ECC is a free, MIT-licensed toolkit trending on GitHub that bundles the code review job teams usually buy separately from CodeRabbit or Greptile alongside a Copilot subscription.
A small engineering team choosing its AI coding stack often ends up paying twice for related jobs: once for a coding assistant like GitHub Copilot, and again for a separate service that reviews the pull requests the assistant helps produce. ECC, an open source toolkit that has been climbing GitHub's trending list, is built around closing that gap. It is free and MIT licensed, and its own documentation frames code review as the piece a Copilot-only team would otherwise buy separately, from a service like CodeRabbit at $24 to $72 per developer per month, or Greptile at $30 per seat per month, on top of a GitHub Copilot seat at $10 a month.
ECC is not a model. It sits on top of an existing coding agent, most fully supported inside Claude Code, and adds the process around it. The README describes a system that "plans before it builds, verifies changes with tests, reviews its own work from a fresh context, remembers what matters, and turns repeated wins into reusable skills and workflows." Installed once, it gives a project access to 68 specialized agents and 286 skills covering planning, testing, security review, and build repair, plus AgentShield, a scanner the project runs against its own prompts, hooks, and configuration files. The GitHub page currently shows about 247,000 stars and 37,200 forks, though the count is less interesting than what is actually bundled underneath it.
The comparison to paid tools is explicit rather than implied. In its own feature-parity table, ECC lists code review as a capability and names the GitHub Copilot equivalent as "external PR review via CodeRabbit + Greptile," the two services a Copilot-only setup would need to add separately. That core functionality is free and MIT licensed. A hosted version for private repositories, ECC Pro, starts at $19 per seat per month, which still undercuts a single CodeRabbit Essentials seat.
Install paths are documented for several routes: a guided npx ecc-universal setup command, native plugin installation inside Claude Code, or a full manual clone and install script. Commit history on the repository shows near-daily activity through the first days of September, and the README states plainly that the project currently ships from a single maintainer who pushes updates weekly across seven supported coding harnesses.
For a founder or operations lead who signs off on software spend without writing the code personally, the appeal is straightforward. A five- or ten-person engineering team that already pays for Copilot seats does not necessarily need a second recurring line item just to get PR review coverage. Folding that function into a free, self-hosted layer can turn two subscriptions into one, or into a much smaller ECC Pro bill if private-repo hosting was the only reason the team needed a paid tier at all.
That said, the saving is really a labor trade, not a free lunch. Someone on the team still has to install, configure, and keep ECC updated, and the project's own support documentation is honest that feature parity depends on which coding tool a team runs it with. Inside GitHub Copilot specifically, ECC can only offer an instruction and prompt layer, since Copilot has no hook system or subagent API for it to plug into. The fuller agent, hook, and memory automation is reserved for Claude Code.
The tool does not remove the need for a person to read what gets merged. It automates the review pass, not the judgment behind it, and a team relying on one maintainer's release cadence is also accepting the risk that comes with any project run by a single person, even one that is active and well documented.
The more useful question for a team looking at this is not whether the free version matches the paid stack feature for feature, but whether the work of running it themselves costs less than the subscriptions it replaces. That answer looks different for a two-person shop than it does for a company that already has someone doing platform engineering as part of their job.