diff --git a/.github/workflows/build-docs.yml b/.github/workflows/build-docs.yml
index 6cf0ff8cc..29c168ea8 100644
--- a/.github/workflows/build-docs.yml
+++ b/.github/workflows/build-docs.yml
@@ -41,3 +41,6 @@ jobs:
 
       - name: Build docs
         run: npm run docs:build
+
+      - name: Check the build output and the docs for citation markers
+        run: npm run check:citation-markers
diff --git a/dev-docs/BUILD.md b/dev-docs/BUILD.md
index c1273b71a..130fce144 100644
--- a/dev-docs/BUILD.md
+++ b/dev-docs/BUILD.md
@@ -26,6 +26,8 @@ The generator lives in `docs/script/` rather than beside the engine build script
 
 Both are git-ignored, and both are regenerated as the first step of `docs:dev` and `docs:build`. `docs:generate-function-docs` is a gate, not a formatter: it fails the build on a missing catalogue entry or a `'Custom'` category. See [`FUNCTION-CATALOGUE.md`](../hyperformula/dev-docs/FUNCTION-CATALOGUE.md).
 
+After `docs:build`, the `build-docs` workflow runs `npm run check:citation-markers`. It fails when a citation marker from a draft document (the patterns are listed in the script) appears in the engine's build output or in `docs/api/` and `docs/guide/`, and when one of those directories is missing or empty.
+
 ## Deploying the portal
 
 The portal is served by a Cloudflare Worker, and **deployment is driven by Workers Builds on push, not from a developer's machine**: `master` deploys to production, every other branch uploads a preview version. The commands below exist for debugging that pipeline. The triggers, the Worker name, and the dashboard build settings are in [`docs/README.md`](../docs/README.md#deployment).
diff --git a/dev-docs/STRUCTURE.md b/dev-docs/STRUCTURE.md
index 32e886004..1393625c0 100644
--- a/dev-docs/STRUCTURE.md
+++ b/dev-docs/STRUCTURE.md
@@ -114,7 +114,7 @@ Each script lives with whatever invokes it, and every one has exactly one caller
 
 | Directory | Holds |
 |---|---|
-| `script/` | `release/` and `check-licenses.mjs` — both span the whole repository |
+| `script/` | `release/`, `check-licenses.mjs` and `check-citation-markers.mjs` — all three span the whole repository |
 | `hyperformula/script/` | `check-file.js`, `check-publish-package.js`, `if-ne-env.js` — called by the engine's build; `check-license-key-parser-drift.js` — called by `vendored-parser.yml`; `postinstall-skills-message.js` — shipped in the package and run by npm when a user installs it, silent inside this repository |
 | `docs/script/` | the built-in-functions generator and `prepare-cf-assets.js` — called by the portal |
 | `hyperformula-ui/scripts/` | `generateCssText.mjs` and `generateApiDocs.mjs` — called by the UI core's `build:styles` and `docs` |
diff --git a/package.json b/package.json
index c9dca6825..ff3da5566 100644
--- a/package.json
+++ b/package.json
@@ -57,6 +57,7 @@
     "docs:preview:cf": "npm --prefix docs run preview:cf --",
     "audit": "npm audit --omit=dev",
     "check:licenses": "node script/check-licenses.mjs",
+    "check:citation-markers": "node script/check-citation-markers.mjs",
     "release": "bash script/release/release.sh"
   },
   "devDependencies": {
diff --git a/script/AGENTS.md b/script/AGENTS.md
index 82645d663..1b048ee26 100644
--- a/script/AGENTS.md
+++ b/script/AGENTS.md
@@ -6,8 +6,9 @@ Repository-level scripts. Each package keeps its own in `hyperformula/script/` a
 |---|---|---|
 | `check-licenses.mjs` | `npm run check:licenses` | Asserts every production dependency is permissively licensed |
 | `release/` | `npm run release` | The release procedure, across the packages and the sibling repositories |
+| `check-citation-markers.mjs` | `npm run check:citation-markers`, which `build-docs.yml` runs after `docs:build` | Fails when a citation marker from a draft document appears in the engine's build output or the docs |
 
 - What the build produces, and where the licence gate fits: [`dev-docs/BUILD.md`](../dev-docs/BUILD.md)
 - Everything else: [`dev-docs/README.md`](../dev-docs/README.md)
 
