
+					ApexVariationName: "foo",
+					MinSdkVersion:     FutureApiLevel,
+					InApexVariants:    []string{"foo"},
+					InApexModules:     []string{"foo"},
+					ForPrebuiltApex:   NotForPrebuiltApex,
+				},
+				{
+					ApexVariationName: "bar",
+					MinSdkVersion:     FutureApiLevel,
+					Updatable:         true,
+					InApexVariants:    []string{"bar"},
+					InApexModules:     []string{"bar"},
+					ForPrebuiltApex:   NotForPrebuiltApex,
+				},
 				// This one should not be merged in with the others because it is for
 				// a prebuilt_apex.
-				{"baz", FutureApiLevel, true, false, []string{"baz"}, []string{"baz"}, nil, ForPrebuiltApex, nil},
+				{
+					ApexVariationName: "baz",
+					MinSdkVersion:     FutureApiLevel,
+					Updatable:         true,
+					InApexVariants:    []string{"baz"},
+					InApexModules:     []string{"baz"},
+					ForPrebuiltApex:   ForPrebuiltApex,
+				},
 			},
 			wantMerged: []ApexInfo{
-				{"apex10000", FutureApiLevel, true, false, []string{"bar", "foo"}, []string{"bar", "foo"}, nil, NotForPrebuiltApex, nil},
-				{"baz", FutureApiLevel, true, false, []string{"baz"}, []string{"baz"}, nil, ForPrebuiltApex, nil},
+				{
+					ApexVariationName: "apex10000",
+					MinSdkVersion:     FutureApiLevel,
+					Updatable:         true,
+					InApexVariants:    []string{"foo", "bar"},
+					InApexModules:     []string{"foo", "bar"},
+					ForPrebuiltApex:   NotForPrebuiltApex,
+				},
+				{
+					ApexVariationName: "baz",
+					MinSdkVersion:     FutureApiLevel,
+					Updatable:         true,
+					InApexVariants:    []string{"baz"},
+					InApexModules:     []string{"baz"},
+					ForPrebuiltApex:   ForPrebuiltApex,
+				},
 			},
 			wantAliases: [][2]string{
-				{"bar", "apex10000"},
 				{"foo", "apex10000"},
+				{"bar", "apex10000"},
 			},
 		},
 		{
 			name: "merge different UsePlatformApis but don't allow using platform api",
 			in: []ApexInfo{
-				{"foo", FutureApiLevel, false, false, []string{"foo"}, []string{"foo"}, nil, NotForPrebuiltApex, nil},
-				{"bar", FutureApiLevel, false, true, []string{"bar"}, []string{"bar"}, nil, NotForPrebuiltApex, nil},
+				{
+					ApexVariationName: "foo",
+					MinSdkVersion:     FutureApiLevel,
+					InApexVariants:    []string{"foo"},
+					InApexModules:     []string{"foo"},
+					ForPrebuiltApex:   NotForPrebuiltApex,
+				},
+				{
+					ApexVariationName: "bar",
+					MinSdkVersion:     FutureApiLevel,
+					UsePlatformApis:   true,
+					InApexVariants:    []string{"bar"},
+					InApexModules:     []string{"bar"},
+					ForPrebuiltApex:   NotForPrebuiltApex,
+				},
 			},
 			wantMerged: []ApexInfo{
-				{"apex10000", FutureApiLevel, false, false, []string{"bar", "foo"}, []string{"bar", "foo"}, nil, NotForPrebuiltApex, nil},
+				{
+					ApexVariationName: "apex10000",
+					MinSdkVersion:     FutureApiLevel,
+					InApexVariants:    []string{"foo", "bar"},
+					InApexModules:     []string{"foo", "bar"},
+					ForPrebuiltApex:   NotForPrebuiltApex,
+				},
 			},
 			wantAliases: [][2]string{
-				{"bar", "apex10000"},
 				{"foo", "apex10000"},
+				{"bar", "apex10000"},
 			},
 		},
 		{
 			name: "merge same UsePlatformApis and allow using platform api",
 			in: []ApexInfo{
-				{"foo", FutureApiLevel, false, true, []string{"foo"}, []string{"foo"}, nil, NotForPrebuiltApex, nil},
-				{"bar", FutureApiLevel, false, true, []string{"bar"}, []string{"bar"}, nil, NotForPrebuiltApex, nil},
+				{
+					ApexVariationName: "foo",
+					MinSdkVersion:     FutureApiLevel,
+					UsePlatformApis:   true,
+					InApexVariants:    []string{"foo"},
+					InApexModules:     []string{"foo"},
+					ForPrebuiltApex:   NotForPrebuiltApex,
+				},
+				{
+					ApexVariationName: "bar",
+					MinSdkVersion:     FutureApiLevel,
+					UsePlatformApis:   true,
+					InApexVariants:    []string{"bar"},
+					InApexModules:     []string{"bar"},
+					ForPrebuiltApex:   NotForPrebuiltApex,
+				},
 			},
 			wantMerged: []ApexInfo{
-				{"apex10000", FutureApiLevel, false, true, []string{"bar", "foo"}, []string{"bar", "foo"}, nil, NotForPrebuiltApex, nil},
+				{
+					ApexVariationName: "apex10000",
+					MinSdkVersion:     FutureApiLevel,
+					UsePlatformApis:   true,
+					InApexVariants:    []string{"foo", "bar"},
+					InApexModules:     []string{"foo", "bar"},
+					ForPrebuiltApex:   NotForPrebuiltApex,
+				},
 			},
 			wantAliases: [][2]string{
-				{"bar", "apex10000"},
 				{"foo", "apex10000"},
+				{"bar", "apex10000"},
 			},
 		},
 	}
 
 	for _, tt := range tests {
 		t.Run(tt.name, func(t *testing.T) {
-			config := TestConfig(t.TempDir(), nil, "", nil)
-			ctx := &configErrorWrapper{config: config}
-			gotMerged, gotAliases := mergeApexVariations(ctx, tt.in)
+			gotMerged, gotAliases := mergeApexVariations(tt.in)
 			if !reflect.DeepEqual(gotMerged, tt.wantMerged) {
 				t.Errorf("mergeApexVariations() gotMerged = %v, want %v", gotMerged, tt.wantMerged)
 			}
diff --git a/android/base_module_context.go b/android/base_module_context.go
index c4922f4..c5fe585 100644
--- a/android/base_module_context.go
+++ b/android/base_module_context.go
@@ -20,7 +20,7 @@
 	"strings"
 
 	"github.com/google/blueprint"
-	"github.com/google/blueprint/parser"
+	"github.com/google/blueprint/proptools"
 )
 
 // BaseModuleContext is the same as blueprint.BaseModuleContext except that Config() returns
@@ -219,7 +219,7 @@
 
 	// EvaluateConfiguration makes ModuleContext a valid proptools.ConfigurableEvaluator, so this context
 	// can be used to evaluate the final value of Configurable properties.
-	EvaluateConfiguration(parser.SelectType, string, string) (string, bool)
+	EvaluateConfiguration(condition proptools.ConfigurableCondition, property string) proptools.ConfigurableValue
 }
 
 type baseModuleContext struct {
@@ -577,6 +577,6 @@
 	return sb.String()
 }
 
-func (m *baseModuleContext) EvaluateConfiguration(ty parser.SelectType, property, condition string) (string, bool) {
-	return m.Module().ConfigurableEvaluator(m).EvaluateConfiguration(ty, property, condition)
+func (m *baseModuleContext) EvaluateConfiguration(condition proptools.ConfigurableCondition, property string) proptools.ConfigurableValue {
+	return m.Module().ConfigurableEvaluator(m).EvaluateConfiguration(condition, property)
 }
diff --git a/android/config.go b/android/config.go
index 11bd81b..75d135f 100644
--- a/android/config.go
+++ b/android/config.go
@@ -949,7 +949,11 @@
 }
 
 func (c *config) PlatformMinSupportedTargetSdkVersion() string {
-	return String(c.productVariables.Platform_min_supported_target_sdk_version)
+	var val, ok = c.productVariables.BuildFlags["RELEASE_PLATFORM_MIN_SUPPORTED_TARGET_SDK_VERSION"]
+	if !ok {
+		return ""
+	}
+	return val
 }
 
 func (c *config) PlatformBaseOS() string {
diff --git a/android/module.go b/android/module.go
index 89c4ddd..26261cc 100644
--- a/android/module.go
+++ b/android/module.go
@@ -29,7 +29,6 @@
 	"android/soong/bazel"
 
 	"github.com/google/blueprint"
-	"github.com/google/blueprint/parser"
 	"github.com/google/blueprint/proptools"
 )
 
@@ -2140,41 +2139,82 @@
 	e.ctx.OtherModulePropertyErrorf(e.m, property, fmt, args)
 }
 
-func (e configurationEvalutor) EvaluateConfiguration(ty parser.SelectType, property, condition string) (string, bool) {
+func (e configurationEvalutor) EvaluateConfiguration(condition proptools.ConfigurableCondition, property string) proptools.ConfigurableValue {
 	ctx := e.ctx
 	m := e.m
-	switch ty {
-	case parser.SelectTypeReleaseVariable:
-		if v, ok := ctx.Config().productVariables.BuildFlags[condition]; ok {
-			return v, true
+	switch condition.FunctionName {
+	case "release_variable":
+		if len(condition.Args) != 1 {
+			ctx.OtherModulePropertyErrorf(m, property, "release_variable requires 1 argument, found %d", len(condition.Args))
+			return proptools.ConfigurableValueUndefined()
 		}
-		return "", false
-	case parser.SelectTypeProductVariable:
+		if v, ok := ctx.Config().productVariables.BuildFlags[condition.Args[0]]; ok {
+			return proptools.ConfigurableValueString(v)
+		}
+		return proptools.ConfigurableValueUndefined()
+	case "product_variable":
 		// TODO(b/323382414): Might add these on a case-by-case basis
 		ctx.OtherModulePropertyErrorf(m, property, "TODO(b/323382414): Product variables are not yet supported in selects")
-		return "", false
-	case parser.SelectTypeSoongConfigVariable:
-		parts := strings.Split(condition, ":")
-		namespace := parts[0]
-		variable := parts[1]
+		return proptools.ConfigurableValueUndefined()
+	case "soong_config_variable":
+		if len(condition.Args) != 2 {
+			ctx.OtherModulePropertyErrorf(m, property, "soong_config_variable requires 2 arguments, found %d", len(condition.Args))
+			return proptools.ConfigurableValueUndefined()
+		}
+		namespace := condition.Args[0]
+		variable := condition.Args[1]
 		if n, ok := ctx.Config().productVariables.VendorVars[namespace]; ok {
 			if v, ok := n[variable]; ok {
-				return v, true
+				return proptools.ConfigurableValueString(v)
 			}
 		}
-		return "", false
-	case parser.SelectTypeVariant:
-		if condition == "arch" {
-			if !m.base().ArchReady() {
-				ctx.OtherModulePropertyErrorf(m, property, "A select on arch was attempted before the arch mutator ran")
-				return "", false
-			}
-			return m.base().Arch().ArchType.Name, true
+		return proptools.ConfigurableValueUndefined()
+	case "arch":
+		if len(condition.Args) != 0 {
+			ctx.OtherModulePropertyErrorf(m, property, "arch requires no arguments, found %d", len(condition.Args))
+			return proptools.ConfigurableValueUndefined()
 		}
-		ctx.OtherModulePropertyErrorf(m, property, "Unknown variant %s", condition)
-		return "", false
+		if !m.base().ArchReady() {
+			ctx.OtherModulePropertyErrorf(m, property, "A select on arch was attempted before the arch mutator ran")
+			return proptools.ConfigurableValueUndefined()
+		}
+		return proptools.ConfigurableValueString(m.base().Arch().ArchType.Name)
+	case "os":
+		if len(condition.Args) != 0 {
+			ctx.OtherModulePropertyErrorf(m, property, "os requires no arguments, found %d", len(condition.Args))
+			return proptools.ConfigurableValueUndefined()
+		}
+		// the arch mutator runs after the os mutator, we can just use this to enforce that os is ready.
+		if !m.base().ArchReady() {
+			ctx.OtherModulePropertyErrorf(m, property, "A select on os was attempted before the arch mutator ran (arch runs after os, we use it to lazily detect that os is ready)")
+			return proptools.ConfigurableValueUndefined()
+		}
+		return proptools.ConfigurableValueString(m.base().Os().Name)
+	case "boolean_var_for_testing":
+		// We currently don't have any other boolean variables (we should add support for typing
+		// the soong config variables), so add this fake one for testing the boolean select
+		// functionality.
+		if len(condition.Args) != 0 {
+			ctx.OtherModulePropertyErrorf(m, property, "boolean_var_for_testing requires 0 arguments, found %d", len(condition.Args))
+			return proptools.ConfigurableValueUndefined()
+		}
+
+		if n, ok := ctx.Config().productVariables.VendorVars["boolean_var"]; ok {
+			if v, ok := n["for_testing"]; ok {
+				switch v {
+				case "true":
+					return proptools.ConfigurableValueBool(true)
+				case "false":
+					return proptools.ConfigurableValueBool(false)
+				default:
+					ctx.OtherModulePropertyErrorf(m, property, "testing:my_boolean_var can only be true or false, found %q", v)
+				}
+			}
+		}
+		return proptools.ConfigurableValueUndefined()
 	default:
-		panic("Should be unreachable")
+		ctx.OtherModulePropertyErrorf(m, property, "Unknown select condition %s", condition.FunctionName)
+		return proptools.ConfigurableValueUndefined()
 	}
 }
 
diff --git a/android/mutator.go b/android/mutator.go
index 0ff4f48..75ba650 100644
--- a/android/mutator.go
+++ b/android/mutator.go
@@ -391,6 +391,7 @@
 
 type IncomingTransitionContext interface {
 	ArchModuleContext
+	ModuleProviderContext
 
 	// Module returns the target of the dependency edge for which the transition
 	// is being computed
@@ -404,6 +405,7 @@
 
 type OutgoingTransitionContext interface {
 	ArchModuleContext
+	ModuleProviderContext
 
 	// Module returns the target of the dependency edge for which the transition
 	// is being computed
@@ -505,6 +507,7 @@
 type androidTransitionMutator struct {
 	finalPhase bool
 	mutator    TransitionMutator
+	name       string
 }
 
 func (a *androidTransitionMutator) Split(ctx blueprint.BaseModuleContext) []string {
@@ -537,6 +540,10 @@
 	return DeviceConfig{c.bp.Config().(Config).deviceConfig}
 }
 
+func (c *outgoingTransitionContextImpl) provider(provider blueprint.AnyProviderKey) (any, bool) {
+	return c.bp.Provider(provider)
+}
+
 func (a *androidTransitionMutator) OutgoingTransition(bpctx blueprint.OutgoingTransitionContext, sourceVariation string) string {
 	if m, ok := bpctx.Module().(Module); ok {
 		ctx := outgoingTransitionContextPool.Get().(*outgoingTransitionContextImpl)
@@ -568,6 +575,10 @@
 	return DeviceConfig{c.bp.Config().(Config).deviceConfig}
 }
 
