The 6 Best AI Code Review Tools for Pull Requests in 2025

A comprehensive comparison of platforms, bots, and agents to speed up your code review cycle.

Introduction: The "Review Gap" in the Age of AI

AI code generation tools like GitHub Copilot and Cursor have fundamentally changed how developers write code. What once took hours now takes minutes. A single developer can output 2-3x more code than before. But here's the problem I keep seeing with teams I talk to: while AI has accelerated code creation, human review capacity has remained completely flat.

This mismatch has created what I call the "Review Gap." Your team is writing more code than ever, but you're still reviewing it the old way, one PR at a time, with the same limited human attention. Pull requests pile up. Context switching increases. Deployment velocity suffers.

The solution isn't to hire more reviewers or work longer hours. The solution is to apply AI to the review process itself. Modern AI code review tools have evolved far beyond simple linters. They provide context-aware analysis that can summarize changes, catch subtle bugs, verify architectural alignment, and even suggest fixes, all in seconds rather than hours.

But not all AI review tools are created equal. I tested the leading options based on three critical criteria:

Context awareness: Does it understand your entire repository, or just the lines that changed?

False positive rate: Does it waste your time with nitpicks, or does it flag genuinely important issues?

Workflow integration: Does it fit naturally into your development process, or is it just another noisy bot cluttering your PR timeline?

Let's look at the six best tools available in 2025.

1. Graphite Agent (Best Overall Platform)

Category: Comprehensive review platform

Why it wins: Graphite solves the root cause of slow reviews (workflow) and applies AI on top.

Most AI code review tools are bots that bolt onto your existing GitHub workflow. They leave comments, generate summaries, and hope for the best. Graphite takes a fundamentally different approach. It's a platform that rethinks the entire code review workflow, starting with how you structure your changes.

Graphite's killer feature is stacked pull requests. Instead of creating one massive PR with 2,000 lines of changes, you break your work into small, atomic PRs that build on each other. Each PR in the stack is focused and reviewable. This approach dramatically improves review speed and quality, but here's the AI advantage: smaller PRs give AI dramatically better results.

When Graphite Agent reviews a 200-line PR with a clear scope, it can provide genuinely useful feedback. It catches type errors, identifies potential race conditions, spots security vulnerabilities, and suggests optimizations. When competitors try to review a 2,000-line monolithic PR, their AI struggles with context and produces generic advice or misses critical issues entirely.

Graphite Agent isn't just a comment bot. It's an interactive companion that lives on your PR page. You can ask it questions like "What happens if this API endpoint receives a null value?" or "Is this change thread-safe?" It generates test plans, explains complex logic, and provides instant summaries of what changed and why.

The integration feels seamless. Graphite Agent appears directly in Graphite's PR inbox, which provides a cleaner, faster interface than GitHub's native UI. Reviews happen in under 90 seconds. The AI maintains a sub-5% negative feedback rate, meaning developers trust its suggestions because they're rarely wrong.

Pricing is straightforward and team-friendly. Graphite Agent is included in paid plans. The Team plan runs around $40 per user per month with unlimited AI reviews, making it cost-effective for organizations that review hundreds of PRs weekly.

Best for: Teams who want to fundamentally speed up their development velocity, not just add a bot to GitHub.

2. GitHub Copilot (Best for IDE Integration)

Category: IDE and native GitHub integration

Overview: The default choice for many teams. GitHub Copilot excels at "in-the-flow" assistance while writing code.

GitHub Copilot started as an autocomplete tool but has expanded into code review territory. If you're already using VS Code with Copilot, you get basic PR review features built in. Copilot can generate PR descriptions, summarize changes, and leave inline comments on pull requests through GitHub's native interface (especially with the Enterprise tier).

The main advantage is deep integration with the Microsoft ecosystem. Copilot works seamlessly in VS Code, integrates with GitHub Enterprise, and meets enterprise compliance requirements out of the box. For organizations heavily invested in Microsoft tooling, this integration is valuable. You get a single vendor, unified billing, and consistent security policies across development tools.

The "Copilot Workspace" feature allows developers to describe desired changes in natural language, and Copilot suggests code modifications. This works well for small refactoring tasks or implementing simple features. The AI has improved significantly over the past year and can handle increasingly complex requests.

That said, Copilot's PR review experience has notable limitations compared to specialized agents. The analysis often stays surface-level, focused on style and obvious bugs rather than architectural concerns or subtle logic errors. Early adopters report that Copilot's PR comments can be noisy if not carefully configured. The AI doesn't have the same "agentic" feel as specialized tools. It provides suggestions but lacks the deeply interactive, conversational interface that helps developers dig deeper into complex issues on the PR timeline itself.

