ropey

Safe, project-wide Python refactoring for coding agents. ropey is an MCP server that exposes the rope refactoring library as tools a coding agent (Claude in Claude Code, OpenCode, or any MCP client) can call.

Why

Coding agents read and navigate Python well. An LSP like Astral's ty answers "where is this defined?" and "who references it?" precisely. What agents lack is a safe way to change Python structurally. Renaming a symbol used across thirty files by hand-editing text is slow and unreliable: the agent can't be sure it found every reference, can't prove a textual match is the same binding, and routinely leaves half-renamed code.

ropey closes that gap with one division of labour:

ty finds and reads; ropey changes.

The agent points at code using the exact line/character coordinates its LSP already returned, and ropey performs the behaviour-preserving transformation across the whole project: rename, move, extract, inline, change signature, organise imports, and so on. One sibling tool, rewrite, takes a pattern→goal transformation for structural changes none of the refactorings express, addressed by a code template rather than a coordinate (see the safety contract).

Related MCP server: OHM-MCP

The safety contract

• Behaviour is preserved, with one exception. Every refactoring alters the structure of your code without changing what it does, and rope proves each transformation safe before ropey writes it. rewrite is the exception: it makes no behaviour-preservation claim. The agent asserts that pattern and goal are equivalent, and the tool guarantees only that it rewrites exactly the matches it reports. In exchange it surfaces every Match Site (file + range, flagged matched or unsure) for the agent to audit, leaves unprovable sites un-rewritten unless explicitly opted in, and refuses any rewrite that would produce unparsable Python. Both preview and apply mode enforce that refusal.

• Dry Run by default. Every tool takes an apply flag. With apply=false (the default) the full consequence is computed and reported but nothing is written. apply=true performs the same change for real. Both report identical detail.

• The Blast Radius. Every result enumerates every affected file with what happened to it: modified, created, moved (with its old path), or deleted. The list is never truncated and never carries file contents. After a live run, git diff shows the exact text.

• Uncertain Occurrences. Python is dynamically typed, so sometimes rope cannot prove that obj.save() refers to the method being renamed. ropey applies only the certain occurrences and reports every uncertain one as a flagged location for the agent to adjudicate. Nothing is silently included or silently dropped.

• Freshness is self-established. Before every refactoring the server re-checks the source on disk, so edits from any writer are reflected, whether they came from the agent, a human editor, git checkout, or a formatter. Correctness never depends on the host announcing its edits.

• git is the undo. ropey writes no cache artifacts into your repo (no .ropeproject/), never edits gitignored files (git couldn't revert them), and recommends a clean working tree before applying so git diff / git checkout are always a complete reversal mechanism.

• Failures are structured. A refactoring that cannot proceed returns a machine-readable reason ("the selection crosses a scope boundary", "the file broken.py cannot be parsed") rather than a stack trace.

Install

Claude Code (plugin marketplace)

/plugin marketplace add andrewesweet/ropey
/plugin install ropey@ropey

The plugin bundles the MCP server config; tools appear after a restart. Requires uv on your PATH.

OpenCode

Add to opencode.json:

{
  "$schema": "https://opencode.ai/config.json",
  "mcp": {
    "ropey": {
      "type": "local",
      "command": [
        "uvx", "--from", "git+https://github.com/andrewesweet/ropey", "ropey"
      ],
      "enabled": true
    }
  }
}

Any other MCP client

ropey is a standard stdio MCP server. Generic config:

{
  "mcpServers": {
    "ropey": {
      "command": "uvx",
      "args": ["--from", "git+https://github.com/andrewesweet/ropey", "ropey"]
    }
  }
}

Or run it directly: uvx --from git+https://github.com/andrewesweet/ropey ropey

The catalogue

Targets are addressed with LSP coordinates (0-based line/character, UTF-16 units), the same coordinates an LSP returns; byte offsets never appear. Point refactorings accept an optional expected_symbol so a stale position fails loudly instead of refactoring the wrong code. The exception is rewrite, which is addressed by a pattern (Python source with ${wildcard} placeholders) instead of a coordinate, and reports its Match Sites back as LSP ranges. ty finds and reads; ropey changes.

Development

uv sync
uv run pytest

Domain documentation lives in CONTEXT.md, the decision records in docs/adr/, and the PRD in docs/prd/. Operability notes and measured latency envelopes: docs/operability.md.