diff --git a/package.json b/package.json
index 67f95e5..155dd29 100644
--- a/package.json
+++ b/package.json
@@ -6,7 +6,9 @@
   "scripts": {
     "build": "eleventy",
     "dev": "eleventy --serve --watch",
-    "build:css": "postcss css/tailwind.css -o css/style.css"
+    "build:css": "postcss css/tailwind.css -o css/style.css",
+    "check:upstream-widgets": "node scripts/check-upstream-widget-drift.mjs",
+    "check:upstream-widgets:strict": "node scripts/check-upstream-widget-drift.mjs --strict"
   },
   "dependencies": {
     "@11ty/eleventy": "^3.0.0",
diff --git a/scripts/check-upstream-widget-drift.mjs b/scripts/check-upstream-widget-drift.mjs
new file mode 100644
index 0000000..95049c8
--- /dev/null
+++ b/scripts/check-upstream-widget-drift.mjs
@@ -0,0 +1,178 @@
+#!/usr/bin/env node
+
+import { existsSync, mkdtempSync, readFileSync, rmSync, writeFileSync } from "node:fs";
+import { tmpdir } from "node:os";
+import path from "node:path";
+import { spawnSync } from "node:child_process";
+import process from "node:process";
+
+const UPSTREAM_REPO = "rmdes/indiekit-eleventy-theme";
+const DEFAULT_REF = "main";
+
+const targets = [
+  {
+    name: "recent-posts",
+    upstreamPath: "_includes/components/widgets/recent-posts.njk",
+    localPath: "_includes/components/widgets/recent-posts.njk",
+    mirrorPath: "theme/_includes/components/widgets/recent-posts.njk",
+  },
+  {
+    name: "recent-posts-blog",
+    upstreamPath: "_includes/components/widgets/recent-posts-blog.njk",
+    localPath: "_includes/components/widgets/recent-posts-blog.njk",
+    mirrorPath: "theme/_includes/components/widgets/recent-posts-blog.njk",
+  },
+];
+
+function printHelp() {
+  console.log(`Usage: node scripts/check-upstream-widget-drift.mjs [options]\n\nOptions:\n  --ref=<git-ref>   Upstream branch/tag/sha to compare against (default: ${DEFAULT_REF})\n  --show-diff       Print unified diff when drift is found\n  --strict          Exit with code 1 when drift is found\n  -h, --help        Show this help\n\nExamples:\n  npm run check:upstream-widgets\n  npm run check:upstream-widgets -- --show-diff\n  npm run check:upstream-widgets -- --ref=main --strict`);
+}
+
+function normalize(content) {
+  return content.replace(/\r\n/g, "\n");
+}
+
+function parseOptions(argv) {
+  const args = new Set(argv);
+  const refArg = argv.find((arg) => arg.startsWith("--ref="));
+
+  return {
+    ref: refArg ? refArg.slice("--ref=".length) : DEFAULT_REF,
+    showDiff: args.has("--show-diff"),
+    strict: args.has("--strict"),
+    help: args.has("-h") || args.has("--help"),
+  };
+}
+
+async function fetchUpstreamFile(ref, filePath) {
+  const url = `https://raw.githubusercontent.com/${UPSTREAM_REPO}/${encodeURIComponent(ref)}/${filePath}`;
+  const response = await fetch(url, {
+    headers: {
+      "User-Agent": "upstream-widget-drift-check",
+    },
+  });
+
+  if (!response.ok) {
+    throw new Error(`HTTP ${response.status} ${response.statusText} (${url})`);
+  }
+
+  return normalize(await response.text());
+}
+
+function printNoIndexDiff(leftFile, rightFile, leftLabel, rightLabel) {
+  const diffResult = spawnSync(
+    "git",
+    ["--no-pager", "diff", "--no-index", "--src-prefix=a/", "--dst-prefix=b/", "--", leftFile, rightFile],
+    { encoding: "utf8" },
+  );
+
+  let output = diffResult.stdout || "";
