diff --git a/tests/__init__.py b/tests/__init__.py
new file mode 100644
index 0000000000..e69de29bb2
diff --git a/tests/test_multi_vendor_routing.py b/tests/test_multi_vendor_routing.py
new file mode 100644
index 0000000000..d523fbafae
--- /dev/null
+++ b/tests/test_multi_vendor_routing.py
@@ -0,0 +1,183 @@
+"""
+Unit tests for multi-vendor routing logic.
+
+These tests use mocked vendor implementations and can run without API keys,
+making them suitable for CI/CD environments.
+
+Run with: pytest tests/test_multi_vendor_routing.py -v
+"""
+
+import pytest
+from unittest.mock import patch, MagicMock
+import sys
+import os
+
+# Add parent directory to path
+sys.path.insert(0, os.path.dirname(os.path.dirname(os.path.abspath(__file__))))
+
+
+@pytest.fixture
+def mock_vendors():
+    """Create mock vendor functions with __name__ attribute."""
+    mock_a = MagicMock(return_value="Result from Vendor A")
+    mock_a.__name__ = "mock_vendor_a"
+    
+    mock_b = MagicMock(return_value="Result from Vendor B")
+    mock_b.__name__ = "mock_vendor_b"
+    
+    mock_c = MagicMock(return_value="Result from Vendor C")
+    mock_c.__name__ = "mock_vendor_c"
+    
+    return {'a': mock_a, 'b': mock_b, 'c': mock_c}
+
+
+@pytest.fixture
+def mock_routing(mock_vendors):
+    """Set up mocked routing environment."""
+    with patch('tradingagents.dataflows.interface.VENDOR_METHODS', {
+        'test_method': {
+            'vendor_a': mock_vendors['a'],
+            'vendor_b': mock_vendors['b'],
+            'vendor_c': mock_vendors['c'],
+        }
+    }), \
+    patch('tradingagents.dataflows.interface.get_category_for_method', return_value='test_category'), \
+    patch('tradingagents.dataflows.interface.get_config') as mock_config:
+        yield mock_config, mock_vendors
+
+
+def test_single_vendor_stops_after_success(mock_routing):
+    """Test that single vendor config stops after first successful vendor."""
+    mock_config, mock_vendors = mock_routing
+    
+    # Configure single vendor
+    mock_config.return_value = {
+        'data_vendors': {'test_category': 'vendor_a'},
+        'tool_vendors': {}
+    }
+    
+    from tradingagents.dataflows.interface import route_to_vendor
+    
+    result = route_to_vendor('test_method', 'arg1', 'arg2')
+    
+    # Assertions
+    mock_vendors['a'].assert_called_once_with('arg1', 'arg2')
+    mock_vendors['b'].assert_not_called()  # Should not try fallback
+    mock_vendors['c'].assert_not_called()  # Should not try fallback
+    assert result == 'Result from Vendor A'
+
+
+def test_multi_vendor_stops_after_all_primaries_success(mock_routing):
+    """Test that multi-vendor stops after all primaries when they succeed."""
+    mock_config, mock_vendors = mock_routing
+    
+    # Configure two primary vendors
+    mock_config.return_value = {
+        'data_vendors': {'test_category': 'vendor_a,vendor_b'},
+        'tool_vendors': {}
+    }
+    
+    from tradingagents.dataflows.interface import route_to_vendor
+    
+    result = route_to_vendor('test_method', 'arg1')
+    
+    # Assertions
+    mock_vendors['a'].assert_called_once_with('arg1')
+    mock_vendors['b'].assert_called_once_with('arg1')
+    mock_vendors['c'].assert_not_called()  # Should NOT try fallback
+    
+    # Result should contain both
+    assert 'Result from Vendor A' in result
+    assert 'Result from Vendor B' in result
+
+
+def test_multi_vendor_stops_after_all_primaries_failure(mock_routing):
+    """Test that multi-vendor stops after all primaries even when they fail."""
+    mock_config, mock_vendors = mock_routing
+    
+    # Configure two primary vendors that will fail
+    mock_vendors['a'].side_effect = Exception("Vendor A failed")
+    mock_vendors['b'].side_effect = Exception("Vendor B failed")
+    
+    mock_config.return_value = {
+        'data_vendors': {'test_category': 'vendor_a,vendor_b'},
+        'tool_vendors': {}
+    }
+    
+    from tradingagents.dataflows.interface import route_to_vendor
+    
+    # Should raise error after trying all primaries
+    with pytest.raises(RuntimeError, match="All vendor implementations failed"):
+        route_to_vendor('test_method', 'arg1')
+    
+    # Assertions
+    mock_vendors['a'].assert_called_once_with('arg1')
+    mock_vendors['b'].assert_called_once_with('arg1')
+    mock_vendors['c'].assert_not_called()  # Should NOT try fallback
+
+
+def test_multi_vendor_partial_failure_stops_after_primaries(mock_routing):
+    """Test that multi-vendor stops after all primaries even if one fails."""
+    mock_config, mock_vendors = mock_routing
+    
+    # First vendor fails, second succeeds
+    mock_vendors['a'].side_effect = Exception("Vendor A failed")
+    
+    mock_config.return_value = {
+        'data_vendors': {'test_category': 'vendor_a,vendor_b'},
+        'tool_vendors': {}
+    }
+    
+    from tradingagents.dataflows.interface import route_to_vendor
+    
+    result = route_to_vendor('test_method', 'arg1')
+    
+    # Assertions
+    mock_vendors['a'].assert_called_once_with('arg1')
+    mock_vendors['b'].assert_called_once_with('arg1')
+    mock_vendors['c'].assert_not_called()  # Should NOT try fallback
+    
+    assert result == 'Result from Vendor B'
+
+
+def test_single_vendor_uses_fallback_on_failure(mock_routing):
+    """Test that single vendor uses fallback if primary fails."""
+    mock_config, mock_vendors = mock_routing
+    
+    # Primary vendor fails
+    mock_vendors['a'].side_effect = Exception("Vendor A failed")
+    
+    mock_config.return_value = {
+        'data_vendors': {'test_category': 'vendor_a'},
+        'tool_vendors': {}
+    }
+    
+    from tradingagents.dataflows.interface import route_to_vendor
+    
+    result = route_to_vendor('test_method', 'arg1')
+    
+    # Assertions
+    mock_vendors['a'].assert_called_once_with('arg1')
+    mock_vendors['b'].assert_called_once_with('arg1')  # Should try fallback
+    assert result == 'Result from Vendor B'
+
+
+def test_tool_level_override_takes_precedence(mock_routing):
+    """Test that tool-level vendor config overrides category-level."""
+    mock_config, mock_vendors = mock_routing
+    
+    # Category says vendor_a, but tool override says vendor_b
+    mock_config.return_value = {
+        'data_vendors': {'test_category': 'vendor_a'},
+        'tool_vendors': {'test_method': 'vendor_b'}
+    }
+    
+    from tradingagents.dataflows.interface import route_to_vendor
+    
+    result = route_to_vendor('test_method', 'arg1')
+    
+    # Assertions
+    mock_vendors['a'].assert_not_called()  # Category default ignored
+    mock_vendors['b'].assert_called_once_with('arg1')  # Tool override used
+    assert result == 'Result from Vendor B'
+
diff --git a/tradingagents/dataflows/interface.py b/tradingagents/dataflows/interface.py
index 4cd5ddef3a..27857f2c40 100644
--- a/tradingagents/dataflows/interface.py
+++ b/tradingagents/dataflows/interface.py
@@ -166,7 +166,7 @@ def route_to_vendor(method: str, *args, **kwargs):
     # Track results and execution state
     results = []
     vendor_attempt_count = 0
-    any_primary_vendor_attempted = False
+    primary_vendors_attempted = []
     successful_vendor = None
 
