diff --git a/docs/decisions/012-hardware-capacity.md b/docs/decisions/012-hardware-capacity.md
index 9da12c0..c1e0bfb 100644
--- a/docs/decisions/012-hardware-capacity.md
+++ b/docs/decisions/012-hardware-capacity.md
@@ -13,6 +13,8 @@ workload that should move, or a node due an upgrade.
 - `docs/hardware/reference.md` is the single, hand-maintained source of truth for
   physical compute + network gear and workload placement intent. Two
   machine-readable tables (node capacity, workload placement) carry the numbers.
+  This includes `ubongo`, the physical control node (ADR-015), even though it sits
+  outside the Proxmox cluster.
 - `scripts/capacity-scan.py` (stdlib-only, like `repo-scan.py` / `tf_to_inventory.py`)
   parses those tables, computes per-node allocated-vs-physical rollups, and
   cross-checks workload hostnames against `terraform output -json` /
diff --git a/docs/hardware/reference.md b/docs/hardware/reference.md
index bd6a65a..8098ebf 100644
--- a/docs/hardware/reference.md
+++ b/docs/hardware/reference.md
@@ -18,6 +18,14 @@
 - **NICs:** _eno1 trunk (vmbr0), eno2 corosync (vmbr1)_
 - **Notes:** _warranty, quirks_
 
+### ubongo (control node — outside the cluster)
+- **Model / form factor:** _TBD (x86-64 mini-PC / USFF, e.g. N100 or refurb micro)_
+- **CPU:** _TBD (target 4 cores, x86-64)_
+- **RAM:** _TBD (target 16 GB)_
+- **Storage:** _TBD (target 250 GB SSD/NVMe)_
+- **NICs:** _wired GbE_
+- **Notes:** _always-on; control plane + AI-worker + local test runner (ADR-015); not a Proxmox guest_
+
 _(repeat for pve1, pve2, askari)_
 
 ## 2. Network gear
@@ -46,6 +54,7 @@ Physical totals per node. Integers; `ram_gb` and `disk_gb` may be decimals.
 |------|-------|--------|---------|
 | pve0 | 20    | 64     | 4000    |
 | pve1 | 20    | 64     | 4000    |
+| ubongo | 4   | 16     | 250     |
 
 ## 5. Capacity notes