diff --git a/scripts/lib/bundled-runtime-deps-install.mjs b/scripts/lib/bundled-runtime-deps-install.mjs
new file mode 100644
index 00000000000..730bc727bd8
--- /dev/null
+++ b/scripts/lib/bundled-runtime-deps-install.mjs
@@ -0,0 +1,66 @@
+import { spawnSync } from "node:child_process";
+
+export function createNestedNpmInstallEnv(env = process.env) {
+  const nextEnv = { ...env };
+  delete nextEnv.npm_config_global;
+  delete nextEnv.npm_config_location;
+  delete nextEnv.npm_config_prefix;
+  return nextEnv;
+}
+
+export function createBundledRuntimeDependencyInstallEnv(env = process.env, options = {}) {
+  const nextEnv = {
+    ...createNestedNpmInstallEnv(env),
+    npm_config_dry_run: "false",
+    npm_config_fetch_retries: env.npm_config_fetch_retries ?? "5",
+    npm_config_fetch_retry_maxtimeout: env.npm_config_fetch_retry_maxtimeout ?? "120000",
+    npm_config_fetch_retry_mintimeout: env.npm_config_fetch_retry_mintimeout ?? "10000",
+    npm_config_fetch_timeout: env.npm_config_fetch_timeout ?? "300000",
+    npm_config_legacy_peer_deps: "true",
+    npm_config_package_lock: "false",
+    npm_config_save: "false",
+  };
+  if (options.ci) {
+    nextEnv.CI = "1";
+  }
+  if (options.quiet) {
+    Object.assign(nextEnv, {
+      npm_config_audit: "false",
+      npm_config_fund: "false",
+      npm_config_loglevel: "error",
+      npm_config_progress: "false",
+      npm_config_yes: "true",
+    });
+  }
+  return nextEnv;
+}
+
+export function createBundledRuntimeDependencyInstallArgs(specs = [], options = {}) {
+  return [
+    "install",
+    ...(options.noAudit ? ["--no-audit"] : []),
+    ...(options.noFund ? ["--no-fund"] : []),
+    "--ignore-scripts",
+    ...(options.silent ? ["--silent"] : []),
+    ...specs,
+  ];
+}
+
+export function runBundledRuntimeDependencyNpmInstall(params) {
+  const runSpawnSync = params.spawnSyncImpl ?? spawnSync;
+  const result = runSpawnSync(params.npmRunner.command, params.npmRunner.args, {
+    cwd: params.cwd,
+    encoding: "utf8",
+    env: params.env ?? params.npmRunner.env ?? process.env,
+    shell: params.npmRunner.shell,
+    stdio: params.stdio ?? "pipe",
+    ...(params.timeoutMs ? { timeout: params.timeoutMs } : {}),
+    windowsHide: true,
+    windowsVerbatimArguments: params.npmRunner.windowsVerbatimArguments,
+  });
+  if (result.status === 0) {
+    return;
+  }
+  const output = [result.stderr, result.stdout].filter(Boolean).join("\n").trim();
+  throw new Error(output || "npm install failed");
+}
diff --git a/scripts/postinstall-bundled-plugins.mjs b/scripts/postinstall-bundled-plugins.mjs
index f49158ef32d..a4a1ad50527 100644
--- a/scripts/postinstall-bundled-plugins.mjs
+++ b/scripts/postinstall-bundled-plugins.mjs
@@ -24,8 +24,20 @@ import {
 import { tmpdir } from "node:os";
 import { basename, dirname, isAbsolute, join, posix, relative } from "node:path";
 import { fileURLToPath, pathToFileURL } from "node:url";
+import {
+  createBundledRuntimeDependencyInstallArgs,
+  createBundledRuntimeDependencyInstallEnv,
+  createNestedNpmInstallEnv,
+  runBundledRuntimeDependencyNpmInstall,
+} from "./lib/bundled-runtime-deps-install.mjs";
 import { resolveNpmRunner } from "./npm-runner.mjs";
 
+export {
+  createBundledRuntimeDependencyInstallArgs,
+  createBundledRuntimeDependencyInstallEnv,
+  createNestedNpmInstallEnv,
+};
+
 export const BUNDLED_PLUGIN_INSTALL_TARGETS = [];
 
 const __dirname = dirname(fileURLToPath(import.meta.url));
@@ -582,32 +594,6 @@ export function discoverBundledPluginRuntimeDeps(params = {}) {
     .toSorted((a, b) => a.name.localeCompare(b.name));
 }
 
