diff --git a/.gn b/.gn
index 5ebbd9a0939de56e469be4d6f5dd8a708ad5fdc9..d996d6a9b4e71c679ece1b6531208d18a3cea814 100644
--- a/.gn
+++ b/.gn
@@ -14,9 +14,6 @@ buildconfig = "//build/config/BUILDCONFIG.gn"
 # in the source tree, e.g. for third party source trees.
 secondary_source = "//build/secondary/"
 
-# The source root location.
-root = "//build/gn"
-
 # The executable used to execute scripts in action and exec_script.
 script_executable = "/usr/bin/env"
 
diff --git a/BUILD.gn b/BUILD.gn
new file mode 100644
index 0000000000000000000000000000000000000000..52f40bbc7c585598fad4f7fd22c14ce2a10c4043
--- /dev/null
+++ b/BUILD.gn
@@ -0,0 +1,110 @@
+# Copyright 2019 The Fuchsia Authors. All rights reserved.
+# Use of this source code is governed by a BSD-style license that can be
+# found in the LICENSE file.
+
+import("//build/config/fuchsia/zircon.gni")
+import("//build/testing/platforms.gni")
+
+# Collect the source files that are dependencies of the create_gn_rules.py
+# script, below.  Unfortunately, exec_script cannot use a depfile produced
+# by the script and only supports a separately computed list of dependencies.
+zircon_files =
+    exec_script("//build/zircon/list_source_files.py", [], "list lines")
+
+supporting_templates = [
+  "//build/zircon/boards.mako",
+  "//build/zircon/header.mako",
+  "//build/zircon/host_tool.mako",
+  "//build/zircon/main.mako",
+  "//build/zircon/shared_library.mako",
+  "//build/zircon/source_library.mako",
+  "//build/zircon/static_library.mako",
+  "//build/zircon/sysroot.mako",
+]
+
+# The following script generates GN build files for Zircon objects.  It is
+# placed before everything else so that //zircon targets are available in
+# due time.  See //build/zircon/README.md for more details.
+exec_script("//build/zircon/create_gn_rules.py",
+            [
+              "--out",
+              rebase_path("//zircon/public"),
+              "--zircon-build",
+              rebase_path(zircon_root_build_dir),
+              "--zircon-manifest",
+              rebase_path("$zircon_root_build_dir/export/manifest-$target_cpu"),
+            ],
+            "",
+            zircon_files + supporting_templates)
+
+# Write a file that can be sourced by `fx`.  This file is produced
+# by `gn gen` and is not known to Ninja at all, so it has nothing to
+# do with the build itself.  Its sole purpose is to leave bread
+# crumbs about the settings `gn gen` used for `fx` to use later.
+_relative_build_dir = rebase_path(root_build_dir, "//", "//")
+_fx_config_lines = [
+  "# Generated by `gn gen`.",
+  "FUCHSIA_BUILD_DIR='${_relative_build_dir}'",
+  "FUCHSIA_ARCH='${target_cpu}'",
+]
+write_file("$root_build_dir/fx.config", _fx_config_lines)
+
+# Forwarding targets to things defined in //build/gn that are referred to by
+# infrastructure.
+# TODO(jamesr): Move definition from //build/gn to here after updating infra.
+
+# Permit dependencies on testonly targets from packages.
+testonly = true
+
+group("default") {
+  public_deps = [
+    "//build/gn:default",
+  ]
+}
+
+group("host_tests") {
+  visibility = []
+  public_deps = [
+    "//build/gn:host_tests",
+  ]
+}
+
+group("tests") {
+  public_deps = [
+    "//build/gn:tests",
+  ]
+}
+
+group("pseudo_tests") {
+  public_deps = [
+    "//build/gn:pseudo_tests",
+  ]
+}
+
+group("copy_host_tests") {
+  public_deps = [
+    "//build/gn:copy_host_tests",
+  ]
+}
+
+group("breakpad_symbols") {
+  public_deps = [
+    "//build/gn:breakpad_symbols",
+  ]
+}
+
+group("package_archive") {
+  public_deps = [
+    "//build/gn:package_archive",
+  ]
+}
+
+# Generates a JSON manifest of the platforms available for testing, along with
+# their properties.
+target_platforms = []
+foreach(platform, test_platforms) {
+  if (!defined(platform.cpu) || platform.cpu == current_cpu) {
+    target_platforms += [ platform ]
+  }
+}
+write_file("$root_build_dir/platforms.json", target_platforms, "json")
diff --git a/build/gn/BUILD.gn b/build/gn/BUILD.gn
index b537d8a5ed145c06b581552c69b0ecbce6ac7714..0d0995ccba4f7f47a68353b9270f0f6f1b09d4ac 100644
--- a/build/gn/BUILD.gn
+++ b/build/gn/BUILD.gn
@@ -6,56 +6,11 @@ import("//build/compiled_action.gni")
 import("//build/config/fuchsia/zircon.gni")
 import("//build/gn/packages.gni")
 import("//build/package.gni")
-import("//build/testing/platforms.gni")
 import("//build/toolchain/goma.gni")
 
