diff --git a/sdk/typescript/src/runtime.ts b/sdk/typescript/src/runtime.ts
index 4a09a894..66f6baff 100644
--- a/sdk/typescript/src/runtime.ts
+++ b/sdk/typescript/src/runtime.ts
@@ -64,6 +64,9 @@ const CREDENTIAL_LOCK_NAME = ".codex-security-scan.lock";
 const CREDENTIAL_LOGOUT_MARKER = ".codex-security-logged-out";
 const CREDENTIAL_LOCK_POLL_MILLISECONDS = 25;
 const INCOMPLETE_CREDENTIAL_LOCK_MILLISECONDS = 30_000;
+// `process.kill` narrows its pid to a 32-bit signed integer and rejects anything that
+// does not survive the round trip, so a larger value can never name a process.
+const MAX_PROCESS_ID = 2_147_483_647;
 
 export interface PluginInstall {
   pluginRoot: string;
@@ -418,9 +421,21 @@ async function recoverStaleCredentialHomeLock(lock: string): Promise<boolean> {
     }
   }
 
-  if (isRecord(owner) && typeof owner["pid"] === "number") {
+  // Only a positive integer within the pid range names a process. `process.kill` reads 0
+  // as the caller's own process group and -1 as every process it may signal, so both
+  // always report a live owner and would hold the lock open forever, and a fractional or
+  // out-of-range value makes it throw an argument error that is neither ESRCH nor EPERM
+  // and escapes raw. An owner that cannot be identified is treated like a missing one, so
+  // the age check below still reclaims the lock.
+  const ownerPid = isRecord(owner) ? owner["pid"] : undefined;
+  if (
+    typeof ownerPid === "number" &&
+    Number.isInteger(ownerPid) &&
+    ownerPid > 0 &&
+    ownerPid <= MAX_PROCESS_ID
+  ) {
     try {
-      process.kill(owner["pid"], 0);
+      process.kill(ownerPid, 0);
       return false;
     } catch (error) {
       if (nodeErrorCode(error) !== "ESRCH") {
diff --git a/sdk/typescript/tests-ts/runtime.test.ts b/sdk/typescript/tests-ts/runtime.test.ts
index 7cb55da3..1624dca2 100644
--- a/sdk/typescript/tests-ts/runtime.test.ts
+++ b/sdk/typescript/tests-ts/runtime.test.ts
@@ -15,6 +15,7 @@ import {
   stat,
   symlink,
   truncate,
+  utimes,
   writeFile,
 } from "node:fs/promises";
 import * as fsPromises from "node:fs/promises";
@@ -1632,6 +1633,45 @@ describe("runtime directories and plugin Python boundary", () => {
     expect(existsSync(lock)).toBe(false);
   });
 
+  test("recovers credential-home locks whose owner names no process", async () => {
+    const root = await temporaryDirectory();
+    const home = await prepareCodexSecurityCredentialHome({
+      CODEX_SECURITY_STATE_DIR: join(root, "state"),
+    });
+    const lock = join(home, ".codex-security-scan.lock");
+    // `process.kill` reads 0 as the caller's own process group and -1 as every process
+    // it may signal, so both report a live owner forever, and a fractional pid, a pid
+    // just past the signed 32-bit range, or one past the safe-integer range makes it
+    // throw an argument error instead. None of them identifies a process holding this
+    // lock, so an aged lock naming one has to be reclaimed like any other stale lock.
+    for (const pid of [0, -1, 0.5, 2 ** 31, 2 ** 53]) {
+      await mkdir(lock, { mode: 0o700 });
+      await writeFile(
+        join(lock, "owner.json"),
+        `${JSON.stringify({ pid, token: "unidentifiable-owner" })}\n`,
+        { mode: 0o600 },
+      );
+      const aged = new Date(Date.now() - 10 * 60_000);
+      await utimes(lock, aged, aged);
+
+      // An owner that is treated as live is waited on forever, so the acquisition is
+      // bounded here to fail the test rather than hang it.
+      const abort = new AbortController();
+      const timer = setTimeout(() => abort.abort(), 5_000);
+      try {
+        const release = await acquireCodexSecurityCredentialHomeLock(
+          home,
+          abort.signal,
+        );
+        expect(existsSync(lock)).toBe(true);
+        await release();
+      } finally {
+        clearTimeout(timer);
+      }
+      expect(existsSync(lock)).toBe(false);
+    }
+  });
+
   test("prevents ambient credential imports after an explicit logout", async () => {
     const root = await temporaryDirectory();
     const home = await prepareCodexSecurityCredentialHome({