Submitting Reports Onchain

This guide shows how to manually submit a generated CRE report to the blockchain using the low-level evm.Client.WriteReport() method. The forwarder verifies signatures onchain: no separate offchain verification step.

Use this approach when:

You've already generated a report using runtime.GenerateReport() (from single value or struct generation)
You need fine-grained control over the submission process
You don't have (or can't use) the WriteReportFrom<StructName>() binding helper

Prerequisites

You must have:

A generated report ready to submit (from single value or struct generation)
A consumer contract address that implements the IReceiver interface

Step-by-step example

Step 1: Create an EVM client

import "github.com/smartcontractkit/cre-sdk-go/capabilities/blockchain/evm"

evmClient := &evm.Client{
    ChainSelector: config.ChainSelector, // e.g., 16015286601757825753 for Sepolia
}

Step 2: Prepare submission parameters

import "github.com/ethereum/go-ethereum/common"

// Receiver contract address (must implement IReceiver interface)
receiverAddress := common.HexToAddress(config.ReceiverAddress)

// Optional gas configuration
gasConfig := &evm.GasConfig{
    GasLimit: config.GasLimit, // e.g., 1000000
}

Step 3: Submit the report

writePromise := evmClient.WriteReport(runtime, &evm.WriteCreReportRequest{
    Receiver:  receiverAddress.Bytes(),
    Report:    report, // The report from runtime.GenerateReport()
    GasConfig: gasConfig,
})

resp, err := writePromise.Await()
if err != nil {
    return fmt.Errorf("failed to write report: %w", err)
}

// Extract transaction hash
txHash := fmt.Sprintf("0x%x", resp.TxHash)
logger.Info("Report submitted successfully", "txHash", txHash)

Understanding the response

The WriteReportReply struct provides comprehensive transaction details:

type WriteReportReply struct {
    TxStatus                        TxStatus                         // SUCCESS, REVERTED, or FATAL
    ReceiverContractExecutionStatus *ReceiverContractExecutionStatus // Contract execution status
    TxHash                          []byte                            // Transaction hash
    TransactionFee                  *pb.BigInt                        // Fee paid in Wei
    ErrorMessage                    *string                           // Error message if failed
}

Key fields to check:

TxStatus: Indicates whether the transaction succeeded, reverted, or had a fatal error
TxHash: The transaction hash you can use to verify on a block explorer (e.g., Etherscan)
TransactionFee: The total gas cost paid for the transaction in Wei
ReceiverContractExecutionStatus: Whether your consumer contract's onReport() function executed successfully
ErrorMessage: If the transaction failed, this field contains details about what went wrong

Best practices

When submitting reports onchain, follow these practices to ensure reliability and observability:

Log transaction details: Always log the transaction hash for debugging and monitoring. This allows you to track your submission on block explorers and troubleshoot issues.
```
txHash := fmt.Sprintf("0x%x", resp.TxHash)
logger.Info("Report submitted successfully", "txHash", txHash, "status", resp.TxStatus)
```
Handle gas configuration: Provide explicit gas limits for complex transactions to avoid out-of-gas errors. Adjust based on your contract's complexity and the data size.
```
gasConfig := &evm.GasConfig{
    GasLimit: 500000, // Adjust based on your needs
}
```

Monitor transaction status: Always check the TxStatus field in the response to ensure your transaction was successful. Handle REVERTED and FATAL statuses appropriately.

if resp.TxStatus != evm.TxStatusSuccess {
    return fmt.Errorf("transaction failed with status: %v, error: %s", resp.TxStatus, *resp.ErrorMessage)
}

Complete example

Here's a full workflow that generates a report from a single value and submits it onchain:

//go:build wasip1

package main

import (
	"fmt"
	"log/slog"
	"math/big"

	"github.com/ethereum/go-ethereum/accounts/abi"
	"github.com/ethereum/go-ethereum/common"
	"github.com/smartcontractkit/cre-sdk-go/capabilities/blockchain/evm"
	"github.com/smartcontractkit/cre-sdk-go/capabilities/scheduler/cron"
	"github.com/smartcontractkit/cre-sdk-go/cre"
	"github.com/smartcontractkit/cre-sdk-go/cre/wasm"
)

type Config struct {
	Schedule        string `json:"schedule"`
	ReceiverAddress string `json:"receiverAddress"`
	ChainSelector   uint64 `json:"chainSelector"`
	GasLimit        uint64 `json:"gasLimit"`
}

type MyResult struct {
	TxHash string
}

func InitWorkflow(config *Config, logger *slog.Logger, secretsProvider cre.SecretsProvider) (cre.Workflow[*Config], error) {
	return cre.Workflow[*Config]{
		cre.Handler(cron.Trigger(&cron.Config{Schedule: config.Schedule}), onCronTrigger),
	}, nil
}

func onCronTrigger(config *Config, runtime cre.Runtime, trigger *cron.Payload) (*MyResult, error) {
	logger := runtime.Logger()