 # Permit dependencies on testonly targets from packages.
 testonly = true
 
-# Collect the source files that are dependencies of the create_gn_rules.py
-# script, below.  Unfortunately, exec_script cannot use a depfile produced
-# by the script and only supports a separately computed list of dependencies.
-zircon_files =
-    exec_script("//build/zircon/list_source_files.py", [], "list lines")
-
-supporting_templates = [
-  "//build/zircon/boards.mako",
-  "//build/zircon/header.mako",
-  "//build/zircon/host_tool.mako",
-  "//build/zircon/main.mako",
-  "//build/zircon/shared_library.mako",
-  "//build/zircon/source_library.mako",
-  "//build/zircon/static_library.mako",
-  "//build/zircon/sysroot.mako",
-]
-
-# The following script generates GN build files for Zircon objects.  It is
-# placed before everything else so that //zircon targets are available in
-# due time.  See //build/zircon/README.md for more details.
-exec_script("//build/zircon/create_gn_rules.py",
-            [
-              "--out",
-              rebase_path("//zircon/public"),
-              "--zircon-build",
-              rebase_path(zircon_root_build_dir),
-              "--zircon-manifest",
-              rebase_path("$zircon_root_build_dir/export/manifest-$target_cpu"),
-            ],
-            "",
-            zircon_files + supporting_templates)
-
-# Write a file that can be sourced by `fx`.  This file is produced
-# by `gn gen` and is not known to Ninja at all, so it has nothing to
-# do with the build itself.  Its sole purpose is to leave bread
-# crumbs about the settings `gn gen` used for `fx` to use later.
-_relative_build_dir = rebase_path(root_build_dir, "//", "//")
-_fx_config_lines = [
-  "# Generated by `gn gen`.",
-  "FUCHSIA_BUILD_DIR='${_relative_build_dir}'",
-  "FUCHSIA_ARCH='${target_cpu}'",
-]
-write_file("$root_build_dir/fx.config", _fx_config_lines)
-
 group("default") {
   deps = [
     ":copy_host_tests",
@@ -70,11 +25,20 @@ group("default") {
 }
 
 group("host_tests") {
-  visibility = [ ":*" ]
+  visibility = [
+    ":*",
+    "//:host_tests",
+  ]
   public_deps = []
   foreach(label, package_host_tests) {
     public_deps += [ "$label($host_toolchain)" ]
   }
+  deps = [
+    # Currently host tests dependencies wind up as dependencies of the packages.
+    # TODO: We should more cleanly separate host targets (including tests) from
+    # packages.
+    "//build/images:packages",
+  ]
 }
 
 # TODO(joshuaseaton|mcgrathr): Make this a formal build_api_module.
@@ -221,13 +185,3 @@ compiled_action("package_archive") {
     "//build/images:updates",
   ]
 }
-
-# Generates a JSON manifest of the platforms available for testing, along with
-# their properties.
-target_platforms = []
-foreach(platform, test_platforms) {
-  if (!defined(platform.cpu) || platform.cpu == current_cpu) {
-    target_platforms += [ platform ]
-  }
-}
-write_file("$root_build_dir/platforms.json", target_platforms, "json")