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mcp-rector-warm

Rector is great. Its cold start is not. Every rector process boots Rector from scratch before a single rule fires, on every file. Keep Rector warm and pay that boot once. Same output as cold. up to 10× faster per file on Laravel and Symfony.

Two ways in, one warm engine:

• an MCP server that gives your AI agent a fast Rector;
• a language server that puts Rector's fixes in your editor.

Docs

Who it's for

Both ship in one package. Run one, or both side by side.

Same answers. Just faster.

• Up to 10× faster per file on Laravel and Symfony, at the median.
• Identical output. Every warm answer in the benchmark was byte-identical to a cold rector process, and CI checks warm output against a fresh cold Rector run.
• Keep cold Rector in your CI. Warm is editor feedback: fast, and built to match cold. Keep vendor/bin/rector process --dry-run in CI as the gate, the same as without this tool.
• One-time boot. The first call boots Rector, once per server. An idle server costs nothing.
• Edit rector.php freely. Config changes apply on the next call. No restart.

The fastest mode is on by default: a long-lived session child keeps Rector's analysis warm between calls (what it watches). Set MCP_RECTOR_WARM_SESSION=0 to turn it off. Every write -- rector_process with dryRun: false, an LSP code action, rector-warm.fixWorkspace -- always forks fresh from a pristine worker, never the session, whatever it's set to.

Get started

That's the install. PHP 8.2+, Rector ^2.4 comes along as a normal Composer dependency. Now pick where Rector should run.

Rector in your AI agent

For: anyone who lets Claude, Copilot agent mode, Cursor, Cline or another agent refactor PHP.

• Your agent can run Rector after every edit, without waiting for Rector to boot each time -- automatically with Claude Code via supertool (below), on request with any other client.
• Preview first. The agent sees the diff; files change only when it asks to write.
• Stays inside your project. Paths outside the working directory are refused.
• Any MCP client. Claude Desktop, VS Code, Cursor, Cline, Continue, Zed.

With Claude Code (recommended)

Plain MCP has a gap: the agent has to remember to call rector_process, and in practice it forgets, or calls it only at the end. claude-supertool closes that gap -- its rector-mcp validator runs this server after every edit made through a supertool op, and puts the result in the edit's own output, so "runs Rector after every edit" is a fact about the tool instead of a hope about the agent.

Install the plugin, once per machine:

Restart your Claude Code session afterward -- the plugin's hook only registers at session start.

Then, as a project dependency -- not the global install above, since .supertool.json below points at vendor/bin/:

and a minimal .supertool.json:

mcp_autospawn: true lets the validator start the warm daemon itself on first use, so there is nothing to register as a separate MCP server. After an edit to a PHP file, supertool's own output carries a [validators] block with either rector-mcp : ok or the Rector finding, right where the edit happened:

The honest caveat: this only fires on an edit made through one of supertool's own mutating ops (edit, paste, replace, replace_lines, vim) -- not through Claude Code's built-in Edit/Write tools, which write to disk with no validator and no rollback. To make supertool the only edit route, deny the native tools in the project's .claude/settings.json:

That is a project decision, not something this server or supertool does for you -- see claude-supertool's README, "Hard-block native tools", for the full list (it also covers the raw shell commands supertool replaces) and the headless-session equivalent.

Full supertool setup →, including the optional phpstan validator (backed by mcp-phpstan-warm) alongside this one.

Any other MCP client

Add it to Claude Desktop (~/Library/Application Support/Claude/claude_desktop_config.json on macOS, %APPDATA%\Claude\claude_desktop_config.json on Windows):

Restart Claude and ask: "Run Rector on src/Foo.php". Done.

Full setup → VS Code and other clients, the rector_process tool, timeouts.

Rector in your editor

For: PHP developers who want Rector's suggestions where they write code, not in a terminal afterwards.

• Fixes appear as you type, on unsaved edits too, not only on save.
• One click to apply one rule, the whole file, or the whole project, without touching files that have unsaved changes.
• A broken file never looks clean. A syntax error or a bad config shows up as an error.
• Change rector.php, see it at once. Open files re-check when the config changes.

Point your editor's LSP client at:

for PHP files, with composer.json / rector.php as root markers.

Full setup → copy-paste configs for Neovim and Helix (tested in CI), Zed, Sublime Text and PhpStorm.

Rector in your validation loop

For: teams and tools that run Rector after every generated change, as a check.

• Start once, call per file. No boot on each check after the first.
• Plain MCP over stdio. Drive it from any MCP client library (Python, Node, Go…).
• Failures are real errors. A bad path, a missing config or a Rector exception comes back as an error, never as a silent pass.

Full setup →

This repo dogfoods exactly that setup on itself (#201): .supertool.json runs this checkout's own bin/mcp-rector-warm and mcp-phpstan-warm as claude-supertool validators on every PHP edit, plus phplint/py-compile/bash-check/jsonlint/ yaml-check for the cheap syntax checks. See CONTRIBUTING.md for what that means for a pull request.

The numbers

Up to 10× faster per file on Laravel and Symfony with the warm session (on by default), 3.3–4.1× with MCP_RECTOR_WARM_SESSION=0. Every warm answer was byte-identical to cold -- including every write, which never goes through the session either way.

Machine, method, full table, reproduce it on your project →

Install

Puts mcp-rector-warm and rector-warm-lsp on your $PATH. As a project dependency, both are in vendor/bin/.

Documentation

• MCP server: every client setup, the rector_process tool, options, the call timeout, compatibility.
• Language server: editor setup, diagnostics, quick-fixes, unsaved buffers, fix-all, limits.
• How it works: architecture, config reloads, Windows and other PHP builds without pcntl.
• Benchmark: method, full numbers, how to reproduce.
• FAQ.
• The language server, for the Rector maintainers: design, correctness checks, known limits.

Credits

• Rector by Tomas Votruba and contributors — the engine doing all the real work. If you ship PHP, sponsor him.
• Model Context Protocol by Anthropic — the protocol that makes this kind of tool integration possible.
• mcp/sdk — official PHP SDK, used here for stdio transport + tool discovery.

Related

• Rector docs — config, rules, sets.
• Rector on Packagist — the upstream package.
• claude-supertool — DPT's batched-ops Claude Code companion; integrates this server as a validator.

License

Community License — see Digital Process Tools.