From 56ff4548e2d2cb63f2929f6c3ba7089d22901e81 Mon Sep 17 00:00:00 2001
From: Li-john1021 <215793081+Li-john1021@users.noreply.github.com>
Date: Thu, 15 Oct 2026 14:29:50 +0800
Subject: [PATCH] fix(anthropic): drop list annotation in thought-signature id
 parse

LIT001 ceiling was one over merge-base because Final[list[str]] on the
split of tool_call.id. Use str.partition instead so the signature path
adds no mutable collection annotation.
---
 .../llms/anthropic/pass_through/adapters/transformation.py  | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/litellm/llms/anthropic/pass_through/adapters/transformation.py b/litellm/llms/anthropic/pass_through/adapters/transformation.py
index 9340f9741d9..86c0866330e 100644
--- a/litellm/llms/anthropic/pass_through/adapters/transformation.py
+++ b/litellm/llms/anthropic/pass_through/adapters/transformation.py
@@ -386,9 +386,9 @@ class LiteLLMAnthropicMessagesAdapter:
 
         raw_id: Final[object] = _optional_attr(tool_call, "id")
         if isinstance(raw_id, str) and THOUGHT_SIGNATURE_SEPARATOR in raw_id:
-            parts: Final[list[str]] = raw_id.split(THOUGHT_SIGNATURE_SEPARATOR, 1)
-            if len(parts) == 2 and parts[1]:
-                return parts[1]
+            _, _, embedded = raw_id.partition(THOUGHT_SIGNATURE_SEPARATOR)
+            if embedded:
+                return embedded
 
         return None