From 75a9842f1a714ec464552d8744d8295caacf3782 Mon Sep 17 00:00:00 2001
From: Gahow Wang <gahow.wang@gmail.com>
Date: Sat, 4 Apr 2026 23:50:42 +0800
Subject: [PATCH] Bypass proxies for loopback engines

---
 src/aituner/http_client.py | 27 ++++++++++++++++++++++++---
 tests/test_core_flow.py    |  7 ++++++-
 2 files changed, 30 insertions(+), 4 deletions(-)

diff --git a/src/aituner/http_client.py b/src/aituner/http_client.py
index 61e98a7..33550ae 100644
--- a/src/aituner/http_client.py
+++ b/src/aituner/http_client.py
@@ -5,14 +5,35 @@ import os
 import time
 import urllib.error
 import urllib.request
+from ipaddress import ip_address
 from dataclasses import dataclass
 from typing import Any, Iterable
+from urllib.parse import urlparse
 
 
 class HttpClientError(RuntimeError):
     """Raised for HTTP client failures."""
 
 
+def _should_bypass_proxy(url: str) -> bool:
+    host = (urlparse(url).hostname or "").strip()
+    if not host:
+        return False
+    if host == "localhost":
+        return True
+    try:
+        return ip_address(host).is_loopback
+    except ValueError:
+        return False
+
+
+def _urlopen(request: urllib.request.Request, *, timeout: float):
+    if _should_bypass_proxy(request.full_url):
+        opener = urllib.request.build_opener(urllib.request.ProxyHandler({}))
+        return opener.open(request, timeout=timeout)
+    return urllib.request.urlopen(request, timeout=timeout)
+
+
 def _auth_headers(api_key_env: str | None) -> dict[str, str]:
     headers = {"Content-Type": "application/json"}
     if api_key_env:
@@ -37,7 +58,7 @@ def wait_for_server(base_url: str, path: str, timeout_s: float) -> None:
     while time.monotonic() < deadline:
         try:
             request = urllib.request.Request(url=url, headers=_auth_headers(None), method="GET")
-            with urllib.request.urlopen(request, timeout=5) as response:
+            with _urlopen(request, timeout=5) as response:
                 if 200 <= response.status < 500:
                     return
         except Exception as exc:  # noqa: BLE001
@@ -66,7 +87,7 @@ def chat_completion(
         method="POST",
     )
     try:
-        with urllib.request.urlopen(request, timeout=timeout_s) as response:
+        with _urlopen(request, timeout=timeout_s) as response:
             return json.loads(response.read().decode("utf-8"))
     except urllib.error.HTTPError as exc:
         detail = exc.read().decode("utf-8", errors="replace")
@@ -99,7 +120,7 @@ def stream_chat_completion(
     chunk_token_count = 0
     completion_tokens: int | None = None
     try:
-        with urllib.request.urlopen(request, timeout=timeout_s) as response:
+        with _urlopen(request, timeout=timeout_s) as response:
             for raw in _iter_sse_lines(response):
                 if raw == "[DONE]":
                     break
diff --git a/tests/test_core_flow.py b/tests/test_core_flow.py
index 12d7b76..4b7fa7b 100644
--- a/tests/test_core_flow.py
+++ b/tests/test_core_flow.py
@@ -8,7 +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.http_client import _openai_url, _should_bypass_proxy
 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
@@ -833,6 +833,11 @@ class CoreFlowTests(unittest.TestCase):
             "http://example.com/v1/chat/completions",
         )
 
+    def test_loopback_urls_bypass_proxy(self) -> None:
+        self.assertTrue(_should_bypass_proxy("http://127.0.0.1:8000/v1/models"))
+        self.assertTrue(_should_bypass_proxy("http://localhost:8000/health"))
+        self.assertFalse(_should_bypass_proxy("http://example.com/v1/models"))
+
 
 if __name__ == "__main__":
     unittest.main()