diff --git a/src/controllers/nostr/relay.ts b/src/controllers/nostr/relay.ts
index 1537047..8befa56 100644
--- a/src/controllers/nostr/relay.ts
+++ b/src/controllers/nostr/relay.ts
@@ -15,12 +15,14 @@ import type { Event, Filter } from '@/deps.ts';
 /** Limit of events returned per-filter. */
 const FILTER_LIMIT = 100;
 
+/** NIP-01 relay to client message. */
 type RelayMsg =
   | ['EVENT', string, Event]
   | ['NOTICE', string]
   | ['EOSE', string]
   | ['OK', string, boolean, string];
 
+/** Set up the Websocket connection. */
 function connectStream(socket: WebSocket) {
   socket.onmessage = (e) => {
     const result = jsonSchema.pipe(clientMsgSchema).safeParse(e.data);
@@ -31,6 +33,7 @@ function connectStream(socket: WebSocket) {
     }
   };
 
+  /** Handle client message. */
   function handleMsg(msg: ClientMsg) {
     switch (msg[0]) {
       case 'REQ':
@@ -45,6 +48,7 @@ function connectStream(socket: WebSocket) {
     }
   }
 
+  /** Handle REQ. Start a subscription. */
   async function handleReq([_, sub, ...filters]: ClientREQ) {
     for (const event of await eventsDB.getFilters(prepareFilters(filters))) {
       send(['EVENT', sub, event]);
@@ -52,20 +56,28 @@ function connectStream(socket: WebSocket) {
     send(['EOSE', sub]);
   }
 
+  /** Handle EVENT. Store the event. */
   async function handleEvent([_, event]: ClientEVENT) {
     try {
+      // This will store it (if eligible) and run other side-effects.
       await pipeline.handleEvent(event);
       send(['OK', event.id, true, '']);
-    } catch (_e) {
-      send(['OK', event.id, false, 'blocked: only registered users can post']);
+    } catch (e) {
+      if (e instanceof pipeline.RelayError) {
+        send(['OK', event.id, false, e.message]);
+      } else {
+        send(['OK', event.id, false, 'error: something went wrong']);
+      }
     }
   }
 
+  /** Handle CLOSE. Close the subscription. */
   function handleClose([_, _sub]: ClientCLOSE) {
     // TODO: ???
     return;
   }
 
+  /** Send a message back to the client. */
   function send(msg: RelayMsg) {
     return socket.send(JSON.stringify(msg));
   }
diff --git a/src/pipeline.ts b/src/pipeline.ts
index 00d3eb9..af72b79 100644
--- a/src/pipeline.ts
+++ b/src/pipeline.ts
@@ -12,9 +12,9 @@ import { isRelay, nostrDate } from '@/utils.ts';
  */
 async function handleEvent(event: Event): Promise<void> {
   await Promise.all([
-    trackHashtags(event),
     storeEvent(event),
     trackRelays(event),
+    trackHashtags(event),
   ]);
 }
 
@@ -22,6 +22,8 @@ async function handleEvent(event: Event): Promise<void> {
 async function storeEvent(event: Event): Promise<void> {
   if (await findUser({ pubkey: event.pubkey }) || await isLocallyFollowed(event.pubkey)) {
     await eventsDB.insertEvent(event).catch(console.warn);
+  } else {
+    return Promise.reject(new RelayError('blocked', 'only registered users can post'));
   }
 }
 
@@ -61,4 +63,11 @@ function trackRelays(event: Event) {
   return addRelays([...relays]);
 }
 
-export { handleEvent };
+/** NIP-20 command line result. */
+class RelayError extends Error {
+  constructor(prefix: 'duplicate' | 'pow' | 'blocked' | 'rate-limited' | 'invalid' | 'error', message: string) {
+    super(`${prefix}: ${message}`);
+  }
+}
+
+export { handleEvent, RelayError };