Composition

Encrypt, compress, and compose Persist backends and codecs for IndexedDB and string-wire storage.

import { createStorage } from "@stainless-code/persist";
import {
  idbStateStorage,
  createIdbStorage,
} from "@stainless-code/persist/backends/idb";
import { createEncryptedStorage } from "@stainless-code/persist/backends/encrypted";
import { createCompressedStorage } from "@stainless-code/persist/backends/compressed";
import { serovalCodec } from "@stainless-code/persist/codecs/seroval";
import { persistStore } from "@stainless-code/persist/sources/tanstack-store";

// Encryption at rest (AES-GCM WebCrypto) over IndexedDB. Encryption is a
// backend wrapper (crypto.subtle is async, the StorageCodec seam is sync),
// not a sync codec; idbStateStorage() in string-wire mode holds the encrypted base64.
const key = await crypto.subtle.generateKey(
  { name: "AES-GCM", length: 256 },
  true,
  ["encrypt", "decrypt"],
);
createStorage(
  () => createEncryptedStorage(() => idbStateStorage(), { key })!,
  serovalCodec(),
  {
    clearCorruptOnFailure: true,
  },
);

// Compress-then-encrypt (standard order) — the two wrappers stack
createStorage(
  () =>
    createEncryptedStorage(
      () => createCompressedStorage(() => idbStateStorage())!,
      { key },
    )!,
  serovalCodec(),
);

// Legacy string payloads in IDB (written by an older version)
createStorage(() => idbStateStorage(), serovalCodec());

// Namespaced IDB store away from other idb-keyval users
import { createStore } from "idb-keyval";
createIdbStorage({ store: createStore("my-db", "persist") });

// Cross-tab sync (localStorage): pair crossTab with onCrossTabRemove when using skipPersist
persistStore(store, {
  name,
  storage,
  crossTab: true,
  onCrossTabRemove: () => store.actions.reset(),
});

// Cross-tab over IDB: no storage events — bridge a BroadcastChannel via crossTabEventTarget

For the full IDB BroadcastChannel bridge, see Cross-tab.