Tenderly Debugger: Setup, Tracing, and Debugging EVM Transactions

A transaction fails with execution reverted — no reason string, no readable log. Or it consumes three times more gas than expected, and it's unclear why. Or a multisig executed incorrectly, but which exact call caused it remains a mystery. console.log doesn't work in Solidity on mainnet, and viewing raw opcodes in Etherscan is painful. This scenario is the daily bread of smart contract developers. In our practice, about 40% of support requests relate to unclear reverts. Manual trace analysis takes from one hour to half a day. Tenderly Debugger cuts that to 2-3 minutes. According to Tenderly, teams save up to 90% of time on error finding. In one case, we reduced gas consumption by 25% after optimization found via tracing.

How Tenderly Debugger Helps Find the Cause of Errors

For each transaction, Tenderly builds:

• Execution trace — step-by-step opcode execution with stack and memory state
• Call tree — tree of nested calls (internal calls, delegatecall, staticcall)
• State changes — which storage slots changed and from which value to which
• Event logs — all emitted events, including from nested calls
• Gas breakdown — how much gas each call in the tree consumed

For contracts with verified source code, the debugger shows Solidity lines instead of opcodes. This is tens of times faster than manually searching for errors. For example, when debugging a reentrancy attack, Tenderly shows the exact number of recursive withdraw() calls and the amount of ETH leaked per iteration.

Example: Debugging a Reverted Transaction

A common scenario: a user reports a failed transaction, hash is known, but reason is empty (old contract, require without message). Paste the hash into Tenderly — immediately see the line in the source where the revert occurred and the current variable values. In one project, we found in 2 minutes a slippage calculation error that caused a 0.5% liquidity loss on every swap.

Setting Up a Project in Tenderly

Adding a Contract

npm install -g @tenderly/cli tenderly login tenderly init # creates tenderly.yaml in the project 

For Hardhat projects, you can install a plugin that automatically pushes artifacts:

// hardhat.config.js require("@tenderly/hardhat-tenderly"); module.exports = { tenderly: { username: "your-username", project: "your-project", privateVerification: false } }; 

After that, running npx hardhat run scripts/deploy.js --network mainnet automatically verifies contracts in Tenderly.

Fork for Debugging

Tenderly Fork — a snapshot of network state at a specific block. You can send transactions without risking funds and see full tracing:

const axios = require('axios'); const response = await axios.post( `https://api.tenderly.co/api/v1/account/${username}/project/${project}/fork`, { network_id: "1", block_number: 19500000 }, { headers: { 'X-Access-Key': process.env.TENDERLY_ACCESS_KEY } } ); const forkId = response.data.simulation_fork.id; const forkRpc = `https://rpc.tenderly.co/fork/${forkId}`; 

Connect to forkRpc as a regular JSON-RPC — all transactions are recorded and available for analysis.

Why Tenderly Debugger Is Better Than Local Debugging

Additionally, Tenderly allows comparing gas costs of different approaches. For example, a typical transfer costs ~21000 gas, while a swap via Uniswap V3 costs from 80000 to 150000 gas depending on slippage.

These numbers help estimate where suboptimal calls are hidden.

Simulation API for Testing

The Simulation API allows simulating transactions before sending them to the network. We use it in CI for automated regression:

const simulation = await axios.post( `https://api.tenderly.co/api/v1/account/${username}/project/${project}/simulate`, { network_id: "1", from: "0xSenderAddress", to: "0xContractAddress", input: contractInterface.encodeFunctionData("transfer", [recipient, amount]), gas: 200000, gas_price: "20000000000", value: "0", save: true }, { headers: { 'X-Access-Key': process.env.TENDERLY_ACCESS_KEY } } ); console.log(simulation.data.transaction.status); console.log(simulation.data.transaction.gas_used); 

Integration of Simulation API into CI pipeline: obtain API key, create endpoint, add a step in GitHub Actions or GitLab CI, check status and gas. If parameters exceed limits, the pipeline fails.

What’s Included in Our Tenderly Turnkey Setup

• Full verification of all project contracts in Tenderly
• Setup of fork environment for debugging and testing
• Integration of Simulation API into CI/CD
• Documentation on usage and configuration
• Team training (1-2 sessions)
• Support for one month after deployment

We are a team with 5 years of experience in blockchain development, having completed over 20 smart contract and DApp projects. Our expertise guarantees fast and quality setup.

Timeframe Estimates

Basic setup with verification and Hardhat plugin connection: 1-2 days. Extended configuration with fork, Simulation API, and monitoring: up to 5 days.

To assess the capabilities of Tenderly for your project get a consultation — contact us. Order a turnkey debugger setup and get full transaction transparency.