Lightning login (LNURL-auth): a site's login lnurl in Send logs you in instead of trying to pay it. A community member pasted Stacker News's lightning-login lnurl into Send and got "stacker.news: no sig query variable provided" (2026-10-16): every lnurl1 was taken for LNURL-pay, their login endpoint was fetched as if for pay parameters, and its refusal came back as the error. Now an lnurl whose URL carries tag=login and a 32-byte k1 (parseLnurlAuth; lightning: prefix and upper case fine; action register|login|link|auth) is a login: the wallet asks first — the site's name, what it is asking (log in / create an account / link / confirm it's you), that the challenge is signed with a key kept for this site alone and that nothing is paid or shared — then signs k1 (ECDSA, DER) with the LUD-05 linking key (m/138'/0 as hashing key, HMAC-SHA256 of the domain read as four 32-bit child indexes under m/138'; the same wallet is the same user on a site every time and a different one elsewhere; from the mnemonic, or an imported xprv) and calls back with sig and key (lnurlAuthKey, lnurlAuthLogin). The site's OK shows "Logged in to <site>", its reason otherwise, with Try again and Back. It takes no balance (checked before canPay in zaps' matchSendText), so it works on an empty wallet and from an Android lightning: intent. tools/lnurl-auth-unit-test.js (login vs pay vs bad k1; one key per site per wallet; the DER signature verifies under the key sent; the server's reason is the error) and tools/lnurl-auth-test.js (a stand-in site that verifies the signature: the ask, nothing sent before Log in, OK, the same key next time, a register link, a refusal's words); send-dest-test passes.

Co-Authored-By: Claude Fable 5.1 <[email protected]>
Claude-Session: https://claude.ai/code/session_01J1Kon8bxJoHRpJdSzshCkp

1 files changed, 14 insertions, 0 deletions

diff --git a/src/i18n.js b/src/i18n.js
index 278d136..4cccefd 100644
--- a/src/i18n.js
+++ b/src/i18n.js
@@ -1477,6 +1477,20 @@ const STR = {
     destPlaceholder: 'Address or Lightning invoice',
     lnQuoting: 'Getting a quote…',
     lnPayTitle: 'Pay over Lightning',
+    lnAuthTitle: 'Log in with Lightning',
+    lnAuthAskLogin: '{domain} is asking you to log in with your wallet.',
+    lnAuthAskRegister: '{domain} is asking you to create an account with your wallet.',
+    lnAuthAskLink: '{domain} is asking to link your wallet to your account there.',
+    lnAuthAskAuth: '{domain} is asking you to confirm it’s you, with your wallet.',
+    lnAuthHow: 'Your wallet signs their challenge with a key it keeps for this site alone. No payment is made, and nothing else about you is shared.',
+    lnAuthGo: 'Log in',
+    lnAuthGoRegister: 'Create account',
+    lnAuthRetry: 'Try again',
+    lnAuthSigning: 'Signing in to {domain}…',
+    lnAuthDoneTitle: 'Logged in to {domain}',
+    lnAuthDoneHint: 'Go back to their page — it should have let you in.',
+    lnAuthFailed: 'They didn’t accept the login.',
+    lnAuthNoKey: 'This account has no wallet key to log in with.',
     lnPayAmount: 'Amount',
     lnPayBoltzFee: 'Swap fee',
     lnPayNetworkFee: 'Network fee',