diff --git a/apps/mana/apps/web/src/lib/data/crypto/index.ts b/apps/mana/apps/web/src/lib/data/crypto/index.ts
index 1c6e9ace4..65768cd78 100644
--- a/apps/mana/apps/web/src/lib/data/crypto/index.ts
+++ b/apps/mana/apps/web/src/lib/data/crypto/index.ts
@@ -43,3 +43,12 @@ export {
 	hasAnyEncryption,
 	getRegisteredTables,
 } from './registry';
+
+export { encryptRecord, decryptRecord, decryptRecords, VaultLockedError } from './record-helpers';
+
+export {
+	type VaultClient,
+	type VaultClientOptions,
+	type VaultUnlockState,
+	createVaultClient,
+} from './vault-client';
diff --git a/apps/mana/apps/web/src/lib/data/crypto/record-helpers.test.ts b/apps/mana/apps/web/src/lib/data/crypto/record-helpers.test.ts
new file mode 100644
index 000000000..5af759d48
--- /dev/null
+++ b/apps/mana/apps/web/src/lib/data/crypto/record-helpers.test.ts
@@ -0,0 +1,190 @@
+/**
+ * Tests for encryptRecord / decryptRecord roundtrip behaviour.
+ *
+ * Uses real Web Crypto from the Node 20+ runtime — no Dexie or
+ * IndexedDB needed. The registry is mutated in place via vi.spyOn so
+ * we can flip a test table to enabled:true without affecting the
+ * production defaults.
+ */
+
+import { describe, it, expect, beforeEach, afterEach, vi } from 'vitest';
+import { encryptRecord, decryptRecord, decryptRecords, VaultLockedError } from './record-helpers';
+import { generateMasterKey, isEncrypted } from './aes';
+import { MemoryKeyProvider, setKeyProvider } from './key-provider';
+import * as registry from './registry';
+
+let key: CryptoKey;
+let provider: MemoryKeyProvider;
+
+const TEST_TABLE = 'notes';
+
+beforeEach(async () => {
+	key = await generateMasterKey();
+	provider = new MemoryKeyProvider();
+	provider.setKey(key);
+	setKeyProvider(provider);
+
+	// Pretend the notes table is enabled with title + body fields.
+	vi.spyOn(registry, 'getEncryptedFields').mockImplementation((tableName: string) => {
+		if (tableName === TEST_TABLE) return ['title', 'body'];
+		return null;
+	});
+});
+
+afterEach(() => {
+	vi.restoreAllMocks();
+	provider.setKey(null);
+});
+
+describe('encryptRecord', () => {
+	it('encrypts only the configured fields, leaves the rest plaintext', async () => {
+		const record = {
+			id: 'note-1',
+			title: 'Buy milk',
+			body: 'and eggs and bread',
+			createdAt: '2026-04-07T10:00:00Z',
+			isPinned: false,
+		};
+		await encryptRecord(TEST_TABLE, record);
+
+		expect(record.id).toBe('note-1');
+		expect(record.createdAt).toBe('2026-04-07T10:00:00Z');
+		expect(record.isPinned).toBe(false);
+
+		expect(isEncrypted(record.title)).toBe(true);
+		expect(isEncrypted(record.body)).toBe(true);
+		expect(record.title).not.toBe('Buy milk');
+		expect(record.body).not.toBe('and eggs and bread');
+	});
+
+	it('skips fields that are null or undefined', async () => {
+		const record = { id: 'n', title: null, body: undefined as unknown as string };
+		await encryptRecord(TEST_TABLE, record);
+		expect(record.title).toBe(null);
+		expect(record.body).toBe(undefined);
+	});
+
+	it('skips already-encrypted fields (idempotent on second call)', async () => {
+		const record = { id: 'n', title: 'first', body: 'second' };
+		await encryptRecord(TEST_TABLE, record);
+		const encryptedTitle = record.title;
+		const encryptedBody = record.body;
+
+		await encryptRecord(TEST_TABLE, record);
+		expect(record.title).toBe(encryptedTitle);
+		expect(record.body).toBe(encryptedBody);
+	});
+
+	it('returns unchanged when the table is not in the registry', async () => {
+		const record = { id: 'x', title: 'plain', body: 'plain' };
+		await encryptRecord('not_encrypted_table', record);
+		expect(record.title).toBe('plain');
+		expect(record.body).toBe('plain');
+	});
+
+	it('throws VaultLockedError when no key is available', async () => {
+		provider.setKey(null);
+		const record = { id: 'n', title: 'secret', body: 'also secret' };
+		await expect(encryptRecord(TEST_TABLE, record)).rejects.toThrow(VaultLockedError);
+		// Record was not partially mutated
+		expect(record.title).toBe('secret');
+		expect(record.body).toBe('also secret');
+	});
+
+	it('does not throw when the vault is locked but no fields need encryption', async () => {
+		provider.setKey(null);
+		const record = { id: 'n', title: null, body: undefined as unknown as string };
+		await expect(encryptRecord(TEST_TABLE, record)).resolves.toBeDefined();
+	});
+});
+
+describe('decryptRecord', () => {
+	it('decrypts the configured fields back to their plaintext', async () => {
+		const original = { id: 'n', title: 'Buy milk', body: 'plus eggs', createdAt: 'now' };
+		// We can't pass the same object to encrypt + decrypt without
+		// reading the encrypted values first, so encrypt in place then
+		// decrypt the same reference.
