feat: add anonymous zap option

Add "Zap anonymously" checkbox that allows users to send zaps without
revealing their identity. When enabled, creates a throwaway keypair to
sign the zap request instead of using the active account's signer.

This also enables users without a signer account to send zaps by
checking the anonymous option.

src/components/ZapWindow.tsx

@@ -21,10 +21,14 @@ import {
   Loader2,
   CheckCircle2,
   LogIn,
+  EyeOff,
 } from "lucide-react";
 import { Button } from "@/components/ui/button";
 import { Input } from "@/components/ui/input";
 import { Label } from "@/components/ui/label";
+import { Checkbox } from "@/components/ui/checkbox";
+import { PrivateKeySigner } from "applesauce-signers";
+import { generateSecretKey } from "nostr-tools";
 import QRCode from "qrcode";
 import { useProfile } from "@/hooks/useProfile";
 import { use$ } from "applesauce-react/hooks";
@@ -138,6 +142,7 @@ export function ZapWindow({
   const [showQrDialog, setShowQrDialog] = useState(false);
   const [showLogin, setShowLogin] = useState(false);
   const [paymentTimedOut, setPaymentTimedOut] = useState(false);
+  const [zapAnonymously, setZapAnonymously] = useState(false);
 
   // Editor ref and search functions
   const editorRef = useRef<MentionEditorHandle>(null);
@@ -356,6 +361,13 @@ export function ZapWindow({
       }
 
       // Step 3: Create and sign zap request event (kind 9734)
+      // If zapping anonymously, create a throwaway signer
+      let anonymousSigner;
+      if (zapAnonymously) {
+        const throwawayKey = generateSecretKey();
+        anonymousSigner = new PrivateKeySigner(throwawayKey);
+      }
+
       const zapRequest = await createZapRequest({
         recipientPubkey,
         amountMillisats,
@@ -366,6 +378,7 @@ export function ZapWindow({
         lnurl: lud16 || undefined,
         emojiTags,
         customTags,
+        signer: anonymousSigner,
       });
 
       const serializedZapRequest = serializeZapRequest(zapRequest);
@@ -657,6 +670,26 @@ export function ZapWindow({
                     className="rounded-md border border-input bg-background px-3 py-1 text-base md:text-sm min-h-9"
                   />
                 )}
+
+                {/* Anonymous zap checkbox */}
+                {hasLightningAddress && (
+                  <div className="flex items-center gap-2">
+                    <Checkbox
+                      id="zap-anonymously"
+                      checked={zapAnonymously}
+                      onCheckedChange={(checked) =>
+                        setZapAnonymously(checked === true)
+                      }
+                    />
+                    <label
+                      htmlFor="zap-anonymously"
+                      className="text-sm text-muted-foreground cursor-pointer flex items-center gap-1.5"
+                    >
+                      <EyeOff className="size-3.5" />
+                      Zap anonymously
+                    </label>
+                  </div>
+                )}
               </div>
 
               {/* No Lightning Address Warning */}
@@ -667,7 +700,7 @@ export function ZapWindow({
               )}
 
               {/* Payment Button */}
-              {!canSign ? (
+              {!canSign && !zapAnonymously ? (
                 <Button
                   onClick={handleLogin}
                   className="w-full"
@@ -713,6 +746,12 @@ export function ZapWindow({
                       Pay with Wallet (
                       {selectedAmount || parseInt(customAmount) || 0} sats)
                     </>
+                  ) : zapAnonymously ? (
+                    <>
+                      <EyeOff className="size-4 mr-2" />
+                      Zap Anonymously (
+                      {selectedAmount || parseInt(customAmount) || 0} sats)
+                    </>
                   ) : (
                     <>
                       <Zap className="size-4 mr-2" />

src/lib/create-zap-request.ts

@@ -3,11 +3,11 @@
  */
 
 import { EventFactory } from "applesauce-core/event-factory";
+import type { ISigner } from "applesauce-signers";
 import type { NostrEvent } from "@/types/nostr";
 import type { EventPointer, AddressPointer } from "./open-parser";
 import accountManager from "@/services/accounts";
-import { relayListCache } from "@/services/relay-list-cache";
-import { AGGREGATOR_RELAYS } from "@/services/loaders";
+import { selectZapRelays } from "./zap-relay-selection";
 
 export interface EmojiTag {
   shortcode: string;
@@ -36,75 +36,50 @@ export interface ZapRequestParams {
    * Used for additional protocol-specific tagging
    */
   customTags?: string[][];
+  /** Optional signer for anonymous zaps (overrides account signer) */
+  signer?: ISigner;
 }
 
