angular-signal-forms-migration-mcp

An MCP server that helps an AI coding agent migrate Angular Reactive Forms to Angular Signal Forms.

It finds the Reactive Forms constructs in your codebase, separates the safe mechanical renames from the ones that need a human decision, and hands back before→after recipes that are verified against a real Angular release rather than written from memory.

Install

Requires Node.js 20+. Nothing to clone — npx fetches it on demand.

claude mcp add signal-forms-migration -- npx -y angular-signal-forms-migration-mcp@latest

Or add it to any MCP client config:

{
  "mcpServers": {
    "signal-forms-migration": {
      "command": "npx",
      "args": ["-y", "angular-signal-forms-migration-mcp@latest"]
    }
  }
}

@latest makes npx re-resolve on every launch, so restarting your editor picks up new releases. Without it, npx keeps serving whichever version it cached first — repoint the config at @latest, or clear the cache with npm cache clean --force.

The server also checks for a newer version once a day and writes a one-line notice to stderr. It is throttled, times out after 2 seconds, never touches stdout, and stays silent on any failure. To turn it off, add "env": { "SIGNAL_FORMS_MCP_NO_UPDATE_CHECK": "1" } to the config block above. To see what is actually running:

npx angular-signal-forms-migration-mcp@latest --version

[!IMPORTANT] Do not npm install this into your Angular app. It is a standalone process your editor spawns, not a library your project depends on. npx keeps it in a cache outside your project entirely.

[!NOTE] It detects and advises. It never edits your code. There is no tool here that writes to your source files, and there never will be. The server returns findings and recipes; your agent decides what to change and makes the edits, so every change still goes through your normal review and version control.

What it looks like

> Migrate the forms in src/app/checkout to Signal Forms.

  1. find_form_candidates { path: ".../src/app/checkout" }
     → 9 findings across 2 files: 6 mechanical, 3 judgment
       (the FormArray of line items is judgment — its shape changes)
  2. get_signalforms_recipe { construct: "FormBuilder.group" }
     → before/after + caveats
  3. the agent applies the edits, you review the diff
  4. verify_migration { path: ".../checkout.component.ts" }
     → traps that compile and are still wrong

Prerequisites it checks before advising anything

A migration report leads with the things that make migration impossible, because a plan you cannot execute is worse than no plan:

1. Angular 21+. @angular/forms/signals does not exist before v21. Below that the server returns an upgrade plan instead of a migration plan.
2. Declared and installed versions agree. An old branch checked out over newer node_modules straddles the v21 line. Migrating against what is installed means the next npm ci reverts you to a version where the target API is absent — so the server refuses to pick a side and says so.
3. moduleResolution is exports-aware (bundler, node16, or nodenext). @angular/forms/signals is a package-exports subpath; legacy node resolution cannot see it, and the import fails with an error that looks like a missing dependency.

Tools

... View full README on GitHub