LND 0.21.2 removed the deprecated Lightning.SendPaymentSync REST route
(/v1/channels/transactions). The backend still called it, so every
Lightning send answered literal HTTP 404 and the wallet UI reported
'Payment failed: Not Found' fleet-wide right after the pin bump —
receive worked, which made it look intermittent.
Pay through the supported Router.SendPaymentV2 route (/v2/router/send)
instead, keeping the existing contract with the UI:
- single-record responses (no_inflight_updates) unwrapped from the
grpc-gateway result envelope, transport errors from the nested error
- a slow multi-hop payment still resolves as pending + payment hash
(only LND may declare failure), never a false 'Payment failed'
- LND's failure_reason codes translated to the same plain-language
advice, invoice-expiry still says 'ask for a fresh invoice'
Guard it at the gate: tests/lifecycle/bats/lnd-api-compat.bats POSTs a
deliberately-invalid invoice to /v2/router/send on the RUNNING LND and
fails if the route answers 404 — the image/backend skew that shipped
silently last time because no test ever spoke the payment endpoint.
Also bumps the stale lnd image expectation in remote-lifecycle.sh.
archipelago
cbd5314dd9