diff --git a/alembic/versions/0002_message_reliability_tables.py b/alembic/versions/0002_message_reliability_tables.py
new file mode 100644
index 0000000..a0027b6
--- /dev/null
+++ b/alembic/versions/0002_message_reliability_tables.py
@@ -0,0 +1,83 @@
+"""message reliability tables
+
+Revision ID: 0002_message_reliability_tables
+Revises: 0001_initial_schema
+Create Date: 2026-03-08 01:30:00.000000
+"""
+
+from typing import Sequence, Union
+
+import sqlalchemy as sa
+from alembic import op
+
+
+revision: str = "0002_message_reliability_tables"
+down_revision: Union[str, Sequence[str], None] = "0001_initial_schema"
+branch_labels: Union[str, Sequence[str], None] = None
+depends_on: Union[str, Sequence[str], None] = None
+
+
+def upgrade() -> None:
+    op.create_table(
+        "message_idempotency_keys",
+        sa.Column("id", sa.Integer(), nullable=False),
+        sa.Column("chat_id", sa.Integer(), nullable=False),
+        sa.Column("sender_id", sa.Integer(), nullable=False),
+        sa.Column("client_message_id", sa.String(length=64), nullable=False),
+        sa.Column("message_id", sa.Integer(), nullable=False),
+        sa.Column("created_at", sa.DateTime(timezone=True), server_default=sa.func.now(), nullable=False),
+        sa.ForeignKeyConstraint(["chat_id"], ["chats.id"], name=op.f("fk_message_idempotency_keys_chat_id_chats"), ondelete="CASCADE"),
+        sa.ForeignKeyConstraint(["sender_id"], ["users.id"], name=op.f("fk_message_idempotency_keys_sender_id_users"), ondelete="CASCADE"),
+        sa.ForeignKeyConstraint(
+            ["message_id"],
+            ["messages.id"],
+            name=op.f("fk_message_idempotency_keys_message_id_messages"),
+            ondelete="CASCADE",
+        ),
+        sa.PrimaryKeyConstraint("id", name=op.f("pk_message_idempotency_keys")),
+        sa.UniqueConstraint("chat_id", "sender_id", "client_message_id", name="uq_msg_idem_chat_sender_client"),
+    )
+    op.create_index(op.f("ix_message_idempotency_keys_id"), "message_idempotency_keys", ["id"], unique=False)
+    op.create_index(op.f("ix_message_idempotency_keys_chat_id"), "message_idempotency_keys", ["chat_id"], unique=False)
+    op.create_index(
+        op.f("ix_message_idempotency_keys_sender_id"),
+        "message_idempotency_keys",
+        ["sender_id"],
+        unique=False,
+    )
+    op.create_index(
+        op.f("ix_message_idempotency_keys_message_id"),
+        "message_idempotency_keys",
+        ["message_id"],
+        unique=False,
+    )
+
+    op.create_table(
+        "message_receipts",
+        sa.Column("id", sa.Integer(), nullable=False),
+        sa.Column("chat_id", sa.Integer(), nullable=False),
+        sa.Column("user_id", sa.Integer(), nullable=False),
+        sa.Column("last_delivered_message_id", sa.Integer(), nullable=True),
+        sa.Column("last_read_message_id", sa.Integer(), nullable=True),
+        sa.Column("updated_at", sa.DateTime(timezone=True), server_default=sa.func.now(), nullable=False),
+        sa.ForeignKeyConstraint(["chat_id"], ["chats.id"], name=op.f("fk_message_receipts_chat_id_chats"), ondelete="CASCADE"),
+        sa.ForeignKeyConstraint(["user_id"], ["users.id"], name=op.f("fk_message_receipts_user_id_users"), ondelete="CASCADE"),
+        sa.PrimaryKeyConstraint("id", name=op.f("pk_message_receipts")),
+        sa.UniqueConstraint("chat_id", "user_id", name="uq_msg_receipts_chat_user"),
+    )
+    op.create_index(op.f("ix_message_receipts_id"), "message_receipts", ["id"], unique=False)
+    op.create_index(op.f("ix_message_receipts_chat_id"), "message_receipts", ["chat_id"], unique=False)
+    op.create_index(op.f("ix_message_receipts_user_id"), "message_receipts", ["user_id"], unique=False)
+
+
+def downgrade() -> None:
+    op.drop_index(op.f("ix_message_receipts_user_id"), table_name="message_receipts")
+    op.drop_index(op.f("ix_message_receipts_chat_id"), table_name="message_receipts")
+    op.drop_index(op.f("ix_message_receipts_id"), table_name="message_receipts")
+    op.drop_table("message_receipts")
+
+    op.drop_index(op.f("ix_message_idempotency_keys_message_id"), table_name="message_idempotency_keys")
+    op.drop_index(op.f("ix_message_idempotency_keys_sender_id"), table_name="message_idempotency_keys")
+    op.drop_index(op.f("ix_message_idempotency_keys_chat_id"), table_name="message_idempotency_keys")
+    op.drop_index(op.f("ix_message_idempotency_keys_id"), table_name="message_idempotency_keys")
+    op.drop_table("message_idempotency_keys")
diff --git a/app/database/models.py b/app/database/models.py
index 97a9473..a385adc 100644
--- a/app/database/models.py
+++ b/app/database/models.py
@@ -2,7 +2,7 @@ from app.auth.models import EmailVerificationToken, PasswordResetToken
 from app.chats.models import Chat, ChatMember
 from app.email.models import EmailLog
 from app.media.models import Attachment
-from app.messages.models import Message
+from app.messages.models import Message, MessageIdempotencyKey, MessageReceipt
 from app.notifications.models import NotificationLog
 from app.users.models import User
 
