Open state

open() is deliberately asynchronous — persistent browser storage is not synchronous, and pretending it is invites hidden hydration bugs.

import { createDurable } from "@0xsarwagya/durable-local";
 
const durable = createDurable();
 
const workspace = await durable.open("workspace", {
  initial: {
    title: "Untitled",
    blocks: [],
  },
});
 
console.log(workspace.value);   // { title: "Untitled", blocks: [] }
console.log(workspace.revision); // 1

When open() resolves, storage has been opened, the slot has been read, migrations (if any) have completed, validation (if any) has run, and the returned value is ready to use. There is no hidden hydration phase.

First open vs later open

• First open (nothing stored): the initial value is committed at revision 1 and returned.
• Later open: the stored value is returned; initial is ignored.

Changing initial in application code never mutates existing user data. If you need to change the shape of stored state, that is a migration.

Same-context coherence

Opening the same slot twice in one JavaScript context returns the same underlying handle. Two open() calls do not become independent realities — they share committed observation.

const a = await durable.open("workspace", { initial: EMPTY });
const b = await durable.open("workspace", { initial: EMPTY });
 
await a.set({ title: "Hello", blocks: [] });
b.value.title; // "Hello"

This is the same-tab equivalent of the cross-tab observation guarantee.

Namespacing

Applications with more than one instance can namespace their slots:

const editor = createDurable({ namespace: "editor" });
const settings = createDurable({ namespace: "settings" });

Slots under different namespaces cannot collide even when they share a name.