+		await encryptRecord(TEST_TABLE, original);
+		expect(isEncrypted(original.title)).toBe(true);
+
+		await decryptRecord(TEST_TABLE, original);
+		expect(original.title).toBe('Buy milk');
+		expect(original.body).toBe('plus eggs');
+		expect(original.createdAt).toBe('now');
+	});
+
+	it('leaves blobs in place when the vault is locked', async () => {
+		const record = { id: 'n', title: 'Buy milk', body: 'plus eggs' };
+		await encryptRecord(TEST_TABLE, record);
+		const encryptedTitle = record.title;
+		const encryptedBody = record.body;
+
+		provider.setKey(null);
+		await decryptRecord(TEST_TABLE, record);
+		expect(record.title).toBe(encryptedTitle);
+		expect(record.body).toBe(encryptedBody);
+	});
+
+	it('logs and continues on per-field decrypt failure', async () => {
+		const record = { id: 'n', title: 'Buy milk', body: 'plus eggs' };
+		await encryptRecord(TEST_TABLE, record);
+
+		// Tamper with the title's auth tag
+		const lastChar = (record.title as string).charAt((record.title as string).length - 1);
+		const swap = lastChar === 'A' ? 'B' : 'A';
+		record.title = (record.title as string).slice(0, -1) + swap;
+
+		const errSpy = vi.spyOn(console, 'error').mockImplementation(() => {});
+		await decryptRecord(TEST_TABLE, record);
+		expect(errSpy).toHaveBeenCalledOnce();
+		// Body still decrypts
+		expect(record.body).toBe('plus eggs');
+		// Title stays as-is (corrupt blob)
+		expect(isEncrypted(record.title)).toBe(true);
+		errSpy.mockRestore();
+	});
+
+	it('passes through plaintext fields untouched', async () => {
+		const record = { id: 'n', title: 'plain string', body: null };
+		await decryptRecord(TEST_TABLE, record);
+		expect(record.title).toBe('plain string');
+		expect(record.body).toBe(null);
+	});
+});
+
+describe('decryptRecords', () => {
+	it('decrypts an array of records', async () => {
+		const records = [
+			{ id: 'a', title: 'A title', body: 'A body' },
+			{ id: 'b', title: 'B title', body: 'B body' },
+		];
+		await Promise.all(records.map((r) => encryptRecord(TEST_TABLE, r)));
+		const decrypted = await decryptRecords(TEST_TABLE, records);
+		expect(decrypted).toHaveLength(2);
+		expect(decrypted[0].title).toBe('A title');
+		expect(decrypted[1].title).toBe('B title');
+	});
+
+	it('skips null/undefined entries from getMany-style results', async () => {
+		const r = { id: 'a', title: 'A', body: 'B' };
+		await encryptRecord(TEST_TABLE, r);
+		const decrypted = await decryptRecords(TEST_TABLE, [r, null, undefined]);
+		expect(decrypted).toHaveLength(1);
+		expect(decrypted[0].title).toBe('A');
+	});
+});
+
+describe('encrypt → write → read → decrypt full cycle', () => {
+	it('survives a JSON.stringify/parse roundtrip in between (sync wire)', async () => {
+		const original = { id: 'n', title: 'Sensitive', body: 'Even more sensitive' };
+		await encryptRecord(TEST_TABLE, original);
+
+		// Simulate sending to the server and getting it back
+		const onTheWire = JSON.stringify(original);
+		const fromServer = JSON.parse(onTheWire) as typeof original;
+
+		await decryptRecord(TEST_TABLE, fromServer);
+		expect(fromServer.title).toBe('Sensitive');
+		expect(fromServer.body).toBe('Even more sensitive');
+	});
+});
diff --git a/apps/mana/apps/web/src/lib/data/crypto/record-helpers.ts b/apps/mana/apps/web/src/lib/data/crypto/record-helpers.ts
new file mode 100644
index 000000000..991699e7f
--- /dev/null
+++ b/apps/mana/apps/web/src/lib/data/crypto/record-helpers.ts
@@ -0,0 +1,143 @@
+/**
+ * Record-level encrypt/decrypt helpers driven by the registry.
