diff --git a/docs/reference/REMOVED_PROVIDERS.md b/docs/reference/REMOVED_PROVIDERS.md
index e03283bd430..24c0aab7d43 100644
--- a/docs/reference/REMOVED_PROVIDERS.md
+++ b/docs/reference/REMOVED_PROVIDERS.md
@@ -1,3 +1,9 @@
+---
+title: "Removed Providers"
+version: 3.8.51
+lastUpdated: 2026-09-03
+---
+
 # Providers removed at their operator's request
 
 Some services were integrated into OmniRoute and later removed because the people who run
diff --git a/package.json b/package.json
index bbfee22bc78..bc63455358d 100644
--- a/package.json
+++ b/package.json
@@ -151,7 +151,8 @@
     "check:router-eval": "node --import tsx scripts/check/check-router-eval-regression.ts",
     "check:doc-links": "node scripts/check/check-doc-links.mjs",
     "check:fabricated-docs": "node scripts/check/check-fabricated-docs.mjs --strict",
-    "check:docs-all": "npm run check:docs-sync && npm run check:docs-counts && npm run check:env-doc-sync && npm run check:deprecated-versions && npm run check:doc-links && npm run check:fabricated-docs",
+    "check:docs-frontmatter": "node scripts/check/check-docs-frontmatter.mjs",
+    "check:docs-all": "npm run check:docs-sync && npm run check:docs-frontmatter && npm run check:docs-counts && npm run check:env-doc-sync && npm run check:deprecated-versions && npm run check:doc-links && npm run check:fabricated-docs",
     "docs:render-diagrams": "node scripts/docs/render-diagrams.mjs",
     "i18n:run": "node scripts/i18n/run-translation.mjs",
     "i18n:run:dry": "node scripts/i18n/run-translation.mjs --dry-run",
diff --git a/scripts/check/check-docs-frontmatter.mjs b/scripts/check/check-docs-frontmatter.mjs
new file mode 100644
index 00000000000..a00751f8809
--- /dev/null
+++ b/scripts/check/check-docs-frontmatter.mjs
@@ -0,0 +1,103 @@
+#!/usr/bin/env node
+/**
+ * Validates the frontmatter of every Markdown file that fumadocs-mdx compiles.
+ *
+ * Why this gate exists: `source.config.ts` feeds `docs/**` globs to
+ * `defineDocs()`, and fumadocs' default frontmatter schema REQUIRES a `title`
+ * string. A doc added without frontmatter does not fail any docs gate — it
+ * fails the **production build** with a generic Turbopack error
+ * (`[MDX] invalid frontmatter … title: Invalid input: expected string,
+ * received undefined`), which then cascades into `check:pack-artifact` and the
+ * tarball boot-smoke. That is exactly how #12478 turned the release branch red
+ * (base-red #12581): one new reference doc, no frontmatter, three failing
+ * gates and an unbuildable branch.
+ *
+ * Catching it here costs milliseconds instead of a full Next build.
+ *
+ * The globs are read from `source.config.ts` rather than duplicated, so adding
+ * a new docs directory there cannot silently escape this check.
+ */
+
+import fs from "node:fs";
+import path from "node:path";
+import { fileURLToPath } from "node:url";
+
+const ROOT = path.resolve(path.dirname(fileURLToPath(import.meta.url)), "..", "..");
+const CONFIG_PATH = path.join(ROOT, "source.config.ts");
+
+/** Extract the `files: [...]` globs declared in source.config.ts. */
+function readConfiguredGlobs() {
+  const src = fs.readFileSync(CONFIG_PATH, "utf-8");
+  const block = src.match(/files\s*:\s*\[([\s\S]*?)\]/);
+  if (!block) {
+    console.error(
+      "[docs-frontmatter] FAIL — could not locate the `files:` globs in source.config.ts"
+    );
+    process.exit(1);
+  }
+  const globs = [...block[1].matchAll(/["'`]([^"'`]+)["'`]/g)].map((m) => m[1]);
+  if (globs.length === 0) {
+    console.error("[docs-frontmatter] FAIL — source.config.ts declares no doc globs");
+    process.exit(1);
+  }
+  return globs;
+}
+
+/** "./reference/**\/*.md" -> the directory under docs/ it covers. */
+function globToDir(glob) {
+  const cleaned = glob.replace(/^\.\//, "");
+  const dir = cleaned.split("/**")[0];
+  return path.join(ROOT, "docs", dir);
+}
+
+function walkMarkdown(dir) {
+  if (!fs.existsSync(dir)) return [];
+  const out = [];
+  for (const entry of fs.readdirSync(dir, { withFileTypes: true })) {
+    const full = path.join(dir, entry.name);
+    if (entry.isDirectory()) out.push(...walkMarkdown(full));
+    else if (entry.isFile() && entry.name.endsWith(".md")) out.push(full);
+  }
+  return out;
+}
+
+const violations = [];
+const files = [...new Set(readConfiguredGlobs().flatMap((g) => walkMarkdown(globToDir(g))))];
+
+for (const file of files) {
+  const rel = path.relative(ROOT, file);
+  const text = fs.readFileSync(file, "utf-8");
+
+  if (!text.startsWith("---")) {
+    violations.push(`${rel}: no frontmatter block (fumadocs requires a \`title\`)`);
+    continue;
+  }
+  const end = text.indexOf("\n---", 3);
+  if (end === -1) {
+    violations.push(`${rel}: frontmatter block is never closed`);
+    continue;
+  }
+  const frontmatter = text.slice(3, end);
+  const title = frontmatter.match(/^\s*title\s*:\s*(.+)$/m);
+  if (!title) {
+    violations.push(`${rel}: frontmatter has no \`title\``);
+  } else if (title[1].trim().replace(/^["']|["']$/g, "") === "") {
+    violations.push(`${rel}: \`title\` is empty`);
+  }
+}
+
+if (violations.length > 0) {
+  console.error(
+    `[docs-frontmatter] FAIL — ${violations.length} doc(s) would break the Next build:`
+  );
+  for (const v of violations) console.error(`  - ${v}`);
+  console.error(
+    "\nEvery Markdown file matched by source.config.ts is compiled by fumadocs-mdx and needs a\n" +
+      'frontmatter block with a title, e.g.:\n\n---\ntitle: "Removed Providers"\nversion: 3.8.51\nlastUpdated: 2026-09-03\n---\n'
+  );
+  process.exit(1);
+}
+
+console.log(
+  `[docs-frontmatter] OK — ${files.length} compiled doc(s) carry a valid frontmatter title.`
+);