+  output = output.split(leftFile).join(leftLabel).split(rightFile).join(rightLabel);
+  if (output.trim()) {
+    process.stdout.write(output);
+  }
+
+  if (diffResult.status !== 0 && diffResult.status !== 1 && diffResult.stderr) {
+    process.stderr.write(diffResult.stderr);
+  }
+}
+
+async function main() {
+  const options = parseOptions(process.argv.slice(2));
+
+  if (options.help) {
+    printHelp();
+    return;
+  }
+
+  const tempDir = mkdtempSync(path.join(tmpdir(), "widget-drift-"));
+  const cwd = process.cwd();
+
+  let upstreamDriftCount = 0;
+  let mirrorDriftCount = 0;
+  let errorCount = 0;
+
+  console.log(`Comparing local widget files against ${UPSTREAM_REPO}@${options.ref}`);
+
+  try {
+    for (const target of targets) {
+      const localAbs = path.join(cwd, target.localPath);
+      const mirrorAbs = path.join(cwd, target.mirrorPath);
+
+      console.log(`\n[${target.name}]`);
+
+      if (!existsSync(localAbs)) {
+        console.log(`  local:   ERROR (missing ${target.localPath})`);
+        errorCount += 1;
+        continue;
+      }
+
+      if (!existsSync(mirrorAbs)) {
+        console.log(`  mirror:  ERROR (missing ${target.mirrorPath})`);
+        errorCount += 1;
+        continue;
+      }
+
+      const localContent = normalize(readFileSync(localAbs, "utf8"));
+      const mirrorContent = normalize(readFileSync(mirrorAbs, "utf8"));
+
+      let upstreamContent;
+      try {
+        upstreamContent = await fetchUpstreamFile(options.ref, target.upstreamPath);
+      } catch (error) {
+        console.log(`  upstream: ERROR (${error.message})`);
+        errorCount += 1;
+        continue;
+      }
+
+      const matchesUpstream = localContent === upstreamContent;
+      const matchesMirror = localContent === mirrorContent;
+
+      console.log(`  upstream: ${matchesUpstream ? "OK" : "DRIFT"}`);
+      console.log(`  mirror:   ${matchesMirror ? "OK" : "DRIFT"}`);
+
+      if (!matchesUpstream) {
+        upstreamDriftCount += 1;
+      }
+
+      if (!matchesMirror) {
+        mirrorDriftCount += 1;
+      }
+
+      if (options.showDiff && !matchesUpstream) {
+        const localTmp = path.join(tempDir, `${target.name}.local.njk`);
+        const upstreamTmp = path.join(tempDir, `${target.name}.upstream.njk`);
+        writeFileSync(localTmp, localContent, "utf8");
+        writeFileSync(upstreamTmp, upstreamContent, "utf8");
+
+        console.log(`\n  diff local vs upstream (${target.name})`);
+        printNoIndexDiff(localTmp, upstreamTmp, `a/${target.localPath}`, `b/upstream/${target.upstreamPath}`);
+      }
+
+      if (options.showDiff && !matchesMirror) {
+        console.log(`\n  diff local vs mirror (${target.name})`);
+        printNoIndexDiff(localAbs, mirrorAbs, `a/${target.localPath}`, `b/${target.mirrorPath}`);
+      }
+    }
+  } finally {
+    rmSync(tempDir, { recursive: true, force: true });
+  }
+
+  console.log("\nSummary");
+  console.log(`  upstream drift: ${upstreamDriftCount}`);
+  console.log(`  mirror drift:   ${mirrorDriftCount}`);
+  console.log(`  errors:         ${errorCount}`);
+
+  if (errorCount > 0) {
+    process.exit(2);
+  }
+
+  if (options.strict && (upstreamDriftCount > 0 || mirrorDriftCount > 0)) {
+    process.exit(1);
+  }
+}
+
+main().catch((error) => {
+  console.error(error);
+  process.exit(2);
+});