letmepost.dev

A publishing API that fails loudly.

Open-source social media publishing API for developers and AI-agent builders. Every failure response carries the rule that failed, the raw platform body, and a remediation — never an empty { body: {} }. No per-profile tax.

Status — alpha. Bluesky works end-to-end. LinkedIn next. Meta and YouTube are review-gated by the platforms (3–12 weeks). See plan.md.

letmepost.dev · PRODUCT.md · TECH.md · plan.md

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Why this exists

Four things developers hit every week with incumbent social-media APIs:

1. Silent failures. Posts report success then never appear. Error bodies come back as {}.
2. API version churn. LinkedIn sunset five API versions in six months; every sunset broke n8n, Zapier, Make, Pabbly, and Postiz.
3. Async media rejections. YouTube's restricted-scope mismatches surfacing as generic forbidden, Threads' OAuthException 2207052, Instagram Reels rejecting Google Drive URLs — all catchable client-side.
4. Per-profile pricing. $6–12 per channel, per month, forever.

letmepost.dev addresses all four, in one API.

Four guarantees on every request

1. Preflight, not postflight. Character counts, media formats, URN patterns, audit states — all validated locally before the upstream call.
2. Transparent errors. Stable code + the rule that failed + the raw platform body + a remediation hint. Always.
3. Pinned platform versions. We pin the header, track deprecations, upgrade internally. Your workflow doesn't break at 2 a.m.
4. Idempotency by default. Every write accepts an Idempotency-Key. Retries are safe.

The shape

Request:

curl -X POST https://api.letmepost.dev/v1/posts \
  -H "Authorization: Bearer lmp_live_…" \
  -H "Idempotency-Key: $(uuidgen)" \
  -H "Content-Type: application/json" \
  -d '{
    "account": { "platform": "bluesky", "id": "acc_…" },
    "text": "Shipping letmepost.dev"
  }'

Failure:

{
  "error": {
    "code": "preflight_failed",
    "rule": "bluesky.text.max_graphemes",
    "platform": "bluesky",
    "platform_version": "atproto-2026-04",
    "message": "Post text is 312 graphemes; Bluesky allows at most 300.",
    "remediation": "Shorten the post to 300 graphemes or fewer.",
    "request_id": "req_01HY6X4AWBJM2K9F2PTQMRD9JQ"
  }
}

Same shape, every time.

Running locally

Prerequisites

• Node >=24 (see .nvmrc)
• pnpm 10.33.0+ (corepack enable if you don't have it)

Install and run

pnpm install
pnpm dev            # API + web in watch mode (turbo)
pnpm test           # vitest across the workspace
pnpm typecheck
pnpm build

Individual apps

pnpm --filter @letmepost/api dev     # API only → http://localhost:3000
pnpm --filter @letmepost/web dev     # Landing site → http://localhost:4321

Repo layout

apps/
  api/                 # Hono HTTP API — core product
  web/                 # Astro landing site (letmepost.dev)
packages/
  schemas/             # Zod — single source of truth for validation, types, OpenAPI
  config-tsconfig/
  config-eslint/

Landing later as the stack grows: apps/dashboard/ (Next.js), packages/openapi/ (generated 3.1 spec), packages/sdk-ts/ (published to npm), plus sibling repos letmepost/sdk-python and letmepost/sdk-go auto-generated from the spec. See TECH.md for the full target tree.

Platform support

Platform	Status
Bluesky	live
LinkedIn	next (~3 weeks)
Twitter / X	soon
Instagram · Facebook · Threads	soon (Meta review starts day 0)
YouTube	later (CASA verification starts day 0)
Pinterest	later

TikTok is deferred to v2 — schemas + DB enum keep it reserved so the v2 add is additive. Deliberately cut from v1: Reddit, Telegram, Discord, Snapchat, Google Business, WhatsApp. Reasoning in PRODUCT.md.

Contributing

Building in the open. File an issue when something's weird; read PRODUCT.md before PRs that touch product surface area and TECH.md for implementation decisions.

License

Apache 2.0. Same code runs the hosted SaaS and the self-host Docker Compose — no feature gate, no open-core trick.