@@ -13,6 +13,8 @@ __all__ = [
     "EmailLog",
     "EmailVerificationToken",
     "Message",
+    "MessageIdempotencyKey",
+    "MessageReceipt",
     "NotificationLog",
     "PasswordResetToken",
     "User",
diff --git a/app/messages/models.py b/app/messages/models.py
index 870808b..94882ab 100644
--- a/app/messages/models.py
+++ b/app/messages/models.py
@@ -2,7 +2,7 @@ from datetime import datetime
 from enum import Enum
 from typing import TYPE_CHECKING
 
-from sqlalchemy import DateTime, Enum as SAEnum, ForeignKey, Text, func
+from sqlalchemy import DateTime, Enum as SAEnum, ForeignKey, String, Text, UniqueConstraint, func
 from sqlalchemy.orm import Mapped, mapped_column, relationship
 
 from app.database.base import Base
@@ -42,3 +42,34 @@ class Message(Base):
     chat: Mapped["Chat"] = relationship(back_populates="messages")
     sender: Mapped["User"] = relationship(back_populates="sent_messages")
     attachments: Mapped[list["Attachment"]] = relationship(back_populates="message", cascade="all, delete-orphan")
+
+
+class MessageIdempotencyKey(Base):
+    __tablename__ = "message_idempotency_keys"
+    __table_args__ = (
+        UniqueConstraint("chat_id", "sender_id", "client_message_id", name="uq_msg_idem_chat_sender_client"),
+    )
+
+    id: Mapped[int] = mapped_column(primary_key=True, index=True)
+    chat_id: Mapped[int] = mapped_column(ForeignKey("chats.id", ondelete="CASCADE"), nullable=False, index=True)
+    sender_id: Mapped[int] = mapped_column(ForeignKey("users.id", ondelete="CASCADE"), nullable=False, index=True)
+    client_message_id: Mapped[str] = mapped_column(String(64), nullable=False)
+    message_id: Mapped[int] = mapped_column(ForeignKey("messages.id", ondelete="CASCADE"), nullable=False, index=True)
+    created_at: Mapped[datetime] = mapped_column(DateTime(timezone=True), server_default=func.now(), nullable=False)
+
+
+class MessageReceipt(Base):
+    __tablename__ = "message_receipts"
+    __table_args__ = (UniqueConstraint("chat_id", "user_id", name="uq_msg_receipts_chat_user"),)
+
+    id: Mapped[int] = mapped_column(primary_key=True, index=True)
+    chat_id: Mapped[int] = mapped_column(ForeignKey("chats.id", ondelete="CASCADE"), nullable=False, index=True)
+    user_id: Mapped[int] = mapped_column(ForeignKey("users.id", ondelete="CASCADE"), nullable=False, index=True)
+    last_delivered_message_id: Mapped[int | None] = mapped_column(nullable=True)
+    last_read_message_id: Mapped[int | None] = mapped_column(nullable=True)
+    updated_at: Mapped[datetime] = mapped_column(
+        DateTime(timezone=True),
+        server_default=func.now(),
+        onupdate=func.now(),
+        nullable=False,
+    )
diff --git a/app/messages/repository.py b/app/messages/repository.py
index 6162d02..a0da9e0 100644
--- a/app/messages/repository.py
+++ b/app/messages/repository.py
@@ -1,7 +1,7 @@
 from sqlalchemy import select
 from sqlalchemy.ext.asyncio import AsyncSession
 
