coss.com

The foundation the world's apps are built on.

Email, SMS, video and scheduling, behind one SDK and one API key. Give your coding agent one prompt and every part is wired in, so you ship the product only you can build.

Quickstart
The COSS platform: email, SMS, video and scheduling seated along the front of one base, with the keys, domains, webhooks and logs they share seated behind them.npm install cossnew Coss()COSScoss.domainsCOSScoss.emailCOSSverifyWebhook()COSScoss.smsCOSScoss.logsCOSScoss.videoCOSScoss.schedulingCOSSProductsemail · sms · video · schedulingPlatformkeys · domains · webhooks · logs

Catalog

Every product runs on the same key, the same SDK and the same platform, so the next one you add needs no new setup.
01

Email

coss.email

Transactional email from your own domains, tracked to every recipient.

  • Single, batch and scheduled sends
  • Per-recipient delivery events
  • Open and click tracking
02

SMS

coss.sms

Text messages worldwide, on the same key, events and logs as email.

  • Send and receive
  • Delivery events on your webhooks
  • Shared suppressions and logs
03

Video

coss.video

Rooms and recordings for the calls inside your product.

  • Rooms on demand
  • Recordings
  • Call events on your webhooks
04

Scheduling

coss.scheduling

Availability and bookings, from the team behind Cal.com.

  • Availability across calendars
  • Bookings and reschedules
  • Booking events on your webhooks

One vendor, not four

Every channel you add usually means another account, another SDK, another dashboard and another invoice. With COSS, the next one is already set up.

Four vendors

4 integrations
  • Four accounts and four sets of keys
  • Four SDKs to learn and keep updated
  • Four webhook formats to verify
  • Four dashboards to search when something breaks
  • Four invoices
  • Start over for every new channel

With COSS

1 integration
  • One account, one key per environment
  • One SDK for every product
  • One webhook format and signature
  • One log across every product
  • One bill
  • The next product is already set up

Assembly takes one prompt

COSS is written for the agent doing the work as much as for you: plain-text docs, typed results, and keys that can't send by accident.

Add COSS to this project: read https://coss.com/llms.txt, install the `coss` package, and develop with a coss_test_ key.

  1. 1

    Copy one prompt

    One line for Claude Code, Cursor or Codex. It points your agent at the manual and tells it how to test.

  2. 2

    Your agent reads the manual

    /llms.txt indexes every docs page in plain text. The API reference and the SDK's types come from one OpenAPI document.

  3. 3

    It tests with a sandbox key

    coss_test_ keys record every email and event and deliver nothing, so the agent can run its code for real.

agent session
  1. Add COSS to this project: read https://coss.com/llms.txt, install the `coss` package…
  2. Fetch coss.com/llms.txt
  3. Fetch coss.com/docs/email/sending
  4. Fetch coss.com/docs/webhooks
  5. Bash npm install coss
  6. Write src/lib/coss.ts
  7. Write src/app/api/webhooks/coss/route.ts
  8. Bash npx tsx scripts/send-test.ts
  9. email_01k7c8m4q2f3e9v6t5r1n0p8yz queued
  10. Email and signed delivery webhooks are in. The test send was recorded with your sandbox key; nothing was delivered.
An illustrative session. What your agent does depends on your project.

Interfaces for agents

Tolerances

The numbers your code can rely on. The docs list every limit in context.
Batch send
100 emails, all or nothing
Scheduling window
30 days ahead
Attachments
20 per email, 25 MB combined
SDK retries
2, honoring Retry-After
SDK timeout
30 s per attempt
SDK runtimes
Node, Bun, Deno, Workers
SDK dependencies
0
Webhook signatures
Standard Webhooks
Webhook timeout
10 s per attempt
Log search
31 days per query
Suppression import
1,000 entries per request
Send body limit
40 MB

Also from coss.com

More from the team behind coss.com, each with its own pages here.

ShipyardNew

Shipyard runs Claude Code, Codex and other coding agents on your own dev boxes. Work with them from your laptop; close it, and they keep going.

About ShipyardDocs

kloqNew

A React calendar obsessed with micro-perfection: hand-tuned drag physics, a design mode that annotates its own craft, and a command palette that reaches everything. One component, on coss ui.

About kloqLive demo

Fit your first part before your coffee cools.

Start free with 3,000 emails a month. Sandbox keys are never billed.

Read the docs