diff --git a/packages/shade-storage-encrypted/src/crypto.ts b/packages/shade-storage-encrypted/src/crypto.ts
index 4d6cf03..6c17c00 100644
--- a/packages/shade-storage-encrypted/src/crypto.ts
+++ b/packages/shade-storage-encrypted/src/crypto.ts
@@ -34,12 +34,16 @@ export {
   deriveBlobSlotId,
   deriveBlobKey,
   deriveBlobSigningSeed,
+  deriveVaultId,
+  deriveVaultContentKey,
+  deriveVaultSigningSeed,
 } from './crypto/kdf.js';
 export {
   AEAD_NONCE_LEN,
   AEAD_TAG_LEN,
   aeadSeal,
   aeadOpen,
+  randomNonce,
 } from './crypto/aead.js';
 export {
   COL,
diff --git a/packages/shade-storage-encrypted/src/crypto/aead.ts b/packages/shade-storage-encrypted/src/crypto/aead.ts
index 0a7ad48..aad7999 100644
--- a/packages/shade-storage-encrypted/src/crypto/aead.ts
+++ b/packages/shade-storage-encrypted/src/crypto/aead.ts
@@ -33,9 +33,32 @@ async function importKey(key: Uint8Array, usages: WebCryptoKeyUsage[]): Promise<
 }
 
 /**
- * Encrypt a plaintext blob with the given key and a deterministic nonce.
- * Returns `nonce || ct||tag` as a single Uint8Array suitable for direct
- * BLOB storage.
+ * A fresh random 12-byte nonce.
+ *
+ * AES-GCM tolerates key reuse but not (key, nonce) reuse: two ciphertexts
+ * sealed under the same pair leak the XOR of their plaintexts and, worse,
+ * the GHASH authentication subkey — the "forbidden attack", which yields
+ * tag forgery for that key. Mutable rows are re-sealed on every change
+ * (`saveSession` runs on each ratchet step), so a nonce derived from row
+ * identity alone repeats by construction.
+ *
+ * Random beats a counter here because the codec is shared across SQLite
+ * and Postgres and has no durable per-row write counter to lean on. At
+ * 96 bits, collision probability stays negligible far past any realistic
+ * number of re-saves.
+ */
+export function randomNonce(): Uint8Array {
+  return globalThis.crypto.getRandomValues(new Uint8Array(NONCE_LEN));
+}
+
+/**
+ * Encrypt a plaintext blob with the given key and nonce. Returns
+ * `nonce || ct||tag` as a single Uint8Array suitable for direct BLOB
+ * storage.
+ *
+ * Callers must pass a nonce that is fresh for this key — see
+ * {@link randomNonce}. Never derive one deterministically from row
+ * identity for a row that can be written more than once.
  */
 export async function aeadSeal(
   key: Uint8Array,
@@ -58,9 +81,19 @@ export async function aeadSeal(
 }
 
 /**
- * Decrypt a `nonce || ct||tag` blob. The expected nonce is verified against
- * the prefix to detect tampering before we even reach the AEAD; if the
- * caller passes a `expectedNonce`, mismatch throws before SubtleCrypto runs.
+ * Decrypt a `nonce || ct||tag` blob.
+ *
+ * The nonce always comes from the blob prefix, which is what makes the
+ * move to random nonces backward compatible: a blob sealed under the old
+ * deterministic scheme opens unchanged, because its nonce was already
+ * stored the same way.
+ *
+ * @param expectedNonce **Deprecated.** Only meaningful when the nonce is
+ * a pure function of row identity, which is exactly the pattern that made
+ * (key, nonce) repeat. It adds no tamper detection that the AEAD tag and
+ * the (table, column, pk) AAD do not already provide — a flipped bit in
+ * the nonce fails the tag. Retained so existing callers keep compiling;
+ * pass nothing.
  */
 export async function aeadOpen(
   key: Uint8Array,
diff --git a/packages/shade-storage-encrypted/src/crypto/kdf.ts b/packages/shade-storage-encrypted/src/crypto/kdf.ts
index 14c3ede..3ef4e84 100644
--- a/packages/shade-storage-encrypted/src/crypto/kdf.ts
+++ b/packages/shade-storage-encrypted/src/crypto/kdf.ts
@@ -106,12 +106,20 @@ export function deriveFieldKey(storageKey: Uint8Array, table: string, column: st
 }
 
