diff --git a/nostr_publisher.py b/nostr_publisher.py
index 677d96f..0e5b4c4 100644
--- a/nostr_publisher.py
+++ b/nostr_publisher.py
@@ -46,7 +46,7 @@ def build_nip52_event(event: Event, pubkey: str) -> NostrEvent:
       start              - unix timestamp (31923) or YYYY-MM-DD (31922)
       end                - same encoding (optional)
       image, location, t (categories) - optional
-      tickets_available     - current remaining capacity (omitted when unlimited)
+      tickets_available     - current remaining capacity (always emitted; 0 = sold out)
       tickets_sold          - running paid-count (always emitted; clients can
                               derive original_capacity = available + sold)
       tickets_price         - price_per_ticket (always emitted; 0 means free)
@@ -96,11 +96,14 @@ def build_nip52_event(event: Event, pubkey: str) -> NostrEvent:
     for cat in event.categories or []:
         tags.append(["t", cat])
 
-    # `amount_tickets == 0` means unlimited capacity in this extension's
-    # schema. Omitting the tag is how clients distinguish unlimited from
-    # "0 left" (sold out).
-    if event.amount_tickets > 0:
-        tags.append(["tickets_available", str(event.amount_tickets)])
+    # Always emitted, including zero. Omitting it used to mean "unlimited",
+    # which contradicted every other reader: `api_get_event` and
+    # `api_ticket_create` both treat `amount_tickets < 1` as sold out, so a
+    # zero-capacity event advertised "Unlimited tickets" on the card while
+    # the detail page and the purchase both returned 410 (aiolabs/events#34).
+    # Clients that must still handle an absent tag — a NIP-52 event from
+    # some other publisher — are unaffected; we simply never omit it.
+    tags.append(["tickets_available", str(event.amount_tickets)])
     tags.append(["tickets_sold", str(event.sold)])
     tags.append(["tickets_price", str(event.price_per_ticket)])
     tags.append(["tickets_currency", event.currency])
diff --git a/static/js/index.vue b/static/js/index.vue
index d53f4c8..fc7db77 100644
--- a/static/js/index.vue
+++ b/static/js/index.vue
@@ -614,9 +614,9 @@
                 dense
                 v-model.number="formDialog.data.amount_tickets"
                 type="number"
-                min="0"
+                min="1"
                 label="Amount of tickets"
-                hint="0 = unlimited"
+                hint="Total tickets on sale"
               ></q-input>
             </div>
             <div class="col">
diff --git a/tests/test_publish_availability.py b/tests/test_publish_availability.py
new file mode 100644
index 0000000..0ef88a5
--- /dev/null
+++ b/tests/test_publish_availability.py
@@ -0,0 +1,56 @@
+"""`tickets_available` is always published, including zero (#34).
+
+Omitting the tag used to mean "unlimited", which contradicted every other
+reader: `api_get_event` and `api_ticket_create` both treat
+`amount_tickets < 1` as sold out. On aio-demo three zero-capacity events
+advertised "Unlimited tickets" on the card while the detail endpoint and
+the purchase both returned 410.
+"""
+
+from datetime import datetime, timezone
+
+import pytest
+
+from ..models import Event
+from ..nostr_publisher import build_nip52_event
+
+PUBKEY = "a" * 64
+
+
+def _event(amount_tickets: int, sold: int = 0) -> Event:
+    return Event(
+        id="evt",
+        wallet="w",
+        name="Availability",
+        info="",
+        closing_date="2030-01-01",
+        event_start_date="2030-01-01T18:00",
+        event_end_date="2030-01-01T22:00",
+        currency="sat",
+        price_per_ticket=0,
+        amount_tickets=amount_tickets,
+        sold=sold,
+        time=datetime.now(timezone.utc),
+        status="approved",
+    )
+
+
+def _tags(event: Event) -> dict[str, str]:
+    return {t[0]: t[1] for t in build_nip52_event(event, PUBKEY).tags if len(t) > 1}
+
+
+@pytest.mark.parametrize("amount", [0, 1, 50])
+def test_tickets_available_is_always_present(amount):
+    assert _tags(_event(amount))["tickets_available"] == str(amount)
+
+
+def test_zero_capacity_reads_as_sold_out_not_unlimited():
+    """The regression: an absent tag is what clients render as unlimited."""
+    tags = _tags(_event(0, sold=0))
+    assert "tickets_available" in tags
+    assert tags["tickets_available"] == "0"
+
+
+def test_sold_out_after_selling_through_still_publishes_zero():
+    assert _tags(_event(0, sold=25))["tickets_available"] == "0"
+    assert _tags(_event(0, sold=25))["tickets_sold"] == "25"