diff --git a/.github/dependabot.yml b/.github/dependabot.yml
new file mode 100644
index 0000000..e2909b5
--- /dev/null
+++ b/.github/dependabot.yml
@@ -0,0 +1,20 @@
+version: 2
+updates:
+  - package-ecosystem: docker
+    directory: "/"
+    schedule:
+      interval: weekly
+      day: monday
+      time: "06:00"
+      timezone: Europe/Vienna
+    open-pull-requests-limit: 2
+    labels: ["dependencies"]
+  - package-ecosystem: github-actions
+    directory: "/"
+    schedule:
+      interval: weekly
+      day: monday
+      time: "06:00"
+      timezone: Europe/Vienna
+    open-pull-requests-limit: 2
+    labels: ["dependencies"]
diff --git a/README.md b/README.md
index 5bb0773..843765b 100644
--- a/README.md
+++ b/README.md
@@ -4,6 +4,8 @@
 
 **Status: public source-only alpha (research preview). Not audited or production-ready.**
 
+**Platform:** Linux **x86_64/amd64 only** for this source build. The pinned Mullvad upgrade binary is compiled for amd64; ARM64 support is not implemented or tested. The Fedora base image is pinned by digest, but distribution RPM dependencies are resolved at build time and are not yet reproducibly locked. Build results can change when package repositories change.
+
 This repository contains the standalone KEMHarbor gateway source and usage documentation. The distributed source tree does not include test harnesses, experimental lifecycle supervisors or an automated container-image release workflow.
 
 ## Gateway characteristics
diff --git a/SECURITY.md b/SECURITY.md
index a2868ac..9657ebd 100644
--- a/SECURITY.md
+++ b/SECURITY.md
@@ -3,6 +3,10 @@
 **Status: research preview; no formal security audit and no production-ready release.**
 This source distribution does not include test harnesses or an automated image-release pipeline. Its documented safety properties are not a substitute for independent security review and live validation.
 
+## Platform and dependency boundaries
+
+This experimental build targets Linux **x86_64/amd64**. Its upstream Mullvad PQ upgrade executable is downloaded for amd64 only; do not use the resulting image on ARM64. The base OCI image is pinned by digest but RPM dependency versions are not locked. An image built at a later date therefore requires fresh testing and security review; digest pinning alone does not provide ongoing security updates.
+
 ## Isolation and capabilities
 
 - Run the VPN inside a dedicated Linux network namespace. **Never** use host networking or privileged mode.