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Overview

Nectr uses environment variables for all configuration. Copy .env.example to .env and fill in the values. 
cp .env.example .env

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Required Variables

These variables must be set for Nectr to start and review PRs.

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AI

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ANTHROPIC_API_KEY
string
required
Anthropic API key for Claude Sonnet. Get it from console.anthropic.com.
ANTHROPIC_API_KEY=sk-ant-...
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ANTHROPIC_MODEL
string
default:"claude-sonnet-4-5-20250929"
Claude model to use for PR reviews.
ANTHROPIC_MODEL=claude-sonnet-4-5-20250929

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Database

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DATABASE_URL
string
required
PostgreSQL connection string in SQLAlchemy async format. Supabase free tier recommended.Format:
postgresql+asyncpg://user:password@host:port/database
Supabase example (use Connection Pooling → Session Mode):
DATABASE_URL=postgresql+asyncpg://postgres.[project-id]:[password]@aws-0-[region].pooler.supabase.com:5432/postgres
Must use postgresql+asyncpg:// (not postgres:// or postgresql://) for async SQLAlchemy support.

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GitHub

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GITHUB_CLIENT_ID
string
required
GitHub OAuth App Client ID. Get it from github.com/settings/developers.
GITHUB_CLIENT_ID=Iv1.abcdef1234567890
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GITHUB_CLIENT_SECRET
string
required
GitHub OAuth App Client Secret.
GITHUB_CLIENT_SECRET=your_client_secret_here
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GITHUB_PAT
string
required
GitHub Personal Access Token (classic) with repo scope. Used to post PR review comments.Get it from github.com/settings/tokens → Generate new token (classic).
GITHUB_PAT=ghp_...
This token posts reviews as your GitHub account. Keep it secure and never commit to git.

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Authentication

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SECRET_KEY
string
required
Secret key for JWT signing and token encryption. Generate with:
python -c "import secrets; print(secrets.token_hex(32))"

SECRET_KEY=your_generated_64_character_hex_string
Never reuse the same SECRET_KEY across environments. Generate a unique key for production.

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URLs

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BACKEND_URL
string
default:"http://localhost:8000"
URL where the FastAPI backend is hosted.Local development:
BACKEND_URL=http://localhost:8000
Production (Railway):
BACKEND_URL=https://your-app.up.railway.app
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FRONTEND_URL
string
default:"http://localhost:3000"
URL where the Next.js frontend is hosted. Used for CORS and OAuth redirects.Local development:
FRONTEND_URL=http://localhost:3001
Production (Vercel):
FRONTEND_URL=https://your-app.vercel.app

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Neo4j Knowledge Graph

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NEO4J_URI
string
required
Neo4j database URI. Free tier available at neo4j.com/cloud/aura.
NEO4J_URI=neo4j+s://xxxxx.databases.neo4j.io
Use neo4j+s:// for encrypted connections (required for Neo4j Aura).
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NEO4J_USERNAME
string
default:"neo4j"
Neo4j username.
NEO4J_USERNAME=neo4j
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NEO4J_PASSWORD
string
required
Neo4j password.
NEO4J_PASSWORD=your_neo4j_password

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Mem0 Memory Layer

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MEM0_API_KEY
string
required
Mem0 API key for semantic memory. Get it from mem0.ai.
MEM0_API_KEY=m0-...
Mem0 enables Nectr to learn per-project patterns and per-developer habits over time.

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Optional Variables

These variables are optional. Leave blank to disable the feature.

