From a25eccafc952aa654c9d826cfff18e568c32d817 Mon Sep 17 00:00:00 2001
From: mateo-berri <277851410+mateo-berri@users.noreply.github.com>
Date: Wed, 9 Sep 2026 18:32:13 -0700
Subject: [PATCH] fix(azure_ai): drop the api_base path segments a relay
 already repeats

---
 .../azure_ai/passthrough/transformation.py     | 18 +++++++++++++++++-
 ...test_azure_ai_passthrough_transformation.py | 18 ++++++++++++++++++
 2 files changed, 35 insertions(+), 1 deletion(-)

diff --git a/litellm/llms/azure_ai/passthrough/transformation.py b/litellm/llms/azure_ai/passthrough/transformation.py
index 1689755b042..ed630bc6f2b 100644
--- a/litellm/llms/azure_ai/passthrough/transformation.py
+++ b/litellm/llms/azure_ai/passthrough/transformation.py
@@ -62,6 +62,22 @@ def foundry_root(api_base: str) -> str:
     return str(url.copy_with(path="/" + "/".join(root_segments), query=None)).rstrip("/")
 
 
+def without_repeated_native_prefix(root: str, native_endpoint: str) -> str:
+    url: Final = httpx.URL(root)
+    root_segments: Final = tuple(segment for segment in url.path.split("/") if segment)
+    native_segments: Final = tuple(segment.casefold() for segment in native_endpoint.split("/") if segment)
+    overlap: Final = next(
+        (
+            length
+            for length in range(min(len(root_segments), len(native_segments)), 0, -1)
+            if tuple(segment.casefold() for segment in root_segments[-length:]) == native_segments[:length]
+        ),
+        0,
+    )
+    kept_segments: Final = root_segments[: len(root_segments) - overlap]
+    return str(url.copy_with(path="/" + "/".join(kept_segments), query=None)).rstrip("/")
+
+
 def relay_query_params(
     request_query_params: Mapping[str, object] | None,
     deployment_api_version: str | None,
@@ -111,7 +127,7 @@ class AzureAIPassthroughConfig(AzureFoundryModelInfo, BasePassthroughConfig):
             raise ValueError("Azure AI api base not found: set `api_base` on the deployment or AZURE_AI_API_BASE")
 
         native_endpoint: Final = strip_leading_model_segment(endpoint, (model, model_group_from(litellm_params)))
-        root: Final = foundry_root(base_target_url).removesuffix(f"/{native_endpoint.strip('/')}")
+        root: Final = without_repeated_native_prefix(foundry_root(base_target_url), native_endpoint)
         query_params: Final = relay_query_params(
             request_query_params, api_version_from(litellm_params), base_target_url
         )
diff --git a/tests/test_litellm/llms/azure_ai/passthrough/test_azure_ai_passthrough_transformation.py b/tests/test_litellm/llms/azure_ai/passthrough/test_azure_ai_passthrough_transformation.py
index 064be954518..1b9036c50c5 100644
--- a/tests/test_litellm/llms/azure_ai/passthrough/test_azure_ai_passthrough_transformation.py
+++ b/tests/test_litellm/llms/azure_ai/passthrough/test_azure_ai_passthrough_transformation.py
@@ -135,6 +135,24 @@ def test_full_url_api_base_that_already_ends_with_the_native_path_is_not_doubled
     assert base == "https://my-resource.cognitiveservices.azure.com/openai/deployments/model-router"
 
 
+@pytest.mark.parametrize("relayed_deployment", ["gpt-4o", "GPT-4o"])
+def test_deployment_root_api_base_is_not_repeated_when_the_relay_carries_the_deployment_path(relayed_deployment):
+    url, base = AzureAIPassthroughConfig().get_complete_url(
+        api_base="https://my-resource.openai.azure.com/openai/deployments/gpt-4o",
+        api_key="key",
+        model="gpt-4o",
+        endpoint=f"aoai-gpt-4o/openai/deployments/{relayed_deployment}/chat/completions",
+        request_query_params={"api-version": "2024-10-21"},
+        litellm_params={"litellm_metadata": {"model_group": "aoai-gpt-4o"}},
+    )
+
+    assert str(url) == (
+        f"https://my-resource.openai.azure.com/openai/deployments/{relayed_deployment}/chat/completions"
+        "?api-version=2024-10-21"
+    )
+    assert base == "https://my-resource.openai.azure.com"
+
+
 def test_parse_relay_under_a_models_api_base_targets_the_foundry_root():
     url, _ = AzureAIPassthroughConfig().get_complete_url(
         api_base=f"{FOUNDRY_BASE}/models",