From 6e312af8c25ccedd1dcd2583358be038ab4875b0 Mon Sep 17 00:00:00 2001
From: Shuwen Wang <47200617+alphabetc1@users.noreply.github.com>
Date: Mon, 7 Sep 2026 11:10:32 +0800
Subject: [PATCH] fix: collect prefix hash values iteratively (#38204)

---
 python/sglang/srt/mem_cache/mamba_radix_cache.py         | 8 +++++---
 python/sglang/srt/mem_cache/radix_cache.py               | 9 +++++----
 .../srt/mem_cache/unified_cache/unified_tree_core.py     | 9 +++++----
 3 files changed, 15 insertions(+), 11 deletions(-)

diff --git a/python/sglang/srt/mem_cache/mamba_radix_cache.py b/python/sglang/srt/mem_cache/mamba_radix_cache.py
index ffbc1ceb0..e98bdec52 100644
--- a/python/sglang/srt/mem_cache/mamba_radix_cache.py
+++ b/python/sglang/srt/mem_cache/mamba_radix_cache.py
@@ -163,9 +163,11 @@ class TreeNode:
         return self.hash_value[-1]
 
     def get_prefix_hash_values(self, node: TreeNode) -> List[str]:
-        if node is None or node.hash_value is None:
-            return []
-        return node.get_prefix_hash_values(node.parent) + node.hash_value
+        chunks = []
+        while node is not None and node.hash_value is not None:
+            chunks.append(node.hash_value)
+            node = node.parent
+        return [value for chunk in reversed(chunks) for value in chunk]
 
     def __lt__(self, other: TreeNode):
         return self.last_access_time < other.last_access_time
diff --git a/python/sglang/srt/mem_cache/radix_cache.py b/python/sglang/srt/mem_cache/radix_cache.py
index 10c527331..f33812cc7 100644
--- a/python/sglang/srt/mem_cache/radix_cache.py
+++ b/python/sglang/srt/mem_cache/radix_cache.py
@@ -311,10 +311,11 @@ class TreeNode:
         return self.hash_value[-1]
 
     def get_prefix_hash_values(self, node: TreeNode) -> List[str]:
-        if node is None or node.hash_value is None:
-            return []
-
-        return node.get_prefix_hash_values(node.parent) + node.hash_value
+        chunks = []
+        while node is not None and node.hash_value is not None:
+            chunks.append(node.hash_value)
+            node = node.parent
+        return [value for chunk in reversed(chunks) for value in chunk]
 
     def __lt__(self, other: TreeNode):
         return self.last_access_time < other.last_access_time
diff --git a/python/sglang/srt/mem_cache/unified_cache/unified_tree_core.py b/python/sglang/srt/mem_cache/unified_cache/unified_tree_core.py
index 072a4abfc..14d909b88 100644
--- a/python/sglang/srt/mem_cache/unified_cache/unified_tree_core.py
+++ b/python/sglang/srt/mem_cache/unified_cache/unified_tree_core.py
@@ -165,10 +165,11 @@ class UnifiedTreeNode:
         return self.hash_value[-1]
 
     def get_prefix_hash_values(self, node: UnifiedTreeNode) -> list[str]:
-        if node is None or node.hash_value is None:
-            return []
-
-        return node.get_prefix_hash_values(node.parent) + node.hash_value
+        chunks = []
+        while node is not None and node.hash_value is not None:
+            chunks.append(node.hash_value)
+            node = node.parent
+        return [value for chunk in reversed(chunks) for value in chunk]
 
 
 class UnifiedLRUList: