diff --git a/ai_trade/config.py b/ai_trade/config.py
index 53c793a..d120605 100644
--- a/ai_trade/config.py
+++ b/ai_trade/config.py
@@ -53,6 +53,9 @@ class Settings:
     min_momentum_for_buy: str = field(
         default_factory=lambda: os.getenv("MIN_MOMENTUM_FOR_BUY", "strong_up")
     )
+    signal_ttl_seconds: int = field(
+        default_factory=lambda: int(os.getenv("SIGNAL_TTL_SECONDS", "300"))
+    )
 
     @property
     def kis_is_virtual(self) -> bool:
diff --git a/ai_trade/tests/test_state_signals_lifecycle.py b/ai_trade/tests/test_state_signals_lifecycle.py
index ba785b9..310a9dd 100644
--- a/ai_trade/tests/test_state_signals_lifecycle.py
+++ b/ai_trade/tests/test_state_signals_lifecycle.py
@@ -48,3 +48,19 @@ def test_purge_expired_signals_removes_expired():
     assert "A" in state.signals
     assert "B" not in state.signals
     assert removed == 1
+
+
+# ----- SIGNAL_TTL_SECONDS env -----
+
+def test_signal_ttl_seconds_default(monkeypatch):
+    monkeypatch.delenv("SIGNAL_TTL_SECONDS", raising=False)
+    from ai_trade.config import Settings
+    s = Settings()
+    assert s.signal_ttl_seconds == 300
+
+
+def test_signal_ttl_seconds_env_override(monkeypatch):
+    monkeypatch.setenv("SIGNAL_TTL_SECONDS", "60")
+    from ai_trade.config import Settings
+    s = Settings()
+    assert s.signal_ttl_seconds == 60