+func (c *incomingTransitionContextImpl) provider(provider blueprint.AnyProviderKey) (any, bool) {
+	return c.bp.Provider(provider)
+}
+
 func (a *androidTransitionMutator) IncomingTransition(bpctx blueprint.IncomingTransitionContext, incomingVariation string) string {
 	if m, ok := bpctx.Module().(Module); ok {
 		ctx := incomingTransitionContextPool.Get().(*incomingTransitionContextImpl)
@@ -586,6 +597,9 @@
 	if am, ok := ctx.Module().(Module); ok {
 		mctx := bottomUpMutatorContextFactory(ctx, am, a.finalPhase)
 		defer bottomUpMutatorContextPool.Put(mctx)
+		base := am.base()
+		base.commonProperties.DebugMutators = append(base.commonProperties.DebugMutators, a.name)
+		base.commonProperties.DebugVariations = append(base.commonProperties.DebugVariations, variation)
 		a.mutator.Mutate(mctx, variation)
 	}
 }
@@ -594,6 +608,7 @@
 	atm := &androidTransitionMutator{
 		finalPhase: x.finalPhase,
 		mutator:    m,
+		name:       name,
 	}
 	mutator := &mutator{
 		name:              name,
diff --git a/android/selects_test.go b/android/selects_test.go
index e59b3e6..f912ce6 100644
--- a/android/selects_test.go
+++ b/android/selects_test.go
@@ -269,11 +269,11 @@
 			},
 		},
 		{
-			name: "Select on variant",
+			name: "Select on arch",
 			bp: `
 			my_module_type {
 				name: "foo",
-				my_string: select(variant("arch"), {
+				my_string: select(arch(), {
 					"x86": "my_x86",
 					"x86_64": "my_x86_64",
 					"arm": "my_arm",
@@ -287,6 +287,22 @@
 			},
 		},
 		{
+			name: "Select on os",
+			bp: `
+			my_module_type {
+				name: "foo",
+				my_string: select(os(), {
+					"android": "my_android",
+					"linux": "my_linux",
+					default: "my_default",
+				}),
+			}
+			`,
+			provider: selectsTestProvider{
+				my_string: proptools.StringPtr("my_android"),
+			},
+		},
+		{
 			name: "Unset value",
 			bp: `
 			my_module_type {
@@ -327,8 +343,10 @@
 			my_module_type {
 				name: "foo",
 				my_string: select(soong_config_variable("my_namespace", "my_variable"), {
+					"foo": "bar",
 					default: unset,
 				}) + select(soong_config_variable("my_namespace", "my_variable2"), {
+					"baz": "qux",
 					default: unset,
 				})
 			}
@@ -341,6 +359,7 @@
 			my_module_type {
 				name: "foo",
 				my_string: select(soong_config_variable("my_namespace", "my_variable"), {
+					"foo": "bar",
 					default: unset,
 				}) + select(soong_config_variable("my_namespace", "my_variable2"), {
 					default: "a",
@@ -414,6 +433,169 @@
 				replacing_string_list: &[]string{"b1"},
 			},
 		},
+		{
+			name: "Multi-condition string 1",
+			bp: `
+			my_module_type {
+				name: "foo",
+				my_string: select((
+					soong_config_variable("my_namespace", "my_variable"),
+					soong_config_variable("my_namespace", "my_variable2"),
+				), {
+					("a", "b"): "a+b",
+					("a", default): "a+default",
+					(default, default): "default",
+				}),
+			}
+			`,
+			vendorVars: map[string]map[string]string{
+				"my_namespace": {
+					"my_variable":  "a",
+					"my_variable2": "b",
+				},
+			},
+			provider: selectsTestProvider{
+				my_string: proptools.StringPtr("a+b"),
+			},
+		},
+		{
+			name: "Multi-condition string 2",
+			bp: `
+			my_module_type {
+				name: "foo",
+				my_string: select((
+					soong_config_variable("my_namespace", "my_variable"),
+					soong_config_variable("my_namespace", "my_variable2"),
+				), {
+					("a", "b"): "a+b",
+					("a", default): "a+default",
+					(default, default): "default",
+				}),
+			}
+			`,
+			vendorVars: map[string]map[string]string{
+				"my_namespace": {
+					"my_variable":  "a",
+					"my_variable2": "c",
+				},
+			},
+			provider: selectsTestProvider{
+				my_string: proptools.StringPtr("a+default"),
+			},
+		},
+		{
+			name: "Multi-condition string 3",
+			bp: `
+			my_module_type {
+				name: "foo",
+				my_string: select((
+					soong_config_variable("my_namespace", "my_variable"),
+					soong_config_variable("my_namespace", "my_variable2"),
+				), {
+					("a", "b"): "a+b",
+					("a", default): "a+default",
+					(default, default): "default",
+				}),
+			}
+			`,
+			vendorVars: map[string]map[string]string{
+				"my_namespace": {
+					"my_variable":  "c",
+					"my_variable2": "b",
+				},
+			},
+			provider: selectsTestProvider{
+				my_string: proptools.StringPtr("default"),
+			},
+		},
+		{
+			name: "Select on boolean",
+			bp: `
+			my_module_type {
+				name: "foo",
+				my_string: select(boolean_var_for_testing(), {
+					true: "t",
+					false: "f",
+				}),
+			}
+			`,
+			vendorVars: map[string]map[string]string{
+				"boolean_var": {
+					"for_testing": "true",
+				},
+			},
+			provider: selectsTestProvider{
+				my_string: proptools.StringPtr("t"),
+			},
+		},
+		{
+			name: "Select on boolean false",
+			bp: `
+			my_module_type {
+				name: "foo",
+				my_string: select(boolean_var_for_testing(), {
+					true: "t",
+					false: "f",
+				}),
+			}
+			`,
+			vendorVars: map[string]map[string]string{
+				"boolean_var": {
+					"for_testing": "false",
+				},
+			},
+			provider: selectsTestProvider{
+				my_string: proptools.StringPtr("f"),
+			},
+		},
+		{
+			name: "Select on boolean undefined",
+			bp: `
+			my_module_type {
+				name: "foo",
+				my_string: select(boolean_var_for_testing(), {
+					true: "t",
+					false: "f",
+				}),
+			}
+			`,
+			expectedError: "foo",
+		},
+		{
+			name: "Select on boolean undefined with default",
+			bp: `
+			my_module_type {
+				name: "foo",
+				my_string: select(boolean_var_for_testing(), {
+					true: "t",
+					false: "f",
+					default: "default",
+				}),
+			}
+			`,
+			provider: selectsTestProvider{
+				my_string: proptools.StringPtr("default"),
+			},
+		},
+		{
+			name: "Mismatched condition types",
+			bp: `
+			my_module_type {
+				name: "foo",
+				my_string: select(boolean_var_for_testing(), {
+					"true": "t",
+					"false": "f",
+					default: "default",
+				}),
+			}
+			`,
+			vendorVars: map[string]map[string]string{
+				"boolean_var": {
+					"for_testing": "false",
+				},
+			},
+			expectedError: "Expected all branches of a select on condition boolean_var_for_testing\\(\\) to have type bool, found string",
+		},
 	}
 
 	for _, tc := range testCases {
diff --git a/android/variable.go b/android/variable.go
index 5a079db..0040d83 100644
--- a/android/variable.go
+++ b/android/variable.go
@@ -201,23 +201,22 @@
 	BuildThumbprintFile *string `json:",omitempty"`
 	DisplayBuildNumber  *bool   `json:",omitempty"`
 
-	Platform_display_version_name             *string  `json:",omitempty"`
-	Platform_version_name                     *string  `json:",omitempty"`
-	Platform_sdk_version                      *int     `json:",omitempty"`
-	Platform_sdk_codename                     *string  `json:",omitempty"`
-	Platform_sdk_version_or_codename          *string  `json:",omitempty"`
-	Platform_sdk_final                        *bool    `json:",omitempty"`
-	Platform_sdk_extension_version            *int     `json:",omitempty"`
-	Platform_base_sdk_extension_version       *int     `json:",omitempty"`
-	Platform_version_active_codenames         []string `json:",omitempty"`
-	Platform_version_all_preview_codenames    []string `json:",omitempty"`
-	Platform_systemsdk_versions               []string `json:",omitempty"`
-	Platform_security_patch                   *string  `json:",omitempty"`
-	Platform_preview_sdk_version              *string  `json:",omitempty"`
-	Platform_min_supported_target_sdk_version *string  `json:",omitempty"`
-	Platform_base_os                          *string  `json:",omitempty"`
-	Platform_version_last_stable              *string  `json:",omitempty"`
-	Platform_version_known_codenames          *string  `json:",omitempty"`
+	Platform_display_version_name          *string  `json:",omitempty"`
+	Platform_version_name                  *string  `json:",omitempty"`
+	Platform_sdk_version                   *int     `json:",omitempty"`
+	Platform_sdk_codename                  *string  `json:",omitempty"`
+	Platform_sdk_version_or_codename       *string  `json:",omitempty"`
+	Platform_sdk_final                     *bool    `json:",omitempty"`
+	Platform_sdk_extension_version         *int     `json:",omitempty"`
+	Platform_base_sdk_extension_version    *int     `json:",omitempty"`
+	Platform_version_active_codenames      []string `json:",omitempty"`
+	Platform_version_all_preview_codenames []string `json:",omitempty"`
+	Platform_systemsdk_versions            []string `json:",omitempty"`
+	Platform_security_patch                *string  `json:",omitempty"`
+	Platform_preview_sdk_version           *string  `json:",omitempty"`
+	Platform_base_os                       *string  `json:",omitempty"`
+	Platform_version_last_stable           *string  `json:",omitempty"`
+	Platform_version_known_codenames       *string  `json:",omitempty"`
 
 	DeviceName                            *string  `json:",omitempty"`
 	DeviceProduct                         *string  `json:",omitempty"`
diff --git a/bpfix/bpfix/bpfix_test.go b/bpfix/bpfix/bpfix_test.go
index 672e852..b5b49b1 100644
--- a/bpfix/bpfix/bpfix_test.go
+++ b/bpfix/bpfix/bpfix_test.go
@@ -19,6 +19,7 @@
 import (
 	"bytes"
 	"fmt"
+	"os"
 	"reflect"
 	"strings"
 	"testing"
@@ -2215,3 +2216,9 @@
 		})
 	}
 }
+
+func TestMain(m *testing.M) {
+	// Skip checking Android.mk path with cleaning "ANDROID_BUILD_TOP"
+	os.Setenv("ANDROID_BUILD_TOP", "")
+	os.Exit(m.Run())
+}
diff --git a/cc/cc.go b/cc/cc.go
index a1cae39..e3954d7 100644
--- a/cc/cc.go
+++ b/cc/cc.go
@@ -1995,6 +1995,20 @@
 }
 
 func (c *Module) GenerateAndroidBuildActions(actx android.ModuleContext) {
+	ctx := moduleContextFromAndroidModuleContext(actx, c)
+
+	// If Test_only is set on a module in bp file, respect the setting, otherwise
+	// see if is a known test module type.
+	testOnly := c.testModule || c.testLibrary()
+	if c.sourceProperties.Test_only != nil {
+		testOnly = Bool(c.sourceProperties.Test_only)
+	}
+	// Keep before any early returns.
+	android.SetProvider(ctx, android.TestOnlyProviderKey, android.TestModuleInformation{
+		TestOnly:       testOnly,
+		TopLevelTarget: c.testModule,
+	})
+
 	// Handle the case of a test module split by `test_per_src` mutator.
 	//
 	// The `test_per_src` mutator adds an extra variation named "", depending on all the other
@@ -2013,8 +2027,6 @@
 
 	c.makeLinkType = GetMakeLinkType(actx, c)
 
-	ctx := moduleContextFromAndroidModuleContext(actx, c)
-
 	deps := c.depsToPaths(ctx)
 	if ctx.Failed() {
 		return
@@ -2141,17 +2153,6 @@
 		android.SetProvider(ctx, testing.TestModuleProviderKey, testing.TestModuleProviderData{})
 	}
 
-	// If Test_only is set on a module in bp file, respect the setting, otherwise
-	// see if is a known test module type.
-	testOnly := c.testModule || c.testLibrary()
-	if c.sourceProperties.Test_only != nil {
-		testOnly = Bool(c.sourceProperties.Test_only)
-	}
-	android.SetProvider(ctx, android.TestOnlyProviderKey, android.TestModuleInformation{
-		TestOnly:       testOnly,
-		TopLevelTarget: c.testModule,
-	})
-
 	android.SetProvider(ctx, blueprint.SrcsFileProviderKey, blueprint.SrcsFileProviderData{SrcPaths: deps.GeneratedSources.Strings()})
 
 	android.CollectDependencyAconfigFiles(ctx, &c.mergedAconfigFiles)
diff --git a/cc/cc_test_only_property_test.go b/cc/cc_test_only_property_test.go
index 972e86b..c14f34e 100644
--- a/cc/cc_test_only_property_test.go
+++ b/cc/cc_test_only_property_test.go
@@ -78,6 +78,38 @@
 	}
 }
 
