diff --git a/bitspire.py b/bitspire.py
index 9e0c70c..1609052 100644
--- a/bitspire.py
+++ b/bitspire.py
@@ -126,6 +126,14 @@ def assert_nostr_attribution(machine: Machine, extra: dict) -> None:
             "missing nostr_sender_pubkey on Payment.extra — invoice was not "
             "issued through the nostr-transport path"
         )
+    if not machine.machine_npub:
+        # Unpaired machine (machine_npub None — nullable since #29/m011). It has
+        # no identity to attribute a settlement to; reject cleanly rather than
+        # let normalize_public_key(None) raise an uncaught AttributeError.
+        raise SettlementAttributionError(
+            f"machine {machine.id} is unpaired (no machine_npub); "
+            "a settlement cannot be attributed to it"
+        )
     from lnbits.utils.nostr import normalize_public_key
 
     try:
diff --git a/cassette_transport.py b/cassette_transport.py
index 9f60d9a..e6517a1 100644
--- a/cassette_transport.py
+++ b/cassette_transport.py
@@ -141,8 +141,10 @@ def _state_d_tag(atm_pubkey_hex: str) -> str:
 
 def build_state_d_tags_for_machines(machines: list[Machine]) -> list[str]:
     """Bootstrap-consumer subscription filter helper: returns the full
-    `#d=[...]` list for all known ATMs an operator subscribes to."""
-    return [_state_d_tag(_atm_hex_pubkey(m)) for m in machines]
+    `#d=[...]` list for all known PAIRED ATMs an operator subscribes to.
+    Unpaired machines (machine_npub is None — nullable since #29/m011) have no
+    state-beacon d-tag yet, so skip them rather than crash `_atm_hex_pubkey`."""
+    return [_state_d_tag(_atm_hex_pubkey(m)) for m in machines if m.machine_npub]
 
 
 # =============================================================================
diff --git a/crud.py b/crud.py
index 6c4ef53..6eda100 100644
--- a/crud.py
+++ b/crud.py
@@ -180,6 +180,11 @@ async def get_machine_by_atm_pubkey_hex(atm_pubkey_hex: str) -> Machine | None:
     target = atm_pubkey_hex.lower()
     machines = await list_all_active_machines()
     for m in machines:
+        # Unpaired machines (machine_npub is None — nullable since #29/m011)
+        # have no identity to match and would raise AttributeError in
+        # normalize_public_key (not caught below); skip them.
+        if not m.machine_npub:
+            continue
         try:
             if normalize_public_key(m.machine_npub).lower() == target:
                 return m
diff --git a/views_api.py b/views_api.py
index 1a5bc62..35d35b2 100644
--- a/views_api.py
+++ b/views_api.py
@@ -1081,6 +1081,12 @@ async def api_update_super_config(
     )
     if super_fractions_changed:
         for machine in await list_all_active_machines():
+            # Unpaired machines (machine_npub is None — nullable since #29/m011)
+            # have no Nostr identity to publish a fee-config beacon to. Skip
+            # them; they pick up the current fee config when they pair
+            # (api_pair_machine publishes on success).
+            if not machine.machine_npub:
+                continue
             await publish_fee_config(machine, config, machine.operator_user_id)
     return config
 
@@ -1147,6 +1153,14 @@ async def api_publish_machine_cassettes(
       500 — anything else from the publish path
     """
     machine = await _machine_owned_by(machine_id, user.id)
+    if not machine.machine_npub:
+        # Unpaired machine (machine_npub None — nullable since #29/m011) has no
+        # ATM identity to publish a cassette config to. Fail fast with a clean
+        # 400 instead of crashing publish_to_atm's normalize_public_key(None).
+        raise HTTPException(
+            HTTPStatus.BAD_REQUEST,
+            "machine is not paired — pair it before publishing cassette config",
+        )
 
     existing = await list_cassette_configs_for_machine(machine_id)
     existing_positions = {row.position for row in existing}