fix(spv): atomically extend BIP44 receive pool on wallet import

[lklimek]

Summary

Fixes the second of the four layers behind the zero-balance-on-import bug tracked in #829: addresses generated via the UI beyond the WalletManager's default BIP44 gap limit (30) are not re-registered into the live monitored set on startup, so SPV filter matching misses any UTXO at those higher indices.

This PR is now narrowly focused on the bug-2 fix only. The platform pin bump and clear_data_dir fix have been extracted into #834 and must land first.

Reproduction

1. In an existing wallet, use the UI to generate 35+ receive addresses (indices 0–34).
2. Restart DET.
3. Send a testnet transaction to the address at an index ≥ 30 (beyond the WalletManager default gap limit).
4. Wait for the transaction to confirm, then observe the wallet balance in the UI.

Expected: The balance at the receiving address appears, because the WalletManager's monitored address set should include every index that exists in DET's local database.

Actual: The address shows zero balance. On restart, the WalletManager is reconstructed with WalletAccountCreationOptions::Default which pre-generates BIP44 indices 0–29 only. Any indices DET previously stored in wallet_addresses beyond 29 are never re-registered into the WalletManager, so the live monitored address set is narrower than DET's on-disk state. SPV filter matching misses any UTXO at indices ≥ 30.

Observed with a reference testnet wallet that has a multi-output transaction at BIP44 indices 0 and 32–40 (motivating tx: 56bdab0ac5dfefc47e136eedeede07a83ff0f2cb753683578fd41677975f8b32 in block 1,459,352). Only index 0 shows balance; 32–40 do not.

Root cause

Upstream's BIP44 gap-limit reactive extension works as designed: if at least one address within the current gap is observed, the pool extends. But DET stores more addresses in its local DB than it restores to the live monitored set on startup, and there's no code path that reconciles the two.

There's also a second, subtler race: earlier drafts extended the pool after load_wallet_from_seed returned, meaning wm.wallet_count() could cross the threshold that run_spv_loop waits on while the pool was still at its default size — SPV's filter pipeline then started matching against an incomplete set.

Fix

extend_bip44_receive_pool_locked runs inside the WalletManager write lock held by load_wallet_from_seed. wm.wallet_count() does not increment until the pool is final, closing the race. The extension target is max_db_idx (the highest BIP44 receive index present in the wallet_addresses DB table), plus a small slack (LOOKAHEAD_SLACK = 100).

Supporting helpers

• Database::max_bip44_receive_index() — reads the DB's wallet_addresses table for the highest receive index known for a given wallet.
• SpvManager::extend_bip44_receive_pool_locked — called under the existing write lock; iterates get_receive_address(wallet_id, i, BIP44, mark_used=true) up to max_db_idx + LOOKAHEAD_SLACK. Uses upstream's existing gap-limit reactive extension without adding new API surface.

Files

File	Lines	Purpose
src/context/wallet_lifecycle.rs	+35	Pool extension plumbing inside load_wallet_from_seed's write lock
src/database/wallet.rs	+125	Database::max_bip44_receive_index helper + 3 unit tests
src/spv/manager.rs	+95	SpvManager::extend_bip44_receive_pool_locked

Total: +253 / -2 lines. Single commit.

Test plan

Automated (all green)

• cargo build --all-features — clean
• cargo clippy --all-features --all-targets -- -D warnings — clean
• cargo +nightly fmt --all -- --check — clean
• cargo test --all-features --workspace --lib — 455 / 455 pass

Manual on testnet

• Cold start with existing wallet containing indices ≥ 30. Launch DET against a DB that already has addresses generated up to e.g. index 40. Expected: on first sync, balance on indices ≥ 30 appears without manual clear-and-resync. Log contains Extended SPV BIP44 receive pool wallet=… generated=<N> target_index=<max_db_idx>.
• Fresh install regression. rm -rf ~/.config/dash-evo-tool/data.db ~/.config/dash-evo-tool/spv/ → launch → fresh wallet with no historical UTXOs. Expected: no crash, standard checkpoint sync, balance = 0.

What this PR does not carry

• Platform bump & clear_data_dir fix — moved to #834 for focused review. That PR must land first (this branch is otherwise cleanly independent but relies on the bumped platform for its build).
• Bug 1 (startup init-order race) — #833.
• Bug 3 (mid-session import rescan workaround) — previously on this branch; stripped because it's blocked upstream by rust-dashcore#651 constraint #4. Preserved on archive/spv-wallet-address-sync-2026-04-20 for future reference. Until upstream fix(fees): consolidate Core and Platform fee estimation #651 lands, the sanctioned workaround for mid-session imports is "Clear SPV Data".

Merge order

1. #834 (platform bump + clear_data_dir fix)
2. #833 (bug 1 startup race — independent, can land first or alongside)
3. This PR (bug 2 pool extension)

Related

• Issue: #829 — four-layer root cause.
• Sibling PR: #834 — platform bump + clear_data_dir fix.
• Sibling PR: #833 — bug 1 startup init-order race.
• Upstream: rust-dashcore#651 — tracks bugs 3 & 4.
• Archive: archive/spv-wallet-address-sync-2026-04-20 — preserved pre-strip state.

_{🤖 Co-authored by Claudius the Magnificent AI Agent}

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