fix(frontend): prevent chat message loss during websocket disconnections or page refresh (#13380)

enterprise/migrations/versions/101_add_pending_messages_table.py

@@ -0,0 +1,39 @@
+"""Add pending_messages table for server-side message queuing
+
+Revision ID: 101
+Revises: 100
+Create Date: 2025-03-15 00:00:00.000000
+
+"""
+
+from typing import Sequence, Union
+
+import sqlalchemy as sa
+from alembic import op
+
+# revision identifiers, used by Alembic.
+revision: str = '101'
+down_revision: Union[str, None] = '100'
+branch_labels: Union[str, Sequence[str], None] = None
+depends_on: Union[str, Sequence[str], None] = None
+
+
+def upgrade() -> None:
+    """Create pending_messages table for storing messages before conversation is ready.
+
+    Messages are stored temporarily until the conversation becomes ready, then
+    delivered and deleted regardless of success or failure.
+    """
+    op.create_table(
+        'pending_messages',
+        sa.Column('id', sa.String(), primary_key=True),
+        sa.Column('conversation_id', sa.String(), nullable=False, index=True),
+        sa.Column('role', sa.String(20), nullable=False, server_default='user'),
+        sa.Column('content', sa.JSON, nullable=False),
+        sa.Column('created_at', sa.DateTime(timezone=True), nullable=False),
+    )
+
+
+def downgrade() -> None:
+    """Remove pending_messages table."""
+    op.drop_table('pending_messages')

enterprise/server/utils/saas_pending_message_injector.py

@@ -0,0 +1,172 @@
+"""Enterprise injector for PendingMessageService with SAAS filtering."""
+
+from typing import AsyncGenerator
+from uuid import UUID
+
+from fastapi import Request
+from sqlalchemy import select
+from storage.stored_conversation_metadata_saas import StoredConversationMetadataSaas
+from storage.user import User
+
+from openhands.agent_server.models import ImageContent, TextContent
+from openhands.app_server.errors import AuthError
+from openhands.app_server.pending_messages.pending_message_models import (
+    PendingMessageResponse,
+)
+from openhands.app_server.pending_messages.pending_message_service import (
+    PendingMessageService,
+    PendingMessageServiceInjector,
+    SQLPendingMessageService,
+)
+from openhands.app_server.services.injector import InjectorState
+from openhands.app_server.user.specifiy_user_context import ADMIN
+from openhands.app_server.user.user_context import UserContext
+
+
+class SaasSQLPendingMessageService(SQLPendingMessageService):
+    """Extended SQLPendingMessageService with user and organization-based filtering.
+
+    This enterprise version ensures that:
+    - Users can only queue messages for conversations they own
+    - Organization isolation is enforced for multi-tenant deployments
+    """
+
+    def __init__(self, db_session, user_context: UserContext):
+        super().__init__(db_session=db_session)
+        self.user_context = user_context
+
+    async def _get_current_user(self) -> User | None:
+        """Get the current user using the existing db_session.
+
+        Returns:
+            User object or None if no user_id is available
+        """
+        user_id_str = await self.user_context.get_user_id()
+        if not user_id_str:
+            return None
+
+        user_id_uuid = UUID(user_id_str)
+        result = await self.db_session.execute(
+            select(User).where(User.id == user_id_uuid)
+        )
+        return result.scalars().first()
+
+    async def _validate_conversation_ownership(self, conversation_id: str) -> None:
+        """Validate that the current user owns the conversation.
+
+        This ensures multi-tenant isolation by checking:
+        - The conversation belongs to the current user
+        - The conversation belongs to the user's current organization
+
+        Args:
+            conversation_id: The conversation ID to validate (can be task-id or UUID)
+
+        Raises:
+            AuthError: If user doesn't own the conversation or authentication fails
+        """
+        # For internal operations (e.g., processing pending messages during startup)
+        # we need a mode that bypasses filtering. The ADMIN context enables this.
+        if self.user_context == ADMIN:
+            return
+
+        user_id_str = await self.user_context.get_user_id()
+        if not user_id_str:
+            raise AuthError('User authentication required')
+
+        user_id_uuid = UUID(user_id_str)
+
+        # Check conversation ownership via SAAS metadata
+        query = select(StoredConversationMetadataSaas).where(
+            StoredConversationMetadataSaas.conversation_id == conversation_id
+        )
+        result = await self.db_session.execute(query)
+        saas_metadata = result.scalar_one_or_none()
+
+        # If no SAAS metadata exists, the conversation might be a new task-id
+        # that hasn't been linked to a conversation yet. Allow access in this case
+        # as the message will be validated when the conversation is created.
+        if saas_metadata is None:
+            return
+
+        # Verify user ownership
+        if saas_metadata.user_id != user_id_uuid:
+            raise AuthError('You do not have access to this conversation')
+
+        # Verify organization ownership if applicable
+        user = await self._get_current_user()
+        if user and user.current_org_id is not None:
+            if saas_metadata.org_id != user.current_org_id:
+                raise AuthError('Conversation belongs to a different organization')
+
+    async def add_message(
+        self,
+        conversation_id: str,
+        content: list[TextContent | ImageContent],
+        role: str = 'user',
+    ) -> PendingMessageResponse:
+        """Queue a message with ownership validation.
+
+        Args:
+            conversation_id: The conversation ID to queue the message for
+            content: Message content
+            role: Message role (default: 'user')
+
+        Returns:
+            PendingMessageResponse with the queued message info
+
+        Raises:
+            AuthError: If user doesn't own the conversation
+        """
+        await self._validate_conversation_ownership(conversation_id)
+        return await super().add_message(conversation_id, content, role)
+
+    async def get_pending_messages(self, conversation_id: str):
+        """Get pending messages with ownership validation.
+
+        Args:
+            conversation_id: The conversation ID to get messages for
+
+        Returns:
+            List of pending messages
+
+        Raises:
+            AuthError: If user doesn't own the conversation
+        """
+        await self._validate_conversation_ownership(conversation_id)
+        return await super().get_pending_messages(conversation_id)
+
+    async def count_pending_messages(self, conversation_id: str) -> int:
+        """Count pending messages with ownership validation.
+
+        Args:
+            conversation_id: The conversation ID to count messages for
+
+        Returns:
+            Number of pending messages
+
+        Raises:
+            AuthError: If user doesn't own the conversation
+        """
+        await self._validate_conversation_ownership(conversation_id)
+        return await super().count_pending_messages(conversation_id)
+
+
+class SaasPendingMessageServiceInjector(PendingMessageServiceInjector):
+    """Enterprise injector for PendingMessageService with SAAS filtering."""
+
+    async def inject(
+        self, state: InjectorState, request: Request | None = None
+    ) -> AsyncGenerator[PendingMessageService, None]:
+        from openhands.app_server.config import (
+            get_db_session,
+            get_user_context,
+        )
+
+        async with (
+            get_user_context(state, request) as user_context,
+            get_db_session(state, request) as db_session,
+        ):
+            service = SaasSQLPendingMessageService(
+                db_session=db_session, user_context=user_context
+            )
+            yield service

frontend/__tests__/components/interactive-chat-box.test.tsx

@@ -198,9 +198,9 @@ describe("InteractiveChatBox", () => {
     expect(onSubmitMock).toHaveBeenCalledWith("Hello, world!", [], []);
   });
 
-  it("should disable the submit button when agent is loading", async () => {
+  it("should disable the submit button when awaiting user confirmation", async () => {
     const user = userEvent.setup();
-    mockStores(AgentState.LOADING);
+    mockStores(AgentState.AWAITING_USER_CONFIRMATION);
 
     renderInteractiveChatBox({
       onSubmit: onSubmitMock,

frontend/__tests__/conversation-local-storage.test.ts

@@ -229,4 +229,231 @@ describe("conversation localStorage utilities", () => {
       expect(parsed.subConversationTaskId).toBeNull();
     });
   });
+
+  describe("draftMessage persistence", () => {
+    describe("getConversationState", () => {
+      it("returns default draftMessage as null when no state exists", () => {
+        // Arrange
+        const conversationId = "conv-draft-1";
+
+        // Act
+        const state = getConversationState(conversationId);
+
+        // Assert
+        expect(state.draftMessage).toBeNull();
+      });
+
+      it("retrieves draftMessage from localStorage when it exists", () => {
+        // Arrange
+        const conversationId = "conv-draft-2";
+        const draftText = "This is my saved draft message";
+        const consolidatedKey = `${LOCAL_STORAGE_KEYS.CONVERSATION_STATE}-${conversationId}`;
+
+        localStorage.setItem(
+          consolidatedKey,
+          JSON.stringify({
+            draftMessage: draftText,
+          }),
+        );
+
+        // Act
+        const state = getConversationState(conversationId);
+
+        // Assert
+        expect(state.draftMessage).toBe(draftText);
+      });
+
+      it("returns null draftMessage for task conversation IDs (not persisted)", () => {
+        // Arrange
+        const taskId = "task-uuid-123";
+        const consolidatedKey = `${LOCAL_STORAGE_KEYS.CONVERSATION_STATE}-${taskId}`;
+
+        // Even if somehow there's data in localStorage for a task ID
+        localStorage.setItem(
+          consolidatedKey,
+          JSON.stringify({
+            draftMessage: "Should not be returned",
+          }),
+        );
+
+        // Act
+        const state = getConversationState(taskId);
+
+        // Assert - should return default state, not the stored value
+        expect(state.draftMessage).toBeNull();
+      });
+    });
+
+    describe("setConversationState", () => {
+      it("persists draftMessage to localStorage", () => {
+        // Arrange
+        const conversationId = "conv-draft-3";
+        const draftText = "New draft message to save";
+        const consolidatedKey = `${LOCAL_STORAGE_KEYS.CONVERSATION_STATE}-${conversationId}`;
+
+        // Act
+        setConversationState(conversationId, {
+          draftMessage: draftText,
+        });
+
+        // Assert
+        const stored = localStorage.getItem(consolidatedKey);
+        expect(stored).not.toBeNull();
+        const parsed = JSON.parse(stored!);
+        expect(parsed.draftMessage).toBe(draftText);
+      });
+
+      it("does not persist draftMessage for task conversation IDs", () => {
+        // Arrange
+        const taskId = "task-draft-xyz";
+        const consolidatedKey = `${LOCAL_STORAGE_KEYS.CONVERSATION_STATE}-${taskId}`;
+
+        // Act
+        setConversationState(taskId, {
+          draftMessage: "Draft for task ID",
+        });
+
+        // Assert - nothing should be stored
+        expect(localStorage.getItem(consolidatedKey)).toBeNull();
+      });
+
+      it("merges draftMessage with existing state without overwriting other fields", () => {
+        // Arrange
+        const conversationId = "conv-draft-4";
+        const consolidatedKey = `${LOCAL_STORAGE_KEYS.CONVERSATION_STATE}-${conversationId}`;
+
+        localStorage.setItem(
+          consolidatedKey,
+          JSON.stringify({
+            selectedTab: "terminal",
+            rightPanelShown: false,
+            unpinnedTabs: ["tab-1", "tab-2"],
+            conversationMode: "plan",
+            subConversationTaskId: "task-123",
+          }),
+        );
+
+        // Act
+        setConversationState(conversationId, {
+          draftMessage: "Updated draft",
+        });
+
+        // Assert
+        const stored = localStorage.getItem(consolidatedKey);
+        const parsed = JSON.parse(stored!);
+
+        expect(parsed.draftMessage).toBe("Updated draft");
+        expect(parsed.selectedTab).toBe("terminal");
+        expect(parsed.rightPanelShown).toBe(false);
+        expect(parsed.unpinnedTabs).toEqual(["tab-1", "tab-2"]);
+        expect(parsed.conversationMode).toBe("plan");
+        expect(parsed.subConversationTaskId).toBe("task-123");
+      });
+
+      it("clears draftMessage when set to null", () => {
+        // Arrange
+        const conversationId = "conv-draft-5";
+        const consolidatedKey = `${LOCAL_STORAGE_KEYS.CONVERSATION_STATE}-${conversationId}`;
+
+        localStorage.setItem(
+          consolidatedKey,
+          JSON.stringify({
+            draftMessage: "Existing draft",
+          }),
+        );
+
+        // Act
+        setConversationState(conversationId, {
+          draftMessage: null,
+        });
+
+        // Assert
+        const stored = localStorage.getItem(consolidatedKey);
+        const parsed = JSON.parse(stored!);
+        expect(parsed.draftMessage).toBeNull();
+      });
+
+      it("clears draftMessage when set to empty string (stored as empty string)", () => {
+        // Arrange
+        const conversationId = "conv-draft-6";
+        const consolidatedKey = `${LOCAL_STORAGE_KEYS.CONVERSATION_STATE}-${conversationId}`;
+
+        localStorage.setItem(
+          consolidatedKey,
+          JSON.stringify({
+            draftMessage: "Existing draft",
+          }),
+        );
+
+        // Act
+        setConversationState(conversationId, {
+          draftMessage: "",
+        });
+
+        // Assert
+        const stored = localStorage.getItem(consolidatedKey);
+        const parsed = JSON.parse(stored!);
+        expect(parsed.draftMessage).toBe("");
+      });
+    });
+
+    describe("conversation-specific draft isolation", () => {
+      it("stores drafts separately for different conversations", () => {
+        // Arrange
+        const convA = "conv-A";
+        const convB = "conv-B";
+        const draftA = "Draft for conversation A";
+        const draftB = "Draft for conversation B";
+
+        // Act
+        setConversationState(convA, { draftMessage: draftA });
+        setConversationState(convB, { draftMessage: draftB });
+
+        // Assert
+        const stateA = getConversationState(convA);
+        const stateB = getConversationState(convB);
+
+        expect(stateA.draftMessage).toBe(draftA);
+        expect(stateB.draftMessage).toBe(draftB);
+      });
+
+      it("updating one conversation draft does not affect another", () => {
+        // Arrange
+        const convA = "conv-isolated-A";
+        const convB = "conv-isolated-B";
+
+        setConversationState(convA, { draftMessage: "Original draft A" });
+        setConversationState(convB, { draftMessage: "Original draft B" });
+
+        // Act - update only conversation A
+        setConversationState(convA, { draftMessage: "Updated draft A" });
+
+        // Assert - conversation B should be unchanged
+        const stateA = getConversationState(convA);
+        const stateB = getConversationState(convB);
+
+        expect(stateA.draftMessage).toBe("Updated draft A");
+        expect(stateB.draftMessage).toBe("Original draft B");
+      });
+
+      it("clearing one conversation draft does not affect another", () => {
+        // Arrange
+        const convA = "conv-clear-A";
+        const convB = "conv-clear-B";
+
+        setConversationState(convA, { draftMessage: "Draft A" });
+        setConversationState(convB, { draftMessage: "Draft B" });
+
+        // Act - clear draft for conversation A
+        setConversationState(convA, { draftMessage: null });
+
+        // Assert
+        const stateA = getConversationState(convA);
+        const stateB = getConversationState(convB);
+
+        expect(stateA.draftMessage).toBeNull();
+        expect(stateB.draftMessage).toBe("Draft B");
+      });
+    });
+  });
 });