Pricing varies by plan. GitHub Copilot Individual is $10 per month, while Copilot Business is $19 per user per month. Organizations paying for GitHub Enterprise receive the most advanced PR summarization and review features as part of their contract.

Best for: Teams fully committed to the Microsoft ecosystem who want a safe, baseline AI experience without changing their workflow.

3. CodeRabbit (Best Standalone Bot)

Category: Third-party PR bot

Overview: A popular tool that connects to GitHub, GitLab, or Bitbucket and provides detailed AI reviews through PR comments.

CodeRabbit has established itself as the leading third-party AI review bot. It offers a rich feature set that goes well beyond basic static analysis. When you open a PR, CodeRabbit automatically generates a detailed "walkthrough" summary explaining what changed and why. It uses a combination of large language models and traditional linters (it runs over 40 different code analyzers) to provide comprehensive feedback.

The chat interface is a standout feature. You can have a conversation with CodeRabbit directly in PR comments, asking follow-up questions or requesting clarification on its suggestions. This makes the review process more interactive and helps developers understand the reasoning behind each recommendation.

CodeRabbit is highly configurable. You can tune its "nitpickiness" level, define custom rules for your codebase, and train it to learn from your team's feedback over time. It integrates with multiple platforms (GitHub, GitLab, Bitbucket, Azure DevOps) and offers both cloud and self-hosted deployment options for teams with strict security requirements.

The main drawback is noise. CodeRabbit leaves many comments on each PR. While comprehensive analysis can be valuable, it also clutters the GitHub timeline and can overwhelm developers, especially on larger changes. You'll need to invest time in configuration to dial down irrelevant feedback. Some teams report that CodeRabbit's enthusiasm for suggesting improvements, while well-intentioned, creates review fatigue.

Pricing is competitive. CodeRabbit offers a free tier for open-source projects and personal use. Paid plans range from $12 per user per month(Lite) to $24-$30 per user per month (Pro). The Pro tier includes all features: advanced linters, chat capabilities, and detailed reporting.

Best for: Teams who want to keep the native GitHub UI but need better automated feedback, and who don't mind investing time in configuration.

4. Greptile (Best for Deep Context and RAG)

Category: Specialized context engine

Overview: Focuses heavily on understanding your entire codebase, not just the diff in each PR.

Greptile takes a unique approach to AI code review by building a comprehensive knowledge graph of your entire repository. It indexes every function, every dependency, every historical change, and uses this context to provide unusually deep analysis. When reviewing a PR, Greptile doesn't just look at the changed lines. It understands how those changes ripple through your entire codebase.

This approach excels at answering complex questions that require cross-file or cross-module understanding. For example: "How does this API change affect the billing service?" or "What other components depend on this function?" Greptile can trace dependencies, identify potential breaking changes, and spot issues that would be nearly impossible for a human reviewer to catch without hours of investigation.

The tool is particularly valuable for large, legacy codebases where understanding context is the hardest part of code review. New team members benefit enormously from Greptile's ability to explain how different parts of the system interact. Senior engineers appreciate having an AI that can flag subtle architectural issues that simple diff-based analysis would miss.

Greptile emphasizes customization and enterprise features. You can define private AI models, create custom rules specific to your organization, and deploy Greptile on-premises for complete control over your data. The tool meets SOC 2 compliance standards and integrates with both GitHub and GitLab.

The trade-off is complexity. Greptile's full-repository analysis takes time to set up and requires more computational resources than simpler diff-based tools. The platform is priced for enterprise use at around $30 per user per month for cloud deployment, with custom pricing for self-hosted options. For smaller teams or simpler codebases, this may be more powerful than necessary.

Best for: Large, complex monorepos where understanding the impact of changes across the entire system is the hardest part of code review.

5. Ellipsis (Best for Automated Fixes)

Category: Action-oriented agent

Overview: An AI agent that can take reviewer comments and automatically implement the requested changes.

Ellipsis bridges the gap between review and implementation. Most AI review tools identify issues and leave comments. Ellipsis goes further: it can read a reviewer's comment ("Make this variable const" or "Add input validation here") and automatically generate a commit with the fix.

This capability is genuinely useful for reducing the back-and-forth in code reviews. Instead of the original author context-switching back to their IDE, finding the file, making the change, and pushing a new commit, Ellipsis handles it automatically. For minor refactoring tasks, style fixes, or simple logic adjustments, this saves significant time.

