diff --git a/CHANGELOG.md b/CHANGELOG.md
index b0725af08..e14eb5746 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -16,6 +16,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 - [EE] Added mermaid diagram rendering to Ask Sourcebot answers, with pan/zoom, copy/export, in-thread deep links, and an interleaved right-panel view. [#1369](https://github.com/sourcebot-dev/sourcebot/pull/1369)
 - [EE] Added a context-window usage gauge to the Ask Sourcebot chat details, showing how much of the selected model's context window each turn occupies. Window sizes are resolved from the models.dev catalog. [#1370](https://github.com/sourcebot-dev/sourcebot/pull/1370)
 - Added language model input-modality and document capability resolution, automatically resolved from the models.dev catalog (falls back to text-only for uncatalogued/self-hosted models). [#1372](https://github.com/sourcebot-dev/sourcebot/pull/1372)
+- [EE] Added text file attachments to Ask Sourcebot, letting users attach text/code/config files to a chat message via the paperclip button, drag-and-drop, or paste, with large pastes auto-converted to attachments. [#1374](https://github.com/sourcebot-dev/sourcebot/pull/1374)
 
 ### Fixed
 - Send anonymous server-side PostHog events as personless so unauthenticated requests don't inflate person counts. [#1367](https://github.com/sourcebot-dev/sourcebot/pull/1367)
diff --git a/packages/web/package.json b/packages/web/package.json
index d6c1c4db6..61f1dade0 100644
--- a/packages/web/package.json
+++ b/packages/web/package.json
@@ -177,6 +177,7 @@
     "react-day-picker": "^9.14.0",
     "react-device-detect": "^2.2.3",
     "react-dom": "19.2.4",
+    "react-dropzone": "^15.0.0",
     "react-hook-form": "^7.53.0",
     "react-hotkeys-hook": "^4.5.1",
     "react-icons": "^5.6.0",
@@ -200,6 +201,7 @@
     "tailwindcss-animate": "^1.0.7",
     "use-stick-to-bottom": "^1.1.3",
     "usehooks-ts": "^3.1.0",
+    "uuid": "^14.0.0",
     "vscode-icons-js": "^11.6.1",
     "zod": "^3.25.76",
     "zod-to-json-schema": "^3.24.5"
diff --git a/packages/web/src/app/(app)/askgh/[owner]/[repo]/components/landingPage.tsx b/packages/web/src/app/(app)/askgh/[owner]/[repo]/components/landingPage.tsx
index f18ea5c74..afc7af4c3 100644
--- a/packages/web/src/app/(app)/askgh/[owner]/[repo]/components/landingPage.tsx
+++ b/packages/web/src/app/(app)/askgh/[owner]/[repo]/components/landingPage.tsx
@@ -3,14 +3,15 @@
 import Image from 'next/image';
 import { SearchModeSelector } from "@/app/(app)/components/searchModeSelector";
 import { Separator } from "@/components/ui/separator";
-import { ChatBox } from "@/features/chat/components/chatBox";
+import { ChatBox, ChatBoxHandle } from "@/features/chat/components/chatBox";
 import { ChatBoxToolbar } from "@/features/chat/components/chatBox/chatBoxToolbar";
+import { ChatPaneDropzone } from "@/features/chat/components/chatBox/chatPaneDropzone";
 import { NotConfiguredErrorBanner } from "@/features/chat/components/notConfiguredErrorBanner";
 import { LanguageModelInfo, RepoSearchScope } from "@/features/chat/types";
 import { useCreateNewChatThread } from "@/features/chat/useCreateNewChatThread";
 import { DISABLED_MCP_SERVER_IDS_LOCAL_STORAGE_KEY } from "@/features/chat/constants";
 import { getRepoImageSrc } from '@/lib/utils';
-import { useMemo, useState } from "react";
+import { useMemo, useRef, useState } from "react";
 import { useLocalStorage } from "usehooks-ts";
 
 interface LandingPageProps {
@@ -33,6 +34,7 @@ export const LandingPage = ({
     const { createNewChatThread, isLoading } = useCreateNewChatThread();
     const [isContextSelectorOpen, setIsContextSelectorOpen] = useState(false);
     const [disabledMcpServerIds, setDisabledMcpServerIds] = useLocalStorage<string[]>(DISABLED_MCP_SERVER_IDS_LOCAL_STORAGE_KEY, [], { initializeWithValue: false });
+    const chatBoxRef = useRef<ChatBoxHandle>(null);
     const isChatBoxDisabled = languageModels.length === 0;
 
     const selectedSearchScopes = useMemo(() => [
@@ -67,11 +69,16 @@ export const LandingPage = ({
                 </div>
 
                 {/* ChatBox */}
-                <div className="w-full">
+                <ChatPaneDropzone
+                    className="w-full"
+                    onFilesDropped={(files) => chatBoxRef.current?.addFiles(files)}
+                    disabled={isChatBoxDisabled}
+                >
                     <div className="border rounded-md w-full shadow-sm">
                         <ChatBox
-                            onSubmit={(children) => {
-                                createNewChatThread(children, selectedSearchScopes, disabledMcpServerIds);
+                            ref={chatBoxRef}
+                            onSubmit={(children, _editor, attachments) => {
+                                createNewChatThread(children, selectedSearchScopes, disabledMcpServerIds, attachments);
                             }}
                             className="min-h-[50px]"
                             isRedirecting={isLoading}
@@ -107,7 +114,7 @@ export const LandingPage = ({
                     {isChatBoxDisabled && (
                         <NotConfiguredErrorBanner className="mt-4" />
                     )}
-                </div>
+                </ChatPaneDropzone>
             </div>
         </div>
     )
diff --git a/packages/web/src/app/(app)/chat/chatLandingPage.tsx b/packages/web/src/app/(app)/chat/chatLandingPage.tsx
index 5bd84a3d0..f81e27247 100644
--- a/packages/web/src/app/(app)/chat/chatLandingPage.tsx
+++ b/packages/web/src/app/(app)/chat/chatLandingPage.tsx
@@ -5,6 +5,7 @@ import { CustomSlateEditor } from "@/features/chat/customSlateEditor";
 import { ServiceErrorException } from "@/lib/serviceError";
 import { isServiceError, measure } from "@/lib/utils";
 import { LandingPageChatBox } from "./components/landingPageChatBox";
+import { ChatLandingDropzone } from "./components/chatLandingDropzone";
 import { RepositoryCarousel } from "../components/repositoryCarousel";
 import { Separator } from "@/components/ui/separator";
 import { DemoCards } from "./components/demoCards";
@@ -56,7 +57,7 @@ export async function ChatLandingPage() {
     })() : undefined;
 