-export function createNestedNpmInstallEnv(env = process.env) {
-  const nextEnv = { ...env };
-  delete nextEnv.npm_config_global;
-  delete nextEnv.npm_config_location;
-  delete nextEnv.npm_config_prefix;
-  return nextEnv;
-}
-
-export function createBundledRuntimeDependencyInstallEnv(env = process.env) {
-  return {
-    ...createNestedNpmInstallEnv(env),
-    npm_config_dry_run: "false",
-    npm_config_fetch_retries: env.npm_config_fetch_retries ?? "5",
-    npm_config_fetch_retry_maxtimeout: env.npm_config_fetch_retry_maxtimeout ?? "120000",
-    npm_config_fetch_retry_mintimeout: env.npm_config_fetch_retry_mintimeout ?? "10000",
-    npm_config_fetch_timeout: env.npm_config_fetch_timeout ?? "300000",
-    npm_config_legacy_peer_deps: "true",
-    npm_config_package_lock: "false",
-    npm_config_save: "false",
-  };
-}
-
-export function createBundledRuntimeDependencyInstallArgs(missingSpecs) {
-  return ["install", "--ignore-scripts", ...missingSpecs];
-}
-
 function shouldEagerInstallBundledPluginDeps(env = process.env) {
   return env?.[EAGER_BUNDLED_PLUGIN_DEPS_ENV]?.trim() === "1";
 }
@@ -1003,19 +989,12 @@ export function runBundledPluginPostinstall(params = {}) {
         comSpec: params.comSpec,
         npmArgs: createBundledRuntimeDependencyInstallArgs(missingSpecs),
       });
-    const result = spawn(npmRunner.command, npmRunner.args, {
+    runBundledRuntimeDependencyNpmInstall({
       cwd: packageRoot,
-      encoding: "utf8",
+      npmRunner,
       env: npmRunner.env ?? installEnv,
-      stdio: "pipe",
-      windowsHide: true,
-      shell: npmRunner.shell,
-      windowsVerbatimArguments: npmRunner.windowsVerbatimArguments,
+      spawnSyncImpl: spawn,
     });
-    if (result.status !== 0) {
-      const output = [result.stderr, result.stdout].filter(Boolean).join("\n").trim();
-      throw new Error(output || "npm install failed");
-    }
     log.log(`[postinstall] installed bundled plugin deps: ${missingSpecs.join(", ")}`);
   } catch (e) {
     // Non-fatal: gateway will surface the missing dep via doctor.
diff --git a/scripts/stage-bundled-plugin-runtime-deps.mjs b/scripts/stage-bundled-plugin-runtime-deps.mjs
index eb929f8e0ec..02a37e0a289 100644
--- a/scripts/stage-bundled-plugin-runtime-deps.mjs
+++ b/scripts/stage-bundled-plugin-runtime-deps.mjs
@@ -1,10 +1,14 @@
-import { spawnSync } from "node:child_process";
 import { createHash } from "node:crypto";
 import fs from "node:fs";
 import path from "node:path";
 import { performance } from "node:perf_hooks";
 import { pathToFileURL } from "node:url";
 import semverSatisfies from "semver/functions/satisfies.js";
+import {
+  createBundledRuntimeDependencyInstallArgs,
+  createBundledRuntimeDependencyInstallEnv,
+  runBundledRuntimeDependencyNpmInstall,
+} from "./lib/bundled-runtime-deps-install.mjs";
 import { resolveNpmRunner } from "./npm-runner.mjs";
 
 const TRANSIENT_TEMP_REMOVE_ERROR_CODES = new Set(["EBUSY", "ENOTEMPTY", "EPERM"]);
@@ -905,39 +909,17 @@ function createRuntimeInstallManifest(pluginId, pinnedGroups) {
 }
 
 function runNpmInstall(params) {
-  const npmEnv = {
-    ...(params.npmRunner.env ?? process.env),
-    CI: "1",
-    npm_config_audit: "false",
-    npm_config_dry_run: "false",
-    npm_config_fetch_retries: process.env.npm_config_fetch_retries ?? "5",
-    npm_config_fetch_retry_maxtimeout: process.env.npm_config_fetch_retry_maxtimeout ?? "120000",
-    npm_config_fetch_retry_mintimeout: process.env.npm_config_fetch_retry_mintimeout ?? "10000",
-    npm_config_fetch_timeout: process.env.npm_config_fetch_timeout ?? "300000",
-    npm_config_fund: "false",
-    npm_config_legacy_peer_deps: "true",
-    npm_config_loglevel: "error",
-    npm_config_package_lock: "false",
-    npm_config_progress: "false",
-    npm_config_save: "false",
-    npm_config_yes: "true",
-  };
-  const runSpawnSync = params.spawnSyncImpl ?? spawnSync;
-  const result = runSpawnSync(params.npmRunner.command, params.npmRunner.args, {
+  return runBundledRuntimeDependencyNpmInstall({
     cwd: params.cwd,
-    encoding: "utf8",
-    env: npmEnv,
-    shell: params.npmRunner.shell,
+    npmRunner: params.npmRunner,
+    env: createBundledRuntimeDependencyInstallEnv(params.npmRunner.env ?? process.env, {
+      ci: true,
+      quiet: true,
+    }),
+    spawnSyncImpl: params.spawnSyncImpl,
     stdio: ["ignore", "pipe", "pipe"],
     timeout: params.timeoutMs ?? 5 * 60 * 1000,
-    windowsHide: true,
-    windowsVerbatimArguments: params.npmRunner.windowsVerbatimArguments,
   });
-  if (result.status === 0) {
-    return;
-  }
-  const output = [result.stderr, result.stdout].filter(Boolean).join("\n").trim();
-  throw new Error(output || "npm install failed");
 }
 
 function resolveLegacyRuntimeDepsStampPath(pluginDir) {
@@ -1203,7 +1185,11 @@ function installPluginRuntimeDeps(params) {
       runNpmInstall({
         cwd: tempInstallDir,
         npmRunner: resolveNpmRunner({
-          npmArgs: ["install", "--no-audit", "--no-fund", "--ignore-scripts", "--silent"],
+          npmArgs: createBundledRuntimeDependencyInstallArgs([], {
+            noAudit: true,
+            noFund: true,
+            silent: true,
+          }),
         }),
       });
     }