PR Lens is a free, open-source tool from Coldtea.ai that turns a pull request's code changes into an animated architecture and data-flow diagram, posted as a comment directly on the PR. Instead of scrolling a file-by-file diff, you get a visual map of what components changed and how data moves between them, updated automatically on every push.
Short answer: PR Lens by Coldtea.ai is a free GitHub App (open source, MIT licensed) that draws animated architecture and data-flow diagrams inside your pull requests. Install it once per repo and it posts a sticky comment that updates on every push. It's also available as a GitHub Action, a CLI, or an agent skill, but those three modes require your own Gemini or OpenAI API key.
I went through PR Lens's docs site, its GitHub README, and the GitHub App's own listing to see what you're actually installing before you point it at a repo. It's built by the same team behind Coldtea.ai, the multi-agent coding IDE I tested last month, and it solves a narrower problem: once an AI agent hands you a 40-file PR, how do you actually review it without reading every line cold.
What you'll need
For the simplest path — the GitHub App — you need nothing but a GitHub account and admin access on the repo you want to install it into. That's it; no API key, no config file, no billing setup, at least for public repositories, which the app explicitly runs free. If you want more control — running PR Lens as a GitHub Action in your own CI, from the CLI on your machine, or as a skill your coding agent calls automatically — you'll need Node 20.11 or newer, pnpm 10, and your own API key for Gemini (the default model), OpenAI, or a compatible endpoint, since PR Lens doesn't ship a hosted model for those modes. Private-repo pricing for the GitHub App itself isn't published on the site as of this writing, so check the authorization screen or reach out to Coldtea directly before installing on anything you bill a team for.
Step-by-step: setting up PR Lens by Coldtea.ai
1. Decide which installation mode fits your workflow
The GitHub App is the zero-setup option and what most reviewers should start with. The GitHub Action gives you a self-hosted version you control through your own workflow file. The CLI lets you generate diagrams locally without touching CI. The agent skill lets a coding agent (installed via npx skills add coldteadotai/pr-lens) diagram its own changes as it works. In my testing, the GitHub App was the only mode that required zero configuration — everything else asks for an API key up front.
2. Install the GitHub App
Go to github.com/apps/coldtea-pr-lens and install it on the repository or repositories you want covered. The app's own listing describes the flow as "install, open a PR, and the diagram appears in under a minute" — when I walked through the authorization screen, it was a standard GitHub App install with no extra account to create on Coldtea's side.
3. Open a pull request
Once installed, PR Lens watches for new pull requests and pushes to open ones. It posts a single sticky comment per PR — the README is specific that this comment updates in place rather than piling up new comments on every push, which matters if you're used to noisier bot behavior from other review tools.
4. Read the diagram, not just the diff
The comment renders components in green for new, amber for changed, and red for removed, with animated sequences showing the order data moves through the system. Nested <details> sections let you drill into a specific component without leaving the PR. This is the actual point of the tool — you're meant to look at the shape of the change before you read the line-by-line diff, not instead of it.
5. (Optional) Set up the GitHub Action for more control
If you want the diagramming to run in your own CI rather than through Coldtea's hosted app, add .github/workflows/pr-lens.yml using coldteadotai/pr-lens/packages/action@v0, store your model API key as a repo secret, and grant contents: write and pull-requests: write permissions. This is the mode to use on a private repo if you'd rather not install a third-party GitHub App at all.
6. (Optional) Customize behavior with a config file
PR Lens reads settings from .github/pr-lens.yml if you add one — useful for tuning what gets diagrammed on a large monorepo instead of accepting the defaults. The README's own advice on one six-lane monorepo example was blunt: "you should not be opening a PR this large" — a reminder that the tool visualizes blast radius, it doesn't fix the size of your PRs.
Example prompts you can copy
PR Lens doesn't take natural-language prompts the way a chat tool does, but the CLI and agent-skill modes accept commands and instructions worth having ready:
npx @coldtea/pr-lens-cli analyze— run this locally before opening a PR to see the diagram your changes will generate, so you can catch a confusing architecture before a reviewer does.npx @coldtea/pr-lens-cli validate— checks your.github/pr-lens.ymlconfig for errors before you commit it, which saves a failed CI run.- For the agent skill: "Diagram the data flow for the change you just made before committing, and flag if it touches more than three top-level components." This gets a coding agent to self-check the blast radius of its own PR before you ever see it.
- "Regenerate the PR Lens diagram after this fix" — useful in a PR comment thread when you've pushed a follow-up commit and want the sticky comment to reflect the current state rather than the original one.
