40032: Invalid message extras field

A publish was rejected because a message included an extras field that is not permitted, or one whose value was the wrong type. Only recognized extras keys with values of the expected shape are accepted.

What you should do

Put only recognized Ably keys in a message's extras field, with values of the expected shape. To attach your own metadata, use extras.headers, which must be a flat map of string keys to string, number, boolean, or null values. Move any custom fields there and republish.

Why it happens

A message's extras contained a key Ably doesn't permit, or extras.headers had the wrong shape. extras is reserved for specific Ably features, so arbitrary top-level keys are rejected, as are headers that aren't a flat, string-keyed map of simple values.

What you'll see

The error is reported with code 40032 and HTTP status 400. The messages include Message has impermissible extras fields: <key> and extras.headers if present must be a map<string, string|number|boolean|null>.