+func TestTestOnlyValueWithTestPerSrcProp(t *testing.T) {
+	t.Parallel()
+	ctx := android.GroupFixturePreparers(
+		prepareForCcTest,
+	).RunTestWithBp(t, `
+                // These should be test-only
+                cc_test { name: "cc-test",
+                          gtest: false,
+                          test_per_src: true,
+                          srcs: ["foo_test.cpp"],
+                          test_options: { unit_test: false, },
+                         }
+	`)
+
+	// Ensure all variation of test-per-src tests are marked test-only.
+	ctx.VisitAllModules(func(m blueprint.Module) {
+		testOnly := false
+		if provider, ok := android.OtherModuleProvider(ctx.TestContext.OtherModuleProviderAdaptor(), m, android.TestOnlyProviderKey); ok {
+			if provider.TestOnly {
+				testOnly = true
+			}
+		}
+		if module, ok := m.(*Module); ok {
+			if testModule, ok := module.installer.(*testBinary); ok {
+				if !testOnly && *testModule.Properties.Test_per_src {
+					t.Errorf("%v is not test-only but should be", m)
+				}
+			}
+		}
+	})
+}
+
 func TestTestOnlyInTeamsProto(t *testing.T) {
 	t.Parallel()
 	ctx := android.GroupFixturePreparers(
diff --git a/cmd/release_config/Android.bp b/cmd/release_config/Android.bp
deleted file mode 100644
index 7f627ff..0000000
--- a/cmd/release_config/Android.bp
+++ /dev/null
@@ -1,30 +0,0 @@
-package {
-    default_applicable_licenses: ["Android-Apache-2.0"],
-}
-
-bootstrap_go_package {
-    name: "release-config",
-    pkgPath: "android/soong/cmd/release_config",
-    deps: [
-        "golang-protobuf-encoding-prototext",
-        "golang-protobuf-reflect-protoreflect",
-        "golang-protobuf-runtime-protoimpl",
-        "soong-cmd-release-config-proto",
-    ],
-    srcs: [
-        "main.go",
-    ],
-}
-
-bootstrap_go_package {
-    name: "soong-cmd-release-config-proto",
-    pkgPath: "android/soong/cmd/release_config/release_config_proto",
-    deps: [
-        "golang-protobuf-reflect-protoreflect",
-        "golang-protobuf-runtime-protoimpl",
-    ],
-    srcs: [
-        "release_config_proto/build_flags_out.pb.go",
-        "release_config_proto/build_flags_src.pb.go",
-    ],
-}
diff --git a/cmd/release_config/main.go b/cmd/release_config/main.go
deleted file mode 100644
index 3bb6b3d..0000000
--- a/cmd/release_config/main.go
+++ /dev/null
@@ -1,691 +0,0 @@
-// Copyright 2024 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 main
-
-import (
-	"cmp"
-	"encoding/json"
-	"flag"
-	"fmt"
-	"io/fs"
-	"os"
-	"path/filepath"
-	"slices"
-	"strings"
-
-	"android/soong/cmd/release_config/release_config_proto"
-
-	"google.golang.org/protobuf/encoding/prototext"
-	"google.golang.org/protobuf/proto"
-)
-
-var verboseFlag bool
-
-type StringList []string
-
-func (l *StringList) Set(v string) error {
-	*l = append(*l, v)
-	return nil
-}
-
-func (l *StringList) String() string {
-	return fmt.Sprintf("%v", *l)
-}
-
-var releaseConfigMapPaths StringList
-
-func DumpProtos(outDir string, message proto.Message) error {
-	basePath := filepath.Join(outDir, "all_release_configs")
-	writer := func(suffix string, marshal func() ([]byte, error)) error {
-		data, err := marshal()
-		if err != nil {
-			return err
-		}
-		return os.WriteFile(fmt.Sprintf("%s.%s", basePath, suffix), data, 0644)
-	}
-	err := writer("textproto", func() ([]byte, error) { return prototext.MarshalOptions{Multiline: true}.Marshal(message) })
-	if err != nil {
-		return err
-	}
-
-	err = writer("pb", func() ([]byte, error) { return proto.Marshal(message) })
-	if err != nil {
-		return err
-	}
-
-	return writer("json", func() ([]byte, error) { return json.MarshalIndent(message, "", "  ") })
-}
-
-func LoadTextproto(path string, message proto.Message) error {
-	data, err := os.ReadFile(path)
-	if err != nil {
-		return err
-	}
-	ret := prototext.Unmarshal(data, message)
-	if verboseFlag {
-		debug, _ := prototext.Marshal(message)
-		fmt.Printf("%s: %s\n", path, debug)
-	}
-	return ret
-}
-
-func WalkTextprotoFiles(root string, subdir string, Func fs.WalkDirFunc) error {
-	path := filepath.Join(root, subdir)
-	if _, err := os.Stat(path); err != nil {
-		// Missing subdirs are not an error.
-		return nil
-	}
-	return filepath.WalkDir(path, func(path string, d fs.DirEntry, err error) error {
-		if err != nil {
-			return err
-		}
-		if strings.HasSuffix(d.Name(), ".textproto") && d.Type().IsRegular() {
-			return Func(path, d, err)
-		}
-		return nil
-	})
-}
-
-type FlagValue struct {
-	// The path providing this value.
-	path string
-
-	// Protobuf
-	proto release_config_proto.FlagValue
-}
-
-func FlagValueFactory(protoPath string) (fv *FlagValue) {
-	fv = &FlagValue{path: protoPath}
-	if protoPath != "" {
-		LoadTextproto(protoPath, &fv.proto)
-	}
-	return fv
-}
-
-// One directory's contribution to the a release config.
-type ReleaseConfigContribution struct {
-	// Paths to files providing this config.
-	path string
-
-	// The index of the config directory where this release config
-	// contribution was declared.
-	// Flag values cannot be set in a location with a lower index.
-	DeclarationIndex int
-
-	// Protobufs relevant to the config.
-	proto release_config_proto.ReleaseConfig
-
-	FlagValues []*FlagValue
-}
-
-// A single release_config_map.textproto and its associated data.
-// Used primarily for debugging.
-type ReleaseConfigMap struct {
-	// The path to this release_config_map file.
-	path string
-
-	// Data received
-	proto release_config_proto.ReleaseConfigMap
-
-	ReleaseConfigContributions map[string]*ReleaseConfigContribution
-	FlagDeclarations           []release_config_proto.FlagDeclaration
-}
-
-// A generated release config.
-type ReleaseConfig struct {
-	// the Name of the release config
-	Name string
-
-	// The index of the config directory where this release config was
-	// first declared.
-	// Flag values cannot be set in a location with a lower index.
-	DeclarationIndex int
-
-	// What contributes to this config.
-	Contributions []*ReleaseConfigContribution
-
-	// Aliases for this release
-	OtherNames []string
-
-	// The names of release configs that we inherit
-	InheritNames []string
-
-	// Unmarshalled flag artifacts
-	FlagArtifacts FlagArtifacts
-
-	// Generated release config
-	ReleaseConfigArtifact *release_config_proto.ReleaseConfigArtifact
-
-	// We have begun compiling this release config.
-	compileInProgress bool
-}
-
-type FlagArtifact struct {
-	FlagDeclaration *release_config_proto.FlagDeclaration
-
-	// The index of the config directory where this flag was declared.
-	// Flag values cannot be set in a location with a lower index.
-	DeclarationIndex int
-
-	Traces []*release_config_proto.Tracepoint
-
-	// Assigned value
-	Value *release_config_proto.Value
-}
-
-// Key is flag name.
-type FlagArtifacts map[string]*FlagArtifact
-
-type ReleaseConfigDirMap map[string]int
-
-// The generated release configs.
-type ReleaseConfigs struct {
-	// Ordered list of release config maps processed.
-	ReleaseConfigMaps []*ReleaseConfigMap
-
-	// Aliases
-	Aliases map[string]*string
-
-	// Dictionary of flag_name:FlagDeclaration, with no overrides applied.
-	FlagArtifacts FlagArtifacts
-
-	// Dictionary of name:ReleaseConfig
-	ReleaseConfigs map[string]*ReleaseConfig
-
-	// Generated release configs
-	Artifact release_config_proto.ReleaseConfigsArtifact
-
-	// The list of config directories used.
-	ConfigDirs []string
-
-	// A map from the config directory to its order in the list of config
-	// directories.
-	ConfigDirIndexes ReleaseConfigDirMap
-}
-
-func (src *FlagArtifact) Clone() *FlagArtifact {
-	value := &release_config_proto.Value{}
-	proto.Merge(value, src.Value)
-	return &FlagArtifact{
-		FlagDeclaration: src.FlagDeclaration,
-		Traces:          src.Traces,
-		Value:           value,
-	}
-}
-
-func (src FlagArtifacts) Clone() (dst FlagArtifacts) {
-	if dst == nil {
-		dst = make(FlagArtifacts)
-	}
-	for k, v := range src {
-		dst[k] = v.Clone()
-	}
-	return
-}
-
-func ReleaseConfigFactory(name string, index int) (c *ReleaseConfig) {
-	return &ReleaseConfig{Name: name, DeclarationIndex: index}
-}
-
-func ReleaseConfigsFactory() (c *ReleaseConfigs) {
-	return &ReleaseConfigs{
-		Aliases:          make(map[string]*string),
-		FlagArtifacts:    make(map[string]*FlagArtifact),
-		ReleaseConfigs:   make(map[string]*ReleaseConfig),
-		ConfigDirs:       []string{},
-		ConfigDirIndexes: make(ReleaseConfigDirMap),
-	}
-}
-
-func ReleaseConfigMapFactory(protoPath string) (m *ReleaseConfigMap) {
-	m = &ReleaseConfigMap{
-		path:                       protoPath,
-		ReleaseConfigContributions: make(map[string]*ReleaseConfigContribution),
-	}
-	if protoPath != "" {
-		LoadTextproto(protoPath, &m.proto)
-	}
-	return m
-}
-
-func FlagDeclarationFactory(protoPath string) (fd *release_config_proto.FlagDeclaration) {
-	fd = &release_config_proto.FlagDeclaration{}
-	if protoPath != "" {
-		LoadTextproto(protoPath, fd)
-	}
-	return fd
-}
-
-func (configs *ReleaseConfigs) LoadReleaseConfigMap(path string, ConfigDirIndex int) error {
-	m := ReleaseConfigMapFactory(path)
-	if m.proto.Origin == nil || *m.proto.Origin == "" {
-		return fmt.Errorf("Release config map %s lacks origin", path)
-	}
-	if m.proto.DefaultContainer == nil {
-		return fmt.Errorf("Release config map %s lacks default_container", path)
-	}
-	dir := filepath.Dir(path)
-	// Record any aliases, checking for duplicates.
-	for _, alias := range m.proto.Aliases {
-		name := *alias.Name
-		oldTarget, ok := configs.Aliases[name]
-		if ok {
-			if *oldTarget != *alias.Target {
-				return fmt.Errorf("Conflicting alias declarations: %s vs %s",
-					*oldTarget, *alias.Target)
-			}
-		}
-		configs.Aliases[name] = alias.Target
-	}
-	var err error
-	err = WalkTextprotoFiles(dir, "flag_declarations", func(path string, d fs.DirEntry, err error) error {
-		flagDeclaration := FlagDeclarationFactory(path)
-		// Container must be specified.
-		if flagDeclaration.Container == nil {
-			flagDeclaration.Container = m.proto.DefaultContainer
-		}
-		// TODO: drop flag_declaration.origin from the proto.
-		if flagDeclaration.Origin == nil {
-			flagDeclaration.Origin = m.proto.Origin
-		}
-		// There is always a default value.
-		if flagDeclaration.Value == nil {
-			flagDeclaration.Value = &release_config_proto.Value{Val: &release_config_proto.Value_UnspecifiedValue{true}}
-		}
-		m.FlagDeclarations = append(m.FlagDeclarations, *flagDeclaration)
-		name := *flagDeclaration.Name
-		if def, ok := configs.FlagArtifacts[name]; !ok {
-			configs.FlagArtifacts[name] = &FlagArtifact{FlagDeclaration: flagDeclaration, DeclarationIndex: ConfigDirIndex}
-		} else if !proto.Equal(def.FlagDeclaration, flagDeclaration) {
-			return fmt.Errorf("Duplicate definition of %s", *flagDeclaration.Name)
-		}
-		// Set the initial value in the flag artifact.
-		configs.FlagArtifacts[name].UpdateValue(
-			FlagValue{path: path, proto: release_config_proto.FlagValue{
-				Name: proto.String(name), Value: flagDeclaration.Value}})
-		return nil
-	})
-	if err != nil {
-		return err
-	}
-
-	err = WalkTextprotoFiles(dir, "release_configs", func(path string, d fs.DirEntry, err error) error {
-		releaseConfigContribution := &ReleaseConfigContribution{path: path, DeclarationIndex: ConfigDirIndex}
-		LoadTextproto(path, &releaseConfigContribution.proto)
-		name := *releaseConfigContribution.proto.Name
-		if fmt.Sprintf("%s.textproto", name) != filepath.Base(path) {
-			return fmt.Errorf("%s incorrectly declares release config %s", path, name)
-		}
-		if _, ok := configs.ReleaseConfigs[name]; !ok {
-			configs.ReleaseConfigs[name] = ReleaseConfigFactory(name, ConfigDirIndex)
-		}
-		config := configs.ReleaseConfigs[name]
-		config.InheritNames = append(config.InheritNames, releaseConfigContribution.proto.Inherits...)
-
-		// Only walk flag_values/{RELEASE} for defined releases.
-		err2 := WalkTextprotoFiles(dir, filepath.Join("flag_values", name), func(path string, d fs.DirEntry, err error) error {
-			flagValue := FlagValueFactory(path)
-			if fmt.Sprintf("%s.textproto", *flagValue.proto.Name) != filepath.Base(path) {
-				return fmt.Errorf("%s incorrectly sets value for flag %s", path, *flagValue.proto.Name)
-			}
-			releaseConfigContribution.FlagValues = append(releaseConfigContribution.FlagValues, flagValue)
-			return nil
-		})
-		if err2 != nil {
-			return err2
-		}
-		m.ReleaseConfigContributions[name] = releaseConfigContribution
-		config.Contributions = append(config.Contributions, releaseConfigContribution)
-		return nil
-	})
-	if err != nil {
-		return err
-	}
-	configs.ReleaseConfigMaps = append(configs.ReleaseConfigMaps, m)
-	return nil
-}
-
-func (configs *ReleaseConfigs) GetReleaseConfig(name string) (*ReleaseConfig, error) {
-	trace := []string{name}
-	for target, ok := configs.Aliases[name]; ok; target, ok = configs.Aliases[name] {
-		name = *target
-		trace = append(trace, name)
-	}
-	if config, ok := configs.ReleaseConfigs[name]; ok {
-		return config, nil
-	}
-	return nil, fmt.Errorf("Missing config %s.  Trace=%v", name, trace)
-}
-
-func (configs *ReleaseConfigs) DumpMakefile(outDir, targetRelease string) error {
-	outFile := filepath.Join(outDir, "release_config.mk")
-	makeVars := make(map[string]string)
-	config, err := configs.GetReleaseConfig(targetRelease)
-	if err != nil {
-		return err
-	}
-	// Sort the flags by name first.
-	names := []string{}
-	for k, _ := range config.FlagArtifacts {
-		names = append(names, k)
-	}
-	slices.SortFunc(names, func(a, b string) int {
-		return cmp.Compare(a, b)
-	})
-	partitions := make(map[string][]string)
-
-	vNames := []string{}
-	addVar := func(name, suffix, value string) {
-		fullName := fmt.Sprintf("_ALL_RELEASE_FLAGS.%s.%s", name, suffix)
-		vNames = append(vNames, fullName)
-		makeVars[fullName] = value
-	}
-
-	for _, name := range names {
-		flag := config.FlagArtifacts[name]
-		decl := flag.FlagDeclaration
-
-		// cName := strings.ToLower(release_config_proto.Container_name[decl.GetContainer()])
-		cName := strings.ToLower(decl.Container.String())
-		if cName == strings.ToLower(release_config_proto.Container_ALL.String()) {
-			partitions["product"] = append(partitions["product"], name)
-			partitions["system"] = append(partitions["system"], name)
-			partitions["system_ext"] = append(partitions["system_ext"], name)
-			partitions["vendor"] = append(partitions["vendor"], name)
-		} else {
-			partitions[cName] = append(partitions[cName], name)
-		}
-		value := MarshalValue(flag.Value)
-		makeVars[name] = value
-		addVar(name, "PARTITIONS", cName)
-		addVar(name, "DEFAULT", MarshalValue(decl.Value))
-		addVar(name, "VALUE", value)
-		addVar(name, "DECLARED_IN", *flag.Traces[0].Source)
-		addVar(name, "SET_IN", *flag.Traces[len(flag.Traces)-1].Source)
-		addVar(name, "ORIGIN", *decl.Origin)
-	}
-	pNames := []string{}
-	for k, _ := range partitions {
-		pNames = append(pNames, k)
-	}
-	slices.SortFunc(pNames, func(a, b string) int {
-		return cmp.Compare(a, b)
-	})
-
-	// Now sort the make variables, and output them.
-	slices.SortFunc(vNames, func(a, b string) int {
-		return cmp.Compare(a, b)
-	})
-
-	// Write the flags as:
-	//   _ALL_RELELASE_FLAGS
-	//   _ALL_RELEASE_FLAGS.PARTITIONS.*
-	//   all _ALL_RELEASE_FLAGS.*, sorted by name
-	//   Final flag values, sorted by name.
-	data := fmt.Sprintf("_ALL_RELEASE_FLAGS :=$= %s\n", strings.Join(names, " "))
-	for _, pName := range pNames {
-		data += fmt.Sprintf("_ALL_RELEASE_FLAGS.PARTITIONS.%s :=$= %s\n", pName, strings.Join(partitions[pName], " "))
-	}
-	for _, vName := range vNames {
-		data += fmt.Sprintf("%s :=$= %s\n", vName, makeVars[vName])
-	}
-	data += "\n\n# Values for all build flags\n"
-	data += fmt.Sprintf("RELEASE_ACONFIG_VALUE_SETS :=$= %s\n",
-		strings.Join(config.ReleaseConfigArtifact.AconfigValueSets, " "))
-	for _, name := range names {
-		data += fmt.Sprintf("%s :=$= %s\n", name, makeVars[name])
-	}
-	return os.WriteFile(outFile, []byte(data), 0644)
-}
-
-func (configs *ReleaseConfigs) GenerateReleaseConfigs(targetRelease string) error {
-	otherNames := make(map[string][]string)
-	for aliasName, aliasTarget := range configs.Aliases {
-		if _, ok := configs.ReleaseConfigs[aliasName]; ok {
-			return fmt.Errorf("Alias %s is a declared release config", aliasName)
-		}
-		if _, ok := configs.ReleaseConfigs[*aliasTarget]; !ok {
-			if _, ok2 := configs.Aliases[*aliasTarget]; !ok2 {
-				return fmt.Errorf("Alias %s points to non-existing config %s", aliasName, *aliasTarget)
-			}
-		}
-		otherNames[*aliasTarget] = append(otherNames[*aliasTarget], aliasName)
-	}
-	for name, aliases := range otherNames {
-		configs.ReleaseConfigs[name].OtherNames = aliases
-	}
-
-	for _, config := range configs.ReleaseConfigs {
-		err := config.GenerateReleaseConfig(configs)
-		if err != nil {
-			return err
-		}
-	}
-
-	releaseConfig, err := configs.GetReleaseConfig(targetRelease)
-	if err != nil {
-		return err
-	}
-	configs.Artifact = release_config_proto.ReleaseConfigsArtifact{
-		ReleaseConfig: releaseConfig.ReleaseConfigArtifact,
-		OtherReleaseConfigs: func() []*release_config_proto.ReleaseConfigArtifact {
-			orc := []*release_config_proto.ReleaseConfigArtifact{}
-			for name, config := range configs.ReleaseConfigs {
-				if name != releaseConfig.Name {
-					orc = append(orc, config.ReleaseConfigArtifact)
-				}
-			}
-			return orc
-		}(),
-	}
-	return nil
-}
-
-func MarshalValue(value *release_config_proto.Value) string {
-	switch val := value.Val.(type) {
-	case *release_config_proto.Value_UnspecifiedValue:
-		// Value was never set.
-		return ""
-	case *release_config_proto.Value_StringValue:
-		return val.StringValue
-	case *release_config_proto.Value_BoolValue:
-		if val.BoolValue {
-			return "true"
-		}
-		// False ==> empty string
-		return ""
-	case *release_config_proto.Value_Obsolete:
-		return " #OBSOLETE"
-	default:
-		// Flagged as error elsewhere, so return empty string here.
-		return ""
-	}
-}
-
-func (fa *FlagArtifact) UpdateValue(flagValue FlagValue) error {
-	name := *flagValue.proto.Name
-	fa.Traces = append(fa.Traces, &release_config_proto.Tracepoint{Source: proto.String(flagValue.path), Value: flagValue.proto.Value})
-	if fa.Value.GetObsolete() {
-		return fmt.Errorf("Attempting to set obsolete flag %s. Trace=%v", name, fa.Traces)
-	}
-	switch val := flagValue.proto.Value.Val.(type) {
-	case *release_config_proto.Value_StringValue:
-		fa.Value = &release_config_proto.Value{Val: &release_config_proto.Value_StringValue{val.StringValue}}
-	case *release_config_proto.Value_BoolValue:
-		fa.Value = &release_config_proto.Value{Val: &release_config_proto.Value_BoolValue{val.BoolValue}}
-	case *release_config_proto.Value_Obsolete:
-		if !val.Obsolete {
-			return fmt.Errorf("%s: Cannot set obsolete=false.  Trace=%v", name, fa.Traces)
-		}
-		fa.Value = &release_config_proto.Value{Val: &release_config_proto.Value_Obsolete{true}}
-	default:
-		return fmt.Errorf("Invalid type for flag_value: %T.  Trace=%v", val, fa.Traces)
-	}
-	return nil
-}
-
-func (fa *FlagArtifact) Marshal() (*release_config_proto.FlagArtifact, error) {
-	return &release_config_proto.FlagArtifact{
-		FlagDeclaration: fa.FlagDeclaration,
-		Value:           fa.Value,
-		Traces:          fa.Traces,
-	}, nil
-}
-
-func (config *ReleaseConfig) GenerateReleaseConfig(configs *ReleaseConfigs) error {
-	if config.ReleaseConfigArtifact != nil {
-		return nil
-	}
-	if config.compileInProgress {
-		return fmt.Errorf("Loop detected for release config %s", config.Name)
-	}
-	config.compileInProgress = true
-
-	// Generate any configs we need to inherit.  This will detect loops in
-	// the config.
-	contributionsToApply := []*ReleaseConfigContribution{}
-	myInherits := []string{}
-	myInheritsSet := make(map[string]bool)
-	for _, inherit := range config.InheritNames {
-		if _, ok := myInheritsSet[inherit]; ok {
-			continue
-		}
-		myInherits = append(myInherits, inherit)
-		myInheritsSet[inherit] = true
-		iConfig, err := configs.GetReleaseConfig(inherit)
-		if err != nil {
-			return err
-		}
-		iConfig.GenerateReleaseConfig(configs)
-		contributionsToApply = append(contributionsToApply, iConfig.Contributions...)
-	}
-	contributionsToApply = append(contributionsToApply, config.Contributions...)
-
-	myAconfigValueSets := []string{}
-	myFlags := configs.FlagArtifacts.Clone()
-	myDirsMap := make(map[int]bool)
-	for _, contrib := range contributionsToApply {
-		myAconfigValueSets = append(myAconfigValueSets, contrib.proto.AconfigValueSets...)
-		myDirsMap[contrib.DeclarationIndex] = true
-		for _, value := range contrib.FlagValues {
-			fa, ok := myFlags[*value.proto.Name]
-			if !ok {
-				return fmt.Errorf("Setting value for undefined flag %s in %s\n", *value.proto.Name, value.path)
-			}
-			myDirsMap[fa.DeclarationIndex] = true
-			if fa.DeclarationIndex > contrib.DeclarationIndex {
-				// Setting location is to the left of declaration.
-				return fmt.Errorf("Setting value for flag %s not allowed in %s\n", *value.proto.Name, value.path)
-			}
-			if err := fa.UpdateValue(*value); err != nil {
-				return err
-			}
-		}
-	}
-
-	directories := []string{}
-	for idx, confDir := range configs.ConfigDirs {
-		if _, ok := myDirsMap[idx]; ok {
-			directories = append(directories, confDir)
-		}
-	}
-
-	config.FlagArtifacts = myFlags
-	config.ReleaseConfigArtifact = &release_config_proto.ReleaseConfigArtifact{
-		Name:       proto.String(config.Name),
-		OtherNames: config.OtherNames,
-		FlagArtifacts: func() []*release_config_proto.FlagArtifact {
-			ret := []*release_config_proto.FlagArtifact{}
-			for _, flag := range myFlags {
-				ret = append(ret, &release_config_proto.FlagArtifact{
-					FlagDeclaration: flag.FlagDeclaration,
-					Traces:          flag.Traces,
-					Value:           flag.Value,
-				})
-			}
-			return ret
-		}(),
-		AconfigValueSets: myAconfigValueSets,
-		Inherits:         myInherits,
-		Directories:      directories,
-	}
-
-	config.compileInProgress = false
-	return nil
-}
-
-func main() {
-	var targetRelease string
-	var outputDir string
-
-	outEnv := os.Getenv("OUT_DIR")
-	if outEnv == "" {
-		outEnv = "out"
-	}
-	defaultOutputDir := filepath.Join(outEnv, "soong", "release-config")
-	var defaultMapPaths StringList
-	defaultLocations := StringList{
-		"build/release/release_config_map.textproto",
-		"vendor/google_shared/build/release/release_config_map.textproto",
-		"vendor/google/release/release_config_map.textproto",
-	}
-	for _, path := range defaultLocations {
-		if _, err := os.Stat(path); err == nil {
-			defaultMapPaths = append(defaultMapPaths, path)
-		}
-	}
-	prodMaps := os.Getenv("PRODUCT_RELEASE_CONFIG_MAPS")
-	if prodMaps != "" {
-		defaultMapPaths = append(defaultMapPaths, strings.Split(prodMaps, " ")...)
-	}
-
-	flag.BoolVar(&verboseFlag, "debug", false, "print debugging information")
-	flag.Var(&releaseConfigMapPaths, "map", "path to a release_config_map.textproto. may be repeated")
-	flag.StringVar(&targetRelease, "release", "trunk_staging", "TARGET_RELEASE for this build")
-	flag.StringVar(&outputDir, "out_dir", defaultOutputDir, "basepath for the output. Multiple formats are created")
-	flag.Parse()
-
-	if len(releaseConfigMapPaths) == 0 {
-		releaseConfigMapPaths = defaultMapPaths
-		fmt.Printf("No --map argument provided.  Using: --map %s\n", strings.Join(releaseConfigMapPaths, " --map "))
-	}
-
-	configs := ReleaseConfigsFactory()
-	for idx, releaseConfigMapPath := range releaseConfigMapPaths {
-		// Maintain an ordered list of release config directories.
-		configDir := filepath.Dir(releaseConfigMapPath)
-		configs.ConfigDirIndexes[configDir] = idx
-		configs.ConfigDirs = append(configs.ConfigDirs, configDir)
-		err := configs.LoadReleaseConfigMap(releaseConfigMapPath, idx)
-		if err != nil {
-			panic(err)
-		}
-	}
-
-	// Now that we have all of the release config maps, can meld them and generate the artifacts.
-	err := configs.GenerateReleaseConfigs(targetRelease)
-	if err != nil {
-		panic(err)
-	}
-	err = os.MkdirAll(outputDir, 0775)
-	if err != nil {
-		panic(err)
-	}
-	err = configs.DumpMakefile(outputDir, targetRelease)
-	if err != nil {
-		panic(err)
-	}
-	DumpProtos(outputDir, &configs.Artifact)
-}
diff --git a/cmd/release_config/release_config/Android.bp b/cmd/release_config/release_config/Android.bp
new file mode 100644
index 0000000..3c73826
--- /dev/null
+++ b/cmd/release_config/release_config/Android.bp
@@ -0,0 +1,18 @@
+package {
+    default_applicable_licenses: ["Android-Apache-2.0"],
+}
+
+bootstrap_go_package {
+    name: "soong-cmd-release_config-release_config",
+    pkgPath: "android/soong/cmd/release_config/release_config",
+    deps: [
+        "golang-protobuf-encoding-prototext",
+        "golang-protobuf-reflect-protoreflect",
+        "golang-protobuf-runtime-protoimpl",
+        "soong-cmd-release_config-proto",
+        "soong-cmd-release_config-lib",
+    ],
+    srcs: [
+        "main.go",
+    ],
+}
diff --git a/cmd/release_config/release_config/main.go b/cmd/release_config/release_config/main.go
new file mode 100644
index 0000000..076abfa
--- /dev/null
+++ b/cmd/release_config/release_config/main.go
@@ -0,0 +1,57 @@
+// Copyright 2024 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 main
+
+import (
+	"flag"
+	"os"
+
+	rc_lib "android/soong/cmd/release_config/release_config_lib"
+)
+
+func main() {
+	var top string
+	var releaseConfigMapPaths rc_lib.StringList
+	var targetRelease string
+	var outputDir string
+	var err error
+	var configs *rc_lib.ReleaseConfigs
+
+	flag.StringVar(&top, "top", ".", "path to top of workspace")
+	flag.Var(&releaseConfigMapPaths, "map", "path to a release_config_map.textproto. may be repeated")
+	flag.StringVar(&targetRelease, "release", "trunk_staging", "TARGET_RELEASE for this build")
+	flag.StringVar(&outputDir, "out_dir", rc_lib.GetDefaultOutDir(), "basepath for the output. Multiple formats are created")
+	flag.Parse()
+
+	if err = os.Chdir(top); err != nil {
+		panic(err)
+	}
+	configs, err = rc_lib.ReadReleaseConfigMaps(releaseConfigMapPaths, targetRelease)
+	if err != nil {
+		panic(err)
+	}
+	err = os.MkdirAll(outputDir, 0775)
+	if err != nil {
+		panic(err)
+	}
+	err = configs.DumpMakefile(outputDir, targetRelease)
+	if err != nil {
+		panic(err)
+	}
+	err = configs.DumpArtifact(outputDir)
+	if err != nil {
+		panic(err)
+	}
+}
diff --git a/cmd/release_config/release_config_lib/Android.bp b/cmd/release_config/release_config_lib/Android.bp
new file mode 100644
index 0000000..601194c
--- /dev/null
+++ b/cmd/release_config/release_config_lib/Android.bp