     return (
-        <div className="flex flex-col items-center h-full overflow-hidden">
+        <ChatLandingDropzone disabled={languageModels.length === 0}>
                 <div className="flex flex-col items-center h-full overflow-y-auto pt-8 pb-8 md:pt-16 w-full px-5">
                     <div className="max-h-44 w-auto">
                         <SourcebotLogo
@@ -92,6 +93,6 @@ export async function ChatLandingPage() {
                         </>
                     )}
                 </div>
-        </div>
+        </ChatLandingDropzone>
     )
 }
diff --git a/packages/web/src/app/(app)/chat/components/chatLandingDropzone.tsx b/packages/web/src/app/(app)/chat/components/chatLandingDropzone.tsx
new file mode 100644
index 000000000..821b3a5ba
--- /dev/null
+++ b/packages/web/src/app/(app)/chat/components/chatLandingDropzone.tsx
@@ -0,0 +1,44 @@
+'use client';
+
+import { ChatBoxHandle } from "@/features/chat/components/chatBox";
+import { ChatPaneDropzone } from "@/features/chat/components/chatBox/chatPaneDropzone";
+import { createContext, ReactNode, useCallback, useContext, useRef } from "react";
+
+type RegisterChatBoxHandle = (handle: ChatBoxHandle | null) => void;
+
+const LandingChatBoxContext = createContext<RegisterChatBoxHandle | null>(null);
+
+// Lets the (nested) landing chat box register its imperative handle so the
+// pane-level drop zone can forward dropped files into it. Returns a no-op when
+// rendered outside the provider.
+export const useRegisterLandingChatBox = (): RegisterChatBoxHandle => {
+    return useContext(LandingChatBoxContext) ?? (() => { });
+}
+
+interface ChatLandingDropzoneProps {
+    disabled?: boolean;
+    children: ReactNode;
+}
+
+// Wraps the entire unstarted-chat landing pane in a drag-and-drop target.
+// The chat box lives deeper in the tree (and behind a server/client boundary),
+// so it registers its handle via context rather than a direct ref.
+export const ChatLandingDropzone = ({ disabled, children }: ChatLandingDropzoneProps) => {
+    const handleRef = useRef<ChatBoxHandle | null>(null);
+
+    const register = useCallback<RegisterChatBoxHandle>((handle) => {
+        handleRef.current = handle;
+    }, []);
+
+    return (
+        <LandingChatBoxContext.Provider value={register}>
+            <ChatPaneDropzone
+                className="flex flex-col items-center h-full overflow-hidden"
+                onFilesDropped={(files) => handleRef.current?.addFiles(files)}
+                disabled={disabled}
+            >
+                {children}
+            </ChatPaneDropzone>
+        </LandingChatBoxContext.Provider>
+    )
+}
diff --git a/packages/web/src/app/(app)/chat/components/landingPageChatBox.tsx b/packages/web/src/app/(app)/chat/components/landingPageChatBox.tsx
index ed749450f..61f78bf4d 100644
--- a/packages/web/src/app/(app)/chat/components/landingPageChatBox.tsx
+++ b/packages/web/src/app/(app)/chat/components/landingPageChatBox.tsx
@@ -7,6 +7,7 @@ import { LanguageModelInfo, SearchScope } from "@/features/chat/types";
 import { useCreateNewChatThread } from "@/features/chat/useCreateNewChatThread";
 import { RepositoryQuery, SearchContextQuery } from "@/lib/types";
 import { useState } from "react";
+import { useRegisterLandingChatBox } from "./chatLandingDropzone";
 import { useLocalStorage } from "usehooks-ts";
 import { DISABLED_MCP_SERVER_IDS_LOCAL_STORAGE_KEY, SELECTED_SEARCH_SCOPES_LOCAL_STORAGE_KEY } from "@/features/chat/constants";
 import { SearchModeSelector } from "../../components/searchModeSelector";
@@ -31,14 +32,16 @@ export const LandingPageChatBox = ({
     const [selectedSearchScopes, setSelectedSearchScopes] = useLocalStorage<SearchScope[]>(SELECTED_SEARCH_SCOPES_LOCAL_STORAGE_KEY, [], { initializeWithValue: false });
     const [disabledMcpServerIds, setDisabledMcpServerIds] = useLocalStorage<string[]>(DISABLED_MCP_SERVER_IDS_LOCAL_STORAGE_KEY, [], { initializeWithValue: false });
     const [isContextSelectorOpen, setIsContextSelectorOpen] = useState(false);
+    const registerChatBox = useRegisterLandingChatBox();
     const isChatBoxDisabled = languageModels.length === 0;
 
     return (
         <div className="w-full max-w-[800px] mt-4">
             <div className="border rounded-md w-full shadow-sm">
                 <ChatBox
-                    onSubmit={(children) => {
-                        createNewChatThread(children, selectedSearchScopes, disabledMcpServerIds);
+                    ref={registerChatBox}
+                    onSubmit={(children, _editor, attachments) => {
+                        createNewChatThread(children, selectedSearchScopes, disabledMcpServerIds, attachments);
                     }}
                     className="min-h-[50px]"
                     isRedirecting={isLoading}
@@ -74,6 +77,6 @@ export const LandingPageChatBox = ({
             {isChatBoxDisabled && (
                 <NotConfiguredErrorBanner className="mt-4" />
             )}
-        </div >
+        </div>
     )
 }
diff --git a/packages/web/src/ee/features/chat/agent.ts b/packages/web/src/ee/features/chat/agent.ts
index c0f1e45bc..e6cc49ca3 100644
--- a/packages/web/src/ee/features/chat/agent.ts
+++ b/packages/web/src/ee/features/chat/agent.ts
@@ -22,7 +22,7 @@ import { randomUUID } from "crypto";
 import _dedent from "dedent";
 import { ANSWER_TAG, FILE_REFERENCE_PREFIX } from "@/features/chat/constants";
 import { Source } from "@/features/chat/types";
-import { addLineNumbers, fileReferenceToString, getAnswerPartFromAssistantMessage, getTurnProgressState, getUserMessageText } from "@/features/chat/utils";
+import { addLineNumbers, fileReferenceToString, formatAttachmentsForPrompt, getAnswerPartFromAssistantMessage, getTurnProgressState, getUserMessageAttachments, getUserMessageText } from "@/features/chat/utils";
 import { createTools } from "./tools";
 import { getConnectedMcpClients } from "@/ee/features/chat/mcp/mcpClientFactory";
 import { getMcpTools, McpToolsResult } from "@/ee/features/chat/mcp/mcpToolSets";
@@ -105,9 +105,16 @@ export const createMessageStream = async ({
     let messageHistory: ModelMessage[] =
         messages.map((message, index): ModelMessage | undefined => {
             if (message.role === 'user') {
+                // Fold inline-text attachments into this turn's content (not the
+                // system prompt) so they stay bound to their turn, re-emitted from
+                // the persisted parts.
+                const text = getUserMessageText(message);
+                const attachmentsBlock = formatAttachmentsForPrompt(
+                    getUserMessageAttachments(message),
+                );
                 return {
                     role: 'user',
-                    content: getUserMessageText(message),
+                    content: attachmentsBlock ? `${text}\n\n${attachmentsBlock}` : text,
                 };
             }
 