-from app.messages.models import Message, MessageType
+from app.messages.models import Message, MessageIdempotencyKey, MessageReceipt, MessageType
 
 
 async def create_message(
@@ -18,6 +18,45 @@ async def create_message(
     return message
 
 
+async def get_message_by_client_message_id(
+    db: AsyncSession,
+    *,
+    chat_id: int,
+    sender_id: int,
+    client_message_id: str,
+) -> Message | None:
+    result = await db.execute(
+        select(Message)
+        .join(MessageIdempotencyKey, MessageIdempotencyKey.message_id == Message.id)
+        .where(
+            MessageIdempotencyKey.chat_id == chat_id,
+            MessageIdempotencyKey.sender_id == sender_id,
+            MessageIdempotencyKey.client_message_id == client_message_id,
+        )
+        .limit(1)
+    )
+    return result.scalar_one_or_none()
+
+
+async def create_message_idempotency_key(
+    db: AsyncSession,
+    *,
+    chat_id: int,
+    sender_id: int,
+    client_message_id: str,
+    message_id: int,
+) -> MessageIdempotencyKey:
+    key = MessageIdempotencyKey(
+        chat_id=chat_id,
+        sender_id=sender_id,
+        client_message_id=client_message_id,
+        message_id=message_id,
+    )
+    db.add(key)
+    await db.flush()
+    return key
+
+
 async def get_message_by_id(db: AsyncSession, message_id: int) -> Message | None:
     result = await db.execute(select(Message).where(Message.id == message_id))
     return result.scalar_one_or_none()
@@ -39,3 +78,32 @@ async def list_chat_messages(
 
 async def delete_message(db: AsyncSession, message: Message) -> None:
     await db.delete(message)
+
+
+async def get_message_receipt(db: AsyncSession, *, chat_id: int, user_id: int) -> MessageReceipt | None:
+    result = await db.execute(
+        select(MessageReceipt).where(
+            MessageReceipt.chat_id == chat_id,
+            MessageReceipt.user_id == user_id,
+        )
+    )
+    return result.scalar_one_or_none()
+
+
+async def create_message_receipt(
+    db: AsyncSession,
+    *,
+    chat_id: int,
+    user_id: int,
+    last_delivered_message_id: int | None,
+    last_read_message_id: int | None,
+) -> MessageReceipt:
+    receipt = MessageReceipt(
+        chat_id=chat_id,
+        user_id=user_id,
+        last_delivered_message_id=last_delivered_message_id,
+        last_read_message_id=last_read_message_id,
+    )
+    db.add(receipt)
+    await db.flush()
+    return receipt
diff --git a/app/messages/router.py b/app/messages/router.py
index 3a4181d..215b941 100644
--- a/app/messages/router.py
+++ b/app/messages/router.py
@@ -3,8 +3,9 @@ from sqlalchemy.ext.asyncio import AsyncSession
 
 from app.auth.service import get_current_user
 from app.database.session import get_db
-from app.messages.schemas import MessageCreateRequest, MessageRead, MessageUpdateRequest
+from app.messages.schemas import MessageCreateRequest, MessageRead, MessageStatusUpdateRequest, MessageUpdateRequest
 from app.messages.service import create_chat_message, delete_message, get_messages, update_message
+from app.realtime.schemas import MessageStatusPayload
 from app.realtime.service import realtime_gateway
 from app.users.models import User
 
@@ -18,7 +19,11 @@ async def create_message(
     current_user: User = Depends(get_current_user),
 ) -> MessageRead:
     message = await create_chat_message(db, sender_id=current_user.id, payload=payload)
-    await realtime_gateway.publish_message_created(message=message, sender_id=current_user.id)
+    await realtime_gateway.publish_message_created(
+        message=message,
+        sender_id=current_user.id,
+        client_message_id=payload.client_message_id,
+    )
     return message
 
