Before arming a deep walk on a native-ingester platform (Patreon — where
verify is one cheap API page), POST /sources/{id}/backfill {start|recover}
runs the shared verify_source_credential first and REFUSES (409 + reason)
only on a definitive rejection (verify→False, e.g. expired cookies). It
proceeds on valid (True) or inconclusive (None — a network blip must not
block). Gated to native platforms: gallery-dl verify is a slow --simulate
subprocess, too heavy for an arm action. The credential read happens in a
session that's CLOSED before the verify network call (no held conn).
Frontend: onBackfill/onRecover now read e.body.detail (ApiError carries the
reason in .body, not .detail) so the rejection text surfaces in the toast.
Tests: arm blocked on rejection (409, source not armed), proceeds on
inconclusive, stop never pre-flights, gallery-dl platform skips pre-flight.
An autouse fixture stubs verify to 'valid' for the existing backfill
endpoint tests so they stay network-free.
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
bvandeusen
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