diff --git a/plugins/codex/scripts/lib/state.mjs b/plugins/codex/scripts/lib/state.mjs
index 2da23498..11e12663 100644
--- a/plugins/codex/scripts/lib/state.mjs
+++ b/plugins/codex/scripts/lib/state.mjs
@@ -150,6 +150,36 @@ export function listJobs(cwd) {
   return loadState(cwd).jobs;
 }
 
+/**
+ * Check whether a process with the given pid is currently alive.
+ * Cross-platform: uses `process.kill(pid, 0)` which sends signal 0
+ * (no-op signal) and throws ESRCH if the process is gone. EPERM means
+ * the process exists but we lack permission to signal it (still alive).
+ */
+export function isPidAlive(pid) {
+  if (!pid || typeof pid !== "number") return false;
+  try {
+    process.kill(pid, 0);
+    return true;
+  } catch (err) {
+    return err && err.code === "EPERM";
+  }
+}
+
+/**
+ * A job counts as "active" only if its status says queued/running AND
+ * the recorded pid is still alive. This prevents zombie state from
+ * causing false alarms when the codex process was SIGKILL'd
+ * (e.g., by a cleanup script or an OS reboot) without getting a chance
+ * to write status="completed" to disk.
+ */
+export function isJobActive(job) {
+  if (!job) return false;
+  if (job.status !== "queued" && job.status !== "running") return false;
+  if (!job.pid) return false;
+  return isPidAlive(job.pid);
+}
+
 export function setConfig(cwd, key, value) {
   return updateState(cwd, (state) => {
     state.config = {
diff --git a/plugins/codex/scripts/stop-review-gate-hook.mjs b/plugins/codex/scripts/stop-review-gate-hook.mjs
index 2346bdcf..5bec0f75 100644
--- a/plugins/codex/scripts/stop-review-gate-hook.mjs
+++ b/plugins/codex/scripts/stop-review-gate-hook.mjs
@@ -8,7 +8,7 @@ import { fileURLToPath } from "node:url";
 
 import { getCodexAvailability } from "./lib/codex.mjs";
 import { loadPromptTemplate, interpolateTemplate } from "./lib/prompts.mjs";
-import { getConfig, listJobs } from "./lib/state.mjs";
+import { getConfig, isJobActive, listJobs } from "./lib/state.mjs";
 import { sortJobsNewestFirst } from "./lib/job-control.mjs";
 import { SESSION_ID_ENV } from "./lib/tracked-jobs.mjs";
 import { resolveWorkspaceRoot } from "./lib/workspace.mjs";
@@ -146,7 +146,7 @@ function main() {
   const config = getConfig(workspaceRoot);
 
   const jobs = sortJobsNewestFirst(filterJobsForCurrentSession(listJobs(workspaceRoot), input));
-  const runningJob = jobs.find((job) => job.status === "queued" || job.status === "running");
+  const runningJob = jobs.find(isJobActive);
   const runningTaskNote = runningJob
     ? `Codex task ${runningJob.id} is still running. Check /codex:status and use /codex:cancel ${runningJob.id} if you want to stop it before ending the session.`
     : null;