diff --git a/ui/build/config.go b/ui/build/config.go
index f02222e..79f57ac 100644
--- a/ui/build/config.go
+++ b/ui/build/config.go
@@ -54,6 +54,16 @@
 	rbeRandPrefix = rand.Intn(1000)
 }
 
+// Which builder are we using?
+type ninjaCommandType = int
+
+const (
+	_ = iota
+	NINJA_NINJA
+	NINJA_N2
+	NINJA_SISO
+)
+
 type Config struct{ *configImpl }
 
 type configImpl struct {
@@ -123,9 +133,8 @@
 	// could consider merging them.
 	moduleDebugFile string
 
-	// Whether to use n2 instead of ninja.  This is controlled with the
-	// environment variable SOONG_USE_N2
-	useN2 bool
+	// Which builder are we using
+	ninjaCommand ninjaCommandType
 }
 
 type NinjaWeightListSource uint
@@ -288,8 +297,16 @@
 		ret.moduleDebugFile, _ = filepath.Abs(shared.JoinPath(ret.SoongOutDir(), "soong-debug-info.json"))
 	}
 
-	if os.Getenv("SOONG_USE_N2") == "true" {
-		ret.useN2 = true
+	ret.ninjaCommand = NINJA_NINJA
+	switch os.Getenv("SOONG_NINJA") {
+	case "n2":
+		ret.ninjaCommand = NINJA_N2
+	case "siso":
+		ret.ninjaCommand = NINJA_SISO
+	default:
+		if os.Getenv("SOONG_USE_N2") == "true" {
+			ret.ninjaCommand = NINJA_N2
+		}
 	}
 
 	ret.environ.Unset(
@@ -349,7 +366,8 @@
 		// We read it here already, don't let others share in the fun
 		"GENERATE_SOONG_DEBUG",
 
-		// Use config.useN2 instead.
+		// Use config.ninjaCommand instead.
+		"SOONG_NINJA",
 		"SOONG_USE_N2",
 	)
 
@@ -1641,6 +1659,12 @@
 	return strings.ReplaceAll(path, "/linux-x86/", "/linux_musl-x86/")
 }
 
+func (c *configImpl) SisoBin() string {
+	path := c.PrebuiltBuildTool("siso")
+	// Use musl instead of glibc because glibc on the build server is old and has bugs
+	return strings.ReplaceAll(path, "/linux-x86/", "/linux_musl-x86/")
+}
+
 func (c *configImpl) PrebuiltBuildTool(name string) string {
 	if v, ok := c.environ.Get("SANITIZE_HOST"); ok {
 		if sanitize := strings.Fields(v); inList("address", sanitize) {
diff --git a/ui/build/ninja.go b/ui/build/ninja.go
index 4e3e544..def0783 100644
--- a/ui/build/ninja.go
+++ b/ui/build/ninja.go
@@ -49,14 +49,10 @@
 	nr := status.NewNinjaReader(ctx, ctx.Status.StartTool(), fifo)
 	defer nr.Close()
 
-	executable := config.NinjaBin()
-	args := []string{
-		"-d", "keepdepfile",
-		"-d", "keeprsp",
-		"-d", "stats",
-		"--frontend_file", fifo,
-	}
-	if config.useN2 {
+	var executable string
+	var args []string
+	switch config.ninjaCommand {
+	case NINJA_N2:
 		executable = config.N2Bin()
 		args = []string{
 			"-d", "trace",
@@ -66,8 +62,31 @@
 			//"-d", "stats",
 			"--frontend-file", fifo,
 		}
+	case NINJA_SISO:
+		executable = config.SisoBin()
+		args = []string{
+			"ninja",
+			"--log_dir", config.SoongOutDir(),
+			// TODO: implement these features, or remove them.
+			//"-d", "trace",
+			//"-d", "keepdepfile",
+			//"-d", "keeprsp",
+			//"-d", "stats",
+			//"--frontend-file", fifo,
+		}
+	default:
+		// NINJA_NINJA is the default.
+		executable = config.NinjaBin()
+		args = []string{
+			"-d", "keepdepfile",
+			"-d", "keeprsp",
+			"-d", "stats",
+			"--frontend_file", fifo,
+			"-o", "usesphonyoutputs=yes",
+			"-w", "dupbuild=err",
+			"-w", "missingdepfile=err",
+		}
 	}
-
 	args = append(args, config.NinjaArgs()...)
 
 	var parallel int
@@ -83,17 +102,10 @@
 
 	args = append(args, "-f", config.CombinedNinjaFile())
 
-	if !config.useN2 {
-		args = append(args,
-			"-o", "usesphonyoutputs=yes",
-			"-w", "dupbuild=err",
-			"-w", "missingdepfile=err")
-	}
-
 	if !config.BuildBrokenMissingOutputs() {
 		// Missing outputs will be treated as errors.
 		// BUILD_BROKEN_MISSING_OUTPUTS can be used to bypass this check.
-		if !config.useN2 {
+		if config.ninjaCommand != NINJA_N2 {
 			args = append(args,
 				"-w", "missingoutfile=err",
 			)
@@ -110,21 +122,18 @@
 		cmd.Environment.AppendFromKati(config.KatiEnvFile())
 	}
 