frontend/__tests__/conversation-websocket-handler.test.tsx

@@ -1,3 +1,4 @@
+import React from "react";
 import {
   describe,
   it,
@@ -8,7 +9,7 @@ import {
   afterEach,
   vi,
 } from "vitest";
-import { screen, waitFor, render, cleanup } from "@testing-library/react";
+import { screen, waitFor, render, cleanup, act } from "@testing-library/react";
 import { QueryClient, QueryClientProvider } from "@tanstack/react-query";
 import { http, HttpResponse } from "msw";
 import { MemoryRouter, Route, Routes } from "react-router";
@@ -682,8 +683,242 @@ describe("Conversation WebSocket Handler", () => {
 
   // 7. Message Sending Tests
   describe("Message Sending", () => {
-    it.todo("should send user actions through WebSocket when connected");
-    it.todo("should handle send attempts when disconnected");
+    it("should send user actions through WebSocket when connected", async () => {
+      // Arrange
+      const conversationId = "test-conversation-send";
+      let receivedMessage: unknown = null;
+
+      // Set up MSW to capture sent messages
+      mswServer.use(
+        wsLink.addEventListener("connection", ({ client, server }) => {
+          server.connect();
+
+          // Capture messages sent from client
+          client.addEventListener("message", (event) => {
+            receivedMessage = JSON.parse(event.data as string);
+          });
+        }),
+      );
+
+      // Create ref to store sendMessage function
+      let sendMessageFn: typeof useConversationWebSocket extends () => infer R
+        ? R extends { sendMessage: infer S }
+          ? S
+          : null
+        : null = null;
+
+      function TestComponent() {
+        const context = useConversationWebSocket();
+
+        React.useEffect(() => {
+          if (context?.sendMessage) {
+            sendMessageFn = context.sendMessage;
+          }
+        }, [context?.sendMessage]);
+
+        return (
+          <div>
+            <div data-testid="connection-state">
+              {context?.connectionState || "NOT_AVAILABLE"}
+            </div>
+          </div>
+        );
+      }
+
+      // Act
+      renderWithWebSocketContext(
+        <TestComponent />,
+        conversationId,
+        `http://localhost:3000/api/conversations/${conversationId}`,
+      );
+
+      // Wait for connection
+      await waitFor(() => {
+        expect(screen.getByTestId("connection-state")).toHaveTextContent(
+          "OPEN",
+        );
+      });
+
+      // Send a message
+      await waitFor(() => {
+        expect(sendMessageFn).not.toBeNull();
+      });
+
+      await act(async () => {
+        await sendMessageFn!({
+          role: "user",
+          content: [{ type: "text", text: "Hello from test" }],
+        });
+      });
+
+      // Assert - message should have been received by mock server
+      await waitFor(() => {
+        expect(receivedMessage).toEqual({
+          role: "user",
+          content: [{ type: "text", text: "Hello from test" }],
+        });
+      });
+    });
+
+    it("should not throw error when sendMessage is called with WebSocket connected", async () => {
+      // This test verifies that sendMessage doesn't throw an error
+      // when the WebSocket is connected.
+      const conversationId = "test-conversation-no-throw";
+      let sendError: Error | null = null;
+
+      // Set up MSW to connect and receive messages
+      mswServer.use(
+        wsLink.addEventListener("connection", ({ server }) => {
+          server.connect();
+        }),
+      );
+
+      // Create ref to store sendMessage function
+      let sendMessageFn: typeof useConversationWebSocket extends () => infer R
+        ? R extends { sendMessage: infer S }
+          ? S
+          : null
+        : null = null;
+
+      function TestComponent() {
+        const context = useConversationWebSocket();
+
+        React.useEffect(() => {
+          if (context?.sendMessage) {
+            sendMessageFn = context.sendMessage;
+          }
+        }, [context?.sendMessage]);
+
+        return (
+          <div>
+            <div data-testid="connection-state">
+              {context?.connectionState || "NOT_AVAILABLE"}
+            </div>
+          </div>
+        );
+      }
+
+      // Act
+      renderWithWebSocketContext(
+        <TestComponent />,
+        conversationId,
+        `http://localhost:3000/api/conversations/${conversationId}`,
+      );
+
+      // Wait for connection
+      await waitFor(() => {
+        expect(screen.getByTestId("connection-state")).toHaveTextContent(
+          "OPEN",
+        );
+      });
+
+      // Wait for the context to be available
+      await waitFor(() => {
+        expect(sendMessageFn).not.toBeNull();
+      });
+
+      // Try to send a message
+      await act(async () => {
+        try {
+          await sendMessageFn!({
+            role: "user",
+            content: [{ type: "text", text: "Test message" }],
+          });
+        } catch (error) {
+          sendError = error as Error;
+        }
+      });
+
+      // Assert - should NOT throw an error
+      expect(sendError).toBeNull();
+    });
+
+    it("should send multiple messages through WebSocket in order", async () => {
+      // Arrange
+      const conversationId = "test-conversation-multi";
+      const receivedMessages: unknown[] = [];
+
+      // Set up MSW to capture sent messages
+      mswServer.use(
+        wsLink.addEventListener("connection", ({ client, server }) => {
+          server.connect();
+
+          // Capture messages sent from client
+          client.addEventListener("message", (event) => {
+            receivedMessages.push(JSON.parse(event.data as string));
+          });
+        }),
+      );
+
+      // Create ref to store sendMessage function
+      let sendMessageFn: typeof useConversationWebSocket extends () => infer R
+        ? R extends { sendMessage: infer S }
+          ? S
+          : null
+        : null = null;
+
+      function TestComponent() {
+        const context = useConversationWebSocket();
+
+        React.useEffect(() => {
+          if (context?.sendMessage) {
+            sendMessageFn = context.sendMessage;
+          }
+        }, [context?.sendMessage]);
+
+        return (
+          <div>
+            <div data-testid="connection-state">
+              {context?.connectionState || "NOT_AVAILABLE"}
+            </div>
+          </div>
+        );
+      }
+
+      // Act
+      renderWithWebSocketContext(
+        <TestComponent />,
+        conversationId,
+        `http://localhost:3000/api/conversations/${conversationId}`,
+      );
+
+      // Wait for connection
+      await waitFor(() => {
+        expect(screen.getByTestId("connection-state")).toHaveTextContent(
+          "OPEN",
+        );
+      });
+
+      await waitFor(() => {
+        expect(sendMessageFn).not.toBeNull();
+      });
+
+      // Send multiple messages
+      await act(async () => {
+        await sendMessageFn!({
+          role: "user",
+          content: [{ type: "text", text: "Message 1" }],
+        });
+        await sendMessageFn!({
+          role: "user",
+          content: [{ type: "text", text: "Message 2" }],
+        });
+      });
+
+      // Assert - both messages should have been received in order
+      await waitFor(() => {
+        expect(receivedMessages.length).toBe(2);
+      });
+
+      expect(receivedMessages[0]).toEqual({
+        role: "user",
+        content: [{ type: "text", text: "Message 1" }],
+      });
+      expect(receivedMessages[1]).toEqual({
+        role: "user",
+        content: [{ type: "text", text: "Message 2" }],
+      });
+    });
   });
 
