wolfsenberg · wolfsenberg · May 23, 2026
diff --git a/frontend/src/app/(marketing)/detail/[slug]/page.tsx b/frontend/src/app/(marketing)/detail/[slug]/page.tsx
@@ -4,7 +4,7 @@ import Link from "next/link";
 import { notFound, useParams } from "next/navigation";
 import { useFreighter } from "@/hooks/useFreighter";
 import { balanceApi, campaignsApi, donationsApi, type BalanceApi } from "@/lib/api";
-import { formatLedgerReference, getStellarExpertContractUrl, getStellarExpertTxUrl, isStellarTxHash, buildPaymentTransaction, submitSignedTransactionXdr, STELLAR_CONFIG } from "@/lib/stellar";
+import { formatLedgerReference, getStellarExpertContractUrl, getStellarExpertTxUrl, isStellarTxHash, buildSignAndSubmit, STELLAR_CONFIG } from "@/lib/stellar";
 import toast from "react-hot-toast";
 import VotingPanel from "@/components/stellar/VotingPanel";
 import SafeImageFrame from "@/components/campaign/SafeImageFrame";
@@ -266,51 +266,45 @@ export default function DetailPage() {
     const memo = `LNGP-DON-${campaignId}`.slice(0, 28);
 
     try {
-      // 1. Build unsigned XLM payment to LINGAP receiver
-      const tx = await buildPaymentTransaction(
-        publicKey,
-        receivingWallet,
-        effectiveAmount.toFixed(7),
-        undefined,
-        memo,
-      );
-
-      // 2. Freighter signs → popup appears here
+      // buildSignAndSubmit: builds tx with fresh sequence, Freighter signs,
+      // submits raw XDR, auto-retries once on tx_bad_seq
       toast("Check your Freighter wallet to sign the donation.", { icon: "🔐", duration: 8000 });
-      let signedXdr: string;
+      let realTxHash: string;
       try {
-        signedXdr = await sign(tx.toXDR(), STELLAR_CONFIG.network);
+        const result = await buildSignAndSubmit(
+          publicKey,
+          receivingWallet,
+          effectiveAmount.toFixed(7),
+          memo,
+          sign,
+        );
+        realTxHash = result.hash;
       } catch (signErr: unknown) {
         const msg = signErr instanceof Error ? signErr.message : String(signErr);
         if (msg.toLowerCase().includes("user declined") || msg.toLowerCase().includes("rejected")) {
           toast.error("Donation cancelled in Freighter.");
         } else {
-          toast.error(`Freighter error: ${msg}`);
+          toast.error(msg);
         }
         return;
       }
 
-      // 3. Submit to Stellar Horizon — real on-chain tx
-      toast("Submitting to Stellar network...", { icon: "🚀", duration: 6000 });
-      const submitResult = await submitSignedTransactionXdr(signedXdr);
-      const realTxHash = submitResult.hash;
-
-      // 4. Record in LINGAP DB with the real Stellar tx hash + deduct balance
+      // Record in LINGAP DB with the real Stellar tx hash + deduct balance
       await donationsApi.create({
         amount: Number(effectiveAmount.toFixed(7)),
         asset: "XLM",
         purpose: donationPurpose,
         stellarTxHash: realTxHash,
         fundingSource: "stellar_wallet",
-        spendBalance: true,   // deducts from LINGAP balance AND records real tx hash
+        spendBalance: true,
         walletAddress: publicKey,
       });
 
       setConfirmedDonationXlm((c) => c + effectiveAmount);
       setLastTxHash(realTxHash);
       toast.success(`Donation confirmed on Stellar! TX: ${realTxHash.slice(0, 10)}...`);
 
-      // 5. Refresh live totals
+      // Refresh live totals
       try {
         const [latest, nextBalance] = await Promise.all([
           campaignsApi.publicOne(campaignId),

diff --git a/frontend/src/components/balance/TopUpModal.tsx b/frontend/src/components/balance/TopUpModal.tsx
@@ -7,6 +7,7 @@ import { balanceApi, type BalanceApi, type BalanceTransactionApi } from "@/lib/a
 import { useFreighter } from "@/hooks/useFreighter";
 import {
   buildPaymentTransaction,
+  buildSignAndSubmit,
   getStellarExpertContractUrl,
   getStellarExpertTxUrl,
   submitSignedTransactionXdr,
@@ -116,8 +117,6 @@ export default function TopUpModal({ open, onClose, rate, onConfirmed }: TopUpMo
     setConfirmedTxHash("");
 
     try {
-      let stellarTxHash: string | undefined;
-
       // ── ALL methods: send a real Stellar payment through Freighter ──────────
       // This makes every top-up visible on stellar.expert regardless of
       // payment method. The memo identifies the source channel.
@@ -139,39 +138,34 @@ export default function TopUpModal({ open, onClose, rate, onConfirmed }: TopUpMo
 
       toast("Check your Freighter wallet to sign the top-up.", { icon: "🔐", duration: 8000 });
 
-      const tx = await buildPaymentTransaction(
-        publicKey,
-        receivingWallet,
-        amountXlm.toFixed(7),
-        undefined,
-        memoLabel,
-      );
-
-      let signedXdr: string;
+      let stellarTxHash: string;
       try {
-        signedXdr = await sign(tx.toXDR(), NETWORK_PASSPHRASE);
+        const result = await buildSignAndSubmit(
+          publicKey,
+          receivingWallet,
+          amountXlm.toFixed(7),
+          memoLabel,
+          sign,
+        );
+        stellarTxHash = result.hash;
       } catch (signErr: unknown) {
         const msg = signErr instanceof Error ? signErr.message : String(signErr);
         if (msg.toLowerCase().includes("user declined") || msg.toLowerCase().includes("rejected")) {
           toast.error("Transaction cancelled in Freighter.");
         } else {
-          toast.error(`Freighter error: ${msg}`);
+          toast.error(msg);
         }
         return;
       }
 
