diff --git a/packages/core-ts/.eslintrc.js b/packages/core-ts/.eslintrc.js
new file mode 100644
index 0000000..5e8f71b
--- /dev/null
+++ b/packages/core-ts/.eslintrc.js
@@ -0,0 +1,33 @@
+module.exports = {
+  root: false,
+  parser: "@typescript-eslint/parser",
+  parserOptions: {
+    ecmaVersion: 2020,
+    sourceType: "module",
+  },
+  ignorePatterns: ["dist/", "node_modules/"],
+  rules: {
+    "no-restricted-syntax": [
+      "error",
+      {
+        selector: "CallExpression[callee.name='Number']",
+        message:
+          "Do not use Number() to cast values in core-ts routing interfaces. " +
+          "Casting BigInt to Number silently clips values above Number.MAX_SAFE_INTEGER (2^53-1), " +
+          "causing routing corruption. Keep values as BigInt throughout."
+      },
+      {
+        selector: "UnaryExpression[operator='+']",
+        message:
+          "Do not use unary + in core-ts. " +
+          "This coerces BigInt to Number with silent precision loss."
+      },
+      {
+        selector: "CallExpression[callee.name='parseFloat']",
+        message:
+          "Do not use parseFloat() in core-ts routing interfaces. " +
+          "This may silently lose precision on large integers."
+      }
+    ]
+  }
+};
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