# Refactor a legacy module in Nuxt with Atlas in 2026

> Atlas helps Nuxt developers safely refactor legacy modules by mapping public surfaces, pinning behavior with `vitest`, and applying changes incrementally.

Refactoring a legacy Nuxt module without breaking existing callers is achievable with Atlas, which uses `lsp` to map public surfaces, `vitest (@nuxt/test-utils)` to pin behavior, and `apply_patch` for structural changes, ensuring your Nuxt 3 application remains stable and performant in 2026.

## Key takeaways

- Atlas uses `lsp` to comprehensively map Nuxt module public surfaces and all their callsites.
- `vitest (@nuxt/test-utils)` via `pnpm test` establishes a critical behavioral baseline for Nuxt refactors.
- `apply_patch` ensures safe, incremental changes to Nuxt `.vue` and `.ts` files, failing on drift.
- Atlas integrates with `pnpm` and `prettier` for a complete Nuxt development workflow.
- Permission-gated tool calls and unified diffs provide full control and transparency over Nuxt code changes.
- `todowrite` helps track and complete all callsite migrations in complex Nuxt refactors.

## How Atlas Maps Nuxt Module Public Surfaces

In 2026, Atlas leverages the `lsp` tool's `documentSymbol` operation to precisely map the public surface of any Nuxt module. This process identifies every exported function, component, or composable, ensuring that all 1,000+ potential callsites are accounted for before any refactoring begins.

To prevent silent breakage, Atlas first uses the `lsp` tool to understand the module's public API. It performs a `documentSymbol` operation on the target Nuxt module file, which enumerates all exported symbols. For each identified symbol, Atlas then executes `findReferences` to locate every single callsite across your Nuxt project. This includes usages within `pages/` for file-based routing, `composables/` for auto-imports, and `server/api/` for Nitro handlers. This comprehensive mapping ensures that Atlas has a complete picture of the module's dependencies and impact, a critical first step before any code modification.

## Pinning Nuxt Module Behavior with `vitest (@nuxt/test-utils)`

Before any structural changes, Atlas pins the existing behavior of your Nuxt module by running its tests. Using `bash` to execute `pnpm test`, Atlas records a green baseline from `vitest (@nuxt/test-utils)`, ensuring that the module's functionality is preserved throughout the refactoring process in 2026.

A core principle of safe refactoring is to establish a behavioral baseline. Atlas achieves this by using the `bash` tool to run your existing Nuxt tests. Specifically, it executes `pnpm test`, which invokes `vitest (@nuxt/test-utils)` as configured in your `nuxt.config.ts`. Atlas records the output, confirming that all tests pass before any modifications are made. This 'green baseline' serves as a critical reference point, allowing Atlas to verify that each subsequent change maintains the module's original behavior, preventing regressions in your Nuxt application.

## Incremental Refactoring and Safety in Nuxt

Atlas refactors Nuxt modules incrementally using `apply_patch`, ensuring each change is small and verifiable. After every hunk lands, Atlas re-runs `pnpm test` to confirm behavior, and uses `todowrite` to track any remaining 1-to-1 callsite migrations, providing robust safety in 2026.

Structural changes are applied using Atlas's `apply_patch` tool. This tool is designed for safety: it anchors each hunk on context lines and `old_lines`, and will fail with 'Failed to find context' if the target Nuxt `.vue` or `.ts` file has drifted since the patch was generated. This prevents applying changes to an outdated file. Crucially, after each individual hunk is successfully applied, Atlas immediately re-runs `pnpm test` via `bash` to verify that the module's behavior remains unchanged. For complex refactors involving callsite migrations, Atlas uses `todowrite` to maintain a list of remaining tasks, ensuring no callsite is overlooked and preventing a partially migrated module from being mistaken for a finished one.

## Reviewing and Committing Nuxt Refactors with Atlas

Atlas provides a transparent review process for all Nuxt refactoring changes. Every file edit generates a unified diff for your approval, and all tool calls are permission-gated. In 2026, Atlas can also run `prettier` over touched `.vue` and `.ts` files, ensuring code style consistency before committing.

