diff --git a/comfy_execution/caching.py b/comfy_execution/caching.py
index 78212bde3..cbf2e9de1 100644
--- a/comfy_execution/caching.py
+++ b/comfy_execution/caching.py
@@ -1,7 +1,6 @@
 import asyncio
 import bisect
 import gc
-import itertools
 import psutil
 import time
 import torch
@@ -17,6 +16,7 @@ NODE_CLASS_CONTAINS_UNIQUE_ID: Dict[str, bool] = {}
 
 
 def include_unique_id_in_input(class_type: str) -> bool:
+    """Return whether a node class includes UNIQUE_ID among its hidden inputs."""
     if class_type in NODE_CLASS_CONTAINS_UNIQUE_ID:
         return NODE_CLASS_CONTAINS_UNIQUE_ID[class_type]
     class_def = nodes.NODE_CLASS_MAPPINGS[class_type]
@@ -24,52 +24,181 @@ def include_unique_id_in_input(class_type: str) -> bool:
     return NODE_CLASS_CONTAINS_UNIQUE_ID[class_type]
 
 class CacheKeySet(ABC):
+    """Base helper for building and storing cache keys for prompt nodes."""
     def __init__(self, dynprompt, node_ids, is_changed_cache):
+        """Initialize cache-key storage for a dynamic prompt execution pass."""
         self.keys = {}
         self.subcache_keys = {}
 
     @abstractmethod
     async def add_keys(self, node_ids):
+        """Populate cache keys for the provided node ids."""
         raise NotImplementedError()
 
     def all_node_ids(self):
+        """Return the set of node ids currently tracked by this key set."""
         return set(self.keys.keys())
 
     def get_used_keys(self):
+        """Return the computed cache keys currently in use."""
         return self.keys.values()
 
     def get_used_subcache_keys(self):
+        """Return the computed subcache keys currently in use."""
         return self.subcache_keys.values()
 
     def get_data_key(self, node_id):
+        """Return the cache key for a node, if present."""
         return self.keys.get(node_id, None)
 
     def get_subcache_key(self, node_id):
+        """Return the subcache key for a node, if present."""
         return self.subcache_keys.get(node_id, None)
 
 class Unhashable:
-    def __init__(self):
-        self.value = float("NaN")
+    """Hashable identity sentinel for values that cannot be represented safely in cache keys."""
+    pass
 
