diff --git a/codex/recursion_engine.py b/codex/recursion_engine.py
index ad35e5a..5b57597 100644
--- a/codex/recursion_engine.py
+++ b/codex/recursion_engine.py
@@ -1 +1,35 @@
-print("Hello World")
+from __future__ import annotations
+
+from dataclasses import dataclass
+from typing import Callable, Any
+
+
+@dataclass
+class RecursionLimits:
+    max_depth: int = 5
+    max_nodes: int = 10_000
+
+
+class RecursionEngine:
+    """Safe, bounded recursion helper."""
+    def __init__(self, limits: RecursionLimits | None = None) -> None:
+        self.limits = limits or RecursionLimits()
+        self._nodes = 0
+
+    def recursive(self, fn: Callable[[Any], Any], x: Any, depth: int = 0) -> Any:
+        if depth > self.limits.max_depth:
+            raise RecursionError("max_depth exceeded")
+        if self._nodes >= self.limits.max_nodes:
+            raise RecursionError("max_nodes exceeded")
+
+        self._nodes += 1
+        y = fn(x)
+        # placeholder: stop when fn returns x unchanged
+        if y == x:
+            return y
+        return self.recursive(fn, y, depth + 1)
+
+
+if __name__ == "__main__":
+    eng = RecursionEngine(RecursionLimits(max_depth=3))
+    print(eng.recursive(lambda n: n - 1 if n > 0 else n, 3))