Automating Web3 Frontend Migration in One Command

The Ticking Time Bomb in Every dApp's package.json

Every production dApp built in 2022–2023 shares the same lurking technical debt: a tightly coupled trio of outdated dependencies — wagmi v1, ethers.js v5, and RainbowKit v1. These libraries were once the gold standard of the Web3 frontend stack. Today, they are a migration nightmare waiting to happen.

The core issue is deceptively simple. wagmi v2 dropped ethers.js entirely in favor of viem. RainbowKit v2 requires wagmi v2. Migrating one without the others breaks everything. And yet, every team that tackles this migration does it the same painful way: manually, file by file, over days or weeks, with a non-trivial chance of introducing subtle bugs into production wallet-connection flows.

Now, a growing number of developers are turning to AI-powered codemods and automated migration scripts to collapse that multi-week process into a single command.

Why This Migration Is Uniquely Painful

Unlike a typical library version bump, the wagmi v1 → v2 migration is effectively a paradigm shift. ethers.js and viem have fundamentally different APIs. Where ethers uses ethers.utils.formatEther(), viem uses formatEther() as a standalone import. Where ethers relies on BigNumber, viem uses native bigint. Provider and signer abstractions vanish entirely in viem's model, replaced by 'public clients' and 'wallet clients.'

This means every file that touches on-chain data — every hook, every utility function, every contract interaction — needs to be rewritten. In a medium-sized dApp, that can mean touching 50 to 200 files.

RainbowKit compounds the problem. Its v2 release changed configuration patterns, connector setup, and theming APIs. The getDefaultWallets function was replaced, chain configurations moved to a new structure, and the entire provider wrapper changed shape.

Manual migration introduces three major risks:

• Silent type mismatches — BigNumber vs bigint errors that TypeScript may not catch without strict configuration
• Broken wallet flows — connector API changes that only surface when users try to connect MetaMask or WalletConnect in production
• Incomplete replacements — stray ethers.js imports that compile fine but fail at runtime

The Automation Approach: Codemods Meet LLMs

The solution emerging from the developer community combines two technologies: traditional AST-based codemods (think jscodeshift) and large language model-assisted code transformation.

Here is how the automated pipeline typically works:

Step 1: Dependency Graph Analysis

The script first parses package.json and maps every file that imports from wagmi, ethers, or @rainbow-me/rainbowkit. This produces a directed dependency graph showing exactly which files need transformation and in what order.

Step 2: AST-Based Deterministic Transforms

For well-defined, mechanical changes — like swapping ethers.utils.formatEther(value) to formatEther(value) from viem, or converting BigNumber.from(x) to BigInt(x) — an AST-based codemod handles the transformation deterministically. No LLM hallucination risk. No ambiguity.

Common deterministic transforms include:

• Rewriting all import { ... } from 'ethers' statements to their viem equivalents
• Converting useContractRead / useContractWrite hooks to wagmi v2's useReadContract / useWriteContract
• Updating RainbowKit's getDefaultWallets to the v2 connectorsForWallets pattern
• Replacing chain imports from wagmi/chains with the new viem/chains source

Step 3: LLM-Assisted Contextual Rewrites

For complex, context-dependent transformations — like refactoring a custom hook that wraps multiple ethers.js provider calls into viem's publicClient pattern — the pipeline delegates to an LLM (typically GPT-4 or Claude) with a carefully constrained prompt.

The key insight is that the LLM is never given free rein. It receives:

• The original file
• A strict mapping table of ethers → viem API equivalences
• The target file's type signature constraints
• Instructions to preserve all business logic and only modify infrastructure calls

This hybrid approach — deterministic transforms for mechanical changes, LLM-assisted rewrites for contextual ones — achieves what neither tool can do alone.

Step 4: Automated Validation

After transformation, the script runs a three-layer validation:

1. TypeScript compilation — catches type mismatches immediately
2. Import verification — ensures zero remaining ethers.js imports exist
3. Smoke tests — automated wallet connection and contract read tests using a local Anvil fork

Real-World Results

Developers who have adopted this approach report dramatic time savings. A migration that previously took a senior frontend engineer 2–3 weeks can be completed in under a day, with most of the time spent on review rather than writing code.

One open-source implementation circulating on GitHub claims to handle the full migration for a typical dApp with a single npx migrate-web3-stack command. While exact numbers vary by project complexity, early adopters report:

• 85–95% of transformations handled automatically by the AST codemod layer
• 3–8% of files requiring LLM-assisted contextual rewrites
• Under 2% of files needing manual intervention, typically for highly custom contract interaction patterns

The Broader Implications for AI-Assisted Code Migration

This Web3 migration use case is a compelling proof-of-concept for a much larger trend: using LLMs not as code generators, but as code migrators.

Traditional codemods excel at mechanical, pattern-based transforms but fall apart when context matters. LLMs excel at understanding context but hallucinate on exact syntax. The hybrid approach — using AST transforms as the backbone and LLMs as a contextual 'fill-in' layer — may become the standard pattern for large-scale code migrations across the industry.

Companies like Grit.io, Codemod.com, and Amazon (with its Q Code Transformation tool for Java upgrades) are already investing heavily in this space. The Web3 frontend migration is simply one of the most acute, well-defined examples of the problem.

What Teams Should Do Now

For any team still running wagmi v1 and ethers.js v5 in production, the window for a comfortable migration is closing. Ecosystem tooling, documentation, and community support increasingly assume v2. Security patches for v1 dependencies will eventually stop.

Here is a practical checklist:

1. Audit your dependency graph — identify every file importing from the legacy trio
2. Set up a local Anvil fork — you need deterministic on-chain state for testing
3. Run deterministic codemods first — handle the mechanical 85% before involving any LLM
4. Use LLM-assisted transforms with strict constraints — never let the model improvise on contract ABIs or chain configurations
5. Validate with TypeScript strict mode — turn on strict: true in tsconfig if you have not already
6. Test wallet connections across browsers — MetaMask, WalletConnect, and Coinbase Wallet all behave differently

Outlook

The days of multi-week manual migrations for well-understood API changes are numbered. As AI-assisted codemod tooling matures, the expectation will shift: if a library author ships a breaking change, they should also ship a codemod — ideally one that leverages LLMs for the edge cases.

For the Web3 frontend ecosystem specifically, the wagmi v1 → v2 migration is the canary in the coal mine. Teams that automate it now will be better positioned for the next inevitable wave of breaking changes. Those that keep putting it off are accumulating technical debt that compounds with every passing month.