fix(migrate): require a reorg-safe sweep depth + re-verify before adopt; make the wallet.dat swap crash-safe

Resilience audit, migrate-to-seed (the sweep RPC is byte-identical — see below):
- Adopt was enabled at >= 1 confirmation and never re-read state before stopping the daemon, so a 1-block
  reorg after the swap could un-mine the sweep and strand the funds in the .bak. Adopt now needs a
  reorg-safe depth (>= 10, matching the History "confirmed" threshold), and the button runs
  verifyThenAdoptSeedWallet(): a read-only gettransaction(confs) + z_gettotalbalance minconf 0 (includes
  unconfirmed, fixing the old minconf-1 "no funds" gate) immediately before the daemon stop, refusing while
  syncing or if any read fails. The remainder re-sweep still shows once mined (>=1).
- The wallet.dat swap was rename(legacy->bak) then non-atomic copy(new->wallet.dat): a hard kill left
  wallet.dat missing or half-written. New order: probe the new file is a BDB wallet; stage a size-verified
  copy beside wallet.dat; COPY (never overwrite) the legacy wallet to the timestamped .bak and verify it;
  then ONE atomic fs::rename of the staged file over wallet.dat. At every instant wallet.dat is the whole
  old or whole new wallet, and a verified .bak exists before the replace. On any failure only our scratch
  files are removed; the user's wallet is untouched.

Byte-identical: z_mergetoaddress (beginSweepToSeedWallet, ["ANY_TADDR","ANY_ZADDR"], amounts, fee, recipient,
memo) and beginAdoptSeedWallet's disconnect/vault-removal/stop/rescan/restart logic are unchanged; only the
adopt gating, two new read-only RPCs, presentation, and the file-move safety change. Pure tests:
sweepConfsAreReorgSafe + adoptReverifyPasses.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

src/app.cpp

@@ -5043,7 +5043,7 @@ void App::renderSeedMigrationDialog()
             ImGui::Spacing();
             if (!seed_migration_nofunds_confirmed_) ImGui::BeginDisabled();
             if (ui::material::TactileButton(TR("mig_adopt_now"), ImVec2(190 * dp, 0)))
-                beginAdoptSeedWallet();
+                verifyThenAdoptSeedWallet();   // fresh minconf-0, sync-aware balance check before the swap
             if (!seed_migration_nofunds_confirmed_) ImGui::EndDisabled();
             ImGui::SameLine();
             if (ui::material::TactileButton(TR("refresh"), ImVec2(110 * dp, 0)))
@@ -5107,7 +5107,8 @@ void App::renderSeedMigrationDialog()
 
     case SeedMigrationStep::Confirming: {
         const double dust = DRAGONX_DEFAULT_FEE;  // treat <= one fee as "empty"
-        const bool confirmed = seed_migration_sweep_confs_ >= 1;
+        const bool mined = seed_migration_sweep_confs_ >= 1;   // remainder re-sweep stays offered once mined
+        const bool confirmed = dragonx::sweepConfsAreReorgSafe(seed_migration_sweep_confs_);  // adopt needs reorg-safe depth
         const bool legacyEmpty = seed_migration_legacy_remaining_ >= 0.0 &&
                                  seed_migration_legacy_remaining_ <= dust;
         ImGui::TextWrapped("%s", TR("mig_confirming"));
@@ -5127,8 +5128,8 @@ void App::renderSeedMigrationDialog()
         ImGui::Spacing();
         if (confirmed && legacyEmpty) {
             if (ui::material::TactileButton(TR("mig_adopt"), ImVec2(180 * dp, 0)))
-                beginAdoptSeedWallet();
-        } else if (confirmed && seed_migration_legacy_remaining_ >= 0.0 && !legacyEmpty) {
+                verifyThenAdoptSeedWallet();   // re-reads confs + balance right before the daemon stop
+        } else if (mined && seed_migration_legacy_remaining_ >= 0.0 && !legacyEmpty) {
             // Only claim a remainder once the legacy balance was actually measured; while a sweep is
             // mined but the balance scan is still gated (node syncing), remaining stays at the -1.0
             // sentinel, so fall through to the waiting state rather than offering a sweep on an unknown.
@@ -5152,6 +5153,10 @@ void App::renderSeedMigrationDialog()
                 if (ui::material::TactileButton(TR("cancel"), ImVec2(110 * dp, 0)))
                     seed_migration_confirm_sweep_ = false;
             }
+        } else if (mined && legacyEmpty) {
+            // Mined but not yet reorg-safe deep: say so instead of the misleading "waiting to be mined".
+            char dbuf[200]; snprintf(dbuf, sizeof(dbuf), TR("mig_waiting_depth"), dragonx::kSweepAdoptMinConfs);
+            ImGui::TextWrapped("%s", dbuf);
         } else {
             ImGui::TextColored(kMedium, "%s", TR("mig_waiting_mine"));
         }