@@ -0,0 +1,36 @@
+// Copyright 2024 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 {
+    default_applicable_licenses: ["Android-Apache-2.0"],
+}
+
+bootstrap_go_package {
+    name: "soong-cmd-release_config-lib",
+    pkgPath: "android/soong/release_config/release_config_lib",
+    deps: [
+        "golang-protobuf-encoding-prototext",
+        "golang-protobuf-reflect-protoreflect",
+        "golang-protobuf-runtime-protoimpl",
+        "soong-cmd-release_config-proto",
+    ],
+    srcs: [
+        "flag_artifact.go",
+        "flag_declaration.go",
+        "flag_value.go",
+        "release_config.go",
+        "release_configs.go",
+        "util.go",
+    ],
+}
diff --git a/cmd/release_config/release_config_lib/flag_artifact.go b/cmd/release_config/release_config_lib/flag_artifact.go
new file mode 100644
index 0000000..51673a5
--- /dev/null
+++ b/cmd/release_config/release_config_lib/flag_artifact.go
@@ -0,0 +1,89 @@
+// Copyright 2024 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 release_config_lib
+
+import (
+	"fmt"
+
+	"android/soong/cmd/release_config/release_config_proto"
+
+	"google.golang.org/protobuf/proto"
+)
+
+type FlagArtifact struct {
+	FlagDeclaration *release_config_proto.FlagDeclaration
+
+	// The index of the config directory where this flag was declared.
+	// Flag values cannot be set in a location with a lower index.
+	DeclarationIndex int
+
+	Traces []*release_config_proto.Tracepoint
+
+	// Assigned value
+	Value *release_config_proto.Value
+}
+
+// Key is flag name.
+type FlagArtifacts map[string]*FlagArtifact
+
+func (src *FlagArtifact) Clone() *FlagArtifact {
+	value := &release_config_proto.Value{}
+	proto.Merge(value, src.Value)
+	return &FlagArtifact{
+		FlagDeclaration: src.FlagDeclaration,
+		Traces:          src.Traces,
+		Value:           value,
+	}
+}
+
+func (src FlagArtifacts) Clone() (dst FlagArtifacts) {
+	if dst == nil {
+		dst = make(FlagArtifacts)
+	}
+	for k, v := range src {
+		dst[k] = v.Clone()
+	}
+	return
+}
+
+func (fa *FlagArtifact) UpdateValue(flagValue FlagValue) error {
+	name := *flagValue.proto.Name
+	fa.Traces = append(fa.Traces, &release_config_proto.Tracepoint{Source: proto.String(flagValue.path), Value: flagValue.proto.Value})
+	if fa.Value.GetObsolete() {
+		return fmt.Errorf("Attempting to set obsolete flag %s. Trace=%v", name, fa.Traces)
+	}
+	switch val := flagValue.proto.Value.Val.(type) {
+	case *release_config_proto.Value_StringValue:
+		fa.Value = &release_config_proto.Value{Val: &release_config_proto.Value_StringValue{val.StringValue}}
+	case *release_config_proto.Value_BoolValue:
+		fa.Value = &release_config_proto.Value{Val: &release_config_proto.Value_BoolValue{val.BoolValue}}
+	case *release_config_proto.Value_Obsolete:
+		if !val.Obsolete {
+			return fmt.Errorf("%s: Cannot set obsolete=false.  Trace=%v", name, fa.Traces)
+		}
+		fa.Value = &release_config_proto.Value{Val: &release_config_proto.Value_Obsolete{true}}
+	default:
+		return fmt.Errorf("Invalid type for flag_value: %T.  Trace=%v", val, fa.Traces)
+	}
+	return nil
+}
+
+func (fa *FlagArtifact) Marshal() (*release_config_proto.FlagArtifact, error) {
+	return &release_config_proto.FlagArtifact{
+		FlagDeclaration: fa.FlagDeclaration,
+		Value:           fa.Value,
+		Traces:          fa.Traces,
+	}, nil
+}
diff --git a/cmd/release_config/release_config_lib/flag_declaration.go b/cmd/release_config/release_config_lib/flag_declaration.go
new file mode 100644
index 0000000..d5cc418
--- /dev/null
+++ b/cmd/release_config/release_config_lib/flag_declaration.go
@@ -0,0 +1,27 @@
+// Copyright 2024 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 release_config_lib
+
+import (
+	"android/soong/cmd/release_config/release_config_proto"
+)
+
+func FlagDeclarationFactory(protoPath string) (fd *release_config_proto.FlagDeclaration) {
+	fd = &release_config_proto.FlagDeclaration{}
+	if protoPath != "" {
+		LoadTextproto(protoPath, fd)
+	}
+	return fd
+}
diff --git a/cmd/release_config/release_config_lib/flag_value.go b/cmd/release_config/release_config_lib/flag_value.go
new file mode 100644
index 0000000..138e8f8
--- /dev/null
+++ b/cmd/release_config/release_config_lib/flag_value.go
@@ -0,0 +1,56 @@
+// Copyright 2024 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 release_config_lib
+
+import (
+	"android/soong/cmd/release_config/release_config_proto"
+)
+
+type FlagValue struct {
+	// The path providing this value.
+	path string
+
+	// Protobuf
+	proto release_config_proto.FlagValue
+}
+
+func FlagValueFactory(protoPath string) (fv *FlagValue) {
+	fv = &FlagValue{path: protoPath}
+	if protoPath != "" {
+		LoadTextproto(protoPath, &fv.proto)
+	}
+	return fv
+}
+
+func MarshalValue(value *release_config_proto.Value) string {
+	switch val := value.Val.(type) {
+	case *release_config_proto.Value_UnspecifiedValue:
+		// Value was never set.
+		return ""
+	case *release_config_proto.Value_StringValue:
+		return val.StringValue
+	case *release_config_proto.Value_BoolValue:
+		if val.BoolValue {
+			return "true"
+		}
+		// False ==> empty string
+		return ""
+	case *release_config_proto.Value_Obsolete:
+		return " #OBSOLETE"
+	default:
+		// Flagged as error elsewhere, so return empty string here.
+		return ""
+	}
+}
diff --git a/cmd/release_config/release_config_lib/flag_value_test.go b/cmd/release_config/release_config_lib/flag_value_test.go
new file mode 100644
index 0000000..aaa4caf
--- /dev/null
+++ b/cmd/release_config/release_config_lib/flag_value_test.go
@@ -0,0 +1,67 @@
+// Copyright 2024 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 release_config_lib
+
+import (
+	"os"
+	"path/filepath"
+	"testing"
+
+	rc_proto "android/soong/cmd/release_config/release_config_proto"
+
+	"google.golang.org/protobuf/proto"
+)
+
+type testCaseFlagValue struct {
+	protoPath string
+	name      string
+	data      []byte
+	expected  rc_proto.FlagValue
+	err       error
+}
+
+func (tc testCaseFlagValue) assertProtoEqual(t *testing.T, expected, actual proto.Message) {
+	if !proto.Equal(expected, actual) {
+		t.Errorf("Expected %q found %q", expected, actual)
+	}
+}
+
+func TestFlagValue(t *testing.T) {
+	testCases := []testCaseFlagValue{
+		{
+			name:      "stringVal",
+			protoPath: "build/release/flag_values/test/RELEASE_FOO.textproto",
+			data:      []byte(`name: "RELEASE_FOO" value {string_value: "BAR"}`),
+			expected: rc_proto.FlagValue{
+				Name:  proto.String("RELEASE_FOO"),
+				Value: &rc_proto.Value{Val: &rc_proto.Value_StringValue{"BAR"}},
+			},
+			err: nil,
+		},
+	}
+	for _, tc := range testCases {
+		var err error
+		tempdir := t.TempDir()
+		path := filepath.Join(tempdir, tc.protoPath)
+		if err = os.MkdirAll(filepath.Dir(path), 0755); err != nil {
+			t.Fatal(err)
+		}
+		if err = os.WriteFile(path, tc.data, 0644); err != nil {
+			t.Fatal(err)
+		}
+		actual := FlagValueFactory(path)
+		tc.assertProtoEqual(t, &tc.expected, &actual.proto)
+	}
+}
diff --git a/cmd/release_config/release_config_lib/release_config.go b/cmd/release_config/release_config_lib/release_config.go
new file mode 100644
index 0000000..3110dae
--- /dev/null
+++ b/cmd/release_config/release_config_lib/release_config.go
@@ -0,0 +1,154 @@
+// Copyright 2024 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 release_config_lib
+
+import (
+	"fmt"
+
+	"android/soong/cmd/release_config/release_config_proto"
+
+	"google.golang.org/protobuf/proto"
+)
+
+// One directory's contribution to the a release config.
+type ReleaseConfigContribution struct {
+	// Paths to files providing this config.
+	path string
+
+	// The index of the config directory where this release config
+	// contribution was declared.
+	// Flag values cannot be set in a location with a lower index.
+	DeclarationIndex int
+
+	// Protobufs relevant to the config.
+	proto release_config_proto.ReleaseConfig
+
+	FlagValues []*FlagValue
+}
+
+// A generated release config.
+type ReleaseConfig struct {
+	// the Name of the release config
+	Name string
+
+	// The index of the config directory where this release config was
+	// first declared.
+	// Flag values cannot be set in a location with a lower index.
+	DeclarationIndex int
+
+	// What contributes to this config.
+	Contributions []*ReleaseConfigContribution
+
+	// Aliases for this release
+	OtherNames []string
+
+	// The names of release configs that we inherit
+	InheritNames []string
+
+	// Unmarshalled flag artifacts
+	FlagArtifacts FlagArtifacts
+
+	// Generated release config
+	ReleaseConfigArtifact *release_config_proto.ReleaseConfigArtifact
+
+	// We have begun compiling this release config.
+	compileInProgress bool
+}
+
+func ReleaseConfigFactory(name string, index int) (c *ReleaseConfig) {
+	return &ReleaseConfig{Name: name, DeclarationIndex: index}
+}
+
+func (config *ReleaseConfig) GenerateReleaseConfig(configs *ReleaseConfigs) error {
+	if config.ReleaseConfigArtifact != nil {
+		return nil
+	}
+	if config.compileInProgress {
+		return fmt.Errorf("Loop detected for release config %s", config.Name)
+	}
+	config.compileInProgress = true
+
+	// Generate any configs we need to inherit.  This will detect loops in
+	// the config.
+	contributionsToApply := []*ReleaseConfigContribution{}
+	myInherits := []string{}
+	myInheritsSet := make(map[string]bool)
+	for _, inherit := range config.InheritNames {
+		if _, ok := myInheritsSet[inherit]; ok {
+			continue
+		}
+		myInherits = append(myInherits, inherit)
+		myInheritsSet[inherit] = true
+		iConfig, err := configs.GetReleaseConfig(inherit)
+		if err != nil {
+			return err
+		}
+		iConfig.GenerateReleaseConfig(configs)
+		contributionsToApply = append(contributionsToApply, iConfig.Contributions...)
+	}
+	contributionsToApply = append(contributionsToApply, config.Contributions...)
+
+	myAconfigValueSets := []string{}
+	myFlags := configs.FlagArtifacts.Clone()
+	myDirsMap := make(map[int]bool)
+	for _, contrib := range contributionsToApply {
+		myAconfigValueSets = append(myAconfigValueSets, contrib.proto.AconfigValueSets...)
+		myDirsMap[contrib.DeclarationIndex] = true
+		for _, value := range contrib.FlagValues {
+			fa, ok := myFlags[*value.proto.Name]
+			if !ok {
+				return fmt.Errorf("Setting value for undefined flag %s in %s\n", *value.proto.Name, value.path)
+			}
+			myDirsMap[fa.DeclarationIndex] = true
+			if fa.DeclarationIndex > contrib.DeclarationIndex {
+				// Setting location is to the left of declaration.
+				return fmt.Errorf("Setting value for flag %s not allowed in %s\n", *value.proto.Name, value.path)
+			}
+			if err := fa.UpdateValue(*value); err != nil {
+				return err
+			}
+		}
+	}
+
+	directories := []string{}
+	for idx, confDir := range configs.ConfigDirs {
+		if _, ok := myDirsMap[idx]; ok {
+			directories = append(directories, confDir)
+		}
+	}
+
+	config.FlagArtifacts = myFlags
+	config.ReleaseConfigArtifact = &release_config_proto.ReleaseConfigArtifact{
+		Name:       proto.String(config.Name),
+		OtherNames: config.OtherNames,
+		FlagArtifacts: func() []*release_config_proto.FlagArtifact {
+			ret := []*release_config_proto.FlagArtifact{}
+			for _, flag := range myFlags {
+				ret = append(ret, &release_config_proto.FlagArtifact{
+					FlagDeclaration: flag.FlagDeclaration,
+					Traces:          flag.Traces,
+					Value:           flag.Value,
+				})
+			}
+			return ret
+		}(),
+		AconfigValueSets: myAconfigValueSets,
+		Inherits:         myInherits,
+		Directories:      directories,
+	}
+
+	config.compileInProgress = false
+	return nil
+}
diff --git a/cmd/release_config/release_config_lib/release_configs.go b/cmd/release_config/release_config_lib/release_configs.go
new file mode 100644
index 0000000..74fdc00
--- /dev/null
+++ b/cmd/release_config/release_config_lib/release_configs.go
@@ -0,0 +1,365 @@
+// Copyright 2024 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 release_config_lib
+
+import (
+	"cmp"
+	"encoding/json"
+	"fmt"
+	"io/fs"
+	"os"
+	"path/filepath"
+	"slices"
+	"strings"
+
+	"android/soong/cmd/release_config/release_config_proto"
+
+	"google.golang.org/protobuf/encoding/prototext"
+	"google.golang.org/protobuf/proto"
+)
+
+// A single release_config_map.textproto and its associated data.
+// Used primarily for debugging.
+type ReleaseConfigMap struct {
+	// The path to this release_config_map file.
+	path string
+
+	// Data received
+	proto release_config_proto.ReleaseConfigMap
+
+	ReleaseConfigContributions map[string]*ReleaseConfigContribution
+	FlagDeclarations           []release_config_proto.FlagDeclaration
+}
+
+type ReleaseConfigDirMap map[string]int
+
+// The generated release configs.
+type ReleaseConfigs struct {
+	// Ordered list of release config maps processed.
+	ReleaseConfigMaps []*ReleaseConfigMap
+
+	// Aliases
+	Aliases map[string]*string
+
+	// Dictionary of flag_name:FlagDeclaration, with no overrides applied.
+	FlagArtifacts FlagArtifacts
+
+	// Dictionary of name:ReleaseConfig
+	ReleaseConfigs map[string]*ReleaseConfig
+
+	// Generated release configs
+	Artifact release_config_proto.ReleaseConfigsArtifact
+
+	// The list of config directories used.
+	ConfigDirs []string
+
+	// A map from the config directory to its order in the list of config
+	// directories.
+	ConfigDirIndexes ReleaseConfigDirMap
+}
+
+func (configs *ReleaseConfigs) DumpArtifact(outDir string) error {
+	message := &configs.Artifact
+	basePath := filepath.Join(outDir, "all_release_configs")
+	writer := func(suffix string, marshal func() ([]byte, error)) error {
+		data, err := marshal()
+		if err != nil {
+			return err
+		}
+		return os.WriteFile(fmt.Sprintf("%s.%s", basePath, suffix), data, 0644)
+	}
+	err := writer("textproto", func() ([]byte, error) { return prototext.MarshalOptions{Multiline: true}.Marshal(message) })
+	if err != nil {
+		return err
+	}
+
+	err = writer("pb", func() ([]byte, error) { return proto.Marshal(message) })
+	if err != nil {
+		return err
+	}
+
+	return writer("json", func() ([]byte, error) { return json.MarshalIndent(message, "", "  ") })
+}
+
+func ReleaseConfigsFactory() (c *ReleaseConfigs) {
+	return &ReleaseConfigs{
+		Aliases:          make(map[string]*string),
+		FlagArtifacts:    make(map[string]*FlagArtifact),
+		ReleaseConfigs:   make(map[string]*ReleaseConfig),
+		ConfigDirs:       []string{},
+		ConfigDirIndexes: make(ReleaseConfigDirMap),
+	}
+}
+
+func ReleaseConfigMapFactory(protoPath string) (m *ReleaseConfigMap) {
+	m = &ReleaseConfigMap{
+		path:                       protoPath,
+		ReleaseConfigContributions: make(map[string]*ReleaseConfigContribution),
+	}
+	if protoPath != "" {
+		LoadTextproto(protoPath, &m.proto)
+	}
+	return m
+}
+
+func (configs *ReleaseConfigs) LoadReleaseConfigMap(path string, ConfigDirIndex int) error {
+	m := ReleaseConfigMapFactory(path)
+	if m.proto.DefaultContainer == nil {
+		return fmt.Errorf("Release config map %s lacks default_container", path)
+	}
+	dir := filepath.Dir(path)
+	// Record any aliases, checking for duplicates.
+	for _, alias := range m.proto.Aliases {
+		name := *alias.Name
+		oldTarget, ok := configs.Aliases[name]
+		if ok {
+			if *oldTarget != *alias.Target {
+				return fmt.Errorf("Conflicting alias declarations: %s vs %s",
+					*oldTarget, *alias.Target)
+			}
+		}
+		configs.Aliases[name] = alias.Target
+	}
+	var err error
+	err = WalkTextprotoFiles(dir, "flag_declarations", func(path string, d fs.DirEntry, err error) error {
+		flagDeclaration := FlagDeclarationFactory(path)
+		// Container must be specified.
+		if flagDeclaration.Container == nil {
+			flagDeclaration.Container = m.proto.DefaultContainer
+		}
+		// TODO: once we have namespaces initialized, we can throw an error here.
+		if flagDeclaration.Namespace == nil {
+			flagDeclaration.Namespace = proto.String("android_UNKNOWN")
+		}
+		// If the input didn't specify a value, create one (== UnspecifiedValue).
+		if flagDeclaration.Value == nil {
+			flagDeclaration.Value = &release_config_proto.Value{Val: &release_config_proto.Value_UnspecifiedValue{false}}
+		}
+		m.FlagDeclarations = append(m.FlagDeclarations, *flagDeclaration)
+		name := *flagDeclaration.Name
+		if def, ok := configs.FlagArtifacts[name]; !ok {
+			configs.FlagArtifacts[name] = &FlagArtifact{FlagDeclaration: flagDeclaration, DeclarationIndex: ConfigDirIndex}
+		} else if !proto.Equal(def.FlagDeclaration, flagDeclaration) {
+			return fmt.Errorf("Duplicate definition of %s", *flagDeclaration.Name)
+		}
+		// Set the initial value in the flag artifact.
+		configs.FlagArtifacts[name].UpdateValue(
+			FlagValue{path: path, proto: release_config_proto.FlagValue{
+				Name: proto.String(name), Value: flagDeclaration.Value}})
+		return nil
+	})
+	if err != nil {
+		return err
+	}
+
+	err = WalkTextprotoFiles(dir, "release_configs", func(path string, d fs.DirEntry, err error) error {
+		releaseConfigContribution := &ReleaseConfigContribution{path: path, DeclarationIndex: ConfigDirIndex}
+		LoadTextproto(path, &releaseConfigContribution.proto)
+		name := *releaseConfigContribution.proto.Name
+		if fmt.Sprintf("%s.textproto", name) != filepath.Base(path) {
+			return fmt.Errorf("%s incorrectly declares release config %s", path, name)
+		}
+		if _, ok := configs.ReleaseConfigs[name]; !ok {
+			configs.ReleaseConfigs[name] = ReleaseConfigFactory(name, ConfigDirIndex)
+		}
+		config := configs.ReleaseConfigs[name]
+		config.InheritNames = append(config.InheritNames, releaseConfigContribution.proto.Inherits...)
+
+		// Only walk flag_values/{RELEASE} for defined releases.
+		err2 := WalkTextprotoFiles(dir, filepath.Join("flag_values", name), func(path string, d fs.DirEntry, err error) error {
+			flagValue := FlagValueFactory(path)
+			if fmt.Sprintf("%s.textproto", *flagValue.proto.Name) != filepath.Base(path) {
+				return fmt.Errorf("%s incorrectly sets value for flag %s", path, *flagValue.proto.Name)
+			}
+			releaseConfigContribution.FlagValues = append(releaseConfigContribution.FlagValues, flagValue)
+			return nil
+		})
+		if err2 != nil {
+			return err2
+		}
+		m.ReleaseConfigContributions[name] = releaseConfigContribution
+		config.Contributions = append(config.Contributions, releaseConfigContribution)
+		return nil
+	})
+	if err != nil {
+		return err
+	}
+	configs.ReleaseConfigMaps = append(configs.ReleaseConfigMaps, m)
+	return nil
+}
+
+func (configs *ReleaseConfigs) GetReleaseConfig(name string) (*ReleaseConfig, error) {
+	trace := []string{name}
+	for target, ok := configs.Aliases[name]; ok; target, ok = configs.Aliases[name] {
+		name = *target
+		trace = append(trace, name)
+	}
+	if config, ok := configs.ReleaseConfigs[name]; ok {
+		return config, nil
+	}
+	return nil, fmt.Errorf("Missing config %s.  Trace=%v", name, trace)
+}
+
+func (configs *ReleaseConfigs) DumpMakefile(outDir, targetRelease string) error {
+	outFile := filepath.Join(outDir, "release_config.mk")
+	makeVars := make(map[string]string)
+	config, err := configs.GetReleaseConfig(targetRelease)
+	if err != nil {
+		return err
+	}
+	// Sort the flags by name first.
+	names := []string{}
+	for k, _ := range config.FlagArtifacts {
+		names = append(names, k)
+	}
+	slices.SortFunc(names, func(a, b string) int {
+		return cmp.Compare(a, b)
+	})
+	partitions := make(map[string][]string)
+
+	vNames := []string{}
+	addVar := func(name, suffix, value string) {
+		fullName := fmt.Sprintf("_ALL_RELEASE_FLAGS.%s.%s", name, suffix)
+		vNames = append(vNames, fullName)
+		makeVars[fullName] = value
+	}
+
+	for _, name := range names {
+		flag := config.FlagArtifacts[name]
+		decl := flag.FlagDeclaration
+
+		// cName := strings.ToLower(release_config_proto.Container_name[decl.GetContainer()])
+		cName := strings.ToLower(decl.Container.String())
+		if cName == strings.ToLower(release_config_proto.Container_ALL.String()) {
+			partitions["product"] = append(partitions["product"], name)
+			partitions["system"] = append(partitions["system"], name)
+			partitions["system_ext"] = append(partitions["system_ext"], name)
+			partitions["vendor"] = append(partitions["vendor"], name)
+		} else {
+			partitions[cName] = append(partitions[cName], name)
+		}
+		value := MarshalValue(flag.Value)
+		makeVars[name] = value
+		addVar(name, "PARTITIONS", cName)
+		addVar(name, "DEFAULT", MarshalValue(decl.Value))
+		addVar(name, "VALUE", value)
+		addVar(name, "DECLARED_IN", *flag.Traces[0].Source)
+		addVar(name, "SET_IN", *flag.Traces[len(flag.Traces)-1].Source)
+		addVar(name, "NAMESPACE", *decl.Namespace)
+	}
+	pNames := []string{}
+	for k, _ := range partitions {
+		pNames = append(pNames, k)
+	}
+	slices.SortFunc(pNames, func(a, b string) int {
+		return cmp.Compare(a, b)
+	})
+
+	// Now sort the make variables, and output them.
+	slices.SortFunc(vNames, func(a, b string) int {
+		return cmp.Compare(a, b)
+	})
+
+	// Write the flags as:
+	//   _ALL_RELELASE_FLAGS
+	//   _ALL_RELEASE_FLAGS.PARTITIONS.*
+	//   all _ALL_RELEASE_FLAGS.*, sorted by name
+	//   Final flag values, sorted by name.
+	data := fmt.Sprintf("_ALL_RELEASE_FLAGS :=$= %s\n", strings.Join(names, " "))
+	for _, pName := range pNames {
+		data += fmt.Sprintf("_ALL_RELEASE_FLAGS.PARTITIONS.%s :=$= %s\n", pName, strings.Join(partitions[pName], " "))
+	}
+	for _, vName := range vNames {
+		data += fmt.Sprintf("%s :=$= %s\n", vName, makeVars[vName])
+	}
+	data += "\n\n# Values for all build flags\n"
+	data += fmt.Sprintf("RELEASE_ACONFIG_VALUE_SETS :=$= %s\n",
+		strings.Join(config.ReleaseConfigArtifact.AconfigValueSets, " "))
+	for _, name := range names {
+		data += fmt.Sprintf("%s :=$= %s\n", name, makeVars[name])
+	}
+	return os.WriteFile(outFile, []byte(data), 0644)
+}
+
+func (configs *ReleaseConfigs) GenerateReleaseConfigs(targetRelease string) error {
+	otherNames := make(map[string][]string)
+	for aliasName, aliasTarget := range configs.Aliases {
+		if _, ok := configs.ReleaseConfigs[aliasName]; ok {
+			return fmt.Errorf("Alias %s is a declared release config", aliasName)
+		}
+		if _, ok := configs.ReleaseConfigs[*aliasTarget]; !ok {
+			if _, ok2 := configs.Aliases[*aliasTarget]; !ok2 {
+				return fmt.Errorf("Alias %s points to non-existing config %s", aliasName, *aliasTarget)
+			}
+		}
+		otherNames[*aliasTarget] = append(otherNames[*aliasTarget], aliasName)
+	}
+	for name, aliases := range otherNames {
+		configs.ReleaseConfigs[name].OtherNames = aliases
+	}
+
+	for _, config := range configs.ReleaseConfigs {
+		err := config.GenerateReleaseConfig(configs)
+		if err != nil {
+			return err
+		}
+	}
+
+	releaseConfig, err := configs.GetReleaseConfig(targetRelease)
+	if err != nil {
+		return err
+	}
+	configs.Artifact = release_config_proto.ReleaseConfigsArtifact{
+		ReleaseConfig: releaseConfig.ReleaseConfigArtifact,
+		OtherReleaseConfigs: func() []*release_config_proto.ReleaseConfigArtifact {
+			orc := []*release_config_proto.ReleaseConfigArtifact{}
+			for name, config := range configs.ReleaseConfigs {
+				if name != releaseConfig.Name {
+					orc = append(orc, config.ReleaseConfigArtifact)
+				}
+			}
+			return orc
+		}(),
+	}
+	return nil
+}
+
+func ReadReleaseConfigMaps(releaseConfigMapPaths StringList, targetRelease string) (*ReleaseConfigs, error) {
+	var err error
+
+	if len(releaseConfigMapPaths) == 0 {
+		releaseConfigMapPaths = GetDefaultMapPaths()
+		if len(releaseConfigMapPaths) == 0 {
+			return nil, fmt.Errorf("No maps found")
+		}
+		fmt.Printf("No --map argument provided.  Using: --map %s\n", strings.Join(releaseConfigMapPaths, " --map "))
+	}
+
+	configs := ReleaseConfigsFactory()
+	for idx, releaseConfigMapPath := range releaseConfigMapPaths {
+		// Maintain an ordered list of release config directories.
+		configDir := filepath.Dir(releaseConfigMapPath)
+		configs.ConfigDirIndexes[configDir] = idx
+		configs.ConfigDirs = append(configs.ConfigDirs, configDir)
+		err = configs.LoadReleaseConfigMap(releaseConfigMapPath, idx)
+		if err != nil {
+			return nil, err
+		}
+	}
+
+	// Now that we have all of the release config maps, can meld them and generate the artifacts.
+	err = configs.GenerateReleaseConfigs(targetRelease)
+	return configs, err
+}
diff --git a/cmd/release_config/release_config_lib/util.go b/cmd/release_config/release_config_lib/util.go
new file mode 100644
index 0000000..c59deb3
--- /dev/null
+++ b/cmd/release_config/release_config_lib/util.go
@@ -0,0 +1,90 @@
+// Copyright 2024 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 release_config_lib
+
+import (
+	"fmt"
+	"io/fs"
+	"os"
+	"path/filepath"
+	"strings"
+
+	"google.golang.org/protobuf/encoding/prototext"
+	"google.golang.org/protobuf/proto"
+)
+
+type StringList []string
+
+func (l *StringList) Set(v string) error {
+	*l = append(*l, v)
+	return nil
+}
+
+func (l *StringList) String() string {
+	return fmt.Sprintf("%v", *l)
+}
+
+func LoadTextproto(path string, message proto.Message) error {
+	data, err := os.ReadFile(path)
+	if err != nil {
+		return err
+	}
+	ret := prototext.Unmarshal(data, message)
+	return ret
+}
+
+func WalkTextprotoFiles(root string, subdir string, Func fs.WalkDirFunc) error {
+	path := filepath.Join(root, subdir)
+	if _, err := os.Stat(path); err != nil {
+		// Missing subdirs are not an error.
+		return nil
+	}
+	return filepath.WalkDir(path, func(path string, d fs.DirEntry, err error) error {
+		if err != nil {
+			return err
+		}
+		if strings.HasSuffix(d.Name(), ".textproto") && d.Type().IsRegular() {
+			return Func(path, d, err)
+		}
+		return nil
+	})
+}
+
+func GetDefaultOutDir() string {
+	outEnv := os.Getenv("OUT_DIR")
+	if outEnv == "" {
+		outEnv = "out"
+	}
+	return filepath.Join(outEnv, "soong", "release-config")
+}
+
+func GetDefaultMapPaths() StringList {
+	var defaultMapPaths StringList
+	defaultLocations := StringList{
+		"build/release/release_config_map.textproto",
+		"vendor/google_shared/build/release/release_config_map.textproto",
+		"vendor/google/release/release_config_map.textproto",
+	}
+	for _, path := range defaultLocations {
+		if _, err := os.Stat(path); err == nil {
+			defaultMapPaths = append(defaultMapPaths, path)
+		}
+	}
+	prodMaps := os.Getenv("PRODUCT_RELEASE_CONFIG_MAPS")
+	if prodMaps != "" {
+		defaultMapPaths = append(defaultMapPaths, strings.Split(prodMaps, " ")...)
+	}
+	return defaultMapPaths
+}
diff --git a/cmd/release_config/release_config_proto/Android.bp b/cmd/release_config/release_config_proto/Android.bp
index a8660c7..5a6aeab 100644
--- a/cmd/release_config/release_config_proto/Android.bp
+++ b/cmd/release_config/release_config_proto/Android.bp
@@ -17,7 +17,7 @@
 }
 
