Summary: In 2026, “good” Ethereum smart contracts look different: Pectra (May 7, 2025) raised blob throughput, made calldata-heavy posts more expensive, and introduced EIP‑7702 smart EOAs—while Dencun-era opcodes like MCOPY and transient storage went from “nice to have” to “use them.” This guide distills the practices 7Block Labs implements for startup and enterprise programs today, with concrete code, tooling, and governance choices you can adopt immediately.

Ethereum Smart Contract Best Practices 2026: What’s the Best Approach for Implementing Smart Contracts?

Decision-makers don’t need another intro to “what is a smart contract.” You need a 2026‑calibrated blueprint that aligns with Ethereum’s latest protocol changes, the current toolchain, and the ways real systems fail. Below is the approach we ship on client engagements, with specifics you can copy into your engineering playbook.

1) Establish a 2026 baseline: compiler, EVM version, and toolchain

Compiler/EVM targets
- Target Solidity 0.8.30+ and the Prague EVM by default. Starting May 7, 2025 (Pectra activation), Solidity set Prague as the default EVM version. Pin 0.8.31 if you want the latest storage-layout specifier enhancements for safer upgrades. (soliditylang.org)
- If you must compile for pre‑Pectra networks, explicitly set an older EVM version (e.g., cancun) in build config. (soliditylang.org)
Tooling choice (pragmatic)
- Foundry is the path of least friction for 0.8.30+ and Prague; releases through 2025 made v1.3.x stable for audits, fuzzing, and storage‑layout inspection. (getfoundry.sh)
- Hardhat remains fine for legacy stacks, but its documented “fully supported” Solidity versions currently stop at 0.8.28; expect gaps (e.g., stack traces) on newer compilers unless you accept partial support. (v2.hardhat.org)
Compiler switches we standardize:
- viaIR: true for production builds (better codegen for MCOPY/TSTORE patterns).
- Optimizer: 10k–200k runs depending on call frequency; model with Foundry gas snapshots.
- Model checker (SMT) in CI for critical invariants; 0.8.30 fixed several SMT issues. (soliditylang.org)

2) Code for the protocol that exists now: post‑Pectra and post‑Dencun behaviors

Pectra (mainnet May 7, 2025) made three changes you must reflect in design and cost models:

Calldata floor pricing (EIP‑7623): data‑heavy transactions pay at least 10/40 gas per zero/non‑zero byte, reducing worst‑case EL payload size and nudging data availability to blobs. Your “fallback to calldata” playbook is now wrong except during extreme blob spikes. (eips.ethereum.org)
Blob throughput increase (EIP‑7691): target blobs per block doubled 3→6; max 6→9 with a retuned base‑fee update fraction. This changes your blob budget curves and fee alerts. (eips.ethereum.org)
Mainnet activation details (Pectra): confirmed epoch 364032 at 10:05:11 UTC on May 7, 2025. Use this for gating chain feature flags in CI and simulation. (blog.ethereum.org)

Dencun remains foundational:

EIP‑4844 blob transactions: Type‑3 tx includes max_fee_per_blob_gas and blob_versioned_hashes; price is an independent EIP‑1559‑like market. For batchers and data posts, target blobs first; only reroute to calldata when blob base fee exceeds app‑specific thresholds. (eips.ethereum.org)
EIP‑4788 beacon roots: trust‑minimized access to the beacon chain via the on‑chain beacon roots contract at 0x000F3d…Beac02—critical for bridges, staking pools, and restaking designs that previously depended on oracles. (eips.ethereum.org)

Two Dencun opcodes are now standard practice:

EIP‑1153 transient storage (TSTORE/TLOAD): for reentrancy locks, per‑tx allowances, and metadata propagation through delegatecall without permanent SSTORE costs. Use the transient variant of ReentrancyGuard. (eips.ethereum.org)
EIP‑5656 MCOPY: prefer memory‑to‑memory copies over identity precompile; it’s dramatically cheaper for bulk copies in parsers/routers. (eips.ethereum.org)

Finally, your upgrade and deploy strategies must honor:

EIP‑6780 SELFDESTRUCT: you can’t rely on self‑destruct‑and‑redeploy patterns anymore except in the same transaction as creation; use proxies or diamonds instead. (eips.ethereum.org)

3) Choosing your account model in 2026: 7702, 4337, or both?

