- payments.rs: an expired invoice can never succeed on retry, so the
error now says so and tells the payer the way out (ask the recipient
for a fresh invoice) instead of echoing LND's raw reason.
- middleware.rs: the error sanitizer masked every Lightning payment
failure as 'Operation failed. Check server logs' — but LND's reasons
('invoice expired', 'unable to find a path') are written for the
payer and are all actionable. 'Payment failed', 'Invalid payment
request' and 'Missing payment_request' now pass through, with a
regression test.
Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
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