Located bug.

Example output:
from query: account: number = 4, sequence = 0
for signing: nonce: 0

src/cosmoscodec.ts

@@ -54,6 +54,8 @@ export class CosmosCodec implements TxCodec {
   }
 
   public bytesToSign(unsigned: UnsignedTransaction, nonce: Nonce): SigningJob {
+    console.log("nonce:", nonce);
+    // ohhh... this is a bug!!!
     const accountNumber = 0;
     const memo = (unsigned as any).memo;
     const built = buildUnsignedTx(unsigned, this.tokens);

src/cosmosconnection.ts

@@ -171,6 +171,7 @@ export class CosmosConnection implements BlockchainConnection {
     const address = isPubkeyQuery(query) ? pubkeyToAddress(query.pubkey, this.prefix) : query.address;
     const { result } = await this.restClient.authAccounts(address);
     const account = result.value;
+    console.log(`account: number = ${account.account_number}, sequence = ${account.sequence}`);
     return parseInt(account.sequence, 10) as Nonce;
   }