 bootstrap_go_package {
-    name: "soong-release_config_proto",
+    name: "soong-cmd-release_config-proto",
     pkgPath: "android/soong/release_config/release_config_proto",
     deps: [
         "golang-protobuf-reflect-protoreflect",
diff --git a/cmd/release_config/release_config_proto/build_flags_src.pb.go b/cmd/release_config/release_config_proto/build_flags_src.pb.go
index 0f2c30b..ccf3b3f 100644
--- a/cmd/release_config/release_config_proto/build_flags_src.pb.go
+++ b/cmd/release_config/release_config_proto/build_flags_src.pb.go
@@ -287,6 +287,9 @@
 	// The name of the flag.
 	// See # name for format detail
 	Name *string `protobuf:"bytes,1,opt,name=name" json:"name,omitempty"`
+	// Namespace the flag belongs to (required)
+	// See # namespace for format detail
+	Namespace *string `protobuf:"bytes,2,opt,name=namespace" json:"namespace,omitempty"`
 	// Text description of the flag's purpose.
 	Description *string `protobuf:"bytes,3,opt,name=description" json:"description,omitempty"`
 	// Value for the flag
@@ -296,9 +299,6 @@
 	// The container for this flag.  This overrides any default container given
 	// in the release_config_map message.
 	Container *Container `protobuf:"varint,206,opt,name=container,enum=android.release_config_proto.Container" json:"container,omitempty"`
-	// Temporarily allow origin at the flag declaration level while we
-	// move flags to their own locations.
-	Origin *string `protobuf:"bytes,208,opt,name=origin" json:"origin,omitempty"`
 }
 