diff --git a/packages/web/src/ee/features/chat/components/chatThread/chatThread.tsx b/packages/web/src/ee/features/chat/components/chatThread/chatThread.tsx
index 87faf79f8..a7dfa82af 100644
--- a/packages/web/src/ee/features/chat/components/chatThread/chatThread.tsx
+++ b/packages/web/src/ee/features/chat/components/chatThread/chatThread.tsx
@@ -4,7 +4,7 @@ import { useToast } from '@/components/hooks/use-toast';
 import { Button } from '@/components/ui/button';
 import { Separator } from '@/components/ui/separator';
 import { CustomSlateEditor } from '@/features/chat/customSlateEditor';
-import { AdditionalChatRequestParams, CustomEditor, LanguageModelInfo, SBChatMessage, SearchScope, Source } from '@/features/chat/types';
+import { AdditionalChatRequestParams, AttachmentData, CustomEditor, LanguageModelInfo, SBChatMessage, SearchScope, Source } from '@/features/chat/types';
 import { createUIMessage, getAllMentionElements, getTurnProgressState, getUserMessageText, resetEditor, slateContentToString } from '@/features/chat/utils';
 import { useChat } from '@ai-sdk/react';
 import { CreateUIMessage, DefaultChatTransport, lastAssistantMessageIsCompleteWithApprovalResponses } from 'ai';
@@ -15,8 +15,9 @@ import { useStickToBottom } from 'use-stick-to-bottom';
 import { Descendant } from 'slate';
 import { useMessagePairs } from '../../useMessagePairs';
 import { useSelectedLanguageModel } from '@/features/chat/useSelectedLanguageModel';
-import { ChatBox } from '@/features/chat/components/chatBox';
+import { ChatBox, ChatBoxHandle } from '@/features/chat/components/chatBox';
 import { ChatBoxToolbar } from '@/features/chat/components/chatBox/chatBoxToolbar';
+import { ChatPaneDropzone } from '@/features/chat/components/chatBox/chatPaneDropzone';
 import { ChatThreadListItem } from './chatThreadListItem';
 import { ErrorBanner } from './errorBanner';
 import { McpFailedServersBanner } from './mcpFailedServersBanner';
@@ -72,6 +73,7 @@ export const ChatThread = ({
 }: ChatThreadProps) => {
     const [isErrorBannerVisible, setIsErrorBannerVisible] = useState(false);
     const hasSubmittedInputMessage = useRef(false);
+    const chatBoxRef = useRef<ChatBoxHandle>(null);
     const { scrollRef, contentRef, scrollToBottom, isAtBottom } = useStickToBottom({ initial: false });
     const { toast } = useToast();
     const router = useRouter();
@@ -347,11 +349,11 @@ export const ChatThread = ({
         }
     }, [error]);
 
-    const onSubmit = useCallback(async (children: Descendant[], editor: CustomEditor) => {
+    const onSubmit = useCallback(async (children: Descendant[], editor: CustomEditor, attachments: AttachmentData[]) => {
         const text = slateContentToString(children);
         const mentions = getAllMentionElements(children);
 
-        const message = createUIMessage(text, mentions.map(({ data }) => data), selectedSearchScopes, disabledMcpServerIds);
+        const message = createUIMessage(text, mentions.map(({ data }) => data), selectedSearchScopes, disabledMcpServerIds, attachments);
         sendMessage(message);
 
         scrollToBottom();
@@ -381,6 +383,11 @@ export const ChatThread = ({
     return (
         <ToolApprovalProvider value={addToolApprovalResponse}>
         <McpServerIconContext.Provider value={mcpServerIconMap}>
+        <ChatPaneDropzone
+            className="flex flex-col flex-1 min-h-0 w-full"
+            onFilesDropped={(files) => chatBoxRef.current?.addFiles(files)}
+            disabled={!isOwner || languageModels.length === 0}
+        >
             {error && (
                 <ErrorBanner
                     error={error}
@@ -470,6 +477,7 @@ export const ChatThread = ({
                         <div className="border rounded-md w-full shadow-sm">
                             <CustomSlateEditor>
                                 <ChatBox
+                                    ref={chatBoxRef}
                                     onSubmit={onSubmit}
                                     className="min-h-[80px]"
                                     preferredSuggestionsBoxPlacement="top-start"
@@ -520,6 +528,7 @@ export const ChatThread = ({
                     </div>
                 )}
             </div>
+        </ChatPaneDropzone>
         </McpServerIconContext.Provider>
         </ToolApprovalProvider>
     );
diff --git a/packages/web/src/ee/features/chat/components/chatThread/chatThreadListItem.tsx b/packages/web/src/ee/features/chat/components/chatThread/chatThreadListItem.tsx
index 31191ecc4..8d6e42827 100644
--- a/packages/web/src/ee/features/chat/components/chatThread/chatThreadListItem.tsx
+++ b/packages/web/src/ee/features/chat/components/chatThread/chatThreadListItem.tsx
@@ -8,8 +8,9 @@ import { CSSProperties, forwardRef, memo, useCallback, useEffect, useMemo, useRe
 import scrollIntoView from 'scroll-into-view-if-needed';
 import { Reference, referenceSchema, SBChatMessage, Source } from "@/features/chat/types";
 import { useExtractReferences } from '../../useExtractReferences';
-import { getAnswerPartFromAssistantMessage, getLastStepParts, getUserMessageText, groupMessageIntoSteps, isSBChatToolPart, repairReferences } from '@/features/chat/utils';
+import { getAnswerPartFromAssistantMessage, getLastStepParts, getUserMessageAttachments, getUserMessageText, groupMessageIntoSteps, isSBChatToolPart, repairReferences } from '@/features/chat/utils';
 import { AnswerCard } from './answerCard';
+import { MessageAttachments } from './messageAttachments';
 import { DetailsCard } from './detailsCard';
 import { ApprovalRequestedToolPart, ToolApprovalBanner } from './toolApprovalBanner';
 import { MarkdownRenderer, REFERENCE_PAYLOAD_ATTRIBUTE } from './markdownRenderer';
@@ -68,6 +69,10 @@ const ChatThreadListItemComponent = forwardRef<HTMLDivElement, ChatThreadListIte
         return getUserMessageText(userMessage);
     }, [userMessage]);
 
+    const userAttachments = useMemo(() => {
+        return getUserMessageAttachments(userMessage);
+    }, [userMessage]);
+
     // Take the assistant message and repair any references that are not properly formatted.
     // This applies to parts that are text (i.e., text & reasoning).
     const assistantMessage = useMemo(() => {
@@ -418,27 +423,30 @@ const ChatThreadListItemComponent = forwardRef<HTMLDivElement, ChatThreadListIte
                         ref={leftPanelRef}
                         className="py-4 h-full"
                     >
-                        <div className="flex flex-row gap-2 mb-4">
-                            {isTurnInProgress ? (
-                                <Loader2 className="w-4 h-4 animate-spin flex-shrink-0 mt-1.5" />
-                            ) : (
-                                <CheckCircle className="w-4 h-4 text-green-700 flex-shrink-0 mt-1.5" />
+                        <div className="mb-4">
+                            {userAttachments.length > 0 && (
+                                <MessageAttachments attachments={userAttachments} className="mb-1.5 ml-6" />
                             )}
-                            <MarkdownRenderer
-                                content={userQuestion.trim()}
-                                className="prose-p:m-0"
-                                escapeHtml={true}
-                            />
+
+                            <div className="flex flex-row gap-2">
+                                {isTurnInProgress ? (
+                                    <Loader2 className="w-4 h-4 animate-spin flex-shrink-0 mt-1.5" />
+                                ) : (
+                                    <CheckCircle className="w-4 h-4 text-green-700 flex-shrink-0 mt-1.5" />
+                                )}
+                                <MarkdownRenderer
+                                    content={userQuestion.trim()}
+                                    className="prose-p:m-0"
+                                    escapeHtml={true}
+                                />
+                            </div>
                         </div>
 