EIP‑7702 smart EOAs (Type‑4 “set‑code” tx): an EOA can temporarily delegate execution to contract logic for a transaction, then revert to a normal EOA. This preserves the user’s familiar address and enables batching/sponsored flows without deploying a separate smart account. Libraries and SDKs (e.g., ethers v6.14) already support 7702. (eips.ethereum.org)
ERC‑4337 smart accounts: mature rails for sponsored gas, batching, aggregators, and paymasters. The shared mempool launched across major L2s and mainnet to improve inclusion/censorship resistance; follow ERC‑7562 validation‑scope rules. (etherspot.io)
Modular accounts via ERC‑7579 + registries via ERC‑7484: 7579 is converging as the “portable modules” standard (validators, executors, hooks); a registry pattern (7484) lets accounts query security attestations before loading third‑party modules. This reduces vendor lock‑in risk for enterprise wallets. (eips.ethereum.org)

Our 2026 recommendation

For consumer wallets or migrations from EOAs: adopt a “7702‑front, 4337‑rails” approach—smart features with the same address via 7702, while still using 4337 bundlers/paymasters when you need sponsorship, sessions, or aggregations. Ensure your bundler providers participate in the shared mempool for inclusion guarantees. (etherspot.io)

4) Practical code: using transient storage, MCOPY, blobs, and the beacon root

Transient reentrancy guard (Solidity, OpenZeppelin 5.1+)

// SPDX-License-Identifier: MIT
pragma solidity ^0.8.30;

import {ReentrancyGuardTransient} from "@openzeppelin/contracts/utils/ReentrancyGuardTransient.sol";

contract Vault is ReentrancyGuardTransient {
    mapping(address => uint256) public balances;

    function deposit() external payable {
        balances[msg.sender] += msg.value;
    }

    function withdraw(uint256 amt) external nonReentrant {
        require(balances[msg.sender] >= amt, "insufficient");
        balances[msg.sender] -= amt;
        (bool ok,) = msg.sender.call{value: amt}("");
        require(ok, "xfer fail");
    }
}

Use ReentrancyGuardTransient when EIP‑1153 is live (Ethereum mainnet, major L2s) to cut SSTORE costs and eliminate refund constraints. (docs.openzeppelin.com)

Fast memory copies with MCOPY (inline assembly)

function _copy(bytes memory src) internal pure returns (bytes memory dst) {
    dst = new bytes(src.length);
    assembly {
        // mcopied len from src+32 to dst+32
        let len := mload(src)
        // dst data ptr = add(dst, 32); src data ptr = add(src, 32)
        mcopy(add(dst, 32), add(src, 32), len)
    }
}

MCOPY reduces copy gas from ~96 gas/word down to the W_copy schedule and avoids precompile overhead; for router payloads and calldata slicing this adds up quickly. (eips.ethereum.org)

Reading the beacon root (EIP‑4788)

interface IBeaconRoots {
    function get(bytes32 tsBE) external view returns (bytes32 root);
}

address constant BEACON_ROOTS = 0x000F3df6D732807Ef1319fB7B8bB8522d0Beac02;

function beaconRootAt(uint256 ts) internal view returns (bytes32) {
    // input must be 32‑byte big‑endian timestamp
    bytes32 tsBE = bytes32(uint256(ts));
    return IBeaconRoots(BEACON_ROOTS).get(tsBE);
}

Design oracles/bridges to verify against the canonical beacon root rather than trusting external relays where feasible. (eips.ethereum.org)

Sending a blob transaction (TypeScript with a modern client)

import { createWalletClient, http, parseEther } from 'viem';
import { mainnet } from 'viem/chains';
// Example: viem exposes blob tx helpers.
const client = createWalletClient({ chain: mainnet, transport: http() });

const hash = await client.sendTransaction({
  to: '0xfeed...beef',
  value: parseEther('0'),
  data: '0x', // EVM can't access blob data; business logic uses commitments
  blobs: [new Uint8Array(128 * 1024)], // one 128 KiB blob
  maxFeePerBlobGas: 3_000_000n,        // tune with your blob budget policy
});

Ensure your infra estimates blob base fees and guards maxFeePerBlobGas per chain. Blob fields are distinct from EVM gas fields, and blob gas is burned up front. (eips.ethereum.org)