 func (x *FlagDeclaration) Reset() {
@@ -340,6 +340,13 @@
 	return ""
 }
 
+func (x *FlagDeclaration) GetNamespace() string {
+	if x != nil && x.Namespace != nil {
+		return *x.Namespace
+	}
+	return ""
+}
+
 func (x *FlagDeclaration) GetDescription() string {
 	if x != nil && x.Description != nil {
 		return *x.Description
@@ -368,13 +375,6 @@
 	return Container_UNSPECIFIED_container
 }
 
-func (x *FlagDeclaration) GetOrigin() string {
-	if x != nil && x.Origin != nil {
-		return *x.Origin
-	}
-	return ""
-}
-
 type FlagValue struct {
 	state         protoimpl.MessageState
 	sizeCache     protoimpl.SizeCache
@@ -568,8 +568,6 @@
 
 	// Any aliases.
 	Aliases []*ReleaseAlias `protobuf:"bytes,1,rep,name=aliases" json:"aliases,omitempty"`
-	// The origin for flags declared here.
-	Origin *string `protobuf:"bytes,2,opt,name=origin" json:"origin,omitempty"`
 	// The default container for flags declared here.
 	DefaultContainer *Container `protobuf:"varint,3,opt,name=default_container,json=defaultContainer,enum=android.release_config_proto.Container" json:"default_container,omitempty"`
 }
@@ -613,13 +611,6 @@
 	return nil
 }
 
-func (x *ReleaseConfigMap) GetOrigin() string {
-	if x != nil && x.Origin != nil {
-		return *x.Origin
-	}
-	return ""
-}
-
 func (x *ReleaseConfigMap) GetDefaultContainer() Container {
 	if x != nil && x.DefaultContainer != nil {
 		return *x.DefaultContainer
@@ -643,71 +634,70 @@
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+	0x3a, 0x0a, 0x05, 0x76, 0x61, 0x6c, 0x75, 0x65, 0x18, 0xc9, 0x01, 0x20, 0x01, 0x28, 0x0b, 0x32,
+	0x23, 0x2e, 0x61, 0x6e, 0x64, 0x72, 0x6f, 0x69, 0x64, 0x2e, 0x72, 0x65, 0x6c, 0x65, 0x61, 0x73,
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+	0x65, 0x6c, 0x65, 0x61, 0x73, 0x65, 0x5f, 0x63, 0x6f, 0x6e, 0x66, 0x69, 0x67, 0x12, 0x12, 0x0a,
+	0x04, 0x6e, 0x61, 0x6d, 0x65, 0x18, 0x01, 0x20, 0x01, 0x28, 0x09, 0x52, 0x04, 0x6e, 0x61, 0x6d,
+	0x65, 0x12, 0x1a, 0x0a, 0x08, 0x69, 0x6e, 0x68, 0x65, 0x72, 0x69, 0x74, 0x73, 0x18, 0x02, 0x20,
+	0x03, 0x28, 0x09, 0x52, 0x08, 0x69, 0x6e, 0x68, 0x65, 0x72, 0x69, 0x74, 0x73, 0x12, 0x2c, 0x0a,
+	0x12, 0x61, 0x63, 0x6f, 0x6e, 0x66, 0x69, 0x67, 0x5f, 0x76, 0x61, 0x6c, 0x75, 0x65, 0x5f, 0x73,
+	0x65, 0x74, 0x73, 0x18, 0x03, 0x20, 0x03, 0x28, 0x09, 0x52, 0x10, 0x61, 0x63, 0x6f, 0x6e, 0x66,
+	0x69, 0x67, 0x56, 0x61, 0x6c, 0x75, 0x65, 0x53, 0x65, 0x74, 0x73, 0x22, 0x3b, 0x0a, 0x0d, 0x72,
+	0x65, 0x6c, 0x65, 0x61, 0x73, 0x65, 0x5f, 0x61, 0x6c, 0x69, 0x61, 0x73, 0x12, 0x12, 0x0a, 0x04,
+	0x6e, 0x61, 0x6d, 0x65, 0x18, 0x01, 0x20, 0x01, 0x28, 0x09, 0x52, 0x04, 0x6e, 0x61, 0x6d, 0x65,
+	0x12, 0x16, 0x0a, 0x06, 0x74, 0x61, 0x72, 0x67, 0x65, 0x74, 0x18, 0x02, 0x20, 0x01, 0x28, 0x09,
+	0x52, 0x06, 0x74, 0x61, 0x72, 0x67, 0x65, 0x74, 0x22, 0xb1, 0x01, 0x0a, 0x12, 0x72, 0x65, 0x6c,
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+	0x45, 0x0a, 0x07, 0x61, 0x6c, 0x69, 0x61, 0x73, 0x65, 0x73, 0x18, 0x01, 0x20, 0x03, 0x28, 0x0b,
+	0x32, 0x2b, 0x2e, 0x61, 0x6e, 0x64, 0x72, 0x6f, 0x69, 0x64, 0x2e, 0x72, 0x65, 0x6c, 0x65, 0x61,
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+	0x6c, 0x69, 0x61, 0x73, 0x65, 0x73, 0x12, 0x54, 0x0a, 0x11, 0x64, 0x65, 0x66, 0x61, 0x75, 0x6c,
+	0x74, 0x5f, 0x63, 0x6f, 0x6e, 0x74, 0x61, 0x69, 0x6e, 0x65, 0x72, 0x18, 0x03, 0x20, 0x01, 0x28,
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+	0x77, 0x6f, 0x72, 0x6b, 0x66, 0x6c, 0x6f, 0x77, 0x12, 0x18, 0x0a, 0x14, 0x55, 0x4e, 0x53, 0x50,
+	0x45, 0x43, 0x49, 0x46, 0x49, 0x45, 0x44, 0x5f, 0x77, 0x6f, 0x72, 0x6b, 0x66, 0x6c, 0x6f, 0x77,
+	0x10, 0x00, 0x12, 0x0a, 0x0a, 0x06, 0x4c, 0x41, 0x55, 0x4e, 0x43, 0x48, 0x10, 0x01, 0x12, 0x0c,
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+	0x4d, 0x41, 0x4e, 0x55, 0x41, 0x4c, 0x10, 0x03, 0x2a, 0x64, 0x0a, 0x09, 0x63, 0x6f, 0x6e, 0x74,
+	0x61, 0x69, 0x6e, 0x65, 0x72, 0x12, 0x19, 0x0a, 0x15, 0x55, 0x4e, 0x53, 0x50, 0x45, 0x43, 0x49,
+	0x46, 0x49, 0x45, 0x44, 0x5f, 0x63, 0x6f, 0x6e, 0x74, 0x61, 0x69, 0x6e, 0x65, 0x72, 0x10, 0x00,
+	0x12, 0x07, 0x0a, 0x03, 0x41, 0x4c, 0x4c, 0x10, 0x01, 0x12, 0x0b, 0x0a, 0x07, 0x50, 0x52, 0x4f,
+	0x44, 0x55, 0x43, 0x54, 0x10, 0x02, 0x12, 0x0a, 0x0a, 0x06, 0x53, 0x59, 0x53, 0x54, 0x45, 0x4d,
+	0x10, 0x03, 0x12, 0x0e, 0x0a, 0x0a, 0x53, 0x59, 0x53, 0x54, 0x45, 0x4d, 0x5f, 0x45, 0x58, 0x54,
+	0x10, 0x04, 0x12, 0x0a, 0x0a, 0x06, 0x56, 0x45, 0x4e, 0x44, 0x4f, 0x52, 0x10, 0x05, 0x42, 0x33,
+	0x5a, 0x31, 0x61, 0x6e, 0x64, 0x72, 0x6f, 0x69, 0x64, 0x2f, 0x73, 0x6f, 0x6f, 0x6e, 0x67, 0x2f,
+	0x72, 0x65, 0x6c, 0x65, 0x61, 0x73, 0x65, 0x5f, 0x63, 0x6f, 0x6e, 0x66, 0x69, 0x67, 0x2f, 0x72,
 	0x65, 0x6c, 0x65, 0x61, 0x73, 0x65, 0x5f, 0x63, 0x6f, 0x6e, 0x66, 0x69, 0x67, 0x5f, 0x70, 0x72,
-	0x6f, 0x74, 0x6f, 0x2e, 0x63, 0x6f, 0x6e, 0x74, 0x61, 0x69, 0x6e, 0x65, 0x72, 0x52, 0x10, 0x64,
-	0x65, 0x66, 0x61, 0x75, 0x6c, 0x74, 0x43, 0x6f, 0x6e, 0x74, 0x61, 0x69, 0x6e, 0x65, 0x72, 0x2a,
-	0x4a, 0x0a, 0x08, 0x77, 0x6f, 0x72, 0x6b, 0x66, 0x6c, 0x6f, 0x77, 0x12, 0x18, 0x0a, 0x14, 0x55,
-	0x4e, 0x53, 0x50, 0x45, 0x43, 0x49, 0x46, 0x49, 0x45, 0x44, 0x5f, 0x77, 0x6f, 0x72, 0x6b, 0x66,
-	0x6c, 0x6f, 0x77, 0x10, 0x00, 0x12, 0x0a, 0x0a, 0x06, 0x4c, 0x41, 0x55, 0x4e, 0x43, 0x48, 0x10,
-	0x01, 0x12, 0x0c, 0x0a, 0x08, 0x50, 0x52, 0x45, 0x42, 0x55, 0x49, 0x4c, 0x54, 0x10, 0x02, 0x12,
-	0x0a, 0x0a, 0x06, 0x4d, 0x41, 0x4e, 0x55, 0x41, 0x4c, 0x10, 0x03, 0x2a, 0x64, 0x0a, 0x09, 0x63,
-	0x6f, 0x6e, 0x74, 0x61, 0x69, 0x6e, 0x65, 0x72, 0x12, 0x19, 0x0a, 0x15, 0x55, 0x4e, 0x53, 0x50,
-	0x45, 0x43, 0x49, 0x46, 0x49, 0x45, 0x44, 0x5f, 0x63, 0x6f, 0x6e, 0x74, 0x61, 0x69, 0x6e, 0x65,
-	0x72, 0x10, 0x00, 0x12, 0x07, 0x0a, 0x03, 0x41, 0x4c, 0x4c, 0x10, 0x01, 0x12, 0x0b, 0x0a, 0x07,
-	0x50, 0x52, 0x4f, 0x44, 0x55, 0x43, 0x54, 0x10, 0x02, 0x12, 0x0a, 0x0a, 0x06, 0x53, 0x59, 0x53,
-	0x54, 0x45, 0x4d, 0x10, 0x03, 0x12, 0x0e, 0x0a, 0x0a, 0x53, 0x59, 0x53, 0x54, 0x45, 0x4d, 0x5f,
-	0x45, 0x58, 0x54, 0x10, 0x04, 0x12, 0x0a, 0x0a, 0x06, 0x56, 0x45, 0x4e, 0x44, 0x4f, 0x52, 0x10,
-	0x05, 0x42, 0x33, 0x5a, 0x31, 0x61, 0x6e, 0x64, 0x72, 0x6f, 0x69, 0x64, 0x2f, 0x73, 0x6f, 0x6f,
-	0x6e, 0x67, 0x2f, 0x72, 0x65, 0x6c, 0x65, 0x61, 0x73, 0x65, 0x5f, 0x63, 0x6f, 0x6e, 0x66, 0x69,
-	0x67, 0x2f, 0x72, 0x65, 0x6c, 0x65, 0x61, 0x73, 0x65, 0x5f, 0x63, 0x6f, 0x6e, 0x66, 0x69, 0x67,
-	0x5f, 0x70, 0x72, 0x6f, 0x74, 0x6f,
+	0x6f, 0x74, 0x6f,
 }
 
