FuelLabs/fuels-ts · error · FuelError

DECODE_ERROR

DECODE_ERROR

Error message

Invalid byte data size.

What it means

Thrown by ByteCoder.decode at the top guard: data.length < WORD_SIZE (8). The message is the literal "Invalid byte data size.". A Sway Bytes value is length-prefixed by a u64, so at least 8 bytes are needed just to read the length. Fewer than 8 bytes means the payload cannot contain the length header.

Source

Thrown at packages/abi-coder/src/encoding/coders/ByteCoder.ts:24

import { Coder } from './AbstractCoder';
import { BigNumberCoder } from './BigNumberCoder';

export class ByteCoder extends Coder<number[], Uint8Array> {
  static memorySize = 1;
  constructor() {
    super('struct', 'struct Bytes', WORD_SIZE);
  }

  encode(value: number[] | Uint8Array): Uint8Array {
    const bytes = value instanceof Uint8Array ? value : new Uint8Array(value);
    const lengthBytes = new BigNumberCoder('u64').encode(bytes.length);

    return new Uint8Array([...lengthBytes, ...bytes]);
  }

  decode(data: Uint8Array, offset: number): [Uint8Array, number] {
    if (data.length < WORD_SIZE) {
      throw new FuelError(ErrorCode.DECODE_ERROR, `Invalid byte data size.`);
    }

    const offsetAndLength = offset + WORD_SIZE;
    const lengthBytes = data.slice(offset, offsetAndLength);
    const length = bn(new BigNumberCoder('u64').decode(lengthBytes, 0)[0]).toNumber();

    const dataBytes = data.slice(offsetAndLength, offsetAndLength + length);

    if (dataBytes.length !== length) {
      throw new FuelError(ErrorCode.DECODE_ERROR, `Invalid bytes byte data size.`);
    }

    return [dataBytes, offsetAndLength + length];
  }
}

View on GitHub (pinned to b3f37c91ac)

Solutions

1. Verify data.length >= WORD_SIZE (8) before decode.
2. Confirm the bytes actually represent a length-prefixed Sway Bytes value.
3. Let AbiCoder handle offset/prefix bookkeeping.

if (data.length < 8) throw new Error('need >= 8 bytes for Bytes length header')
byteCoder.decode(data, offset)

const canDecodeBytes = (data: Uint8Array) => data.length >= 8

try { byteCoder.decode(data, offset) }
catch (e) { if ((e as FuelError).code === ErrorCode.DECODE_ERROR) { /* payload too short / wrong coder */ } throw e }

When it happens

Trigger: Calling byteVec.decode(data, offset) with data shorter than 8 bytes, e.g. a truncated or empty payload, or a wrong offset leaving fewer than 8 bytes.

Common situations: Truncated Bytes return data from the provider; wrong coder applied to the bytes; manual offset advanced past the length header; decoding an empty/garbage buffer.

Related errors

• DECODE_ERROR
• DECODE_ERROR
• DECODE_ERROR
• DECODE_ERROR
• DECODE_ERROR

AI-assisted analysis of FuelLabs/fuels-ts@b3f37c91ac (2026-08-12). Data as JSON: /api/errors/4e5cef0402a0cd2c. Report an issue: GitHub.