From ebf84c423719dadf6253a0e79ca64c8979e6bd30 Mon Sep 17 00:00:00 2001
From: Ritika shrestha <87307821+ritsth@users.noreply.github.com>
Date: Sun, 28 Jun 2026 14:27:03 -0700
Subject: [PATCH] fix(cohere): avoid duplicate /v2 in rerank v2 url for
 versioned api_base

When api_base already ends in /v2 (the documented Cohere v2 root), the rerank
v2 url builder appended /v2/rerank again, producing /v2/v2/rerank. Normalize so
a versioned root resolves to /v2/rerank and a bare host still gets /v2/rerank.

Fixes #31167
---
 .../llms/cohere/rerank_v2/transformation.py   | 11 +++++----
 .../cohere/rerank_v2/test_transformation.py   | 24 +++++++++++++++++++
 2 files changed, 30 insertions(+), 5 deletions(-)
 create mode 100644 tests/test_litellm/llms/cohere/rerank_v2/test_transformation.py

diff --git a/litellm/llms/cohere/rerank_v2/transformation.py b/litellm/llms/cohere/rerank_v2/transformation.py
index 7c68a431a90..a4e73d4d838 100644
--- a/litellm/llms/cohere/rerank_v2/transformation.py
+++ b/litellm/llms/cohere/rerank_v2/transformation.py
@@ -19,11 +19,12 @@ class CohereRerankV2Config(CohereRerankConfig):
         optional_params: dict | None = None,
     ) -> str:
         if api_base:
-            # Remove trailing slashes and ensure clean base URL
-            api_base = api_base.rstrip("/")
-            if not api_base.endswith("/v2/rerank"):
-                api_base = f"{api_base}/v2/rerank"
-            return api_base
+            base = api_base.rstrip("/")
+            if base.endswith("/v2/rerank"):
+                return base
+            if base.endswith("/v2"):
+                return f"{base}/rerank"
+            return f"{base}/v2/rerank"
         return "https://api.cohere.ai/v2/rerank"
 
     def get_supported_cohere_rerank_params(self, model: str) -> list:
diff --git a/tests/test_litellm/llms/cohere/rerank_v2/test_transformation.py b/tests/test_litellm/llms/cohere/rerank_v2/test_transformation.py
new file mode 100644
index 00000000000..ee5cafa1f1d
--- /dev/null
+++ b/tests/test_litellm/llms/cohere/rerank_v2/test_transformation.py
@@ -0,0 +1,24 @@
+import pytest
+
+from litellm.llms.cohere.rerank_v2.transformation import CohereRerankV2Config
+
+
+@pytest.mark.parametrize(
+    "api_base, expected",
+    [
+        # versioned root must not duplicate the version segment (#31167)
+        ("https://api.cohere.ai/v2", "https://api.cohere.ai/v2/rerank"),
+        ("https://api.cohere.ai/v2/", "https://api.cohere.ai/v2/rerank"),
+        # bare host gets the full v2 rerank path
+        ("https://api.cohere.ai", "https://api.cohere.ai/v2/rerank"),
+        # already-complete url is left untouched
+        ("https://api.cohere.ai/v2/rerank", "https://api.cohere.ai/v2/rerank"),
+        # self-hosted gateway exposing a versioned root
+        ("https://gateway.internal/cohere/v2", "https://gateway.internal/cohere/v2/rerank"),
+        # no api_base falls back to the public endpoint
+        (None, "https://api.cohere.ai/v2/rerank"),
+    ],
+)
+def test_get_complete_url_does_not_duplicate_version(api_base, expected):
+    config = CohereRerankV2Config()
+    assert config.get_complete_url(api_base=api_base, model="rerank-v3.5") == expected