diff --git a/config.py b/config.py
index 72cd81a..776b0cc 100644
--- a/config.py
+++ b/config.py
@@ -18,6 +18,8 @@ class ExecConfig(BaseSettings):
     enable_type_checking: bool = True
     max_type_check_attempts: int = 3
     keep_only_relevant_files: bool = False
+    # maximum number of automatic debug/fix attempts per node
+    max_debug_retries_per_node: int = 2
 
 
 class CodeConfig(BaseSettings):
diff --git a/treesearch/node.py b/treesearch/node.py
index 37a38e4..e1bdc4d 100644
--- a/treesearch/node.py
+++ b/treesearch/node.py
@@ -62,6 +62,9 @@ class Node(NodeMixin):
     type_check_passed: bool = field(default=False)
     type_check_results: list[TypeCheckResult] = field(default_factory=list)
 
+    # ---- debug retry limiting ----
+    debug_attempts: int = field(default=0)
+
     @property
     def name(self) -> str:
         short_id = f"{self.id[:4]}...{self.id[-4:]}"
@@ -107,6 +110,8 @@ def __setstate__(self, state):
         """Set state during unpickling"""
         # Ensure all required attributes are present
         self.__dict__.update(state)
+        if "debug_attempts" not in self.__dict__:
+            self.debug_attempts = 0
 
     def absorb_exec_result(self, exec_result: ExecutionResult):
         """Absorb the result of executing the code from this node."""
diff --git a/treesearch/search.py b/treesearch/search.py
index 69b9bc8..012445f 100644
--- a/treesearch/search.py
+++ b/treesearch/search.py
@@ -69,26 +69,42 @@ def best_buggy_node(self):
         return buggy_nodes[0]
 
     def select_next_node(self) -> Node:
-        if (
-            len(self.buggy_nodes) > 0
-            and random.random() < self._config.treesearch.debug_prob
-            or len(self.good_nodes) == 0
-        ):
+        # Exclude nodes that exhausted their debug attempts
+        limit = self._config.exec.max_debug_retries_per_node
+        eligible = [n for n in self.all_nodes if n.debug_attempts < limit]
+
+        if not eligible:
+            logger.info("No eligible nodes available after applying debug-attempts filter.")
+            # fallback: return best good node if available, else best buggy node
+            if len(self.good_nodes) > 0:
+                return self.best_good_node
+            return self.best_buggy_node
+
+        buggy = [n for n in eligible if n.is_buggy]
+        good = [n for n in eligible if not n.is_buggy]
+
+        # Prefer debugging buggy nodes with probability debug_prob or when no good nodes exist
+        if (len(buggy) > 0 and random.random() < self._config.treesearch.debug_prob) or len(good) == 0:
             if random.random() < self._config.treesearch.epsilon:
                 logger.info("Selecting random buggy node for debugging...")
-                nodes = self.buggy_nodes
-                weights = [1 / (len(n.children) + 1) for n in nodes]
-                return random.choices(nodes, weights=weights, k=1)[0]
+                weights = [1 / (len(n.children) + 1) for n in buggy]
+                return random.choices(buggy, weights=weights, k=1)[0]
             else:
                 logger.info("Selecting best buggy node for debugging...")
-                return max(self.buggy_nodes, key=lambda n: n.score.score * (1 / (len(n.children) + 1)))
+                return max(buggy, key=lambda n: n.score.score * (1 / (len(n.children) + 1)))
+
+        # Otherwise select a good node to improve
+        if len(good) == 0:
+            # no good nodes available; fallback
+            if len(self.good_nodes) > 0:
+                return self.best_good_node
+            return self.best_buggy_node
 
         if random.random() < self._config.treesearch.epsilon:
-            nodes = self.good_nodes
-            weights = [1 / (len(n.children) + 1) for n in nodes]
-            return random.choices(nodes, weights=weights, k=1)[0]
+            weights = [1 / (len(n.children) + 1) for n in good]
+            return random.choices(good, weights=weights, k=1)[0]
         else:
-            return max(self.good_nodes, key=lambda n: n.score.score * (1 / (len(n.children) + 1)))
+            return max(good, key=lambda n: n.score.score * (1 / (len(n.children) + 1)))
 
     async def run(self):
         logger.info("Starting tree search...")
@@ -106,11 +122,32 @@ async def run(self):
             logger.info(
                 f"Treesearch iteration {i + 1}/{self._config.treesearch.max_iterations}"
             )
+
             parent_node = self.select_next_node()
 
-            if parent_node.is_buggy:
+            if parent_node is None:
+                logger.info("select_next_node returned None — ending search early.")
+                break
+
+            # Check if we can still debug this node or if we've hit the retry limit
+            max_debug_retries = self._config.exec.max_debug_retries_per_node
+            can_debug = (
+                parent_node.is_buggy 
+                and parent_node.debug_attempts < max_debug_retries
+            )
+
+            if can_debug:
+                logger.info(
+                    f"Debugging node {parent_node.id[:8]}... "
+                    f"(attempt {parent_node.debug_attempts + 1}/{max_debug_retries})"
+                )
                 child_node = await self._minimal_agent._debug(parent_node)
+                parent_node.debug_attempts += 1
             else:
+                if parent_node.is_buggy and parent_node.debug_attempts >= max_debug_retries:
+                    logger.info(
+                        f"Node {parent_node.id[:8]} has reached max debug retries"
+                    )
                 child_node = await self._minimal_agent._improve(parent_node)
 
             await self.exec_node(child_node)