fix: treat empty OPENAI_BASE_URL same as None for default fallback

fix_base_url.py

@@ -0,0 +1,45 @@
+#!/usr/bin/env python3
+"""Fix script for issue #2927: empty OPENAI_BASE_URL should fallback to default"""
+
+file_path = "src/openai/_client.py"
+
+with open(file_path, 'r') as f:
+    lines = f.readlines()
+
+modified_lines = []
+i = 0
+while i < len(lines):
+    line = lines[i]
+
+    # Look for the pattern:
+    # if base_url is None:
+    #     base_url = os.environ.get("OPENAI_BASE_URL")
+    # if base_url is None:
+    #     base_url = f"https://api.openai.com/v1"
+
+    if 'if base_url is None:' in line and i+1 < len(lines):
+        next_line = lines[i+1]
+        if 'base_url = os.environ.get("OPENAI_BASE_URL")' in next_line:
+            # This is the first "if base_url is None"
+            # Keep it as is
+            modified_lines.append(line)
+            modified_lines.append(next_line)
+            i += 2
+
+            # Now check if the next line is the second "if base_url is None"
+            if i < len(lines) and 'if base_url is None:' in lines[i]:
+                # Replace this second check with "if not base_url:"
+                indent = lines[i][:lines[i].index('if')]
+                modified_lines.append(f"{indent}# Treat empty string same as None to allow fallback to default\n")
+                modified_lines.append(f"{indent}# Fixes #2927: export OPENAI_BASE_URL=\"\" should not prevent default URL\n")
+                modified_lines.append(f"{indent}if not base_url:\n")
+                i += 1
+            continue
+
+    modified_lines.append(line)
+    i += 1
+
+with open(file_path, 'w') as f:
+    f.writelines(modified_lines)
+
+print("✅ Fixed both occurrences (sync and async clients)")

src/openai/_client.py

@@ -162,7 +162,9 @@ def __init__(
 
         if base_url is None:
             base_url = os.environ.get("OPENAI_BASE_URL")
-        if base_url is None:
+        # Treat empty string same as None to allow fallback to default
+        # Fixes #2927: export OPENAI_BASE_URL="" should not prevent default URL
+        if not base_url:
             base_url = f"https://api.openai.com/v1"
 
         super().__init__(
@@ -537,7 +539,9 @@ def __init__(
 
         if base_url is None:
             base_url = os.environ.get("OPENAI_BASE_URL")
-        if base_url is None:
+        # Treat empty string same as None to allow fallback to default
+        # Fixes #2927: export OPENAI_BASE_URL="" should not prevent default URL
+        if not base_url:
             base_url = f"https://api.openai.com/v1"
 
         super().__init__(