5) Upgradeability that ages well

Prefer UUPS proxies (ERC‑1822/1967) for single‑contract upgrades; Transparent proxies for admin‑isolated control; Beacons for N‑instance fleets. Use namespaced storage (standard in OZ v5+) and lock upgrades behind AccessManager or a timelocked multisig. (docs.openzeppelin.com)
Validate storage layouts in CI with OpenZeppelin Upgrades Core/CLI; annotate implementations with @custom:oz-upgrades to force checks. Foundry and Hardhat plugins both support deploy/upgrade flows. (docs.openzeppelin.com)
Remember historical footguns: uninitialized UUPS implementations (fixed since 4.3.2) still appear in legacy code audits—initialize logic contracts and gate _authorizeUpgrade. (github.com)
Solidity 0.8.31 extended storage layout specifiers, enabling more explicit slot planning in complex systems (diamonds/modules). Use it for critical registries to make layout drift explicit. (soliditylang.org)

Minimal UUPS base (Upgradeable flavor):

// SPDX-License-Identifier: MIT
pragma solidity ^0.8.31;

import {Initializable} from "@openzeppelin/contracts-upgradeable/proxy/utils/Initializable.sol";
import {UUPSUpgradeable} from "@openzeppelin/contracts-upgradeable/proxy/utils/UUPSUpgradeable.sol";
import {AccessManaged} from "@openzeppelin/contracts-upgradeable/access/manager/AccessManagedUpgradeable.sol";

contract Core is Initializable, UUPSUpgradeable, AccessManaged {
    uint256 public x;

    function initialize(address authority) public initializer {
        __UUPSUpgradeable_init();
        __AccessManaged_init(authority);
    }

    function set(uint256 v) external restricted { x = v; }

    function _authorizeUpgrade(address) internal override restricted {}
}

Gate upgrades with AccessManager roles and optional delays to create a reliable “break‑glass” window. (docs.openzeppelin.com)

6) Gas and data‑cost playbook (updated for 7623/7691/4844)

Prefer blobs for DA. Only failover to calldata on sustained blob base‑fee spikes; reprice after 7691’s asymmetric response (≈+8.2% per full block, ≈−14.5% per empty block) and put new alert thresholds in your batcher. (eips.ethereum.org)
Rework calldata‑heavy endpoints (Merkle proofs, orderbooks) to post in blobs and reference commitments on‑chain; if you must pass data to EVM, compress to bytes32‑keyed maps or bitpacking.
Use custom errors, events instead of return strings; pack state into tightly‑fit slots; prefer bytes32 over string; favor unchecked math in hot loops with explicit bounds checks at the perimeter.
Adopt MCOPY and TSTORE/TLOAD in libraries where appropriate; OZ v5.1 adds transient ReentrancyGuard and packing utilities to make this safer. (docs.openzeppelin.com)
Keep a per‑chain “max_fee_per_blob_gas” guardrail map and rotate budgets when forks alter blob schedule parameters per EIP‑7840. (eip.info)

7) Security program: what auditors expect in 2026

Static + property testing
- Slither ≥0.11.0 adds detectors for transient storage patterns, L2 predeploy deprecations, and oracle checks. Run it in CI with allowlists. (github.com)
- Fuzz and invariant tests in Foundry; run across EVM versions (cancun vs prague) to catch opcode‑cost or semantic shifts.
4337 readiness
- Track EntryPoint versions and mempool stance; the EF launched a dedicated bug bounty for 4337/7562; shared mempool improves inclusion guarantees—design for it. (docs.erc4337.io)
Operational risk is trending up in size, not count:
- 2025 saw ~$3.4B stolen with concentration in a few mega‑breaches; wallet compromises remain a significant slice. Your key management and deployment ops are now as important as your Solidity. (chainalysis.com)
Admin/ops guardrails
- Use multisig/timelock for upgrades; split deployer and operator roles; wire canary/kill‑switches (Pausable) sparingly and document their triggers and scope. Prefer AccessManager to centralize permissions with delays. (docs.openzeppelin.com)

8) Cross‑chain: choose boring bridges and isolate failure domains

If you must go cross‑chain, prefer production‑proven managed interoperability like Chainlink CCIP. Adopt their patterns: decouple message reception from core business logic, enforce admin hygiene, soak‑test rate limits, and operate monitors for delays/outages. Track live chain/token support via CCIP Directory when making go/no‑go decisions. (docs.chain.link)