-	switch config.NinjaWeightListSource() {
-	case NINJA_LOG:
-		if !config.useN2 {
+	// TODO(b/346806126): implement this for the other ninjaCommand values.
+	if config.ninjaCommand == NINJA_NINJA {
+		switch config.NinjaWeightListSource() {
+		case NINJA_LOG:
 			cmd.Args = append(cmd.Args, "-o", "usesninjalogasweightlist=yes")
-		}
-	case EVENLY_DISTRIBUTED:
-		// pass empty weight list means ninja considers every tasks's weight as 1(default value).
-		if !config.useN2 {
+		case EVENLY_DISTRIBUTED:
+			// pass empty weight list means ninja considers every tasks's weight as 1(default value).
 			cmd.Args = append(cmd.Args, "-o", "usesweightlist=/dev/null")
-		}
-	case EXTERNAL_FILE:
-		fallthrough
-	case HINT_FROM_SOONG:
-		// The weight list is already copied/generated.
-		if !config.useN2 {
+		case EXTERNAL_FILE:
+			fallthrough
+		case HINT_FROM_SOONG:
+			// The weight list is already copied/generated.
 			ninjaWeightListPath := filepath.Join(config.OutDir(), ninjaWeightListFileName)
 			cmd.Args = append(cmd.Args, "-o", "usesweightlist="+ninjaWeightListPath)
 		}
@@ -227,6 +236,8 @@
 			// We don't want this build broken flag to cause reanalysis, so allow it through to the
 			// actions.
 			"BUILD_BROKEN_INCORRECT_PARTITION_IMAGES",
+			// Do not do reanalysis just because we changed ninja commands.
+			"SOONG_NINJA",
 			"SOONG_USE_N2",
 			"RUST_BACKTRACE",
 			"RUST_LOG",
@@ -235,8 +246,11 @@
 
 	cmd.Environment.Set("DIST_DIR", config.DistDir())
 	cmd.Environment.Set("SHELL", "/bin/bash")
-	if config.useN2 {
+	switch config.ninjaCommand {
+	case NINJA_N2:
 		cmd.Environment.Set("RUST_BACKTRACE", "1")
+	default:
+		// Only set RUST_BACKTRACE for n2.
 	}
 
 	// Print the environment variables that Ninja is operating in.
diff --git a/ui/build/soong.go b/ui/build/soong.go
index 97bc997..eb51022 100644
--- a/ui/build/soong.go
+++ b/ui/build/soong.go
@@ -588,19 +588,11 @@
 		nr := status.NewNinjaReader(ctx, ctx.Status.StartTool(), fifo)
 		defer nr.Close()
 
-		ninjaArgs := []string{
-			"-d", "keepdepfile",
-			"-d", "stats",
-			"-o", "usesphonyoutputs=yes",
-			"-o", "preremoveoutputs=yes",
-			"-w", "dupbuild=err",
-			"-w", "outputdir=err",
-			"-w", "missingoutfile=err",
-			"-j", strconv.Itoa(config.Parallel()),
-			"--frontend_file", fifo,
-			"-f", filepath.Join(config.SoongOutDir(), "bootstrap.ninja"),
-		}
-		if config.useN2 {
+		var ninjaCmd string
+		var ninjaArgs []string
+		switch config.ninjaCommand {
+		case NINJA_N2:
+			ninjaCmd = config.N2Bin()
 			ninjaArgs = []string{
 				// TODO: implement these features, or remove them.
 				//"-d", "keepdepfile",
@@ -615,6 +607,39 @@
 				"--frontend-file", fifo,
 				"-f", filepath.Join(config.SoongOutDir(), "bootstrap.ninja"),
 			}
+		case NINJA_SISO:
+			ninjaCmd = config.SisoBin()
+			ninjaArgs = []string{
+				"ninja",
+				// TODO: implement these features, or remove them.
+				//"-d", "keepdepfile",
+				//"-d", "stats",
+				//"-o", "usesphonyoutputs=yes",
+				//"-o", "preremoveoutputs=yes",
+				//"-w", "dupbuild=err",
+				//"-w", "outputdir=err",
+				//"-w", "missingoutfile=err",
+				"-v",
+				"-j", strconv.Itoa(config.Parallel()),
+				//"--frontend-file", fifo,
+				"--log_dir", config.SoongOutDir(),
+				"-f", filepath.Join(config.SoongOutDir(), "bootstrap.ninja"),
+			}
+		default:
+			// NINJA_NINJA is the default.
+			ninjaCmd = config.NinjaBin()
+			ninjaArgs = []string{
+				"-d", "keepdepfile",
+				"-d", "stats",
+				"-o", "usesphonyoutputs=yes",
+				"-o", "preremoveoutputs=yes",
+				"-w", "dupbuild=err",
+				"-w", "outputdir=err",
+				"-w", "missingoutfile=err",
+				"-j", strconv.Itoa(config.Parallel()),
+				"--frontend_file", fifo,
+				"-f", filepath.Join(config.SoongOutDir(), "bootstrap.ninja"),
+			}
 		}
 
 		if extra, ok := config.Environment().Get("SOONG_UI_NINJA_ARGS"); ok {
@@ -623,10 +648,6 @@
 		}
 
 		ninjaArgs = append(ninjaArgs, targets...)
-		ninjaCmd := config.NinjaBin()
-		if config.useN2 {
-			ninjaCmd = config.N2Bin()
-		}
 
 		cmd := Command(ctx, config, "soong bootstrap",
 			ninjaCmd, ninjaArgs...)