feat: implement file attachment system with session management and event handling

backend/application/chat/utilities/file_utils.py

@@ -455,5 +455,6 @@ def build_files_manifest(session_context: Dict[str, Any]) -> Optional[Dict[str,
             f"{file_list}\n\n"
             "(You can ask to open or analyze any of these by name. "
             "Large contents are not fully in this prompt unless user or tools provided excerpts.)"
+            "The user may refer to these files in their requests as session files or attachments."
         )
     }

backend/tests/test_attach_file_flow.py

@@ -0,0 +1,209 @@
+import base64
+import uuid
+import pytest
+
+from application.chat.service import ChatService
+from modules.file_storage.manager import FileManager
+from modules.file_storage.mock_s3_client import MockS3StorageClient
+
+
+class FakeLLM:
+    async def call_plain(self, model_name, messages, temperature=0.7):
+        return "ok"
+
+    async def call_with_tools(self, model_name, messages, tools_schema, tool_choice="auto", temperature=0.7):
+        from interfaces.llm import LLMResponse
+        return LLMResponse(content="ok", tool_calls=None, model_used=model_name)
+
+    async def call_with_rag(self, model_name, messages, data_sources, user_email, temperature=0.7):
+        return "ok"
+
+    async def call_with_rag_and_tools(self, model_name, messages, data_sources, tools_schema, user_email, tool_choice="auto", temperature=0.7):
+        from interfaces.llm import LLMResponse
+        return LLMResponse(content="ok", tool_calls=None, model_used=model_name)
+
+
+@pytest.fixture
+def file_manager():
+    # Use in-process mock S3 for deterministic tests
+    return FileManager(s3_client=MockS3StorageClient())
+
+
+@pytest.fixture
+def chat_service(file_manager):
+    # Minimal ChatService wiring for file/session operations
+    return ChatService(llm=FakeLLM(), file_manager=file_manager)
+
+
+@pytest.mark.asyncio
+async def test_handle_attach_file_success_creates_session_and_emits_update(chat_service, file_manager):
+    user_email = "user1@example.com"
+    session_id = uuid.uuid4()
+
+    # Seed a file into the mock storage for this user
+    filename = "report.txt"
+    content_b64 = base64.b64encode(b"hello world").decode()
+    upload_meta = await file_manager.s3_client.upload_file(
+        user_email=user_email,
+        filename=filename,
+        content_base64=content_b64,
+        content_type="text/plain",
+        tags={"source": "user"},
+        source_type="user",
+    )
+    s3_key = upload_meta["key"]
+
+    updates = []
+
+    async def capture_update(msg):
+        updates.append(msg)
+
+    # Act: attach the file to a brand new session (auto-creates session)
+    resp = await chat_service.handle_attach_file(
+        session_id=session_id,
+        s3_key=s3_key,
+        user_email=user_email,
+        update_callback=capture_update,
+    )
+
+    # Assert: success response and files_update emitted
+    assert resp.get("type") == "file_attach"
+    assert resp.get("success") is True
+    assert resp.get("filename") == filename
+
+    assert any(
+        u.get("type") == "intermediate_update" and u.get("update_type") == "files_update"
+        for u in updates
+    ), "Expected a files_update intermediate update to be emitted"
+
+    # Session context should include the file by filename
+    session = chat_service.sessions.get(session_id)
+    assert session is not None
+    assert filename in session.context.get("files", {})
+    assert session.context["files"][filename]["key"] == s3_key
+
+
+@pytest.mark.asyncio
+async def test_handle_attach_file_not_found_returns_error(chat_service):
+    user_email = "user1@example.com"
+    session_id = uuid.uuid4()
+
+    # Non-existent S3 key for the same user
+    bad_key = f"users/{user_email}/uploads/does_not_exist_12345.txt"
+    resp = await chat_service.handle_attach_file(
+        session_id=session_id,
+        s3_key=bad_key,
+        user_email=user_email,
+        update_callback=None,
+    )
+
+    assert resp.get("type") == "file_attach"
+    assert resp.get("success") is False
+    assert "File not found" in resp.get("error", "")
+
+
+@pytest.mark.asyncio
+async def test_handle_attach_file_unauthorized_other_user_key(chat_service, file_manager):
+    # Upload under user1
+    owner_email = "owner@example.com"
+    other_email = "other@example.com"
+    session_id = uuid.uuid4()
+
+    filename = "secret.pdf"
+    content_b64 = base64.b64encode(b"top-secret").decode()
+    upload_meta = await file_manager.s3_client.upload_file(
+        user_email=owner_email,
+        filename=filename,
+        content_base64=content_b64,
+        content_type="application/pdf",
+        tags={"source": "user"},
+        source_type="user",
+    )
+    s3_key = upload_meta["key"]
+
+    # Attempt to attach with a different user should fail
+    resp = await chat_service.handle_attach_file(
+        session_id=session_id,
+        s3_key=s3_key,
+        user_email=other_email,
+        update_callback=None,
+    )
+
+    assert resp.get("type") == "file_attach"
+    assert resp.get("success") is False
+    assert "Access denied" in resp.get("error", "")
+
+
+@pytest.mark.asyncio
+async def test_handle_reset_session_reinitializes(chat_service):
+    user_email = "user1@example.com"
+    session_id = uuid.uuid4()
+
+    # Create a session first
+    await chat_service.create_session(session_id, user_email)
+    assert chat_service.sessions.get(session_id) is not None
+
+    # Reset the session
+    resp = await chat_service.handle_reset_session(session_id=session_id, user_email=user_email)
+
+    assert resp.get("type") == "session_reset"
+    # After reset, a fresh active session should exist for the same id
+    new_session = chat_service.sessions.get(session_id)
+    assert new_session is not None
+    assert new_session.active is True
+
+
+@pytest.mark.asyncio
+async def test_handle_download_file_success_after_attach(chat_service, file_manager):
+    user_email = "user1@example.com"
+    session_id = uuid.uuid4()
+
+    # Upload and then attach to session
+    filename = "notes.md"
+    content_bytes = b"### Title\nSome content."
+    content_b64 = base64.b64encode(content_bytes).decode()
+    upload_meta = await file_manager.s3_client.upload_file(
+        user_email=user_email,
+        filename=filename,
+        content_base64=content_b64,
+        content_type="text/markdown",
+        tags={"source": "user"},
+        source_type="user",
+    )
+    s3_key = upload_meta["key"]
+
+    await chat_service.handle_attach_file(
+        session_id=session_id,
+        s3_key=s3_key,
+        user_email=user_email,
+        update_callback=None,
+    )
+
+    # Act: download by filename (from session context)
+    resp = await chat_service.handle_download_file(
+        session_id=session_id,
+        filename=filename,
+        user_email=user_email,
+    )
+
+    assert resp.get("type") is not None
+    # content_base64 should match uploaded content
+    returned_b64 = resp.get("content_base64")
+    assert isinstance(returned_b64, str) and len(returned_b64) > 0
+    assert base64.b64decode(returned_b64) == content_bytes
+
+
+@pytest.mark.asyncio
+async def test_handle_download_file_not_in_session_returns_error(chat_service):
+    user_email = "user1@example.com"
+    session_id = uuid.uuid4()
+    filename = "missing.txt"
+
+    # No attach performed; should error that file isn't in session
+    resp = await chat_service.handle_download_file(
+        session_id=session_id,
+        filename=filename,
+        user_email=user_email,
+    )
+
+    assert resp.get("error") == "Session or file manager not available" or resp.get("error") == "File not found in session"

