Implement client message IDs

backend/services/main/main.py

@@ -11,6 +11,7 @@ from sqlalchemy.orm.exc import DetachedInstanceError
 
 # Import from same directory
 from .routes import account, messaging, profile, push, webrtc, devices, moderation, download, keys, envelope_messaging, livekit
+from .routes.account import get_server_instance_id
 from .models import User
 from .constants import OWNER_USERNAME
 from .utils import get_client_ip
@@ -155,9 +156,18 @@ async def lifespan(app: FastAPI):
         except asyncio.CancelledError:
             pass
 
+INSTANCE_ID_HEADER = "X-FromChat-Instance-Id"
+
 # Initialize FastAPI
 app = FastAPI(title="FromChat", lifespan=lifespan)
 
+
+@app.middleware("http")
+async def server_instance_id_middleware(request: Request, call_next):
+    response = await call_next(request)
+    response.headers[INSTANCE_ID_HEADER] = get_server_instance_id()
+    return response
+
 # Add rate limiting middleware
 app.state.limiter = limiter
 app.add_middleware(SlowAPIMiddleware)
@@ -308,6 +318,7 @@ app.add_middleware(
     allow_credentials=True,
     allow_methods=["*"],
     allow_headers=["*"],
+    expose_headers=["*", INSTANCE_ID_HEADER],
 )
 
 # Routes

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,

backend/services/main/websocket/handlers.py

@@ -156,6 +156,12 @@ async def dmSend(manager: MessaggingSocketManager, websocket: WebSocket, db: Ses
         if key not in payload:
             raise HTTPException(status_code=400, detail=f"Missing {key}")
 
+    client_message_id = payload.get("client_message_id") or payload.get("clientMessageId")
+    if isinstance(client_message_id, str):
+        client_message_id = client_message_id.strip() or None
+    else:
+        client_message_id = None
+
     env = DMEnvelope(
         sender_id=user.id,
         recipient_id=int(payload["recipientId"]),
@@ -191,13 +197,16 @@ async def dmSend(manager: MessaggingSocketManager, websocket: WebSocket, db: Ses
     }
     await manager.send_update_to_user(env.recipient_id, "dmNew", recipient_payload["data"], db)
 
-    # Send to sender with their MEK
+    # Send to sender with their MEK (client_message_id only for optimistic ack matching)
+    sender_data = {
+        **base_payload,
+        "wrapped_mek_b64": env.sender_wrapped_mek_b64,
+    }
+    if client_message_id:
+        sender_data["client_message_id"] = client_message_id
     sender_payload = {
         "type": "dmNew",
-        "data": {
-            **base_payload,
-            "wrapped_mek_b64": env.sender_wrapped_mek_b64,
-        }
+        "data": sender_data,
     }
     await manager.send_update_to_user(env.sender_id, "dmNew", sender_payload["data"], db)