 /**
- * Derive a deterministic 12-byte AEAD nonce from a row key (typically the
- * field key) plus (table, pk) binding. With per-field keys, deterministic
- * nonces are safe because each (key, plaintext) pair appears at most once
- * — re-saving the same row reuses the (nonce, key) pair only because the
- * plaintext also changes (chain ratchet, prekey state, etc.). The AAD
- * also binds (table, column, pk) so swapping is rejected on decrypt.
+ * Derive a deterministic 12-byte AEAD nonce from a row key plus (table, pk).
+ *
+ * @deprecated Unsafe for anything that can be written twice, which is every
+ * mutable row. The original rationale held that re-saving a row was fine
+ * "because the plaintext also changes" — but that is precisely the case
+ * AES-GCM forbids: reusing (key, nonce) across *different* plaintexts leaks
+ * their XOR and the GHASH subkey (the forbidden attack), enabling tag
+ * forgery. `saveSession` re-seals on every ratchet step, so the pair
+ * repeated by construction. Use {@link randomNonce} from `./aead.js`.
+ *
+ * Kept exported (it is part of the published surface via `index.ts` and
+ * `crypto.ts`) so consumers keep compiling. No caller inside this package
+ * uses it any more. Reading old data needs no migration: `aeadOpen` has
+ * always taken the nonce from the blob prefix.
  */
 export function deriveNonce(rowKey: Uint8Array, table: string, pk: string): Uint8Array {
   const out = hkdfDerive(rowKey, `shade-row-nonce-v1:${table}:${pk}`, 12);
@@ -161,3 +169,42 @@ export function deriveBlobKey(masterKey: Uint8Array, app: string): Uint8Array {
 export function deriveBlobSigningSeed(masterKey: Uint8Array, app: string): Uint8Array {
   return hkdfDerive(masterKey, `shade-blob-sig-v1:${app}`, 32);
 }
+
+// ─── V4.13 — vault (server-side encrypted file store) ──────────
+//
+// The blob primitive above holds ONE small blob per slot. A vault holds
+// a whole collection — a project workspace, a mailbox, a drive folder —
+// as content-addressed objects plus an append-only log of manifests.
+//
+// Its own HKDF branch rather than a reuse of `shade-blob-*-v1`, for two
+// reasons. A vault key is used on far more ciphertext than a profile
+// blob ever is, and the two have different blast radii: whoever holds
+// the vault key can read every file, while the profile key exposes only
+// the host list. Separate labels mean compromising one cannot be turned
+// into the other, even though both hang off the same master.
+//
+//   vaultId    = HKDF(masterKey, info=`shade-vault-id-v1:${app}`)
+//   contentKey = HKDF(masterKey, info=`shade-vault-content-v1:${app}`)
+//   sigSeed    = HKDF(masterKey, info=`shade-vault-sig-v1:${app}`)
+
+/** 32-byte vault identifier. Opaque to the relay, like a slotId. */
+export function deriveVaultId(masterKey: Uint8Array, app: string): Uint8Array {
+  return hkdfDerive(masterKey, `shade-vault-id-v1:${app}`, 32);
+}
+
+/**
+ * AEAD key for the vault's objects and manifests.
+ *
+ * One key for the whole collection, not one per file: per-file keys would
+ * have to be stored somewhere, and that somewhere would be a manifest
+ * encrypted under a collection key anyway. Object AAD binds the content
+ * hash, so a ciphertext cannot be moved to another object's name.
+ */
+export function deriveVaultContentKey(masterKey: Uint8Array, app: string): Uint8Array {
+  return hkdfDerive(masterKey, `shade-vault-content-v1:${app}`, 32);
+}
+
+/** 32-byte Ed25519 signing seed; TOFU-pinned by the relay on first write. */
+export function deriveVaultSigningSeed(masterKey: Uint8Array, app: string): Uint8Array {
+  return hkdfDerive(masterKey, `shade-vault-sig-v1:${app}`, 32);
+}
diff --git a/packages/shade-storage-encrypted/src/crypto/row-codec.ts b/packages/shade-storage-encrypted/src/crypto/row-codec.ts
index 1979a0d..c31039f 100644
--- a/packages/shade-storage-encrypted/src/crypto/row-codec.ts
+++ b/packages/shade-storage-encrypted/src/crypto/row-codec.ts
@@ -22,8 +22,8 @@ import {
   serializeSignedPreKey, deserializeSignedPreKey,
   toBase64, fromBase64,
 } from '@shade/core';
-import { aeadOpen, aeadSeal } from './aead.js';
-import { buildAad, deriveNonce } from './kdf.js';
+import { aeadOpen, aeadSeal, randomNonce } from './aead.js';
+import { buildAad } from './kdf.js';
 import type { KeyManager } from './key-manager.js';
 
 const TEXT_ENCODER = new TextEncoder();
@@ -64,9 +64,8 @@ export async function sealString(
   plaintext: string,
 ): Promise<Uint8Array> {
   const key = km.fieldKey(table, column);
-  const nonce = deriveNonce(key, table, pk);
   const aad = buildAad(table, column, pk);
-  return aeadSeal(key, nonce, TEXT_ENCODER.encode(plaintext), aad);
+  return aeadSeal(key, randomNonce(), TEXT_ENCODER.encode(plaintext), aad);
 }
 
