diff --git a/packages/core-eslint/base.js b/packages/core-eslint/base.js
index bab3131..0b4ba59 100644
--- a/packages/core-eslint/base.js
+++ b/packages/core-eslint/base.js
@@ -4,8 +4,14 @@ import tseslint from "typescript-eslint";
 import turboPlugin from "eslint-plugin-turbo";
 import boundaries from "eslint-plugin-boundaries";
 import globals from "globals";
+import conformancePlugin from "./plugin.js";
+import path from "node:path";
+import { fileURLToPath } from "node:url";
 // <gen:realtime-rules-imports>
 
+const __dirname = path.dirname(fileURLToPath(import.meta.url));
+const repoRoot = path.resolve(__dirname, "..", "..");
+
 export default [
   { ignores: ["dist/**", "node_modules/**", ".next/**", ".turbo/**", "storybook-static/**"] },
   js.configs.recommended,
@@ -23,6 +29,23 @@ export default [
       "turbo/no-undeclared-env-vars": "warn",
     },
   },
+  {
+    plugins: { conformance: conformancePlugin },
+    rules: {
+      // Structural conformance rules (milestone iii.a).
+      // `feature-must-have-manifest` is WARN today because only auth has a manifest;
+      // flip to ERROR after blog/media/navigation/marketing-pages migrate.
+      "conformance/feature-must-have-manifest": [
+        "warn",
+        { repoRoot },
+      ],
+      "conformance/usecase-must-have-test-file": "error",
+      "conformance/required-cores-installed": [
+        "error",
+        { repoRoot },
+      ],
+    },
+  },
   {
     rules: {
       // Honour the leading-underscore convention for intentionally-unused params/vars.