diff --git a/backend/ai.py b/backend/ai.py
index d16befa..53f8115 100644
--- a/backend/ai.py
+++ b/backend/ai.py
@@ -125,7 +125,8 @@ def _extract_json(text: str) -> dict[str, Any]:
 def suggest_for_ticket(ticket_id: str) -> dict[str, Any]:
     ticket = _fetch_ticket(ticket_id)
     notes = _fetch_notes(ticket_id)
-    history = _fetch_recent_resolved(30)
+    # A Resolved/Closed ticket must not be offered as a "similar past ticket" to itself.
+    history = [t for t in _fetch_recent_resolved(30) if t.get("id") != ticket.get("id")]
 
     if not history:
         return {"matches": [], "note": "No resolved tickets available for comparison."}
diff --git a/backend/test_ai_suggest.py b/backend/test_ai_suggest.py
new file mode 100644
index 0000000..fed1ab2
--- /dev/null
+++ b/backend/test_ai_suggest.py
@@ -0,0 +1,53 @@
+"""Tests for ai.suggest_for_ticket (the real ai module, not the stub used in test_main)."""
+
+import importlib
+import sys
+from unittest.mock import MagicMock
+
+import pytest
+
+
+@pytest.fixture
+def ai(monkeypatch):
+    sys.modules.pop("ai", None)
+    module = importlib.import_module("ai")
+    yield module
+    sys.modules.pop("ai", None)
+
+
+def test_suggest_excludes_the_ticket_itself(ai, monkeypatch):
+    target = {"id": "t1", "title": "Printer jam", "status": "Closed"}
+    other = {"id": "t2", "title": "Paper jam", "status": "Resolved"}
+    monkeypatch.setattr(ai, "_fetch_ticket", lambda _id: target)
+    monkeypatch.setattr(ai, "_fetch_notes", lambda _id: [])
+    monkeypatch.setattr(ai, "_fetch_recent_resolved", lambda limit=30: [dict(target), dict(other)])
+
+    captured = {}
+
+    def fake_build(ticket, notes, history):
+        captured["history"] = history
+        return "prompt"
+
+    monkeypatch.setattr(ai, "_build_prompt", fake_build)
+    client = MagicMock()
+    client.messages.create.return_value = MagicMock(
+        content=[MagicMock(type="text", text='{"matches": []}')]
+    )
+    monkeypatch.setattr(ai, "_get_client", lambda: client)
+
+    ai.suggest_for_ticket("t1")
+
+    assert [t["id"] for t in captured["history"]] == ["t2"]
+
+
+def test_suggest_with_only_itself_in_history_returns_note(ai, monkeypatch):
+    target = {"id": "t1", "title": "Printer jam", "status": "Closed"}
+    monkeypatch.setattr(ai, "_fetch_ticket", lambda _id: target)
+    monkeypatch.setattr(ai, "_fetch_notes", lambda _id: [])
+    monkeypatch.setattr(ai, "_fetch_recent_resolved", lambda limit=30: [dict(target)])
+    monkeypatch.setattr(ai, "_get_client", lambda: pytest.fail("model must not be called"))
+
+    result = ai.suggest_for_ticket("t1")
+
+    assert result["matches"] == []
+    assert "No resolved tickets" in result["note"]