   // 8. History Loading State Tests

frontend/__tests__/hooks/use-draft-persistence.test.tsx

@@ -0,0 +1,594 @@
+import { describe, it, expect, vi, beforeEach, afterEach } from "vitest";
+import { renderHook, act } from "@testing-library/react";
+import { useDraftPersistence } from "#/hooks/chat/use-draft-persistence";
+import * as conversationLocalStorage from "#/utils/conversation-local-storage";
+
+// Mock the entire module
+vi.mock("#/utils/conversation-local-storage", () => ({
+  useConversationLocalStorageState: vi.fn(),
+  getConversationState: vi.fn(),
+  setConversationState: vi.fn(),
+}));
+
+// Mock the getTextContent utility
+vi.mock("#/components/features/chat/utils/chat-input.utils", () => ({
+  getTextContent: vi.fn((el: HTMLDivElement | null) => el?.textContent || ""),
+}));
+
+describe("useDraftPersistence", () => {
+  let mockSetDraftMessage: (message: string | null) => void;
+
+  // Create a mock ref to contentEditable div
+  const createMockChatInputRef = (initialContent = "") => {
+    const div = document.createElement("div");
+    div.setAttribute("contenteditable", "true");
+    div.textContent = initialContent;
+    return { current: div };
+  };
+
+  beforeEach(() => {
+    vi.clearAllMocks();
+    vi.useFakeTimers();
+    localStorage.clear();
+
+    mockSetDraftMessage = vi.fn<(message: string | null) => void>();
+
+    // Default mock for useConversationLocalStorageState
+    vi.mocked(conversationLocalStorage.useConversationLocalStorageState).mockReturnValue({
+      state: {
+        selectedTab: "editor",
+        rightPanelShown: true,
+        unpinnedTabs: [],
+        conversationMode: "code",
+        subConversationTaskId: null,
+        draftMessage: null,
+      },
+      setSelectedTab: vi.fn(),
+      setRightPanelShown: vi.fn(),
+      setUnpinnedTabs: vi.fn(),
+      setConversationMode: vi.fn(),
+      setDraftMessage: mockSetDraftMessage,
+    });
+
+    // Default mock for getConversationState
+    vi.mocked(conversationLocalStorage.getConversationState).mockReturnValue({
+      selectedTab: "editor",
+      rightPanelShown: true,
+      unpinnedTabs: [],
+      conversationMode: "code",
+      subConversationTaskId: null,
+      draftMessage: null,
+    });
+  });
+
+  afterEach(() => {
+    vi.useRealTimers();
+    vi.clearAllMocks();
+  });
+
+  describe("draft restoration on mount", () => {
+    it("restores draft from localStorage when mounting with existing draft", () => {
+      // Arrange
+      const conversationId = "conv-restore-1";
+      const savedDraft = "Previously saved draft message";
+      const chatInputRef = createMockChatInputRef();
+
+      vi.mocked(conversationLocalStorage.getConversationState).mockReturnValue({
+        selectedTab: "editor",
+        rightPanelShown: true,
+        unpinnedTabs: [],
+        conversationMode: "code",
+        subConversationTaskId: null,
+        draftMessage: savedDraft,
+      });
+
+      // Act
+      renderHook(() => useDraftPersistence(conversationId, chatInputRef));
+
+      // Assert - draft should be restored to the DOM element
+      expect(chatInputRef.current?.textContent).toBe(savedDraft);
+    });
+
+    it("clears input on mount then restores draft if exists", () => {
+      // Arrange
+      const conversationId = "conv-restore-2";
+      const existingContent = "Stale content from previous conversation";
+      const savedDraft = "Saved draft";
+      const chatInputRef = createMockChatInputRef(existingContent);
+
+      vi.mocked(conversationLocalStorage.getConversationState).mockReturnValue({
+        selectedTab: "editor",
+        rightPanelShown: true,
+        unpinnedTabs: [],
+        conversationMode: "code",
+        subConversationTaskId: null,
+        draftMessage: savedDraft,
+      });
+
+      // Act
+      renderHook(() => useDraftPersistence(conversationId, chatInputRef));
+
+      // Assert - input cleared then draft restored
+      expect(chatInputRef.current?.textContent).toBe(savedDraft);
+    });
+
+    it("clears input when no draft exists for conversation", () => {
+      // Arrange
+      const conversationId = "conv-no-draft";
+      const chatInputRef = createMockChatInputRef("Some stale content");
+
+      vi.mocked(conversationLocalStorage.getConversationState).mockReturnValue({
+        selectedTab: "editor",
+        rightPanelShown: true,
+        unpinnedTabs: [],
+        conversationMode: "code",
+        subConversationTaskId: null,
+        draftMessage: null,
+      });
+
+      // Act
+      renderHook(() => useDraftPersistence(conversationId, chatInputRef));
+
+      // Assert - content should be cleared since there's no draft
+      expect(chatInputRef.current?.textContent).toBe("");
+    });
+  });
+
+  describe("debounced saving", () => {
+    it("saves draft after debounce period", () => {
+      // Arrange
+      const conversationId = "conv-debounce-1";
+      const chatInputRef = createMockChatInputRef();
+
+      const { result } = renderHook(() =>
+        useDraftPersistence(conversationId, chatInputRef),
+      );
+
+      // Act - simulate user typing
+      chatInputRef.current!.textContent = "New draft content";
+      act(() => {
+        result.current.saveDraft();
+      });
+
+      // Assert - should not save immediately
+      expect(mockSetDraftMessage).not.toHaveBeenCalled();
+
+      // Fast forward past debounce period (500ms)
+      act(() => {
+        vi.advanceTimersByTime(500);
+      });
+
+      // Assert - should save after debounce
+      expect(mockSetDraftMessage).toHaveBeenCalledWith("New draft content");
+    });
+
+    it("cancels pending save when new input arrives before debounce", () => {
+      // Arrange
+      const conversationId = "conv-debounce-2";
+      const chatInputRef = createMockChatInputRef();
+
+      const { result } = renderHook(() =>
+        useDraftPersistence(conversationId, chatInputRef),
+      );
+
+      // Act - first input
+      chatInputRef.current!.textContent = "First";
+      act(() => {
+        result.current.saveDraft();
+      });
+
+      // Wait 200ms (less than debounce)
+      act(() => {
+        vi.advanceTimersByTime(200);
+      });
+
+      // Second input before debounce completes
+      chatInputRef.current!.textContent = "First Second";
+      act(() => {
+        result.current.saveDraft();
+      });
+
+      // Complete the second debounce
+      act(() => {
+        vi.advanceTimersByTime(500);
+      });
+
+      // Assert - should only save the final value once
+      expect(mockSetDraftMessage).toHaveBeenCalledTimes(1);
+      expect(mockSetDraftMessage).toHaveBeenCalledWith("First Second");
+    });
+
+    it("does not save if content matches existing draft", () => {
+      // Arrange
+      const conversationId = "conv-no-change";
+      const existingDraft = "Existing draft";
+      const chatInputRef = createMockChatInputRef(existingDraft);
+
+      vi.mocked(conversationLocalStorage.useConversationLocalStorageState).mockReturnValue({
+        state: {
+          selectedTab: "editor",
+          rightPanelShown: true,
+          unpinnedTabs: [],
+          conversationMode: "code",
+          subConversationTaskId: null,
+          draftMessage: existingDraft,
+        },
+        setSelectedTab: vi.fn(),
+        setRightPanelShown: vi.fn(),
+        setUnpinnedTabs: vi.fn(),
+        setConversationMode: vi.fn(),
+        setDraftMessage: mockSetDraftMessage,
+      });
+
+      vi.mocked(conversationLocalStorage.getConversationState).mockReturnValue({
+        selectedTab: "editor",
+        rightPanelShown: true,
+        unpinnedTabs: [],
+        conversationMode: "code",
+        subConversationTaskId: null,
+        draftMessage: existingDraft,
+      });
+
+      const { result } = renderHook(() =>
+        useDraftPersistence(conversationId, chatInputRef),
+      );
+
+      // Act - try to save same content
+      act(() => {
+        result.current.saveDraft();
+      });
+
+      act(() => {
+        vi.advanceTimersByTime(500);
+      });
+
+      // Assert - should not save since content is the same
+      expect(mockSetDraftMessage).not.toHaveBeenCalled();
+    });
+  });
+
+  describe("clearDraft", () => {
+    it("clears the draft from localStorage", () => {
+      // Arrange
+      const conversationId = "conv-clear-1";
+      const chatInputRef = createMockChatInputRef("Some content");
+
+      const { result } = renderHook(() =>
+        useDraftPersistence(conversationId, chatInputRef),
+      );
+
+      // Act
+      act(() => {
+        result.current.clearDraft();
+      });
+
+      // Assert
+      expect(mockSetDraftMessage).toHaveBeenCalledWith(null);
+    });
+
+    it("cancels any pending debounced save when clearing", () => {
+      // Arrange
+      const conversationId = "conv-clear-2";
+      const chatInputRef = createMockChatInputRef();
+
+      const { result } = renderHook(() =>
+        useDraftPersistence(conversationId, chatInputRef),
+      );
+
+      // Start a save
+      chatInputRef.current!.textContent = "Pending draft";
+      act(() => {
+        result.current.saveDraft();
+      });
+
+      // Clear before debounce completes
+      act(() => {
+        vi.advanceTimersByTime(200);
+        result.current.clearDraft();
+      });
+
+      // Complete the original debounce period
+      act(() => {
+        vi.advanceTimersByTime(500);
+      });
+
+      // Assert - only the clear should have been called (the pending save should be cancelled)
+      expect(mockSetDraftMessage).toHaveBeenCalledTimes(1);
+      expect(mockSetDraftMessage).toHaveBeenCalledWith(null);
+    });
+  });
+
+  describe("conversation switching", () => {
+    it("clears input when switching to a new conversation without a draft", () => {
+      // Arrange
+      const chatInputRef = createMockChatInputRef("Draft from conv A");
+
+      // First conversation has a draft
+      vi.mocked(conversationLocalStorage.getConversationState)
+        .mockReturnValueOnce({
+          selectedTab: "editor",
+          rightPanelShown: true,
+          unpinnedTabs: [],
+          conversationMode: "code",
+          subConversationTaskId: null,
+          draftMessage: "Draft from conv A",
+        })
+        .mockReturnValue({
+          selectedTab: "editor",
+          rightPanelShown: true,
+          unpinnedTabs: [],
+          conversationMode: "code",
+          subConversationTaskId: null,
+          draftMessage: null,
+        });
+
+      const { rerender } = renderHook(
+        ({ conversationId }) =>
+          useDraftPersistence(conversationId, chatInputRef),
+        { initialProps: { conversationId: "conv-A" } },
+      );
+
+      // Act - switch to conversation B
+      rerender({ conversationId: "conv-B" });
+
+      // Assert - input should be cleared (no draft for conv-B)
+      expect(chatInputRef.current?.textContent).toBe("");
+    });
+
+    it("restores draft when switching to a conversation with an existing draft", () => {
+      // Arrange
+      const chatInputRef = createMockChatInputRef();
+      const draftForConvB = "Saved draft for conversation B";
+
+      vi.mocked(conversationLocalStorage.getConversationState)
+        .mockReturnValueOnce({
+          selectedTab: "editor",
+          rightPanelShown: true,
+          unpinnedTabs: [],
+          conversationMode: "code",
+          subConversationTaskId: null,
+          draftMessage: null,
+        })
+        .mockReturnValue({
+          selectedTab: "editor",
+          rightPanelShown: true,
+          unpinnedTabs: [],
+          conversationMode: "code",
+          subConversationTaskId: null,
+          draftMessage: draftForConvB,
+        });
+
+      const { rerender } = renderHook(
+        ({ conversationId }) =>
+          useDraftPersistence(conversationId, chatInputRef),
+        { initialProps: { conversationId: "conv-A" } },
+      );
+
+      // Act - switch to conversation B
+      rerender({ conversationId: "conv-B" });
+
+      // Assert - draft for conv-B should be restored
+      expect(chatInputRef.current?.textContent).toBe(draftForConvB);
+    });
+
+    it("cancels pending save when switching conversations", () => {
+      // Arrange
+      const chatInputRef = createMockChatInputRef();
+
+      const { result, rerender } = renderHook(
+        ({ conversationId }) =>
+          useDraftPersistence(conversationId, chatInputRef),
+        { initialProps: { conversationId: "conv-A" } },
+      );
+
+      // Start typing in conv-A
+      chatInputRef.current!.textContent = "Draft for conv-A";
+      act(() => {
+        result.current.saveDraft();
+      });
+
+      // Switch conversation before debounce completes
+      act(() => {
+        vi.advanceTimersByTime(200);
+      });
+      rerender({ conversationId: "conv-B" });
+
+      // Complete the debounce period
+      act(() => {
+        vi.advanceTimersByTime(500);
+      });
+
+      // Assert - the save should NOT have happened because conversation changed
+      expect(mockSetDraftMessage).not.toHaveBeenCalled();
+    });
+  });
+
+  describe("task ID to real conversation ID transition", () => {
+    it("transfers draft from task ID to real conversation ID during transition", () => {
+      // Arrange
+      const chatInputRef = createMockChatInputRef("Draft typed during init");
+
+      vi.mocked(conversationLocalStorage.getConversationState).mockReturnValue({
+        selectedTab: "editor",
+        rightPanelShown: true,
+        unpinnedTabs: [],
+        conversationMode: "code",
+        subConversationTaskId: null,
+        draftMessage: null,
+      });
+
+      const { rerender } = renderHook(
+        ({ conversationId }) =>
+          useDraftPersistence(conversationId, chatInputRef),
+        { initialProps: { conversationId: "task-abc-123" } },
+      );
+
+      // Simulate user typing during task initialization
+      chatInputRef.current!.textContent = "Draft typed during init";
+
+      // Act - transition to real conversation ID
+      rerender({ conversationId: "conv-real-123" });
+
+      // Assert - draft should be saved to the new real conversation ID
+      expect(conversationLocalStorage.setConversationState).toHaveBeenCalledWith(
+        "conv-real-123",
+        { draftMessage: "Draft typed during init" },
+      );
+
+      // And the draft should remain visible in the input
+      expect(chatInputRef.current?.textContent).toBe("Draft typed during init");
+    });
+
+    it("does not transfer empty draft during task-to-real transition", () => {
+      // Arrange
+      const chatInputRef = createMockChatInputRef("");
+
+      vi.mocked(conversationLocalStorage.getConversationState).mockReturnValue({
+        selectedTab: "editor",
+        rightPanelShown: true,
+        unpinnedTabs: [],
+        conversationMode: "code",
+        subConversationTaskId: null,
+        draftMessage: null,
+      });
+
+      const { rerender } = renderHook(
+        ({ conversationId }) =>
+          useDraftPersistence(conversationId, chatInputRef),
+        { initialProps: { conversationId: "task-abc-123" } },
+      );
+
+      // Act - transition to real conversation ID with empty input
+      rerender({ conversationId: "conv-real-123" });
+
+      // Assert - no draft should be saved (input is cleared, checked by hook)
+      // The setConversationState should not be called with draftMessage
+      expect(conversationLocalStorage.setConversationState).not.toHaveBeenCalled();
+    });
+
+    it("does not transfer draft for non-task ID transitions", () => {
+      // Arrange
+      const chatInputRef = createMockChatInputRef("Some draft");
+
+      vi.mocked(conversationLocalStorage.getConversationState).mockReturnValue({
+        selectedTab: "editor",
+        rightPanelShown: true,
+        unpinnedTabs: [],
+        conversationMode: "code",
+        subConversationTaskId: null,
+        draftMessage: null,
+      });
+
+      const { rerender } = renderHook(
+        ({ conversationId }) =>
+          useDraftPersistence(conversationId, chatInputRef),
+        { initialProps: { conversationId: "conv-A" } },
+      );
+
+      // Act - normal conversation switch (not task-to-real)
+      rerender({ conversationId: "conv-B" });
+
+      // Assert - should not use setConversationState directly
+      // (the normal path uses setDraftMessage from the hook)
+      expect(conversationLocalStorage.setConversationState).not.toHaveBeenCalled();
+    });
+  });
+
+  describe("hasDraft and isRestored state", () => {
+    it("returns hasDraft true when draft exists in hook state", () => {
+      // Arrange
+      const conversationId = "conv-has-draft";
+      const chatInputRef = createMockChatInputRef();
+
+      vi.mocked(conversationLocalStorage.useConversationLocalStorageState).mockReturnValue({
+        state: {
+          selectedTab: "editor",
+          rightPanelShown: true,
+          unpinnedTabs: [],
+          conversationMode: "code",
+          subConversationTaskId: null,
+          draftMessage: "Existing draft",
+        },
+        setSelectedTab: vi.fn(),
+        setRightPanelShown: vi.fn(),
+        setUnpinnedTabs: vi.fn(),
+        setConversationMode: vi.fn(),
+        setDraftMessage: mockSetDraftMessage,
+      });
+
+      // Act
+      const { result } = renderHook(() =>
+        useDraftPersistence(conversationId, chatInputRef),
+      );
+
+      // Assert
+      expect(result.current.hasDraft).toBe(true);
+    });
+
+    it("returns hasDraft false when no draft exists", () => {
+      // Arrange
+      const conversationId = "conv-no-draft";
+      const chatInputRef = createMockChatInputRef();
+
+      // Act
+      const { result } = renderHook(() =>
+        useDraftPersistence(conversationId, chatInputRef),
+      );
+
+      // Assert
+      expect(result.current.hasDraft).toBe(false);
+    });
+
+    it("sets isRestored to true after restoration completes", () => {
+      // Arrange
+      const conversationId = "conv-restored";
+      const chatInputRef = createMockChatInputRef();
+
+      vi.mocked(conversationLocalStorage.getConversationState).mockReturnValue({
+        selectedTab: "editor",
+        rightPanelShown: true,
+        unpinnedTabs: [],
+        conversationMode: "code",
+        subConversationTaskId: null,
+        draftMessage: "Draft to restore",
+      });
+
+      // Act
+      const { result } = renderHook(() =>
+        useDraftPersistence(conversationId, chatInputRef),
+      );
+
+      // Assert
+      expect(result.current.isRestored).toBe(true);
+    });
+  });
+
+  describe("cleanup on unmount", () => {
+    it("clears pending timeout on unmount", () => {
+      // Arrange
+      const conversationId = "conv-unmount";
+      const chatInputRef = createMockChatInputRef();
+
+      const { result, unmount } = renderHook(() =>
+        useDraftPersistence(conversationId, chatInputRef),
+      );
+
+      // Start a save
+      chatInputRef.current!.textContent = "Draft";
+      act(() => {
+        result.current.saveDraft();
+      });
+
+      // Unmount before debounce completes
+      unmount();
+
+      // Complete the debounce period
+      act(() => {
+        vi.advanceTimersByTime(500);
+      });
+
+      // Assert - save should not have been called after unmount
+      expect(mockSetDraftMessage).not.toHaveBeenCalled();
+    });
+  });
+});

