Faults

A fault is raised by the runtime when something outside your code goes wrong. Faults are never declared, listed in fails, rejected or matched. A fault goes straight to the edge of the app, where the client gets a fixed code and the cause is logged:

Reacting to a provider's problem

Code that must react to a dependency's problem gets a domain failure from the place the problem arises. An integration maps the provider's conditions to failures you declare (Calling):

failures: {    provider.invalid_recipient: ReminderRejected    provider.rate_limited: ReminderDelayed}

The action then lists only those domain failures, never unavailable or outcome_unknown:

action send_reminder(todo: Todo) fails ReminderRejected, ReminderDelayed -> Receipt {    return attempt mail.send_reminder(todo)}

Defects

A runtime fault that comes from your code is a defect. Int overflow and the recursion limit (Recursion) end the operation with internal_fault, undo its writes, and log which one happened:

{  "event": "operation.failed",  "classification": "int_overflow",  "operation": "action:price_line",  "site": "domains/ordering/actions/price_line.jadpo:4",  "request_id": "req_0b1e…"}

Division by zero can't happen, because a divisor's type must exclude zero (Expressions and operators). A construction that fails at run time never reaches the client as a fault either, because it needs an attempt.

A bug in Jadpo

A defect the checker should have ruled out is a bug in Jadpo, not in your app. The client gets the same 500 internal_fault as for any defect, and nothing about Jadpo, the version or the cause is in the response. The operator's operation.failed line adds bug_in_jadpo: true and report, the address of the issue form, beside the build's version, the request_id and the .jadpo frames. It never holds a request body, a header or a setting value. A fault that is your own code's, such as an overflow, has bug_in_jadpo: false and report: null.

The jadpo command, jadpo dev and jadpo test aren't deployed apps. A panic in them prints a screen that says it is a bug in Jadpo and writes a crash file for you to read and attach to a report (When Jadpo itself fails). Jadpo sends nothing anywhere.