src/app.h

@@ -1188,6 +1188,7 @@ private:
     void pollSweepStatus(bool forceBalance = false);  // Confirming step: confs always; balance only when it can move the gate
     void locateSweepTxid();              // recover a lost sweep txid (send to dest) -> Confirming gate
     void beginAdoptSeedWallet();         // stop daemon -> swap wallet.dat -> restart with -rescan
+    void verifyThenAdoptSeedWallet();    // re-read sweep confs + minconf-0 balance, then beginAdoptSeedWallet() iff safe
     void provisionChatIdentityFromSecret(std::string secret);
     std::string chatReplyZaddr();                                // a stable (persisted) wallet z-addr — chat IDENTITY (reply-to)
     // A spendable z-address that can actually PAY `need` (a fee, or a split's notes plus its fee), preferring

src/app_network.cpp

@@ -41,6 +41,10 @@
 #include "ui/windows/mining_pool_panel.h"  // ui::resolveMiningUserAddress
 #include <sodium.h>              // sodium_memzero for wiping the fetched mnemonic
 #include <cctype>
+#ifndef _WIN32
+#include <fcntl.h>               // open/fsync: flush the staged wallet + .bak before the atomic swap
+#include <unistd.h>
+#endif
 #include "config/settings.h"
 #include "wallet/lite_wallet_controller.h"  // lite send/new-address routing
 #include "wallet/lite_wallet_state_mapper.h"  // LiteWalletAppRefreshModel for lite chat harvest
@@ -6571,6 +6575,57 @@ void App::locateSweepTxid()
     });
 }
 