 /** Decrypt a blob into a string, reconstructing AAD from (table, column, pk). */
@@ -78,9 +77,8 @@ export async function openString(
   blob: Uint8Array,
 ): Promise<string> {
   const key = km.fieldKey(table, column);
-  const expectedNonce = deriveNonce(key, table, pk);
   const aad = buildAad(table, column, pk);
-  const pt = await aeadOpen(key, blob, aad, expectedNonce);
+  const pt = await aeadOpen(key, blob, aad);
   return TEXT_DECODER.decode(pt);
 }
 
@@ -93,9 +91,8 @@ export async function sealBytes(
   plaintext: Uint8Array,
 ): Promise<Uint8Array> {
   const key = km.fieldKey(table, column);
-  const nonce = deriveNonce(key, table, pk);
   const aad = buildAad(table, column, pk);
-  return aeadSeal(key, nonce, plaintext, aad);
+  return aeadSeal(key, randomNonce(), plaintext, aad);
 }
 
 /** Decrypt arbitrary bytes payload. */
@@ -107,9 +104,8 @@ export async function openBytes(
   blob: Uint8Array,
 ): Promise<Uint8Array> {
   const key = km.fieldKey(table, column);
-  const expectedNonce = deriveNonce(key, table, pk);
   const aad = buildAad(table, column, pk);
-  return aeadOpen(key, blob, aad, expectedNonce);
+  return aeadOpen(key, blob, aad);
 }
 