frontend/src/components/AllFilesView.jsx

@@ -17,7 +17,7 @@ import { useChat } from '../contexts/ChatContext'
 import { useWS } from '../contexts/WSContext'
 
 const AllFilesView = () => {
-  const { token, user: userEmail } = useChat()
+  const { token, user: userEmail, ensureSession, addSystemEvent, addPendingFileEvent, attachments } = useChat()
   const { sendMessage } = useWS()
   const [allFiles, setAllFiles] = useState([])
   const [filteredFiles, setFilteredFiles] = useState([])
@@ -211,17 +211,36 @@ const AllFilesView = () => {
     }
   }
 
-  const handleLoadToSession = async (file) => {
+  const handleAddToSession = async (file) => {
     try {
+      // Check if file is already attached
+      if (attachments.has(file.key)) {
+        addSystemEvent('file-attached', `'${file.filename}' is already in this session.`)
+        return
+      }
+
+      // Ensure session exists
+      await ensureSession()
+
+      // Add "attaching" system event and track it as pending
+      const eventId = addSystemEvent('file-attaching', `Adding '${file.filename}' to this session...`, {
+        fileId: file.key,
+        fileName: file.filename,
+        source: 'library'
+      })
+
+      // Track this as a pending file event
+      addPendingFileEvent(file.key, eventId)
+
+      // Send attach_file message (WebSocket handler will resolve the pending event)
       sendMessage({
         type: 'attach_file',
         s3_key: file.key,
         user: userEmail
       })
-      showNotification(`File "${file.filename}" loaded to current session`, 'success')
     } catch (error) {
-      console.error('Error loading file to session:', error)
-      showNotification('Failed to load file to session', 'error')
+      console.error('Error adding file to session:', error)
+      addSystemEvent('file-attach-error', `Failed to add '${file.filename}' to session: ${error.message}`)
     }
   }
 
