Backloop Code Review

A fully local code review platform with a built-in feedback loop, to make iterating on agentic code output efficient and fun.

Overview

Coding assistants do great on many tasks, but they are still lacking when working on big, established code bases. In particular, getting code from a working prototype to review-grade version that meets all coding standards often requires a significant amount of manual polishing, that can easily eat up the initial efficiency gains.

Backloop provides a streamlined workflow for reviewing code changes with AI assistance, providing live feedback and an instant feedback loop.

It works by spinning up an ad-hoc web server that hosts a GitHub-like code review UI that's linked to the current coding session.

For the assistant, the workflow looks like this:

1. Start a review by calling startreview() and give the returned URL to the user
2. Call await_comments(), and ...
3. ... if receiving a comment, work on it and call receive_comment()
4. ... if receiving REVIEW APPROVED, done.

For the user, the workflow looks like this:

1. Open the link to the review
2. Leave comments with feedback, or edit small touch-ups directly
3. When satisfied with the code, approve the review.

A review will have a url like http://127.0.0.1:52267/review/c0837b48/view?since=HEAD~1&live=true, you can adjust the query parameters to get a different view on the repository. See the reference section below to learn which parameters exist.

When in "live" mode, that is when the live parameter is set to true, the review willl also show untracked files and non-staged changes in the current working directory, and include an "edit directly" button to make small changes directly, without waiting for a round of thinking.

Installation

To add the MCP server to Claude Code use

claude mcp add local-review -- uvx --from backloop backloop-mcp

or run the equivalent command for the agent of your choice.

Then, use a prompt like this to start the review:

> Open a local review for the changes you made and wait for approval, then commit and push the changes.

Standalone Usage

You can also use Backloop without an agent, as a standalone local diff viewer:

uvx --from backloop server

This starts the web server which you can use to view diffs and add comments. (though no one will see the comments in that case)

MCP Tools Reference

Once configured, Claude has access to these MCP tools:

startreview()

Starts a new review session. Exactly one parameter must be specified:

• since='HEAD' - Review changes since a given commit, including uncommited changes
• commit='abc123' - Review a specific commit
• range='main..feature' - Review a range of commits
• title='foo' - Optional review title

Examples:

• Review changes before committing: startreview(since='HEAD')
• Review changes after committing: startreview(since='HEAD~1')
• Review changes to a PR branch: startreview(range='origin/main..HEAD')

await_comments()

Blocks until either a comment is posted or the review is approved. Returns comment details (including the originating review_id) or "REVIEW APPROVED".

resolve_comment()

Marks a specific comment as resolved by its ID.