diff --git a/apps/server/src/cloud/pinnedRuntime.test.ts b/apps/server/src/cloud/pinnedRuntime.test.ts
index a0ca9e5f0fa0..4755b05d5830 100644
--- a/apps/server/src/cloud/pinnedRuntime.test.ts
+++ b/apps/server/src/cloud/pinnedRuntime.test.ts
@@ -228,6 +228,67 @@ it.layer(NodeServices.layer)("ensurePinnedRuntimeInstalled", (it) => {
     }),
   );
 
+  it.effect("drops every spelling of the inherited allow-scripts policy from the installer", () =>
+    Effect.gen(function* () {
+      const fs = yield* FileSystem.FileSystem;
+      const path = yield* Path.Path;
+      const baseDir = yield* fs.makeTempDirectoryScoped({ prefix: "t3-pinned-runtime-env-" });
+      // npx exports the lowercase name and npm reads the uppercase one just the
+      // same. Unrelated npm configuration must still reach the child.
+      const stubbed = {
+        npm_config_allow_scripts: "true",
+        NPM_CONFIG_ALLOW_SCRIPTS: "true",
+        npm_config_registry: "https://registry.example.test/",
+      };
+      const previous = Object.fromEntries(
+        Object.keys(stubbed).map((key) => [key, process.env[key]]),
+      );
+      Object.assign(process.env, stubbed);
+      yield* Effect.addFinalizer(() =>
+        Effect.sync(() => {
+          for (const [key, value] of Object.entries(previous)) {
+            if (value === undefined) delete process.env[key];
+            else process.env[key] = value;
+          }
+        }),
+      );
+
+      // Spawn a real child with exactly what the installer hands npm, so the
+      // assertion covers the environment the child sees rather than the input.
+      const real = yield* Effect.service(ProcessRunner.ProcessRunner).pipe(
+        Effect.provide(ProcessRunner.layer),
+      );
+      const inner = successfulRunner(fs, path);
+      let childEnv: Record<string, string | undefined> | undefined;
+      const runner = ProcessRunner.ProcessRunner.of({
+        run: (input) =>
+          Effect.gen(function* () {
+            const probe = yield* real.run({
+              ...input,
+              command: process.execPath,
+              args: ["-e", "process.stdout.write(JSON.stringify(process.env))"],
+            });
+            childEnv = JSON.parse(probe.stdout) as Record<string, string | undefined>;
+            return yield* inner.run(input);
+          }),
+      });
+
+      yield* ensurePinnedRuntimeInstalled({
+        baseDir,
+        version: "1.2.3",
+        fs,
+        path,
+        runner,
+        validate: () => Effect.void,
+      });
+
+      assert.isDefined(childEnv);
+      assert.notProperty(childEnv, "npm_config_allow_scripts");
+      assert.notProperty(childEnv, "NPM_CONFIG_ALLOW_SCRIPTS");
+      assert.equal(childEnv.npm_config_registry, "https://registry.example.test/");
+    }),
+  );
+
   it.effect("removes staging when installation is interrupted", () =>
     Effect.gen(function* () {
       const fs = yield* FileSystem.FileSystem;
diff --git a/apps/server/src/cloud/pinnedRuntime.ts b/apps/server/src/cloud/pinnedRuntime.ts
index 534ed917218f..4be012164d49 100644
--- a/apps/server/src/cloud/pinnedRuntime.ts
+++ b/apps/server/src/cloud/pinnedRuntime.ts
@@ -6,6 +6,7 @@ import * as PlatformError from "effect/PlatformError";
 import * as Schema from "effect/Schema";
 import * as Option from "effect/Option";
 import * as Semaphore from "effect/Semaphore";
+import { HostProcessEnvironment } from "@t3tools/shared/hostProcess";
 
 import * as ProcessRunner from "../processRunner.ts";
 
@@ -161,10 +162,22 @@ const installPinnedRuntime = Effect.fn("cloud.pinned_runtime.ensure_installed")(
       "--no-audit",
       `t3@${input.version}`,
     ];
+    // npx exports its resolved allow-scripts policy as npm_config_allow_scripts,
+    // which npm 12 reads as a project-scoped --allow-scripts and refuses with
+    // EALLOWSCRIPTS. npm matches config variable names case-insensitively, so
+    // unset every spelling the child would inherit (Node drops undefined
+    // entries) and leave the rest of the npm configuration alone.
+    const hostEnvironment = yield* HostProcessEnvironment;
+    const installEnv = Object.fromEntries(
+      Object.keys(hostEnvironment)
+        .filter((key) => /^npm_config_allow[-_]scripts$/i.test(key))
+        .map((key) => [key, undefined]),
+    );
     yield* runner
       .run({
         command: "npm",
         args: installArgs,
+        env: installEnv,
         // Native dependencies may compile from source on slower machines.
         timeout: PINNED_RUNTIME_INSTALL_TIMEOUT,
       })
@@ -178,6 +191,7 @@ const installPinnedRuntime = Effect.fn("cloud.pinned_runtime.ensure_installed")(
                 runner.run({
                   command: "pnpm",
                   args: ["--package=npm@11", "dlx", "npm", ...installArgs],
+                  env: installEnv,
                   timeout: PINNED_RUNTIME_INSTALL_TIMEOUT,
                 })
               : Effect.fail(error),