 // ─── Typed encoders for each StorageProvider entity ──────────────────────
diff --git a/packages/shade-storage-encrypted/src/index.ts b/packages/shade-storage-encrypted/src/index.ts
index 4d6c432..bb0ae44 100644
--- a/packages/shade-storage-encrypted/src/index.ts
+++ b/packages/shade-storage-encrypted/src/index.ts
@@ -19,12 +19,16 @@ export {
   deriveBlobSlotId,
   deriveBlobKey,
   deriveBlobSigningSeed,
+  deriveVaultId,
+  deriveVaultContentKey,
+  deriveVaultSigningSeed,
 } from './crypto/kdf.js';
 export {
   AEAD_NONCE_LEN,
   AEAD_TAG_LEN,
   aeadSeal,
   aeadOpen,
+  randomNonce,
 } from './crypto/aead.js';
 export { EncryptedSQLiteStorage } from './storage/encrypted-sqlite.js';
 export {
diff --git a/packages/shade-storage-encrypted/tests/nonce-reuse.test.ts b/packages/shade-storage-encrypted/tests/nonce-reuse.test.ts
new file mode 100644
index 0000000..b283bfe
--- /dev/null
+++ b/packages/shade-storage-encrypted/tests/nonce-reuse.test.ts
@@ -0,0 +1,141 @@
+/**
+ * Regression tests for the AES-GCM nonce-reuse fix (G0).
+ *
+ * The codec used to derive its nonce from (fieldKey, table, pk) alone. That
+ * is a pure function of row identity, so every re-seal of a mutable row —
+ * `saveSession` runs on each ratchet step — reused (key, nonce) across
+ * different plaintexts. AES-GCM forbids exactly that: it leaks the XOR of
+ * the plaintexts and the GHASH subkey, which yields tag forgery under that
+ * key. These tests fail if the derivation ever comes back.
+ */
+import { describe, test, expect } from 'bun:test';
+import { KeyManager } from '../src/crypto/key-manager.js';
+import { AEAD_NONCE_LEN, aeadSeal } from '../src/crypto/aead.js';
+import { buildAad, deriveNonce } from '../src/crypto/kdf.js';
+import {
+  COL,
+  TBL,
+  openBytes,
+  openString,
+  sealBytes,
+  sealString,
+} from '../src/crypto/row-codec.js';
+
+const TEXT = new TextEncoder();
+
+function km(): Promise<KeyManager> {
+  return KeyManager.open({ kind: 'injected', key: new Uint8Array(32).fill(0x42) });
+}
+
+const nonceOf = (blob: Uint8Array) => blob.subarray(0, AEAD_NONCE_LEN);
+const hex = (b: Uint8Array) => Array.from(b, (x) => x.toString(16).padStart(2, '0')).join('');
+
+describe('nonce uniqueness across re-saves', () => {
+  test('two seals of the same row do not share a nonce', async () => {
+    const k = await km();
+    // The real shape of the bug: same (table, column, pk), different
+    // plaintext, as a session row is re-sealed on every ratchet step.
+    const first = await sealString(k, TBL.sessions, COL.session, 'alice', '{"messageCount":1}');
+    const second = await sealString(k, TBL.sessions, COL.session, 'alice', '{"messageCount":2}');
+    expect(hex(nonceOf(first))).not.toBe(hex(nonceOf(second)));
+    k.destroy();
+  });
+
+  test('a long run of re-saves produces all-distinct nonces', async () => {
+    const k = await km();
+    const seen = new Set<string>();
+    for (let i = 0; i < 200; i++) {
+      const blob = await sealString(k, TBL.sessions, COL.session, 'alice', `state-${i}`);
+      seen.add(hex(nonceOf(blob)));
+    }
+    expect(seen.size).toBe(200);
+    k.destroy();
+  });
+
+  test('sealBytes is covered by the same rule', async () => {
+    const k = await km();
+    const a = await sealBytes(k, TBL.config, COL.config, 'cfg', TEXT.encode('one'));
+    const b = await sealBytes(k, TBL.config, COL.config, 'cfg', TEXT.encode('two'));
+    expect(hex(nonceOf(a))).not.toBe(hex(nonceOf(b)));
+    k.destroy();
+  });
+
+  test('the nonce is not the derived one', async () => {
+    const k = await km();
+    const blob = await sealString(k, TBL.sessions, COL.session, 'alice', 'payload');
+    const derived = deriveNonce(k.fieldKey(TBL.sessions, COL.session), TBL.sessions, 'alice');
+    expect(hex(nonceOf(blob))).not.toBe(hex(derived));
+    k.destroy();
+  });
+});
+
+describe('backward compatibility with deterministically-sealed blobs', () => {
+  // `aeadOpen` has always read the nonce from the blob prefix, so data
+  // written before the fix opens unchanged and needs no migration. This
+  // test reproduces an old blob by sealing with the deprecated derivation.
+  test('a blob sealed with the old derived nonce still opens', async () => {
+    const k = await km();
+    const key = k.fieldKey(TBL.sessions, COL.session);
+    const legacy = await aeadSeal(
+      key,
+      deriveNonce(key, TBL.sessions, 'alice'),
+      TEXT.encode('written before the fix'),
+      buildAad(TBL.sessions, COL.session, 'alice'),
+    );
+
+    const opened = await openString(k, TBL.sessions, COL.session, 'alice', legacy);
+    expect(opened).toBe('written before the fix');
+    k.destroy();
+  });
+
+  test('openBytes reads an old blob too', async () => {
+    const k = await km();
+    const key = k.fieldKey(TBL.config, COL.config);
+    const payload = TEXT.encode('legacy bytes');
+    const legacy = await aeadSeal(
+      key,
+      deriveNonce(key, TBL.config, 'cfg'),
+      payload,
+      buildAad(TBL.config, COL.config, 'cfg'),
+    );
+
+    expect(await openBytes(k, TBL.config, COL.config, 'cfg', legacy)).toEqual(payload);
+    k.destroy();
+  });
+
+  test('new and old blobs are both readable under one key', async () => {
+    const k = await km();
+    const key = k.fieldKey(TBL.sessions, COL.session);
+    const legacy = await aeadSeal(
+      key,
+      deriveNonce(key, TBL.sessions, 'bob'),
+      TEXT.encode('old'),
+      buildAad(TBL.sessions, COL.session, 'bob'),
+    );
+    const fresh = await sealString(k, TBL.sessions, COL.session, 'bob', 'new');
+
+    expect(await openString(k, TBL.sessions, COL.session, 'bob', legacy)).toBe('old');
+    expect(await openString(k, TBL.sessions, COL.session, 'bob', fresh)).toBe('new');
+    k.destroy();
+  });
+});
+
+describe('tamper detection survives the switch', () => {
+  // The dropped `expectedNonce` check was the stated reason for the
+  // deterministic nonce. It detected nothing the AEAD tag misses.
+  test('a flipped nonce byte is still rejected', async () => {
+    const k = await km();
+    const blob = await sealString(k, TBL.sessions, COL.session, 'alice', 'payload');
+    const tampered = new Uint8Array(blob);
+    tampered[0]! ^= 0x01;
+    await expect(openString(k, TBL.sessions, COL.session, 'alice', tampered)).rejects.toThrow();
+    k.destroy();
+  });
+
+  test('a blob moved to another row is still rejected (AAD binding)', async () => {
+    const k = await km();
+    const blob = await sealString(k, TBL.sessions, COL.session, 'alice', 'alice-secret');
+    await expect(openString(k, TBL.sessions, COL.session, 'bob', blob)).rejects.toThrow();
+    k.destroy();
+  });
+});