frontend/__tests__/hooks/use-handle-plan-click.test.tsx

@@ -88,6 +88,7 @@ describe("useHandlePlanClick", () => {
       unpinnedTabs: [],
       subConversationTaskId: null,
       conversationMode: "code",
+      draftMessage: null,
     });
   });
 
@@ -117,6 +118,7 @@ describe("useHandlePlanClick", () => {
         unpinnedTabs: [],
         subConversationTaskId: storedTaskId,
         conversationMode: "code",
+        draftMessage: null,
       });
 
       renderHook(() => useHandlePlanClick());
@@ -155,6 +157,7 @@ describe("useHandlePlanClick", () => {
         unpinnedTabs: [],
         subConversationTaskId: storedTaskId,
         conversationMode: "code",
+        draftMessage: null,
       });
 
       renderHook(() => useHandlePlanClick());

frontend/src/api/pending-message-service/pending-message-service.api.ts

@@ -0,0 +1,40 @@
+/**
+ * Pending Message Service
+ *
+ * This service handles server-side message queuing for V1 conversations.
+ * Messages can be queued when the WebSocket is not connected and will be
+ * delivered automatically when the conversation becomes ready.
+ */
+
+import { openHands } from "../open-hands-axios";
+import type {
+  PendingMessageResponse,
+  QueuePendingMessageRequest,
+} from "./pending-message-service.types";
+
+class PendingMessageService {
+  /**
+   * Queue a message for delivery when conversation becomes ready.
+   *
+   * This endpoint allows users to submit messages even when the conversation's
+   * WebSocket connection is not yet established. Messages are stored server-side
+   * and delivered automatically when the conversation transitions to READY status.
+   *
+   * @param conversationId The conversation ID (can be task ID before conversation is ready)
+   * @param message The message to queue
+   * @returns PendingMessageResponse with the message ID and queue position
+   * @throws Error if too many pending messages (limit: 10 per conversation)
+   */
+  static async queueMessage(
+    conversationId: string,
+    message: QueuePendingMessageRequest,
+  ): Promise<PendingMessageResponse> {
+    const { data } = await openHands.post<PendingMessageResponse>(
+      `/api/v1/conversations/${conversationId}/pending-messages`,
+      message,
+    );
+    return data;
+  }
+}
+
+export default PendingMessageService;

frontend/src/api/pending-message-service/pending-message-service.types.ts

@@ -0,0 +1,22 @@
+/**
+ * Types for the pending message service
+ */
+
+import type { V1MessageContent } from "../conversation-service/v1-conversation-service.types";
+
+/**
+ * Response when queueing a pending message
+ */
+export interface PendingMessageResponse {
+  id: string;
+  queued: boolean;
+  position: number;
+}
+
+/**
+ * Request to queue a pending message
+ */
+export interface QueuePendingMessageRequest {
+  role?: "user";
+  content: V1MessageContent[];
+}

frontend/src/components/features/chat/chat-interface.tsx

@@ -190,8 +190,14 @@ export function ChatInterface() {
     const prompt =
       uploadedFiles.length > 0 ? `${content}\n\n${filePrompt}` : content;
 
-    send(createChatMessage(prompt, imageUrls, uploadedFiles, timestamp));
-    setOptimisticUserMessage(content);
+    const result = await send(
+      createChatMessage(prompt, imageUrls, uploadedFiles, timestamp),
+    );
+    // Only show optimistic UI if message was sent immediately via WebSocket
+    // If queued for later delivery, the message will appear when actually delivered
+    if (!result.queued) {
+      setOptimisticUserMessage(content);
+    }
     setMessageToSend("");
   };
 

frontend/src/components/features/chat/custom-chat-input.tsx

@@ -60,6 +60,7 @@ export function CustomChatInput({
     messageToSend,
     checkIsContentEmpty,
     clearEmptyContentHandler,
+    saveDraft,
   } = useChatInputLogic();
 
   const {
@@ -158,6 +159,7 @@ export function CustomChatInput({
           onInput={() => {
             handleInput();
             updateSlashMenu();
+            saveDraft();
           }}
           onPaste={handlePaste}
           onKeyDown={(e) => {

frontend/src/components/features/chat/interactive-chat-box.tsx

@@ -142,8 +142,9 @@ export function InteractiveChatBox({ onSubmit }: InteractiveChatBoxProps) {
     handleSubmit(suggestion);
   };
 
+  // Allow users to submit messages during LOADING state - they will be
+  // queued server-side and delivered when the conversation becomes ready
   const isDisabled =
-    curAgentState === AgentState.LOADING ||
     curAgentState === AgentState.AWAITING_USER_CONFIRMATION ||
     isTaskPolling(subConversationTaskStatus);
 

frontend/src/contexts/conversation-websocket-context.tsx

@@ -40,6 +40,7 @@ import type {
   V1SendMessageRequest,
 } from "#/api/conversation-service/v1-conversation-service.types";
 import EventService from "#/api/event-service/event-service.api";
+import PendingMessageService from "#/api/pending-message-service/pending-message-service.api";
 import { useConversationStore } from "#/stores/conversation-store";
 import { isBudgetOrCreditError, trackError } from "#/utils/error-handler";
 import { useTracking } from "#/hooks/use-tracking";
@@ -47,6 +48,7 @@ import { useReadConversationFile } from "#/hooks/mutation/use-read-conversation-
 import useMetricsStore from "#/stores/metrics-store";
 import { I18nKey } from "#/i18n/declaration";
 import { useConversationHistory } from "#/hooks/query/use-conversation-history";
+import { setConversationState } from "#/utils/conversation-local-storage";
 
 // eslint-disable-next-line @typescript-eslint/naming-convention
 export type V1_WebSocketConnectionState =
@@ -55,9 +57,13 @@ export type V1_WebSocketConnectionState =
   | "CLOSED"
   | "CLOSING";
 
+interface SendMessageResult {
+  queued: boolean; // true if message was queued for later delivery, false if sent immediately
+}
+
 interface ConversationWebSocketContextType {
   connectionState: V1_WebSocketConnectionState;
-  sendMessage: (message: V1SendMessageRequest) => Promise<void>;
+  sendMessage: (message: V1SendMessageRequest) => Promise<SendMessageResult>;
   isLoadingHistory: boolean;
 }
 
@@ -397,6 +403,10 @@ export function ConversationWebSocketProvider({
           // Clear optimistic user message when a user message is confirmed
           if (isUserMessageEvent(event)) {
             removeOptimisticUserMessage();
+            // Clear draft from localStorage - message was successfully delivered
+            if (conversationId) {
+              setConversationState(conversationId, { draftMessage: null });
+            }
           }
 
           // Handle cache invalidation for ActionEvent
@@ -556,6 +566,11 @@ export function ConversationWebSocketProvider({
           // Clear optimistic user message when a user message is confirmed
           if (isUserMessageEvent(event)) {
             removeOptimisticUserMessage();
+            // Clear draft from localStorage - message was successfully delivered
+            // Use main conversationId since user types in main conversation input
+            if (conversationId) {
+              setConversationState(conversationId, { draftMessage: null });
+            }
           }
 
           // Handle cache invalidation for ActionEvent
@@ -810,21 +825,44 @@ export function ConversationWebSocketProvider({
   );
 
   // V1 send message function via WebSocket
+  // Falls back to REST API queue when WebSocket is not connected
   const sendMessage = useCallback(
-    async (message: V1SendMessageRequest) => {
+    async (message: V1SendMessageRequest): Promise<SendMessageResult> => {
       const currentMode = useConversationStore.getState().conversationMode;
       const currentSocket =
         currentMode === "plan" ? planningAgentSocket : mainSocket;
 
       if (!currentSocket || currentSocket.readyState !== WebSocket.OPEN) {
-        const error = "WebSocket is not connected";
-        setErrorMessage(error);
-        throw new Error(error);
+        // WebSocket not connected - queue message via REST API
+        // Message will be delivered automatically when conversation becomes ready
+        if (!conversationId) {
+          const error = new Error("No conversation ID available");
+          setErrorMessage(error.message);
+          throw error;
+        }
+
+        try {
+          await PendingMessageService.queueMessage(conversationId, {
+            role: "user",
+            content: message.content,
+          });
+          // Message queued successfully - it will be delivered when ready
+          // Return queued: true so caller knows not to show optimistic UI
+          return { queued: true };
+        } catch (error) {
+          const errorMessage =
+            error instanceof Error
+              ? error.message
+              : "Failed to queue message for delivery";
+          setErrorMessage(errorMessage);
+          throw error;
+        }
       }
 
       try {
         // Send message through WebSocket as JSON
         currentSocket.send(JSON.stringify(message));
+        return { queued: false };
       } catch (error) {
         const errorMessage =
           error instanceof Error ? error.message : "Failed to send message";
@@ -832,7 +870,7 @@ export function ConversationWebSocketProvider({
         throw error;
       }
     },
-    [mainSocket, planningAgentSocket, setErrorMessage],
+    [mainSocket, planningAgentSocket, setErrorMessage, conversationId],
   );
 
   // Track main socket state changes

frontend/src/hooks/chat/use-chat-input-logic.ts

@@ -5,12 +5,15 @@ import {
   getTextContent,
 } from "#/components/features/chat/utils/chat-input.utils";
 import { useConversationStore } from "#/stores/conversation-store";
+import { useConversationId } from "#/hooks/use-conversation-id";
+import { useDraftPersistence } from "./use-draft-persistence";
 
 /**
  * Hook for managing chat input content logic
  */
 export const useChatInputLogic = () => {
   const chatInputRef = useRef<HTMLDivElement | null>(null);
+  const { conversationId } = useConversationId();
 
   const {
     messageToSend,
@@ -19,6 +22,12 @@ export const useChatInputLogic = () => {
     setIsRightPanelShown,
   } = useConversationStore();
 