                         {isThinking && (
-                            <div className="space-y-4 mb-4">
-                                <Skeleton className="h-4 max-w-32" />
-                                <div className="space-y-2">
-                                    <Skeleton className="h-3 max-w-72" />
-                                    <Skeleton className="h-3 max-w-64" />
-                                    <Skeleton className="h-3 max-w-56" />
-                                </div>
+                            <div className="space-y-2 mb-4">
+                                <Skeleton className="h-3 w-full max-w-80" />
+                                <Skeleton className="h-3 w-full max-w-72" />
+                                <Skeleton className="h-3 w-full max-w-56" />
                             </div>
                         )}
 
diff --git a/packages/web/src/ee/features/chat/components/chatThread/detailsCard.tsx b/packages/web/src/ee/features/chat/components/chatThread/detailsCard.tsx
index 7b6c7867f..c705b6be5 100644
--- a/packages/web/src/ee/features/chat/components/chatThread/detailsCard.tsx
+++ b/packages/web/src/ee/features/chat/components/chatThread/detailsCard.tsx
@@ -537,6 +537,7 @@ export const StepPartRenderer = ({ part, toolTokenUsageMap }: { part: SBChatMess
         case 'data-source':
         case 'data-mcp-server':
         case 'data-mcp-failed-server':
+        case 'data-attachment':
         case 'file':
         case 'source-document':
         case 'source-url':
diff --git a/packages/web/src/ee/features/chat/components/chatThread/messageAttachments.tsx b/packages/web/src/ee/features/chat/components/chatThread/messageAttachments.tsx
new file mode 100644
index 000000000..7d2b5040e
--- /dev/null
+++ b/packages/web/src/ee/features/chat/components/chatThread/messageAttachments.tsx
@@ -0,0 +1,47 @@
+'use client';
+
+import { VscodeFileIcon } from "@/app/components/vscodeFileIcon";
+import { AttachmentViewerDialog } from "@/features/chat/components/chatBox/attachmentViewerDialog";
+import { AttachmentData } from "@/features/chat/types";
+import { cn } from "@/lib/utils";
+import { useState } from "react";
+
+interface MessageAttachmentsProps {
+    attachments: AttachmentData[];
+    className?: string;
+}
+
+export const MessageAttachments = ({ attachments, className }: MessageAttachmentsProps) => {
+    const [activeAttachment, setActiveAttachment] = useState<AttachmentData | null>(null);
+
+    if (attachments.length === 0) {
+        return null;
+    }
+
+    return (
+        <>
+            <div className={cn("flex flex-row flex-wrap gap-1.5", className)}>
+                {attachments.map((attachment, index) => (
+                    <button
+                        key={`${attachment.filename}-${index}`}
+                        type="button"
+                        onClick={() => setActiveAttachment(attachment)}
+                        className="flex flex-row items-center gap-1 rounded bg-muted px-1.5 py-0.5 text-xs hover:bg-accent transition-colors"
+                        title={`View ${attachment.filename}`}
+                    >
+                        <VscodeFileIcon fileName={attachment.filename} className="w-3 h-3" />
+                        <span className="font-mono max-w-[160px] truncate">
+                            {attachment.filename}
+                        </span>
+                    </button>
+                ))}
+            </div>
+            <AttachmentViewerDialog
+                open={activeAttachment !== null}
+                onOpenChange={(open) => !open && setActiveAttachment(null)}
+                filename={activeAttachment?.filename}
+                text={activeAttachment?.kind === 'text' ? activeAttachment.text : undefined}
+            />
+        </>
+    )
+}
diff --git a/packages/web/src/features/chat/attachmentUtils.ts b/packages/web/src/features/chat/attachmentUtils.ts
new file mode 100644
index 000000000..4ab042532
--- /dev/null
+++ b/packages/web/src/features/chat/attachmentUtils.ts
@@ -0,0 +1,198 @@
+'use client';
+
+import {
+    ATTACHMENT_ALLOWED_TEXT_EXTENSIONS,
+    ATTACHMENT_ALLOWED_TEXT_MIME_TYPES,
+    ATTACHMENT_MAX_TURN_TEXT_BYTES,
+    ATTACHMENT_PASTE_AUTO_CONVERT_MIN_CHARS,
+    ATTACHMENT_PASTE_AUTO_CONVERT_MIN_LINES,
+} from "./constants";
+import { AttachmentData, TextAttachment } from "./types";
+import { v4 as uuidv4 } from "uuid";
+
+// Normalizes an untrusted filename: basename only, strips control chars (which
+// could break the `<attachment filename="...">` tag or UI), collapses whitespace.
+export const sanitizeFilename = (name: string): string => {
+    const basename = name.split(/[\\/]/).pop() ?? name;
+    return Array.from(basename)
+        .filter((char) => {
+            const code = char.charCodeAt(0);
+            return code >= 32 && code !== 127;
+        })
+        .join('')
+        .replace(/\s+/g, ' ')
+        .trim() || 'attachment';
+}
+
+// A text attachment selected in the chat box but not yet submitted. The `id`
+// is a client-only key for list rendering and removal; it is stripped before
+// the attachment becomes part of a message.
+export type PendingAttachment = TextAttachment & { id: string };
+
+// Builds the comma-separated `accept` attribute for a native `<input type=file>`
+// so the OS picker only surfaces supported text file types.
+export const getAttachmentAcceptAttribute = (): string => {
+    return [
+        'text/*',
+        ...ATTACHMENT_ALLOWED_TEXT_MIME_TYPES,
+        ...ATTACHMENT_ALLOWED_TEXT_EXTENSIONS.map((extension) => `.${extension}`),
+    ].join(',');
+}
+
+// Builds react-dropzone's `accept` map. Extensions are attached to `text/plain`
+// so code files that report an empty/unusual MIME type are still selectable.
+export const getAttachmentDropzoneAccept = (): Record<string, string[]> => {
+    const accept: Record<string, string[]> = {
+        'text/*': [],
+        'text/plain': ATTACHMENT_ALLOWED_TEXT_EXTENSIONS.map((extension) => `.${extension}`),
+    };
+    for (const mimeType of ATTACHMENT_ALLOWED_TEXT_MIME_TYPES) {
+        accept[mimeType] = [];
+    }
+    return accept;
+}
+
+// Total UTF-8 byte size of a turn's submitted text (prompt + attachment bodies),
+// checked against ATTACHMENT_MAX_TURN_TEXT_BYTES at submit time.
+export const getSubmittedTextBytes = (text: string, attachments: PendingAttachment[]): number => {
+    const textBytes = new TextEncoder().encode(text).length;
+    const attachmentBytes = attachments.reduce((sum, attachment) => sum + attachment.sizeBytes, 0);
+    return textBytes + attachmentBytes;
+}
+
+export const toAttachmentData = (attachment: PendingAttachment): AttachmentData => {
+    return {
+        kind: attachment.kind,
+        filename: attachment.filename,
+        mediaType: attachment.mediaType,
+        sizeBytes: attachment.sizeBytes,
+        text: attachment.text,
+    };
+}
+
+const getExtension = (filename: string): string => {
+    const parts = filename.toLowerCase().split('.');
+    return parts.length > 1 ? (parts[parts.length - 1] ?? '') : '';
+}
+
+export const isAllowedTextFile = (file: File): boolean => {
+    if (file.type.startsWith('text/')) {
+        return true;
+    }
+    if (ATTACHMENT_ALLOWED_TEXT_MIME_TYPES.includes(file.type)) {
+        return true;
+    }
+
+    const extension = getExtension(file.name);
+    if (ATTACHMENT_ALLOWED_TEXT_EXTENSIONS.includes(extension)) {
+        return true;
+    }
+
+    // Files with no extension (e.g. "Dockerfile") report an empty extension;
+    // fall back to matching the whole lowercased filename.
+    const nameLower = file.name.toLowerCase();
+    if (ATTACHMENT_ALLOWED_TEXT_EXTENSIONS.includes(nameLower)) {
+        return true;
+    }
+
+    return false;
+}
+
+const readAsText = (file: File): Promise<string> => {
+    return new Promise((resolve, reject) => {
+        const reader = new FileReader();
+        reader.onerror = () => reject(reader.error ?? new Error('Failed to read file'));
+        reader.onload = () => resolve(typeof reader.result === 'string' ? reader.result : '');
+        reader.readAsText(file);
+    });
+}
+
+// Whether a plain-text paste is large enough to auto-convert into an attachment
+// instead of being inserted inline. Gated on length or line count.
+export const shouldAutoConvertPaste = (text: string): boolean => {
+    if (text.length >= ATTACHMENT_PASTE_AUTO_CONVERT_MIN_CHARS) {
+        return true;
+    }
+    return countLines(text) >= ATTACHMENT_PASTE_AUTO_CONVERT_MIN_LINES;
+}
+
+export const countLines = (text: string): number => {
+    if (text.length === 0) {
+        return 0;
+    }
+    return text.split('\n').length;
+}
+
+// Generates a non-colliding filename for an auto-converted paste, e.g.
+// `pasted.txt`, then `pasted-2.txt`, `pasted-3.txt`, ...
+const getPastedAttachmentFilename = (existing: PendingAttachment[]): string => {
+    const used = new Set(existing.map((attachment) => attachment.filename));
+    if (!used.has('pasted.txt')) {
+        return 'pasted.txt';
+    }
+
+    let index = 2;
+    while (used.has(`pasted-${index}.txt`)) {
+        index++;
+    }
+    return `pasted-${index}.txt`;
+}
+
+// Builds a pending text attachment from a pasted string. The per-turn text
+// budget is enforced once at submit time, not here, so this can't fail.
+export const createPastedTextAttachment = (
+    text: string,
+    existing: PendingAttachment[],
+): PendingAttachment => {
+    return {
+        id: uuidv4(),
+        kind: 'text',
+        filename: getPastedAttachmentFilename(existing),
+        mediaType: 'text/plain',
+        sizeBytes: new Blob([text]).size,
+        text,
+    };
+}
+
+export type ReadFilesResult = {
+    attachments: PendingAttachment[];
+    errors: string[];
+};
+
+// Reads files into pending text attachments, rejecting non-text files and any
+// file larger than the per-turn budget (skipped before reading to avoid loading
+// a huge file into memory). The aggregate budget is enforced at submit time.
+export const readFilesAsAttachments = async (
+    files: File[],
+): Promise<ReadFilesResult> => {
+    const attachments: PendingAttachment[] = [];
+    const errors: string[] = [];
+
+    for (const file of files) {
+        if (!isAllowedTextFile(file)) {
+            errors.push(`${file.name}: unsupported file type (text files only).`);
+            continue;
+        }
+
+        if (file.size > ATTACHMENT_MAX_TURN_TEXT_BYTES) {
+            errors.push(`${file.name}: exceeds the ${Math.round(ATTACHMENT_MAX_TURN_TEXT_BYTES / 1024)}KB per-message limit.`);
+            continue;
+        }
+
+        try {
