Onramp error handling

Every error the App Kit SDK throws for Onramp is a KitError, exported from @circle-fin/app-kit. Its structured fields let you branch on the failure type instead of parsing message strings. For a full integration walkthrough, see the embed widget quickstart.

`KitError` fields

Field	Description
`type`	Classifies the failure. One of `INPUT`, `NETWORK`, `SERVICE`, `RATE_LIMIT`, `RPC`, or `UNKNOWN`.
`recoverability`	Indicates whether to retry. One of `RETRYABLE`, `RESUMABLE`, or `FATAL`.
`name`	Stable identifier for exact matching, logging, and telemetry.
`code`	Numeric sub-classification in a `name`. Stable identifier for telemetry.
`message`	Human-readable diagnostic. Not suitable for end-user display without review.
`cause`	The underlying error, if one was wrapped.

Prefer type and recoverability for control flow. They are the stable, forward-compatible contract. Use name and code only for exact matching, logging, and telemetry.

Error handling

Catch a KitError and branch on type and recoverability to decide how to recover:

TypeScript

import { KitError } from "@circle-fin/app-kit";

try {
  const session = await kit.onramp.fetchSession({ url, body });
  kit.onramp.mountIframe({ session, container });
} catch (err) {
  if (err instanceof KitError) {
    if (err.recoverability === "RETRYABLE") {
      return scheduleRetry();
    }
    if (err.type === "INPUT") {
      return showValidationError(err.message);
    }
    if (err.type === "RATE_LIMIT") {
      return showRateLimitToast();
    }
  }
  throw err;
}

Common error codes

Code	Name	Type	When it fires
`1907`	`INPUT_INVALID_API_KEY`	`INPUT`	API key is missing, invalid, or unauthorized (401 or 403).
`1910`	`INPUT_WIDGET_URL_ORIGIN_MISMATCH`	`INPUT`	`mountIframe` or `openWindow` called with a `widgetBaseUrl` that doesn’t match the server’s.
`1914`	`INPUT_NO_WINDOW`	`INPUT`	The client kit was used in a non-browser environment. Run client code in the browser, or pass a `window`.
`8923`	`SERVICE_SESSION_ENDPOINT_REJECTED`	`SERVICE`	Your session route returned a non-2xx response. Check auth on your route or the request body.

HTTP status code mapping

createSessionRouteHandler maps thrown errors to HTTP status codes automatically:

`type`	HTTP status	Meaning
`INPUT`	400	The request body failed validation.
`RATE_LIMIT`	429	Too many requests. Retry after a backoff.
`NETWORK`	504	Upstream connection failed or timed out.
`SERVICE`	502	Upstream service returned an error.
`RPC`	502	Upstream RPC call failed.
`UNKNOWN`	500	Unclassified error.

The handler also returns:

405 Method Not Allowed for any method other than POST.
400 Bad Request if the body cannot be parsed as JSON.
401 Unauthorized if your authorize callback returns false.

Upstream response bodies are never echoed into the response. Only the status code and length of the upstream response are kept on KitError.cause for diagnostic purposes.

Error sources

Source	Throws when	`type`
`new AppKit()`, `createAppServerKit()`	Constructor options are missing or invalid.	`INPUT`
`kit.onramp.mountIframe()`	The session has expired or is malformed, or the container is missing.	`INPUT`
`kit.onramp.openWindow()`	The session has expired or is malformed.	`INPUT`
`server.onramp.createSession()`	Input is invalid, the upstream API rejects the request, or the network fails.	`INPUT`, `NETWORK`, `SERVICE`, `RATE_LIMIT`
`kit.onramp.fetchSession()`	Your session route returns a non-2xx response, or the body can’t be parsed.	`INPUT`, `NETWORK`, `SERVICE`

Runtime widget errors are surfaced through the INITIALIZATION_ERROR event rather than thrown. See Handle lifecycle events.

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Onramp error handling

`KitError` fields

Error handling

Common error codes

HTTP status code mapping

Error sources

​KitError fields

​Error handling

​Common error codes

​HTTP status code mapping

​Error sources

`KitError` fields

Error handling

Common error codes

HTTP status code mapping

Error sources