+  // Draft persistence - saves to localStorage, restores on mount
+  const { saveDraft, clearDraft } = useDraftPersistence(
+    conversationId,
+    chatInputRef,
+  );
+
   // Save current input value when drawer state changes
   useEffect(() => {
     if (chatInputRef.current) {
@@ -51,5 +60,7 @@ export const useChatInputLogic = () => {
     checkIsContentEmpty,
     clearEmptyContentHandler,
     getCurrentMessage,
+    saveDraft,
+    clearDraft,
   };
 };

frontend/src/hooks/chat/use-draft-persistence.ts

@@ -0,0 +1,179 @@
+import { useEffect, useRef, useCallback, useState } from "react";
+import {
+  useConversationLocalStorageState,
+  getConversationState,
+  setConversationState,
+} from "#/utils/conversation-local-storage";
+import { getTextContent } from "#/components/features/chat/utils/chat-input.utils";
+
+/**
+ * Check if a conversation ID is a temporary task ID.
+ * Task IDs have the format "task-{uuid}" and are used during V1 conversation initialization.
+ */
+const isTaskId = (id: string): boolean => id.startsWith("task-");
+
+const DRAFT_SAVE_DEBOUNCE_MS = 500;
+
+/**
+ * Hook for persisting draft messages to localStorage.
+ * Handles debounced saving on input, restoration on mount, and clearing on confirmed delivery.
+ */
+export const useDraftPersistence = (
+  conversationId: string,
+  chatInputRef: React.RefObject<HTMLDivElement | null>,
+) => {
+  const { state, setDraftMessage } =
+    useConversationLocalStorageState(conversationId);
+  const saveTimeoutRef = useRef<ReturnType<typeof setTimeout> | null>(null);
+  const hasRestoredRef = useRef(false);
+  const [isRestored, setIsRestored] = useState(false);
+
+  // Track current conversationId to prevent saving draft to wrong conversation
+  const currentConversationIdRef = useRef(conversationId);
+  // Track if this is the first mount to handle initial cleanup
+  const isFirstMountRef = useRef(true);
+
+  // IMPORTANT: This effect must run FIRST when conversation changes.
+  // It handles three concerns:
+  // 1. Cleanup: Cancel pending saves from previous conversation
+  // 2. Task-to-real transition: Preserve draft typed during initialization
+  // 3. DOM reset: Clear stale content before restoration effect runs
+  useEffect(() => {
+    const previousConversationId = currentConversationIdRef.current;
+    const isInitialMount = isFirstMountRef.current;
+    currentConversationIdRef.current = conversationId;
+    isFirstMountRef.current = false;
+
+    // --- 1. Cancel pending saves from previous conversation ---
+    // Prevents draft from being saved to wrong conversation if user switched quickly
+    if (saveTimeoutRef.current) {
+      clearTimeout(saveTimeoutRef.current);
+      saveTimeoutRef.current = null;
+    }
+
+    const element = chatInputRef.current;
+
+    // --- 2. Handle task-to-real ID transition (preserve draft during initialization) ---
+    // When a new V1 conversation initializes, it starts with a temporary "task-xxx" ID
+    // that transitions to a real conversation ID once ready. Task IDs don't persist
+    // to localStorage, so any draft typed during this phase would be lost.
+    // We detect this transition and transfer the draft to the new real ID.
+    if (!isInitialMount && previousConversationId !== conversationId) {
+      const wasTaskId = isTaskId(previousConversationId);
+      const isNowRealId = !isTaskId(conversationId);
+
+      if (wasTaskId && isNowRealId && element) {
+        const currentText = getTextContent(element).trim();
+        if (currentText) {
+          // Transfer draft to the new (real) conversation ID
+          setConversationState(conversationId, { draftMessage: currentText });
+          // Keep draft visible in DOM and mark as restored to prevent overwrite
+          hasRestoredRef.current = true;
+          setIsRestored(true);
+          return; // Skip normal cleanup - draft is already in correct state
+        }
+      }
+    }
+
+    // --- 3. Clear stale DOM content (will be restored by next effect if draft exists) ---
+    // This prevents stale drafts from appearing in new conversations due to:
+    // - Browser form restoration on back/forward navigation
+    // - React DOM recycling between conversation switches
+    // The restoration effect will then populate with the correct saved draft
+    if (element) {
+      element.textContent = "";
+    }
+
+    // Reset restoration flag so the restoration effect will run for new conversation
+    hasRestoredRef.current = false;
+    setIsRestored(false);
+  }, [conversationId, chatInputRef]);
+
+  // Restore draft from localStorage - reads directly to avoid state sync timing issues
+  useEffect(() => {
+    if (hasRestoredRef.current) {
+      return;
+    }
+
+    const element = chatInputRef.current;
+    if (!element) {
+      return;
+    }
+
+    // Read directly from localStorage to avoid stale state from useConversationLocalStorageState
+    // The hook's state may not have synced yet after conversationId change
+    const { draftMessage } = getConversationState(conversationId);
+
+    // Only restore if there's a saved draft and the input is empty
+    if (draftMessage && getTextContent(element).trim() === "") {
+      element.textContent = draftMessage;
+      // Move cursor to end
+      const selection = window.getSelection();
+      const range = document.createRange();
+      range.selectNodeContents(element);
+      range.collapse(false);
+      selection?.removeAllRanges();
+      selection?.addRange(range);
+    }
+
+    hasRestoredRef.current = true;
+    setIsRestored(true);
+  }, [chatInputRef, conversationId]);
+
+  // Debounced save function - called from onInput handler
+  const saveDraft = useCallback(() => {
+    // Clear any pending save
+    if (saveTimeoutRef.current) {
+      clearTimeout(saveTimeoutRef.current);
+    }
+
+    // Capture the conversationId at the time of input
+    const capturedConversationId = conversationId;
+
+    saveTimeoutRef.current = setTimeout(() => {
+      // Verify we're still on the same conversation before saving
+      // This prevents saving draft to wrong conversation if user switched quickly
+      if (capturedConversationId !== currentConversationIdRef.current) {
+        return;
+      }
+
+      const element = chatInputRef.current;
+      if (!element) {
+        return;
+      }
+
+      const text = getTextContent(element).trim();
+      // Only save if content has changed
+      if (text !== (state.draftMessage || "")) {
+        setDraftMessage(text || null);
+      }
+    }, DRAFT_SAVE_DEBOUNCE_MS);
+  }, [chatInputRef, state.draftMessage, setDraftMessage, conversationId]);
+
+  // Clear draft - called after message delivery is confirmed
+  const clearDraft = useCallback(() => {
+    // Cancel any pending save
+    if (saveTimeoutRef.current) {
+      clearTimeout(saveTimeoutRef.current);
+      saveTimeoutRef.current = null;
+    }
+    setDraftMessage(null);
+  }, [setDraftMessage]);
+
+  // Cleanup timeout on unmount
+  useEffect(
+    () => () => {
+      if (saveTimeoutRef.current) {
+        clearTimeout(saveTimeoutRef.current);
+      }
+    },
+    [],
+  );
+
+  return {
+    saveDraft,
+    clearDraft,
+    isRestored,
+    hasDraft: !!state.draftMessage,
+  };
+};

frontend/src/hooks/use-send-message.ts

@@ -5,6 +5,10 @@ import { useConversationWebSocket } from "#/contexts/conversation-websocket-cont
 import { useConversationId } from "#/hooks/use-conversation-id";
 import { V1MessageContent } from "#/api/conversation-service/v1-conversation-service.types";
 
+interface SendResult {
+  queued: boolean; // true if message was queued for later delivery
+}
+
 /**
  * Unified hook for sending messages that works with both V0 and V1 conversations
  * - For V0 conversations: Uses Socket.IO WebSocket via useWsClient
@@ -26,7 +30,7 @@ export function useSendMessage() {
     conversation?.conversation_version === "V1";
 
   const send = useCallback(
-    async (event: Record<string, unknown>) => {
+    async (event: Record<string, unknown>): Promise<SendResult> => {
       if (isV1Conversation && v1Context) {
         // V1: Convert V0 event format to V1 message format
         const { action, args } = event as {
@@ -57,19 +61,20 @@ export function useSendMessage() {
           }
 
           // Send via V1 WebSocket context (uses correct host/port)
-          await v1Context.sendMessage({
+          const result = await v1Context.sendMessage({
             role: "user",
             content,
           });
-        } else {
-          // For non-message events, fall back to V0 send
-          // (e.g., agent state changes, other control events)
-          v0Send(event);
+          return result;
         }
-      } else {
-        // V0: Use Socket.IO
+        // For non-message events, fall back to V0 send
+        // (e.g., agent state changes, other control events)
         v0Send(event);
+        return { queued: false };
       }
+      // V0: Use Socket.IO
+      v0Send(event);
+      return { queued: false };
     },
     [isV1Conversation, v1Context, v0Send, conversationId],
   );

frontend/src/utils/conversation-local-storage.ts

@@ -23,6 +23,7 @@ export interface ConversationState {
   unpinnedTabs: string[];
   conversationMode: ConversationMode;
   subConversationTaskId: string | null;
+  draftMessage: string | null;
 }
 
 const DEFAULT_CONVERSATION_STATE: ConversationState = {
@@ -31,6 +32,7 @@ const DEFAULT_CONVERSATION_STATE: ConversationState = {
   unpinnedTabs: [],
   conversationMode: "code",
   subConversationTaskId: null,
+  draftMessage: null,
 };
 
 /**
@@ -121,6 +123,7 @@ export function useConversationLocalStorageState(conversationId: string): {
   setRightPanelShown: (shown: boolean) => void;
   setUnpinnedTabs: (tabs: string[]) => void;
   setConversationMode: (mode: ConversationMode) => void;
+  setDraftMessage: (message: string | null) => void;
 } {
   const [state, setState] = useState<ConversationState>(() =>
     getConversationState(conversationId),
@@ -178,5 +181,6 @@ export function useConversationLocalStorageState(conversationId: string): {
     setRightPanelShown: (shown) => updateState({ rightPanelShown: shown }),
     setUnpinnedTabs: (tabs) => updateState({ unpinnedTabs: tabs }),
     setConversationMode: (mode) => updateState({ conversationMode: mode }),
+    setDraftMessage: (message) => updateState({ draftMessage: message }),
   };
 }

openhands/app_server/app_conversation/live_status_app_conversation_service.py

@@ -59,6 +59,9 @@ from openhands.app_server.event_callback.event_callback_service import (
 from openhands.app_server.event_callback.set_title_callback_processor import (
     SetTitleCallbackProcessor,
 )
+from openhands.app_server.pending_messages.pending_message_service import (
+    PendingMessageService,
+)
 from openhands.app_server.sandbox.docker_sandbox_service import DockerSandboxService
 from openhands.app_server.sandbox.sandbox_models import (
     AGENT_SERVER,
@@ -127,6 +130,7 @@ class LiveStatusAppConversationService(AppConversationServiceBase):
     sandbox_service: SandboxService
     sandbox_spec_service: SandboxSpecService
     jwt_service: JwtService
+    pending_message_service: PendingMessageService
     sandbox_startup_timeout: int
     sandbox_startup_poll_frequency: int
     max_num_conversations_per_sandbox: int
@@ -373,6 +377,15 @@ class LiveStatusAppConversationService(AppConversationServiceBase):
             task.app_conversation_id = info.id
             yield task
 
+            # Process any pending messages queued while waiting for conversation
+            if sandbox.session_api_key:
+                await self._process_pending_messages(
+                    task_id=task.id,
+                    conversation_id=info.id,
+                    agent_server_url=agent_server_url,
+                    session_api_key=sandbox.session_api_key,
+                )
+
         except Exception as exc:
             _logger.exception('Error starting conversation', stack_info=True)
             task.status = AppConversationStartTaskStatus.ERROR
@@ -1424,6 +1437,89 @@ class LiveStatusAppConversationService(AppConversationServiceBase):
             plugins=plugins,
         )
 
