---
title: "Create a domain connection (idempotent per app + domain)"
method: POST
path: "/connections"
tags: ["Connections"]
---

# Create a domain connection (idempotent per app + domain)

`POST /connections`

## Request

- Base URL: `https://api.customdomain.ai/v1`
- URL: `https://api.customdomain.ai/v1/connections`
- Auth: one of:
  - HTTP bearer
  - HTTP bearer
  - OAuth 2 (authorization code, authorization URL `https://api.customdomain.ai/oauth/agent/authorize`, token URL `https://api.customdomain.ai/oauth/agent/token`, scopes: `domains:connect`)

Starts connecting `domain` under the calling application and returns the connection plus its authoritative desired record set. Idempotent: if the app already has a non-failed connection for the domain, that existing connection is replayed with `200`.

A domain another application already serves live is refused with `409 domain_already_connected` before anything is written: move it by disconnecting it there first. When the ownership TXT flow is on the claim is accepted instead, and the ownership challenge decides it.

Callable from the widget (a widget JWT) or straight from your server with an API key, in which case the connection is created on the key's application, or on `application_id` when that names another application of the same tenant.

A delegated agent token needs `domains:connect` and creates the connection on its own application.

A workspace with no subscription yet connects its first ten domains, or the number an operator set, without one (`first_domain_free` and `free_domains` on the billing reads): a retry of the last of them is still replayed with `200`, and the next domain is refused with `402 billing_required` until the workspace starts its trial. A domain that is still waiting for its records can be removed with `DELETE /connections/{id}`, which frees its place at once.

## Request body

- object: The body is decoded with unknown fields REJECTED, so the properties below are exactly the accepted set: any other key is a `400`. Everything besides `domain` is optional.
  - `domain` string, required
  - `application_url` string, uri: Origin the edge reverse-proxies this connection's traffic to (Power). Validated on the way in: it must be an absolute `http(s)` URL with a public host; private, loopback and cloud-metadata targets are rejected with a `400`. Power is part of the Growth plan and up: on a plan without it the create is refused with `402 plan_upgrade_required` and nothing is stored. Omit to leave the edge on its own router.
  - `www_redirect` boolean: Serve an apex↔www redirect for this connection.
  - `override_spf` boolean: Replace an existing SPF record instead of merging into it. Honoured only for providers whose connection check reports `spf_override_support` as true; for every other provider the existing record is merged, as when this is false.
  - `validate_dmarc` boolean: Accepted, stored with the connection and echoed back. It is not acted on yet: DMARC is not checked during verification today.
  - `validate_caa` boolean: Adds the two apex CAA records that authorize Let's Encrypt (`issue` and `issuewild`) to the connection's desired record set, skipping any already present. No separate CAA check is run against the domain's existing records. Edge routing only: a domain routed to your own infrastructure (a connect target) gets its certificate there, so no CAA records are added for it.
  - `monitor` boolean: Enrol the domain in drift monitoring: once the connection goes live the control plane registers a drift watch and the hourly sweeper re-checks the connection's DNS records, emitting `domain.record_missing` / `domain.record_restored` when they change. Unlike the four flags above this one DEFAULTS TO TRUE: omitting it enrols the domain. That is deliberate back-compat: the watch used to be registered unconditionally, so every connection created before this flag was honoured is monitored, and every existing integrator omits the field. Send `false` to opt a connection out; the value is echoed on the connection and is the only thing that decides whether the watch is registered. The plan's Monitor entitlement is not enforced today: monitoring is registered for every connection that has this on, regardless of plan.
  - `batch_id` string: Caller-supplied id correlating every domain connected in one multi-domain session. Stamped on each connection and echoed back; empty for a standalone connect. Set once at create.
  - `end_user_ref` string: The integrator's OWN identifier for the end user this connect is attributed to, so the console can render "Connected by …" and search by customer. Empty ⇒ a console/direct connect. Set once at create and never mutated.
  - `end_user_email` string, email: Optional. The email address of the end user this domain is connected for. After a Move they get one email with the new DNS records, sent on your behalf and naming your application (at most 3 per connection in 30 days). It wins over an address given when the token was minted, is stored only on the connection, and is shown back only in this call's response and on `GET /connections/{id}` with an API key.
  - `application_id` string: API key callers only: create the connection on this application of the key's tenant. A widget or agent token may only name its own application (anything else is a `403`).

