diff --git a/intellij/localconfig/localconfig.go b/intellij/localconfig/localconfig.go
new file mode 100644
index 0000000..44ef730
--- /dev/null
+++ b/intellij/localconfig/localconfig.go
@@ -0,0 +1,50 @@
+// Copyright 2020 The Monogon Project Authors.
+//
+// SPDX-License-Identifier: Apache-2.0
+//
+// 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.
+
+// localconfig modifies the project's IntelliJ config to include project-specific settings. This is usually done by
+// checking in the .idea directory, but we do not want to do this: it conflicts with the Bazel plugin's way of
+// conducting its workspace business, lacks backwards compatibility, and is a common source of spurious Git diffs,
+// especially when the IDE/JDK/random plugins are updated and team members run different versions.
+//
+// Instead, we use the officially supported way of shipping IntelliJ Bazel project configs - a .bazelproject file that
+// can be imported using the Bazel project import wizard, with local configs. We then use this tool to mangle the local
+// configs to add additional custom configuration beyond run configurations. This avoids merge conflicts and allows us
+// to intelligently handle schema changes.
+//
+package main
+
+import (
+	"log"
+	"os"
+	"path"
+
+	"git.monogon.dev/source/nexantic.git/intellij/localconfig/watchers"
+)
+
+func main() {
+	if len(os.Args) != 2 {
+		log.Fatal("usage: localconfig <project dir>")
+	}
+
+	projectDir := os.Args[1]
+	if _, err := os.Stat(path.Join(projectDir, ".ijwb")); err != nil {
+		log.Fatalf("invalid project dir: %v", err)
+	}
+
+	if err := watchers.RewriteConfig(projectDir); err != nil {
+		log.Fatal(err)
+	}
+}