diff --git a/agent/auxiliary_client.py b/agent/auxiliary_client.py
index cfc44e5f2a6..102ff79f1ce 100644
--- a/agent/auxiliary_client.py
+++ b/agent/auxiliary_client.py
@@ -3049,10 +3049,17 @@ def resolve_provider_client(
         if custom_entry:
             custom_base = custom_entry.get("base_url", "").strip()
             custom_key = custom_entry.get("api_key", "").strip()
-            custom_key_env = custom_entry.get("key_env", "").strip()
+            custom_key_env = (custom_entry.get("key_env") or custom_entry.get("api_key_env") or "").strip()
             if not custom_key and custom_key_env:
                 custom_key = os.getenv(custom_key_env, "").strip()
             custom_key = custom_key or "no-key-required"
+            if custom_key == "no-key-required":
+                logger.warning(
+                    "resolve_provider_client: named custom provider %r has no resolvable "
+                    "api_key — request will be sent with placeholder no-key-required "
+                    "and will 401 on auth-required endpoints",
+                    custom_entry.get("name") or provider,
+                )
             # An explicit per-task api_mode override (from _resolve_task_provider_model)
             # wins; otherwise fall back to what the provider entry declared.
             entry_api_mode = (api_mode or custom_entry.get("api_mode") or "").strip()