     for vendor in fallback_vendors:
@@ -179,10 +179,6 @@ def route_to_vendor(method: str, *args, **kwargs):
         is_primary_vendor = vendor in primary_vendors
         vendor_attempt_count += 1
 
-        # Track if we attempted any primary vendor
-        if is_primary_vendor:
-            any_primary_vendor_attempted = True
-
         # Debug: Print current attempt
         vendor_type = "PRIMARY" if is_primary_vendor else "FALLBACK"
         print(f"DEBUG: Attempting {vendor_type} vendor '{vendor}' for {method} (attempt #{vendor_attempt_count})")
@@ -214,6 +210,10 @@ def route_to_vendor(method: str, *args, **kwargs):
                 print(f"FAILED: {impl_func.__name__} from vendor '{vendor_name}' failed: {e}")
                 continue
 
+        # Track which primary vendors we've attempted
+        if is_primary_vendor:
+            primary_vendors_attempted.append(vendor)
+
         # Add this vendor's results
         if vendor_results:
             results.extend(vendor_results)
@@ -221,13 +221,17 @@ def route_to_vendor(method: str, *args, **kwargs):
             result_summary = f"Got {len(vendor_results)} result(s)"
             print(f"SUCCESS: Vendor '{vendor}' succeeded - {result_summary}")
             
-            # Stopping logic: Stop after first successful vendor for single-vendor configs
-            # Multiple vendor configs (comma-separated) may want to collect from multiple sources
+            # Stopping logic for single vendor: Stop after first success
             if len(primary_vendors) == 1:
                 print(f"DEBUG: Stopping after successful vendor '{vendor}' (single-vendor config)")
                 break
         else:
             print(f"FAILED: Vendor '{vendor}' produced no results")
+        
+        # Stopping logic for multi-vendor: Stop after all primaries attempted (regardless of success)
+        if len(primary_vendors) > 1 and set(primary_vendors_attempted) == set(primary_vendors):
+            print(f"DEBUG: All primary vendors attempted ({', '.join(primary_vendors_attempted)}), stopping")
+            break
 
     # Final result summary
     if not results: