diff --git a/evalharness/model/runner.py b/evalharness/model/runner.py
index 1288fd4..5b65a21 100644
--- a/evalharness/model/runner.py
+++ b/evalharness/model/runner.py
@@ -852,13 +852,12 @@ def _make_adapter(spec: str, api_key: str = '') -> ModelAdapter:
         from .pool import pooled
 
         rest = spec[len('openai-pool/'):]
-        ms = __import__('re').findall(r'\{(\d+)\.\.(\d+)\}', rest)
-        if not ms:
-            raise ValueError("openai-pool needs a {start..end} port range")
         base_url, _, model = rest.partition('?')
         # expand EACH comma-separated segment's OWN range independently --
         # a global sub(count=1) would keep replacing only the FIRST range
-        # and emit URLs with literal '{8200..8203}' in later segments
+        # and emit URLs with literal '{8200..8203}' in later segments.
+        # Segments WITHOUT a range are plain members: --auto-concurrency
+        # wraps a single endpoint as a 1-member pool to get the gate.
         specs = []
         for seg in base_url.split(','):
             seg = seg.strip()
@@ -870,6 +869,9 @@ def _make_adapter(spec: str, api_key: str = '') -> ModelAdapter:
                     specs.append(f'openai/{u}?{model}')
             elif seg:
                 specs.append(f'openai/{seg}?{model}')
+        if not specs:
+            raise ValueError('openai-pool needs at least one endpoint '
+                             '(plain URL or {start..end} port range)')
         adapter = pooled(specs, api_key=api_key) if api_key else pooled(specs)
     elif re.fullmatch(r'mock[-:](boxed|oracle|fc|tool|echo|const)?', spec):
         # mock-boxed (preferred) == legacy mock:boxed; bare 'mock' == echo.