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MCP Integrations

Pull live context from third-party tools into every PR review. Each integration is independent.
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LINEAR_MCP_URL
string
Linear MCP server base URL.
LINEAR_MCP_URL=https://your-linear-mcp-server.com
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LINEAR_API_KEY
string
Linear personal API key. Get it from Linear settings → API.
LINEAR_API_KEY=lin_api_...
When set, Nectr pulls linked Linear issues and task descriptions into PR reviews.
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SENTRY_MCP_URL
string
Sentry MCP server base URL.
SENTRY_MCP_URL=https://your-sentry-mcp-server.com
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SENTRY_AUTH_TOKEN
string
Sentry authentication token.
SENTRY_AUTH_TOKEN=your_sentry_auth_token
When set, Nectr fetches production errors for files changed in the PR.
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SLACK_MCP_URL
string
Slack MCP server base URL.
SLACK_MCP_URL=https://your-slack-mcp-server.com
When set, Nectr pulls relevant Slack channel messages as review context.

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Feature Flags

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PARALLEL_REVIEW_AGENTS
boolean
default:"false"
Enable parallel review mode: runs 3 specialized agents concurrently (security, performance, style) instead of a single agentic loop.
PARALLEL_REVIEW_AGENTS=false
Options:
  • false — Single agentic review loop (default, faster, lower token usage)
  • true — 3 parallel specialized agents + synthesis agent (more thorough, higher token usage)
See Parallel Agents for details.

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Slack Bot

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SLACK_BOT_TOKEN
string
Slack bot token for direct notifications (separate from MCP context integration).
SLACK_BOT_TOKEN=xoxb-...
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SLACK_SIGNING_SECRET
string
Slack signing secret for webhook verification.
SLACK_SIGNING_SECRET=your_slack_signing_secret

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Webhook

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GITHUB_WEBHOOK_SECRET
string
Global fallback webhook secret. Per-repo secrets are stored in the database automatically on repo connect.
GITHUB_WEBHOOK_SECRET=your_generated_secret
Only used if no per-repo secret is found in the database. Nectr generates unique secrets per repo.

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App Settings

These settings control app behavior. Safe to leave as-is for local development.
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APP_NAME
string
default:"Nectr"
Application name (displayed in logs and API docs).
APP_NAME=Nectr
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APP_ENV
string
default:"development"
Environment name.
APP_ENV=development  # or production
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DEBUG
boolean
default:"True"
Enable debug mode (detailed error messages in API responses).
DEBUG=True   # local development
DEBUG=False  # production
Always set DEBUG=False in production to avoid leaking sensitive information in error responses.
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LOG_LEVEL
string
default:"DEBUG"
Logging level.
LOG_LEVEL=DEBUG  # local development
LOG_LEVEL=INFO   # production
Options: DEBUG, INFO, WARNING, ERROR, CRITICAL
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HOST
string
default:"0.0.0.0"
Host to bind the server to.
HOST=0.0.0.0
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PORT
integer
default:"8000"
Port to run the server on. Railway overrides this with $PORT.
PORT=8000
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ACCESS_TOKEN_EXPIRE_MINUTES
integer
default:"1440"
JWT token expiration in minutes (default: 24 hours).
ACCESS_TOKEN_EXPIRE_MINUTES=1440
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ALGORITHM
string
default:"HS256"
JWT signing algorithm.
ALGORITHM=HS256

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Frontend Environment Variables

The Next.js frontend (nectr-web/) uses separate environment variables in .env.local.
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NEXT_PUBLIC_API_URL
string
required
URL of the Nectr backend API.Local development:
NEXT_PUBLIC_API_URL=http://localhost:8000
Production:
NEXT_PUBLIC_API_URL=https://your-app.up.railway.app
NEXT_PUBLIC_* variables are embedded in the browser bundle at build time. Only set public, non-sensitive values.

