HTTP

Use @formadapter/http when the endpoint is not a framework action or typed procedure.

bun add @formadapter/http

JSON

import { createHttpSubmission } from "@formadapter/http";

const submit = createHttpSubmission({
  url: "/api/profile",
  init: { credentials: "include" },
});

export function ProfileEditor() {
  return <Profile.Form onSubmit={submit} />;
}

JSON is the default. It sends the prepared schema input so the endpoint can validate and transform at its own trust boundary. The form abort signal is always forwarded.

Multipart and files

const submit = createHttpSubmission({
  url: "/api/profile",
  body: "form-data",
});

This sends FormAdapter's schema-aware FormData. Do not set content-type; fetch must add the multipart boundary.

A matching request handler

import { createRequestHandler, fieldError } from "@formadapter/server";
import { profileConfig, profileSchema } from "@/app/profile/profile-schema";

export const POST = createRequestHandler(
  profileSchema,
  async (profile) => {
    if (await database.user.exists({ email: profile.email })) {
      throw fieldError("email", "That email is already registered");
    }
    return database.profile.save(profile);
  },
  { config: profileConfig },
);

The request handler accepts JSON, multipart FormData, and URL-encoded POST bodies. It returns serialized SubmissionState JSON with appropriate status codes.

A successful endpoint response is wrapped as success unless it already returns a well-formed SubmissionState. Structured 4xx failures and intentional 4xx messages are preserved. Bodies from 5xx responses and exception details from network failures are never shown to users; they use errorMessage or a safe fallback. Abort errors are rethrown so cancellation still works.

init may be a function of the current submit context, and a custom fetch implementation is supported for tests or non-browser runtimes.