diff --git a/gateway/platforms/helpers.py b/gateway/platforms/helpers.py
index c834dd89c..18d97fcb7 100644
--- a/gateway/platforms/helpers.py
+++ b/gateway/platforms/helpers.py
@@ -49,7 +49,10 @@ class MessageDeduplicator:
             return False
         now = time.time()
         if msg_id in self._seen:
-            return True
+            if now - self._seen[msg_id] < self._ttl:
+                return True
+            # Entry has expired — remove it and treat as new
+            del self._seen[msg_id]
         self._seen[msg_id] = now
         if len(self._seen) > self._max_size:
             cutoff = now - self._ttl
diff --git a/gateway/run.py b/gateway/run.py
index 327f8ae32..ea45dcdd3 100644
--- a/gateway/run.py
+++ b/gateway/run.py
@@ -9725,9 +9725,9 @@ def main():
     
     config = None
     if args.config:
-        import json
+        import yaml
         with open(args.config, encoding="utf-8") as f:
-            data = json.load(f)
+            data = yaml.safe_load(f)
             config = GatewayConfig.from_dict(data)
     
     # Run the gateway - exit with code 1 if no platforms connected,
diff --git a/tests/gateway/test_message_deduplicator.py b/tests/gateway/test_message_deduplicator.py
new file mode 100644
index 000000000..59fe7e394
--- /dev/null
+++ b/tests/gateway/test_message_deduplicator.py
@@ -0,0 +1,89 @@
+"""Tests for MessageDeduplicator TTL enforcement (#10306).
+
+Previously, is_duplicate() returned True for any previously seen ID without
+checking its age — expired entries were only purged when cache size exceeded
+max_size.  Normal workloads never overflowed, so messages stayed "duplicate"
+forever.
+
+The fix checks TTL at query time: if the entry's timestamp plus TTL is in
+the past, the entry is treated as expired and the message is allowed through.
+"""
+
+import time
+from unittest.mock import patch
+
+from gateway.platforms.helpers import MessageDeduplicator
+
+
+class TestMessageDeduplicatorTTL:
+    """TTL-based expiration must work regardless of cache size."""
+
+    def test_duplicate_within_ttl(self):
+        """Same message within TTL window is duplicate."""
+        dedup = MessageDeduplicator(ttl_seconds=60)
+        assert dedup.is_duplicate("msg-1") is False
+        assert dedup.is_duplicate("msg-1") is True
+
+    def test_not_duplicate_after_ttl_expires(self):
+        """Same message AFTER TTL expires should NOT be duplicate."""
+        dedup = MessageDeduplicator(ttl_seconds=5)
+        assert dedup.is_duplicate("msg-1") is False
+
+        # Fast-forward time past TTL
+        dedup._seen["msg-1"] = time.time() - 10  # 10s ago, TTL is 5s
+        assert dedup.is_duplicate("msg-1") is False, \
+            "Expired entry should not be treated as duplicate"
+
+    def test_expired_entry_gets_refreshed(self):
+        """After an expired entry is allowed through, it should be re-tracked."""
+        dedup = MessageDeduplicator(ttl_seconds=5)
+        assert dedup.is_duplicate("msg-1") is False
+
+        # Expire the entry
+        dedup._seen["msg-1"] = time.time() - 10
+
+        # Should be allowed through (expired)
+        assert dedup.is_duplicate("msg-1") is False
+        # Now should be duplicate again (freshly tracked)
+        assert dedup.is_duplicate("msg-1") is True
+
+    def test_different_messages_not_confused(self):
+        """Different message IDs are independent."""
+        dedup = MessageDeduplicator(ttl_seconds=60)
+        assert dedup.is_duplicate("msg-1") is False
+        assert dedup.is_duplicate("msg-2") is False
+        assert dedup.is_duplicate("msg-1") is True
+        assert dedup.is_duplicate("msg-2") is True
+
+    def test_empty_id_never_duplicate(self):
+        """Empty/None message IDs are never treated as duplicate."""
+        dedup = MessageDeduplicator(ttl_seconds=60)
+        assert dedup.is_duplicate("") is False
+        assert dedup.is_duplicate("") is False
+
+    def test_max_size_eviction_prunes_expired(self):
+        """Cache pruning on overflow removes expired entries."""
+        dedup = MessageDeduplicator(max_size=5, ttl_seconds=60)
+        # Add 6 entries, with the first 3 expired
+        now = time.time()
+        for i in range(3):
+            dedup._seen[f"old-{i}"] = now - 120  # expired (2 min ago, TTL 60s)
+        for i in range(3):
+            dedup.is_duplicate(f"new-{i}")
+        # Now we have 6 entries. Next insert triggers pruning.
+        dedup.is_duplicate("trigger")
+        # The 3 expired entries should be gone, leaving 4 fresh ones
+        assert len(dedup._seen) == 4
+        assert "old-0" not in dedup._seen
+        assert "new-0" in dedup._seen
+
+    def test_ttl_zero_means_no_dedup(self):
+        """With TTL=0, all entries expire immediately."""
+        dedup = MessageDeduplicator(ttl_seconds=0)
+        assert dedup.is_duplicate("msg-1") is False
+        # Entry was just added at time.time(), and TTL is 0,
+        # so now - seen_time >= 0 = ttl, meaning it's expired
+        # But time.time() might be the exact same float, so
+        # the check is `now - ts < ttl` which is `0 < 0` = False
+        # This means TTL=0 effectively disables dedup
+        assert dedup.is_duplicate("msg-1") is False