diff --git a/deploy/nixos/bitspire-atm.nix b/deploy/nixos/bitspire-atm.nix
index 51daf42..43f4d3c 100644
--- a/deploy/nixos/bitspire-atm.nix
+++ b/deploy/nixos/bitspire-atm.nix
@@ -21,7 +21,18 @@ in
     relayUrl = mkOption {
       type = types.str;
       default = "wss://relay.aiolabs.dev";
-      description = "Nostr relay URL the ATM and LNbits both subscribe to";
+      description = ''
+        Nostr relay URL the ATM and LNbits both subscribe to.
+
+        On a fresh-boot disk image this value is seeded into
+        `/var/lib/bitspire/.env` as `VITE_RELAY_URL=…` (see flake.nix
+        `bitspire-env` activation script). The operator can override
+        the seeded value at runtime by editing `.env` directly or by
+        re-running `deploy/nixos/provision-atm.sh` with a different
+        `RELAY_URL`. The renderer's resolution order is:
+        `/var/lib/bitspire/.env` → this NixOS default → renderer
+        hardcoded fallback (`ws://localhost:7777`).
+      '';
     };
 
     lnbitsServerPubkey = mkOption {
diff --git a/flake.nix b/flake.nix
index 720c167..dc69891 100644
--- a/flake.nix
+++ b/flake.nix
@@ -186,14 +186,19 @@
               };
 
               # Env template — runtime secrets provisioned via provision-atm.sh.
-              # Fields are intentionally empty so a fresh disk image boots
-              # cleanly into the "needs provisioning" state; provision-atm.sh
-              # SSHes in and overwrites with real values.
+              # Identity fields are intentionally empty so a fresh disk image
+              # boots cleanly into the "needs provisioning" state; provision-
+              # atm.sh SSHes in and overwrites with real values.
+              #
+              # VITE_RELAY_URL seeds from `config.services.bitspire.relayUrl`
+              # so the NixOS module's `relayUrl` option becomes the default
+              # without losing the operator's ability to override via .env
+              # (edit the file or re-run provision-atm.sh).
               system.activationScripts.bitspire-env = ''
                 mkdir -p /var/lib/bitspire
                 if [ ! -f /var/lib/bitspire/.env ]; then
                   cp ${pkgs.writeText "bitspire-env-default" ''
-                    VITE_RELAY_URL=
+                    VITE_RELAY_URL=${config.services.bitspire.relayUrl}
                     VITE_LNBITS_SERVER_PUBKEY=
                     VITE_ATM_PRIVATE_KEY=
                     VITE_APP_ID=