+// Final gate before the swap: on the RPC worker, RE-READ the sweep tx's confirmations (when a sweep txid
+// exists) and z_gettotalbalance with minconf 0 (includes unconfirmed, unlike the default minconf 1), then
+// - only if both are reorg-safe, the node is not syncing and the legacy balance is ~0 - call
+// beginAdoptSeedWallet() on the main thread, so the disconnect + daemon stop follow these reads at once.
+// Read-only RPCs; any failure blocks adopt (nothing is stopped or swapped) and the user may retry.
+void App::verifyThenAdoptSeedWallet()
+{
+    if (capture_mode_) { beginAdoptSeedWallet(); return; }   // UI sweep: unchanged behaviour
+    if (seed_migration_confirm_in_flight_) return;
+    if (!rpc_ || !worker_ || !state_.connected) {
+        ui::Notifications::instance().warning(TR("mig_adopt_reverify_failed"));
+        return;
+    }
+    seed_migration_confirm_in_flight_ = true;
+    const std::string txid = seed_migration_sweep_txid_;
+    const bool needTx = !txid.empty();
+    const bool syncing = effectivelySyncing();   // main-thread snapshot for the worker
+    worker_->post([this, txid, needTx, syncing]() -> rpc::RPCWorker::MainCb {
+        int confs = 0; double total = -1.0; bool ok = false;
+        rpc::RPCClient::TraceScope trace("Migrate / pre-adopt verify");
+        try {
+            if (needTx) {
+                auto tx = rpc_->call("gettransaction", {txid});
+                if (!tx.contains("confirmations") || !tx["confirmations"].is_number()) throw std::runtime_error("no confirmations");
+                confs = tx["confirmations"].get<int>();
+            }
+            auto bal = rpc_->call("z_gettotalbalance", nlohmann::json::array({0}));   // minconf 0
+            if (bal.contains("total") && bal["total"].is_string()) {
+                total = std::stod(bal["total"].get<std::string>());
+                ok = true;
+            }
+        } catch (...) { ok = false; }
+        return [this, needTx, syncing, confs, total, ok]() {
+            seed_migration_confirm_in_flight_ = false;
+            if (ok) {
+                if (needTx) seed_migration_sweep_confs_ = confs;
+                seed_migration_legacy_remaining_ = total;
+            }
+            // Only act while still on a step that offers Adopt (the user may have closed/changed it).
+            const bool onAdoptStep = seed_migration_step_ == SeedMigrationStep::Confirming ||
+                                     seed_migration_step_ == SeedMigrationStep::Sweep;
+            if (ok && onAdoptStep &&
+                dragonx::adoptReverifyPasses(needTx, confs, total, syncing, DRAGONX_DEFAULT_FEE)) {
+                beginAdoptSeedWallet();   // unchanged: stop daemon -> swap -> restart with -rescan
+            } else if (onAdoptStep) {
+                ui::Notifications::instance().warning(TR("mig_adopt_reverify_failed"), 12.0f);
+            }
+        };
+    });
+}
+
 // Phase 2 step 2: adopt the new seed wallet as the primary wallet. Stop the daemon, move the
 // legacy wallet.dat aside to a timestamped backup (NEVER delete it), copy the new wallet in, and
 // restart with -rescan so the new keys pick up the swept funds. Runs on a background thread.
@@ -6632,21 +6687,53 @@ void App::beginAdoptSeedWallet()
                 const std::string backup = legacy + ".legacy-migrated-" + ts + ".bak";
                 if (!fs::exists(newWallet)) {
                     err = "The new wallet file is missing; your wallet was not changed.";
+                } else if (!util::probeWalletFile(newWallet).isBerkeleyDB) {
+                    err = "The new wallet file is not a valid wallet; your wallet was not changed.";
                 } else {
-                    bool movedLegacy = false;
-                    if (fs::exists(legacy)) {
-                        fs::rename(legacy, backup, ec);
-                        if (ec) err = "Could not back up your current wallet; nothing was changed.";
-                        else movedLegacy = true;
-                    }
-                    if (err.empty()) {
-                        fs::copy_file(newWallet, legacy, fs::copy_options::overwrite_existing, ec);
-                        if (ec) {
-                            if (movedLegacy) { std::error_code ec2; fs::rename(backup, legacy, ec2); }
-                            err = "Could not install the new wallet; your original wallet was restored.";
-                        } else {
-                            swapDone = true;
+                    // Crash-safe order: wallet.dat is only ever REPLACED by one atomic rename of a complete,
+                    // size-verified staged copy, and only AFTER a complete size-verified .bak of the legacy
+                    // wallet exists. A hard kill at any point leaves wallet.dat as either the whole old or the
+                    // whole new wallet - never missing or half-written. Nothing of the user's is deleted.
+                    const std::string staged = legacy + ".adopt-tmp";
+                    auto sameSize = [](const std::string& a, const std::string& b) {
+                        std::error_code e1, e2;
+                        const auto sa = fs::file_size(a, e1);
+                        const auto sb = fs::file_size(b, e2);
+                        return !e1 && !e2 && sa == sb && sa > 0;
+                    };
+#ifndef _WIN32
+                    auto syncFile = [](const std::string& p) {   // best-effort flush to disk
+                        int fd = ::open(p.c_str(), O_RDONLY);
+                        if (fd >= 0) { ::fsync(fd); ::close(fd); }
+                    };
+#else
+                    auto syncFile = [](const std::string&) {};
+#endif
+                    bool backupCreated = false;
+                    // (a) Stage a full copy of the new wallet beside wallet.dat (same dir => atomic rename).
+                    fs::copy_file(newWallet, staged, fs::copy_options::overwrite_existing, ec);
+                    if (ec || !sameSize(newWallet, staged)) {
+                        err = "Could not stage the new wallet; nothing was changed.";
+                    } else {
+                        syncFile(staged);
+                        // (b) COPY (not rename) the legacy wallet to the timestamped .bak and verify it.
+                        if (fs::exists(legacy)) {
+                            backupCreated = !fs::exists(backup);
+                            fs::copy_file(legacy, backup, fs::copy_options::none, ec);   // never overwrites an existing .bak
+                            if (ec || !sameSize(legacy, backup)) err = "Could not back up your current wallet; nothing was changed.";
+                            else syncFile(backup);
                         }
+                        // (c) Atomically replace wallet.dat with the staged wallet.
+                        if (err.empty()) {
+                            fs::rename(staged, legacy, ec);
+                            if (ec) err = "Could not install the new wallet; your original wallet was left unchanged.";
+                            else swapDone = true;
+                        }
+                    }
+                    if (!err.empty()) {   // failed before the replace: original untouched; drop only OUR scratch files
+                        std::error_code e3;
+                        fs::remove(staged, e3);
+                        if (backupCreated) fs::remove(backup, e3);
                     }
                 }
             }

