diff --git a/apps/desktop/src/components/AppShell.tsx b/apps/desktop/src/components/AppShell.tsx
index 06b0d9c..97ec6fc 100644
--- a/apps/desktop/src/components/AppShell.tsx
+++ b/apps/desktop/src/components/AppShell.tsx
@@ -1,4 +1,3 @@
-import { loadDevicePrivateKey } from '@chat-app/shared/auth';
 import { useEffect } from 'react';
 import { Outlet } from 'react-router-dom';
 
@@ -6,7 +5,7 @@ import { useAuth } from '../context/AuthContext';
 import { startConversationKeySync } from '../lib/conversationKeySync';
 import { startDeviceApprovalListener } from '../lib/deviceApproval';
 import { ensureNotificationPermission } from '../lib/osNotify';
-import { devLocalSecretStore } from '../lib/secretStore';
+import { cachedUserKey } from '../lib/userIdentity';
 import { BackupPromptBanner } from './BackupPromptBanner';
 import { CallUI } from './CallUI';
 import { DeviceApprovalBanner } from './DeviceApprovalBanner';
@@ -28,7 +27,7 @@ export function AppShell() {
     const stopApproval = startDeviceApprovalListener({
       ownUserId: userId,
       ownDeviceId: deviceId,
-      getPriv: () => loadDevicePrivateKey(devLocalSecretStore, userId, deviceId),
+      getPriv: () => cachedUserKey(userId),
     });
     return () => {
       stopKeySync();
diff --git a/apps/desktop/src/components/ForwardDialog.tsx b/apps/desktop/src/components/ForwardDialog.tsx
index 7ce1ac2..082ab3c 100644
--- a/apps/desktop/src/components/ForwardDialog.tsx
+++ b/apps/desktop/src/components/ForwardDialog.tsx
@@ -1,4 +1,3 @@
-import { loadDevicePrivateKey } from '@chat-app/shared/auth';
 import {
   type AttachmentHandle,
   type DecryptedMessage,
@@ -15,8 +14,8 @@ import { useTranslation } from 'react-i18next';
 
 import { useAuth } from '../context/AuthContext';
 import { useConversationsContext } from '../context/ConversationsContext';
-import { devLocalSecretStore } from '../lib/secretStore';
 import { supabase } from '../lib/supabase';
+import { cachedUserKey } from '../lib/userIdentity';
 import { Avatar } from './Avatar';
 import { ForwardIcon, SpinnerIcon, UsersIcon, XIcon } from './icons';
 
@@ -89,8 +88,8 @@ export function ForwardDialog({ open, message, currentConversationId, onClose }:
     setBusy(true);
     setError(null);
     try {
-      const priv = await loadDevicePrivateKey(devLocalSecretStore, session.user.id, device.id);
-      if (!priv) throw new Error('private key not loaded');
+      const priv = await cachedUserKey(session.user.id);
+      if (!priv) throw new Error('user key not unlocked');
 
       const hasAttachments = sourceAttachments.length > 0;
       const text = preview || (hasAttachments ? '' : '');
diff --git a/apps/desktop/src/components/MessageBubble.tsx b/apps/desktop/src/components/MessageBubble.tsx
index 4862c75..c48aaa1 100644
--- a/apps/desktop/src/components/MessageBubble.tsx
+++ b/apps/desktop/src/components/MessageBubble.tsx
@@ -1,4 +1,3 @@
-import { loadDevicePrivateKey } from '@chat-app/shared/auth';
 import {
   type DecryptedMessage,
   editEncryptedMessage,
@@ -11,8 +10,8 @@ import { createPortal } from 'react-dom';
 import { useTranslation } from 'react-i18next';
 
