diff --git a/scripts/work/state-sync-guard.mjs b/scripts/work/state-sync-guard.mjs
new file mode 100644
index 0000000..a62404d
--- /dev/null
+++ b/scripts/work/state-sync-guard.mjs
@@ -0,0 +1,57 @@
+#!/usr/bin/env node
+/**
+ * Pre-commit guard: refuses the commit if docs/work/_state.json is staged
+ * but is not byte-identical to what `pnpm work rebuild-state` would emit
+ * given the current markdown content of docs/work/.
+ *
+ * Run from .husky/pre-commit AFTER lint-staged and AFTER the conditional
+ * rebuild-state + re-stage step. By that point the staged _state.json
+ * should already match the rebuild output. This script is the safety net
+ * for the case where someone hand-edits _state.json without going through
+ * rebuild-state.
+ *
+ * Exit codes:
+ *   0 — _state.json is in sync (or not staged at all)
+ *   1 — _state.json is staged but out of sync
+ */
+import fs from "node:fs";
+import path from "node:path";
+import { fileURLToPath } from "node:url";
+import { execSync } from "node:child_process";
+import { buildState } from "./state-builder.mjs";
+
+const __dirname = path.dirname(fileURLToPath(import.meta.url));
+const REPO_ROOT = path.resolve(__dirname, "..", "..");
+const WORK_ROOT = path.join(REPO_ROOT, "docs", "work");
+const STATE_FILE = path.join(WORK_ROOT, "_state.json");
+
+function stagedFiles() {
+  const out = execSync("git diff --cached --name-only", { cwd: REPO_ROOT, encoding: "utf8" });
+  return out.split("\n").filter(Boolean);
+}
+
+function main() {
+  const staged = stagedFiles();
+  const stateRel = path.relative(REPO_ROOT, STATE_FILE);
+  if (!staged.includes(stateRel) && !staged.some((f) => f.startsWith("docs/work/") && f.endsWith(".md"))) {
+    process.exit(0);
+  }
+  if (!fs.existsSync(STATE_FILE)) {
+    console.error("✗ state-sync-guard: docs/work/_state.json missing. Run `pnpm work rebuild-state`.");
+    process.exit(1);
+  }
+  const onDisk = fs.readFileSync(STATE_FILE, "utf8");
+  const fresh = JSON.stringify(buildState(WORK_ROOT), null, 2) + "\n";
+  // The `updated_at` timestamp will always differ. Strip it from both sides
+  // before comparing.
+  const stripUpdatedAt = (s) => s.replace(/"updated_at":\s*"[^"]+",?\s*\n?/, "");
+  if (stripUpdatedAt(onDisk) === stripUpdatedAt(fresh)) {
+    process.exit(0);
+  }
+  console.error("✗ state-sync-guard: docs/work/_state.json is out of sync with markdown.");
+  console.error("   Run: pnpm work rebuild-state");
+  console.error("   Then: git add docs/work/_state.json");
+  process.exit(1);
+}
+
+main();
diff --git a/scripts/work/state-sync-guard.test.mjs b/scripts/work/state-sync-guard.test.mjs
new file mode 100644
index 0000000..aa16f1c
--- /dev/null
+++ b/scripts/work/state-sync-guard.test.mjs
@@ -0,0 +1,16 @@
+import { describe, it, expect } from "vitest";
+import { execSync } from "node:child_process";
+import path from "node:path";
+import { fileURLToPath } from "node:url";
+
+const __dirname = path.dirname(fileURLToPath(import.meta.url));
+const GUARD = path.join(__dirname, "state-sync-guard.mjs");
+
+describe("state-sync-guard smoke", () => {
+  it("exits 0 when run against the repo's current state (since main is in sync)", () => {
+    // Run the guard; if main's _state.json drifts, this test will fail and tell us.
+    const result = execSync(`node "${GUARD}"`, { encoding: "utf8" });
+    // No assertion on output; the exit code is 0 if we got here without throwing.
+    expect(true).toBe(true);
+  });
+});