+            const text = await readAsText(file);
+            attachments.push({
+                id: uuidv4(),
+                kind: 'text',
+                filename: sanitizeFilename(file.name),
+                mediaType: file.type || 'text/plain',
+                sizeBytes: file.size,
+                text,
+            });
+        } catch {
+            errors.push(`${file.name}: failed to read file.`);
+        }
+    }
+
+    return { attachments, errors };
+}
diff --git a/packages/web/src/features/chat/components/chatBox/attachmentButton.tsx b/packages/web/src/features/chat/components/chatBox/attachmentButton.tsx
new file mode 100644
index 000000000..fef235c06
--- /dev/null
+++ b/packages/web/src/features/chat/components/chatBox/attachmentButton.tsx
@@ -0,0 +1,54 @@
+'use client';
+
+import { Button } from "@/components/ui/button";
+import { Tooltip, TooltipContent, TooltipTrigger } from "@/components/ui/tooltip";
+import { getAttachmentAcceptAttribute } from "@/features/chat/attachmentUtils";
+import { Paperclip } from "lucide-react";
+import { useRef } from "react";
+
+interface AttachmentButtonProps {
+    onAddFiles: (files: File[]) => void;
+    disabled?: boolean;
+}
+
+export const AttachmentButton = ({ onAddFiles, disabled }: AttachmentButtonProps) => {
+    const inputRef = useRef<HTMLInputElement>(null);
+
+    return (
+        <>
+            <input
+                ref={inputRef}
+                type="file"
+                multiple
+                accept={getAttachmentAcceptAttribute()}
+                className="hidden"
+                onChange={(e) => {
+                    const files = e.target.files ? Array.from(e.target.files) : [];
+                    if (files.length > 0) {
+                        onAddFiles(files);
+                    }
+                    // Reset so selecting the same file again re-triggers onChange.
+                    e.target.value = '';
+                }}
+            />
+            <Tooltip>
+                <TooltipTrigger asChild>
+                    <Button
+                        type="button"
+                        variant="ghost"
+                        size="icon"
+                        className="w-6 h-6 text-muted-foreground hover:text-foreground"
+                        disabled={disabled}
+                        onClick={() => inputRef.current?.click()}
+                        aria-label="Attach files"
+                    >
+                        <Paperclip className="w-4 h-4" />
+                    </Button>
+                </TooltipTrigger>
+                <TooltipContent>
+                    Attach text files
+                </TooltipContent>
+            </Tooltip>
+        </>
+    )
+}
diff --git a/packages/web/src/features/chat/components/chatBox/attachmentTray.tsx b/packages/web/src/features/chat/components/chatBox/attachmentTray.tsx
new file mode 100644
index 000000000..2646fa93b
--- /dev/null
+++ b/packages/web/src/features/chat/components/chatBox/attachmentTray.tsx
@@ -0,0 +1,65 @@
+'use client';
+
+import { VscodeFileIcon } from "@/app/components/vscodeFileIcon";
+import { cn } from "@/lib/utils";
+import { X } from "lucide-react";
+import { useState } from "react";
+import { PendingAttachment } from "../../attachmentUtils";
+import { AttachmentViewerDialog } from "./attachmentViewerDialog";
+
+interface AttachmentTrayProps {
+    attachments: PendingAttachment[];
+    // Omitted when the tray is read-only (e.g. while a submission is
+    // redirecting); the remove control is hidden in that case.
+    onRemove?: (id: string) => void;
+    className?: string;
+}
+
+export const AttachmentTray = ({ attachments, onRemove, className }: AttachmentTrayProps) => {
+    const [activeAttachment, setActiveAttachment] = useState<PendingAttachment | null>(null);
+
+    if (attachments.length === 0) {
+        return null;
+    }
+
+    return (
+        <>
+            <div className={cn("flex flex-row flex-wrap gap-1.5", className)}>
+                {attachments.map((attachment) => (
+                    <div
+                        key={attachment.id}
+                        className="flex flex-row items-center gap-1 rounded bg-muted px-1.5 py-0.5 text-xs"
+                    >
+                        <button
+                            type="button"
+                            onClick={() => setActiveAttachment(attachment)}
+                            className="flex flex-row items-center gap-1 hover:text-foreground"
+                            title={`View ${attachment.filename}`}
+                        >
+                            <VscodeFileIcon fileName={attachment.filename} className="w-3 h-3" />
+                            <span className="font-mono max-w-[160px] truncate">
+                                {attachment.filename}
+                            </span>
+                        </button>
+                        {onRemove && (
+                            <button
+                                type="button"
+                                onClick={() => onRemove(attachment.id)}
+                                className="text-muted-foreground hover:text-foreground"
+                                aria-label={`Remove ${attachment.filename}`}
+                            >
+                                <X className="w-3 h-3" />
+                            </button>
+                        )}
+                    </div>
+                ))}
+            </div>
+            <AttachmentViewerDialog
+                open={activeAttachment !== null}
+                onOpenChange={(open) => !open && setActiveAttachment(null)}
+                filename={activeAttachment?.filename}
+                text={activeAttachment?.text}
+            />
+        </>
+    )
+}
diff --git a/packages/web/src/features/chat/components/chatBox/attachmentViewerDialog.tsx b/packages/web/src/features/chat/components/chatBox/attachmentViewerDialog.tsx
new file mode 100644
index 000000000..46dc236dc
--- /dev/null
+++ b/packages/web/src/features/chat/components/chatBox/attachmentViewerDialog.tsx
@@ -0,0 +1,54 @@
+'use client';
+
+import { Dialog, DialogContent, DialogDescription, DialogHeader, DialogTitle } from "@/components/ui/dialog";
+import { useEffect } from "react";
+
+interface AttachmentViewerDialogProps {
+    filename?: string;
+    text?: string;
+    open: boolean;
+    onOpenChange: (open: boolean) => void;
+}
+
+// Shared viewer for inspecting an inline-text attachment's contents. Used for
+// both staged (not-yet-sent) and sent attachments.
+export const AttachmentViewerDialog = ({ filename, text, open, onOpenChange }: AttachmentViewerDialogProps) => {
+    // The staged viewer is rendered inside the Slate `Editable` subtree, where
+    // Radix's built-in Escape-to-close can get swallowed by the editor's
+    // focus/key handling. A capture-phase listener guarantees Escape closes the
+    // dialog, matching every other modal in the app.
+    useEffect(() => {
+        if (!open) {
+            return;
+        }
+
+        const handleKeyDown = (event: KeyboardEvent) => {
+            if (event.key === 'Escape') {
+                onOpenChange(false);
+            }
+        };
+
+        document.addEventListener('keydown', handleKeyDown, true);
+        return () => {
+            document.removeEventListener('keydown', handleKeyDown, true);
+        };
+    }, [open, onOpenChange]);
+
+    return (
+        <Dialog open={open} onOpenChange={onOpenChange}>
+            <DialogContent className="max-w-3xl">
+                <DialogHeader>
+                    <DialogTitle className="font-mono text-sm break-all">
+                        {filename}
+                    </DialogTitle>
+                    <DialogDescription className="sr-only">
+                        Preview of the attached file{filename ? ` ${filename}` : ''}.
+                    </DialogDescription>
+                </DialogHeader>
+                <pre className="max-h-[60vh] overflow-auto rounded bg-muted p-3 text-xs whitespace-pre-wrap break-words">
+                    {text}
+                </pre>
+            </DialogContent>
+        </Dialog>
+    )
+}
diff --git a/packages/web/src/features/chat/components/chatBox/chatBox.tsx b/packages/web/src/features/chat/components/chatBox/chatBox.tsx
index e405e8266..1bd33235f 100644
--- a/packages/web/src/features/chat/components/chatBox/chatBox.tsx
+++ b/packages/web/src/features/chat/components/chatBox/chatBox.tsx
@@ -3,13 +3,16 @@
 import { VscodeFileIcon } from "@/app/components/vscodeFileIcon";
 import { Button } from "@/components/ui/button";
 import { Tooltip, TooltipContent, TooltipTrigger } from "@/components/ui/tooltip";
-import { CustomEditor, MentionElement, RenderElementPropsFor, SearchScope } from "@/features/chat/types";
+import { AttachmentData, CustomEditor, MentionElement, RenderElementPropsFor, SearchScope } from "@/features/chat/types";
 import { insertMention, slateContentToString } from "@/features/chat/utils";
+import { createPastedTextAttachment, getSubmittedTextBytes, PendingAttachment, readFilesAsAttachments, shouldAutoConvertPaste, toAttachmentData } from "@/features/chat/attachmentUtils";
+import { AttachmentButton } from "./attachmentButton";
+import { AttachmentTray } from "./attachmentTray";
 import { cn } from "@/lib/utils";
 import { useIsMac } from "@/hooks/useIsMac";
 import { computePosition, flip, offset, shift, VirtualElement } from "@floating-ui/react";
 import { ArrowUp, Loader2, StopCircleIcon } from "lucide-react";
-import { Fragment, KeyboardEvent, memo, useCallback, useEffect, useMemo, useRef, useState } from "react";
+import { forwardRef, Fragment, KeyboardEvent, memo, Ref, useCallback, useEffect, useImperativeHandle, useMemo, useRef, useState } from "react";
 import { useHotkeys } from "react-hotkeys-hook";
 import { Descendant, insertText } from "slate";
 import { Editable, ReactEditor, RenderElementProps, RenderLeafProps, useFocused, useSelected, useSlate } from "slate-react";
@@ -23,13 +26,17 @@ import { SearchContextQuery } from "@/lib/types";
 import isEqual from "fast-deep-equal/react";
 import { LoginDialog } from "./loginDialog";
 import { usePathname } from "next/navigation";
-import { PENDING_CHAT_SUBMISSION_SESSION_STORAGE_KEY } from "@/features/chat/constants";
+import { ATTACHMENT_MAX_TURN_TEXT_BYTES, PENDING_CHAT_SUBMISSION_SESSION_STORAGE_KEY } from "@/features/chat/constants";
 import useCaptureEvent from "@/hooks/useCaptureEvent";
 import { useHasEntitlement } from "@/features/entitlements/useHasEntitlement";
 import { UpsellDialog } from "@/features/billing/upsellDialog";
 