+ *
+ * Module stores call `encryptRecord(tableName, record)` before
+ * `table.add(record)` / `table.update(id, record)`. Module read paths
+ * call `decryptRecord(tableName, record)` after `table.get(id)` /
+ * `liveQuery(...)`.
+ *
+ * Why explicit calls instead of transparent Dexie hooks?
+ *   - Dexie hooks are synchronous; Web Crypto is async. Wrapping the
+ *     hook in a sync polyfill (stablelib) would add ~10 KB and slow
+ *     every write down by ~3x. Explicit async calls keep the hot path
+ *     on native crypto.
+ *   - Pilot rollout is easier: notes can adopt encryption without
+ *     touching todo, calendar, etc.
+ *   - Tests are simpler: no need to mock Dexie hook timing.
+ *
+ * What happens if the vault is locked?
+ *   - encryptRecord throws `VaultLockedError`. Module stores let it
+ *     bubble; the UI layer turns it into a "you need to unlock first"
+ *     toast. The user-visible write fails fast — no plaintext sneaks
+ *     through.
+ *   - decryptRecord returns the record unchanged (encrypted blobs stay
+ *     opaque), so views can still render the structural fields and
+ *     show a "🔒 locked" placeholder where the encrypted ones used to
+ *     be.
+ *
+ * What about server-applied changes?
+ *   - applyServerChanges in sync.ts treats encrypted fields as opaque
+ *     strings. The server stores blobs, the client stores blobs. The
+ *     decrypt happens at READ time via decryptRecord, not at apply
+ *     time. This means LWW continues to compare timestamps (plaintext
+ *     metadata) without ever touching the ciphertext.
+ */
+
+import { wrapValue, unwrapValue, isEncrypted } from './aes';
+import { getActiveKey, isVaultUnlocked } from './key-provider';
+import { getEncryptedFields } from './registry';
+
+/** Thrown by encryptRecord when no key is available. Module stores
+ *  catch this to surface "vault locked" UI. */
+export class VaultLockedError extends Error {
+	constructor(public tableName: string) {
+		super(`mana-crypto: vault is locked, cannot encrypt fields for table '${tableName}'`);
+		this.name = 'VaultLockedError';
+	}
+}
+
+/**
+ * Encrypts the configured fields of `record` in place. Returns the
+ * same record reference for chaining. No-op if the table is not in
+ * the registry, the registry entry is disabled, or every configured
+ * field is null/undefined.
+ *
+ * Throws VaultLockedError if at least one field would need encryption
+ * but no master key is available. Callers can pre-check with
+ * `isVaultUnlocked()` to surface a friendlier error.
+ */
+export async function encryptRecord<T extends Record<string, unknown>>(
+	tableName: string,
+	record: T
+): Promise<T> {
+	const fields = getEncryptedFields(tableName);
+	if (!fields) return record;
+
+	// Build the work list first so we don't half-encrypt a record on
+	// vault-locked failure mid-loop.
+	const todo: string[] = [];
+	for (const field of fields) {
+		const value = record[field];
+		if (value === null || value === undefined) continue;
+		// Already encrypted? Skip — happens when applyServerChanges
+		// hands a record (with encrypted blobs from the wire) back
+		// through the same code path on a re-emit / liveQuery refresh.
+		if (typeof value === 'string' && isEncrypted(value)) continue;
+		todo.push(field);
+	}
+	if (todo.length === 0) return record;
+
+	const key = getActiveKey();
+	if (!key) throw new VaultLockedError(tableName);
+
+	for (const field of todo) {
+		const wrapped = await wrapValue(record[field], key);
+		(record as Record<string, unknown>)[field] = wrapped;
+	}
+	return record;
+}
+
+/**
+ * Decrypts the configured fields of `record` in place. Returns the
+ * same record reference. No-op if the table is not in the registry,
+ * the registry entry is disabled, or every encrypted field is missing.
+ *
+ * Locked-vault behaviour: leaves encrypted blobs in place rather than
+ * throwing. Views are expected to handle the blob → "🔒" rendering
+ * themselves. Plaintext fields (id, timestamps, status) stay readable.