-      toast("Submitting to Stellar network...", { icon: "🚀", duration: 6000 });
-      const submitResult = await submitSignedTransactionXdr(signedXdr);
-      stellarTxHash = submitResult.hash;
-
       // ── Record in LINGAP backend ─────────────────────────────────────────
       const res = await balanceApi.simulateTopUp({
         paymentMethod: method,
         amountXlm: Number(amountXlm.toFixed(7)),
         senderReference: senderReference.trim() || undefined,
         senderName: senderName.trim() || undefined,
         senderWallet: publicKey,
-        stellarTxHash,
+        stellarTxHash: stellarTxHash,
       });
 
       const topUpTx = res.data.data.top_up;

diff --git a/frontend/src/lib/stellar.ts b/frontend/src/lib/stellar.ts
@@ -5,7 +5,6 @@ import {
   Asset,
   Keypair,
   Horizon,
-  BASE_FEE,
   Memo,
 } from "@stellar/stellar-sdk";
 
@@ -36,10 +35,13 @@ export async function buildPaymentTransaction(
   asset: Asset = Asset.native(),
   memo?: string
 ) {
+  // Always load a fresh account to get the latest sequence number.
+  // Stale sequences cause tx_bad_seq errors when multiple transactions
+  // are submitted in quick succession.
   const sourceAccount = await loadAccount(sourcePublicKey);
 
   const txBuilder = new TransactionBuilder(sourceAccount, {
-    fee: BASE_FEE,
+    fee: "10000", // 10,000 stroops — avoids tx_insufficient_fee on testnet
     networkPassphrase: STELLAR_CONFIG.network,
   });
 
@@ -49,13 +51,88 @@ export async function buildPaymentTransaction(
 
   if (memo) txBuilder.addMemo(Memo.text(memo));
 
-  txBuilder.setTimeout(180);
+  // 30s timeout — enough for Freighter to sign without the tx expiring
+  txBuilder.setTimeout(30);
   return txBuilder.build();
 }
 
-export async function submitSignedTransactionXdr(signedXdr: string) {
-  const transaction = TransactionBuilder.fromXDR(signedXdr, STELLAR_CONFIG.network);
-  return horizonServer.submitTransaction(transaction);
+export async function submitSignedTransactionXdr(
+  signedXdr: string,
+  retries = 1,
+): Promise<{ hash: string; successful: boolean }> {
+  // Submit the raw signed XDR directly to Horizon via fetch.
+  // Using the SDK's submitTransaction() can silently re-encode the envelope
+  // and drop the Freighter signature, causing tx_bad_auth errors.
+  const params = new URLSearchParams({ tx: signedXdr });
+  const res = await fetch(`${STELLAR_CONFIG.horizonUrl}/transactions`, {
+    method: "POST",
+    headers: { "Content-Type": "application/x-www-form-urlencoded" },
+    body: params.toString(),
+  });
+  const data = await res.json();
+
+  if (!res.ok) {
+    const codes = data?.extras?.result_codes;
+    const txCode: string = codes?.transaction ?? "";
+    const opCodes: string[] = codes?.operations ?? [];
+
+    // tx_bad_seq means the sequence was stale — the caller should rebuild
+    // the transaction with a fresh sequence and re-sign. We surface this
+    // as a distinct error so the UI can give a clear message.
+    if (txCode === "tx_bad_seq") {
+      throw new Error("TX_BAD_SEQ");
+    }
+
+    // op_underfunded — not enough XLM in the source wallet
+    if (opCodes.includes("op_underfunded")) {
+      throw new Error("Insufficient XLM in your Freighter wallet. Please fund your testnet account via friendbot.stellar.org.");
+    }
+
+    // op_no_destination — destination account doesn't exist on this network
+    if (opCodes.includes("op_no_destination")) {
+      throw new Error("The LINGAP receiving wallet doesn't exist on this network yet. Contact support.");
+    }
+
+    const detail = codes
+      ? `Stellar error: ${JSON.stringify(codes)}`
+      : data?.detail || data?.title || "Transaction failed";
+    throw new Error(detail);
+  }
+
+  return data as { hash: string; successful: boolean };
+}
+
+/**
+ * Build, sign (via Freighter), and submit a payment transaction.
+ * Automatically retries once on tx_bad_seq by rebuilding with a fresh sequence.
+ */
+export async function buildSignAndSubmit(
+  sourcePublicKey: string,
+  destinationPublicKey: string,
+  amount: string,
+  memo: string,
+  signFn: (xdr: string, networkPassphrase: string) => Promise<string>,
+): Promise<{ hash: string }> {
+  for (let attempt = 0; attempt < 2; attempt++) {
+    const tx = await buildPaymentTransaction(
+      sourcePublicKey,
+      destinationPublicKey,
+      amount,
+      undefined,
+      memo,
+    );
+    const signedXdr = await signFn(tx.toXDR(), STELLAR_CONFIG.network);
+    try {
+      const result = await submitSignedTransactionXdr(signedXdr);
+      return { hash: result.hash };
+    } catch (err: unknown) {
+      const msg = err instanceof Error ? err.message : String(err);
+      // On bad sequence, rebuild with fresh account data and retry once
+      if (msg === "TX_BAD_SEQ" && attempt === 0) continue;
+      throw err;
+    }
+  }
+  throw new Error("Transaction failed after retry.");
 }
 
 export function getStellarExpertTxUrl(txHash: string) {

diff --git a/frontend/tsconfig.tsbuildinfo b/frontend/tsconfig.tsbuildinfo