FuelLabs/fuels-ts · error · FuelError

INVALID_TRANSACTION_OUTPUT

INVALID_TRANSACTION_OUTPUT

Error message

Invalid transaction output type: ${type}.

What it means

Thrown by OutputCoder.encode() when output.type is not one of OutputType (Coin=0, Contract=1, Change=2, Variable=3, ContractCreated=4). The encode switch falls through to default. It indicates an output object with an out-of-range type.

Source

Thrown at packages/transactions/src/coders/output.ts:293

      }
      case OutputType.Contract: {
        parts.push(new OutputContractCoder().encode(value));
        break;
      }
      case OutputType.Change: {
        parts.push(new OutputChangeCoder().encode(value));
        break;
      }
      case OutputType.Variable: {
        parts.push(new OutputVariableCoder().encode(value));
        break;
      }
      case OutputType.ContractCreated: {
        parts.push(new OutputContractCreatedCoder().encode(value));
        break;
      }
      default: {
        throw new FuelError(
          ErrorCode.INVALID_TRANSACTION_OUTPUT,
          `Invalid transaction output type: ${type}.`
        );
      }
    }

    return concat(parts);
  }

  decode(data: Uint8Array, offset: number): [Output, number] {
    let decoded;
    let o = offset;

    [decoded, o] = new NumberCoder('u8', { padToWordSize: true }).decode(data, o);
    const type = decoded as OutputType;
    switch (type) {
      case OutputType.Coin: {
        [decoded, o] = new OutputCoinCoder().decode(data, o);

View on GitHub (pinned to b3f37c91ac)

Solutions

1. Use the OutputType enum and SDK output factories when constructing outputs.
2. Validate output.type is one of the five known OutputType values before encoding.
3. Upgrade @fuel-ts/transactions if a newer output type is required.

Example fix

// before
const out = { type: 7, ... };

// after
import { OutputType } from '@fuel-ts/transactions';
const out = { type: OutputType.Coin, ... };

import { OutputType } from '@fuel-ts/transactions';

const VALID_OUTPUT_TYPES = new Set([OutputType.Coin, OutputType.Contract, OutputType.Change, OutputType.Variable, OutputType.ContractCreated]);
outputs.forEach(o => { if (!VALID_OUTPUT_TYPES.has(o.type as OutputType)) throw new Error(`Bad output type ${o.type}`); });

import { OutputType } from '@fuel-ts/transactions';
function isValidOutput(o: { type: number }): boolean {
  return [OutputType.Coin, OutputType.Contract, OutputType.Change, OutputType.Variable, OutputType.ContractCreated].includes(o.type as OutputType);
}

try {
  outputCoder.encode(value);
} catch (e) {
  if (e instanceof FuelError && e.code === ErrorCode.INVALID_TRANSACTION_OUTPUT) {
    // coerce output.type to a valid OutputType enum member before retrying
  } else throw e;
}

When it happens

Trigger: Manually constructing an Output with an invalid type number; assigning type: 5+; building transaction outputs from unvalidated external data.

Common situations: Hand-assembling outputs instead of using SDK helpers; protocol/SDK version mismatch introducing a new output kind; off-by-one type assignments.

Related errors

• INVALID_TRANSACTION_INPUT
• INVALID_POLICY_TYPE
• UNSUPPORTED_TRANSACTION_TYPE
• INVALID_TRANSACTION_INPUT
• INVALID_TRANSACTION_INPUT

AI-assisted analysis of FuelLabs/fuels-ts@b3f37c91ac (2026-08-12). Data as JSON: /api/errors/225dc37d20f946c2. Report an issue: GitHub.