+export interface ChatBoxHandle {
+    addFiles: (files: File[]) => void;
+}
+
 interface ChatBoxProps {
-    onSubmit: (children: Descendant[], editor: CustomEditor) => void;
+    onSubmit: (children: Descendant[], editor: CustomEditor, attachments: AttachmentData[]) => void;
     onStop?: () => void;
     preferredSuggestionsBoxPlacement?: "top-start" | "bottom-start";
     className?: string;
@@ -56,7 +63,7 @@ const ChatBoxComponent = ({
     isAuthenticated,
     selectedSearchScopes,
     searchContexts,
-}: ChatBoxProps) => {
+}: ChatBoxProps, ref: Ref<ChatBoxHandle>) => {
     const suggestionsBoxRef = useRef<HTMLDivElement>(null);
     const [index, setIndex] = useState(0);
     const editor = useSlate();
@@ -82,11 +89,86 @@ const ChatBoxComponent = ({
     });
     const { selectedLanguageModel } = useSelectedLanguageModel();
     const { toast } = useToast();
+    const isMac = useIsMac();
     const isAskEnabled = useHasEntitlement('ask');
     const [isLoginDialogOpen, setIsLoginDialogOpen] = useState<boolean>(false);
     const [isUpsellDialogOpen, setIsUpsellDialogOpen] = useState<boolean>(false);
+    const [attachments, setAttachments] = useState<PendingAttachment[]>([]);
+    const [submittedAttachments, setSubmittedAttachments] = useState<PendingAttachment[]>([]);
     const pathname = usePathname();
 
