diff --git a/scripts/assert-registry-content.mjs b/scripts/assert-registry-content.mjs
new file mode 100644
index 00000000..357f29d4
--- /dev/null
+++ b/scripts/assert-registry-content.mjs
@@ -0,0 +1,162 @@
+#!/usr/bin/env node
+/*
+ * Copyright (c) 2026, Salesforce, Inc.
+ * All rights reserved.
+ * SPDX-License-Identifier: Apache-2.0
+ * For full license text, see the LICENSE file in the repo root or https://www.apache.org/licenses/LICENSE-2.0
+ */
+
+/**
+ * Pre-publish guard for agentscript issue #71: refuse to publish dependents
+ * that would stamp workspace:* onto a reused version whose registry dist
+ * differs from local dist. Complementary to verify-published-packages.mjs (PR #72).
+ * Run after the scope rewrite in scripts/publish.mjs.
+ */
+
+import { execFileSync } from "node:child_process";
+import { createHash } from "node:crypto";
+import { existsSync, mkdtempSync, readFileSync, readdirSync, rmSync, statSync } from "node:fs";
+import { tmpdir } from "node:os";
+import { join, relative } from "node:path";
+
+const ROOT = new URL("..", import.meta.url).pathname;
+const INTERNAL_SCOPE = "@agentscript/";
+const PUBLISH_SCOPE = "@sf-agentscript/";
+
+function walk(dir) {
+  const out = [];
+  for (const entry of readdirSync(dir, { withFileTypes: true })) {
+    const full = join(dir, entry.name);
+    if (entry.isDirectory()) out.push(...walk(full));
+    else if (entry.isFile()) out.push(full);
+  }
+  return out;
+}
+
+function hashDistTree(pkgPath) {
+  const dist = join(pkgPath, "dist");
+  if (!existsSync(dist) || !statSync(dist).isDirectory()) return null;
+  const files = walk(dist).filter((f) => !f.endsWith(".map")).sort();
+  if (files.length === 0) return null;
+  const h = createHash("sha256");
+  for (const file of files) {
+    h.update(relative(dist, file).replaceAll(String.fromCharCode(92), "/"));
+    h.update(Buffer.from([0]));
+    h.update(readFileSync(file));
+    h.update(Buffer.from([0]));
+  }
+  return h.digest("hex");
+}
+
+function publishName(name) {
+  if (name.startsWith(PUBLISH_SCOPE)) return name;
+  if (name.startsWith(INTERNAL_SCOPE)) return name.replace(INTERNAL_SCOPE, PUBLISH_SCOPE);
+  return name;
+}
+
+function npmMeta(name, version) {
+  const url = "https://registry.npmjs.org/" + name.replace("/", "%2F") + "/" + version;
+  try {
+    const raw = execFileSync("curl", ["-sS", "-f", "-L", url], { encoding: "utf8", maxBuffer: 16 * 1024 * 1024 });
+    return JSON.parse(raw);
+  } catch {
+    return null;
+  }
+}
+
+function hashRemoteDist(tarballUrl) {
+  const dir = mkdtempSync(join(tmpdir(), "as-reg-"));
+  const tgz = join(dir, "pkg.tgz");
+  try {
+    execFileSync("curl", ["-sS", "-f", "-L", "-o", tgz, tarballUrl], { maxBuffer: 64 * 1024 * 1024 });
+    execFileSync("tar", ["-xzf", tgz, "-C", dir], { stdio: "pipe" });
+    return hashDistTree(join(dir, "package"));
+  } finally {
+    rmSync(dir, { recursive: true, force: true });
+  }
+}
+
+function readPkgJson(pkgPath) {
+  return JSON.parse(readFileSync(join(pkgPath, "package.json"), "utf8"));
+}
+
+function workspaceScopedDepNames(pkgJson) {
+  const deps = { ...(pkgJson.dependencies || {}), ...(pkgJson.optionalDependencies || {}) };
+  return Object.keys(deps).filter((n) => n.startsWith(INTERNAL_SCOPE) || n.startsWith(PUBLISH_SCOPE));
+}
+console.log("assert registry content");
+const listOut = execFileSync("pnpm", ["-r", "list", "--json", "--depth", "-1"], { cwd: ROOT, encoding: "utf8" });
