diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index e15a651..c048c1d 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -71,3 +71,5 @@ jobs:
         # Wiring all of that up is tracked separately.
         mix test.turn
         mix test.nat
+        # Snapcraft recipe contract (unpinned libc6 / USN rebuilds); no anvil.
+        DIODE_MINIMAL_TEST=1 mix test --no-start test/snap/snapcraft_test.exs
diff --git a/snap/snapcraft.yaml b/snap/snapcraft.yaml
index 339e4b8..6b9c4f2 100644
--- a/snap/snapcraft.yaml
+++ b/snap/snapcraft.yaml
@@ -56,6 +56,8 @@ parts:
       # WireGuardNat (MASQUERADE/FORWARD) calls iptables + `ip route`; firewall-control plug required at runtime.
       - iptables
       - iproute2
+      # Unpinned: Snapcraft stages the Ubuntu archive libc used at build time.
+      # Rebuilds pick up USNs (e.g. USN-8737-2 / libc6 2.39-0ubuntu8.9); do not pin.
       - libc6
       - libncurses6
       - libsigsegv2
diff --git a/test/snap/snapcraft_test.exs b/test/snap/snapcraft_test.exs
new file mode 100644
index 0000000..46c8e58
--- /dev/null
+++ b/test/snap/snapcraft_test.exs
@@ -0,0 +1,58 @@
+# Diode Server
+# Copyright 2021-2024 Diode
+# Licensed under the Diode License, Version 1.1
+
+# Snap Store USN scans (e.g. USN-8737-2) are resolved by rebuilding when
+# libc6 is staged from the Ubuntu archive without a version pin.
+defmodule Snap.SnapcraftTest do
+  use ExUnit.Case, async: true
+
+  @snapcraft Path.expand("../../snap/snapcraft.yaml", __DIR__)
+
+  setup_all do
+    {:ok, yaml: File.read!(@snapcraft)}
+  end
+
+  test "uses core24 so staged debs come from Ubuntu 24.04 (noble)", %{yaml: yaml} do
+    assert yaml =~ ~r/^base:\s*core24\s*$/m
+  end
+
+  test "does not pin apt sources that would freeze libc6 away from USNs", %{yaml: yaml} do
+    refute yaml =~ ~r/^package-repositories:/m
+  end
+
+  test "libc6 is listed unpinned in build-packages and stage-packages", %{yaml: yaml} do
+    for section <- ["build-packages", "stage-packages"] do
+      packages = listed_packages(yaml, section)
+      libc6 = Enum.filter(packages, &String.starts_with?(&1, "libc6"))
+
+      assert libc6 == ["libc6"],
+             "#{section} must list unpinned libc6 so a snap rebuild pulls archive security updates (USN-8737-2); got: #{inspect(libc6)}"
+    end
+  end
+
+  defp listed_packages(yaml, section) do
+    lines = String.split(yaml, "\n")
+
+    start =
+      Enum.find_index(lines, fn line ->
+        String.match?(line, ~r/^\s{2,4}#{Regex.escape(section)}:\s*$/)
+      end)
+
+    assert is_integer(start), "missing #{section} in snap/snapcraft.yaml"
+
+    lines
+    |> Enum.drop(start + 1)
+    |> Enum.take_while(&list_continuation?/1)
+    |> Enum.flat_map(fn line ->
+      case Regex.run(~r/^\s+-\s+(\S+)\s*$/, line) do
+        [_, pkg] -> [pkg]
+        _ -> []
+      end
+    end)
+  end
+
+  defp list_continuation?(line) do
+    String.match?(line, ~r/^\s*(?:#|$|- )/)
+  end
+end