 
@@ -50,3 +55,17 @@ async def remove_message(
     current_user: User = Depends(get_current_user),
 ) -> None:
     await delete_message(db, message_id=message_id, user_id=current_user.id)
+
+
+@router.post("/status")
+async def update_status(
+    payload: MessageStatusUpdateRequest,
+    db: AsyncSession = Depends(get_db),
+    current_user: User = Depends(get_current_user),
+) -> dict[str, int]:
+    return await realtime_gateway.handle_message_status(
+        db,
+        user_id=current_user.id,
+        payload=MessageStatusPayload(chat_id=payload.chat_id, message_id=payload.message_id),
+        event=payload.status,
+    )
diff --git a/app/messages/schemas.py b/app/messages/schemas.py
index 735d8a1..17e370b 100644
--- a/app/messages/schemas.py
+++ b/app/messages/schemas.py
@@ -1,4 +1,5 @@
 from datetime import datetime
+from typing import Literal
 
 from pydantic import BaseModel, ConfigDict, Field
 
@@ -21,7 +22,14 @@ class MessageCreateRequest(BaseModel):
     chat_id: int
     type: MessageType = MessageType.TEXT
     text: str | None = Field(default=None, max_length=4096)
+    client_message_id: str | None = Field(default=None, min_length=8, max_length=64)
 
 
 class MessageUpdateRequest(BaseModel):
     text: str = Field(min_length=1, max_length=4096)
+
+
+class MessageStatusUpdateRequest(BaseModel):
+    chat_id: int
+    message_id: int
+    status: Literal["message_delivered", "message_read"]
diff --git a/app/messages/service.py b/app/messages/service.py
index 3485d25..2d58e38 100644
--- a/app/messages/service.py
+++ b/app/messages/service.py
@@ -1,29 +1,60 @@
 from fastapi import HTTPException, status
+from sqlalchemy.exc import IntegrityError
 from sqlalchemy.ext.asyncio import AsyncSession
 
 from app.chats.service import ensure_chat_membership
 from app.messages import repository
 from app.messages.models import Message
 from app.messages.spam_guard import enforce_message_spam_policy
-from app.messages.schemas import MessageCreateRequest, MessageUpdateRequest
+from app.messages.schemas import MessageCreateRequest, MessageStatusUpdateRequest, MessageUpdateRequest
 from app.notifications.service import dispatch_message_notifications
 
 
 async def create_chat_message(db: AsyncSession, *, sender_id: int, payload: MessageCreateRequest) -> Message:
     await ensure_chat_membership(db, chat_id=payload.chat_id, user_id=sender_id)
+    if payload.client_message_id:
+        existing = await repository.get_message_by_client_message_id(
+            db,
+            chat_id=payload.chat_id,
+            sender_id=sender_id,
+            client_message_id=payload.client_message_id,
+        )
+        if existing:
+            return existing
     if payload.type.value == "text" and not (payload.text and payload.text.strip()):
         raise HTTPException(status_code=status.HTTP_422_UNPROCESSABLE_ENTITY, detail="Text message cannot be empty")
     await enforce_message_spam_policy(user_id=sender_id, chat_id=payload.chat_id, text=payload.text)
 
