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POST
auth.signin.start

Authorizations

Authorization
string
header
required

A Lath API key: lath_live_sk… or lath_test_sk… on a server, lath_live_pk… or lath_test_pk… in a browser.

Headers

Idempotency-Key
string

Replays the stored response for the same key and input; refuses different input.

Body

application/json
method
enum<string>
required
Available options:
email_code,
email_link,
sms_code
identifier
string
required

The email address, or the E.164 phone number for sms_code

Required string length: 3 - 320
redirectTo
string<uri>

For email_link: where the hosted landing page sends the user afterwards

locale
string

Send the sign-in message in this language, if a variant of the template exists for it. Omit to use the user's recorded language, which a first-time visitor does not yet have.

Maximum string length: 20

Response

{ activityId, result }. activityId is empty for reads.

activityId
string
required

The activity this call created, or empty for a read.

result
object
required
Last modified on September 13, 2026