diff --git a/opencode/decisions.yaml b/opencode/decisions.yaml
index cd17ceb4..5c5d17f5 100644
--- a/opencode/decisions.yaml
+++ b/opencode/decisions.yaml
@@ -431,4 +431,28 @@ notes:
     integrations:
       - tuya
       - matter
+    status: superseded
+    superseded_by: 2026-08-23-enp1s0-ipv6-must-stay-auto-thread-2
+  - id: 2026-08-23-enp1s0-ipv6-must-stay-auto-thread-2
+    date: 2026-08-23
+    title: enp1s0 IPv6 must stay Auto (Thread-Matter needs routed v6)
+    decision: enp1s0 IPv6 stays Auto. Static-no-gateway breaks Thread-Matter (nodes
+      fd25:f6c0:5149::/48 go ENETUNREACH); Auto breaks Tuya while Bell router v6 is
+      broken. Real fix = reboot the router. netfix_ipv6.sh via
+      shell_command.ipv6_static_nogw = quick toggle between modes if ever needed again.
+    rationale: "2026-08-23: Bell GigaHub default v6 route black-holed apigw.tuyaus.com -> Tuya
+      setup cancelled repeatedly. Static-no-gateway fixed Tuya but killed Thread-Matter
+      within minutes (41/90 down). Auto restored all 90 Matter nodes; Tuya failed again ->
+      router still broken. User will reboot it. After reboot verify BOTH tuya loaded AND 0
+      matter unavailable; if still broken, fallback = SSH addon + manual route for
+      fd25:f6c0:5149::/48 only."
+    entities:
+      - light.3d_printer_lights
+    files:
+      - configuration.yaml
+      - netfix_ipv6.sh
+    integrations:
+      - tuya
+      - matter
+    pin: true
     status: active