fix lnurl description_hash mismatch when sender provides a comment

The bolt11 description_hash is computed from the metadata JSON, which
was being constructed with the sender's `comment` substituted into
text/plain. Wallets verify description_hash against the metadata they
received in the lnurl-pay response, so injecting the comment into the
hash made the verification fail — the invoice would settle but
description_hash verification would reject it as inconsistent.

Keep metadata canonical ("Paying user@host") so the description_hash
the wallet receives matches what they verify against. The comment is
still preserved as the human-readable memo on the invoice record.

Co-Authored-By: Claude Opus 4.7 (1M context) <[email protected]>

1 files changed, 6 insertions, 2 deletions

diff --git a/routes/lnurl.ts b/routes/lnurl.ts
index f4357ff2..6b4e5deb 100644
--- a/routes/lnurl.ts
+++ b/routes/lnurl.ts
@@ -97,9 +97,8 @@ export default {
       let { username } = user;
       username = username.replace(/\s/g, "").toLowerCase();
 
-      const memo = comment ?? `Paying ${username}@${host}`;
       let metadata = JSON.stringify([
-        ["text/plain", memo],
+        ["text/plain", `Paying ${username}@${host}`],
         ["text/identifier", `${username}@${host}`],
       ]);
 
@@ -124,6 +123,11 @@ export default {
             user,
           });
 
+      if (comment) {
+        invoice.memo = comment;
+        await s(`invoice:${invoice.id}`, invoice);
+      }
+
       return c.json({
         pr: invoice.text,
         routes: [],