diff --git a/android/image.go b/android/image.go
index 0f03107..6e5a551 100644
--- a/android/image.go
+++ b/android/image.go
@@ -14,7 +14,7 @@
 
 package android
 
-// ImageInterface is implemented by modules that need to be split by the imageMutator.
+// ImageInterface is implemented by modules that need to be split by the imageTransitionMutator.
 type ImageInterface interface {
 	// ImageMutatorBegin is called before any other method in the ImageInterface.
 	ImageMutatorBegin(ctx BaseModuleContext)
@@ -81,18 +81,16 @@
 	DebugRamdiskVariation string = "debug_ramdisk"
 )
 
-// imageMutator creates variants for modules that implement the ImageInterface that
+// imageTransitionMutator creates variants for modules that implement the ImageInterface that
 // allow them to build differently for each partition (recovery, core, vendor, etc.).
-func imageMutator(ctx BottomUpMutatorContext) {
-	if ctx.Os() != Android {
-		return
-	}
+type imageTransitionMutator struct{}
 
-	if m, ok := ctx.Module().(ImageInterface); ok {
+func (imageTransitionMutator) Split(ctx BaseModuleContext) []string {
+	var variations []string
+
+	if m, ok := ctx.Module().(ImageInterface); ctx.Os() == Android && ok {
 		m.ImageMutatorBegin(ctx)
 
-		var variations []string
-
 		if m.CoreVariantNeeded(ctx) {
 			variations = append(variations, CoreVariation)
 		}
@@ -117,15 +115,29 @@
 
 		extraVariations := m.ExtraImageVariations(ctx)
 		variations = append(variations, extraVariations...)
+	}
 
-		if len(variations) == 0 {
-			return
-		}
+	if len(variations) == 0 {
+		variations = append(variations, "")
+	}
 
-		mod := ctx.CreateVariations(variations...)
-		for i, v := range variations {
-			mod[i].base().setImageVariation(v)
-			mod[i].(ImageInterface).SetImageVariation(ctx, v)
-		}
+	return variations
+}
+
+func (imageTransitionMutator) OutgoingTransition(ctx OutgoingTransitionContext, sourceVariation string) string {
+	return sourceVariation
+}
+
+func (imageTransitionMutator) IncomingTransition(ctx IncomingTransitionContext, incomingVariation string) string {
+	if _, ok := ctx.Module().(ImageInterface); ctx.Os() != Android || !ok {
+		return CoreVariation
+	}
+	return incomingVariation
+}
+
+func (imageTransitionMutator) Mutate(ctx BottomUpMutatorContext, variation string) {
+	ctx.Module().base().setImageVariation(variation)
+	if m, ok := ctx.Module().(ImageInterface); ok {
+		m.SetImageVariation(ctx, variation)
 	}
 }
diff --git a/android/module.go b/android/module.go
index 5c2b1e1..f9fab96 100644
--- a/android/module.go
+++ b/android/module.go
@@ -1914,7 +1914,7 @@
 				return
 			}
 			cacheKey = &blueprint.BuildActionCacheKey{
-				Id:        ctx.bp.ModuleId(),
+				Id:        ctx.bp.ModuleCacheKey(),
 				InputHash: hash,
 			}
 		}
diff --git a/android/mutator.go b/android/mutator.go
index b81dd12..38fb857 100644
--- a/android/mutator.go
+++ b/android/mutator.go
@@ -149,7 +149,7 @@
 
 func registerArchMutator(ctx RegisterMutatorsContext) {
 	ctx.BottomUpBlueprint("os", osMutator).Parallel()
-	ctx.BottomUp("image", imageMutator).Parallel()
+	ctx.Transition("image", &imageTransitionMutator{})
 	ctx.BottomUpBlueprint("arch", archMutator).Parallel()
 }
 
diff --git a/bin/soongdbg b/bin/soongdbg
index a73bdf9..98d31eb 100755
--- a/bin/soongdbg
+++ b/bin/soongdbg
@@ -216,7 +216,7 @@
                         help="jq query for each module metadata")
     parser.add_argument("--deptags", action="store_true",
                         help="show dependency tags (makes the graph much more complex)")
-    parser.add_argument("--tag", action="append",
+    parser.add_argument("--tag", action="append", default=[],
                         help="Limit output to these dependency tags.")
 
     group = parser.add_argument_group("output formats",
diff --git a/bpf/bpf.go b/bpf/bpf.go
index 09262e5..6445394 100644
--- a/bpf/bpf.go
+++ b/bpf/bpf.go
@@ -148,6 +148,10 @@
 		"-no-canonical-prefixes",
 
 		"-O2",
+		"-Wall",
+		"-Werror",
+		"-Wextra",
+
 		"-isystem bionic/libc/include",
 		"-isystem bionic/libc/kernel/uapi",
 		// The architecture doesn't matter here, but asm/types.h is included by linux/types.h.
@@ -165,7 +169,7 @@
 
 	cflags = append(cflags, bpf.properties.Cflags...)
 
