diff --git a/src/plugins/npm-install-security-scan.release.test.ts b/src/plugins/npm-install-security-scan.release.test.ts
index bd027ce0c6f2..56fccf2041de 100644
--- a/src/plugins/npm-install-security-scan.release.test.ts
+++ b/src/plugins/npm-install-security-scan.release.test.ts
@@ -1,9 +1,9 @@
-import { execFile } from "node:child_process";
-import { copyFileSync, mkdirSync, mkdtempSync, readdirSync, readFileSync, rmSync } from "node:fs";
+import { execFile, spawnSync } from "node:child_process";
+import fs, { copyFileSync, mkdirSync, mkdtempSync, readFileSync, rmSync } from "node:fs";
 import { tmpdir } from "node:os";
 import { dirname, join, relative, resolve, sep } from "node:path";
 import { promisify } from "node:util";
-import { afterEach, describe, expect, it } from "vitest";
+import { afterEach, describe, expect, it, vi } from "vitest";
 import { isScannable, scanDirectoryWithSummary } from "../security/skill-scanner.js";
 
 type NpmPackFile = {
@@ -130,11 +130,73 @@ function stageScannerRelevantPackedFiles(
   return stageDir;
 }
 
-function collectPublishablePluginPackages(): PublishablePluginPackage[] {
-  return readdirSync("extensions", { withFileTypes: true })
+function listPublishablePluginPackageDirs(): string[] {
+  const externalDirs = listExternalPluginPackageDirs();
+  if (externalDirs) {
+    return externalDirs;
+  }
+  return fs
+    .readdirSync("extensions", { withFileTypes: true })
     .filter((entry) => entry.isDirectory())
-    .flatMap((entry) => {
-      const packageDir = join("extensions", entry.name);
+    .map((entry) => join("extensions", entry.name))
+    .toSorted();
+}
+
+function listExternalPluginPackageDirs(): string[] | null {
+  const packageFiles = listGitExtensionPackageFiles() ?? listFindExtensionPackageFiles();
+  if (!packageFiles) {
+    return null;
+  }
+  return packageFiles
+    .flatMap((file) => {
+      const match = /^extensions\/([^/]+)\/package\.json$/u.exec(file);
+      return match?.[1] ? [join("extensions", match[1])] : [];
+    })
+    .toSorted();
+}
+
+function listGitExtensionPackageFiles(): string[] | null {
+  const result = spawnSync("git", ["ls-files", "--", "extensions/*/package.json"], {
+    cwd: process.cwd(),
+    encoding: "utf8",
+    maxBuffer: 1024 * 1024,
+    stdio: ["ignore", "pipe", "ignore"],
+  });
+  if (result.status !== 0) {
+    return null;
+  }
+  return result.stdout
+    .split("\n")
+    .map((line) => line.trim())
+    .filter((line) => line.length > 0)
+    .toSorted();
+}
+
+function listFindExtensionPackageFiles(): string[] | null {
+  const result = spawnSync(
+    "find",
+    [resolve("extensions"), "-maxdepth", "2", "-type", "f", "-name", "package.json"],
+    {
+      cwd: process.cwd(),
+      encoding: "utf8",
+      maxBuffer: 1024 * 1024,
+      stdio: ["ignore", "pipe", "ignore"],
+    },
+  );
+  if (result.status !== 0) {
+    return null;
+  }
+  return result.stdout
+    .split("\n")
+    .map((line) => line.trim())
+    .filter((line) => line.length > 0)
+    .map((file) => relative(process.cwd(), file).split(sep).join("/"))
+    .toSorted();
+}
+
+function collectPublishablePluginPackages(): PublishablePluginPackage[] {
+  return listPublishablePluginPackageDirs()
+    .flatMap((packageDir) => {
       const packageJsonPath = join(packageDir, "package.json");
       let packageJson: {
         name?: unknown;
@@ -231,6 +293,21 @@ async function scanPublishablePluginPackage(plugin: PublishablePluginPackage): P
 }
 
 describe("publishable plugin npm package install security scan", () => {
+  it("lists publishable plugin packages without scanning extension directories in-process", () => {
+    const readDir = vi.spyOn(fs, "readdirSync");
+    try {
+      const packages = collectPublishablePluginPackages();
+
+      expect(packages.length).toBeGreaterThan(0);
+      expect(
+        packages.every((plugin) => plugin.packageDir.split(sep).join("/").startsWith("extensions/")),
+      ).toBe(true);
+      expect(readDir).not.toHaveBeenCalled();
+    } finally {
+      readDir.mockRestore();
+    }
+  });
+
   it("keeps npm-published plugin files clear of unexpected critical hits", async () => {
     const unexpectedCriticalFindings: string[] = [];
     const reviewedCriticalFindings = new Set<string>();