API
1MSG API: A New Foundation for WhatsApp Integrations
We’ve completed one of the largest backend changes in 1MSG history. 1MSG API is now running across our full production fleet — a modern, typed service built on NestJS and TypeScript.
Nikita L ·
If you’re already integrated with 1MSG, nothing breaks. Your endpoints, URLs, tokens, and response formats work as before. What changed is almost entirely under the hood — and that’s exactly the point.
Why we rebuilt the backend
Our API served customers well, but the stack behind it was aging: JavaScript, loosely coupled contract and implementation, growing complexity with every new message type and production edge case.
1MSG API is not a new product launch. It’s a platform release: the same public API you rely on today, rebuilt on a foundation designed to scale, evolve, and ship safely.
What changed under the hood
1. A complete production core replacement
We didn’t patch the old service — we replaced it.
The entire channel-server fleet now runs on versioned container images, deployed through controlled, repeatable rollouts in our CI/CD pipeline.
This is a full runtime and deployment change — not a cosmetic refactor.
2. Contract-driven architecture: OpenAPI as the source of truth
The new stack is built OpenAPI-first. The API specification is no longer documentation that chases the code — it is the code generator.
From a single contract we generate:
- Server controllers
- A typed TypeScript SDK
- An MCP server for agent and IDE integrations
Generated transport layer (routing, validation, types) is cleanly separated from business logic. One generation pipeline keeps the server, SDK, and tooling in sync when the API evolves.
3. Seamless migration without breaking existing integrations
The hardest part of a backend rewrite isn’t writing new code — it’s preserving years of real-world behavior.
We ported and validated everything existing customers depend on:
- Message flows: text, media, templates, buttons, lists, contacts, location, reactions, carousel, products, and WhatsApp Flows
- Incoming webhooks, status updates, acknowledgements, and customer webhook forwarding
- Groups API, WABA proxy behavior, and more
- Token resolution from query parameters, request body, and Authorization headers
- Original URL shape:
https://api.1msg.io/{instanceId}/...?token=... - HTTP response parity: status codes, error bodies, endpoint aliases, and subscription-blocked behavior
- CORS preflight handling before authentication
Before the first user-facing production deploy (June 19, 2026), we ran canary deployments, smoke tests, and parity checks. The full fleet rollout completed on July 2, 2026.
The bottom line
We built a new platform, moved the entire production fleet onto it, and preserved full backward compatibility with existing integrations.
1MSG API is the foundation for everything that comes next: safer API changes, better developer tooling, and a backend we can evolve with confidence.