From TypeScript + Effect

If you know Effect, Khora’s motivation should feel familiar: failures and capabilities belong in types, resource lifetimes should be structured, and concurrent work should have ownership.

The major difference is where that model lives. Khora builds those ideas into a native language/runtime rather than expressing them as a TypeScript library over the JavaScript/Node execution model.

Where the familiar pieces live

Effect	Khora
Effect<A, E, R>	a function’s return type, raises row and with row
Effect.either	attempt
Redacted	std::core::Redacted — same idea, and Show/Encode make it a compile error rather than a convention: a record holding one derives Decode and refuses Encode, where Effect’s Schema.Redacted round-trips the secret on its encode side by design
Config	std::config::read over a Schema<A>, which derive(Decode) writes from the type; see below
Schedule, retry, repeat	std::resilience
Clock.sleep, TestClock	std::clock::Clock — sleep is an operation on the capability, so a fake clock is a handler and needs no fork-or-deadlock caveat
Queue with dropping/sliding	Channel::dropping / Channel::sliding
Fiber.join	Fiber::join, which re-raises the child’s failure with its type
Effect.forkScoped	nursery.spawn(..)
Ref	Shared<A>
Layer	nothing — see below

Some things are deliberately absent. Effect.gen, pipe, dual APIs, branded types and Match are TypeScript workarounds; Khora has methods, nominal types, match, and let.

Direct style

Effect.gen and yield* disappear. A function calls effectful operations directly, inside the capability and failure context its own signature declares — there is no Effect<A, E, R> value to construct and compose:

// Effect
const loadUser = (id: Id) =>
  Effect.gen(function* () {
    const db = yield* Database;
    const row = yield* db.query(id);
    return User.from(row);
  });

// Khora
fn load_user(id: Id) -> User with { db: Db } raises UserError {
  User::of(db.query(id)!)
}

raises is the typed failure dimension, with is environmental authority, and postfix ! is where control can leave — the marks yield* was carrying. A handler is what supplies a capability for a scope; it is the value a with block binds.

The rows are named the other way round

Effect<A, E, R> calls them Errors and Requirements. Khora writes them as two separate rows, and the conventional names are two letters each so you cannot read them backwards:

fn call<A, 'ef, 'er>(body: () -> A with 'ef raises 'er) -> A
  with 'ef
  raises 'er

'ef is the capability row — Effect’s R. 'er is the failure row — Effect’s E. A single-letter 'e was ambiguous in exactly the direction that hurts somebody arriving from Effect, which is why it is not spelled that way.

No Layer, and that is the point

There is no Layer. A capability is built by an ordinary binding in the with block, once, in the order written — so there is nothing to memoize, and no way to get two structurally identical instances of the same dependency:

with {
  config: env_config(),
  scope: Scope::root(),
  db: postgres_db()!,
  store: sql_store(),
} {
  run_server()!
}

Built once, in the order written, by the ordinary rules of a binding. There is nothing to memoize because there is nothing being rebuilt.

No Config<A> description type either

std::config::read(schema) reads the whole configuration at once. It walks a Schema<A> — the same one that reads a JSON body — for the variables it needs, and answers Validated, so every bad key is reported in one pass and each is spelled as the variable it came from.

There is no description type to defer the read, because the Env handler is already what a test swaps. The schema is there for reuse rather than for deferral.

Interruption is not only at effect boundaries

In Effect, a tight loop inside one synchronous step cannot be interrupted. Khora separates scheduler safepoints from cancellation points and puts a cancellation point at every loop back-edge, every call to a function that can reach one, and every blocking operation, so a spinning loop is cancelable whatever its function’s raises row says. A cancellation does not travel on the error row: it has a return of its own, and a catch does not see it.

Pipelines

Khora’s |> is call-oriented. value |> f(a) means f(value, a), and a single _ placeholder can select another argument position. It is not limited to piping into unary functions.

Visibility is pub, not export

The one place the surface will read as less familiar than you expect. import is spelled the way you already spell it, but what marks a declaration public is pub:

pub type Entry = { id: Int, memo: String };

pub fn total(entries: List<Entry>) -> Int

It also appears on methods, which is why it is not export: nobody imports Map::get, they reach it by having a Map. A declaration without pub is private to its file, which is closer to a module with no export than to TypeScript’s default of exporting whatever is written at the top level.