Reject invalid Tailscale discovery JSON (#1556)

* Reject invalid Tailscale discovery JSON

* Guard nested Tailscale IP shapes

tests/test_model_discovery_status.py

@@ -0,0 +1,37 @@
+from src import model_discovery
+
+
+def test_parse_tailscale_status_rejects_wrong_shapes():
+    assert model_discovery._parse_tailscale_status("{bad") == {}
+    assert model_discovery._parse_tailscale_status("[]") == {}
+    assert model_discovery._parse_tailscale_status('{"Self": {}}') == {"Self": {}}
+
+
+def test_discovery_ignores_invalid_peer_rows(monkeypatch):
+    class Result:
+        returncode = 0
+        stdout = '{"Self":{"TailscaleIPs":["100.1.1.1"]},"Peer":{"bad":"row","ok":{"Online":true,"HostName":"box","OS":"linux","TailscaleIPs":["100.1.1.2"]}}}'
+
+    monkeypatch.setattr(model_discovery.subprocess, "run", lambda *a, **k: Result())
+    model_discovery._hosts_cache = []
+    model_discovery._hosts_cache_time = 0
+
+    assert model_discovery.discover_tailscale_hosts() == ["100.1.1.1", "100.1.1.2"]
+
+
+def test_discovery_ignores_invalid_tailscale_ip_shapes(monkeypatch):
+    class Result:
+        returncode = 0
+        stdout = (
+            '{"Self":{"TailscaleIPs":"100.1.1.1"},'
+            '"Peer":{'
+            '"string_ips":{"Online":true,"HostName":"bad","OS":"linux","TailscaleIPs":"100.1.1.2"},'
+            '"mixed_ips":{"Online":true,"HostName":"ok","OS":"linux","TailscaleIPs":[null,123,"100.1.1.3"]}'
+            '}}'
+        )
+
+    monkeypatch.setattr(model_discovery.subprocess, "run", lambda *a, **k: Result())
+    model_discovery._hosts_cache = []
+    model_discovery._hosts_cache_time = 0
+
+    assert model_discovery.discover_tailscale_hosts() == ["100.1.1.3"]