Review GitHub pull requests with GPT-4o and send feedback and Slack alerts

Created by

Last update

Last update 7 hours ago

Who is this for

Engineering teams, code reviewers, and tech leads who want to automate code review feedback. Ideal for repositories with high PR volume where consistent first-pass review is valuable.

What this workflow does

This workflow automates pull request code review using GPT-4o and routes findings to GitHub and Slack. When a pull request is opened, it fetches the raw diff, sends it to GPT-4o for analysis, and posts a formatted Markdown comment with severity rating, categorized issues, suggestions, and an overall score. Critical findings trigger immediate Slack alerts.

How to set up

Add your GitHub OAuth2 credential to the trigger and comment nodes
Add your OpenAI API credential to the GPT-4o node
Add your Slack OAuth2 credential to both Slack notification nodes
Configure n8n Variables: GITHUB_OWNER, GITHUB_REPO, and GITHUB_TOKEN
Activate the workflow - the GitHub webhook registers automatically
Open a test pull request to verify end-to-end execution

Requirements

GitHub repository with OAuth2 credentials and Personal Access Token
OpenAI API account with GPT-4o access
Slack workspace with OAuth2 app installed
Two Slack channels: one for critical alerts, one for review summaries

How to customize

Adjust the diff truncation limit (default 12,000 chars) in the Format PR Diff node. Modify the GPT-4o system prompt to focus on specific code quality concerns like security or performance. Update Slack channel routing based on your team's notification policy.

Node List

#	Node Name	Type	Purpose
1	When PR Opened	GitHub Trigger	Receives pull_request webhook events
2	Check PR Open	If	Passes only `action = opened` to avoid duplicates
3	Fetch PR Diff	HTTP Request	Fetches the raw unified diff from GitHub
4	Format PR Diff	Code	Extracts PR metadata; truncates diff to 12,000 chars
5	AI Code Review with GPT-4	OpenAI	Sends diff to GPT-4o; returns structured JSON review
6	Build Comment for GitHub	Code	Parses JSON; assembles Markdown comment
7	Post Comment to GitHub	GitHub	Posts the AI review comment on the pull request
8	Check Critical Severity	If	Routes based on CRITICAL vs non-critical severity
9	Alert Critical Issues to Slack	Slack	Sends urgent alert to #incident
10	Share Review Summary on Slack	Slack	Sends summary notification to #code-reviews

Total: 10 nodes (+ 5 Sticky Notes)

Sticky Note Compliance

#	Sticky Note Title	Color	Role
1	Main Sticky Note (Overview)	Yellow	Workflow overview, How it works, Setup steps, Customization
2	Trigger and filter PR	White	Covers GitHub trigger and PR filter
3	Fetch and format diff	White	Covers diff retrieval and formatting
4	AI review and comment	White	Covers AI review and comment building
5	Severity check and alerts	White	Covers severity routing and Slack notifications

All sticky notes use H2 headings (## ) and follow n8n public guidelines.