Enterprise signals in 2025–2026 (ecosystem scale and vendor maturity) also improved CCIP’s case (multi‑VM coverage, Solana/Aptos support), but your contracts must still assume messages can be delayed or dropped; build compensating controls. (blog.chain.link)

9) 7702 + 4337 implementation notes for product leads

Wallet UX: 7702 lets users keep addresses while gaining smart features; pair with 4337 for sponsored flows and session keys. Instrument telemetry per EntryPoint version and shared mempool participation to detect censorship or vendor lock‑in. (eips.ethereum.org)
Standards convergence: target ERC‑7579 accounts and module ecosystems; check module attestations via an ERC‑7484 registry before installation to reduce third‑party module risk. (eips.ethereum.org)

10) What to retire in 2026

“Reset by selfdestruct + CREATE2” upgradability: broken by EIP‑6780 semantics; migrate to UUPS/Transparent/Beacon proxies. (eips.ethereum.org)
Calldata as primary DA rail for rollups: after EIP‑7623 + 7691, blobs are the default; rework cost models and fallbacks. (eips.ethereum.org)
Single‑sig owner upgrade keys: move to AccessManager‑backed roles and timelocked multisig approvals. (docs.openzeppelin.com)
Old Hardhat stacks pinned <0.8.29 for new deployments: move to Foundry or confirm Hardhat support per‑version if you need Prague features. (v2.hardhat.org)

11) Deployment checklist (copy/paste)

Build
- solc 0.8.30+ (Prague), viaIR on; optimizer tuned per profile. (soliditylang.org)
- Foundry v1.3.x; forge coverage/fuzz/invariant suites green. (getfoundry.sh)
- Slither ≥0.11.0 CI run with fail‑on‑new finding; custom detectors where app‑specific. (github.com)
Gas/DA
- Blob posting path with guardrails for max_fee_per_blob_gas; alerting adjusted for 6/9 target:max; calldata fallback thresholds documented per chain. (eips.ethereum.org)
Upgrades
- UUPS/Transparent decided; OZ Upgrades “validate” passed; storage layout diff reviewed and pinned in CI. (docs.openzeppelin.com)
AA
- If 4337: EntryPoint version map per chain; shared mempool provider SLAs; paymaster policy documented; 7562 checks in place. (eips.ethereum.org)
- If 7702: wallet/sdk supports Type‑4 set‑code tx; auth list policy; fallbacks when 7702 unsupported. (eips.ethereum.org)
Ops
- Admin roles under multisig/timelock; EIP‑4788 used where appropriate; monitors for CCIP (if cross‑chain). (eips.ethereum.org)

Closing thought

The “best approach” in 2026 is less about a single framework and more about aligning code, costs, and operations to Ethereum’s post‑Pectra realities: blobs first, calldata last; smart EOAs when it helps UX, smart accounts when you need programmability; transient storage and MCOPY for efficiency; and boring, auditable upgrade paths. If your roadmap bakes in these specifics, your stack will age well into the next set of upgrades (EOF and PeerDAS when they land).

References and further reading

Pectra mainnet announcement and activation time; overview on ethereum.org. (blog.ethereum.org)
EIPs: EIP‑7623 (calldata floor), EIP‑7691 (blob throughput), EIP‑4844 (blob tx), EIP‑4788 (beacon root), EIP‑1153 (transient storage), EIP‑5656 (MCOPY), EIP‑6780 (SELFDESTRUCT), EIP‑7702 (smart EOAs). (eips.ethereum.org)
Solidity 0.8.30/0.8.31 releases (Prague default; storage layout improvements). (soliditylang.org)
OpenZeppelin Contracts v5 docs (ReentrancyGuardTransient, cryptography utilities, AccessManager), OZ Upgrades Plugins. (docs.openzeppelin.com)
ERC‑4337 ecosystem: shared mempool launch; ERC‑7562 mempool/validation rules; community docs and bug bounty. (etherspot.io)
Chainlink CCIP best practices and directory (live networks/tokens). (docs.chain.link)
Slither 0.11.0 release notes. (github.com)
Risk landscape 2025 (Chainalysis). (chainalysis.com)