Normalize OpenAI base URLs

src/aituner/http_client.py

@@ -22,6 +22,14 @@ def _auth_headers(api_key_env: str | None) -> dict[str, str]:
     return headers
 
 
+def _openai_url(base_url: str, path: str) -> str:
+    root = base_url.rstrip("/")
+    normalized_path = "/" + path.lstrip("/")
+    if root.endswith("/v1") and normalized_path.startswith("/v1/"):
+        normalized_path = normalized_path[len("/v1") :]
+    return root + normalized_path
+
+
 def wait_for_server(base_url: str, path: str, timeout_s: float) -> None:
     deadline = time.monotonic() + timeout_s
     url = f"{base_url.rstrip('/')}{path}"
@@ -52,7 +60,7 @@ def chat_completion(
         payload["messages"] = [{"role": "system", "content": system_prompt}, *messages]
     data = json.dumps(payload).encode("utf-8")
     request = urllib.request.Request(
-        url=f"{base_url.rstrip('/')}/v1/chat/completions",
+        url=_openai_url(base_url, "/v1/chat/completions"),
         headers=_auth_headers(api_key_env),
         data=data,
         method="POST",
@@ -80,7 +88,7 @@ def stream_chat_completion(
 ) -> StreamMetrics:
     data = json.dumps(body).encode("utf-8")
     request = urllib.request.Request(
-        url=f"{base_url.rstrip('/')}/v1/chat/completions",
+        url=_openai_url(base_url, "/v1/chat/completions"),
         headers=_auth_headers(None),
         data=data,
         method="POST",

tests/test_core_flow.py

@@ -8,6 +8,7 @@ from pathlib import Path
 from unittest import mock
 
 from aituner.cli import main as cli_main
+from aituner.http_client import _openai_url
 from aituner.job import append_job, build_trial_job
 from aituner.llm import build_prompt, parse_proposal_text
 from aituner.search import ThresholdProbe, binary_search_max_feasible
@@ -717,6 +718,16 @@ class CoreFlowTests(unittest.TestCase):
         self.assertEqual(len(replayed), 3)
         self.assertEqual(replayed[1].error, "slo_pass_rate_unrecoverable")
 
+    def test_openai_url_avoids_double_v1(self) -> None:
+        self.assertEqual(
+            _openai_url("http://example.com", "/v1/chat/completions"),
+            "http://example.com/v1/chat/completions",
+        )
+        self.assertEqual(
+            _openai_url("http://example.com/v1", "/v1/chat/completions"),
+            "http://example.com/v1/chat/completions",
+        )
+
 
 if __name__ == "__main__":
     unittest.main()