Transparency and control are paramount. Atlas computes a unified diff for every file edit, presenting it for your approval before writing any changes to your Nuxt project. Furthermore, every Atlas tool call, including `lsp` or `apply_patch`, is permission-gated against allow, ask, and deny rules, giving you granular control over its actions. After structural changes, Atlas can automatically run `prettier` over the touched `.vue` and `.ts` files, ensuring your Nuxt project's code style is maintained. Once approved, Atlas can stage the changes and create commits on your behalf, integrating direct with your `git` workflow and providing snapshots for easy rollback if needed.

## Steps

1. Run Atlas in your Nuxt project with a `nuxt.config.ts` present.
2. Ask Atlas to map the module's public surface: `lsp documentSymbol` on the module file, then `findReferences` on each exported symbol to enumerate all callsites in `pages/`, `composables/`, and `server/api/`.
3. Pin the module's current behavior: Use `bash` to run `pnpm test` with `vitest (@nuxt/test-utils)` and record the green baseline.
4. Instruct Atlas to restructure the module using `apply_patch` for structural changes, ensuring it anchors on context lines.
5. After each `apply_patch` hunk lands, use `bash` to re-run `pnpm test` to verify behavior immediately.
6. Track any remaining callsite migrations with `todowrite` to ensure a complete refactor.
7. Review the unified diffs provided by Atlas for all `.vue` and `.ts` file changes.
8. Allow Atlas to run `prettier` over the touched `.vue` and `.ts` files to maintain code style.
9. Approve the changes, and let Atlas stage and create a `git` commit on your behalf.

## FAQ

### How does Atlas prevent breaking Nuxt auto-imports during refactoring?

Atlas uses `lsp`'s `findReferences` to identify all usages of auto-imported `composables/` or `utils/` functions before any changes. This ensures every callsite is accounted for and migrated correctly during the refactor.

### Can Atlas refactor server-side Nuxt 3 Nitro handlers?

Yes, Atlas understands the Nuxt 3 server/client split. It can refactor `server/api/` Nitro handlers, mapping their public API surface and ensuring existing tests with `vitest (@nuxt/test-utils)` remain green throughout the process.

### What if Atlas tries to apply a patch to a Nuxt file that has changed?

Atlas's `apply_patch` tool anchors on context lines. If a Nuxt `.vue` or `.ts` file has drifted, `apply_patch` will fail with 'Failed to find context', preventing unintended changes to a stale file and requiring manual intervention.

### How does Atlas ensure my Nuxt project's code style is maintained?

After making edits to Nuxt `.vue` or `.ts` files, Atlas can be instructed to run `prettier` over the touched files. This ensures your project's formatting standards are consistently applied, maintaining code style without manual effort.

### Does Atlas support Nuxt 3's file-based routing when refactoring?

Yes, Atlas is aware of Nuxt's file-based routing in `pages/`. When refactoring components or composables used within routes, Atlas uses `lsp` to track dependencies and ensure no routes are inadvertently broken or misconfigured.

### How does Atlas handle `pnpm` workspaces in a Nuxt monorepo?

Atlas operates within the project context. If your Nuxt project uses `pnpm` workspaces, Atlas will execute `pnpm` commands (like `pnpm test`) correctly within that environment, respecting your monorepo setup and ensuring proper dependency resolution.

### Can Atlas help move a `fetch` call into `useAsyncData` in Nuxt?

Yes, Atlas can assist with Nuxt-specific refactors like moving a `fetch` call out of a component into `useAsyncData`. This ensures the data fetching runs once during SSR instead of twice, optimizing your Nuxt application's performance.

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Canonical HTML: https://runatlas.sh/resources/stacks/refactor-a-legacy-module-in-nuxt
Source of truth: aeo_pages row `/resources/stacks/refactor-a-legacy-module-in-nuxt` (segment: Stacks) (this file is generated from it, never hand-edited).
Licence: Atlas is proprietary with a free core. It is not open source and there is no public source repository.