	// Step 1: Create and encode a value
	myValue := big.NewInt(123456789)
	logger.Info("Created value to encode", "value", myValue.String())

	uint256Type, err := abi.NewType("uint256", "", nil)
	if err != nil {
		return nil, fmt.Errorf("failed to create type: %w", err)
	}

	args := abi.Arguments{{Type: uint256Type}}
	encodedValue, err := args.Pack(myValue)
	if err != nil {
		return nil, fmt.Errorf("failed to encode value: %w", err)
	}
	logger.Info("Encoded value", "hex", fmt.Sprintf("0x%x", encodedValue))

	// Step 2: Generate report
	reportPromise := runtime.GenerateReport(&cre.ReportRequest{
		EncodedPayload: encodedValue,
		EncoderName:    "evm",
		SigningAlgo:    "ecdsa",
		HashingAlgo:    "keccak256",
	})

	report, err := reportPromise.Await()
	if err != nil {
		return nil, fmt.Errorf("failed to generate report: %w", err)
	}
	logger.Info("Report generated successfully")

	// Step 3: Create EVM client
	evmClient := &evm.Client{
		ChainSelector: config.ChainSelector,
	}

	// Step 4: Submit report onchain
	receiverAddress := common.HexToAddress(config.ReceiverAddress)
	gasConfig := &evm.GasConfig{GasLimit: config.GasLimit}

	writePromise := evmClient.WriteReport(runtime, &evm.WriteCreReportRequest{
		Receiver:  receiverAddress.Bytes(),
		Report:    report,
		GasConfig: gasConfig,
	})

	logger.Info("Submitting report onchain...")

	resp, err := writePromise.Await()
	if err != nil {
		return nil, fmt.Errorf("failed to submit report: %w", err)
	}

	// Check transaction status
	if resp.TxStatus != evm.TxStatusSuccess {
		errorMsg := "unknown error"
		if resp.ErrorMessage != nil {
			errorMsg = *resp.ErrorMessage
		}
		return nil, fmt.Errorf("transaction failed with status %v: %s", resp.TxStatus, errorMsg)
	}

	txHash := fmt.Sprintf("0x%x", resp.TxHash)
	logger.Info("Report submitted successfully", "txHash", txHash, "fee", resp.TransactionFee)

	return &MyResult{TxHash: txHash}, nil
}

func main() {
	wasm.NewRunner(cre.ParseJSON[Config]).Run(InitWorkflow)
}

Configuration file (config.json):

{
  "schedule": "0 */1 * * * *",
  "receiverAddress": "0xYourReceiverContractAddress",
  "chainSelector": 16015286601757825753,
  "gasLimit": 1000000
}

Broadcasting transactions

By default, cre workflow simulate performs a dry run without broadcasting transactions to the network. To execute real onchain transactions, use the --broadcast flag:

cre workflow simulate my-workflow --broadcast --target staging-settings

See the CLI Reference for more details.

Troubleshooting

"failed to submit report" or transaction fails to broadcast

Verify your consumer contract address is correct and deployed on the target chain
Check that you're using the correct chain selector for your target blockchain
Verify network connectivity and RPC endpoint availability

Transaction succeeds but TxStatus is REVERTED

Check the ErrorMessage field for details about why the transaction reverted
Verify your consumer contract implements the IReceiver interface correctly (see Building Consumer Contracts)
Review your consumer contract's onReport() validation logic—it may be rejecting the report
Ensure the report data format matches what your consumer contract expects
Important: A reverted transaction opens a replay window. The forwarder does not mark reverted reports as used, meaning anyone can resubmit the signed report once conditions change. If your workflow takes corrective action after seeing a revert, see Same-chain replay on failure for how to protect against double-execution

"out of gas" error or transaction runs out of gas

Increase the GasLimit in your GasConfig
Check if your consumer contract's onReport() function has unexpectedly complex logic
Review the transaction on a block explorer to see the actual gas used

ReceiverContractExecutionStatus indicates failure

Your consumer contract's onReport() function executed but encountered an error
Review the contract's event logs and error messages on a block explorer
Check that your contract's validation logic (e.g., forwarder checks, workflow ID checks) is correctly configured
Verify the decoded data in your contract matches the expected struct/value format

"invalid receiver address" or address-related errors

Confirm the receiver address is a valid Ethereum address format
Verify the contract is deployed at that address on the target chain
Use common.HexToAddress() to properly convert address strings

Learn more

Onchain Write Overview: Understand all onchain write approaches
Using WriteReportFrom Helpers: Use the simpler all-in-one helper for struct submission
Generating Reports: Single Values: Generate reports for single primitive values
Generating Reports: Structs: Generate reports for struct data
Building Consumer Contracts: Create contracts that can receive reports
EVM Client Reference: Complete API documentation

Submitting Reports Onchain

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