-No workflow runs these; they are run by hand from the repository root. `release/release.sh` needs an operator at a terminal on purpose — after `--real-run`, its typed confirmation is the last guard before `npm publish` — so never make it run without one. Nothing here is covered by tests; a change is verified by running it.
+Only `check-citation-markers.mjs` runs in CI; the others are run by hand from the repository root. `release/release.sh` needs an operator at a terminal on purpose — after `--real-run`, its typed confirmation is the last guard before `npm publish` — so never make it run without one. Nothing here is covered by tests; a change is verified by running it.
diff --git a/script/check-citation-markers.mjs b/script/check-citation-markers.mjs
new file mode 100644
index 000000000..bbcf16462
--- /dev/null
+++ b/script/check-citation-markers.mjs
@@ -0,0 +1,109 @@
+#!/usr/bin/env node
+/**
+ * Fails when a citation marker from a draft document appears in the engine's
+ * build output or in the documentation.
+ *
+ * The markers are `[V<n>]`, `[<prefix>_<n>]` with the prefix `vrf`, `dec`,
+ * `con`, `que`, `wrg` or `crf`, and the footer heading `§AuditSources`. A source
+ * comment survives into `commonjs/`, `es/`, the development bundle in `dist/`
+ * and the `sourcesContent` of the source maps in `dist/`, so every file of the
+ * output is scanned, not only the minified bundles.
+ *
+ * Run it after `npm run docs:build`, which builds both the engine and the docs.
+ * A path that is missing or holds no files fails the check instead of being
+ * skipped, so a moved output directory cannot turn it into a scan of nothing.
+ */
+import { readdirSync, readFileSync, statSync } from 'node:fs'
+import path from 'node:path'
+import { fileURLToPath } from 'node:url'
+
+const REPO_ROOT = path.resolve(path.dirname(fileURLToPath(import.meta.url)), '..')
+
+/** The engine's build output and the documentation, relative to the repository root. */
+const SCANNED = [
+  'hyperformula/commonjs',
+  'hyperformula/dist',
+  'hyperformula/es',
+  'hyperformula/languages',
+  'hyperformula/typings',
+  'docs/api',
+  'docs/guide',
+]
+
+const MARKER = /\[(?:V\d+|(?:vrf|dec|con|que|wrg|crf)_\d+)\]|§\s*AuditSources/g
+
+/** Checked before every scan, so a broken pattern fails instead of finding nothing. */
+const MUST_MATCH = ['[V3]', '[vrf_1]', '[dec_2]', '[con_3]', '[que_4]', '[wrg_5]', '[crf_6]', '§AuditSources', '§ AuditSources']
+const MUST_NOT_MATCH = ['[V]', '[v1]', '[vrf_]', '[vrf_1a]', '[abc_1]', 'AuditSources', 'cells[V1']
+
+/**
+ * Prints an error and exits with code 2, which means the scan could not run.
+ *
+ * @param {string} message What went wrong.
+ */
+function abort(message) {
+  console.error(`ERROR: ${message}`)
+  process.exit(2)
+}
+
+/**
+ * Lists every file under a directory.
+ *
+ * @param {string} dir Absolute path of the directory.
+ * @returns {string[]} Absolute paths of the files.
+ */
+function listFiles(dir) {
+  return readdirSync(dir, { withFileTypes: true }).flatMap((entry) => {
+    const full = path.join(dir, entry.name)
+    if (entry.isDirectory()) {
+      return listFiles(full)
+    }
+    return entry.isFile() ? [full] : []
+  })
+}
+
+for (const sample of MUST_MATCH) {
+  if (!sample.match(MARKER)) {
+    abort(`the marker pattern does not match ${sample}`)
+  }
+}
+for (const sample of MUST_NOT_MATCH) {
+  if (sample.match(MARKER)) {
+    abort(`the marker pattern matches ${sample}, which is not a marker`)
+  }
+}
+
+const hits = []
+let fileCount = 0
+for (const relative of SCANNED) {
+  const dir = path.join(REPO_ROOT, relative)
+  let isDirectory = false
+  try {
+    isDirectory = statSync(dir).isDirectory()
+  } catch {
+    abort(`${relative} does not exist. Build the engine and the docs first: npm run docs:build`)
+  }
+  if (!isDirectory) {
+    abort(`${relative} is not a directory`)
+  }
+  const files = listFiles(dir)
+  if (files.length === 0) {
+    abort(`${relative} contains no files`)
+  }
+  console.log(`${relative}: ${files.length} files`)
+  fileCount += files.length
+  for (const file of files) {
+    const text = readFileSync(file, 'utf8')
+    for (const match of text.matchAll(MARKER)) {
+      const line = text.slice(0, match.index).split('\n').length
+      hits.push(`${path.relative(REPO_ROOT, file)}:${line}: ${match[0]}`)
+    }
+  }
+}
+
+if (hits.length > 0) {
+  console.error(hits.join('\n'))
+  console.error(`\nERROR: ${hits.length} citation markers found. Remove them from the source comments or strings they come from.`)
+  process.exit(1)
+}
+console.log(`No citation markers in ${fileCount} files.`)