Notifications with a receipt.

One API for email, SMS, and in-app messages. Charon accepts each request once, carries it to the person it’s for, and keeps evidence of what happened.

Notification 0193a7c2

Email to acme.example

10:42:07.112 Accepted 202, key order-42
10:42:07.118 Queued outbox job 1 of 1
10:42:07.304 Dispatching mx1.example.net, TLS
10:42:08.951 Accepted by MX 250 2.0.0
10:42:09.010 Webhook email.submitted, signed

Delivered

Every message crosses once.

Accept once

The notification and its delivery job are saved together. A retry gets the first answer back.
Deliver carefully

Workers lease each job. Temporary failures retry, and permanent ones stop.
Keep the receipt

Every attempt leaves evidence, sent to you as signed webhooks.

Unknown

If a server drops the connection after taking a message, Charon marks it unknown instead of sending it twice.

One lifecycle for every channel.

DKIM-Signature: v=1; a=rsa-sha256; d=acme.example; s=charon1;

Email, sent direct

Sent straight to the recipient’s mail server, signed with your domain’s DKIM key.

“Your code is 482913” ✓1 segment, GSM-7

SMS you can predict

Segments are counted before sending, with a receipt for each one.

In-app feeds

A feed for each person, with unread counts.

One request to send.

Send a notification with an idempotency key. Charon answers 202 Accepted once the notification and its delivery job are stored together.

Retries never double-send: The same key returns the first answer. A new body with an old key gets a 409.
Your account comes from your key: Requests can’t name another account, and every query is scoped to yours.
Status without personal data: GET /v1/notifications/{id} returns state and timestamps, never the recipient or content.

POST /v1/notifications
Authorization: Bearer chr_live.<id>.<secret>
Idempotency-Key: order-42
Content-Type: application/json

{
  "channel": {
    "type": "email",
    "to": "[email protected]",
    "sender_domain_id": "8d3f…",
    "template_version_id": "0c21…",
    "variables": { "order_id": "42" }
  }
}

curl "$CHARON_URL/v1/notifications" \
  -H "Authorization: Bearer $CHARON_API_KEY" \
  -H "Idempotency-Key: order-42" \
  -H "Content-Type: application/json" \
  -d '{
    "channel": { "type": "in_app", "recipient_id": "user-1" },
    "body": "Your order is ready."
  }'

const response = await fetch(`${CHARON_URL}/v1/notifications`, {
  method: 'POST',
  headers: {
    authorization: `Bearer ${process.env.CHARON_API_KEY}`,
    'idempotency-key': `order-${order.id}`,
    'content-type': 'application/json',
  },
  body: JSON.stringify({
    channel: { type: 'in_app', recipient_id: user.id },
    body: 'Your order is ready.',
  }),
});

// response.status === 202

202 Accepted Idempotency-Replayed: false

Questions.

What does early access include?

An API key for the hosted service, and help setting up your sending domains and SMS senders. We start with the channels and volume you tell us about.

How do I know what happened to a message?

Ask the status API with the notification’s ID, or subscribe to signed webhooks for delivery, bounce, and complaint events.

Can I retry a request safely?

Yes. Send the same request with the same idempotency key and Charon returns the original answer instead of sending again.

What does Charon keep about my recipients?

Only what it needs to deliver and prove delivery. The status API never returns recipients or content, and logs never contain them.