supabase-local-dev-loopClaude Skill

Supabase Local Dev Loop

Overview

Run the full Supabase stack locally — Postgres, Auth, Storage, Realtime, Edge Functions, and Studio — using Docker and the Supabase CLI. Local development mirrors production APIs exactly, enabling offline work, fast iteration, and repeatable migration workflows. Schema changes flow through supabase db diff to generate migrations, and supabase db reset replays them cleanly.

Prerequisites

• Docker Desktop installed and running (required for all local services)
• Node.js 18+ (for npx supabase commands)
• No global install needed — all commands use npx supabase

Instructions

Step 1: Initialize Project and Start Local Stack

# Initialize Supabase in your project root
npx supabase init

This creates a supabase/ directory:

supabase/
├── config.toml          # Local stack configuration (ports, auth settings)
├── migrations/          # SQL migration files (version-controlled)
└── seed.sql             # Seed data (runs after migrations on db reset)

Start the local stack (first run pulls Docker images — takes a few minutes):

npx supabase start

The CLI prints all local endpoints and keys:

API URL:          http://localhost:54321
GraphQL URL:      http://localhost:54321/graphql/v1
S3 Storage URL:   http://localhost:54321/storage/v1/s3
DB URL:           postgresql://postgres:postgres@localhost:54322/postgres
Studio URL:       http://localhost:54323
Inbucket URL:     http://localhost:54324
anon key:         eyJhbGciOiJI...
service_role key: eyJhbGciOiJI...

Create .env.local from these values (git-ignored):

# .env.local
SUPABASE_URL=http://localhost:54321
SUPABASE_ANON_KEY=<anon-key-from-supabase-start>
SUPABASE_SERVICE_ROLE_KEY=<service-role-key-from-supabase-start>
DATABASE_URL=postgresql://postgres:postgres@localhost:54322/postgres

Verify the stack is running:

npx supabase status

Step 2: Create Migrations and Seed Data

Create a migration file with a descriptive name:

npx supabase migration new create_profiles
# Creates: supabase/migrations/<timestamp>_create_profiles.sql

Write the migration SQL:

-- supabase/migrations/<timestamp>_create_profiles.sql
create table public.profiles (
  id uuid references auth.users(id) primary key,
  username text unique not null,
  avatar_url text,
  created_at timestamptz default now(),
  updated_at timestamptz default now()
);

-- Always enable RLS on public tables
alter table public.profiles enable row level security;

create policy "Public profiles are viewable by everyone"
  on public.profiles for select
  using (true);

create policy "Users can update own profile"
  on public.profiles for update
  using (auth.uid() = id);

-- Auto-create profile on signup via trigger
create or replace function public.handle_new_user()
returns trigger as $$
begin
  insert into public.profiles (id, username)
  values (new.id, new.raw_user_meta_data->>'username');
  return new;
end;
$$ language plpgsql security definer;

create trigger on_auth_user_created
  after insert on auth.users
  for each row execute procedure public.handle_new_user();

Add seed data for local development:

-- supabase/seed.sql (runs automatically after migrations on db reset)
insert into auth.users (id, email, raw_user_meta_data)
values
  ('a1b2c3d4-e5f6-7890-abcd-ef1234567890', 'alice@example.com',
   '{"username": "alice"}'),
  ('b2c3d4e5-f6a7-8901-bcde-f12345678901', 'bob@example.com',
   '{"username": "bob"}');

Apply migrations and seed data in one command:

npx supabase db reset
# Drops the database, replays all migrations, runs seed.sql

Step 3: Iterate with Diff-Based Migrations

The core iteration loop: make changes in Studio, diff them into migration files, then verify with a clean reset.

Open Studio at http://localhost:54323 and make schema changes interactively (add columns, create tables, modify RLS policies). Then capture those changes as a migration:

# Generate a migration from the diff between migrations and current DB state
npx supabase db diff -f add_bio_to_profiles

# Review the generated file
cat supabase/migrations/*_add_bio_to_profiles.sql

The generated migration captures exactly what changed:

-- Auto-generated by supabase db diff
alter table public.profiles add column bio text;

Verify the full migration chain replays cleanly:

npx supabase db reset
# Success = all migrations + seed apply without errors

Push verified migrations to a remote Supabase project:

# Link to remote project first (one-time)
npx supabase link --project-ref <your-project-ref>

# Push migrations to remote
npx supabase db push

Daily workflow summary:

# Start of day
npx supabase start

# After schema changes in Studio
npx supabase db diff -f descriptive_name
npx supabase db reset          # Verify clean replay

# Before committing
npx supabase db reset          # Final verification
npm test                       # Run tests against local instance

# End of day
npx supabase stop

Output

• Local Supabase stack running all services via Docker (Postgres, Auth, Storage, Realtime, Studio)
• Version-controlled migration files in supabase/migrations/
• Seed data for repeatable local state
• Diff-based migration workflow for safe schema iteration
• .env.local with local connection credentials

Error Handling

Error	Cause	Solution
Cannot connect to Docker daemon	Docker not running	Start Docker Desktop, then retry npx supabase start
Port 54321 already in use	Previous instance still running	Run npx supabase stop then npx supabase start
supabase db reset fails	Syntax error in migration SQL	Check the failing migration file, fix SQL, re-run reset
Permission denied on start	Docker socket permissions	Add user to docker group: sudo usermod -aG docker $USER
supabase db diff empty	No schema changes detected	Verify changes were made in the local DB, not just Studio UI cache
relation "auth.users" does not exist	Running migration outside Supabase	Auth schema only exists in the Supabase-managed Postgres instance

Examples

Connect from Application Code

import { createClient } from '@supabase/supabase-js'

const supabase = createClient(
  process.env.SUPABASE_URL!,       // http://localhost:54321 locally
  process.env.SUPABASE_ANON_KEY!   // Local anon key from supabase start
)

// Fetch profiles — works identically in local and production
const { data, error } = await supabase
  .from('profiles')
  .select('username, avatar_url')
  .limit(10)

Test Against Local Instance with Vitest

import { createClient } from '@supabase/supabase-js'
import { describe, it, expect, beforeAll } from 'vitest'

const supabase = createClient(
  'http://localhost:54321',
  'eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9...'  // Local anon key
)

describe('profiles', () => {
  beforeAll(async () => {
    // Seed data is already loaded via supabase db reset
  })

  it('fetches public profiles', async () => {
    const { data, error } = await supabase
      .from('profiles')
      .select('username')
      .limit(1)

    expect(error).toBeNull()
    expect(data).toHaveLength(1)
    expect(data![0].username).toBeDefined()
  })

  it('enforces RLS on update', async () => {
    // Anon users cannot update profiles (no auth.uid())
    const { error } = await supabase
      .from('profiles')
      .update({ username: 'hacker' })
      .eq('username', 'alice')

    expect(error).not.toBeNull()
  })
})

Edge Function Local Development

# Create and serve an Edge Function with hot reload
npx supabase functions new hello-world
npx supabase functions serve --env-file .env.local

# Test it
curl -X POST http://localhost:54321/functions/v1/hello-world \
  -H "Authorization: Bearer $SUPABASE_ANON_KEY" \
  -H "Content-Type: application/json" \
  -d '{"name": "World"}'

Resources

• Local Development Overview
• Supabase CLI Reference
• Database Migrations
• Edge Functions Quickstart
• Row Level Security

Next Steps

Proceed to supabase-sdk-patterns for production-ready client initialization, typed queries, and real-time subscriptions.