Common mistakes to avoid
The mistake I'd flag first: installing the GitHub App on a private repo and assuming it's free, when the site only states the app is free for open source — commercial pricing for private repos isn't published anywhere I could find, so confirm the terms on the actual authorization screen before you install broadly. Second, treating the GitHub Action, CLI, and agent skill as free just because the GitHub App is — those three modes call a model API directly using your own key, so you're paying Gemini or OpenAI's usage rates even though PR Lens itself doesn't charge a subscription. Third, skipping the diagram and going straight to the diff out of habit; the whole point of the tool is catching architectural drift — a change that touches more components than the PR title suggests — which a line diff doesn't surface well. Fourth, letting a coding agent open PRs that are too large to diagram usefully; if the README is telling you a monorepo PR is too big to render cleanly, that's a signal to split the PR, not a rendering bug to work around. Fifth, editing the generated SVG directly instead of fixing the underlying config — the README recommends correcting .github/pr-lens.yml so the diagram stays consistent with future pushes instead of drifting out of sync.
PR Lens vs. CodeRabbit at a glance
| PR Lens (Coldtea.ai) | CodeRabbit | |
|---|---|---|
| What it does | Draws an animated architecture/data-flow diagram in the PR | Writes AI review comments, 1-click fixes, and summaries |
| Price (public repos) | Free, open source (MIT) | Free reviews forever for public repos |
| Price (private repos) | Not published; GitHub App terms apply | Essentials $24/dev/mo, Team $48/dev/mo, Advanced $72/dev/mo (billed annually) |
| Model cost | Bring your own key for Action/CLI/skill modes (GitHub App is hosted) | Included in subscription |
| Output format | Visual diagram, sticky PR comment | Text review comments, inline suggestions |
| Best for | Understanding what changed structurally before reading code | Catching bugs, style issues, and security problems in the code itself |
These solve different problems and I'd expect many teams to run both rather than choose one. I confirmed PR Lens's pricing on prlens.dev and CodeRabbit's tiers on coderabbit.ai/pricing on September 7, 2026 — usage-based add-ons on both sides change often enough that the live pages are worth a second look before you commit a team to either.
Tools that make this easier
PR Lens comes from the same company as Coldtea.ai, the desktop IDE I reviewed that bundles multi-agent coding, QA, and monitoring — if you're already running Coldtea's terminal, PR Lens is a natural add-on for the review side of that workflow rather than a separate purchase decision. If you're weighing PR Lens against a fuller AI code-review suite, my best AI tool for code roundup covers where diagram-first tools fit next to line-by-line reviewers. The underlying problem PR Lens is built to solve — reviewing PRs an AI agent wrote faster than you'd write them yourself — is exactly what I dug into in my honest review of AI programming tools and in AI-written code is still your code, which makes the case for why a visual pass before the line-by-line diff actually matters. For a broader look at coding agents PR Lens can sit alongside, see my AI coding assistant guide. And if you're running several agents in parallel and worried about conflicting changes landing in the same PR, this local merge queue for parallel Claude Code agents tackles a related coordination problem from a different angle.
My take
PR Lens solves a real, specific problem: once a coding agent can generate a 40-file PR in the time it takes you to read the title, a line-by-line diff stops being a reasonable first pass. Drawing the architecture and data flow before the diff is a genuinely useful reframe, and making the GitHub App free for open source with a one-minute install is the right call for adoption. What's less clear is the private-repo story — there's no published commercial price, and the Action, CLI, and agent-skill modes all push the model cost onto your own API key rather than bundling it. If you're already inside Coldtea's ecosystem, install PR Lens on your next real PR and see if the diagram actually changes how fast you approve things. If you're not, it's still worth trying on a public repo first, since that's the one mode with a genuinely zero-cost, zero-config path to test it.
Last updated: September 7, 2026 · By Vishal Swami, Founder & Lead AI Reviewer, AISagely
Frequently Asked Questions
Is PR Lens by Coldtea.ai free?
The GitHub App is free for open-source repositories, with no API key required. Private-repo pricing isn't published on the site, so check the authorization screen or contact Coldtea before installing on a commercial repo. The GitHub Action, CLI, and agent skill are free to run yourself, but you supply your own Gemini or OpenAI API key, so you pay that provider's usage rate.
How long does it take to set up PR Lens?
The GitHub App install takes under a minute, per PR Lens's own listing — you authorize it on a repo and the diagram appears on the next PR. The GitHub Action or CLI setup takes longer since you're adding a workflow file or installing Node and pnpm locally and wiring up an API key first.
What is the easiest way to use PR Lens?
Install the GitHub App on a public repository first. It needs no configuration, no API key, and no separate account, so it's the fastest way to see whether the diagram format actually changes how you review PRs before you invest in the Action, CLI, or agent-skill setup.
Does PR Lens replace a tool like CodeRabbit?
No. PR Lens draws a structural diagram of what changed; it doesn't write review comments, flag bugs, or suggest fixes the way CodeRabbit does. They solve adjacent problems — seeing the shape of a change versus catching issues in the code itself — and I'd expect most teams to use them together rather than pick one.
Can I use PR Lens with a coding agent like Claude Code or Codex?
Yes. The agent-skill mode, installed with npx skills add coldteadotai/pr-lens, lets a coding agent generate a diagram of its own changes as part of its workflow, which is useful if you want the agent to self-check the blast radius of a PR before it ever reaches you.