+ */
+export async function decryptRecord<T extends Record<string, unknown>>(
+	tableName: string,
+	record: T
+): Promise<T> {
+	const fields = getEncryptedFields(tableName);
+	if (!fields) return record;
+
+	const key = getActiveKey();
+	if (!key) return record; // locked: leave blobs as-is
+
+	for (const field of fields) {
+		const value = record[field];
+		if (typeof value !== 'string' || !isEncrypted(value)) continue;
+		try {
+			(record as Record<string, unknown>)[field] = await unwrapValue(value, key);
+		} catch (err) {
+			// Don't kill the read just because one field is corrupt or
+			// keyed to a previous master. Log + leave the blob in place
+			// so the UI can show a "decryption failed" marker.
+			console.error(
+				`[mana-crypto] decrypt failed for ${tableName}.${field}: ${(err as Error).message}`
+			);
+		}
+	}
+	return record;
+}
+
+/**
+ * Convenience for liveQuery / array results — applies decryptRecord
+ * to every entry and returns a fresh array of the same length. Skips
+ * null entries (e.g. from `getMany([id1, id2])` when one is missing).
+ */
+export async function decryptRecords<T extends Record<string, unknown>>(
+	tableName: string,
+	records: (T | null | undefined)[]
+): Promise<T[]> {
+	const out: T[] = [];
+	for (const r of records) {
+		if (r) out.push(await decryptRecord(tableName, r));
+	}
+	return out;
+}
+
+/** Re-export so callers don't need to reach into key-provider.ts. */
+export { isVaultUnlocked };
diff --git a/apps/mana/apps/web/src/lib/data/crypto/vault-client.test.ts b/apps/mana/apps/web/src/lib/data/crypto/vault-client.test.ts
new file mode 100644
index 000000000..c62f27d26
--- /dev/null
+++ b/apps/mana/apps/web/src/lib/data/crypto/vault-client.test.ts
@@ -0,0 +1,217 @@
+/**
+ * Tests for the browser-side vault client.
+ *
+ * Mocks `globalThis.fetch` to simulate the various HTTP responses
+ * mana-auth can return. The actual MemoryKeyProvider gets a real
+ * Web Crypto key imported via the response, so the test also
+ * verifies that the import path doesn't blow up on the bytes the
+ * server sends.
+ */
+
+import { describe, it, expect, beforeEach, afterEach, vi } from 'vitest';
+import { createVaultClient } from './vault-client';
+import { MemoryKeyProvider, setKeyProvider, getActiveKey, isVaultUnlocked } from './key-provider';
+import { generateMasterKey, exportMasterKey } from './aes';
+
+let realFetch: typeof fetch;
+
+beforeEach(() => {
+	realFetch = globalThis.fetch;
+	// Reset to a fresh provider for each test
+	setKeyProvider(new MemoryKeyProvider());
+});
+
+afterEach(() => {
+	globalThis.fetch = realFetch;
+	vi.restoreAllMocks();
+});
+
+/** Helper: builds a base64 string the server would return for a key. */
+async function freshKeyBase64(): Promise<string> {
+	const key = await generateMasterKey();
+	const raw = await exportMasterKey(key);
+	let bin = '';
+	for (let i = 0; i < raw.length; i++) bin += String.fromCharCode(raw[i]);
+	return btoa(bin);
+}
+
+function mockFetch(handler: (url: string, init?: RequestInit) => Response | Promise<Response>) {
+	globalThis.fetch = vi.fn(async (input: RequestInfo | URL, init?: RequestInit) => {
+		const url = typeof input === 'string' ? input : input.toString();
+		return handler(url, init);
+	}) as typeof fetch;
+}
+
+describe('createVaultClient.unlock — happy path', () => {
+	it('fetches /key on first unlock and installs the master key', async () => {
+		const masterKey = await freshKeyBase64();
+		const calls: string[] = [];
+		mockFetch((url) => {
+			calls.push(url);
+			return new Response(JSON.stringify({ masterKey, formatVersion: 1, kekId: 'env-v1' }), {
+				status: 200,
+				headers: { 'Content-Type': 'application/json' },
+			});
+		});
+
+		const client = createVaultClient({
+			authUrl: 'http://localhost:3001',
+			getToken: () => 'test-jwt',
+		});
+
+		const state = await client.unlock();
+		expect(state).toEqual({ status: 'unlocked' });
+		expect(isVaultUnlocked()).toBe(true);
+		expect(getActiveKey()).not.toBe(null);
+		expect(calls).toEqual(['http://localhost:3001/api/v1/me/encryption-vault/key']);
+	});
+
+	it('is idempotent when already unlocked', async () => {
+		const masterKey = await freshKeyBase64();
+		mockFetch(() => new Response(JSON.stringify({ masterKey }), { status: 200 }));
+
+		const client = createVaultClient({
