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# Execution & Gas

:::info
Tempo Zones is still in early development and is available for testing purposes on Tempo Testnet only. While Tempo Zones are in this stage, expect breaking changes to the design and implementation. Do not use this in production. If you're interested in working with Tempo Labs as a design partner on the development of Tempo Zones, contact us at [tempo.xyz/contact](https://tempo.xyz/contact).
:::

This page specifies how Tempo Zones handle gas accounting, fee collection, and token management. For deposit and withdrawal flows, see the [bridging specification](/docs/protocol/zones/bridging). For balance visibility and access control rules, see the [accounts specification](/docs/protocol/zones/accounts).

## Fee Tokens

Tempo Zones reuse Tempo fee units and gas accounting. Each transaction includes a `feeToken` field. Any enabled TIP-20 token with USD currency is valid for gas payment. The sequencer accepts all enabled tokens directly, so no Fee AMM is needed.

## Deposit Fees

Deposits charge a fixed processing fee in the deposited token:

```
fee = FIXED_DEPOSIT_GAS × zoneGasRate
```

`FIXED_DEPOSIT_GAS` is fixed at 100,000 gas. The sequencer configures `zoneGasRate` through `ZonePortal.setZoneGasRate()`. The fee is deducted from the deposit amount and paid to the sequencer on Tempo Mainnet.

## Withdrawal Fees

Withdrawals charge a processing fee in the withdrawn token:

```
fee = gasLimit × tempoGasRate
```

The user specifies `gasLimit` to cover processing and any callback execution. The sequencer configures `tempoGasRate` through `ZoneOutbox.setTempoGasRate()`.

## Fixed Gas Costs

All user-facing TIP-20 transfer and approval operations cost exactly 100,000 gas. This removes gas-based information leaks tied to storage state. On a standard EVM chain, gas varies based on whether a transfer writes to a previously empty storage slot, revealing whether the recipient has received tokens before. Fixed costs eliminate that side channel.

| Function | Gas Cost |
|----------|----------|
| `transfer(to, amount)` | 100,000 |
| `transferFrom(from, to, amount)` | 100,000 |
| `transferWithMemo(to, amount, memo)` | 100,000 |
| `transferFromWithMemo(from, to, amount, memo)` | 100,000 |
| `approve(spender, amount)` | 100,000 |

System functions (`systemTransferFrom`, `transferFeePreTx`, `transferFeePostTx`) retain standard gas costs. Only restricted system callers can invoke them, so the gas side channel does not apply.

## Contract Creation Disabled

Tempo Zones currently disable the `CREATE` and `CREATE2` opcodes. Each Tempo Zone runs a fixed set of system contracts and predeploys. Any transaction that attempts contract creation reverts.

## Token Management

![Policy inheritance from mainnet to zone](/learn/zones/diagram-tip20.svg)

The sequencer manages which TIP-20 tokens are available on a Tempo Zone:

| Function | Behavior |
|----------|----------|
| `enableToken(token)` | Enables a TIP-20 token for bridging and gas payment. Irreversible. |
| `pauseDeposits(token)` | Stops new deposits for the token. Withdrawals continue. |
| `resumeDeposits(token)` | Restarts deposits for a previously paused token. |

Once enabled, a token cannot be disabled. This preserves withdrawals for that token, subject to the token's own compliance policy. Tokens on the Tempo Zone use the same address as their Tempo Mainnet counterpart. `ZoneInbox` mints on deposit, `ZoneOutbox` burns on withdrawal. No mechanism exists to create new tokens on the Tempo Zone.