@@ -380,9 +399,9 @@ const AllFilesView = () => {
                 {/* Action Buttons */}
                 <div className="flex items-center gap-2 flex-shrink-0">
                   <button
-                    onClick={() => handleLoadToSession(file)}
+                    onClick={() => handleAddToSession(file)}
                     className="p-2 rounded-lg bg-purple-600 hover:bg-purple-700 text-white transition-colors"
-                    title="Load to current session"
+                    title="Add to session"
                   >
                     <ArrowUpToLine className="w-4 h-4" />
                   </button>

frontend/src/components/Message.jsx

@@ -50,7 +50,7 @@ hljs.registerLanguage('sh', bash)
 const processFileReferences = (content) => {
   return content.replace(
     /@file\s+([^\s]+)/g,
-    '<span class="inline-flex items-center px-2 py-1 rounded-md bg-green-900/30 border border-green-500/30 text-green-400 text-sm font-medium">📎 @file $1</span>'
+    '<span class="inline-flex items-center px-2 py-1 rounded-md bg-green-900/30 border border-green-500/30 text-green-400 text-sm font-medium">@file $1</span>'
   )
 }
 
@@ -629,24 +629,24 @@ const renderContent = () => {
             </div>
           )}
 
-          {/* Result Section */}
-          {message.result && (
-            <div className="mb-2">
-              <div className={`border-l-4 pl-4 ${
-                message.status === 'failed' ? 'border-red-500' : 'border-green-500'
-              }`}>
-                <button
-                  onClick={() => setToolOutputCollapsed(!toolOutputCollapsed)}
-                  className={`w-full text-left text-sm font-semibold mb-2 flex items-center gap-2 transition-colors ${
-                    message.status === 'failed' 
-                      ? 'text-red-400 hover:text-red-300' 
-                      : 'text-green-400 hover:text-green-300'
-                  }`}
-                >
-                  <span className={`transform transition-transform duration-200 ${toolOutputCollapsed ? 'rotate-0' : 'rotate-90'}`}>
-                    ▶
-                  </span>
-                  {message.status === 'failed' ? 'Error Details' : 'Output Result'} {toolOutputCollapsed ? '(click to expand)' : ''}
+          {/* Result Section */}
+          {message.result && (
+            <div className="mb-2">
+              <div className={`border-l-4 pl-4 ${
+                message.status === 'failed' ? 'border-red-500' : 'border-green-500'
+              }`}>
+                <button
+                  onClick={() => setToolOutputCollapsed(!toolOutputCollapsed)}
+                  className={`w-full text-left text-sm font-semibold mb-2 flex items-center gap-2 transition-colors ${
+                    message.status === 'failed' 
+                      ? 'text-red-400 hover:text-red-300' 
+                      : 'text-green-400 hover:text-green-300'
+                  }`}
+                >
+                  <span className={`transform transition-transform duration-200 ${toolOutputCollapsed ? 'rotate-0' : 'rotate-90'}`}>
+                    ▶
+                  </span>
+                  {message.status === 'failed' ? 'Error Details' : 'Output Result'} {toolOutputCollapsed ? '(click to expand)' : ''}
                 </button>
 
                 {!toolOutputCollapsed && (
@@ -768,6 +768,31 @@ const renderContent = () => {
     }
 
     if (isUser || isSystem) {
+      // Handle file attachment system events
+      if (message.type === 'system' && message.subtype) {
+        switch (message.subtype) {
+          case 'file-attaching':
+            return (
+              <div className="text-blue-300 italic">
+                {message.text}
+              </div>
+            )
+          case 'file-attached':
+            return (
+              <div className="text-green-300">
+                {message.text}
+              </div>
+            )
+          case 'file-attach-error':
+            return (
+              <div className="text-red-300">
+                {message.text}
+              </div>
+            )
+          default:
+            return <div className="text-gray-200">{message.content}</div>
+        }
+      }
       return <div className="text-gray-200">{message.content}</div>
     }