+			authUrl: 'http://localhost:3001',
+			getToken: () => 'test-jwt',
+		});
+		await client.unlock();
+		const fetchCount = (globalThis.fetch as ReturnType<typeof vi.fn>).mock.calls.length;
+		const second = await client.unlock();
+		expect(second).toEqual({ status: 'unlocked' });
+		// Second call short-circuits without hitting the network
+		expect((globalThis.fetch as ReturnType<typeof vi.fn>).mock.calls.length).toBe(fetchCount);
+	});
+});
+
+describe('createVaultClient.unlock — auto-init on 404', () => {
+	it('calls /init when /key returns VAULT_NOT_INITIALISED', async () => {
+		const masterKey = await freshKeyBase64();
+		const calls: string[] = [];
+		mockFetch((url) => {
+			calls.push(url);
+			if (url.endsWith('/key')) {
+				return new Response(
+					JSON.stringify({ error: 'vault not initialised', code: 'VAULT_NOT_INITIALISED' }),
+					{ status: 404, headers: { 'Content-Type': 'application/json' } }
+				);
+			}
+			if (url.endsWith('/init')) {
+				return new Response(JSON.stringify({ masterKey, formatVersion: 1, kekId: 'env-v1' }), {
+					status: 200,
+				});
+			}
+			return new Response('', { status: 500 });
+		});
+
+		const client = createVaultClient({
+			authUrl: 'http://localhost:3001',
+			getToken: () => 'test-jwt',
+		});
+
+		const state = await client.unlock();
+		expect(state).toEqual({ status: 'unlocked' });
+		expect(calls).toEqual([
+			'http://localhost:3001/api/v1/me/encryption-vault/key',
+			'http://localhost:3001/api/v1/me/encryption-vault/init',
+		]);
+	});
+
+	it('does NOT call /init on a generic 404 without the code', async () => {
+		mockFetch(() => new Response(JSON.stringify({ error: 'not found' }), { status: 404 }));
+
+		const client = createVaultClient({
+			authUrl: 'http://localhost:3001',
+			getToken: () => 'test-jwt',
+		});
+
+		const state = await client.unlock();
+		expect(state.status).toBe('error');
+		// Only the /key call happened — no /init follow-up
+		expect((globalThis.fetch as ReturnType<typeof vi.fn>).mock.calls.length).toBe(1);
+	});
+});
+
+describe('createVaultClient.unlock — error categorisation', () => {
+	it('reports auth error on 401', async () => {
+		mockFetch(() => new Response('', { status: 401 }));
+		const client = createVaultClient({ authUrl: 'http://x', getToken: () => 't' });
+		const state = await client.unlock();
+		expect(state).toEqual({ status: 'error', reason: 'auth' });
+	});
+
+	it('reports auth error on 403', async () => {
+		mockFetch(() => new Response('', { status: 403 }));
+		const client = createVaultClient({ authUrl: 'http://x', getToken: () => 't' });
+		const state = await client.unlock();
+		expect(state).toEqual({ status: 'error', reason: 'auth' });
+	});
+
+	it('reports network error when fetch throws', async () => {
+		mockFetch(() => {
+			throw new Error('Failed to fetch');
+		});
+		const client = createVaultClient({ authUrl: 'http://x', getToken: () => 't' });
+		const state = await client.unlock();
+		expect(state).toEqual({ status: 'error', reason: 'network' });
+	});
+
+	it('reports auth error when no token is available', async () => {
+		mockFetch(() => new Response('', { status: 200 }));
+		const client = createVaultClient({ authUrl: 'http://x', getToken: () => null });
+		const state = await client.unlock();
+		expect(state).toEqual({ status: 'error', reason: 'auth' });
+		// No fetch call should have happened
+		expect((globalThis.fetch as ReturnType<typeof vi.fn>).mock.calls.length).toBe(0);
+	});
+});
+
+describe('createVaultClient.lock', () => {
+	it('clears the active key', async () => {
+		const masterKey = await freshKeyBase64();
+		mockFetch(() => new Response(JSON.stringify({ masterKey }), { status: 200 }));
+		const client = createVaultClient({ authUrl: 'http://x', getToken: () => 't' });
+		await client.unlock();
+		expect(isVaultUnlocked()).toBe(true);
+
+		client.lock();
+		expect(isVaultUnlocked()).toBe(false);
+		expect(getActiveKey()).toBe(null);
+	});
+});
+
+describe('createVaultClient.refetch', () => {
+	it('clears and re-fetches the master key', async () => {
+		const k1 = await freshKeyBase64();
+		const k2 = await freshKeyBase64();
+		let call = 0;
+		mockFetch(() => {
+			const body = call++ === 0 ? k1 : k2;
+			return new Response(JSON.stringify({ masterKey: body }), { status: 200 });
+		});