+    async def _process_pending_messages(
+        self,
+        task_id: UUID,
+        conversation_id: UUID,
+        agent_server_url: str,
+        session_api_key: str,
+    ) -> None:
+        """Process pending messages queued before conversation was ready.
+
+        Messages are delivered concurrently to the agent server. After processing,
+        all messages are deleted from the database regardless of success or failure.
+
+        Args:
+            task_id: The start task ID (may have been used as conversation_id initially)
+            conversation_id: The real conversation ID
+            agent_server_url: URL of the agent server
+            session_api_key: API key for authenticating with agent server
+        """
+        # Convert UUIDs to strings for the pending message service
+        # The frontend uses task-{uuid.hex} format (no hyphens), matching OpenHandsUUID serialization
+        task_id_str = f'task-{task_id.hex}'
+        # conversation_id uses standard format (with hyphens) for agent server API compatibility
+        conversation_id_str = str(conversation_id)
+
+        _logger.info(f'task_id={task_id_str} conversation_id={conversation_id_str}')
+
+        # First, update any messages that were queued with the task_id
+        updated_count = await self.pending_message_service.update_conversation_id(
+            old_conversation_id=task_id_str,
+            new_conversation_id=conversation_id_str,
+        )
+        _logger.info(f'updated_count={updated_count} ')
+        if updated_count > 0:
+            _logger.info(
+                f'Updated {updated_count} pending messages from task_id={task_id_str} '
+                f'to conversation_id={conversation_id_str}'
+            )
+
+        # Get all pending messages for this conversation
+        pending_messages = await self.pending_message_service.get_pending_messages(
+            conversation_id_str
+        )
+
+        if not pending_messages:
+            return
+
+        _logger.info(
+            f'Processing {len(pending_messages)} pending messages for '
+            f'conversation {conversation_id_str}'
+        )
+
+        # Process messages sequentially to preserve order
+        for msg in pending_messages:
+            try:
+                # Serialize content objects to JSON-compatible dicts
+                content_json = [item.model_dump() for item in msg.content]
+                # Use the events endpoint which handles message sending
+                response = await self.httpx_client.post(
+                    f'{agent_server_url}/api/conversations/{conversation_id_str}/events',
+                    json={
+                        'role': msg.role,
+                        'content': content_json,
+                        'run': True,
+                    },
+                    headers={'X-Session-API-Key': session_api_key},
+                    timeout=30.0,
+                )
+                response.raise_for_status()
+                _logger.debug(f'Delivered pending message {msg.id}')
+            except Exception as e:
+                _logger.warning(f'Failed to deliver pending message {msg.id}: {e}')
+
+        # Delete all pending messages after processing (regardless of success/failure)
+        deleted_count = (
+            await self.pending_message_service.delete_messages_for_conversation(
+                conversation_id_str
+            )
+        )
+        _logger.info(
+            f'Finished processing pending messages for conversation {conversation_id_str}. '
+            f'Deleted {deleted_count} messages.'
+        )
+
     async def update_agent_server_conversation_title(
         self,
         conversation_id: str,
@@ -1796,6 +1892,7 @@ class LiveStatusAppConversationServiceInjector(AppConversationServiceInjector):
             get_global_config,
             get_httpx_client,
             get_jwt_service,
+            get_pending_message_service,
             get_sandbox_service,
             get_sandbox_spec_service,
             get_user_context,
@@ -1815,6 +1912,7 @@ class LiveStatusAppConversationServiceInjector(AppConversationServiceInjector):
             get_event_service(state, request) as event_service,
             get_jwt_service(state, request) as jwt_service,
             get_httpx_client(state, request) as httpx_client,
+            get_pending_message_service(state, request) as pending_message_service,
         ):
             access_token_hard_timeout = None
             if self.access_token_hard_timeout:
@@ -1859,6 +1957,7 @@ class LiveStatusAppConversationServiceInjector(AppConversationServiceInjector):
                 event_callback_service=event_callback_service,
                 event_service=event_service,
                 jwt_service=jwt_service,
+                pending_message_service=pending_message_service,
                 sandbox_startup_timeout=self.sandbox_startup_timeout,
                 sandbox_startup_poll_frequency=self.sandbox_startup_poll_frequency,
                 max_num_conversations_per_sandbox=self.max_num_conversations_per_sandbox,

openhands/app_server/app_lifespan/alembic/versions/007.py

@@ -0,0 +1,39 @@
+"""Add pending_messages table for server-side message queuing
+
+Revision ID: 007
+Revises: 006
+Create Date: 2025-03-15 00:00:00.000000
+
+"""
+
+from typing import Sequence, Union
+
+import sqlalchemy as sa
+from alembic import op
+
+# revision identifiers, used by Alembic.
+revision: str = '007'
+down_revision: Union[str, None] = '006'
+branch_labels: Union[str, Sequence[str], None] = None
+depends_on: Union[str, Sequence[str], None] = None
+
+
+def upgrade() -> None:
+    """Create pending_messages table for storing messages before conversation is ready.
+
+    Messages are stored temporarily until the conversation becomes ready, then
+    delivered and deleted regardless of success or failure.
+    """
+    op.create_table(
+        'pending_messages',
+        sa.Column('id', sa.String(), primary_key=True),
+        sa.Column('conversation_id', sa.String(), nullable=False, index=True),
+        sa.Column('role', sa.String(20), nullable=False, server_default='user'),
+        sa.Column('content', sa.JSON, nullable=False),
+        sa.Column('created_at', sa.DateTime(timezone=True), nullable=False),
+    )
+
+
+def downgrade() -> None:
+    """Remove pending_messages table."""
+    op.drop_table('pending_messages')

openhands/app_server/config.py

@@ -33,6 +33,10 @@ from openhands.app_server.event_callback.event_callback_service import (
     EventCallbackService,
     EventCallbackServiceInjector,
 )
+from openhands.app_server.pending_messages.pending_message_service import (
+    PendingMessageService,
+    PendingMessageServiceInjector,
+)
 from openhands.app_server.sandbox.sandbox_service import (
     SandboxService,
     SandboxServiceInjector,
@@ -114,6 +118,7 @@ class AppServerConfig(OpenHandsModel):
     app_conversation_info: AppConversationInfoServiceInjector | None = None
     app_conversation_start_task: AppConversationStartTaskServiceInjector | None = None
     app_conversation: AppConversationServiceInjector | None = None
+    pending_message: PendingMessageServiceInjector | None = None
     user: UserContextInjector | None = None
     jwt: JwtServiceInjector | None = None
     httpx: HttpxClientInjector = Field(default_factory=HttpxClientInjector)
@@ -280,6 +285,13 @@ def config_from_env() -> AppServerConfig:
             tavily_api_key=tavily_api_key
         )
 
+    if config.pending_message is None:
+        from openhands.app_server.pending_messages.pending_message_service import (
+            SQLPendingMessageServiceInjector,
+        )
+
+        config.pending_message = SQLPendingMessageServiceInjector()
+
     if config.user is None:
         config.user = AuthUserContextInjector()
 
@@ -358,6 +370,14 @@ def get_app_conversation_service(
     return injector.context(state, request)
 
 
+def get_pending_message_service(
+    state: InjectorState, request: Request | None = None
+) -> AsyncContextManager[PendingMessageService]:
+    injector = get_global_config().pending_message
+    assert injector is not None
+    return injector.context(state, request)
+
+
 def get_user_context(
     state: InjectorState, request: Request | None = None
 ) -> AsyncContextManager[UserContext]:
@@ -433,6 +453,12 @@ def depends_app_conversation_service():
     return Depends(injector.depends)
 
 
+def depends_pending_message_service():
+    injector = get_global_config().pending_message
+    assert injector is not None
+    return Depends(injector.depends)
+
+
 def depends_user_context():
     injector = get_global_config().user
     assert injector is not None

openhands/app_server/pending_messages/__init__.py

@@ -0,0 +1,21 @@
+"""Pending messages module for server-side message queuing."""
+
+from openhands.app_server.pending_messages.pending_message_models import (
+    PendingMessage,
+    PendingMessageResponse,
+)
+from openhands.app_server.pending_messages.pending_message_service import (
+    PendingMessageService,
+    PendingMessageServiceInjector,
+    SQLPendingMessageService,
+    SQLPendingMessageServiceInjector,
+)
+
+__all__ = [
+    'PendingMessage',
+    'PendingMessageResponse',
+    'PendingMessageService',
+    'PendingMessageServiceInjector',
+    'SQLPendingMessageService',
+    'SQLPendingMessageServiceInjector',
+]

openhands/app_server/pending_messages/pending_message_models.py

@@ -0,0 +1,32 @@
+"""Models for pending message queue functionality."""
+
+from datetime import datetime
+from uuid import uuid4
+
+from pydantic import BaseModel, Field
+
+from openhands.agent_server.models import ImageContent, TextContent
+from openhands.agent_server.utils import utc_now
+
+
+class PendingMessage(BaseModel):
+    """A message queued for delivery when conversation becomes ready.
+
+    Pending messages are stored in the database and delivered to the agent_server
+    when the conversation transitions to READY status. Messages are deleted after
+    processing, regardless of success or failure.
+    """
+
+    id: str = Field(default_factory=lambda: str(uuid4()))
+    conversation_id: str  # Can be task-{uuid} or real conversation UUID
+    role: str = 'user'
+    content: list[TextContent | ImageContent]
+    created_at: datetime = Field(default_factory=utc_now)
+
+
+class PendingMessageResponse(BaseModel):
+    """Response when queueing a pending message."""
+
+    id: str
+    queued: bool
+    position: int = Field(description='Position in the queue (1-based)')

openhands/app_server/pending_messages/pending_message_router.py

@@ -0,0 +1,104 @@
+"""REST API router for pending messages."""
+
+import logging
+
+from fastapi import APIRouter, HTTPException, Request, status
+from pydantic import TypeAdapter, ValidationError
+
+from openhands.agent_server.models import ImageContent, TextContent
+from openhands.app_server.config import depends_pending_message_service
+from openhands.app_server.pending_messages.pending_message_models import (
+    PendingMessageResponse,
+)
+from openhands.app_server.pending_messages.pending_message_service import (
+    PendingMessageService,
+)
+from openhands.server.dependencies import get_dependencies
+
+logger = logging.getLogger(__name__)
+
+# Type adapter for validating content from request
+_content_type_adapter = TypeAdapter(list[TextContent | ImageContent])
+
+# Create router with authentication dependencies
+router = APIRouter(
+    prefix='/conversations/{conversation_id}/pending-messages',
+    tags=['Pending Messages'],
+    dependencies=get_dependencies(),
+)
+
+# Create dependency at module level
+pending_message_service_dependency = depends_pending_message_service()
+
+
+@router.post(
+    '', response_model=PendingMessageResponse, status_code=status.HTTP_201_CREATED
+)
+async def queue_pending_message(
+    conversation_id: str,
+    request: Request,
+    pending_service: PendingMessageService = pending_message_service_dependency,
+) -> PendingMessageResponse:
+    """Queue a message for delivery when conversation becomes ready.
+
+    This endpoint allows users to submit messages even when the conversation's
+    WebSocket connection is not yet established. Messages are stored server-side
+    and delivered automatically when the conversation transitions to READY status.
+
+    Args:
+        conversation_id: The conversation ID (can be task ID before conversation is ready)
+        request: The FastAPI request containing message content
+
+    Returns:
+        PendingMessageResponse with the message ID and queue position
+
+    Raises:
+        HTTPException 400: If the request body is invalid
+        HTTPException 429: If too many pending messages are queued (limit: 10)
+    """
+    try:
+        body = await request.json()
+    except Exception:
+        raise HTTPException(
+            status_code=status.HTTP_400_BAD_REQUEST,
+            detail='Invalid request body',
+        )
+
+    raw_content = body.get('content')
+    role = body.get('role', 'user')
+
+    if not raw_content or not isinstance(raw_content, list):
+        raise HTTPException(
+            status_code=status.HTTP_400_BAD_REQUEST,
+            detail='content must be a non-empty list',
+        )
+
+    # Validate and parse content into typed objects
+    try:
+        content = _content_type_adapter.validate_python(raw_content)
+    except ValidationError as e:
+        raise HTTPException(
+            status_code=status.HTTP_400_BAD_REQUEST,
+            detail=f'Invalid content format: {e}',
+        )
+
+    # Rate limit: max 10 pending messages per conversation
+    pending_count = await pending_service.count_pending_messages(conversation_id)
+    if pending_count >= 10:
+        raise HTTPException(
+            status_code=status.HTTP_429_TOO_MANY_REQUESTS,
+            detail='Too many pending messages. Maximum 10 messages per conversation.',
+        )
+
+    response = await pending_service.add_message(
+        conversation_id=conversation_id,
+        content=content,
+        role=role,
+    )
+
+    logger.info(
+        f'Queued pending message {response.id} for conversation {conversation_id} '
+        f'(position: {response.position})'
+    )
+
+    return response