-def to_hashable(obj):
-    # So that we don't infinitely recurse since frozenset and tuples
-    # are Sequences.
-    if isinstance(obj, (int, float, str, bool, bytes, type(None))):
-        return obj
-    elif isinstance(obj, Mapping):
-        return frozenset([(to_hashable(k), to_hashable(v)) for k, v in sorted(obj.items())])
-    elif isinstance(obj, Sequence):
-        return frozenset(zip(itertools.count(), [to_hashable(i) for i in obj]))
+
+def _sanitized_sort_key(obj, depth=0, max_depth=32):
+    """Return a deterministic ordering key for sanitized built-in container content."""
+    if depth >= max_depth:
+        return ("MAX_DEPTH",)
+
+    obj_type = type(obj)
+    if obj_type is Unhashable:
+        return ("UNHASHABLE",)
+    elif obj_type in (int, float, str, bool, bytes, type(None)):
+        return (obj_type.__module__, obj_type.__qualname__, repr(obj))
+    elif obj_type is dict:
+        items = [
+            (
+                _sanitized_sort_key(k, depth + 1, max_depth),
+                _sanitized_sort_key(v, depth + 1, max_depth),
+            )
+            for k, v in obj.items()
+        ]
+        items.sort()
+        return ("dict", tuple(items))
+    elif obj_type is list:
+        return ("list", tuple(_sanitized_sort_key(i, depth + 1, max_depth) for i in obj))
+    elif obj_type is tuple:
+        return ("tuple", tuple(_sanitized_sort_key(i, depth + 1, max_depth) for i in obj))
+    elif obj_type is set:
+        return ("set", tuple(sorted(_sanitized_sort_key(i, depth + 1, max_depth) for i in obj)))
+    elif obj_type is frozenset:
+        return ("frozenset", tuple(sorted(_sanitized_sort_key(i, depth + 1, max_depth) for i in obj)))
+    else:
+        return (obj_type.__module__, obj_type.__qualname__, "OPAQUE")
+
+
+def _sanitize_signature_input(obj, depth=0, max_depth=32, seen=None):
+    """Normalize signature inputs to safe built-in containers.
+
+    Preserves built-in container type, replaces opaque runtime values with
+    Unhashable(), and stops safely on cycles or excessive depth.
+    """
+    if depth >= max_depth:
+        return Unhashable()
+
+    if seen is None:
+        seen = set()
+
+    obj_type = type(obj)
+    if obj_type in (dict, list, tuple, set, frozenset):
+        obj_id = id(obj)
+        if obj_id in seen:
+            return Unhashable()
+        next_seen = seen | {obj_id}
+
+    if obj_type in (int, float, str, bool, bytes, type(None)):
+        return obj
+    elif obj_type is dict:
+        sanitized_items = [
+            (
+                _sanitize_signature_input(key, depth + 1, max_depth, next_seen),
+                _sanitize_signature_input(value, depth + 1, max_depth, next_seen),
+            )
+            for key, value in obj.items()
+        ]
+        sanitized_items.sort(
+            key=lambda kv: (
+                _sanitized_sort_key(kv[0], depth + 1, max_depth),
+                _sanitized_sort_key(kv[1], depth + 1, max_depth),
+            )
+        )
+        return {key: value for key, value in sanitized_items}
+    elif obj_type is list:
+        return [_sanitize_signature_input(item, depth + 1, max_depth, next_seen) for item in obj]
+    elif obj_type is tuple:
+        return tuple(_sanitize_signature_input(item, depth + 1, max_depth, next_seen) for item in obj)
+    elif obj_type is set:
+        return {_sanitize_signature_input(item, depth + 1, max_depth, next_seen) for item in obj}
+    elif obj_type is frozenset:
+        return frozenset(_sanitize_signature_input(item, depth + 1, max_depth, next_seen) for item in obj)
+    else:
+        # Execution-cache signatures should be built from prompt-safe values.
+        # If a custom node injects a runtime object here, mark it unhashable so
+        # the node won't reuse stale cache entries across runs, but do not walk
+        # the foreign object and risk crashing on custom container semantics.
+        return Unhashable()
+
+def to_hashable(obj, depth=0, max_depth=32, seen=None):
+    """Convert sanitized prompt inputs into a stable hashable representation.
+
+    Preserves built-in container type and stops safely on cycles or excessive depth.
+    """
+    if depth >= max_depth:
+        return Unhashable()
+
+    if seen is None:
+        seen = set()
+
+    # Restrict recursion to plain built-in containers. Some custom nodes insert
+    # runtime objects into prompt inputs for dynamic graph paths; walking those
+    # objects as generic Mappings / Sequences is unsafe and can destabilize the
+    # cache signature builder.
+    obj_type = type(obj)
+    if obj_type in (int, float, str, bool, bytes, type(None)):
+        return obj
+
+    if obj_type in (dict, list, tuple, set, frozenset):
+        obj_id = id(obj)
+        if obj_id in seen:
+            return Unhashable()
+        seen = seen | {obj_id}
+
+    if obj_type is dict:
+        return (
+            "dict",
+            frozenset(
+                (
+                    to_hashable(k, depth + 1, max_depth, seen),
+                    to_hashable(v, depth + 1, max_depth, seen),
+                )
+                for k, v in obj.items()
+            ),
+        )
+    elif obj_type is list:
+        return ("list", tuple(to_hashable(i, depth + 1, max_depth, seen) for i in obj))
+    elif obj_type is tuple:
+        return ("tuple", tuple(to_hashable(i, depth + 1, max_depth, seen) for i in obj))
+    elif obj_type is set:
+        return ("set", frozenset(to_hashable(i, depth + 1, max_depth, seen) for i in obj))
+    elif obj_type is frozenset:
+        return ("frozenset", frozenset(to_hashable(i, depth + 1, max_depth, seen) for i in obj))
     else:
-        # TODO - Support other objects like tensors?
         return Unhashable()
 
 class CacheKeySetID(CacheKeySet):
+    """Cache-key strategy that keys nodes by node id and class type."""
     def __init__(self, dynprompt, node_ids, is_changed_cache):
+        """Initialize identity-based cache keys for the supplied dynamic prompt."""
         super().__init__(dynprompt, node_ids, is_changed_cache)
         self.dynprompt = dynprompt
 