+    // Set when the user triggers a paste with the OS raw-paste chord
+    // (⌘⇧V / Ctrl+Shift+V). The subsequent `paste` event reads (and clears)
+    // this so the large-paste auto-conversion is skipped for that one paste.
+    const rawPasteRequestedRef = useRef<boolean>(false);
+
+    // Warning shown when prompt text + `nextAttachments` would exceed the per-turn
+    // budget, so an over-budget add surfaces immediately instead of just disabling submit.
+    const getOverBudgetWarning = useCallback((nextAttachments: PendingAttachment[]): string | null => {
+        const totalBytes = getSubmittedTextBytes(slateContentToString(editor.children), nextAttachments);
+        if (totalBytes <= ATTACHMENT_MAX_TURN_TEXT_BYTES) {
+            return null;
+        }
+        return `Attachments exceed the ${Math.round(ATTACHMENT_MAX_TURN_TEXT_BYTES / 1024)}KB per-message limit. Remove a file or shorten your message to send.`;
+    }, [editor]);
+
+    const onAddPastedText = useCallback((text: string) => {
+        const attachment = createPastedTextAttachment(text, attachments);
+        setAttachments((prev) => [...prev, attachment]);
+
+        const overBudgetWarning = getOverBudgetWarning([...attachments, attachment]);
+        if (overBudgetWarning) {
+            toast({
+                description: `⚠️ ${overBudgetWarning}`,
+                variant: "destructive",
+            });
+        } else {
+            toast({
+                title: "Large paste added as an attachment",
+                duration: 5 * 1000,
+                className: "w-fit ml-auto",
+                description: `Use ${isMac ? "⌘+⇧+V" : "Ctrl+Shift+V"} to paste inline instead`,
+            });
+        }
+
+        ReactEditor.focus(editor);
+    }, [attachments, editor, toast, isMac, getOverBudgetWarning]);
+
+    const onAddFiles = useCallback(async (files: File[]) => {
+        if (files.length === 0) {
+            return;
+        }
+
+        const { attachments: added, errors } = await readFilesAsAttachments(files);
+        if (added.length > 0) {
+            setAttachments((prev) => [...prev, ...added]);
+        }
+
+        const overBudgetWarning = added.length > 0 ? getOverBudgetWarning([...attachments, ...added]) : null;
+        const messages = [...errors, ...(overBudgetWarning ? [overBudgetWarning] : [])];
+        if (messages.length > 0) {
+            toast({
+                description: `⚠️ ${messages.join(' ')}`,
+                variant: "destructive",
+            });
+        }
+
+        // Return focus to the prompt input so the user can keep typing.
+        ReactEditor.focus(editor);
+    }, [attachments, toast, editor, getOverBudgetWarning]);
+
+    const removeAttachment = useCallback((id: string) => {
+        setAttachments((prev) => prev.filter((attachment) => attachment.id !== id));
+    }, []);
+
+    // Allow an ancestor pane-level drop zone to forward dropped files into this
+    // chat box (which owns attachment state). See `ChatPaneDropzone`.
+    useImperativeHandle(ref, () => ({
+        addFiles: (files: File[]) => {
+            void onAddFiles(files);
+        },
+    }), [onAddFiles]);
+
     // Reset the index when the suggestion mode changes.
     useEffect(() => {
         setIndex(0);
@@ -118,18 +200,27 @@ const ChatBoxComponent = ({
 
     const { isSubmitDisabled, isSubmitDisabledReason } = useMemo((): {
         isSubmitDisabled: true,
-        isSubmitDisabledReason: "empty" | "redirecting" | "generating" | "no-language-model-selected"
+        isSubmitDisabledReason: "empty" | "too-large" | "redirecting" | "generating" | "no-language-model-selected"
     } | {
         isSubmitDisabled: false,
         isSubmitDisabledReason: undefined,
     } => {
-        if (slateContentToString(editor.children).trim().length === 0) {
+        const text = slateContentToString(editor.children);
+        if (text.trim().length === 0 && attachments.length === 0) {
             return {
                 isSubmitDisabled: true,
                 isSubmitDisabledReason: "empty",
             }
         }
 
+        // Single per-turn bound on the submitted text (prompt + attachments).
+        if (getSubmittedTextBytes(text, attachments) > ATTACHMENT_MAX_TURN_TEXT_BYTES) {
+            return {
+                isSubmitDisabled: true,
+                isSubmitDisabledReason: "too-large",
+            }
+        }
+
         if (isRedirecting) {
             return {
                 isSubmitDisabled: true,
@@ -157,7 +248,7 @@ const ChatBoxComponent = ({
             isSubmitDisabledReason: undefined,
         }
 
-    }, [editor.children, isRedirecting, isTurnInProgress, selectedLanguageModel])
+    }, [editor.children, isRedirecting, isTurnInProgress, selectedLanguageModel, attachments])
 
     const {
         requiresLogin,
@@ -178,6 +269,11 @@ const ChatBoxComponent = ({
                     description: "⚠️ You must select a language model",
                     variant: "destructive",
                 });
+            } else if (isSubmitDisabledReason === "too-large") {
+                toast({
+                    description: `⚠️ Message and attachments exceed the ${Math.round(ATTACHMENT_MAX_TURN_TEXT_BYTES / 1024)}KB per-message limit. Remove a file or shorten the text.`,
+                    variant: "destructive",
+                });
             }
 
             return;
@@ -186,7 +282,7 @@ const ChatBoxComponent = ({
         if (requiresLogin) {
             sessionStorage.setItem(
                 PENDING_CHAT_SUBMISSION_SESSION_STORAGE_KEY,
-                JSON.stringify({ pathname, children: editor.children }),
+                JSON.stringify({ pathname, children: editor.children, attachments: attachments.map(toAttachmentData) }),
             );
             captureEvent('wa_askgh_login_wall_prompted', {});
             setIsLoginDialogOpen(true);
@@ -196,13 +292,15 @@ const ChatBoxComponent = ({
         if (requiresUpgrade) {
             sessionStorage.setItem(
                 PENDING_CHAT_SUBMISSION_SESSION_STORAGE_KEY,
-                JSON.stringify({ pathname, children: editor.children }),
+                JSON.stringify({ pathname, children: editor.children, attachments: attachments.map(toAttachmentData) }),
             );
             setIsUpsellDialogOpen(true);
             return;
         }
 
-        _onSubmit(editor.children, editor);
+        _onSubmit(editor.children, editor, attachments.map(toAttachmentData));
+        setSubmittedAttachments(attachments);
+        setAttachments([]);
     }, [
         isSubmitDisabled,
         requiresLogin,
@@ -212,7 +310,8 @@ const ChatBoxComponent = ({
         isSubmitDisabledReason,
         toast,
         pathname,
-        captureEvent
+        captureEvent,
+        attachments
     ]);
 
     useEffect(() => {
@@ -229,13 +328,17 @@ const ChatBoxComponent = ({
         }
 
         try {
-            const { pathname: storedPathname, children } = JSON.parse(stored) as { pathname: string; children: Descendant[] };
+            const { pathname: storedPathname, children, attachments: storedAttachments = [] } = JSON.parse(stored) as {
+                pathname: string;
+                children: Descendant[];
+                attachments?: AttachmentData[];
+            };
             if (storedPathname !== pathname) {
                 return;
             }
 
             sessionStorage.removeItem(PENDING_CHAT_SUBMISSION_SESSION_STORAGE_KEY);
-            _onSubmit(children, editor);
+            _onSubmit(children, editor, storedAttachments);
         } catch (error) {
             console.error('Failed to restore pending chat submission:', error);
             sessionStorage.removeItem(PENDING_CHAT_SUBMISSION_SESSION_STORAGE_KEY);
@@ -274,6 +377,16 @@ const ChatBoxComponent = ({
     }, [editor, range]);
 