-    message = await repository.create_message(
-        db,
-        chat_id=payload.chat_id,
-        sender_id=sender_id,
-        message_type=payload.type,
-        text=payload.text,
-    )
-    await db.commit()
-    await db.refresh(message)
+    try:
+        message = await repository.create_message(
+            db,
+            chat_id=payload.chat_id,
+            sender_id=sender_id,
+            message_type=payload.type,
+            text=payload.text,
+        )
+        if payload.client_message_id:
+            await repository.create_message_idempotency_key(
+                db,
+                chat_id=payload.chat_id,
+                sender_id=sender_id,
+                client_message_id=payload.client_message_id,
+                message_id=message.id,
+            )
+        await db.commit()
+        await db.refresh(message)
+    except IntegrityError:
+        await db.rollback()
+        if payload.client_message_id:
+            existing = await repository.get_message_by_client_message_id(
+                db,
+                chat_id=payload.chat_id,
+                sender_id=sender_id,
+                client_message_id=payload.client_message_id,
+            )
+            if existing:
+                return existing
+        raise
     try:
         await dispatch_message_notifications(db, message)
     except Exception:
@@ -73,3 +104,43 @@ async def delete_message(db: AsyncSession, *, message_id: int, user_id: int) ->
         raise HTTPException(status_code=status.HTTP_403_FORBIDDEN, detail="You can delete only your own messages")
     await repository.delete_message(db, message)
     await db.commit()
+
+
+async def mark_message_status(
+    db: AsyncSession,
+    *,
+    user_id: int,
+    payload: MessageStatusUpdateRequest,
+) -> dict[str, int]:
+    await ensure_chat_membership(db, chat_id=payload.chat_id, user_id=user_id)
+    message = await repository.get_message_by_id(db, payload.message_id)
+    if not message or message.chat_id != payload.chat_id:
+        raise HTTPException(status_code=status.HTTP_404_NOT_FOUND, detail="Message not found")
+
+    receipt = await repository.get_message_receipt(db, chat_id=payload.chat_id, user_id=user_id)
+    if not receipt:
+        last_delivered = payload.message_id if payload.status in {"message_delivered", "message_read"} else None
+        last_read = payload.message_id if payload.status == "message_read" else None
+        receipt = await repository.create_message_receipt(
+            db,
+            chat_id=payload.chat_id,
+            user_id=user_id,
+            last_delivered_message_id=last_delivered,
+            last_read_message_id=last_read,
+        )
+    else:
+        if payload.status in {"message_delivered", "message_read"}:
+            current = receipt.last_delivered_message_id or 0
+            receipt.last_delivered_message_id = max(current, payload.message_id)
+        if payload.status == "message_read":
+            current_read = receipt.last_read_message_id or 0
+            receipt.last_read_message_id = max(current_read, payload.message_id)
+
+    await db.commit()
+    await db.refresh(receipt)
+    return {
+        "chat_id": payload.chat_id,
+        "message_id": payload.message_id,
+        "last_delivered_message_id": receipt.last_delivered_message_id or 0,
+        "last_read_message_id": receipt.last_read_message_id or 0,
+    }
diff --git a/app/realtime/schemas.py b/app/realtime/schemas.py
index 8edbdaf..d4f1790 100644
--- a/app/realtime/schemas.py
+++ b/app/realtime/schemas.py
@@ -24,6 +24,7 @@ class SendMessagePayload(BaseModel):
     type: MessageType = MessageType.TEXT
     text: str | None = Field(default=None, max_length=4096)
     temp_id: str | None = None
+    client_message_id: str | None = Field(default=None, min_length=8, max_length=64)
 
 
 class ChatEventPayload(BaseModel):
diff --git a/app/realtime/service.py b/app/realtime/service.py
index 6c041db..ce3ed8a 100644
--- a/app/realtime/service.py
+++ b/app/realtime/service.py
@@ -9,8 +9,8 @@ from sqlalchemy.ext.asyncio import AsyncSession
 
 from app.chats.repository import list_user_chat_ids
 from app.chats.service import ensure_chat_membership
-from app.messages.schemas import MessageCreateRequest, MessageRead
-from app.messages.service import create_chat_message
+from app.messages.schemas import MessageCreateRequest, MessageRead, MessageStatusUpdateRequest
+from app.messages.service import create_chat_message, mark_message_status
 from app.realtime.models import ConnectionContext
 from app.realtime.presence import mark_user_offline, mark_user_online
 from app.realtime.repository import RedisRealtimeRepository
@@ -81,9 +81,19 @@ class RealtimeGateway:
         message = await create_chat_message(
             db,
             sender_id=user_id,
-            payload=MessageCreateRequest(chat_id=payload.chat_id, type=payload.type, text=payload.text),
+            payload=MessageCreateRequest(
+                chat_id=payload.chat_id,
+                type=payload.type,
+                text=payload.text,
+                client_message_id=payload.client_message_id or payload.temp_id,
+            ),
+        )
+        await self.publish_message_created(
+            message=message,
+            sender_id=user_id,
+            temp_id=payload.temp_id,
+            client_message_id=payload.client_message_id,
         )
-        await self.publish_message_created(message=message, sender_id=user_id, temp_id=payload.temp_id)
 