-	if proptools.Bool(bpf.properties.Btf) {
+	if proptools.BoolDefault(bpf.properties.Btf, true) {
 		cflags = append(cflags, "-g")
 		if runtime.GOOS != "darwin" {
 			cflags = append(cflags, "-fdebug-prefix-map=/proc/self/cwd=")
@@ -190,7 +194,7 @@
 			},
 		})
 
-		if proptools.Bool(bpf.properties.Btf) {
+		if proptools.BoolDefault(bpf.properties.Btf, true) {
 			objStripped := android.ObjPathWithExt(ctx, "", src, "o")
 			ctx.Build(pctx, android.BuildParams{
 				Rule:   stripRule,
diff --git a/cc/config/global.go b/cc/config/global.go
index bf2502f..66196c2 100644
--- a/cc/config/global.go
+++ b/cc/config/global.go
@@ -136,11 +136,6 @@
 		// displaying logs in web browsers.
 		"-fmessage-length=0",
 
-		// Disable C++17 "relaxed template template argument matching" as a workaround for
-		// our out-dated libcxx.
-		// http://b/341084395
-		"-fno-relaxed-template-template-args",
-
 		// Using simple template names reduces the size of debug builds.
 		"-gsimple-template-names",
 
diff --git a/java/ravenwood.go b/java/ravenwood.go
index 84c285c..a52f405 100644
--- a/java/ravenwood.go
+++ b/java/ravenwood.go
@@ -285,6 +285,14 @@
 	installPath := android.PathForModuleInstall(ctx, r.BaseModuleName())
 	for _, lib := range r.ravenwoodLibgroupProperties.Libs {
 		libModule := ctx.GetDirectDepWithTag(lib, ravenwoodLibContentTag)
+		if libModule == nil {
+			if ctx.Config().AllowMissingDependencies() {
+				ctx.AddMissingDependencies([]string{lib})
+			} else {
+				ctx.PropertyErrorf("lib", "missing dependency %q", lib)
+			}
+			continue
+		}
 		libJar := android.OutputFileForModule(ctx, libModule, "")
 		ctx.InstallFile(installPath, lib+".jar", libJar)
 	}
diff --git a/scripts/gen_build_prop.py b/scripts/gen_build_prop.py
index 56ce14f..c0d4735 100644
--- a/scripts/gen_build_prop.py
+++ b/scripts/gen_build_prop.py
@@ -237,7 +237,7 @@
 
   print(f"# Do not try to parse description or thumbprint")
   print(f"ro.build.description?={config['BuildDesc']}")
-  if "build_thumbprint" in config:
+  if "BuildThumbprint" in config:
     print(f"ro.build.thumbprint={config['BuildThumbprint']}")
 
   print(f"# end build properties")
diff --git a/ui/build/config.go b/ui/build/config.go
index 631b76f..b8fcb6b 100644
--- a/ui/build/config.go
+++ b/ui/build/config.go
@@ -1341,8 +1341,7 @@
 }
 
 func (c *configImpl) rbeTmpDir() string {
-	buildTmpDir := shared.TempDirForOutDir(c.SoongOutDir())
-	return filepath.Join(buildTmpDir, "rbe")
+	return filepath.Join(c.SoongOutDir(), "rbe")
 }
 
 func (c *configImpl) rbeCacheDir() string {
diff --git a/ui/build/rbe.go b/ui/build/rbe.go
index 8fa147f..0a0f956 100644
--- a/ui/build/rbe.go
+++ b/ui/build/rbe.go
@@ -65,7 +65,7 @@
 		"RBE_platform":         "container-image=" + remoteexec.DefaultImage,
 	}
 	if config.StartRBE() {
-		name, err := config.rbeSockAddr(absPath(ctx, config.TempDir()))
+		name, err := config.rbeSockAddr(absPath(ctx, config.rbeTmpDir()))
 		if err != nil {
 			ctx.Fatalf("Error retrieving socket address: %v", err)
 			return nil
diff --git a/ui/build/sandbox_linux.go b/ui/build/sandbox_linux.go
index 5c3fec1..c38174c 100644
--- a/ui/build/sandbox_linux.go
+++ b/ui/build/sandbox_linux.go
@@ -48,7 +48,11 @@
 	}
 )
 
-const nsjailPath = "prebuilts/build-tools/linux-x86/bin/nsjail"
+const (
+	nsjailPath = "prebuilts/build-tools/linux-x86/bin/nsjail"
+	abfsSrcDir = "/src"
+	abfsOutDir = "/src/out"
+)
 
 var sandboxConfig struct {
 	once sync.Once
@@ -145,6 +149,22 @@
 	return sandboxConfig.working
 }
 
+func (c *Cmd) srcDirArg() string {
+	if !c.config.UseABFS() {
+		return sandboxConfig.srcDir
+	}
+
+	return sandboxConfig.srcDir + ":" + abfsSrcDir
+}
+
+func (c *Cmd) outDirArg() string {
+	if !c.config.UseABFS() {
+		return sandboxConfig.outDir
+	}
+
+	return sandboxConfig.outDir + ":" + abfsOutDir
+}
+
 func (c *Cmd) wrapSandbox() {
 	wd, _ := os.Getwd()
 
@@ -188,10 +208,10 @@
 		"-B", "/tmp",
 
 		// Mount source
-		c.config.sandboxConfig.SrcDirMountFlag(), sandboxConfig.srcDir,
+		c.config.sandboxConfig.SrcDirMountFlag(), c.srcDirArg(),
 
 		//Mount out dir as read-write
-		"-B", sandboxConfig.outDir,
+		"-B", c.outDirArg(),
 
 		// Disable newcgroup for now, since it may require newer kernels
 		// TODO: try out cgroups