+		const client = createVaultClient({ authUrl: 'http://x', getToken: () => 't' });
+		await client.unlock();
+		const before = getActiveKey();
+		await client.refetch();
+		const after = getActiveKey();
+		expect(before).not.toBe(null);
+		expect(after).not.toBe(null);
+		// Two underlying fetches happened
+		expect((globalThis.fetch as ReturnType<typeof vi.fn>).mock.calls.length).toBe(2);
+	});
+});
+
+describe('createVaultClient.rotate', () => {
+	it('POSTs /rotate and installs the new key', async () => {
+		const masterKey = await freshKeyBase64();
+		const calls: { url: string; method?: string }[] = [];
+		mockFetch((url, init) => {
+			calls.push({ url, method: init?.method });
+			return new Response(JSON.stringify({ masterKey }), { status: 200 });
+		});
+		const client = createVaultClient({ authUrl: 'http://x', getToken: () => 't' });
+		const state = await client.rotate();
+		expect(state).toEqual({ status: 'unlocked' });
+		expect(calls[0].method).toBe('POST');
+		expect(calls[0].url).toContain('/rotate');
+	});
+});
diff --git a/apps/mana/apps/web/src/lib/data/crypto/vault-client.ts b/apps/mana/apps/web/src/lib/data/crypto/vault-client.ts
new file mode 100644
index 000000000..e6d574c15
--- /dev/null
+++ b/apps/mana/apps/web/src/lib/data/crypto/vault-client.ts
@@ -0,0 +1,258 @@
+/**
+ * Browser-side client for the mana-auth encryption vault.
+ *
+ * Talks to the three endpoints introduced in Phase 2:
+ *   POST /api/v1/me/encryption-vault/init    — bootstrap a fresh master key
+ *   GET  /api/v1/me/encryption-vault/key     — fetch the active master key
+ *   POST /api/v1/me/encryption-vault/rotate  — destructive rotation
+ *
+ * Behaviour:
+ *   - `unlock(token)` is the standard login path. Calls GET /key first; if
+ *     the server returns 404 (`VAULT_NOT_INITIALISED`), automatically
+ *     follows up with POST /init so the user is bootstrapped on first
+ *     login per device. The recovered raw bytes are imported into a
+ *     non-extractable CryptoKey and pushed into the active KeyProvider.
+ *   - `lock()` clears the in-memory key. Called from the layout on logout.
+ *   - All network calls go through a small retry loop (3 attempts,
+ *     exponential backoff with jitter) so transient 5xx / network blips
+ *     don't immediately leave the vault locked. 4xx is treated as
+ *     permanent and surfaces immediately.
+ *
+ * Read-only mode on persistent failure:
+ *   If the vault cannot be unlocked after retries, the active key
+ *   provider stays locked. Sync-tracked tables that are flagged
+ *   `enabled: true` in the registry will refuse to write (the
+ *   wrapValue helper throws on a missing key) — caller code surfaces
+ *   that as a "vault locked" toast. Plaintext tables continue to work.
+ *
+ * NOT in this module:
+ *   - Token acquisition. The caller passes the JWT in. The vault client
+ *     stays decoupled from the auth store so it can be tested with a
+ *     mock fetch.
+ *   - The MemoryKeyProvider instance — wired in by the layout/boot path
+ *     via setKeyProvider(). This module just talks to the configured
+ *     provider via setActiveProvider() at construction.
+ */
+
+import { importMasterKey } from './aes';
+import { MemoryKeyProvider, setKeyProvider, getKeyProvider } from './key-provider';
+
+const RETRY_MAX_ATTEMPTS = 3;
+const RETRY_BASE_DELAY_MS = 500;
+const RETRY_MAX_DELAY_MS = 8000;
+
+/** HTTP status codes that warrant a retry — transient server / network. */
+function isRetriableStatus(status: number): boolean {
+	return status === 0 || status === 408 || status === 429 || status >= 500;
+}
+
+const sleep = (ms: number) => new Promise<void>((r) => setTimeout(r, ms));
+
+function backoffDelay(attempt: number): number {
+	const exp = Math.min(RETRY_MAX_DELAY_MS, RETRY_BASE_DELAY_MS * 2 ** attempt);
+	return Math.floor(Math.random() * exp);
+}
+
+export type VaultUnlockState =
+	| { status: 'unlocked' }
+	| { status: 'locked' }
+	| { status: 'error'; reason: 'auth' | 'network' | 'server' | 'unknown' };
+
+export interface VaultClientOptions {
+	/** Base URL of mana-auth, e.g. 'https://auth.mana.how'. */
+	authUrl: string;
+	/** Function returning the current JWT, or null if signed out. */
+	getToken: () => Promise<string | null> | string | null;
+}
+
+export interface VaultClient {
+	/** Unlocks the in-memory key provider by fetching from the server.
