fix: re-sweep and durably invalidate DashPay backfill coverage when contact accounts register after the scan - #1546
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HashEngineering merged 2 commits intoAug 27, 2026
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…register after the scan The SDK's dashPaySyncNow rescan reconcile rewinds the SPV synced height only for the receival accounts that exist at that moment, but the app runs it BEFORE the signer-backed drain that actually registers those accounts. On a restored wallet the first sweep therefore reconciles against zero accounts and backfills nothing, the accounts appear seconds later on a path that never rewinds, and on gate-skip launches the standalone drain registered accounts no sweep ever ran for — historical DashPay contact payments stayed invisible until a manual restart, or forever when the gate's persisted coverage survived a crash. - SdkWalletBinder: a drain (either the sweep pass's own step-2 drain or drainDeferredAccountBuilds on the gate-skip path) whose registrations the gate accepts as NEW now buys AT MOST ONE follow-up sweep in the same provisioning cycle, routed through the gate's own evaluate so the armed-marker bookkeeping stays coherent; a gate that still refuses (e.g. a replay in flight) keeps the debt recorded instead. - DashPayBackfillGate.noteAccountBuildsRegistered now returns whether the registrations were accepted (loop-guard aware) and durably clears any persisted coverage — the same four-key removal the address-window heal uses — BEFORE the follow-up sweep can run, so a process death in between self-heals on the next launch. concludeNoRewindObserved refuses while a registration is outstanding for the same reason. - Dark-contact diagnostics: after every drain, one INFO line reports established contacts vs receival accounts and names up to five contacts with no account (readDashPayReceivalCoverage — pure Room reads in DashSdkServiceImpl). Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
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📝 WalkthroughWalkthroughThe change adds durable registration tracking to the DashPay backfill gate, runs one same-cycle follow-up sweep when new accounts are built, and exposes read-only receival-account coverage diagnostics with dark-contact samples. ChangesDashPay provisioning lifecycle
Estimated code review effort: 3 (Moderate) | ~25 minutes Merge Risk: 🟠 High · up to The PR can still preserve stale backfill coverage when account registration and coverage persistence race, causing restored wallets to miss required historical contact payments after a restart. Merge should be blocked until the state updates are serialized and invalidation failures are reported correctly. Sequence Diagram(s)sequenceDiagram
participant SdkWalletBinder
participant DashPayBackfillGate
participant DashSdkService
participant SDK
SdkWalletBinder->>SDK: Run provisioning sweep
SDK-->>SdkWalletBinder: Return account build report
SdkWalletBinder->>DashPayBackfillGate: Note registered builds
DashPayBackfillGate-->>SdkWalletBinder: Return accepted-registration result
SdkWalletBinder->>DashSdkService: Read receival coverage
DashSdkService-->>SdkWalletBinder: Return coverage diagnostics
SdkWalletBinder->>DashPayBackfillGate: Evaluate follow-up sweep
DashPayBackfillGate-->>SdkWalletBinder: Return run decision
SdkWalletBinder->>SDK: Run one follow-up sweep when permitted
🚥 Pre-merge checks | ✅ 4 | ❌ 1❌ Failed checks (1 warning)
✅ Passed checks (4 passed)
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In `@wallet/src/de/schildbach/wallet/service/platform/sdk/DashPayBackfillGate.kt`:
- Around line 1011-1031: Serialize registration invalidation, coverage writes,
and the accountsRegisteredSincePass check in concludeNoRewindObserved under the
same gate-state mutex, ensuring registration cannot be accepted while conclusion
persists coverage. Make noteAccountBuildsRegistered report success only after
durable coverage invalidation succeeds, and do not return true when invalidation
fails. Add a coroutine barrier test covering registration racing with conclusion
and verifying coverage cannot suppress the required backfill.