 import { useAuth } from '../context/AuthContext';
-import { devLocalSecretStore } from '../lib/secretStore';
 import { supabase } from '../lib/supabase';
+import { cachedUserKey } from '../lib/userIdentity';
 import type { AggregatedReaction } from '../lib/useMessageReactions';
 import { summarizePollVotes } from '../lib/conversationFeatures';
 import { extractFirstUrl } from '../lib/useLinkPreview';
@@ -201,8 +200,8 @@ export function MessageBubble({
     setBusy(true);
     setEditError(null);
     try {
-      const priv = await loadDevicePrivateKey(devLocalSecretStore, session.user.id, device.id);
-      if (!priv) throw new Error('private key not loaded');
+      const priv = await cachedUserKey(session.user.id);
+      if (!priv) throw new Error('user key not unlocked');
       await editEncryptedMessage({
         client: supabase,
         messageId: message.id,
diff --git a/apps/desktop/src/context/CallContext.tsx b/apps/desktop/src/context/CallContext.tsx
index d174e78..80bea6c 100644
--- a/apps/desktop/src/context/CallContext.tsx
+++ b/apps/desktop/src/context/CallContext.tsx
@@ -1,4 +1,3 @@
-import { loadDevicePrivateKey } from '@chat-app/shared/auth';
 import { sendEncryptedMessage } from '@chat-app/shared/chat';
 import {
   type CallKind,
@@ -114,8 +113,8 @@ import {
   type ScreenSharePreset,
   updateScreenShareSettings,
 } from '../lib/screenShareSettings';
-import { devLocalSecretStore } from '../lib/secretStore';
 import { supabase } from '../lib/supabase';
+import { cachedUserKey } from '../lib/userIdentity';
 import { setWindowFullscreen } from '../lib/windowFullscreen';
 
 export type CallState =
@@ -448,11 +447,7 @@ export function CallProvider({ children }: { children: ReactNode }) {
     ) => {
       if (!session?.user.id || !device?.id) return;
       try {
-        const priv = await loadDevicePrivateKey(
-          devLocalSecretStore,
-          session.user.id,
-          device.id,
-        );
+        const priv = await cachedUserKey(session.user.id);
         if (!priv) return;
         const payload = JSON.stringify({
           v: 1,
diff --git a/apps/desktop/src/lib/conversationKeySync.ts b/apps/desktop/src/lib/conversationKeySync.ts
index 50d05e8..7a7e1e9 100644
--- a/apps/desktop/src/lib/conversationKeySync.ts
+++ b/apps/desktop/src/lib/conversationKeySync.ts
@@ -1,16 +1,14 @@
-import { loadDevicePrivateKey } from '@chat-app/shared/auth';
-import { type OwnDeviceCtx, shareConvKeyToDevice } from '@chat-app/shared/chat';
+import { type OwnUserCtx, shareConvKeyToUser } from '@chat-app/shared/chat';
 import { pgHexToBytes } from '@chat-app/shared/supabase';
 
-import { devLocalSecretStore } from './secretStore';
 import { supabase } from './supabase';
 
 // Watches the `devices` table for new entries AND, on mount, scans every
 // conversation we participate in for missing key bundles. Fills gaps by
-// re-wrapping our active conv-key for the missing recipient devices.
+// re-wrapping our active conv-key for the missing recipient users.
 //
-// This fixes the "cannot decrypt" cliff for devices that registered while
-// no other participant device was online to share the key with them.
+// This fixes the "cannot decrypt" cliff for users that joined while no
+// other participant was online to share the key with them.
 
 export interface SyncCtx {
   myUserId: string;
@@ -57,8 +55,6 @@ export function startConversationKeySync(
   void ownUserId;
   void ownDeviceId;
   void backfilledKey;
-  void loadDevicePrivateKey;
-  void devLocalSecretStore;
   void supabase;
   return () => {};
 }
@@ -70,10 +66,10 @@ export function startConversationKeySync(
 // `wrapForOneDevice` and `syncOneConversationGaps` are exported below for
 // the device-approval module — once the user explicitly approves a new
 // device the approval flow re-uses these helpers to wrap conv-keys for
-// that specific deviceId.
+// that specific user.
 void (() => {
   void listMyConversationIds;
-  void listConversationDevices;
+  void listConversationMembers;
   void listExistingKeyRecipients;
   void getActiveKeyVersion;
   void syncAllExistingGaps;
@@ -94,9 +90,9 @@ async function listMyConversationIds(myUserId: string): Promise<string[]> {
   return (data ?? []).map((r) => r.conversation_id as string);
 }
 
-async function listConversationDevices(
+async function listConversationMembers(
   conversationId: string,
-): Promise<{ id: string; user_id: string; public_key: string }[]> {
+): Promise<{ user_id: string; public_key: string }[]> {
   const { data: members, error: mErr } = await supabase
     .from('conversation_members')
     .select('user_id')
@@ -109,15 +105,14 @@ async function listConversationDevices(
   const userIds = (members ?? []).map((m) => m.user_id as string);
   if (userIds.length === 0) return [];
 
