diff --git a/build/configure/src/proto.rs b/build/configure/src/proto.rs
index 0fcbaadeb..2a046bd68 100644
--- a/build/configure/src/proto.rs
+++ b/build/configure/src/proto.rs
@@ -35,8 +35,7 @@ pub fn setup_protoc(build: &mut Build) -> Result<()> {
             inputs![":extract:protoc:bin"]
         }
     };
-    let protoc_binary = build.expand_inputs(protoc_binary);
-    build.variable("protoc_binary", &protoc_binary[0]);
+    build.add_dependency("protoc_binary", protoc_binary);
     Ok(())
 }
 
diff --git a/build/configure/src/python.rs b/build/configure/src/python.rs
index 815a4f00b..915f76bcc 100644
--- a/build/configure/src/python.rs
+++ b/build/configure/src/python.rs
@@ -106,7 +106,7 @@ impl BuildAction for GenPythonProto {
             })
             .collect();
         build.add_inputs("in", &self.proto_files);
-        build.add_inputs("protoc", inputs!["$protoc_binary"]);
+        build.add_inputs("protoc", inputs![":protoc_binary"]);
         build.add_inputs("protoc-gen-mypy", inputs![":pyenv:protoc-gen-mypy"]);
         build.add_outputs("", python_outputs);
         // not a direct dependency, but we include the output interface in our declared
diff --git a/build/configure/src/rust.rs b/build/configure/src/rust.rs
index fbf72527d..c51412f64 100644
--- a/build/configure/src/rust.rs
+++ b/build/configure/src/rust.rs
@@ -87,7 +87,7 @@ fn prepare_proto_descriptors(build: &mut Build) -> Result<()> {
     build.add_action(
         "rslib:proto",
         CargoBuild {
-            inputs: inputs![glob!["{proto,rslib/proto}/**"], "$protoc_binary",],
+            inputs: inputs![glob!["{proto,rslib/proto}/**"], ":protoc_binary",],
             outputs: &[RustOutput::Data(
                 "descriptors.bin",
                 "$builddir/rslib/proto/descriptors.bin",
diff --git a/build/ninja_gen/src/build.rs b/build/ninja_gen/src/build.rs
index 51e961875..ffa93611f 100644
--- a/build/ninja_gen/src/build.rs
+++ b/build/ninja_gen/src/build.rs
@@ -144,7 +144,8 @@ rule {action_name}
 
     /// Allows you to add dependencies on files or build steps that aren't
     /// required to build the group itself, but are required by consumers of
-    /// that group.
+    /// that group. Can also be used to allow substitution of local binaries
+    /// for downloaded ones (eg :node_binary).
     pub fn add_dependency(&mut self, group: &str, deps: BuildInput) {
         let files = self.expand_inputs(deps);
         let groups = split_groups(group);
diff --git a/build/ninja_gen/src/node.rs b/build/ninja_gen/src/node.rs
index 2c7325994..451865458 100644
--- a/build/ninja_gen/src/node.rs
+++ b/build/ninja_gen/src/node.rs
@@ -52,7 +52,7 @@ impl BuildAction for YarnSetup {
     }
 
     fn files(&mut self, build: &mut impl build::FilesHandle) {
-        build.add_inputs("", inputs!["$node_binary"]);
+        build.add_inputs("", inputs![":node_binary"]);
         build.add_outputs_ext(
             "bin",
             vec![if cfg!(windows) {
@@ -128,8 +128,7 @@ pub fn setup_node(
             inputs![":extract:node:bin"]
         }
     };
-    let node_binary = build.expand_inputs(node_binary);
-    build.variable("node_binary", &node_binary[0]);
+    build.add_dependency("node_binary", node_binary);
 
     match std::env::var("YARN_BINARY") {
         Ok(path) => {
@@ -176,7 +175,7 @@ impl BuildAction for EsbuildScript<'_> {
     }
 
     fn files(&mut self, build: &mut impl build::FilesHandle) {
-        build.add_inputs("node_bin", inputs!["$node_binary"]);
+        build.add_inputs("node_bin", inputs![":node_binary"]);
         build.add_inputs("script", &self.script);
         build.add_inputs("entrypoint", &self.entrypoint);
         build.add_inputs("", inputs!["yarn.lock", ":node_modules", &self.deps]);
@@ -368,7 +367,7 @@ impl BuildAction for GenTypescriptProto<'_> {
                 .map(|d| format!("-I {d}"))
                 .join(" "),
         );
-        build.add_inputs("protoc", inputs!["$protoc_binary"]);
+        build.add_inputs("protoc", inputs![":protoc_binary"]);
         build.add_inputs("gen-es", inputs![":node_modules:protoc-gen-es"]);
         if cfg!(windows) {
             build.add_env_var(
diff --git a/build/ninja_gen/src/python.rs b/build/ninja_gen/src/python.rs
index e95346054..f16da6f3d 100644
--- a/build/ninja_gen/src/python.rs
+++ b/build/ninja_gen/src/python.rs
@@ -75,8 +75,7 @@ pub fn setup_python(build: &mut Build) -> Result<()> {
             inputs![":extract:python:bin"]
         }
     };
-    let python_binary = build.expand_inputs(python_binary);
-    build.variable("python_binary", &python_binary[0]);
+    build.add_dependency("python_binary", python_binary);
     Ok(())
 }
 
@@ -103,7 +102,7 @@ impl BuildAction for PythonEnvironment {
             vec![path]
         };
 
-        build.add_inputs("python_binary", inputs!["$python_binary"]);
+        build.add_inputs("python_binary", inputs![":python_binary"]);
         build.add_inputs("base_requirements", &self.base_requirements_txt);
         build.add_inputs("requirements", &self.requirements_txt);
         build.add_variable("pyenv_folder", self.folder);