From ce8a520a86b0baf83bb779094ebccbc229363041 Mon Sep 17 00:00:00 2001
From: Achintya Rajan <achintya.rajan03@gmail.com>
Date: Wed, 8 Oct 2025 14:40:01 -0700
Subject: [PATCH] new deep merge behavior when processing config

---
 litellm/proxy/proxy_server.py              | 23 ++++++--
 tests/proxy_unit_tests/test_proxy_utils.py | 68 ++++++++++++++++++++++
 2 files changed, 85 insertions(+), 6 deletions(-)

diff --git a/litellm/proxy/proxy_server.py b/litellm/proxy/proxy_server.py
index 7a1e8f1e73..7feb4b825b 100644
--- a/litellm/proxy/proxy_server.py
+++ b/litellm/proxy/proxy_server.py
@@ -2885,6 +2885,20 @@ class ProxyConfig:
             dict: Updated configuration dictionary
         """
 
+        def _deep_merge_dicts(dst: dict, src: dict) -> None:
+            """
+            Deep-merge src into dst, skipping None values from src.
+            On conflicts, src (DB) wins.
+            """
+            for k, v in src.items():
+                if v is None:
+                    # Preserve existing config when DB value is None (matches prior behavior)
+                    continue
+                if isinstance(v, dict) and isinstance(dst.get(k), dict):
+                    _deep_merge_dicts(dst[k], v)
+                else:
+                    dst[k] = v
+
         if param_name == "environment_variables":
             decrypted_env_vars = self._decrypt_and_set_db_env_variables(db_param_value)
             current_config.setdefault("environment_variables", {}).update(
@@ -2905,13 +2919,10 @@ class ProxyConfig:
             return current_config
 
         # For dictionary values, update only non-none values
-        if isinstance(current_config[param_name], dict):
-            # Only keep non None values from db_param_value
-            non_none_values = {k: v for k, v in db_param_value.items() if v is not None}
-
-            # Update the config with non-none values
-            current_config[param_name].update(non_none_values)
+        if isinstance(current_config[param_name], dict) and isinstance(db_param_value, dict):
+            _deep_merge_dicts(current_config[param_name], db_param_value)
         else:
+            # Non-dict or mismatched types: DB value replaces config (unchanged behavior)
             current_config[param_name] = db_param_value
 
         return current_config
diff --git a/tests/proxy_unit_tests/test_proxy_utils.py b/tests/proxy_unit_tests/test_proxy_utils.py
index 34a8a9daf8..9b01f21c58 100644
--- a/tests/proxy_unit_tests/test_proxy_utils.py
+++ b/tests/proxy_unit_tests/test_proxy_utils.py
@@ -1029,6 +1029,74 @@ def test_update_config_fields():
     assert team_config["langfuse_secret"] == "my-fake-secret"
 
 
+def test_update_config_fields_deep_merge_db_wins():
+    from litellm.proxy.proxy_server import ProxyConfig
+
+    proxy_config = ProxyConfig()
+
+    current_config = {
+        "router_settings": {
+            "routing_mode": "cost_optimized",
+            "model_group_alias": {
+                # Existing alias with older model + different hidden flag
+                "claude-sonnet-4": {
+                    "model": "claude-sonnet-4-20240219",
+                    "hidden": True,
+                },
+                # An extra alias that should remain untouched unless DB overrides it
+                "legacy-sonnet": {
+                    "model": "claude-2.1",
+                    "hidden": True,
+                },
+            },
+        }
+    }
+
+    db_param_value = {
+        "model_group_alias": {
+            # Conflict: DB should win (both 'model' and 'hidden')
+            "claude-sonnet-4": {
+                "model": "claude-sonnet-4-20250514",
+                "hidden": False,
+            },
+            # New alias to be added by the merge
+            "claude-sonnet-latest": {
+                "model": "claude-sonnet-4-20250514",
+                "hidden": True,
+            },
+            # Demonstrate that None values from DB are skipped (preserve existing)
+            "legacy-sonnet": {
+                "hidden": None  # should not clobber current True
+            },
+        }
+    }
+
+    updated = proxy_config._update_config_fields(
+        current_config=current_config,
+        param_name="router_settings",
+        db_param_value=db_param_value,
+    )
+
+    rs = updated["router_settings"]
+    aliases = rs["model_group_alias"]
+
+    # DB wins on conflicts (deep) for existing alias
+    assert aliases["claude-sonnet-4"]["model"] == "claude-sonnet-4-20250514"
+    assert aliases["claude-sonnet-4"]["hidden"] is False
+
+    # New alias introduced by DB is present with its values
+    assert "claude-sonnet-latest" in aliases
+    assert aliases["claude-sonnet-latest"]["model"] == "claude-sonnet-4-20250514"
+    assert aliases["claude-sonnet-latest"]["hidden"] is True
+
+    # None in DB does not overwrite existing values
+    assert aliases["legacy-sonnet"]["model"] == "claude-2.1"
+    assert aliases["legacy-sonnet"]["hidden"] is True
+
+    # Unrelated router_settings keys are preserved
+    assert rs["routing_mode"] == "cost_optimized"
+
+
 def test_update_config_fields_default_internal_user_params(monkeypatch):
     from litellm.proxy.proxy_server import ProxyConfig