-  const { data: devices, error: dErr } = await supabase
-    .from('devices')
-    .select('id, user_id, public_key')
+  const { data: keys, error: kErr } = await rawFrom('user_keys')
+    .select('user_id, public_key')
     .in('user_id', userIds);
-  if (dErr) {
-    console.warn('keySync: devices lookup failed', dErr);
+  if (kErr) {
+    console.warn('keySync: user-keys lookup failed', kErr);
     return [];
   }
-  return (devices ?? []) as { id: string; user_id: string; public_key: string }[];
+  return (keys ?? []) as { user_id: string; public_key: string }[];
 }
 
 async function listExistingKeyRecipients(
@@ -125,14 +120,14 @@ async function listExistingKeyRecipients(
   keyVersion: number,
 ): Promise<Set<string>> {
   const { data, error } = await rawFrom('conversation_keys')
-    .select('recipient_device_id')
+    .select('recipient_user_id')
     .eq('conversation_id', conversationId)
     .eq('key_version', keyVersion);
   if (error) {
     console.warn('keySync: existing keys lookup failed', error);
     return new Set();
   }
-  return new Set((data ?? []).map((r: { recipient_device_id: string }) => r.recipient_device_id));
+  return new Set((data ?? []).map((r: { recipient_user_id: string }) => r.recipient_user_id));
 }
 
 async function getActiveKeyVersion(conversationId: string): Promise<number> {
@@ -160,33 +155,32 @@ async function syncAllExistingGaps(ctx: SyncCtx): Promise<void> {
 
 export async function syncOneConversationGaps(ctx: SyncCtx, convId: string): Promise<void> {
   const version = await getActiveKeyVersion(convId);
-  const devices = await listConversationDevices(convId);
-  if (devices.length === 0) return;
+  const members = await listConversationMembers(convId);
+  if (members.length === 0) return;
 
   const recipients = await listExistingKeyRecipients(convId, version);
-  const ownCtx: OwnDeviceCtx = {
+  const ownCtx: OwnUserCtx = {
     userId: ctx.myUserId,
-    deviceId: ctx.myDeviceId,
     privateKey: ctx.priv,
   };
 
-  for (const dev of devices) {
-    if (recipients.has(dev.id)) continue;
-    // Skip our own device — we already have the bundle if we're capable of
+  for (const m of members) {
+    if (recipients.has(m.user_id)) continue;
+    // Skip our own user — we already have the bundle if we're capable of
     // sharing (or don't need it if we ourselves haven't been wrapped yet).
-    if (dev.id === ctx.myDeviceId) continue;
+    if (m.user_id === ctx.myUserId) continue;
     try {
-      await shareConvKeyToDevice(supabase, convId, dev.id, pgHexToBytes(dev.public_key), ownCtx);
+      await shareConvKeyToUser(supabase, convId, m.user_id, pgHexToBytes(m.public_key), ownCtx);
     } catch (err: unknown) {
       // Backfill is best-effort. Most common silent failures:
       //   - tryGetConvKey couldn't unwrap (another peer will fill the gap).
-      //   - RLS rejects because the recipient's owner is a pending (not-yet
+      //   - RLS rejects because the recipient is a pending (not-yet
       //     accepted) DM member, or was removed from the conv.
       // Both are recoverable / expected, swallow without spam.
       if (isExpectedShareFailure(err)) continue;
-      console.warn('keySync: shareConvKeyToDevice gap-fill failed', {
+      console.warn('keySync: shareConvKeyToUser gap-fill failed', {
         convId,
-        recipient: dev.id,
+        recipient: m.user_id,
         err,
       });
     }
@@ -209,12 +203,20 @@ function isExpectedShareFailure(err: unknown): boolean {
   );
 }
 
