diff --git a/ui/build/config.go b/ui/build/config.go
new file mode 100644
index 0000000..b0a7d7a
--- /dev/null
+++ b/ui/build/config.go
@@ -0,0 +1,274 @@
+// Copyright 2017 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 build
+
+import (
+	"path/filepath"
+	"runtime"
+	"strconv"
+	"strings"
+)
+
+type Config struct{ *configImpl }
+
+type configImpl struct {
+	// From the environment
+	arguments []string
+	goma      bool
+	environ   *Environment
+
+	// From the arguments
+	parallel  int
+	keepGoing int
+	verbose   bool
+
+	// From the product config
+	katiArgs   []string
+	ninjaArgs  []string
+	katiSuffix string
+}
+
+func NewConfig(ctx Context, args ...string) Config {
+	ret := &configImpl{
+		environ: OsEnvironment(),
+	}
+
+	ret.environ.Unset(
+		// We're already using it
+		"USE_SOONG_UI",
+
+		// We should never use GOROOT/GOPATH from the shell environment
+		"GOROOT",
+		"GOPATH",
+
+		// These should only come from Soong, not the environment.
+		"CLANG",
+		"CLANG_CXX",
+		"CCC_CC",
+		"CCC_CXX",
+
+		// Used by the goma compiler wrapper, but should only be set by
+		// gomacc
+		"GOMACC_PATH",
+	)
+
+	// Tell python not to spam the source tree with .pyc files.
+	ret.environ.Set("PYTHONDONTWRITEBYTECODE", "1")
+
+	// Sane default matching ninja
+	ret.parallel = runtime.NumCPU() + 2
+	ret.keepGoing = 1
+
+	for _, arg := range args {
+		arg = strings.TrimSpace(arg)
+		if arg == "--make-mode" {
+			continue
+		} else if arg == "showcommands" {
+			ret.verbose = true
+			continue
+		}
+		if arg[0] == '-' {
+			var err error
+			if arg[1] == 'j' {
+				// TODO: handle space between j and number
+				// Unnecessary if used with makeparallel
+				ret.parallel, err = strconv.Atoi(arg[2:])
+			} else if arg[1] == 'k' {
+				// TODO: handle space between k and number
+				// Unnecessary if used with makeparallel
+				ret.keepGoing, err = strconv.Atoi(arg[2:])
+			} else {
+				ctx.Fatalln("Unknown option:", arg)
+			}
+			if err != nil {
+				ctx.Fatalln("Argument error:", err, arg)
+			}
+		} else {
+			ret.arguments = append(ret.arguments, arg)
+		}
+	}
+
+	return Config{ret}
+}
+
+// Lunch configures the environment for a specific product similarly to the
+// `lunch` bash function.
+func (c *configImpl) Lunch(ctx Context, product, variant string) {
+	if variant != "eng" && variant != "userdebug" && variant != "user" {
+		ctx.Fatalf("Invalid variant %q. Must be one of 'user', 'userdebug' or 'eng'", variant)
+	}
+
+	c.environ.Set("TARGET_PRODUCT", product)
+	c.environ.Set("TARGET_BUILD_VARIANT", variant)
+	c.environ.Set("TARGET_BUILD_TYPE", "release")
+	c.environ.Unset("TARGET_BUILD_APPS")
+}
+
+// Tapas configures the environment to build one or more unbundled apps,
+// similarly to the `tapas` bash function.