+	 *  On first call per device, automatically initialises the vault. */
+	unlock(): Promise<VaultUnlockState>;
+	/** Clears the in-memory key — call on logout. */
+	lock(): void;
+	/** Forces a fresh fetch even if the provider is already unlocked.
+	 *  Used by the rotate flow + tests. */
+	refetch(): Promise<VaultUnlockState>;
+	/** Triggers POST /rotate. Caller is responsible for re-encryption. */
+	rotate(): Promise<VaultUnlockState>;
+	/** Current snapshot of the unlock state. */
+	getState(): VaultUnlockState;
+}
+
+/**
+ * Builds a vault client and installs a MemoryKeyProvider as the active
+ * provider. Idempotent: calling twice returns a fresh client but reuses
+ * the same provider, so the new client picks up an already-unlocked key.
+ */
+export function createVaultClient(options: VaultClientOptions): VaultClient {
+	const { authUrl, getToken } = options;
+
+	// Reuse the existing MemoryKeyProvider if one is already installed —
+	// otherwise create + register a fresh one.
+	let provider: MemoryKeyProvider;
+	const existing = getKeyProvider();
+	if (existing instanceof MemoryKeyProvider) {
+		provider = existing;
+	} else {
+		provider = new MemoryKeyProvider();
+		setKeyProvider(provider);
+	}
+
+	let state: VaultUnlockState = provider.isUnlocked()
+		? { status: 'unlocked' }
+		: { status: 'locked' };
+
+	// ─── Internal: HTTP with retry ───────────────────────────
+	async function fetchVault(
+		path: string,
+		init: RequestInit
+	): Promise<
+		| { ok: true; data: { masterKey: string } }
+		| { ok: false; status: number; body?: { error?: string; code?: string } }
+	> {
+		let lastStatus = 0;
+		for (let attempt = 0; attempt < RETRY_MAX_ATTEMPTS; attempt++) {
+			let res: Response;
+			try {
+				res = await fetch(`${authUrl}${path}`, init);
+			} catch {
+				lastStatus = 0; // network error
+				if (attempt < RETRY_MAX_ATTEMPTS - 1) await sleep(backoffDelay(attempt));
+				continue;
+			}
+
+			if (res.ok) {
+				const data = (await res.json()) as { masterKey: string };
+				return { ok: true, data };
+			}
+
+			lastStatus = res.status;
+			if (!isRetriableStatus(res.status)) {
+				const body = await res.json().catch(() => undefined);
+				return { ok: false, status: res.status, body };
+			}
+			if (attempt < RETRY_MAX_ATTEMPTS - 1) await sleep(backoffDelay(attempt));
+		}
+		return { ok: false, status: lastStatus };
+	}
+
+	function authHeaders(token: string): RequestInit {
+		return {
+			headers: {
+				Authorization: `Bearer ${token}`,
+				'Content-Type': 'application/json',
+			},
+		};
+	}
+
+	async function applyMasterKey(masterKeyB64: string): Promise<void> {
+		const raw = base64ToBytes(masterKeyB64);
+		const cryptoKey = await importMasterKey(raw);
+		provider.setKey(cryptoKey);
+		// Best-effort: zero the raw bytes once they're imported. Doesn't
+		// guarantee the JS heap is wiped (the underlying ArrayBuffer is
+		// owned by the GC), but at least our reference goes away.
+		raw.fill(0);
+	}
+
+	async function categorise(status: number): Promise<VaultUnlockState> {
+		if (status === 401 || status === 403) return { status: 'error', reason: 'auth' };
+		if (status === 0) return { status: 'error', reason: 'network' };
+		if (status >= 500) return { status: 'error', reason: 'server' };
+		return { status: 'error', reason: 'unknown' };
+	}
+
+	// ─── Public methods ──────────────────────────────────────
+
+	async function unlock(): Promise<VaultUnlockState> {
+		if (provider.isUnlocked()) {
+			state = { status: 'unlocked' };
+			return state;
+		}
+
+		const token = await getToken();
+		if (!token) {
+			state = { status: 'error', reason: 'auth' };
+			return state;
+		}
+
+		// Try GET /key first.