src/data/seed_migration_resume.h

@@ -42,4 +42,24 @@ inline MigrationResume decideSeedMigrationResume(bool pending,
 // wallet.dat on an unconfirmed sweep. (fund-safety: audit)
 inline bool sweepGateMayAdoptEmptyWallet(bool sweepSubmitted) { return !sweepSubmitted; }
 
+// Reorg-safe depth before the adopt swap is enabled. Matches the History "confirmed" threshold
+// (>= 10, data/transaction_history_store_policy.h): a 1-block reorg must not be able to un-mine the
+// sweep after wallet.dat has been moved aside, which would strand the funds in the .bak.
+inline constexpr int kSweepAdoptMinConfs = 10;
+inline bool sweepConfsAreReorgSafe(int confs) { return confs >= kSweepAdoptMinConfs; }
+
+// Final pre-stop re-verification, run on fresh RPC reads immediately before the daemon is stopped.
+//   needSweepTx : a sweep txid exists, so its confirmations must be reorg-safe (false = genuinely
+//                 empty wallet, no sweep ever submitted).
+//   confs       : fresh gettransaction confirmations (negative = conflicted).
+//   balanceMinconf0 : fresh z_gettotalbalance with minconf 0 (INCLUDES unconfirmed), < 0 = unknown.
+//   syncing     : the node is still catching up, so balance reads are not trustworthy.
+inline bool adoptReverifyPasses(bool needSweepTx, int confs, double balanceMinconf0,
+                                bool syncing, double dust)
+{
+    if (syncing) return false;
+    if (needSweepTx && !sweepConfsAreReorgSafe(confs)) return false;
+    return balanceMinconf0 >= 0.0 && balanceMinconf0 <= dust;
+}
+
 }  // namespace dragonx

src/util/i18n.cpp

@@ -521,6 +521,8 @@ void I18n::loadBuiltinEnglish()
         strings_["mig_sweep_confirm"] = "Send %.8f DRGX from your current wallet to the new seed wallet in a single transaction? This moves all of your funds.";
         strings_["mig_sweep_confirm_yes"] = "Yes, sweep funds";
         strings_["mig_waiting_mine"] = "Waiting for the sweep transaction to be mined…";
+        strings_["mig_waiting_depth"] = "Sweep mined. Waiting for %d confirmations before switching wallets, so a short chain reorganisation cannot undo it…";
+        strings_["mig_adopt_reverify_failed"] = "Could not confirm it is safe to switch wallets yet (the node may still be syncing, the sweep is not deep enough, or funds remain). Nothing was changed - wait and try again.";
         strings_["mig_adopting"] = "Installing your new wallet and rescanning…";
         strings_["mig_done"] = "Migration complete. Your wallet is now backed by your seed phrase.";
         strings_["mig_done_detail"] = "The daemon is rescanning to show your funds — this can take a few minutes. Your previous wallet was saved as a .bak in the data folder.";