Capabilities and local preflight

Inspect supported fields and validate complete provider intent without acquiring credentials or sending.

Use email.capabilities to inspect the configured service, then call email.validate to apply preparation and the actual provider rules. A capability flag is a local support declaration, not a statement about account permission or remote acceptance.

Preflight without an account

Selected provider subpaths expose credential-free functions:

import { Effect } from "effect";
import { preflightPostmarkEmail } from "@corven/email-sdk/postmark";
import { preflightResendEmail } from "@corven/email-sdk/resend";

const message = {
  body: { text: "A fictional credential-free preflight example." },
  from: "sender@fictional.invalid",
  subject: "Fictional notification",
  to: "recipient@fictional.invalid",
};

export const fictionalLocalPreflight = Effect.gen(function* inspectFictionalIntent() {
  const resend = yield* preflightResendEmail(message, { idempotencyKey: "caller-owned-event" });
  const postmark = yield* preflightPostmarkEmail(message);

  return { postmark, resend };
});

This example validates the same message for Resend and Postmark, but supplies a key only to Resend. Giving Postmark an unsupported key must remain a local refusal.

A preflight function needs neither credentials nor an HTTP client. It does not authenticate, inspect account settings, reserve a schedule or prevent a later remote rejection. The CLI providers command lists the available offline profiles.

Preserve complete intent

The field-support table describes base profiles. Provider validation can add restrictions on mailbox formatting, body combinations, MIME types, tag syntax, header names, schedules and recipient evidence.

Do not delete a rejected field to force portability. Decide in application code whether a different message is acceptable, then prepare and approve that new intent explicitly.

Routed candidates

Routing preflights every selected candidate’s effective message, key and policy before transport. A compatible primary does not excuse an incompatible backup. The acquired routed capabilities describe common support, but they do not replace candidate validation or create cross-account replay guarantees.