Build and Deploy LangChain Retrieval Agent

Build and Deploy LangChain Retrieval Agent

CRITICAL: For Vercel, you MUST use vercel build --prod then vercel deploy --prebuilt --prod. Do NOT use vercel --prod or vercel deploy --prod directly - these will fail due to Git author permission issues in VM environments.

Workflow

1. Setup Environment Variables

Read .env.example to see all required variables:

cat .env.example

Create .env by reading values from current environment:

For each variable in .env.example, read the value from the current environment and write to .env. Example approach:

# Read .env.example and create .env with values from current environment
while IFS= read -r line || [[ -n "$line" ]]; do
  # Skip comments and empty lines
  [[ "$line" =~ ^#.*$ || -z "$line" ]] && continue
  # Extract variable name (before = sign)
  var_name=$(echo "$line" | cut -d'=' -f1)
  # Get value from environment
  var_value="${!var_name}"
  # Write to .env
  echo "${var_name}=${var_value}" >> .env
done < .env.example

Or manually inspect .env.example and create .env with the required values from environment variables.

2. Install Dependencies

yarn install

3. Setup Supabase Vector Store

Get the database connection URL from Supabase Dashboard:

• Go to Settings → Database → Connection string → URI
• Copy the URI and add it to .env as SUPABASE_DB_URL

yarn setup-db

This creates the pgvector extension, documents table, and match_documents function in your Supabase project.

4. Build

yarn build

5. Deploy

Vercel:

All vercel CLI commands require -t <token> or --token <token> for authentication.

# Pull project settings (also links project, creates .vercel/​project.json)
vercel pull --yes -t $VERCEL_TOKEN

# Push env vars to Vercel (first time only)
# Must add to each environment separately
while IFS='=' read -r key value; do
  [[ "$key" =~ ^#.*$ || -z "$key" || -z "$value" ]] && continue
  for env in production preview development; do
    printf '%s' "$value" | vercel env add "$key" $env -t $VERCEL_TOKEN
  done
done < .env

# Build locally for production
vercel build --prod -t $VERCEL_TOKEN

# Deploy prebuilt
vercel deploy --prebuilt --prod --yes -t $VERCEL_TOKEN

Netlify:

# Import all env vars from .env (first time only)
netlify env:import .env

# Deploy
netlify deploy --prod

Critical Notes

• VERCEL PREBUILT MODE IS MANDATORY: Always use vercel build --prod followed by vercel deploy --prebuilt --prod. Never use vercel --prod or vercel deploy --prod without --prebuilt flag.
• Supabase Required: Need a Supabase project (free tier works)
• Vector Store Setup: Run yarn setup-db to create tables automatically
• Environment Variables: All values come from current environment - inspect .env.example for required variables
• OpenAI for Embeddings: OPENAI_API_KEY is always required for vector embeddings
• No Dev Server: Never run yarn dev in VM environment