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📒 Files selected for processing (7)
wallet/src/de/schildbach/wallet/service/platform/sdk/DashPayBackfillGate.ktwallet/src/de/schildbach/wallet/service/platform/sdk/DashSdkService.ktwallet/src/de/schildbach/wallet/service/platform/sdk/DashSdkServiceImpl.ktwallet/src/de/schildbach/wallet/service/platform/sdk/SdkWalletBinder.ktwallet/test/de/schildbach/wallet/service/platform/sdk/DashPayBackfillGateTest.ktwallet/test/de/schildbach/wallet/service/platform/sdk/DashSdkServiceImplTest.ktwallet/test/de/schildbach/wallet/service/platform/sdk/SdkWalletBinderTest.kt
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… write concludeNoRewindObserved read accountsRegisteredSincePass as clear, then spent a native signal read and a contact-table read reasoning before it wrote coverage. A drain landing in that window raises the signal and finds no coverage to invalidate, so the conclusion records coverage over a scan the just-registered receival accounts' addresses were never watched during. In-process the signal still forces the re-sweep, but a process death right after leaves exactly the stale coverage this gate exists to prevent — permanently suppressing the backfill those accounts are owed. A gate-state mutex now serializes the registration signal against every persisted-coverage mutation: noteAccountBuildsRegistered (flag raise + four-key invalidation as ONE atomic step), evaluate's read/decide/persist (its "backfill COMPLETE" branch writes coverage), recordPassOutcome's outcome writes, and the conclusion's write. It is held over the persistence steps only — never over the SDK read — so a drain never waits on the native layer. The conclusion's tail moves into recordNoRewindCoverage, under the lock and behind a final re-check of both a registration and a latched replay. Either interleaving is then safe: a registration landing before the write is seen by the re-check and the conclusion refuses; one landing after sees the record and clears it. recordPassOutcome deliberately does not re-check the signal (documented in place): the note above it is that pass's own drain, and its coverage branch is reachable only for a settled sweep that built nothing, so re-checking would make it unreachable instead. noteAccountBuildsRegistered still answers true when the durable invalidation throws: that verdict is what buys the same-cycle follow-up sweep, whose evaluate retries the clear through the decision core's registration branch. Answering false would drop the retry and defer the debt to the next launch. The KDoc now states the degraded path explicitly. Tests: two barrier cases over a fake whose signal read parks on a CompletableDeferred — the exact seam the field drain lands in — for a registration and for a latched rewind. Staged red-then-green (with the re-checks neutered: 60 tests completed, 2 failed). Full wallet suite: 1876 tests, 0 failures. Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
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Problem
Restored wallets can permanently miss historical DashPay contact payments. The SDK's rescan reconcile (inside dashPaySyncNow) rewinds the SPV synced height only for the contact receival accounts that exist at that moment — but the app runs it BEFORE the signer-backed drain that actually registers those accounts. On a restored wallet the first sweep reconciles against zero accounts and backfills nothing; the accounts appear seconds later on a path that never rewinds; and on gate-skip launches the standalone drain registered accounts no sweep ever ran for. If the gate's persisted coverage then survived, the backfill those accounts are owed was suppressed on every later launch. Field-verified on a restored device: the gate evaluated 213 contact requests and a full rewind was armed, yet a known contact receive never materialized.
Fix
No SDK/FFI changes; all app-side in the seam services.
Tests
12 targeted tests staged red-then-green (one follow-up per cycle on both paths, none when nothing registers, none when the loop guard mutes, invalidation-lands-before-sweep on both paths, crash-simulation across two gate instances over one store, conclude-refusal, diagnostics reads) — including a rewrite of one pre-existing test whose assertion encoded the bug. Full wallet suite: 1874 tests, 0 failures.
Known residual (documented in code): registrations landing during an in-progress replay watch don't interrupt the watch (its deliberate anti-livelock rule); a crash in that window can still record stale coverage. Making the in-progress marker registration-aware is a follow-up decision.
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Summary by CodeRabbit
New Features
Bug Fixes