+func (c *configImpl) Tapas(ctx Context, apps []string, arch, variant string) {
+	if len(apps) == 0 {
+		apps = []string{"all"}
+	}
+	if variant == "" {
+		variant = "eng"
+	}
+
+	if variant != "eng" && variant != "userdebug" && variant != "user" {
+		ctx.Fatalf("Invalid variant %q. Must be one of 'user', 'userdebug' or 'eng'", variant)
+	}
+
+	var product string
+	switch arch {
+	case "armv5":
+		product = "generic_armv5"
+	case "arm", "":
+		product = "aosp_arm"
+	case "arm64":
+		product = "aosm_arm64"
+	case "mips":
+		product = "aosp_mips"
+	case "mips64":
+		product = "aosp_mips64"
+	case "x86":
+		product = "aosp_x86"
+	case "x86_64":
+		product = "aosp_x86_64"
+	default:
+		ctx.Fatalf("Invalid architecture: %q", arch)
+	}
+
+	c.environ.Set("TARGET_PRODUCT", product)
+	c.environ.Set("TARGET_BUILD_VARIANT", variant)
+	c.environ.Set("TARGET_BUILD_TYPE", "release")
+	c.environ.Set("TARGET_BUILD_APPS", strings.Join(apps, " "))
+}
+
+func (c *configImpl) Environment() *Environment {
+	return c.environ
+}
+
+func (c *configImpl) Arguments() []string {
+	return c.arguments
+}
+
+func (c *configImpl) OutDir() string {
+	if outDir, ok := c.environ.Get("OUT_DIR"); ok {
+		return outDir
+	}
+	return "out"
+}
+
+func (c *configImpl) NinjaArgs() []string {
+	return c.ninjaArgs
+}
+
+func (c *configImpl) SoongOutDir() string {
+	return filepath.Join(c.OutDir(), "soong")
+}
+
+func (c *configImpl) KatiSuffix() string {
+	if c.katiSuffix != "" {
+		return c.katiSuffix
+	}
+	panic("SetKatiSuffix has not been called")
+}
+
+func (c *configImpl) IsVerbose() bool {
+	return c.verbose
+}
+
+func (c *configImpl) TargetProduct() string {
+	if v, ok := c.environ.Get("TARGET_PRODUCT"); ok {
+		return v
+	}
+	panic("TARGET_PRODUCT is not defined")
+}
+
+func (c *configImpl) KatiArgs() []string {
+	return c.katiArgs
+}
+
+func (c *configImpl) Parallel() int {
+	return c.parallel
+}
+
+func (c *configImpl) UseGoma() bool {
+	if v, ok := c.environ.Get("USE_GOMA"); ok {
+		v = strings.TrimSpace(v)
+		if v != "" && v != "false" {
+			return true
+		}
+	}
+	return false
+}
+
+// RemoteParallel controls how many remote jobs (i.e., commands which contain
+// gomacc) are run in parallel.  Note the paralleism of all other jobs is
+// still limited by Parallel()
+func (c *configImpl) RemoteParallel() int {
+	if v, ok := c.environ.Get("NINJA_REMOTE_NUM_JOBS"); ok {
+		if i, err := strconv.Atoi(v); err == nil {
+			return i
+		}
+	}
+	return 500
+}
+
+func (c *configImpl) SetKatiArgs(args []string) {
+	c.katiArgs = args
+}
+
+func (c *configImpl) SetNinjaArgs(args []string) {
+	c.ninjaArgs = args
+}
+
+func (c *configImpl) SetKatiSuffix(suffix string) {
+	c.katiSuffix = suffix
+}
+
+func (c *configImpl) KatiEnvFile() string {
+	return filepath.Join(c.OutDir(), "env"+c.KatiSuffix()+".sh")
+}
+
+func (c *configImpl) KatiNinjaFile() string {
+	return filepath.Join(c.OutDir(), "build"+c.KatiSuffix()+".ninja")
+}
+
+func (c *configImpl) SoongNinjaFile() string {
+	return filepath.Join(c.SoongOutDir(), "build.ninja")
+}
+
+func (c *configImpl) CombinedNinjaFile() string {
+	return filepath.Join(c.OutDir(), "combined"+c.KatiSuffix()+".ninja")
+}
+
+func (c *configImpl) SoongAndroidMk() string {
+	return filepath.Join(c.SoongOutDir(), "Android-"+c.TargetProduct()+".mk")
+}
+
+func (c *configImpl) SoongMakeVarsMk() string {
+	return filepath.Join(c.SoongOutDir(), "make_vars-"+c.TargetProduct()+".mk")
+}
+
+func (c *configImpl) HostPrebuiltTag() string {
+	if runtime.GOOS == "linux" {
+		return "linux-x86"
+	} else if runtime.GOOS == "darwin" {
+		return "darwin-x86"
+	} else {
+		panic("Unsupported OS")
+	}
+}