## Response `200`

Existing connection replayed (idempotent)

- ConnectionWithRecords
  - `id` string, required
  - `application_id` string, required
  - `domain` string, required
  - `host` string: subdomain label; empty means the apex
  - `provider_id` string: detected / applied DNS provider
  - `setup_type` 'automatic' | 'manual' | 'async' | 'mcp', required: How a connection reaches live.
  - `status` 'pending' | 'propagating' | 'live' | 'failed', required
  - `managed` boolean: `true` when the connection opted into **managed mode**: the control plane holds a durable, encrypted async grant and can re-apply (`POST /v1/connections/{id}:reapply`) or revert (`DELETE /v1/connections/{id}`) the template server-side without re-consent. Omitted (treated as `false`) for the default use-once connection.
  - `created_at` string, date-time, required
  - `sandbox` boolean: `true` when the connection belongs to a test mode application. Its DNS is simulated, nothing real is read, written or served, and it counts for nothing (no free domain, quota, billing or metering). Copied from the application at create and never changed. Omitted (treated as `false`) on a real connection.
  - `last_checked_at` string, date-time: When the propagation poller last examined this connection. Omitted until the first check.
  - `www_redirect` boolean: Serve an apex↔www redirect. Echoed from create.
  - `override_spf` boolean: Replace an existing SPF record instead of merging into it, where the provider supports it. Echoed from create.
  - `validate_dmarc` boolean: Stored and echoed from create; not acted on yet.
  - `validate_caa` boolean: Whether the Let's Encrypt CAA records are part of the desired record set. Echoed from create.
  - `monitor` boolean: Whether the domain is enrolled in drift monitoring. Echoed from create, where it defaults to true when omitted, and honoured: the drift watch is registered when the connection goes live only if this is true. Connections created before the flag was honoured read true (they were monitored unconditionally, and were backfilled), so this is false only where a caller explicitly opted out.
  - `batch_id` string: The multi-domain session this connection was created in. Omitted for a standalone connect.
  - `end_user_ref` string: The integrator's own identifier for the end user who connected this domain. Omitted for a console/direct connect.
  - `retried_at` string, date-time: When a human (or the create-path resume, or real edge traffic) last asked for this connection to be re-verified. The retry clock is max(created_at, retried_at): a revived connection gets a fresh window from here, not from its original creation. Absent when it was never retried.
  - `routing` ConnectionRouting
    - `mode` 'edge' | 'custom', required: `edge`: records point at the CustomDomain™ edge. `custom`: at your own infrastructure.
    - `cname_target` string: For `custom`: the hostname subdomains and ALIAS-capable roots point at.
    - `apex_ipv4` string[]: For `custom`: the addresses roots get on DNS providers with no ALIAS-style record.
    - `set_at` string, date-time, required: When this routing was recorded for the domain.
  - `records_source` 'integrator': Present as `integrator` when the connection's desired record set was supplied through `PUT /v1/connections/{id}/records` rather than authored by us. Omitted for the usual server-synthesized or Domain Connect template-materialized set. Such a connection cannot use the Domain Connect rail, which applies our published templates at the provider.
  - `created_via` '' | 'widget' | 'console' | 'api' | 'agent' | 'mcp': Where the connection was created, recorded once at create and never changed. `widget`: an end user's connect-scoped widget token (the embedded widget in your product). `console`: the CustomDomain™ console. `api`: an API key, or an app-scoped token, from your server. `agent`: a delegated agent access token. `mcp`: the MCP server. Empty for connections created before this was recorded. A trusted server-side caller may name its surface with the `X-CustomDomain-Client` request header (`console` or `mcp`); the header is a label only and grants nothing.
  - `secure_root_domain` boolean: The edge also issues/secures the registrable apex alongside this subdomain connection. Omitted (treated as `false`) when unset.
  - `redirect_to` string, uri: URL the edge 301s this host to (Power redirect target). Omitted when the connection is not a redirect.
  - `power_root_path_access` string[]: URL paths the edge may static-serve at the root (Power root-path access). Omitted when none are configured.
  - `error_code` string: The last failure reason recorded for this connection, from whichever path failed, not only the background poller. It is persisted by: the propagation poller / `:recheck` verification (e.g. `propagation_timeout`, `setup_incomplete`, `pending_expired`, `domain_already_connected`); the foreground apply on `POST /connections/{id}/apply` (e.g. `dns_write_failed`, `ProviderAuthenticationError`, `spf_merge_failed`, `apex_not_supported`, `forwarding_not_supported`); the OAuth callback (which also records `forwarding_not_supported`); and the Domain Connect async callback (both e.g. `provider_unavailable`, `ProviderAuthenticationError`, `apply_failed`, `internal_error`, or the provider's own `error` parameter). Rejected request validation (`400`) is deliberately NOT recorded here: a malformed request is not a connection failure. Omitted when healthy or never failed; cleared when the connection next verifies.
  - `error_message` string: Human-readable detail for `error_code`. Populated on the same paths and cleared alongside it. Omitted when there is none.
  - `write_rail` 'api_key' | 'sign_in' | 'domain_connect' | 'domain_connect_async' | 'route53_role' | 'provider_account' | 'managed_dns': The rail that last wrote this connection's records. Omitted when no rail wrote them (a manual setup, or a connection from before this was recorded). It decides what removing the domain can do with the records (`GET /connections/{id}/removal`).
  - `provider_account_id` string: The connected provider account whose credential wrote this connection's records and, when the account's access is `continuous`, keeps them (repairs and removal). Omitted when none.
  - `removal_started_at` string, date-time: Set while the domain is being removed: the records are being taken out and the connection is deleted when that finishes. The domain no longer serves from this moment. Omitted otherwise.
  - `records` DnsRecord[], required
    - `type` string, required: DNS record type. `APEXCNAME` is the engine's provider-agnostic CNAME-at-the-apex type (a plain CNAME is illegal at a zone apex); it is realized to the host's native ALIAS / ANAME / flattened-CNAME on write, and shown to users as `ALIAS` in manual instructions.
    - `host` string, required: fully-qualified record name
    - `value` string, required
    - `ttl` integer
    - `priority` integer, nullable: MX only
    - `applied` boolean: true once written through a provider
    - `change` 'created' | 'added' | 'replaced' | 'merged' | 'existing': What writing this record did to its name, recorded when we wrote it through a provider API. `created`: nothing of this type was there. `added`: our value joined a shared TXT or CAA set and the values already there were kept. `replaced`: the values of this type at the name were replaced (`prior` holds them). `merged`: an SPF policy was merged with the one already there (`prior` holds the original). `existing`: our exact value was already there, so removing the domain leaves it. Omitted when not recorded (a manual or one-click setup, or a record written before this was recorded).
    - `prior` PriorValue[]: The values this record replaced, so removing the domain can put them back. Omitted when nothing was replaced or it is unknown.
      - `type` string, required
      - `value` string, required
      - `ttl` integer
      - `priority` integer
    - `prior_source` 'provider' | 'public_dns': Where `prior` was read: `provider` (through the provider's API right before the write) or `public_dns` (observed in public DNS before the change). Omitted when unknown.
  - `end_user_email` string, email: The end user's email address, when one was given and the feature is on. Present only on the response of the call that created the connection with it, and on `GET /connections/{id}` with an API key. Never in a list, a webhook, or any read by a widget token.
  - `ask_end_user_email` boolean: Present (true) on a create response only when the widget should offer the end user an optional email field: the feature is on, the caller is a widget token, the domain is not a test domain and the connection has no address yet. The widget then calls `PUT /connections/{id}/end-user-email`. Omitted otherwise.