+const workspacePkgs = JSON.parse(listOut);
+const byPublishName = new Map();
+for (const pkg of workspacePkgs) {
+  const json = readPkgJson(pkg.path);
+  if (json.private) continue;
+  byPublishName.set(publishName(json.name), { path: pkg.path, version: json.version, json });
+}
+
+const stale = [];
+const willPublish = [];
+
+for (const [name, info] of byPublishName) {
+  const localHash = hashDistTree(info.path);
+  if (!localHash) {
+    console.log("  skip " + name + "@" + info.version + " (no dist)");
+    continue;
+  }
+  const meta = npmMeta(name, info.version);
+  if (!meta) {
+    willPublish.push(name);
+    console.log("  new   " + name + "@" + info.version);
+    continue;
+  }
+  const tarball = meta.dist && meta.dist.tarball;
+  if (!tarball) {
+    console.log("  skip " + name + "@" + info.version + " (no tarball)");
+    continue;
+  }
+  const remoteHash = hashRemoteDist(tarball);
+  if (!remoteHash) {
+    console.log("  skip " + name + "@" + info.version + " (remote no dist)");
+    continue;
+  }
+  if (localHash !== remoteHash) {
+    stale.push({ name, version: info.version, localHash, remoteHash });
+    console.log("  STALE " + name + "@" + info.version);
+  } else {
+    console.log("  ok    " + name + "@" + info.version);
+  }
+}
+
+if (stale.length === 0) {
+  console.log("No stale version reuse detected.");
+  process.exit(0);
+}
+
+const staleNames = new Set(stale.map((s) => s.name));
+const blockers = [];
+for (const name of willPublish) {
+  const info = byPublishName.get(name);
+  if (!info) continue;
+  for (const depNameRaw of workspaceScopedDepNames(info.json)) {
+    const depName = publishName(depNameRaw);
+    if (!staleNames.has(depName)) continue;
+    const depInfo = byPublishName.get(depName);
+    blockers.push({
+      pkg: name + "@" + info.version,
+      dep: depName + "@" + (depInfo ? depInfo.version : "?"),
+    });
+  }
+}
+
+if (blockers.length === 0) {
+  console.log("warn: reused version with different dist; no publishing dependent");
+  for (const s of stale) console.log("  - " + s.name + "@" + s.version);
+  process.exit(0);
+}
+console.error("guard failed: dependency pin targets registry content that differs from local dist");
+console.error("see salesforce agentscript issue 71");
+console.error("bad pins:");
+for (const b of blockers) console.error("  - " + b.pkg + " -> STALE " + b.dep);
+console.error("bump stale package versions so workspace protocol stamps a fresh version");
+for (const s of stale) console.error("  stale: " + s.name + "@" + s.version);
+process.exit(1);
diff --git a/scripts/publish.mjs b/scripts/publish.mjs
index 77351597..d4442bca 100644
--- a/scripts/publish.mjs
+++ b/scripts/publish.mjs
@@ -122,7 +122,13 @@ execFileSync('pnpm', ['install', '--no-frozen-lockfile'], {
   stdio: 'inherit',
 });
 
-// Step 5: Publish every public workspace package at the version in its
+// Step 5: Guard against #71 — stale registry content at reused versions
+execFileSync('node', [join(ROOT, 'scripts', 'assert-registry-content.mjs')], {
+  cwd: ROOT,
+  stdio: 'inherit',
+});
+
+// Step 6: Publish every public workspace package at the version in its
 // package.json. `pnpm -r publish` iterates the workspace, skips packages
 // marked `"private": true`, resolves `workspace:*` deps to exact versions in
 // the tarball, and no-ops any version already on the registry — so this is