 var (
diff --git a/cmd/release_config/release_config_proto/build_flags_src.proto b/cmd/release_config/release_config_proto/build_flags_src.proto
index 0662716..8501524 100644
--- a/cmd/release_config/release_config_proto/build_flags_src.proto
+++ b/cmd/release_config/release_config_proto/build_flags_src.proto
@@ -26,6 +26,11 @@
 //      RELEASE_MY_PACKAGE_FLAG is a valid name, while MY_PACKAGE_FLAG, and
 //      RELEASE_MY_PACKAGE__FLAG are invalid.
 //
+// # namespace: namespace the flag belongs to
+//
+//    format: a lowercase string in snake_case format, no consecutive underscores, and no leading
+//      digit. For example android_bar_system
+//
 // # package: package to which the flag belongs
 //
 //    format: lowercase strings in snake_case format, delimited by dots, no
@@ -77,6 +82,10 @@
   // See # name for format detail
   optional string name = 1;
 
+  // Namespace the flag belongs to (required)
+  // See # namespace for format detail
+  optional string namespace = 2;
+
   // Text description of the flag's purpose.
   optional string description = 3;
 
@@ -96,12 +105,6 @@
   // The package associated with this flag.
   // (when Gantry is ready for it) optional string package = 207;
   reserved 207;
-
-  // Temporarily allow origin at the flag declaration level while we
-  // move flags to their own locations.
-  optional string origin = 208;
-
-  // TODO: do we want to include "first used in" (= ap2a)?
 }
 
 message flag_value {
@@ -141,9 +144,6 @@
   // Any aliases.
   repeated release_alias aliases = 1;
 
-  // The origin for flags declared here.
-  optional string origin = 2;
-
   // The default container for flags declared here.
   optional container default_container = 3;
 
diff --git a/dexpreopt/class_loader_context.go b/dexpreopt/class_loader_context.go
index 57c7ae8..af1d33d 100644
--- a/dexpreopt/class_loader_context.go
+++ b/dexpreopt/class_loader_context.go
@@ -323,6 +323,7 @@
 		} else if clc.Host == hostPath && clc.Device == devicePath {
 			// Ok, the same library with the same paths. Don't re-add it, but don't raise an error
 			// either, as the same library may be reachable via different transitional dependencies.
+			clc.Optional = clc.Optional && optional
 			return nil
 		} else {
 			// Fail, as someone is trying to add the same library with different paths. This likely
diff --git a/java/aar.go b/java/aar.go
index a366267..f8955ce 100644
--- a/java/aar.go
+++ b/java/aar.go
@@ -356,12 +356,13 @@
 	forceNonFinalResourceIDs       bool
 	extraLinkFlags                 []string
 	aconfigTextFiles               android.Paths
+	usesLibrary                    *usesLibrary
 }
 
 func (a *aapt) buildActions(ctx android.ModuleContext, opts aaptBuildActionOptions) {
 
 	staticResourcesNodesDepSet, sharedResourcesNodesDepSet, staticRRODirsDepSet, staticManifestsDepSet, sharedExportPackages, libFlags :=
-		aaptLibs(ctx, opts.sdkContext, opts.classLoaderContexts)
+		aaptLibs(ctx, opts.sdkContext, opts.classLoaderContexts, opts.usesLibrary)
 
 	// Exclude any libraries from the supplied list.
 	opts.classLoaderContexts = opts.classLoaderContexts.ExcludeLibs(opts.excludedLibs)
@@ -703,7 +704,8 @@
 }
 
 // aaptLibs collects libraries from dependencies and sdk_version and converts them into paths
-func aaptLibs(ctx android.ModuleContext, sdkContext android.SdkContext, classLoaderContexts dexpreopt.ClassLoaderContextMap) (
+func aaptLibs(ctx android.ModuleContext, sdkContext android.SdkContext,
+	classLoaderContexts dexpreopt.ClassLoaderContextMap, usesLibrary *usesLibrary) (
 	staticResourcesNodes, sharedResourcesNodes *android.DepSet[*resourcesNode], staticRRODirs *android.DepSet[rroDir],
 	staticManifests *android.DepSet[android.Path], sharedLibs android.Paths, flags []string) {
 
@@ -753,6 +755,9 @@
 		}
 
 		addCLCFromDep(ctx, module, classLoaderContexts)
+		if usesLibrary != nil {
+			addMissingOptionalUsesLibsFromDep(ctx, module, usesLibrary)
+		}
 	})
 
 	// AAPT2 overlays are in lowest to highest priority order, the topological order will be reversed later.
@@ -805,12 +810,12 @@
 var _ AndroidLibraryDependency = (*AndroidLibrary)(nil)
 
 func (a *AndroidLibrary) DepsMutator(ctx android.BottomUpMutatorContext) {
+	a.usesLibrary.deps(ctx, false)
 	a.Module.deps(ctx)
 	sdkDep := decodeSdkDep(ctx, android.SdkContext(a))
 	if sdkDep.hasFrameworkLibs() {
 		a.aapt.deps(ctx, sdkDep)
 	}
-	a.usesLibrary.deps(ctx, false)
 
 	for _, aconfig_declaration := range a.aaptProperties.Flags_packages {
 		ctx.AddDependency(ctx.Module(), aconfigDeclarationTag, aconfig_declaration)
@@ -829,6 +834,7 @@
 			classLoaderContexts:            a.classLoaderContexts,
 			enforceDefaultTargetSdkVersion: false,
 			aconfigTextFiles:               getAconfigFilePaths(ctx),
+			usesLibrary:                    &a.usesLibrary,
 		},
 	)
 
@@ -1215,7 +1221,7 @@
 	linkDeps = append(linkDeps, a.manifest)
 
 	staticResourcesNodesDepSet, sharedResourcesNodesDepSet, staticRRODirsDepSet, staticManifestsDepSet, sharedLibs, libFlags :=
-		aaptLibs(ctx, android.SdkContext(a), nil)
+		aaptLibs(ctx, android.SdkContext(a), nil, nil)
 
 	_ = sharedResourcesNodesDepSet
 	_ = staticRRODirsDepSet
@@ -1287,6 +1293,7 @@
 			}
 		}
 		addCLCFromDep(ctx, module, a.classLoaderContexts)
+		addMissingOptionalUsesLibsFromDep(ctx, module, &a.usesLibrary)
 	})
 
 	var implementationJarFile android.OutputPath
@@ -1405,6 +1412,12 @@
 
 var _ android.PrebuiltInterface = (*AARImport)(nil)
 
+func (a *AARImport) UsesLibrary() *usesLibrary {
+	return &a.usesLibrary
+}
+
+var _ ModuleWithUsesLibrary = (*AARImport)(nil)
+
 // android_library_import imports an `.aar` file into the build graph as if it was built with android_library.
 //
 // This module is not suitable for installing on a device, but can be used as a `static_libs` dependency of
diff --git a/java/app.go b/java/app.go
index 1aa3afe..50d1a2f 100644
--- a/java/app.go
+++ b/java/app.go
@@ -249,13 +249,13 @@
 }
 
 func (a *AndroidApp) DepsMutator(ctx android.BottomUpMutatorContext) {
-	a.Module.deps(ctx)
-
 	if String(a.appProperties.Stl) == "c++_shared" && !a.SdkVersion(ctx).Specified() {
 		ctx.PropertyErrorf("stl", "sdk_version must be set in order to use c++_shared")
 	}
 
 	sdkDep := decodeSdkDep(ctx, android.SdkContext(a))
+	a.usesLibrary.deps(ctx, sdkDep.hasFrameworkLibs())
+	a.Module.deps(ctx)
 	if sdkDep.hasFrameworkLibs() {
 		a.aapt.deps(ctx, sdkDep)
 	}
@@ -285,9 +285,6 @@
 		}
 		ctx.AddFarVariationDependencies(variation, jniLibTag, a.appProperties.Jni_libs...)
 	}
-
-	a.usesLibrary.deps(ctx, sdkDep.hasFrameworkLibs())
-
 	for _, aconfig_declaration := range a.aaptProperties.Flags_packages {
 		ctx.AddDependency(ctx.Module(), aconfigDeclarationTag, aconfig_declaration)
 	}
@@ -534,6 +531,7 @@
 			forceNonFinalResourceIDs:       nonFinalIds,
 			extraLinkFlags:                 aaptLinkFlags,
 			aconfigTextFiles:               getAconfigFilePaths(ctx),
+			usesLibrary:                    &a.usesLibrary,
 		},
 	)
 
@@ -815,18 +813,10 @@
 	// The decision to enforce <uses-library> checks is made before adding implicit SDK libraries.
 	a.usesLibrary.freezeEnforceUsesLibraries()
 
-	// Add implicit SDK libraries to <uses-library> list.
-	requiredUsesLibs, optionalUsesLibs := a.classLoaderContexts.UsesLibs()
-	for _, usesLib := range requiredUsesLibs {
-		a.usesLibrary.addLib(usesLib, false)
-	}
-	for _, usesLib := range optionalUsesLibs {
-		a.usesLibrary.addLib(usesLib, true)
-	}
-
 	// Check that the <uses-library> list is coherent with the manifest.
 	if a.usesLibrary.enforceUsesLibraries() {
-		manifestCheckFile := a.usesLibrary.verifyUsesLibrariesManifest(ctx, a.mergedManifestFile)
+		manifestCheckFile := a.usesLibrary.verifyUsesLibrariesManifest(
+			ctx, a.mergedManifestFile, &a.classLoaderContexts)
 		apkDeps = append(apkDeps, manifestCheckFile)
 	}
 
@@ -1596,6 +1586,9 @@
 	// provide the android.test.base statically and use jarjar to rename them so they do not collide
 	// with the classes provided by the android.test.base library.
 	Exclude_uses_libs []string
+
+	// The module names of optional uses-library libraries that are missing from the source tree.
+	Missing_optional_uses_libs []string `blueprint:"mutated"`
 }
 
 // usesLibrary provides properties and helper functions for AndroidApp and AndroidAppImport to verify that the
@@ -1612,20 +1605,11 @@
 	shouldDisableDexpreopt bool
 }
 
-func (u *usesLibrary) addLib(lib string, optional bool) {
-	if !android.InList(lib, u.usesLibraryProperties.Uses_libs) && !android.InList(lib, u.usesLibraryProperties.Optional_uses_libs) {
-		if optional {
-			u.usesLibraryProperties.Optional_uses_libs = append(u.usesLibraryProperties.Optional_uses_libs, lib)
-		} else {
-			u.usesLibraryProperties.Uses_libs = append(u.usesLibraryProperties.Uses_libs, lib)
-		}
-	}
-}
-
 func (u *usesLibrary) deps(ctx android.BottomUpMutatorContext, addCompatDeps bool) {
 	if !ctx.Config().UnbundledBuild() || ctx.Config().UnbundledBuildImage() {
 		ctx.AddVariationDependencies(nil, usesLibReqTag, u.usesLibraryProperties.Uses_libs...)
-		ctx.AddVariationDependencies(nil, usesLibOptTag, u.presentOptionalUsesLibs(ctx)...)
+		presentOptionalUsesLibs := u.presentOptionalUsesLibs(ctx)
+		ctx.AddVariationDependencies(nil, usesLibOptTag, presentOptionalUsesLibs...)
 		// Only add these extra dependencies if the module is an app that depends on framework
 		// libs. This avoids creating a cyclic dependency:
 		//     e.g. framework-res -> org.apache.http.legacy -> ... -> framework-res.
@@ -1636,6 +1620,8 @@
 			ctx.AddVariationDependencies(nil, usesLibCompat28OptTag, dexpreopt.OptionalCompatUsesLibs28...)
 			ctx.AddVariationDependencies(nil, usesLibCompat30OptTag, dexpreopt.OptionalCompatUsesLibs30...)
 		}
+		_, diff, _ := android.ListSetDifference(u.usesLibraryProperties.Optional_uses_libs, presentOptionalUsesLibs)
+		u.usesLibraryProperties.Missing_optional_uses_libs = diff
 	} else {
 		ctx.AddVariationDependencies(nil, r8LibraryJarTag, u.usesLibraryProperties.Uses_libs...)
 		ctx.AddVariationDependencies(nil, r8LibraryJarTag, u.presentOptionalUsesLibs(ctx)...)
@@ -1654,15 +1640,6 @@
 	return optionalUsesLibs
 }
 
-// Helper function to replace string in a list.
-func replaceInList(list []string, oldstr, newstr string) {
-	for i, str := range list {
-		if str == oldstr {
-			list[i] = newstr
-		}
-	}
-}
-
 // Returns a map of module names of shared library dependencies to the paths to their dex jars on
 // host and on device.
 func (u *usesLibrary) classLoaderContextForUsesLibDeps(ctx android.ModuleContext) dexpreopt.ClassLoaderContextMap {
@@ -1704,11 +1681,6 @@
 			libName := dep
 			if ulib, ok := m.(ProvidesUsesLib); ok && ulib.ProvidesUsesLib() != nil {
 				libName = *ulib.ProvidesUsesLib()
-				// Replace module name with library name in `uses_libs`/`optional_uses_libs` in
-				// order to pass verify_uses_libraries check (which compares these properties
-				// against library names written in the manifest).
-				replaceInList(u.usesLibraryProperties.Uses_libs, dep, libName)
-				replaceInList(u.usesLibraryProperties.Optional_uses_libs, dep, libName)
 			}
 			clcMap.AddContext(ctx, tag.sdkVersion, libName, tag.optional,
 				lib.DexJarBuildPath(ctx).PathOrNil(), lib.DexJarInstallPath(),
@@ -1742,7 +1714,7 @@
 // an APK with the manifest embedded in it (manifest_check will know which one it is by the file
 // extension: APKs are supposed to end with '.apk').
 func (u *usesLibrary) verifyUsesLibraries(ctx android.ModuleContext, inputFile android.Path,
-	outputFile android.WritablePath) android.Path {
+	outputFile android.WritablePath, classLoaderContexts *dexpreopt.ClassLoaderContextMap) android.Path {
 
 	statusFile := dexpreopt.UsesLibrariesStatusFile(ctx)
 