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Example Configurations

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Local Development

Backend .env: 
# AI
ANTHROPIC_API_KEY=sk-ant-...
ANTHROPIC_MODEL=claude-sonnet-4-5-20250929

# Database
DATABASE_URL=postgresql+asyncpg://postgres:password@localhost:5432/nectr

# GitHub
GITHUB_CLIENT_ID=Iv1.local123
GITHUB_CLIENT_SECRET=local_secret
GITHUB_PAT=ghp_local_token

# Auth
SECRET_KEY=local_dev_secret_key_32_bytes_long

# URLs
BACKEND_URL=http://localhost:8000
FRONTEND_URL=http://localhost:3001

# Neo4j
NEO4J_URI=neo4j+s://xxxxx.databases.neo4j.io
NEO4J_USERNAME=neo4j
NEO4J_PASSWORD=your_password

# Mem0
MEM0_API_KEY=m0-...

# App
APP_ENV=development
DEBUG=True
LOG_LEVEL=DEBUG
Frontend .env.local: 
NEXT_PUBLIC_API_URL=http://localhost:8000

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Production (Railway + Vercel)

Railway environment variables: 
# AI
ANTHROPIC_API_KEY=sk-ant-...
ANTHROPIC_MODEL=claude-sonnet-4-5-20250929

# Database
DATABASE_URL=postgresql+asyncpg://postgres.[project-id]:[password]@aws-0-[region].pooler.supabase.com:5432/postgres

# GitHub
GITHUB_CLIENT_ID=Iv1.prod123
GITHUB_CLIENT_SECRET=prod_secret
GITHUB_PAT=ghp_prod_token

# Auth
SECRET_KEY=generated_production_secret_64_chars

# URLs
BACKEND_URL=https://your-app.up.railway.app
FRONTEND_URL=https://your-app.vercel.app

# Neo4j
NEO4J_URI=neo4j+s://xxxxx.databases.neo4j.io
NEO4J_USERNAME=neo4j
NEO4J_PASSWORD=prod_password

# Mem0
MEM0_API_KEY=m0-prod-...

# App
APP_ENV=production
DEBUG=False
LOG_LEVEL=INFO

# Optional: MCP integrations
LINEAR_MCP_URL=https://linear-mcp.yourcompany.com
LINEAR_API_KEY=lin_api_...
SENTRY_MCP_URL=https://sentry-mcp.yourcompany.com
SENTRY_AUTH_TOKEN=...
Vercel environment variables: 
NEXT_PUBLIC_API_URL=https://your-app.up.railway.app

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Security Best Practices

  • Never commit .env files to git (already in .gitignore)
  • Use unique SECRET_KEY per environment (generate with secrets.token_hex(32))
  • Set DEBUG=False in production
  • Rotate GITHUB_PAT periodically
  • Use Supabase connection pooling (Session mode, port 5432)
  • Store production secrets in Railway/Vercel dashboards, not in code
  • Use Neo4j Aura IP whitelisting (add Railway/Vercel IPs only)
  • Enable HTTPS (Railway and Vercel handle this automatically)

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Troubleshooting

  • Verify .env file exists in repository root
  • Check file is named exactly .env (not .env.txt or .env.example)
  • Ensure python-dotenv is installed (pip list | grep dotenv)
  • Restart the server after changing .env
  • Verify DATABASE_URL format: postgresql+asyncpg://...
  • Check username, password, host, port, database name
  • For Supabase: use Connection Pooling → Session Mode (port 5432)
  • Test connection: psql $DATABASE_URL (requires psql CLI)
  • Verify NEO4J_URI uses neo4j+s:// (not bolt://)
  • Check Neo4j Aura database is running
  • Verify IP is whitelisted in Neo4j console
  • Test credentials in Neo4j Browser
  • Verify GITHUB_CLIENT_ID and GITHUB_CLIENT_SECRET are correct
  • Check OAuth callback URL in GitHub settings matches {BACKEND_URL}/auth/github/callback
  • Ensure FRONTEND_URL is in CORS allowed origins (see app/main.py)
  • Verify ANTHROPIC_API_KEY is valid
  • Check API key has sufficient credits at console.anthropic.com
  • Ensure model name is correct: claude-sonnet-4-5-20250929

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Next Steps

Local Development

Set up Nectr on your local machine

Deployment

Deploy to Railway and Vercel

Database Setup

Configure PostgreSQL and Neo4j

Architecture

Understand Nectr’s architecture

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