diff --git a/tests/portfolio/test_config.py b/tests/portfolio/test_config.py
new file mode 100644
index 00000000..f9c4cfc8
--- /dev/null
+++ b/tests/portfolio/test_config.py
@@ -0,0 +1,104 @@
+"""Tests for tradingagents/portfolio/config.py."""
+
+import pytest
+from tradingagents.portfolio.config import validate_config
+
+def test_validate_config_valid():
+    """Happy path: valid configuration."""
+    cfg = {
+        "max_positions": 10,
+        "max_position_pct": 0.1,
+        "max_sector_pct": 0.3,
+        "min_cash_pct": 0.05,
+        "default_budget": 100000.0
+    }
+    # Should not raise any exception
+    validate_config(cfg)
+
+def test_validate_config_max_positions_invalid():
+    """max_positions must be >= 1."""
+    cfg = {
+        "max_positions": 0,
+        "max_position_pct": 0.1,
+        "max_sector_pct": 0.3,
+        "min_cash_pct": 0.05,
+        "default_budget": 100000.0
+    }
+    with pytest.raises(ValueError, match=r"max_positions must be >= 1"):
+        validate_config(cfg)
+
+    cfg["max_positions"] = -1
+    with pytest.raises(ValueError, match=r"max_positions must be >= 1"):
+        validate_config(cfg)
+
+def test_validate_config_max_position_pct_invalid():
+    """max_position_pct must be in (0, 1]."""
+    cfg = {
+        "max_positions": 10,
+        "max_position_pct": 0.0,
+        "max_sector_pct": 0.3,
+        "min_cash_pct": 0.05,
+        "default_budget": 100000.0
+    }
+    with pytest.raises(ValueError, match=r"max_position_pct must be in \(0, 1\]"):
+        validate_config(cfg)
+
+    cfg["max_position_pct"] = 1.1
+    with pytest.raises(ValueError, match=r"max_position_pct must be in \(0, 1\]"):
+        validate_config(cfg)
+
+def test_validate_config_max_sector_pct_invalid():
+    """max_sector_pct must be in (0, 1]."""
+    cfg = {
+        "max_positions": 10,
+        "max_position_pct": 0.1,
+        "max_sector_pct": 0.0,
+        "min_cash_pct": 0.05,
+        "default_budget": 100000.0
+    }
+    with pytest.raises(ValueError, match=r"max_sector_pct must be in \(0, 1\]"):
+        validate_config(cfg)
+
+    cfg["max_sector_pct"] = 1.1
+    with pytest.raises(ValueError, match=r"max_sector_pct must be in \(0, 1\]"):
+        validate_config(cfg)
+
+def test_validate_config_min_cash_pct_invalid():
+    """min_cash_pct must be in [0, 1)."""
+    cfg = {
+        "max_positions": 10,
+        "max_position_pct": 0.1,
+        "max_sector_pct": 0.3,
+        "min_cash_pct": -0.1,
+        "default_budget": 100000.0
+    }
+    with pytest.raises(ValueError, match=r"min_cash_pct must be in \[0, 1\)"):
+        validate_config(cfg)
+
+    cfg["min_cash_pct"] = 1.0
+    with pytest.raises(ValueError, match=r"min_cash_pct must be in \[0, 1\)"):
+        validate_config(cfg)
+
+def test_validate_config_default_budget_invalid():
+    """default_budget must be > 0."""
+    cfg = {
+        "max_positions": 10,
+        "max_position_pct": 0.1,
+        "max_sector_pct": 0.3,
+        "min_cash_pct": 0.05,
+        "default_budget": 0.0
+    }
+    with pytest.raises(ValueError, match=r"default_budget must be > 0"):
+        validate_config(cfg)
+
+def test_validate_config_sum_constraints_invalid():
+    """min_cash_pct + max_position_pct must be <= 1.0."""
+    cfg = {
+        "max_positions": 10,
+        "max_position_pct": 0.6,
+        "max_sector_pct": 0.3,
+        "min_cash_pct": 0.5,
+        "default_budget": 100000.0
+    }
+    with pytest.raises(ValueError, match=r"must be <= 1.0"):
+        validate_config(cfg)