+// Approval-flow helper. The legacy signature took (deviceId, userId,
+// devicePubHex) because conv-keys were wrapped per-device. In the per-user
+// model only the user dimension matters, so the device-id parameter is
+// ignored and the public key passed in MUST be the recipient user's
+// user_keys.public_key (callers will be updated alongside the broader
+// approval-flow rework).
 export async function wrapForOneDevice(
   ctx: SyncCtx,
   newDeviceId: string,
   newDeviceUserId: string,
   newDevicePubHex: string,
 ): Promise<void> {
+  void newDeviceId; // kept for API compat; no longer used
+
   const myConvs = new Set(await listMyConversationIds(ctx.myUserId));
   const { data: peerMember, error: pErr } = await supabase
     .from('conversation_members')
@@ -230,16 +232,15 @@ export async function wrapForOneDevice(
   if (sharedConvs.length === 0) return;
 
   const newPub = pgHexToBytes(newDevicePubHex);
-  const ownCtx: OwnDeviceCtx = {
+  const ownCtx: OwnUserCtx = {
     userId: ctx.myUserId,
-    deviceId: ctx.myDeviceId,
     privateKey: ctx.priv,
   };
   for (const convId of sharedConvs) {
     try {
-      await shareConvKeyToDevice(supabase, convId, newDeviceId, newPub, ownCtx);
+      await shareConvKeyToUser(supabase, convId, newDeviceUserId, newPub, ownCtx);
     } catch (err: unknown) {
-      console.warn('keySync: shareConvKeyToDevice failed', { convId, err });
+      console.warn('keySync: shareConvKeyToUser failed', { convId, err });
     }
   }
 }
diff --git a/apps/desktop/src/lib/useConversationMessages.ts b/apps/desktop/src/lib/useConversationMessages.ts
index 79bf879..3b10179 100644
--- a/apps/desktop/src/lib/useConversationMessages.ts
+++ b/apps/desktop/src/lib/useConversationMessages.ts
@@ -1,4 +1,3 @@
-import { loadDevicePrivateKey } from '@chat-app/shared/auth';
 import {
   type AttachmentHandle,
   type DecryptedMessage,
@@ -30,8 +29,8 @@ import {
   shouldGiveUp,
   subscribeOutbox,
 } from './messageOutbox';
-import { devLocalSecretStore } from './secretStore';
 import { supabase } from './supabase';
+import { cachedUserKey } from './userIdentity';
 
 interface State {
   messages: DecryptedMessage[];
@@ -90,25 +89,25 @@ export function useConversationMessages({ conversationId, userId, deviceId }: Ar
     });
   }, [conversationId]);
 
-  // Load own private key once per (user, device).
+  // Load own user private key once per user.
   useEffect(() => {
     privateKeyRef.current = null;
-    if (!userId || !deviceId) return;
-    void loadDevicePrivateKey(devLocalSecretStore, userId, deviceId).then((pk) => {
+    if (!userId) return;
+    void cachedUserKey(userId).then((pk) => {
       privateKeyRef.current = pk;
     });
-  }, [userId, deviceId]);
+  }, [userId]);
 
   const decryptBatch = useCallback(
     async (messages: MessageWithCipher[]): Promise<DecryptedMessage[]> => {
       const priv = privateKeyRef.current;
-      if (!priv || !deviceId || messages.length === 0) {
+      if (!priv || !userId || messages.length === 0) {
         return messages.map((m) => ({ ...m, plaintext: null }));
       }
       return decryptMessages({
         client: supabase,
         messages,
-        ownDeviceId: deviceId,
+        ownUserId: userId,
         ownPrivateKey: priv,
         // Offload the symmetric decrypt + utf-8 decode to a Web Worker so
         // the main thread stays responsive during bulk operations (initial
@@ -116,7 +115,7 @@ export function useConversationMessages({ conversationId, userId, deviceId }: Ar
         aeadBatchDelegate: decryptBatchWorker,
       });
     },
-    [deviceId],
+    [userId],
   );
 
   const refresh = useCallback(async () => {
diff --git a/packages/shared/src/chat/messages.ts b/packages/shared/src/chat/messages.ts
index a9c488d..850d6cc 100644
--- a/packages/shared/src/chat/messages.ts
+++ b/packages/shared/src/chat/messages.ts
@@ -440,7 +440,7 @@ export async function removeReaction(
 export interface DecryptParams {
   client: AppSupabaseClient;
   messages: MessageWithCipher[];
-  ownDeviceId: string;
+  ownUserId: string;
   ownPrivateKey: Uint8Array;
   /**
    * Optional delegate that performs the symmetric-decrypt + utf-8 decode
@@ -483,7 +483,7 @@ export async function decryptMessages(opts: DecryptParams): Promise<DecryptedMes
       const handle = await tryGetConvKey(
         opts.client,
         m.conversationId,
-        opts.ownDeviceId,
+        opts.ownUserId,
         opts.ownPrivateKey,
         m.keyVersion,
       );