What is a transaction
A transaction is a signed message submitted to a blockchain that changes its state — transferring tokens, calling a contract function, or deploying a new contract. Once included in a block, transactions are permanent and irreversible.
When you inspect an EVM transaction on a block explorer, its recorded parameters show everything that single submission includes:
| Field | Description |
|---|
from | The account initiating and paying gas |
to | The recipient address or contract |
value | Amount of native token to send (zero for most contract calls) |
data | Encoded function call for contracts; empty for plain transfers |
gas limit | Maximum computation the sender is willing to pay for |
maxFeePerGas | Maximum total gas price the sender is willing to pay (EIP-1559) |
maxPriorityFeePerGas | Tip paid to the block producer to prioritize inclusion (EIP-1559) |
nonce | A sequential counter that prevents the same transaction from being submitted twice |
Most modern EVM transactions use the EIP-1559 fee format. Legacy transactions with a single gasPrice field are still valid but less common.
Transaction hash
Every submitted transaction receives a unique transaction hash (tx hash) — a hex string like 0x4a3f8b2c.... This is how you look up a transaction on a block explorer:
| Chain | Block explorer |
|---|
| Ethereum mainnet | etherscan.io |
| Ethereum Sepolia | sepolia.etherscan.io |
| Base mainnet | basescan.org |
| Base Sepolia | sepolia.basescan.org |
| Polygon PoS | polygonscan.com |
| Arbitrum One | arbiscan.io |
| Optimism | optimistic.etherscan.io |
| BNB Smart Chain | bscscan.com |
| Avalanche C-Chain | snowtrace.io |
| Solana mainnet | solscan.io |
Gas fees
On-chain transactions require a fee to compensate the network for computation and storage. The fee model differs between EVM chains and Solana.
EVM chains
Gas is the unit of computational work. Every operation costs a fixed amount of gas, and the total fee depends on how much computation the transaction requires:
Transaction fee (EVM) = gas used × gas price (in Gwei)
| Component | Field | Description |
|---|
| Base fee | — | Set by the protocol; burned, not paid to validators |
| Priority fee | maxPriorityFeePerGas | Tip paid to the block producer to prioritize inclusion |
maxFeePerGas field caps the total amount the sender is willing to pay. Any difference between maxFeePerGas and the actual base fee + priority fee is refunded.
Gas prices fluctuate with network congestion. During high activity, fees can spike significantly.
Solana
Solana uses a different fee model with two components:
| Component | Description |
|---|
| Base fee | A flat fee per signature, charged in lamports (1 SOL = 1,000,000,000 lamports) |
| Priority fee | An optional fee per compute unit to increase processing priority during congestion |
Transaction fee (Solana) = (number of signatures × base fee per signature) + (compute units × compute unit price)
Transaction lifecycle in Cobo Agentic Wallet
This lifecycle is specific to Cobo Agentic Wallet. Other products and platforms may handle transaction submission and signing differently.
Submit → Policy validation → MPC signing → Broadcast → Included in block → Confirmed
- Policy validation — the policy engine (governed by the pact) checks the transaction. If it violates a policy, it is blocked before reaching the network.
- MPC signing — if it passes, the transaction is co-signed: the agent and Cobo for agent-initiated transactions; the app and Cobo for app-initiated transactions.
- Broadcast — the signed transaction is sent to the network, included in a block, and confirmed.
Transaction finality
TTransactions are not final the moment they are submitted. They must be included in a block and confirmed by subsequent blocks. For high-value operations, waiting for additional confirmations beyond the first provides stronger settlement guarantees.
| Chain | Time to first confirmation | Practical finality |
|---|
| Ethereum mainnet | ~12 seconds | ~3 minutes (15 blocks) |
| Base mainnet | ~2 seconds | ~10 seconds |
| Polygon PoS | ~2 seconds | ~10 seconds |
| Solana mainnet | ~400 milliseconds | ~2 seconds |
| Ethereum Sepolia | ~12 seconds | ~3 minutes |
| Base Sepolia | ~2 seconds | ~10 seconds |