## Other responses

- `201`: Connection created
- `400`: Error envelope: {code, title, details}.
- `401`: Error envelope: {code, title, details}.
- `402`: Refused because of the workspace's billing. `billing_required`: the workspace has no active or trialing subscription (a new workspace that has not started its trial, a Free workspace past its grace period, a comp that ended, or a subscription Stripe marked unpaid or canceled). It stops a new connection, the start of a domain purchase and the first live credential (an application, an API key or a rotated client secret). Domains already connected keep working, and an owner or admin sets up billing in the console; `details` says where. A new workspace's first domain is the exception: while it has fewer pending, propagating or live connections than its free domains (ten, unless an operator set another number: `free_domains`), a connect and the start of a purchase go through (`first_domain_free`), and the next one is refused with a `title` saying a card is needed to connect more domains. Credentials still need the trial. `quota_exceeded` (connections only): a plan that is refused past its quota (Starter, and the retired Free) is at it and the deployment enforces quotas. `connections_unavailable`: what a connect-scoped widget token, the tenant's own end user, gets instead of either, with neutral wording, so the tenant's customers are never told about the tenant's billing. A delegated agent token gets the full wording, and `GET /billing/standing` tells it beforehand whether a new connection would be refused.
- `403`: Error envelope: {code, title, details}.
- `409`: `domain_already_connected`: another application already serves this domain live. Disconnect it there first, then connect it here.
- `422`: `apex_not_supported`: the domain is a root domain, the application routes to its own infrastructure, the domain's DNS provider has no ALIAS-style record, and the application has no `apex_ipv4` to use instead. Connect a subdomain such as `www`, or add root addresses to the application's routing (`PUT /applications/{id}/connect-target`).

---

[API](https://skmtc.dev/customdomain/apis/customdomain-control-plane-api.md) · [All operations](https://skmtc.dev/customdomain/apis/customdomain-control-plane-api/llms.txt) · [OpenAPI document](https://skmtc.dev/customdomain/apis/customdomain-control-plane-api/revisions/34d89cb7a7cd?raw)