diff --git a/sdk/typescript/scripts/check-package.mjs b/sdk/typescript/scripts/check-package.mjs
index 430da805..bd052933 100644
--- a/sdk/typescript/scripts/check-package.mjs
+++ b/sdk/typescript/scripts/check-package.mjs
@@ -186,12 +186,12 @@ for (const file of files) {
 }
 
 const listing = tar(["-tvzf", archive], "utf8");
-if (/^[^d-]/mu.test(listing)) {
+const listingLines = listing.split(/\r?\n/u).filter(Boolean);
+if (listingLines.some((line) => !/^[d-]/u.test(line))) {
   throw new Error(
     "npm tarball contains a non-regular entry (symbolic or hard link, device, or pipe).",
   );
 }
-const listingLines = listing.split(/\r?\n/u).filter(Boolean);
 if (
   listingLines.length !== entries.length ||
   listingLines.some(
diff --git a/sdk/typescript/tests-ts/check-package.test.ts b/sdk/typescript/tests-ts/check-package.test.ts
new file mode 100644
index 00000000..d31f3a72
--- /dev/null
+++ b/sdk/typescript/tests-ts/check-package.test.ts
@@ -0,0 +1,137 @@
+import {
+  execFileSync,
+  spawnSync,
+  type SpawnSyncReturns,
+} from "node:child_process";
+import { mkdtemp, readdir, rm, writeFile } from "node:fs/promises";
+import { tmpdir } from "node:os";
+import { delimiter, join } from "node:path";
+import { fileURLToPath } from "node:url";
+import { afterAll, describe, expect, test } from "bun:test";
+
+// The `tar` shims below are POSIX shell scripts, so the listing behavior of
+// other platforms is reproduced here rather than exercised natively.
+const testPosix = process.platform === "win32" ? test.skip : test;
+
+const packageRoot = fileURLToPath(new URL("..", import.meta.url));
+const checkPackageScript = fileURLToPath(
+  new URL("../scripts/check-package.mjs", import.meta.url),
+);
+const pluginContract = fileURLToPath(
+  new URL("../plugin-files.json", import.meta.url),
+);
+const temporaryDirectories: string[] = [];
+
+afterAll(async () => {
+  for (const directory of temporaryDirectories) {
+    await rm(directory, { recursive: true, force: true });
+  }
+});
+
+async function temporaryDirectory(prefix: string): Promise<string> {
+  const directory = await mkdtemp(join(tmpdir(), prefix));
+  temporaryDirectories.push(directory);
+  return directory;
+}
+
+let packedTarball: Promise<string> | undefined;
+
+function packTarball(): Promise<string> {
+  packedTarball ??= (async () => {
+    const destination = await temporaryDirectory("codex-security-pack-");
+    const pack = spawnSync(
+      "pnpm",
+      ["pack", "--pack-destination", destination],
+      { cwd: packageRoot, encoding: "utf8" },
+    );
+    if (pack.status !== 0) throw new Error(`pnpm pack failed: ${pack.stderr}`);
+    const tarball = (await readdir(destination)).find((name) =>
+      name.endsWith(".tgz"),
+    );
+    if (tarball === undefined) {
+      throw new Error("pnpm pack did not produce a tarball.");
+    }
+    return join(destination, tarball);
+  })();
+  return packedTarball;
+}
+
+// Rewrites only the verbose listing that the entry-type check reads. Every
+// other invocation reaches the real `tar`, so the archive stays valid and the
+// files extracted from it are untouched.
+async function tarShimPath(filter: string): Promise<string> {
+  const directory = await temporaryDirectory("codex-security-tar-shim-");
+  const realTar = execFileSync("which", ["tar"], { encoding: "utf8" }).trim();
+  await writeFile(
+    join(directory, "tar"),
+    [
+      "#!/bin/sh",
+      'for arg in "$@"; do',
+      '  if [ "$arg" = "-tvzf" ]; then',
+      `    "${realTar}" "$@" | ${filter}`,
+      "    exit $?",
+      "  fi",
+      "done",
+      `exec "${realTar}" "$@"`,
+      "",
+    ].join("\n"),
+    { mode: 0o700 },
+  );
+  return directory;
+}
+
+async function checkPackage(
+  archive: string,
+  shimDirectory?: string,
+): Promise<SpawnSyncReturns<string>> {
+  const path = process.env["PATH"] ?? "";
+  return spawnSync(
+    process.execPath,
+    [checkPackageScript, archive, pluginContract],
+    {
+      encoding: "utf8",
+      env: {
+        ...process.env,
+        PATH:
+          shimDirectory === undefined
+            ? path
+            : `${shimDirectory}${delimiter}${path}`,
+      },
+      timeout: 30_000,
+    },
+  );
+}
+
+describe("npm tarball package check", () => {
+  testPosix(
+    "accepts a valid tarball listed with CRLF line endings",
+    async () => {
+      const tarball = await packTarball();
+
+      const native = await checkPackage(tarball);
+      expect(native.stderr).toBe("");
+      expect(native.status).toBe(0);
+
+      // Windows `tar` terminates listing lines with CRLF. A multiline regular
+      // expression treats the CR as a line terminator of its own, so the
+      // trailing LF used to be inspected as an entry in its own right.
+      const crlf = await checkPackage(
+        tarball,
+        await tarShimPath(`awk '{printf "%s\\r\\n", $0}'`),
+      );
+      expect(crlf.stderr).toBe("");
+      expect(crlf.status).toBe(0);
+    },
+  );
+
+  testPosix("still rejects a tarball holding a non-regular entry", async () => {
+    const rejected = await checkPackage(
+      await packTarball(),
+      await tarShimPath("sed 's#^-#l#'"),
+    );
+    expect(rejected.status).not.toBe(0);
+    expect(rejected.stderr).toContain(
+      "npm tarball contains a non-regular entry",
+    );
+  });
+});