openhands/app_server/pending_messages/pending_message_service.py

@@ -0,0 +1,200 @@
+"""Service for managing pending messages in SQL database."""
+
+from abc import ABC, abstractmethod
+from dataclasses import dataclass
+from typing import AsyncGenerator
+
+from fastapi import Request
+from pydantic import TypeAdapter
+from sqlalchemy import JSON, Column, String, func, select
+from sqlalchemy.ext.asyncio import AsyncSession
+
+from openhands.agent_server.models import ImageContent, TextContent
+from openhands.app_server.pending_messages.pending_message_models import (
+    PendingMessage,
+    PendingMessageResponse,
+)
+from openhands.app_server.services.injector import Injector, InjectorState
+from openhands.app_server.utils.sql_utils import Base, UtcDateTime
+from openhands.sdk.utils.models import DiscriminatedUnionMixin
+
+# Type adapter for deserializing content from JSON
+_content_type_adapter = TypeAdapter(list[TextContent | ImageContent])
+
+
+class StoredPendingMessage(Base):  # type: ignore
+    """SQLAlchemy model for pending messages."""
+
+    __tablename__ = 'pending_messages'
+    id = Column(String, primary_key=True)
+    conversation_id = Column(String, nullable=False, index=True)
+    role = Column(String(20), nullable=False, default='user')
+    content = Column(JSON, nullable=False)
+    created_at = Column(UtcDateTime, server_default=func.now(), index=True)
+
+
+class PendingMessageService(ABC):
+    """Abstract service for managing pending messages."""
+
+    @abstractmethod
+    async def add_message(
+        self,
+        conversation_id: str,
+        content: list[TextContent | ImageContent],
+        role: str = 'user',
+    ) -> PendingMessageResponse:
+        """Queue a message for delivery when conversation becomes ready."""
+
+    @abstractmethod
+    async def get_pending_messages(self, conversation_id: str) -> list[PendingMessage]:
+        """Get all pending messages for a conversation, ordered by created_at."""
+
+    @abstractmethod
+    async def count_pending_messages(self, conversation_id: str) -> int:
+        """Count pending messages for a conversation."""
+
+    @abstractmethod
+    async def delete_messages_for_conversation(self, conversation_id: str) -> int:
+        """Delete all pending messages for a conversation, returning count deleted."""
+
+    @abstractmethod
+    async def update_conversation_id(
+        self, old_conversation_id: str, new_conversation_id: str
+    ) -> int:
+        """Update conversation_id when task-id transitions to real conversation-id.
+
+        Returns the number of messages updated.
+        """
+
+
+@dataclass
+class SQLPendingMessageService(PendingMessageService):
+    """SQL implementation of PendingMessageService."""
+
+    db_session: AsyncSession
+
+    async def add_message(
+        self,
+        conversation_id: str,
+        content: list[TextContent | ImageContent],
+        role: str = 'user',
+    ) -> PendingMessageResponse:
+        """Queue a message for delivery when conversation becomes ready."""
+        # Create the pending message
+        pending_message = PendingMessage(
+            conversation_id=conversation_id,
+            role=role,
+            content=content,
+        )
+
+        # Count existing pending messages for position
+        count_stmt = select(func.count()).where(
+            StoredPendingMessage.conversation_id == conversation_id
+        )
+        result = await self.db_session.execute(count_stmt)
+        position = result.scalar() or 0
+
+        # Serialize content to JSON-compatible format for storage
+        content_json = [item.model_dump() for item in content]
+
+        # Store in database
+        stored_message = StoredPendingMessage(
+            id=str(pending_message.id),
+            conversation_id=conversation_id,
+            role=role,
+            content=content_json,
+            created_at=pending_message.created_at,
+        )
+        self.db_session.add(stored_message)
+        await self.db_session.commit()
+
+        return PendingMessageResponse(
+            id=pending_message.id,
+            queued=True,
+            position=position + 1,
+        )
+
+    async def get_pending_messages(self, conversation_id: str) -> list[PendingMessage]:
+        """Get all pending messages for a conversation, ordered by created_at."""
+        stmt = (
+            select(StoredPendingMessage)
+            .where(StoredPendingMessage.conversation_id == conversation_id)
+            .order_by(StoredPendingMessage.created_at.asc())
+        )
+        result = await self.db_session.execute(stmt)
+        stored_messages = result.scalars().all()
+
+        return [
+            PendingMessage(
+                id=msg.id,
+                conversation_id=msg.conversation_id,
+                role=msg.role,
+                content=_content_type_adapter.validate_python(msg.content),
+                created_at=msg.created_at,
+            )
+            for msg in stored_messages
+        ]
+
+    async def count_pending_messages(self, conversation_id: str) -> int:
+        """Count pending messages for a conversation."""
+        count_stmt = select(func.count()).where(
+            StoredPendingMessage.conversation_id == conversation_id
+        )
+        result = await self.db_session.execute(count_stmt)
+        return result.scalar() or 0
+
+    async def delete_messages_for_conversation(self, conversation_id: str) -> int:
+        """Delete all pending messages for a conversation, returning count deleted."""
+        stmt = select(StoredPendingMessage).where(
+            StoredPendingMessage.conversation_id == conversation_id
+        )
+        result = await self.db_session.execute(stmt)
+        stored_messages = result.scalars().all()
+
+        count = len(stored_messages)
+        for msg in stored_messages:
+            await self.db_session.delete(msg)
+
+        if count > 0:
+            await self.db_session.commit()
+
+        return count
+
+    async def update_conversation_id(
+        self, old_conversation_id: str, new_conversation_id: str
+    ) -> int:
+        """Update conversation_id when task-id transitions to real conversation-id."""
+        stmt = select(StoredPendingMessage).where(
+            StoredPendingMessage.conversation_id == old_conversation_id
+        )
+        result = await self.db_session.execute(stmt)
+        stored_messages = result.scalars().all()
+
+        count = len(stored_messages)
+        for msg in stored_messages:
+            msg.conversation_id = new_conversation_id
+
+        if count > 0:
+            await self.db_session.commit()
+
+        return count
+
+
+class PendingMessageServiceInjector(
+    DiscriminatedUnionMixin, Injector[PendingMessageService], ABC
+):
+    """Abstract injector for PendingMessageService."""
+
+    pass
+
+
+class SQLPendingMessageServiceInjector(PendingMessageServiceInjector):
+    """SQL-based injector for PendingMessageService."""
+
+    async def inject(
+        self, state: InjectorState, request: Request | None = None
+    ) -> AsyncGenerator[PendingMessageService, None]:
+        from openhands.app_server.config import get_db_session
+
+        async with get_db_session(state) as db_session:
+            yield SQLPendingMessageService(db_session=db_session)

openhands/app_server/v1_router.py

@@ -5,6 +5,9 @@ from openhands.app_server.event import event_router
 from openhands.app_server.event_callback import (
     webhook_router,
 )
+from openhands.app_server.pending_messages.pending_message_router import (
+    router as pending_message_router,
+)
 from openhands.app_server.sandbox import sandbox_router, sandbox_spec_router
 from openhands.app_server.user import user_router
 from openhands.app_server.web_client import web_client_router
@@ -13,6 +16,7 @@ from openhands.app_server.web_client import web_client_router
 router = APIRouter(prefix='/api/v1')
 router.include_router(event_router.router)
 router.include_router(app_conversation_router.router)
+router.include_router(pending_message_router)
 router.include_router(sandbox_router.router)
 router.include_router(sandbox_spec_router.router)
 router.include_router(user_router.router)

tests/unit/app_server/test_live_status_app_conversation_service.py

@@ -80,6 +80,7 @@ class TestLiveStatusAppConversationService:
         self.mock_event_callback_service = Mock()
         self.mock_event_service = Mock()
         self.mock_httpx_client = Mock()
+        self.mock_pending_message_service = Mock()
 
         # Create service instance
         self.service = LiveStatusAppConversationService(
@@ -92,6 +93,7 @@ class TestLiveStatusAppConversationService:
             sandbox_service=self.mock_sandbox_service,
             sandbox_spec_service=self.mock_sandbox_spec_service,
             jwt_service=self.mock_jwt_service,
+            pending_message_service=self.mock_pending_message_service,
             sandbox_startup_timeout=30,
             sandbox_startup_poll_frequency=1,
             max_num_conversations_per_sandbox=20,
@@ -2329,6 +2331,7 @@ class TestPluginHandling:
         self.mock_event_callback_service = Mock()
         self.mock_event_service = Mock()
         self.mock_httpx_client = Mock()
+        self.mock_pending_message_service = Mock()
 
         # Create service instance
         self.service = LiveStatusAppConversationService(
@@ -2341,6 +2344,7 @@ class TestPluginHandling:
             sandbox_service=self.mock_sandbox_service,
             sandbox_spec_service=self.mock_sandbox_spec_service,
             jwt_service=self.mock_jwt_service,
+            pending_message_service=self.mock_pending_message_service,
             sandbox_startup_timeout=30,
             sandbox_startup_poll_frequency=1,
             max_num_conversations_per_sandbox=20,

tests/unit/app_server/test_pending_message_router.py

@@ -0,0 +1,227 @@
+"""Unit tests for the pending_message_router endpoints.
+
+This module tests the queue_pending_message endpoint,
+focusing on request validation and rate limiting.
+"""
+
+from unittest.mock import AsyncMock, MagicMock
+from uuid import uuid4
+
+import pytest
+from fastapi import HTTPException, status
+
+from openhands.agent_server.models import TextContent
+from openhands.app_server.pending_messages.pending_message_models import (
+    PendingMessageResponse,
+)
+from openhands.app_server.pending_messages.pending_message_router import (
+    queue_pending_message,
+)
+
+
+def _make_mock_service(
+    add_message_return=None,
+    count_pending_messages_return=0,
+):
+    """Create a mock PendingMessageService for testing."""
+    service = MagicMock()
+    service.add_message = AsyncMock(return_value=add_message_return)
+    service.count_pending_messages = AsyncMock(
+        return_value=count_pending_messages_return
+    )
+    return service
+
+
+def _make_mock_request(body: dict):
+    """Create a mock FastAPI Request with given JSON body."""
+    request = MagicMock()
+    request.json = AsyncMock(return_value=body)
+    return request
+
+
+@pytest.mark.asyncio
+class TestQueuePendingMessage:
+    """Test suite for queue_pending_message endpoint."""
+
+    async def test_queues_message_successfully(self):
+        """Test that a valid message is queued successfully."""
+        # Arrange
+        conversation_id = f'task-{uuid4().hex}'
+        raw_content = [{'type': 'text', 'text': 'Hello, world!'}]
+        expected_response = PendingMessageResponse(
+            id=str(uuid4()),
+            queued=True,
+            position=1,
+        )
+        mock_service = _make_mock_service(
+            add_message_return=expected_response,
+            count_pending_messages_return=0,
+        )
+        mock_request = _make_mock_request({'content': raw_content, 'role': 'user'})
+
+        # Act
+        result = await queue_pending_message(
+            conversation_id=conversation_id,
+            request=mock_request,
+            pending_service=mock_service,
+        )
+
+        # Assert
+        assert result == expected_response
+        mock_service.add_message.assert_called_once()
+        call_kwargs = mock_service.add_message.call_args.kwargs
+        assert call_kwargs['conversation_id'] == conversation_id
+        assert call_kwargs['role'] == 'user'
+        # Content should be parsed into typed objects
+        assert len(call_kwargs['content']) == 1
+        assert isinstance(call_kwargs['content'][0], TextContent)
+        assert call_kwargs['content'][0].text == 'Hello, world!'
+
+    async def test_uses_default_role_when_not_provided(self):
+        """Test that 'user' role is used by default."""
+        # Arrange
+        conversation_id = f'task-{uuid4().hex}'
+        raw_content = [{'type': 'text', 'text': 'Test message'}]
+        expected_response = PendingMessageResponse(
+            id=str(uuid4()),
+            queued=True,
+            position=1,
+        )
+        mock_service = _make_mock_service(
+            add_message_return=expected_response,
+            count_pending_messages_return=0,
+        )
+        mock_request = _make_mock_request({'content': raw_content})
+
+        # Act
+        await queue_pending_message(
+            conversation_id=conversation_id,
+            request=mock_request,
+            pending_service=mock_service,
+        )
+
+        # Assert
+        mock_service.add_message.assert_called_once()
+        call_kwargs = mock_service.add_message.call_args.kwargs
+        assert call_kwargs['conversation_id'] == conversation_id
+        assert call_kwargs['role'] == 'user'
+        assert isinstance(call_kwargs['content'][0], TextContent)
+
+    async def test_returns_400_for_invalid_json_body(self):
+        """Test that invalid JSON body returns 400 Bad Request."""
+        # Arrange
+        conversation_id = f'task-{uuid4().hex}'
+        mock_service = _make_mock_service()
+        mock_request = MagicMock()
+        mock_request.json = AsyncMock(side_effect=Exception('Invalid JSON'))
+
+        # Act & Assert
+        with pytest.raises(HTTPException) as exc_info:
+            await queue_pending_message(
+                conversation_id=conversation_id,
+                request=mock_request,
+                pending_service=mock_service,
+            )
+
+        assert exc_info.value.status_code == status.HTTP_400_BAD_REQUEST
+        assert 'Invalid request body' in exc_info.value.detail
+
+    async def test_returns_400_when_content_is_missing(self):
+        """Test that missing content returns 400 Bad Request."""
+        # Arrange
+        conversation_id = f'task-{uuid4().hex}'
+        mock_service = _make_mock_service()
+        mock_request = _make_mock_request({'role': 'user'})
+
+        # Act & Assert
+        with pytest.raises(HTTPException) as exc_info:
+            await queue_pending_message(
+                conversation_id=conversation_id,
+                request=mock_request,
+                pending_service=mock_service,
+            )
+
+        assert exc_info.value.status_code == status.HTTP_400_BAD_REQUEST
+        assert 'content must be a non-empty list' in exc_info.value.detail
+
+    async def test_returns_400_when_content_is_not_a_list(self):
+        """Test that non-list content returns 400 Bad Request."""
+        # Arrange
+        conversation_id = f'task-{uuid4().hex}'
+        mock_service = _make_mock_service()
+        mock_request = _make_mock_request({'content': 'not a list'})
+
+        # Act & Assert
+        with pytest.raises(HTTPException) as exc_info:
+            await queue_pending_message(
+                conversation_id=conversation_id,
+                request=mock_request,
+                pending_service=mock_service,
+            )
+
+        assert exc_info.value.status_code == status.HTTP_400_BAD_REQUEST
+        assert 'content must be a non-empty list' in exc_info.value.detail
+
+    async def test_returns_400_when_content_is_empty_list(self):
+        """Test that empty list content returns 400 Bad Request."""
+        # Arrange
+        conversation_id = f'task-{uuid4().hex}'
+        mock_service = _make_mock_service()
+        mock_request = _make_mock_request({'content': []})
+
+        # Act & Assert
+        with pytest.raises(HTTPException) as exc_info:
+            await queue_pending_message(
+                conversation_id=conversation_id,
+                request=mock_request,
+                pending_service=mock_service,
+            )
+
+        assert exc_info.value.status_code == status.HTTP_400_BAD_REQUEST
+        assert 'content must be a non-empty list' in exc_info.value.detail
+
+    async def test_returns_429_when_rate_limit_exceeded(self):
+        """Test that exceeding rate limit returns 429 Too Many Requests."""
+        # Arrange
+        conversation_id = f'task-{uuid4().hex}'
+        raw_content = [{'type': 'text', 'text': 'Test message'}]
+        mock_service = _make_mock_service(count_pending_messages_return=10)
+        mock_request = _make_mock_request({'content': raw_content})
+
+        # Act & Assert
+        with pytest.raises(HTTPException) as exc_info:
+            await queue_pending_message(
+                conversation_id=conversation_id,
+                request=mock_request,
+                pending_service=mock_service,
+            )
+
+        assert exc_info.value.status_code == status.HTTP_429_TOO_MANY_REQUESTS
+        assert 'Maximum 10 messages' in exc_info.value.detail
+
+    async def test_allows_up_to_10_messages(self):
+        """Test that 9 existing messages still allows adding one more."""
+        # Arrange
+        conversation_id = f'task-{uuid4().hex}'
+        raw_content = [{'type': 'text', 'text': 'Test message'}]
+        expected_response = PendingMessageResponse(
+            id=str(uuid4()),
+            queued=True,
+            position=10,
+        )
+        mock_service = _make_mock_service(
+            add_message_return=expected_response,
+            count_pending_messages_return=9,
+        )
+        mock_request = _make_mock_request({'content': raw_content})
+
+        # Act
+        result = await queue_pending_message(
+            conversation_id=conversation_id,
+            request=mock_request,
+            pending_service=mock_service,
+        )
+
+        # Assert
+        assert result == expected_response
+        mock_service.add_message.assert_called_once()