     async def handle_typing_event(self, db: AsyncSession, user_id: int, payload: ChatEventPayload, event: str) -> None:
         await ensure_chat_membership(db, chat_id=payload.chat_id, user_id=user_id)
@@ -99,8 +109,12 @@ class RealtimeGateway:
         user_id: int,
         payload: MessageStatusPayload,
         event: str,
-    ) -> None:
-        await ensure_chat_membership(db, chat_id=payload.chat_id, user_id=user_id)
+    ) -> dict[str, int]:
+        receipt_state = await mark_message_status(
+            db,
+            user_id=user_id,
+            payload=MessageStatusUpdateRequest(chat_id=payload.chat_id, message_id=payload.message_id, status=event),
+        )
         await self._publish_chat_event(
             payload.chat_id,
             event=event,
@@ -108,8 +122,11 @@ class RealtimeGateway:
                 "chat_id": payload.chat_id,
                 "message_id": payload.message_id,
                 "user_id": user_id,
+                "last_delivered_message_id": receipt_state["last_delivered_message_id"],
+                "last_read_message_id": receipt_state["last_read_message_id"],
             },
         )
+        return receipt_state
 
     async def load_user_chat_ids(self, db: AsyncSession, user_id: int) -> list[int]:
         return await list_user_chat_ids(db, user_id=user_id)
@@ -139,7 +156,14 @@ class RealtimeGateway:
             return
         await self._handle_redis_event(f"chat:{chat_id}", event_payload)
 
-    async def publish_message_created(self, *, message, sender_id: int, temp_id: str | None = None) -> None:
+    async def publish_message_created(
+        self,
+        *,
+        message,
+        sender_id: int,
+        temp_id: str | None = None,
+        client_message_id: str | None = None,
+    ) -> None:
         message_data = MessageRead.model_validate(message).model_dump(mode="json")
         await self._publish_chat_event(
             message.chat_id,
@@ -148,6 +172,7 @@ class RealtimeGateway:
                 "chat_id": message.chat_id,
                 "message": message_data,
                 "temp_id": temp_id,
+                "client_message_id": client_message_id,
                 "sender_id": sender_id,
             },
         )
diff --git a/web/src/api/chats.ts b/web/src/api/chats.ts
index 2dd5f53..fdcd38d 100644
--- a/web/src/api/chats.ts
+++ b/web/src/api/chats.ts
@@ -35,6 +35,21 @@ export async function sendMessage(chatId: number, text: string, type: MessageTyp
   return data;
 }
 
+export async function sendMessageWithClientId(
+  chatId: number,
+  text: string,
+  type: MessageType,
+  clientMessageId: string
+): Promise<Message> {
+  const { data } = await http.post<Message>("/messages", {
+    chat_id: chatId,
+    text,
+    type,
+    client_message_id: clientMessageId
+  });
+  return data;
+}
+
 export interface UploadUrlResponse {
   upload_url: string;
   file_url: string;
@@ -77,3 +92,15 @@ export async function attachFile(messageId: number, fileUrl: string, fileType: s
     file_size: fileSize
   });
 }
+
+export async function updateMessageStatus(
+  chatId: number,
+  messageId: number,
+  status: "message_delivered" | "message_read"
+): Promise<void> {
+  await http.post("/messages/status", {
+    chat_id: chatId,
+    message_id: messageId,
+    status
+  });
+}
diff --git a/web/src/components/MessageComposer.tsx b/web/src/components/MessageComposer.tsx
index 5894953..96465f3 100644
--- a/web/src/components/MessageComposer.tsx
+++ b/web/src/components/MessageComposer.tsx
@@ -1,5 +1,5 @@
 import { useEffect, useRef, useState } from "react";
-import { attachFile, requestUploadUrl, sendMessage, uploadToPresignedUrl } from "../api/chats";
+import { attachFile, requestUploadUrl, sendMessageWithClientId, uploadToPresignedUrl } from "../api/chats";
 import { useAuthStore } from "../store/authStore";
 import { useChatStore } from "../store/chatStore";
 import { buildWsUrl } from "../utils/ws";
@@ -28,6 +28,13 @@ export function MessageComposer() {
     };
   }, [previewUrl]);
 
