diff --git a/scripts/lib/bashy-node/node-project/build-main-module b/scripts/lib/bashy-node/node-project/build-main-module
index 74f8020..a77f515 100755
--- a/scripts/lib/bashy-node/node-project/build-main-module
+++ b/scripts/lib/bashy-node/node-project/build-main-module
@@ -153,6 +153,7 @@ function build-project {
     && copy-scripts "${srcMainModule}" "${destDir}" \
     && copy-local-modules "${destLocalModules}" "${deps}" \
     && remove-dead-local-modules "${destLocalModules}" "${deps}" \
+    && run-postinstall-scripts "${destLocalModules}" "$(jget "${deps}" '.postinstallScripts')" \
     || return "$?"
 
     # Do `npm install`, but only if it hasn't yet been done _or_ the top-level
@@ -403,6 +404,34 @@ function remove-dead-local-modules {
     fi
 }
 
+# Runs any `postinstall` scripts defined by local modules.
+function run-postinstall-scripts {
+    local destLocalModules="$1"
+    local scriptModules="$2"
+
+    if [[ ${scriptModules} == '[]' ]]; then
+        return
+    fi
+
+    progress-msg 'Running local-module postinstall scripts...'
+
+    local modArray=()
+    jset-array --raw modArray "${scriptModules}"
+
+    # `(...)` to preserve the `cwd` in this process.
+    (
+        cd "${destLocalModules}"
+        local m
+        for m in "${modArray[@]}"; do
+            progress-msg "Postinstall ${m}..."
+            npm explore "${m}" -- npm run postinstall \
+            || return "$?"
+        done
+    )
+
+    progress-msg 'Done running local-module postinstall scripts.'
+}
+
 # Checks a `node_modules` directory (or similar) for "suspect" files, given a
 # desire to have a platform-agnostic build.
 function suspect-file-check {
diff --git a/scripts/lib/bashy-node/node-project/find-module-dependencies.mjs b/scripts/lib/bashy-node/node-project/find-module-dependencies.mjs
index 37aa26c..0d1a444 100644
--- a/scripts/lib/bashy-node/node-project/find-module-dependencies.mjs
+++ b/scripts/lib/bashy-node/node-project/find-module-dependencies.mjs
@@ -84,6 +84,9 @@ const processed = new Set();
 /** The graph of local module dependencies, as a list of edges. */
 let graph = [];
 
+/** Map from module names to corresponding parsed package files. */
+const packageFiles = new Map();
+
 /** Map from external dependency names to sets of all encountered versions. */
 const extDeps = new Map();
 
@@ -126,6 +129,7 @@ while (unprocessed.size > 0) {
   }
 
   localDirs.set(oneDep, moduleDir);
+  packageFiles.set(oneDep, packageObj);
 
   for (const [key, value] of Object.entries(packageObj.dependencies ?? {})) {
     if (key.startsWith('@this/')) {
@@ -146,11 +150,19 @@ while (unprocessed.size > 0) {
 
 // Build up the final result.
 
+const postinstallScripts = [];
+for (const [name, obj] of packageFiles) {
+  if (obj.scripts?.postinstall) {
+    postinstallScripts.push(name);
+  }
+}
+
 const result = {
-  main:      `@this/${mainModule}`,
-  localDeps: [...localDeps].sort(),
-  localDirs: sortObject(Object.fromEntries(localDirs.entries())),
-  extDeps:   sortObject(Object.fromEntries(extDeps.entries()))
+  main:               `@this/${mainModule}`,
+  localDeps:          [...localDeps].sort(),
+  localDirs:          sortObject(Object.fromEntries(localDirs.entries())),
+  extDeps:            sortObject(Object.fromEntries(extDeps.entries())),
+  postinstallScripts
 };
 
 // `extDeps` has sets for values. Reduce them to single elements, and report an