diff --git a/tooling/src/commonMain/kotlin/lang/temper/tooling/buildrun/Build.kt b/tooling/src/commonMain/kotlin/lang/temper/tooling/buildrun/Build.kt
index 0abd5ad..0e4e54c 100644
--- a/tooling/src/commonMain/kotlin/lang/temper/tooling/buildrun/Build.kt
+++ b/tooling/src/commonMain/kotlin/lang/temper/tooling/buildrun/Build.kt
@@ -115,14 +115,7 @@ fun prepareBuild(
         return null
     }
 
-    val pluggedInConfig = moduleConfig.copy(
-        moduleCustomizeHook = { module, isNew ->
-            moduleConfig.moduleCustomizeHook.customize(module, isNew)
-            for (backendId in supportedBackends) {
-                module.addEnvironmentBindings(lookupFactory(backendId)!!.environmentBindings)
-            }
-        },
-    )
+    val pluggedInConfig = plugInBackendConfigs(moduleConfig)
     return Build(
         harness = h,
         requiredExt = requiredExt,
@@ -131,6 +124,19 @@ fun prepareBuild(
     )
 }
 
+/** Applies environment bindings for [backends]. */
+fun plugInBackendConfigs(
+    moduleConfig: ModuleConfig,
+    backends: List<BackendId> = supportedBackends,
+): ModuleConfig = ModuleConfig(
+    moduleCustomizeHook = { module, isNew ->
+        moduleConfig.moduleCustomizeHook.customize(module, isNew)
+        for (backendId in backends) {
+            module.addEnvironmentBindings(lookupFactory(backendId)!!.environmentBindings)
+        }
+    },
+)
+
 /** [Prepare][prepareBuild]s and executes a build, closing the harness afterward. */
 fun doBuild(
     executorService: ExecutorService,
diff --git a/tooling/src/commonMain/kotlin/lang/temper/tooling/buildrun/Watcher.kt b/tooling/src/commonMain/kotlin/lang/temper/tooling/buildrun/Watcher.kt
index 2138c46..cdecdc5 100644
--- a/tooling/src/commonMain/kotlin/lang/temper/tooling/buildrun/Watcher.kt
+++ b/tooling/src/commonMain/kotlin/lang/temper/tooling/buildrun/Watcher.kt
@@ -229,7 +229,7 @@ class Watcher(
                     previouslyCompiled = lastBuild?.partitionedModules?.flatMap { it.second }
                         ?: emptyList(),
                     runTask = runTask,
-                    moduleConfig = moduleConfig,
+                    moduleConfig = plugInBackendConfigs(moduleConfig),
                     cancelGroup = cancelGroup,
                     beforeStartTranslation = outputDirectoriesFree,
                     includeSnapshot = includeSnapshot,