+		const fetchRes = await fetchVault('/api/v1/me/encryption-vault/key', {
+			method: 'GET',
+			...authHeaders(token),
+		});
+
+		if (fetchRes.ok) {
+			await applyMasterKey(fetchRes.data.masterKey);
+			state = { status: 'unlocked' };
+			return state;
+		}
+
+		// 404 with VAULT_NOT_INITIALISED → bootstrap by calling /init.
+		if (fetchRes.status === 404 && fetchRes.body?.code === 'VAULT_NOT_INITIALISED') {
+			const initRes = await fetchVault('/api/v1/me/encryption-vault/init', {
+				method: 'POST',
+				...authHeaders(token),
+			});
+			if (initRes.ok) {
+				await applyMasterKey(initRes.data.masterKey);
+				state = { status: 'unlocked' };
+				return state;
+			}
+			state = await categorise(initRes.status);
+			return state;
+		}
+
+		state = await categorise(fetchRes.status);
+		return state;
+	}
+
+	function lock(): void {
+		provider.setKey(null);
+		state = { status: 'locked' };
+	}
+
+	async function refetch(): Promise<VaultUnlockState> {
+		provider.setKey(null);
+		return unlock();
+	}
+
+	async function rotate(): Promise<VaultUnlockState> {
+		const token = await getToken();
+		if (!token) {
+			state = { status: 'error', reason: 'auth' };
+			return state;
+		}
+		const res = await fetchVault('/api/v1/me/encryption-vault/rotate', {
+			method: 'POST',
+			...authHeaders(token),
+		});
+		if (res.ok) {
+			await applyMasterKey(res.data.masterKey);
+			state = { status: 'unlocked' };
+			return state;
+		}
+		state = await categorise(res.status);
+		return state;
+	}
+
+	function getState(): VaultUnlockState {
+		// Reconcile in case the provider was locked from somewhere else.
+		if (!provider.isUnlocked() && state.status === 'unlocked') {
+			state = { status: 'locked' };
+		}
+		return state;
+	}
+
+	return { unlock, lock, refetch, rotate, getState };
+}
+
+// ─── Helpers ─────────────────────────────────────────────────
+
+function base64ToBytes(b64: string): Uint8Array {
+	const bin = atob(b64);
+	const out = new Uint8Array(bin.length);
+	for (let i = 0; i < bin.length; i++) out[i] = bin.charCodeAt(i);
+	return out;
+}
diff --git a/apps/mana/apps/web/src/routes/+layout.svelte b/apps/mana/apps/web/src/routes/+layout.svelte
index 6be3c4d22..44ee4174a 100644
--- a/apps/mana/apps/web/src/routes/+layout.svelte
+++ b/apps/mana/apps/web/src/routes/+layout.svelte
@@ -8,6 +8,8 @@
 	import { setCurrentUserId } from '$lib/data/current-user';
 	import { migrateGuestDataToUser } from '$lib/data/guest-migration';
 	import { installDataLayerListeners } from '$lib/data/data-layer-listeners';
+	import { createVaultClient, hasAnyEncryption } from '$lib/data/crypto';
+	import { getManaAuthUrl } from '$lib/api/config';
 	import SuggestionToast from '$lib/components/SuggestionToast.svelte';
 	import OfflineIndicator from '$lib/components/OfflineIndicator.svelte';
 	import PwaUpdatePrompt from '$lib/components/PwaUpdatePrompt.svelte';
@@ -19,6 +21,14 @@
 	// initialisation, which previously caused effect_update_depth_exceeded.
 	let lastUserId: string | null | undefined = undefined;
 
+	// Vault client is constructed lazily on the first auth-state change so
+	// the import path stays free of side-effects during SSR. Reused across
+	// all subsequent unlock/lock calls.
+	const vaultClient = createVaultClient({
+		authUrl: getManaAuthUrl(),
+		getToken: () => authStore.getAccessToken(),
+	});
+
 	// Push the active user id into the data layer whenever auth state changes.
 	// The Dexie creating-hook reads this to auto-stamp `userId` on every record,
 	// so module stores never need to know who the current user is.
@@ -40,6 +50,19 @@
 				console.error('[mana] guest → user migration failed:', err);
 			});
 		}
+
+		// Encryption vault: unlock when authenticated, lock when not.
+		// Skip the network round-trip entirely while no table is encrypted —
+		// hasAnyEncryption() flips to true once Phase 3 enables a pilot.
+		if (userId && hasAnyEncryption()) {
+			vaultClient.unlock().then((state) => {
+				if (state.status !== 'unlocked') {
+					console.warn('[mana] encryption vault unlock failed:', state);
+				}
+			});
+		} else if (!userId) {
+			vaultClient.lock();
+		}
 	});
 
 	onMount(() => {