PostMost

A reseller operating system that lets you create one listing and cross-post it to multiple marketplaces.

Stack

• Next.js 16 (App Router)
• TypeScript
• Tailwind CSS + shadcn/ui
• Prisma + Postgres (Neon in production, with a local-Postgres fallback outside production -- see Environment below)
• NextAuth (credentials)

Features

• Universal listing form
• Cross-post queue and status tracking
• Marketplace adapter architecture (eBay, Etsy, Poshmark, Mercari, Depop, Facebook Marketplace, Craigslist, OfferUp, Vinted, Grailed)
• Dashboard with listing stats
• Inventory tracking with cost basis and profit
• Sales analytics with CSV export
• Bulk delist/relist
• Authentication

Setup

Needs a local Postgres. docker-compose.yml provides one (persistent, isolated from production):

docker compose up -d
npm install
npx prisma migrate dev
npm run seed
npm run dev

Open http://localhost:3000 and sign in with [email protected] / demo123.

Environment

Copy .env.example to .env and set at least:

Variable	Purpose
DATABASE_URL / DIRECT_URL	Pooled and direct Postgres connection strings
NEXTAUTH_URL, NEXTAUTH_SECRET	NextAuth base URL and signing secret
MASTER_KEY	64-char hex used only to encrypt marketplace tokens at rest
INNGEST_DEV	Set to 1 for local dev, so the SDK talks to npx inngest-cli@latest dev instead of Inngest's cloud
INNGEST_EVENT_KEY / INNGEST_SIGNING_KEY	Production only -- from an app at app.inngest.com
BROWSER_WORKER_URL / BROWSER_WORKER_SECRET	Production only -- see worker/README.md. Unset locally: manual-adapter platforms run in-process instead
STORAGE_PROVIDER	Storage adapter to use (default r2)
R2_ACCOUNT_ID	Cloudflare account ID (used to build the R2 S3 endpoint)
R2_ACCESS_KEY_ID / R2_SECRET_ACCESS_KEY	R2 API token credentials with object read/write on the bucket
R2_BUCKET	R2 bucket name that stores listing photos
R2_PUBLIC_BASE_URL	Public CDN/custom-domain base URL images are served from (e.g. https://images.postmost.co)
S3_ENDPOINT	Optional S3 endpoint override for another S3-compatible host (e.g. MinIO locally); defaults to R2
NEXT_IMAGE_HOSTS	Optional extra comma-separated hostnames allowed for next/image
BG_REMOVER	Background-removal adapter: birefnet (default) or photoroom
FAL_KEY	fal.ai key used by the BiRefNet adapter
BIREFNET_MODEL / BIREFNET_RESOLUTION	Optional BiRefNet variant and operating resolution
PHOTOROOM_API_KEY	PhotoRoom key for the premium fallback
RESEND_API_KEY	Resend key used to send password-reset emails
EMAIL_FROM	From address for outgoing email; must be a domain verified in Resend

Outside production, a DATABASE_URL that is not a *.neon.tech host uses Prisma's standard TCP client instead of the Neon serverless driver, so a local Postgres works without any code change.

Image storage

Listing photos live in object storage, not in the database. lib/storage/ mirrors the marketplace adapter pattern: lib/storage/types.ts defines StorageAdapter, lib/storage/adapters/r2.ts implements it with the AWS S3 SDK pointed at Cloudflare R2, and getStorage() picks the adapter from STORAGE_PROVIDER. Because it speaks the plain S3 API, swapping to AWS S3 or any other S3-compatible host is a new adapter plus config — no caller changes.

Upload flow (browser never proxies bytes through the serverless function, so the 4.5 MB body limit doesn't apply):

1. The listing form POSTs file metadata to /api/upload, which requires a session (401 otherwise) and rejects non-image types or files over 10 MB.
2. The route returns presigned PUT URLs plus the public CDN URL for each key (listings/<userId>/<uuid>.<ext>).
3. The browser PUTs each file directly to R2 and stores the returned https:// URL on the listing.

AI "Enhance photo" results are uploaded the same way, so enhanced images are hosted URLs too. Legacy base64 data: photos already in the database still render, still validate, and still cross-post through the extension.

Required R2 bucket CORS policy

The browser PUTs uploads directly and the extension re-fetches images to attach them to marketplace forms, so the bucket (and the custom domain in front of it) needs CORS. In the Cloudflare dashboard under R2 > your bucket > Settings > CORS policy:

[
  {
    "AllowedOrigins": ["https://your-app-domain.com", "http://localhost:3000"],
    "AllowedMethods": ["GET", "HEAD", "PUT"],
    "AllowedHeaders": ["content-type", "cache-control"],
    "ExposeHeaders": ["etag"],
    "MaxAgeSeconds": 3600
  },
  {
    "AllowedOrigins": ["*"],
    "AllowedMethods": ["GET", "HEAD"],
    "AllowedHeaders": ["*"],
    "MaxAgeSeconds": 86400
  }
]

Public reads require either R2 public access or a custom domain bound to the bucket; point R2_PUBLIC_BASE_URL at it.

Background removal

lib/ai/background/ is a provider registry in the same shape as storage and marketplaces: getBackgroundRemover() resolves BG_REMOVER (default birefnet), and getConfiguredBackgroundRemover() falls back to whichever provider actually has credentials so a missing key degrades instead of throwing. Adapters return raw cut-out bytes; lib/ai/optimize.ts encodes them as a data: URL that the listing form uploads to storage, so enhanced photos end up hosted like any other.

Adapter	Backend	Notes
birefnet	fal-ai/birefnet/v2	MIT-licensed weights, billed per GPU-second — the unlimited-removals default
photoroom	sdk.photoroom.com/v1/segment	Premium fallback for hair, sheer fabric, white-on-white; sandbox keys are watermarked

To compare providers on your own photos before choosing a production default:

npx tsx -r dotenv/config scripts/bake-off-bg-removal.ts --input ./samples --out ./bakeoff

This is the beginning of the README. Read the rest at the original. Read the full README ↗