tests/unit/app_server/test_pending_message_service.py

@@ -0,0 +1,309 @@
+"""Tests for SQLPendingMessageService.
+
+This module tests the SQL implementation of PendingMessageService,
+covering message queuing, retrieval, counting, deletion, and
+conversation_id updates using SQLite as a mock database.
+"""
+
+from typing import AsyncGenerator
+from uuid import uuid4
+
+import pytest
+from sqlalchemy.ext.asyncio import AsyncSession, async_sessionmaker, create_async_engine
+from sqlalchemy.pool import StaticPool
+
+from openhands.agent_server.models import TextContent
+from openhands.app_server.pending_messages.pending_message_models import (
+    PendingMessageResponse,
+)
+from openhands.app_server.pending_messages.pending_message_service import (
+    SQLPendingMessageService,
+)
+from openhands.app_server.utils.sql_utils import Base
+
+
+@pytest.fixture
+async def async_engine():
+    """Create an async SQLite engine for testing."""
+    engine = create_async_engine(
+        'sqlite+aiosqlite:///:memory:',
+        poolclass=StaticPool,
+        connect_args={'check_same_thread': False},
+        echo=False,
+    )
+
+    async with engine.begin() as conn:
+        await conn.run_sync(Base.metadata.create_all)
+
+    yield engine
+
+    await engine.dispose()
+
+
+@pytest.fixture
+async def async_session(async_engine) -> AsyncGenerator[AsyncSession, None]:
+    """Create an async session for testing."""
+    async_session_maker = async_sessionmaker(
+        async_engine, class_=AsyncSession, expire_on_commit=False
+    )
+
+    async with async_session_maker() as db_session:
+        yield db_session
+
+
+@pytest.fixture
+def service(async_session) -> SQLPendingMessageService:
+    """Create a SQLPendingMessageService instance for testing."""
+    return SQLPendingMessageService(db_session=async_session)
+
+
+@pytest.fixture
+def sample_content() -> list[TextContent]:
+    """Create sample message content for testing."""
+    return [TextContent(text='Hello, this is a test message')]
+
+
+class TestSQLPendingMessageService:
+    """Test suite for SQLPendingMessageService."""
+
+    @pytest.mark.asyncio
+    async def test_add_message_creates_message_with_correct_data(
+        self,
+        service: SQLPendingMessageService,
+        sample_content: list[TextContent],
+    ):
+        """Test that add_message creates a message with the expected fields."""
+        # Arrange
+        conversation_id = f'task-{uuid4().hex}'
+
+        # Act
+        response = await service.add_message(
+            conversation_id=conversation_id,
+            content=sample_content,
+            role='user',
+        )
+
+        # Assert
+        assert isinstance(response, PendingMessageResponse)
+        assert response.queued is True
+        assert response.id is not None
+
+        # Verify the message was stored correctly
+        messages = await service.get_pending_messages(conversation_id)
+        assert len(messages) == 1
+        assert messages[0].conversation_id == conversation_id
+        assert len(messages[0].content) == 1
+        assert isinstance(messages[0].content[0], TextContent)
+        assert messages[0].content[0].text == sample_content[0].text
+        assert messages[0].role == 'user'
+        assert messages[0].created_at is not None
+
+    @pytest.mark.asyncio
+    async def test_add_message_returns_correct_queue_position(
+        self,
+        service: SQLPendingMessageService,
+        sample_content: list[TextContent],
+    ):
+        """Test that queue position increments correctly for each message."""
+        # Arrange
+        conversation_id = f'task-{uuid4().hex}'
+
+        # Act - Add three messages
+        response1 = await service.add_message(conversation_id, sample_content)
+        response2 = await service.add_message(conversation_id, sample_content)
+        response3 = await service.add_message(conversation_id, sample_content)
+
+        # Assert
+        assert response1.position == 1
+        assert response2.position == 2
+        assert response3.position == 3
+
+    @pytest.mark.asyncio
+    async def test_get_pending_messages_returns_messages_ordered_by_created_at(
+        self,
+        service: SQLPendingMessageService,
+    ):
+        """Test that messages are returned in chronological order."""
+        # Arrange
+        conversation_id = f'task-{uuid4().hex}'
+        contents = [
+            [TextContent(text='First message')],
+            [TextContent(text='Second message')],
+            [TextContent(text='Third message')],
+        ]
+
+        for content in contents:
+            await service.add_message(conversation_id, content)
+
+        # Act
+        messages = await service.get_pending_messages(conversation_id)
+
+        # Assert
+        assert len(messages) == 3
+        assert messages[0].content[0].text == 'First message'
+        assert messages[1].content[0].text == 'Second message'
+        assert messages[2].content[0].text == 'Third message'
+
+    @pytest.mark.asyncio
+    async def test_get_pending_messages_returns_empty_list_when_none_exist(
+        self,
+        service: SQLPendingMessageService,
+    ):
+        """Test that an empty list is returned for a conversation with no messages."""
+        # Arrange
+        conversation_id = f'task-{uuid4().hex}'
+
+        # Act
+        messages = await service.get_pending_messages(conversation_id)
+
+        # Assert
+        assert messages == []
+
+    @pytest.mark.asyncio
+    async def test_count_pending_messages_returns_correct_count(
+        self,
+        service: SQLPendingMessageService,
+        sample_content: list[TextContent],
+    ):
+        """Test that count_pending_messages returns the correct number."""
+        # Arrange
+        conversation_id = f'task-{uuid4().hex}'
+        other_conversation_id = f'task-{uuid4().hex}'
+
+        # Add 3 messages to first conversation
+        for _ in range(3):
+            await service.add_message(conversation_id, sample_content)
+
+        # Add 2 messages to second conversation
+        for _ in range(2):
+            await service.add_message(other_conversation_id, sample_content)
+
+        # Act
+        count1 = await service.count_pending_messages(conversation_id)
+        count2 = await service.count_pending_messages(other_conversation_id)
+        count_empty = await service.count_pending_messages('nonexistent')
+
+        # Assert
+        assert count1 == 3
+        assert count2 == 2
+        assert count_empty == 0
+
+    @pytest.mark.asyncio
+    async def test_delete_messages_for_conversation_removes_all_messages(
+        self,
+        service: SQLPendingMessageService,
+        sample_content: list[TextContent],
+    ):
+        """Test that delete_messages_for_conversation removes all messages and returns count."""
+        # Arrange
+        conversation_id = f'task-{uuid4().hex}'
+        other_conversation_id = f'task-{uuid4().hex}'
+
+        # Add messages to both conversations
+        for _ in range(3):
+            await service.add_message(conversation_id, sample_content)
+        await service.add_message(other_conversation_id, sample_content)
+
+        # Act
+        deleted_count = await service.delete_messages_for_conversation(conversation_id)
+
+        # Assert
+        assert deleted_count == 3
+        assert await service.count_pending_messages(conversation_id) == 0
+        # Other conversation should be unaffected
+        assert await service.count_pending_messages(other_conversation_id) == 1
+
+    @pytest.mark.asyncio
+    async def test_delete_messages_for_conversation_returns_zero_when_none_exist(
+        self,
+        service: SQLPendingMessageService,
+    ):
+        """Test that deleting from nonexistent conversation returns 0."""
+        # Arrange
+        conversation_id = f'task-{uuid4().hex}'
+
+        # Act
+        deleted_count = await service.delete_messages_for_conversation(conversation_id)
+
+        # Assert
+        assert deleted_count == 0
+
+    @pytest.mark.asyncio
+    async def test_update_conversation_id_updates_all_matching_messages(
+        self,
+        service: SQLPendingMessageService,
+        sample_content: list[TextContent],
+    ):
+        """Test that update_conversation_id updates all messages with the old ID."""
+        # Arrange
+        old_conversation_id = f'task-{uuid4().hex}'
+        new_conversation_id = str(uuid4())
+        unrelated_conversation_id = f'task-{uuid4().hex}'
+
+        # Add messages to old conversation
+        for _ in range(3):
+            await service.add_message(old_conversation_id, sample_content)
+
+        # Add message to unrelated conversation
+        await service.add_message(unrelated_conversation_id, sample_content)
+
+        # Act
+        updated_count = await service.update_conversation_id(
+            old_conversation_id, new_conversation_id
+        )
+
+        # Assert
+        assert updated_count == 3
+
+        # Verify old conversation has no messages
+        assert await service.count_pending_messages(old_conversation_id) == 0
+
+        # Verify new conversation has all messages
+        messages = await service.get_pending_messages(new_conversation_id)
+        assert len(messages) == 3
+        for msg in messages:
+            assert msg.conversation_id == new_conversation_id
+
+        # Verify unrelated conversation is unchanged
+        assert await service.count_pending_messages(unrelated_conversation_id) == 1
+
+    @pytest.mark.asyncio
+    async def test_update_conversation_id_returns_zero_when_no_match(
+        self,
+        service: SQLPendingMessageService,
+    ):
+        """Test that updating nonexistent conversation_id returns 0."""
+        # Arrange
+        old_conversation_id = f'task-{uuid4().hex}'
+        new_conversation_id = str(uuid4())
+
+        # Act
+        updated_count = await service.update_conversation_id(
+            old_conversation_id, new_conversation_id
+        )
+
+        # Assert
+        assert updated_count == 0
+
+    @pytest.mark.asyncio
+    async def test_messages_are_isolated_between_conversations(
+        self,
+        service: SQLPendingMessageService,
+    ):
+        """Test that operations on one conversation don't affect others."""
+        # Arrange
+        conv1 = f'task-{uuid4().hex}'
+        conv2 = f'task-{uuid4().hex}'
+
+        await service.add_message(conv1, [TextContent(text='Conv1 msg')])
+        await service.add_message(conv2, [TextContent(text='Conv2 msg')])
+
+        # Act
+        messages1 = await service.get_pending_messages(conv1)
+        messages2 = await service.get_pending_messages(conv2)
+
+        # Assert
+        assert len(messages1) == 1
+        assert len(messages2) == 1
+        assert messages1[0].content[0].text == 'Conv1 msg'
+        assert messages2[0].content[0].text == 'Conv2 msg'

tests/unit/server/data_models/test_conversation.py

@@ -2187,6 +2187,7 @@ async def test_delete_v1_conversation_with_sub_conversations():
         sandbox_service=mock_sandbox_service,
         sandbox_spec_service=MagicMock(),
         jwt_service=MagicMock(),
+        pending_message_service=MagicMock(),
         sandbox_startup_timeout=120,
         sandbox_startup_poll_frequency=2,
         max_num_conversations_per_sandbox=20,
@@ -2311,6 +2312,7 @@ async def test_delete_v1_conversation_with_no_sub_conversations():
         sandbox_service=mock_sandbox_service,
         sandbox_spec_service=MagicMock(),
         jwt_service=MagicMock(),
+        pending_message_service=MagicMock(),
         sandbox_startup_timeout=120,
         sandbox_startup_poll_frequency=2,
         max_num_conversations_per_sandbox=20,
@@ -2465,6 +2467,7 @@ async def test_delete_v1_conversation_sub_conversation_deletion_error():
         sandbox_service=mock_sandbox_service,
         sandbox_spec_service=MagicMock(),
         jwt_service=MagicMock(),
+        pending_message_service=MagicMock(),
         sandbox_startup_timeout=120,
         sandbox_startup_poll_frequency=2,
         max_num_conversations_per_sandbox=20,