The tool works by maintaining a detailed understanding of your codebase and coding standards. When it receives a request to implement a change, it generates the code, runs tests to verify nothing breaks, and commits the result. You can review and approve the change before it's applied, maintaining control over what gets merged.

Ellipsis integrates with GitHub and supports multiple programming languages. The AI is trained on millions of open-source repositories, giving it broad knowledge of common patterns and best practices. It's particularly effective for teams that follow consistent coding conventions, as the AI can learn and replicate those patterns.

The limitations are predictable: Ellipsis handles simple, mechanical changes well but struggles with complex logic or architectural refactoring. It works best as a junior engineer who can take clear direction and implement straightforward fixes. For ambiguous or high-complexity changes, human implementation is still necessary.

Pricing has recently shifted to a seat-based model. Ellipsis charges $20 per user per month for unlimited usage, moving away from previous per-commit pricing structures. This makes it predictable for teams to adopt.

Best for: Teams who spend too much time on minor refactoring cycles and want to automate the implementation of simple reviewer feedback.

6. BugBot by Cursor (Best for Security and Logic Errors)

Category: Specialized defect detection

Overview: A tool trained specifically to find logic bugs and security vulnerabilities, developed as part of the Cursor ecosystem.

BugBot takes a surgical approach to code review. Instead of trying to do everything, it focuses exclusively on finding critical bugs and security issues. It's designed to act as a "pre-merge safety net" that catches hard-to-spot problems before they reach production.

The tool excels at identifying edge cases, race conditions, null pointer exceptions, and security vulnerabilities. It's particularly effective at reviewing AI-generated code, where subtle logic errors are more common than with human-written code. BugBot's analysis is highly precise. It maintains a low false-positive rate by focusing only on genuinely problematic code rather than style issues or minor optimizations.

BugBot is deeply integrated with the Cursor IDE. When it flags an issue, you can jump directly to the problematic code in your editor and apply the suggested fix with one click. The tight IDE integration makes the review-fix-verify cycle extremely fast.

The main limitation is scope. BugBot doesn't generate PR summaries, doesn't provide architectural feedback, and doesn't help with code documentation or readability. It has one job: find critical bugs. For teams that need comprehensive review assistance, BugBot would need to be paired with other tools.

Adoption requires committing to the Cursor ecosystem. If your team uses VS Code, IntelliJ, or other editors, switching to Cursor represents a significant change. Some developers love Cursor's AI-first features, others prefer their existing tools.

Pricing is currently tied to your Cursor subscription. It's generally included in Cursor's paid plans (Pro/Business) which start at $20 per user per month, rather than being sold as a standalone bot.

Best for: High-compliance industries or mission-critical codebases where preventing logic errors and security vulnerabilities is paramount, and teams willing to adopt the Cursor IDE.

Comparison Table: At a Glance

How to Choose the Right Tool

For pure speed and workflow improvement: Choose Graphite. The combination of stacked PRs and integrated AI provides the fastest path from code complete to merge. You're not just adding AI to a slow process, you're fixing the process itself.

For massive monorepo querying: Choose Greptile. If your biggest challenge is understanding how changes ripple through a large, complex codebase, Greptile's full-repository analysis provides unmatched context.

For simple summaries on GitHub: Choose CodeRabbit or GitHub Copilot. If you want to keep your existing workflow and just add AI feedback, either of these bots will provide useful suggestions without requiring major changes to how your team works.

For mission-critical bug prevention: Choose BugBot (Cursor). If you're in a regulated industry or working on code where bugs have severe consequences, BugBot's laser focus on critical defects provides valuable protection.

For reducing trivial back-and-forth: Choose Ellipsis. If your reviews are slow because of many small fix requests, having an AI that can implement those fixes automatically saves significant time.

Conclusion

AI code review tools are no longer optional. They're essential for handling the volume of code being generated today. The Review Gap is real, and it's growing. Teams that don't adopt AI assistance will find themselves increasingly unable to keep up with the pace of development.

That said, not all AI tools address the underlying problem. Most are bots that add automation to a fundamentally slow, inefficient workflow. They help, but they're band-aids on a broken process.

To truly fix code review, you need a platform that incentivizes better practices (smaller, more focused PRs) and reviews them with AI. That's why Graphite stands out. It's not just an AI reviewer, it's a complete rethinking of how code review should work in the age of AI-accelerated development.

The best teams are shipping faster than ever while maintaining higher code quality. They're doing it by combining better workflow practices with AI assistance. If you're still relying on manual reviews of large, monolithic PRs, you're leaving velocity and quality on the table.

Try Graphite Agent today — it's included in every Graphite plan. Sign up and review your first stack in minutes.