     async def add_keys(self, node_ids):
+        """Populate identity-based keys for nodes that exist in the dynamic prompt."""
         for node_id in node_ids:
             if node_id in self.keys:
                 continue
@@ -80,15 +209,19 @@ class CacheKeySetID(CacheKeySet):
             self.subcache_keys[node_id] = (node_id, node["class_type"])
 
 class CacheKeySetInputSignature(CacheKeySet):
+    """Cache-key strategy that hashes a node's immediate inputs plus ancestor references."""
     def __init__(self, dynprompt, node_ids, is_changed_cache):
+        """Initialize input-signature-based cache keys for the supplied dynamic prompt."""
         super().__init__(dynprompt, node_ids, is_changed_cache)
         self.dynprompt = dynprompt
         self.is_changed_cache = is_changed_cache
 
     def include_node_id_in_input(self) -> bool:
+        """Return whether node ids should be included in computed input signatures."""
         return False
 
     async def add_keys(self, node_ids):
+        """Populate input-signature-based keys for nodes in the dynamic prompt."""
         for node_id in node_ids:
             if node_id in self.keys:
                 continue
@@ -99,6 +232,7 @@ class CacheKeySetInputSignature(CacheKeySet):
             self.subcache_keys[node_id] = (node_id, node["class_type"])
 
     async def get_node_signature(self, dynprompt, node_id):
+        """Build the full cache signature for a node and its ordered ancestors."""
         signature = []
         ancestors, order_mapping = self.get_ordered_ancestry(dynprompt, node_id)
         signature.append(await self.get_immediate_node_signature(dynprompt, node_id, order_mapping))
@@ -107,6 +241,10 @@ class CacheKeySetInputSignature(CacheKeySet):
         return to_hashable(signature)
 
     async def get_immediate_node_signature(self, dynprompt, node_id, ancestor_order_mapping):
+        """Build the cache-signature fragment for a node's immediate inputs.
+
+        Link inputs are reduced to ancestor references, while raw values are sanitized first.
+        """
         if not dynprompt.has_node(node_id):
             # This node doesn't exist -- we can't cache it.
             return [float("NaN")]
@@ -123,18 +261,20 @@ class CacheKeySetInputSignature(CacheKeySet):
                 ancestor_index = ancestor_order_mapping[ancestor_id]
                 signature.append((key,("ANCESTOR", ancestor_index, ancestor_socket)))
             else:
-                signature.append((key, inputs[key]))
+                signature.append((key, _sanitize_signature_input(inputs[key])))
         return signature
 
     # This function returns a list of all ancestors of the given node. The order of the list is
     # deterministic based on which specific inputs the ancestor is connected by.
     def get_ordered_ancestry(self, dynprompt, node_id):
+        """Return ancestors in deterministic traversal order and their index mapping."""
         ancestors = []
         order_mapping = {}
         self.get_ordered_ancestry_internal(dynprompt, node_id, ancestors, order_mapping)
         return ancestors, order_mapping
 
     def get_ordered_ancestry_internal(self, dynprompt, node_id, ancestors, order_mapping):
+        """Recursively collect ancestors in input order without revisiting prior nodes."""
         if not dynprompt.has_node(node_id):
             return
         inputs = dynprompt.get_node(node_id)["inputs"]
diff --git a/comfy_execution/graph_utils.py b/comfy_execution/graph_utils.py
index 496d2c634..57b4ef36e 100644
--- a/comfy_execution/graph_utils.py
+++ b/comfy_execution/graph_utils.py
@@ -1,11 +1,17 @@
 def is_link(obj):
-    if not isinstance(obj, list):
+    """Return whether obj is a plain prompt link of the form [node_id, output_index]."""
+    # Prompt links produced by the frontend / GraphBuilder are plain Python
+    # lists in the form [node_id, output_index]. Some custom-node paths can
+    # inject foreign runtime objects into prompt inputs during on-prompt graph
+    # rewriting or subgraph construction. Be strict here so cache signature
+    # building never tries to treat list-like proxy objects as links.
+    if type(obj) is not list:
         return False
     if len(obj) != 2:
         return False
-    if not isinstance(obj[0], str):
+    if type(obj[0]) is not str:
         return False
-    if not isinstance(obj[1], int) and not isinstance(obj[1], float):
+    if type(obj[1]) is not int:
         return False
     return True