Implement client message IDs

backend/services/main/routes/account.py

@@ -7,6 +7,7 @@ from fastapi import APIRouter, BackgroundTasks, Depends, HTTPException, status,
 from sqlalchemy.orm import Session
 from sqlalchemy import inspect, text
 import uuid
+import secrets
 from user_agents import parse as parse_ua
 from fastapi.security import HTTPBearer, HTTPAuthorizationCredentials
 
@@ -28,6 +29,16 @@ _SERVER_INSTANCE_ID: str | None = None
 _INSTANCE_ID_FILE = Path(__file__).resolve().parent.parent / ".fromchat_instance_id"
 
 
+def allocate_user_id(db: Session) -> int:
+    """First registered user gets id 1; subsequent users get random unique ids."""
+    if db.query(User).count() == 0:
+        return 1
+    while True:
+        candidate = secrets.randbelow(2_147_483_646) + 2
+        if db.query(User).filter(User.id == candidate).first() is None:
+            return candidate
+
+
 def get_server_instance_id() -> str:
     """Stable server fingerprint; UUID generated once and persisted next to the main service package."""
     global _SERVER_INSTANCE_ID
@@ -289,6 +300,7 @@ def register(
     is_owner = not owner_exists and username == OWNER_USERNAME
     
     new_user = User(
+        id=allocate_user_id(db),
         username=username,
         display_name=display_name,
         password_hash=hashed_password,

backend/services/main/routes/envelope_messaging.py

@@ -37,7 +37,7 @@ from ..service_calls import (
     get_resumable_upload_data_in_storage,
     delete_resumable_upload_in_storage,
 )
-from .messaging import messagingManager, convert_dm_envelope
+from .messaging import messagingManager, convert_dm_envelope, convert_dm_envelope_for_user
 from ..push_service import push_service
 
 logger = logging.getLogger("uvicorn.error")
@@ -360,12 +360,17 @@ async def send_encrypted_message(
         )
 
         # Send user-specific WebSocket updates (each user gets only their MEK and files metadata)
-        recipient_payload = convert_dm_envelope(db, dm_envelope, dm_envelope.recipient_id)
+        recipient_payload = convert_dm_envelope_for_user(
+            db, dm_envelope, dm_envelope.recipient_id,
+        )
         await messagingManager.send_update_to_user(dm_envelope.recipient_id, "dmNew", recipient_payload, db)
 
-        sender_payload = convert_dm_envelope(db, dm_envelope, dm_envelope.sender_id)
-        if request.client_message_id:
-            sender_payload["client_message_id"] = request.client_message_id
+        sender_payload = convert_dm_envelope_for_user(
+            db,
+            dm_envelope,
+            dm_envelope.sender_id,
+            sender_client_message_id=request.client_message_id,
+        )
         await messagingManager.send_update_to_user(dm_envelope.sender_id, "dmNew", sender_payload, db)
 
         try:

backend/services/main/routes/messaging.py

@@ -314,6 +314,27 @@ def convert_dm_envelope(db: Session, envelope: DMEnvelope, user_id: int | None =
     return result
 
 
+def convert_dm_envelope_for_user(
+    db: Session,
+    envelope: DMEnvelope,
+    user_id: int | None,
+    *,
+    sender_client_message_id: str | None = None,
+) -> dict:
+    """
+    Per-user DM payload. [sender_client_message_id] is included only for the sender so clients
+    can match optimistic rows to the server ack; never exposed to the recipient.
+    """
+    payload = convert_dm_envelope(db, envelope, user_id)
+    if (
+        sender_client_message_id
+        and user_id is not None
+        and user_id == envelope.sender_id
+    ):
+        payload["client_message_id"] = sender_client_message_id
+    return payload
+
+
 async def _send_message_internal(
     message_request: SendMessageRequest,
     current_user: User,