diff --git a/evalharness/cli.py b/evalharness/cli.py
index 0bc253a..d1f9f61 100644
--- a/evalharness/cli.py
+++ b/evalharness/cli.py
@@ -546,6 +546,10 @@ def _compose_judge_spec(args):
     url = getattr(args, 'judge_api_url', '') or ''
     provider = getattr(args, 'judge_provider', 'openai-chat') or 'openai-chat'
     internal = {'openai-chat': 'openai', 'openai-pool': 'openai-pool'}.get(provider, provider)
+    if judge and not url and '/' not in judge:
+        raise SystemExit(
+            f'--judge-model {judge!r} needs --judge-api-url (or pass a full '
+            f'spec like openai/http://host:8000/v1?{judge})')
     if url and judge and '/' not in judge:
         judge = f'{internal}/{url.rstrip("/")}?{judge}'
     return judge or None
@@ -640,6 +644,10 @@ def _compose_judge_spec(args):
     url = getattr(args, 'judge_api_url', '') or ''
     provider = getattr(args, 'judge_provider', 'openai-chat') or 'openai-chat'
     internal = {'openai-chat': 'openai', 'openai-pool': 'openai-pool'}.get(provider, provider)
+    if judge and not url and '/' not in judge:
+        raise SystemExit(
+            f'--judge-model {judge!r} needs --judge-api-url (or pass a full '
+            f'spec like openai/http://host:8000/v1?{judge})')
     if url and judge and '/' not in judge:
         judge = f'{internal}/{url.rstrip("/")}?{judge}'
     return judge or None