@@ -1770,27 +1742,37 @@
 		cmd.Flag("--enforce-uses-libraries-relax")
 	}
 
-	for _, lib := range u.usesLibraryProperties.Uses_libs {
+	requiredUsesLibs, optionalUsesLibs := classLoaderContexts.UsesLibs()
+	for _, lib := range requiredUsesLibs {
 		cmd.FlagWithArg("--uses-library ", lib)
 	}
-
-	for _, lib := range u.usesLibraryProperties.Optional_uses_libs {
+	for _, lib := range optionalUsesLibs {
 		cmd.FlagWithArg("--optional-uses-library ", lib)
 	}
 
+	// Also add missing optional uses libs, as the manifest check expects them.
+	// Note that what we add here are the module names of those missing libs, not library names, while
+	// the manifest check actually expects library names. However, the case where a library is missing
+	// and the module name != the library name is too rare for us to handle.
+	for _, lib := range u.usesLibraryProperties.Missing_optional_uses_libs {
+		cmd.FlagWithArg("--missing-optional-uses-library ", lib)
+	}
+
 	rule.Build("verify_uses_libraries", "verify <uses-library>")
 	return outputFile
 }
 
 // verifyUsesLibrariesManifest checks the <uses-library> tags in an AndroidManifest.xml against
 // the build system and returns the path to a copy of the manifest.
-func (u *usesLibrary) verifyUsesLibrariesManifest(ctx android.ModuleContext, manifest android.Path) android.Path {
+func (u *usesLibrary) verifyUsesLibrariesManifest(ctx android.ModuleContext, manifest android.Path,
+	classLoaderContexts *dexpreopt.ClassLoaderContextMap) android.Path {
 	outputFile := android.PathForModuleOut(ctx, "manifest_check", "AndroidManifest.xml")
-	return u.verifyUsesLibraries(ctx, manifest, outputFile)
+	return u.verifyUsesLibraries(ctx, manifest, outputFile, classLoaderContexts)
 }
 
 // verifyUsesLibrariesAPK checks the <uses-library> tags in the manifest of an APK against the build
 // system and returns the path to a copy of the APK.
-func (u *usesLibrary) verifyUsesLibrariesAPK(ctx android.ModuleContext, apk android.Path) {
-	u.verifyUsesLibraries(ctx, apk, nil) // for APKs manifest_check does not write output file
+func (u *usesLibrary) verifyUsesLibrariesAPK(ctx android.ModuleContext, apk android.Path,
+	classLoaderContexts *dexpreopt.ClassLoaderContextMap) {
+	u.verifyUsesLibraries(ctx, apk, nil, classLoaderContexts) // for APKs manifest_check does not write output file
 }
diff --git a/java/app_import.go b/java/app_import.go
index 7387e16..bb07c42 100644
--- a/java/app_import.go
+++ b/java/app_import.go
@@ -355,7 +355,7 @@
 	}
 
 	if a.usesLibrary.enforceUsesLibraries() {
-		a.usesLibrary.verifyUsesLibrariesAPK(ctx, srcApk)
+		a.usesLibrary.verifyUsesLibrariesAPK(ctx, srcApk, &a.dexpreopter.classLoaderContexts)
 	}
 
 	a.dexpreopter.dexpreopt(ctx, android.RemoveOptionalPrebuiltPrefix(ctx.ModuleName()), jnisUncompressed)
@@ -611,6 +611,12 @@
 	return return_struct
 }
 
+func (a *AndroidAppImport) UsesLibrary() *usesLibrary {
+	return &a.usesLibrary
+}
+
+var _ ModuleWithUsesLibrary = (*AndroidAppImport)(nil)
+
 // android_app_import imports a prebuilt apk with additional processing specified in the module.
 // DPI-specific apk source files can be specified using dpi_variants. Example:
 //
diff --git a/java/app_test.go b/java/app_test.go
index 0c28000..eab40e7 100644
--- a/java/app_test.go
+++ b/java/app_test.go
@@ -3244,7 +3244,10 @@
 			name: "static-y",
 			srcs: ["a.java"],
 			uses_libs: ["runtime-required-y"],
-			optional_uses_libs: ["runtime-optional-y"],
+			optional_uses_libs: [
+				"runtime-optional-y",
+				"missing-lib-a",
+			],
 			sdk_version: "current",
 		}
 
@@ -3280,7 +3283,7 @@
 			sdk_version: "current",
 			optional_uses_libs: [
 				"bar",
-				"baz",
+				"missing-lib-b",
 			],
 		}
 
@@ -3295,7 +3298,7 @@
 			],
 			optional_uses_libs: [
 				"bar",
-				"baz",
+				"missing-lib-b",
 			],
 		}
 	`
@@ -3317,10 +3320,10 @@
 	// propagated from dependencies.
 	actualManifestFixerArgs := app.Output("manifest_fixer/AndroidManifest.xml").Args["args"]
 	expectManifestFixerArgs := `--extract-native-libs=true ` +
-		`--uses-library qux ` +
-		`--uses-library quuz ` +
 		`--uses-library foo ` +
 		`--uses-library com.non.sdk.lib ` +
+		`--uses-library qux ` +
+		`--uses-library quuz ` +
 		`--uses-library runtime-library ` +
 		`--uses-library runtime-required-x ` +
 		`--uses-library runtime-required-y ` +
@@ -3339,9 +3342,10 @@
 		`--uses-library runtime-required-x ` +
 		`--uses-library runtime-required-y ` +
 		`--optional-uses-library bar ` +
-		`--optional-uses-library baz ` +
 		`--optional-uses-library runtime-optional-x ` +
-		`--optional-uses-library runtime-optional-y `
+		`--optional-uses-library runtime-optional-y ` +
+		`--missing-optional-uses-library missing-lib-b ` +
+		`--missing-optional-uses-library missing-lib-a`
 	android.AssertStringDoesContain(t, "verify cmd args", verifyCmd, verifyArgs)
 
 	// Test that all libraries are verified for an APK (library order matters).
@@ -3350,7 +3354,7 @@
 		`--uses-library com.non.sdk.lib ` +
 		`--uses-library android.test.runner ` +
 		`--optional-uses-library bar ` +
-		`--optional-uses-library baz `
+		`--missing-optional-uses-library missing-lib-b `
 	android.AssertStringDoesContain(t, "verify apk cmd args", verifyApkCmd, verifyApkArgs)
 
 	// Test that necessary args are passed for constructing CLC in Ninja phase.
diff --git a/java/base.go b/java/base.go
index ef61f1c..938ac5e 100644
--- a/java/base.go
+++ b/java/base.go
@@ -843,9 +843,11 @@
 		if dep != nil {
 			if component, ok := dep.(SdkLibraryComponentDependency); ok {
 				if lib := component.OptionalSdkLibraryImplementation(); lib != nil {
-					// Add library as optional if it's one of the optional compatibility libs.
+					// Add library as optional if it's one of the optional compatibility libs or it's
+					// explicitly listed in the optional_uses_libs property.
 					tag := usesLibReqTag
-					if android.InList(*lib, dexpreopt.OptionalCompatUsesLibs) {
+					if android.InList(*lib, dexpreopt.OptionalCompatUsesLibs) ||
+						android.InList(*lib, j.usesLibrary.usesLibraryProperties.Optional_uses_libs) {
 						tag = usesLibOptTag
 					}
 					ctx.AddVariationDependencies(nil, tag, *lib)
@@ -2387,6 +2389,7 @@
 		}
 
 		addCLCFromDep(ctx, module, j.classLoaderContexts)
+		addMissingOptionalUsesLibsFromDep(ctx, module, &j.usesLibrary)
 	})
 
 	return deps
@@ -2720,3 +2723,13 @@
 }
 
 var _ ModuleWithStem = (*Module)(nil)
+
+type ModuleWithUsesLibrary interface {
+	UsesLibrary() *usesLibrary
+}
+
+func (j *Module) UsesLibrary() *usesLibrary {
+	return &j.usesLibrary
+}
+
+var _ ModuleWithUsesLibrary = (*Module)(nil)
diff --git a/java/java.go b/java/java.go
index ca99e69..fb35a9a 100644
--- a/java/java.go
+++ b/java/java.go
@@ -966,8 +966,8 @@
 }
 
 func (j *Library) DepsMutator(ctx android.BottomUpMutatorContext) {
-	j.deps(ctx)
 	j.usesLibrary.deps(ctx, false)
+	j.deps(ctx)
 }
 
 const (
@@ -3162,13 +3162,35 @@
 	// <uses_library> and should not be added to CLC, but the transitive <uses-library> dependencies
 	// from its CLC should be added to the current CLC.
 	if sdkLib != nil {
-		clcMap.AddContext(ctx, dexpreopt.AnySdkVersion, *sdkLib, false,
+		optional := false
+		if module, ok := ctx.Module().(ModuleWithUsesLibrary); ok {
+			if android.InList(*sdkLib, module.UsesLibrary().usesLibraryProperties.Optional_uses_libs) {
+				optional = true
+			}
+		}
+		clcMap.AddContext(ctx, dexpreopt.AnySdkVersion, *sdkLib, optional,
 			dep.DexJarBuildPath(ctx).PathOrNil(), dep.DexJarInstallPath(), dep.ClassLoaderContexts())
 	} else {
 		clcMap.AddContextMap(dep.ClassLoaderContexts(), depName)
 	}
 }
 
+func addMissingOptionalUsesLibsFromDep(ctx android.ModuleContext, depModule android.Module,
+	usesLibrary *usesLibrary) {
+
+	dep, ok := depModule.(ModuleWithUsesLibrary)
+	if !ok {
+		return
+	}
+
+	for _, lib := range dep.UsesLibrary().usesLibraryProperties.Missing_optional_uses_libs {
+		if !android.InList(lib, usesLibrary.usesLibraryProperties.Missing_optional_uses_libs) {
+			usesLibrary.usesLibraryProperties.Missing_optional_uses_libs =
+				append(usesLibrary.usesLibraryProperties.Missing_optional_uses_libs, lib)
+		}
+	}
+}
+
 type JavaApiContributionImport struct {
 	JavaApiContribution
 
diff --git a/partner/androidmk/androidmk_test.go b/partner/androidmk/androidmk_test.go
index 6bae836..3ace750 100644
--- a/partner/androidmk/androidmk_test.go
+++ b/partner/androidmk/androidmk_test.go
@@ -54,6 +54,9 @@
 }
 
 func TestEndToEnd(t *testing.T) {
+	// Skip checking Android.mk path with cleaning "ANDROID_BUILD_TOP"
+	t.Setenv("ANDROID_BUILD_TOP", "")
+
 	for i, test := range testCases {
 		expected, err := bpfix.Reformat(test.expected)
 		if err != nil {
diff --git a/scripts/manifest_check.py b/scripts/manifest_check.py
index c33b104..b101259 100755
--- a/scripts/manifest_check.py
+++ b/scripts/manifest_check.py
@@ -52,6 +52,14 @@
         'required:false'
     )
     parser.add_argument(
+        '--missing-optional-uses-library',
+        dest='missing_optional_uses_libraries',
+        action='append',
+        help='specify uses-library entries missing from the build system with '
+        'required:false',
+        default=[]
+    )
+    parser.add_argument(
         '--enforce-uses-libraries',
         dest='enforce_uses_libraries',
         action='store_true',
@@ -91,7 +99,7 @@
 C_BOLD = "\033[1m"
 
 
-def enforce_uses_libraries(manifest, required, optional, relax, is_apk, path):
+def enforce_uses_libraries(manifest, required, optional, missing_optional, relax, is_apk, path):
     """Verify that the <uses-library> tags in the manifest match those provided
 
   by the build system.
@@ -119,7 +127,12 @@
     required = trim_namespace_parts(required)
     optional = trim_namespace_parts(optional)
 
-    if manifest_required == required and manifest_optional == optional:
+    existing_manifest_optional = [
+        lib for lib in manifest_optional if lib not in missing_optional]
+
+    # The order of the existing libraries matter, while the order of the missing
+    # ones doesn't.
+    if manifest_required == required and existing_manifest_optional == optional:
         return None
 
     #pylint: disable=line-too-long
@@ -129,6 +142,7 @@
         '\t- required libraries in build system: %s[%s]%s\n' % (C_RED, ', '.join(required), C_OFF),
         '\t                 vs. in the manifest: %s[%s]%s\n' % (C_RED, ', '.join(manifest_required), C_OFF),
         '\t- optional libraries in build system: %s[%s]%s\n' % (C_RED, ', '.join(optional), C_OFF),
+        '\t    and missing ones in build system: %s[%s]%s\n' % (C_RED, ', '.join(missing_optional), C_OFF),
         '\t                 vs. in the manifest: %s[%s]%s\n' % (C_RED, ', '.join(manifest_optional), C_OFF),
         '\t- tags in the manifest (%s):\n' % path,
         '\t\t%s\n' % '\t\t'.join(tags),
@@ -340,11 +354,14 @@
 
         if args.enforce_uses_libraries:
             # Load dexpreopt.config files and build a mapping from module
-            # names to library names. This is necessary because build system
-            # addresses libraries by their module name (`uses_libs`,
-            # `optional_uses_libs`, `LOCAL_USES_LIBRARIES`,
-            # `LOCAL_OPTIONAL_LIBRARY_NAMES` all contain module names), while
-            # the manifest addresses libraries by their name.
+            # names to library names. This is for Make only and it's necessary
+            # because Make passes module names from `LOCAL_USES_LIBRARIES`,
+            # `LOCAL_OPTIONAL_LIBRARY_NAMES`, while the manifest addresses
+            # libraries by their name. Soong doesn't use it and doesn't need it
+            # because it converts the module names to the library names and
+            # passes the library names. There is no need to translate missing
+            # optional libs because they are missing and therefore there is no
+            # mapping for them.
             mod_to_lib = load_dexpreopt_configs(args.dexpreopt_configs)
             required = translate_libnames(args.uses_libraries, mod_to_lib)
             optional = translate_libnames(args.optional_uses_libraries,
@@ -354,8 +371,8 @@
             # those in the manifest. Raise an exception on mismatch, unless the
             # script was passed a special parameter to suppress exceptions.
             errmsg = enforce_uses_libraries(manifest, required, optional,
-                                            args.enforce_uses_libraries_relax,
-                                            is_apk, args.input)
+                args.missing_optional_uses_libraries,
+                args.enforce_uses_libraries_relax, is_apk, args.input)
 
             # Create a status file that is empty on success, or contains an
             # error message on failure. When exceptions are suppressed,
diff --git a/scripts/manifest_check_test.py b/scripts/manifest_check_test.py
index 3be7a30..8003b3e 100755
--- a/scripts/manifest_check_test.py
+++ b/scripts/manifest_check_test.py
@@ -44,15 +44,17 @@
 class EnforceUsesLibrariesTest(unittest.TestCase):
     """Unit tests for add_extract_native_libs function."""
 
-    def run_test(self, xml, apk, uses_libraries=[], optional_uses_libraries=[]): #pylint: disable=dangerous-default-value
+    def run_test(self, xml, apk, uses_libraries=[], optional_uses_libraries=[],
+                 missing_optional_uses_libraries=[]): #pylint: disable=dangerous-default-value
         doc = minidom.parseString(xml)
         try:
             relax = False
             manifest_check.enforce_uses_libraries(
-                doc, uses_libraries, optional_uses_libraries, relax, False,
-                'path/to/X/AndroidManifest.xml')
+                doc, uses_libraries, optional_uses_libraries, missing_optional_uses_libraries,
+                relax, False, 'path/to/X/AndroidManifest.xml')
             manifest_check.enforce_uses_libraries(apk, uses_libraries,
                                                   optional_uses_libraries,
+                                                  missing_optional_uses_libraries,
                                                   relax, True,
                                                   'path/to/X/X.apk')
             return True
@@ -102,6 +104,15 @@
         matches = self.run_test(xml, apk, optional_uses_libraries=['foo'])
         self.assertFalse(matches)
 
+    def test_expected_missing_optional_uses_library(self):
+        xml = self.xml_tmpl % (
+            uses_library_xml('foo') + uses_library_xml('missing') + uses_library_xml('bar'))
+        apk = self.apk_tmpl % (
+            uses_library_apk('foo') + uses_library_apk('missing') + uses_library_apk('bar'))
+        matches = self.run_test(xml, apk, optional_uses_libraries=['foo', 'bar'],
+                                missing_optional_uses_libraries=['missing'])
+        self.assertFalse(matches)
+
     def test_missing_uses_library(self):
         xml = self.xml_tmpl % ('')
         apk = self.apk_tmpl % ('')