diff --git a/package.json b/package.json
index d86db42..8779af5 100644
--- a/package.json
+++ b/package.json
@@ -12,6 +12,7 @@
     "format:check": "prettier \"**/*.{ts,tsx,js,jsx,mjs,cjs,json,css,yml,yaml}\" --check",
     "check": "pnpm lint && pnpm typecheck && pnpm format:check",
     "typecheck": "tsc --noEmit",
+    "guard:no-mock": "node scripts/guard-no-mock.mjs",
     "test": "vitest run",
     "test:watch": "vitest"
   },
diff --git a/scripts/guard-no-mock.mjs b/scripts/guard-no-mock.mjs
new file mode 100644
index 0000000..2df0af7
--- /dev/null
+++ b/scripts/guard-no-mock.mjs
@@ -0,0 +1,156 @@
+import fs from "node:fs/promises"
+import path from "node:path"
+import process from "node:process"
+import { fileURLToPath } from "node:url"
+
+const REPO_ROOT = path.resolve(path.dirname(fileURLToPath(import.meta.url)), "..")
+
+const SOURCE_EXTS = new Set([".ts", ".tsx", ".js", ".jsx", ".mjs", ".cjs"])
+const IGNORE_DIRS = new Set(["node_modules", ".git", ".next", "dist", "build", "coverage"])
+
+function rel(p) {
+  return path.relative(REPO_ROOT, p)
+}
+
+async function statSafe(p) {
+  try {
+    return await fs.stat(p)
+  } catch {
+    return null
+  }
+}
+
+async function listFilesRecursive(dir, { exts = null } = {}) {
+  const out = []
+  const st = await statSafe(dir)
+  if (!st || !st.isDirectory()) return out
+
+  const entries = await fs.readdir(dir, { withFileTypes: true })
+  for (const ent of entries) {
+    if (ent.isDirectory()) {
+      if (IGNORE_DIRS.has(ent.name)) continue
+      out.push(...(await listFilesRecursive(path.join(dir, ent.name), { exts })))
+      continue
+    }
+    if (!ent.isFile()) continue
+    const fullPath = path.join(dir, ent.name)
+    if (exts && !exts.has(path.extname(ent.name))) continue
+    out.push(fullPath)
+  }
+  return out
+}
+
+async function findFilesContainingString(roots, needle) {
+  const matches = []
+  for (const root of roots) {
+    const absRoot = path.join(REPO_ROOT, root)
+    const files = await listFilesRecursive(absRoot, { exts: SOURCE_EXTS })
+    for (const file of files) {
+      const content = await fs.readFile(file, "utf8")
+      if (content.includes(needle)) matches.push(file)
+    }
+  }
+  return matches
+}
+
+async function findFilesMatchingPredicate(roots, predicate) {
+  const matches = []
+  for (const root of roots) {
+    const absRoot = path.join(REPO_ROOT, root)
+    const files = await listFilesRecursive(absRoot, { exts: SOURCE_EXTS })
+    for (const file of files) {
+      const content = await fs.readFile(file, "utf8")
+      if (predicate(content)) matches.push(file)
+    }
+  }
+  return matches
+}
+
+async function findAppApiRoutes() {
+  const apiRoot = path.join(REPO_ROOT, "app", "api")
+  const st = await statSafe(apiRoot)
+  if (!st || !st.isDirectory()) return []
+
+  const files = await listFilesRecursive(apiRoot, { exts: new Set([".ts"]) })
+  return files.filter((p) => path.basename(p) === "route.ts")
+}
+
+async function main() {
+  const violations = []
+
+  const mockImports = await findFilesContainingString(
+    ["app", "components", "lib", "store", "tests"],
+    "@/lib/mock",
+  )
+  if (mockImports.length > 0) {
+    violations.push({
+      title: "Found @/lib/mock import string in source files",
+      files: mockImports,
+    })
+  }
+
+  const libMockDir = path.join(REPO_ROOT, "lib", "mock")
+  const libMockSt = await statSafe(libMockDir)
+  if (libMockSt?.isDirectory()) {
+    violations.push({
+      title: "Found lib/mock directory",
+      files: [libMockDir],
+    })
+  }
+
+  const apiRoutes = await findAppApiRoutes()
+  if (apiRoutes.length > 0) {
+    violations.push({
+      title: "Found app/api/**/route.ts files",
+      files: apiRoutes,
+    })
+  }
+
+  const absoluteBackendMatches = await findFilesMatchingPredicate(
+    ["app", "components"],
+    (content) =>
+      content.includes("NEXT_PUBLIC_BACKEND_URL") || /https?:\/\/localhost:8080/.test(content),
+  )
+  if (absoluteBackendMatches.length > 0) {
+    violations.push({
+      title:
+        "Found absolute backend origins or NEXT_PUBLIC_BACKEND_URL usage in client code (app/ or components/)",
+      files: absoluteBackendMatches,
+    })
+  }
+
+  const apiDir = path.join(REPO_ROOT, "lib", "api")
+  const apiFiles = (await listFilesRecursive(apiDir, { exts: new Set([".ts"]) })).filter(
+    (p) => p !== path.join(apiDir, "client.ts"),
+  )
+  const storeImportRe = /^\s*(?:import|export)\s+(?:type\s+)?(?:[\w*\s{},]*from\s*)?['"]@\/store\//m
+  const apiStoreImports = []
+  for (const file of apiFiles) {
+    const content = await fs.readFile(file, "utf8")
+    if (storeImportRe.test(content)) apiStoreImports.push(file)
+  }
+  if (apiStoreImports.length > 0) {
+    violations.push({
+      title: "Found @/store/ imports in lib/api (except lib/api/client.ts)",
+      files: apiStoreImports,
+    })
+  }
+
+  if (violations.length > 0) {
+    console.error("guard:no-mock failed")
+    for (const v of violations) {
+      console.error(`\n- ${v.title}`)
+      for (const f of v.files) console.error(`  - ${rel(f)}`)
+    }
+    process.exitCode = 1
+    return
+  }
+
+  console.log("guard:no-mock ok")
+}
+
+main().catch((err) => {
+  console.error("guard:no-mock crashed")
+  console.error(err)
+  process.exit(1)
+})