Protobuf (Direct) Encoding

interface SignDoc {
  bodyBytes: Uint8Array;     // encoded TxBody
  authInfoBytes: Uint8Array; // encoded AuthInfo
  chainId: string;
  accountNumber: bigint;
}

import { makeAuthInfoBytes, makeSignDoc, makeSignBytes } from "@cosmjs/proto-signing";

const bodyBytes = registry.encodeTxBody({ messages, memo });

const authInfoBytes = makeAuthInfoBytes(
  [{ pubkey: encodedPubkey, sequence }],
  feeAmount,
  gasLimit,
  feeGranter,
  feePayer,
);

const signDoc = makeSignDoc(bodyBytes, authInfoBytes, chainId, accountNumber);
const bytesToSign = makeSignBytes(signDoc);

const authInfoBytes = makeAuthInfoBytes(
  signers,   // [{ pubkey, sequence }]
  feeAmount, // Coin[]
  gasLimit,  // number
  feeGranter,
  feePayer,
  signMode,  // defaults to SIGN_MODE_DIRECT
);

import { TxRaw } from "cosmjs-types/cosmos/tx/v1beta1/tx";

const txRaw = TxRaw.fromPartial({
  bodyBytes,
  authInfoBytes,
  signatures: [signature],
});

const txBytes = TxRaw.encode(txRaw).finish();