 /**
  * Create and sign a zap request event (kind 9734)
  * This event is NOT published to relays - it's sent to the LNURL callback
+ *
+ * @param params.signer - Optional signer for anonymous zaps. When provided,
+ *                        uses this signer instead of the active account's signer.
  */
 export async function createZapRequest(
   params: ZapRequestParams,
 ): Promise<NostrEvent> {
-  const account = accountManager.active;
+  // Use provided signer (for anonymous zaps) or fall back to account signer
+  let signer = params.signer;
+  let senderPubkey: string | undefined;
 
-  if (!account) {
-    throw new Error("No active account. Please log in to send zaps.");
-  }
+  if (signer) {
+    // Anonymous zap - use provided signer
+    senderPubkey = await signer.getPublicKey();
+  } else {
+    // Normal zap - use account signer
+    const account = accountManager.active;
 
-  const signer = account.signer;
-  if (!signer) {
-    throw new Error("No signer available for active account");
+    if (!account) {
+      throw new Error("No active account. Please log in to send zaps.");
+    }
+
+    signer = account.signer;
+    if (!signer) {
+      throw new Error("No signer available for active account");
+    }
+    senderPubkey = account.pubkey;
   }
 
   // Get relays for zap receipt publication
-  // Priority: explicit params.relays > semantic author relays > sender read relays > aggregators
-  let relays: string[] | undefined = params.relays
-    ? [...new Set(params.relays)] // Deduplicate explicit relays
-    : undefined;
-
-  if (!relays || relays.length === 0) {
-    const collectedRelays: string[] = [];
-
-    // Collect outbox relays from semantic authors (event author and/or addressable event pubkey)
-    const authorsToQuery: string[] = [];
-    if (params.eventPointer?.author) {
-      authorsToQuery.push(params.eventPointer.author);
-    }
-    if (params.addressPointer?.pubkey) {
-      authorsToQuery.push(params.addressPointer.pubkey);
-    }
-
-    // Deduplicate authors
-    const uniqueAuthors = [...new Set(authorsToQuery)];
-
-    // Fetch outbox relays for each author
-    for (const authorPubkey of uniqueAuthors) {
-      const authorOutboxes =
-        (await relayListCache.getOutboxRelays(authorPubkey)) || [];
-      collectedRelays.push(...authorOutboxes);
-    }
-
-    // Include relay hints from pointers
-    if (params.eventPointer?.relays) {
-      collectedRelays.push(...params.eventPointer.relays);
-    }
-    if (params.addressPointer?.relays) {
-      collectedRelays.push(...params.addressPointer.relays);
-    }
-
-    // Deduplicate collected relays
-    const uniqueRelays = [...new Set(collectedRelays)];
-
-    if (uniqueRelays.length > 0) {
-      relays = uniqueRelays;
-    } else {
-      // Fallback to sender's read relays (where they want to receive zap receipts)
-      const senderReadRelays =
-        (await relayListCache.getInboxRelays(account.pubkey)) || [];
-      relays =
-        senderReadRelays.length > 0 ? senderReadRelays : AGGREGATOR_RELAYS;
-    }
-  }
+  // Priority: explicit relays > recipient's inbox > sender's inbox > fallback aggregators
+  const zapRelayResult = await selectZapRelays({
+    recipientPubkey: params.recipientPubkey,
+    senderPubkey,
+    explicitRelays: params.relays,
+  });
+  const relays = zapRelayResult.relays;
 
   // Build tags
   const tags: string[][] = [