Interface HttpRequestOptions<T, TReq>

Either-returning response decoder. Returns Left(DecoderError) on failure; the framework maps that to HttpError.DecodeError(cause: DecoderError). The recursive DecoderError tree preserves structural failure info (paths, child errors) for diagnosis and rendering.

For adapters whose primary API throws (e.g. Zod's .parse), use an adapter package (e.g. functype-zod's Decoder.fromZod(schema)) or wrap the throwing function in a tiny custom decoder. The deprecated validate field is also still accepted for back-compat.

Request-side encoder. When set, the body goes on the wire as JSON.stringify(encode(body)) with Content-Type: application/json, and flatten is ignored. Use it when flatten can't express the wire shape: custom date formats, snake_case keys, stripping fields. A throw inside encode fails the request with HttpError.NetworkError, like any body that can't be serialized.

It applies to the body after beforeRequest runs, so a hook that swaps the body must keep it a TReq.

TReq is inferred from encode. If you pass the response type explicitly (Http.post<User>(…)), pass the request type too (Http.post<User, NewUser>(…)): TypeScript defaults the rest to unknown, and an Encoder<NewUser> won't fit Encoder<unknown>.

Whether to flatten functype ADTs in the request body to their primitive projections (Option → nullable, Either → right-value-or-throw-on-Left, List → array, Try → success-value-or-throw, Map → record) before serializing. Default true — matches the wire shape external JSON APIs expect.

Set to false to emit each ADT's canonical {_tag, value} form via toValue() for functype-to-functype services where both ends round-trip the tagged shape via Decoder.tagged.*.

Ignored when encode is set.

Query-string parameters appended to the URL. Merges with any query string already present in url. See HttpQueryParams for encoding rules.