diff --git a/apps/cli/src/__tests__/helpers/fake-npm.ts b/apps/cli/src/__tests__/helpers/fake-npm.ts
index 0a622d173..b7c94bebc 100644
--- a/apps/cli/src/__tests__/helpers/fake-npm.ts
+++ b/apps/cli/src/__tests__/helpers/fake-npm.ts
@@ -53,6 +53,14 @@ if (process.env.BB_TEST_NPM_INSTALL === "fail") {
   process.exit(1);
 }
 
+if (process.env.BB_TEST_NPM_INSTALL === "fail-noisy-stdout") {
+  process.stderr.write("npm error code EPERM\\nnpm error syscall open\\n");
+  for (let line = 1; line <= 9; line += 1) {
+    process.stdout.write("progress line " + line + "\\n");
+  }
+  process.exit(1);
+}
+
 // npm treats NODE_ENV=production as omit=dev; a command-line --include=dev
 // outranks it. BB_TEST_NPM_ALWAYS_OMIT_DEV forces the omission to stand in for
 // an install that silently drops packages.
diff --git a/apps/cli/src/__tests__/plugin-new.test.ts b/apps/cli/src/__tests__/plugin-new.test.ts
index e2bfc7281..abb8fb883 100644
--- a/apps/cli/src/__tests__/plugin-new.test.ts
+++ b/apps/cli/src/__tests__/plugin-new.test.ts
@@ -214,6 +214,14 @@ describe.sequential("bb plugin new dependency install", () => {
     expect(warnings).toContain("Your cache folder contains root-owned files");
   });
 
+  it("keeps stderr details when a failed install also writes stdout", async () => {
+    vi.stubEnv("BB_TEST_NPM_INSTALL", "fail-noisy-stdout");
+
+    await runPluginNew(["npm-noisy"]);
+
+    expect(warned.join("\n")).toContain("npm error code EPERM");
+  });
+
   it("falls back to the manual step when npm is not on PATH", async () => {
     vi.stubEnv("PATH", join(workDir, "empty-bin"));