+  function makeClientMessageId(): string {
+    if (typeof crypto !== "undefined" && "randomUUID" in crypto) {
+      return crypto.randomUUID();
+    }
+    return `msg-${Date.now()}-${Math.random().toString(16).slice(2)}`;
+  }
+
   function getWs(): WebSocket | null {
     if (!accessToken || !activeChatId) {
       return null;
@@ -44,7 +51,7 @@ export function MessageComposer() {
     if (!activeChatId || !text.trim()) {
       return;
     }
-    const message = await sendMessage(activeChatId, text.trim(), "text");
+    const message = await sendMessageWithClientId(activeChatId, text.trim(), "text", makeClientMessageId());
     prependMessage(activeChatId, message);
     setText("");
     const ws = getWs();
@@ -61,7 +68,7 @@ export function MessageComposer() {
     try {
       const upload = await requestUploadUrl(file);
       await uploadToPresignedUrl(upload.upload_url, upload.required_headers, file, setUploadProgress);
-      const message = await sendMessage(activeChatId, upload.file_url, messageType);
+      const message = await sendMessageWithClientId(activeChatId, upload.file_url, messageType, makeClientMessageId());
       await attachFile(message.id, upload.file_url, file.type || "application/octet-stream", file.size);
       prependMessage(activeChatId, message);
     } catch {
diff --git a/web/src/hooks/useRealtime.ts b/web/src/hooks/useRealtime.ts
index 0fb830a..f709912 100644
--- a/web/src/hooks/useRealtime.ts
+++ b/web/src/hooks/useRealtime.ts
@@ -16,6 +16,7 @@ export function useRealtime() {
   const prependMessage = useChatStore((s) => s.prependMessage);
   const loadChats = useChatStore((s) => s.loadChats);
   const chats = useChatStore((s) => s.chats);
+  const activeChatId = useChatStore((s) => s.activeChatId);
   const typingByChat = useRef<Record<number, Set<number>>>({});
 
   const wsUrl = useMemo(() => {
@@ -34,6 +35,12 @@ export function useRealtime() {
         const chatId = Number(event.payload.chat_id);
         const message = event.payload.message as Message;
         prependMessage(chatId, message);
+        if (message.sender_id !== me?.id) {
+          ws.send(JSON.stringify({ event: "message_delivered", payload: { chat_id: chatId, message_id: message.id } }));
+          if (chatId === activeChatId) {
+            ws.send(JSON.stringify({ event: "message_read", payload: { chat_id: chatId, message_id: message.id } }));
+          }
+        }
         if (!chats.some((chat) => chat.id === chatId)) {
           void loadChats();
         }
@@ -59,7 +66,7 @@ export function useRealtime() {
     };
 
     return () => ws.close();
-  }, [wsUrl, prependMessage, loadChats, chats, me?.id]);
+  }, [wsUrl, prependMessage, loadChats, chats, me?.id, activeChatId]);
 
   return null;
 }
diff --git a/web/src/store/chatStore.ts b/web/src/store/chatStore.ts
index 0cfb0dd..544a68b 100644
--- a/web/src/store/chatStore.ts
+++ b/web/src/store/chatStore.ts
@@ -1,5 +1,5 @@
 import { create } from "zustand";
-import { getChats, getMessages } from "../api/chats";
+import { getChats, getMessages, updateMessageStatus } from "../api/chats";
 import type { Chat, Message } from "../chat/types";
 
 interface ChatState {
@@ -26,12 +26,17 @@ export const useChatStore = create<ChatState>((set, get) => ({
   setActiveChatId: (chatId) => set({ activeChatId: chatId }),
   loadMessages: async (chatId) => {
     const messages = await getMessages(chatId);
+    const sorted = [...messages].reverse();
     set((state) => ({
       messagesByChat: {
         ...state.messagesByChat,
-        [chatId]: [...messages].reverse()
+        [chatId]: sorted
       }
     }));
+    const lastMessage = sorted[sorted.length - 1];
+    if (lastMessage) {
+      void updateMessageStatus(chatId, lastMessage.id, "message_read");
+    }
   },
   prependMessage: (chatId, message) => {
     const old = get().messagesByChat[chatId] ?? [];