diff --git a/.gitsubmodules b/.gitsubmodules
new file mode 100644
index 0000000..00f3262
--- /dev/null
+++ b/.gitsubmodules
@@ -0,0 +1,6 @@
+[submodule "kythe"]
+	path = third_party/kythe 
+	url = https://github.com/kythe/kythe
+[submodule "bazel"]
+	path = third_party/bazel
+	url = https://github.com/bazelbuild/bazel
diff --git a/BUILD b/BUILD
index 0528ef0..80e7e1c 100644
--- a/BUILD
+++ b/BUILD
@@ -19,6 +19,12 @@ py_library(
   ],
 )
 
+py_binary(
+  name = "graphdef_from_bazel",
+  srcs = ["graphdef_from_bazel.py"],
+  deps = [":splitbrain"],
+)
+
 py_binary(
   name = "main",
   srcs = ["main.py"],
diff --git a/graphdef_from_bazel.py b/graphdef_from_bazel.py
new file mode 100644
index 0000000..5e99b4e
--- /dev/null
+++ b/graphdef_from_bazel.py
@@ -0,0 +1,43 @@
+"""Extracts a GraphDef based on a Bazel workspace.
+
+This tool launches the Bazel binary to extract some data from a workspace, and
+processes the protocol buffer output to produce a GraphDef.
+
+Usage:
+  ./graphdef_from_bazel.py --input_dir=path/to/WORKSPACE \\
+    --output_dir=path/to/out
+"""
+
+from absl import app
+from absl import flags
+import graphdef_utils
+from third_party.bazel.src.main.protobuf import build_pb2 
+
+FLAGS = flags.FLAGS
+flags.DEFINE_string('input_path', None, 'Path to Bazel WORKSPACE file.')
+flags.DEFINE_string('output_dir', None, 'Directory to write output to.')
+flags.DEFINE_multi_string('modified_files', [],
+                          'List of modified files to `bazel query` for.')
+flags.DEFINE_bool('textproto', False,
+                  'If true, writes output statistics as textproto format.')
+flags.mark_flag_as_required('input_path')
+flags.mark_flag_as_required('output_dir')
+
+
+def main(argv):
+  del argv
+
+  with open(FLAGS.input_path) as f:
+    pass
+
+  # TODO(cameron): Load bazel proto using vendored dependency.
+  # TODO(cameron): Filter on predicates: Must be a working change in the CL? Maybe keep transitive.
+  # TODO(cameron): Find testdata based stuff and make changes bi-directional. Same with proto.
+  # TODO(cameron): Merge bi-directional dependencies.
+  # TODO(cameron): Import tests from internal.
+  # TODO(cameron): Assert the graph is a DAG. Find and merge cycles.
+  graphdef = program_graph_pb2.GraphDef()
+
+
+if __name__ == '__main__':
+  app.run(main)
\ No newline at end of file
diff --git a/testdata/bazel_query_on_repo.binarypb b/testdata/bazel_query_on_repo.binarypb
new file mode 100644
index 0000000..fb4e768
Binary files /dev/null and b/testdata/bazel_query_on_repo.binarypb differ
diff --git a/third_party/README.md b/third_party/README.md
new file mode 100644
index 0000000..005faa2
--- /dev/null
+++ b/third_party/README.md
@@ -0,0 +1 @@
+# third_party