     const onKeyDown = useCallback((event: KeyboardEvent<HTMLDivElement>) => {
+        // Detect the OS raw-paste chord so the upcoming `paste` event can skip
+        // the large-paste auto-conversion and insert inline instead.
+        if (
+            (event.key === 'v' || event.key === 'V') &&
+            event.shiftKey &&
+            (isMac ? event.metaKey : event.ctrlKey)
+        ) {
+            rawPasteRequestedRef.current = true;
+        }
+
         if (suggestionMode === "none") {
             switch (event.key) {
                 case 'Enter': {
@@ -320,7 +433,7 @@ const ChatBoxComponent = ({
                 }
             }
         }
-    }, [suggestionMode, suggestions, onSubmit, editor, index, onInsertSuggestion]);
+    }, [suggestionMode, suggestions, onSubmit, editor, index, onInsertSuggestion, isMac]);
 
     useEffect(() => {
         if (!range || !suggestionsBoxRef.current) {
@@ -364,6 +477,13 @@ const ChatBoxComponent = ({
             <div
                 className={cn("flex flex-col justify-between gap-0.5 w-full px-3 py-2", className)}
             >
+                {(isRedirecting ? submittedAttachments : attachments).length > 0 && (
+                    <AttachmentTray
+                        attachments={isRedirecting ? submittedAttachments : attachments}
+                        onRemove={isRedirecting ? undefined : removeAttachment}
+                        className="mb-1.5"
+                    />
+                )}
                 <Editable
                     className="w-full focus-visible:outline-none focus-visible:ring-0 bg-background text-base disabled:cursor-not-allowed disabled:opacity-50 md:text-sm max-h-64 overflow-y-auto"
                     placeholder="Ask a question about your code. @mention files or select search scopes to refine your query."
@@ -371,8 +491,38 @@ const ChatBoxComponent = ({
                     renderLeaf={renderLeaf}
                     onKeyDown={onKeyDown}
                     readOnly={isDisabled}
+                    onPaste={(event) => {
+                        const clipboardData = event.clipboardData;
+                        const files = clipboardData?.files ? Array.from(clipboardData.files) : [];
+                        if (files.length > 0) {
+                            event.preventDefault();
+                            void onAddFiles(files);
+                            return;
+                        }
+
+                        // A raw-paste chord (⌘⇧V / Ctrl+Shift+V) bypasses
+                        // auto-conversion for this one paste. Consume the flag
+                        // regardless so it never leaks into the next paste.
+                        const rawPasteRequested = rawPasteRequestedRef.current;
+                        rawPasteRequestedRef.current = false;
+                        if (rawPasteRequested) {
+                            return;
+                        }
+
+                        const text = clipboardData?.getData('text/plain') ?? '';
+                        if (!shouldAutoConvertPaste(text)) {
+                            return;
+                        }
+
+                        event.preventDefault();
+                        onAddPastedText(text);
+                    }}
                 />
-                <div className="ml-auto z-10">
+                <div className="flex flex-row items-center justify-end gap-1 z-10">
+                    <AttachmentButton
+                        onAddFiles={onAddFiles}
+                        disabled={isDisabled || isRedirecting || isTurnInProgress}
+                    />
                     {isRedirecting ? (
                         <Button
                             variant="default"
@@ -455,7 +605,7 @@ const ChatBoxComponent = ({
     )
 }
 
-export const ChatBox = memo(ChatBoxComponent, isEqual);
+export const ChatBox = memo(forwardRef(ChatBoxComponent), isEqual);
 
 const DefaultElement = (props: RenderElementProps) => {
     return <p {...props.attributes}>{props.children}</p>
diff --git a/packages/web/src/features/chat/components/chatBox/chatPaneDropzone.tsx b/packages/web/src/features/chat/components/chatBox/chatPaneDropzone.tsx
new file mode 100644
index 000000000..f7b5d0f59
--- /dev/null
+++ b/packages/web/src/features/chat/components/chatBox/chatPaneDropzone.tsx
@@ -0,0 +1,96 @@
+'use client';
+
+import { useToast } from "@/components/hooks/use-toast";
+import { getAttachmentDropzoneAccept } from "@/features/chat/attachmentUtils";
+import { cn } from "@/lib/utils";
+import { FileUp } from "lucide-react";
+import { ReactNode, useEffect, useState } from "react";
+import { useDropzone } from "react-dropzone";
+
+interface ChatPaneDropzoneProps {
+    onFilesDropped: (files: File[]) => void;
+    disabled?: boolean;
+    className?: string;
+    children: ReactNode;
+}
+
+// Makes an entire chat pane a drag-and-drop target for attachments. Drops are
+// forwarded to the chat box (which owns attachment state) via `onFilesDropped`.
+// `noClick`/`noKeyboard` keep the zone from hijacking clicks/keys; the file
+// picker is opened separately from the attachment button.
+export const ChatPaneDropzone = ({ onFilesDropped, disabled, className, children }: ChatPaneDropzoneProps) => {
+    const { toast } = useToast();
+    // Only surface the overlay when actual files are being dragged (not, e.g., a
+    // text selection dragged within the editor). `dragFileCount` is the number of
+    // files in the active drag (when the browser exposes it).
+    const [isDraggingFiles, setIsDraggingFiles] = useState(false);
+    const [dragFileCount, setDragFileCount] = useState(0);
+
+    const { getRootProps, getInputProps, isDragActive, isDragReject } = useDropzone({
+        accept: getAttachmentDropzoneAccept(),
+        multiple: true,
+        noClick: true,
+        noKeyboard: true,
+        disabled,
+        onDrop: (acceptedFiles, fileRejections) => {
+            setIsDraggingFiles(false);
+            if (acceptedFiles.length > 0) {
+                onFilesDropped(acceptedFiles);
+            }
+            if (fileRejections.length > 0) {
+                toast({
+                    description: `⚠️ Unsupported file type: ${fileRejections.map((rejection) => rejection.file.name).join(', ')}. Text files only.`,
+                    variant: "destructive",
+                });
+            }
+        },
+    });
+
+    // react-dropzone clears `isDragActive` when the drag leaves; mirror that for
+    // our files flag so the overlay never gets stuck.
+    useEffect(() => {
+        if (!isDragActive) {
+            setIsDraggingFiles(false);
+            setDragFileCount(0);
+        }
+    }, [isDragActive]);
+
+    const showOverlay = isDragActive && isDraggingFiles && !disabled;
+
+    return (
+        <div
+            {...getRootProps({
+                className: cn("relative", className),
+                onDragEnter: (event) => {
+                    const types = event.dataTransfer?.types ?? [];
+                    setIsDraggingFiles(types.includes('Files'));
+                    const items = event.dataTransfer?.items;
+                    setDragFileCount(items ? Array.from(items).filter((item) => item.kind === 'file').length : 0);
+                },
+            })}
+        >
+            <input {...getInputProps()} />
+            {showOverlay && (
+                <div className="absolute inset-0 z-30 flex items-center justify-center rounded-md bg-background/70 backdrop-blur-sm pointer-events-none animate-in fade-in-0 duration-150">
+                    <div
+                        className={cn(
+                            "flex flex-col items-center gap-2 rounded-xl border-2 border-dashed px-8 py-6 shadow-lg animate-in fade-in-0 zoom-in-95 duration-150",
+                            isDragReject ? "border-destructive bg-destructive/5" : "border-primary bg-primary/5",
+                        )}
+                    >
+                        <FileUp className={cn("w-8 h-8", isDragReject ? "text-destructive" : "text-primary")} />
+                        <span className="text-lg font-medium text-foreground">
+                            {isDragReject ? "Unsupported file type" : "Drop to attach"}
+                        </span>
+                        {dragFileCount > 0 && (
+                            <span className="text-xs text-muted-foreground">
+                                {dragFileCount} file{dragFileCount === 1 ? '' : 's'}
+                            </span>
+                        )}
+                    </div>
+                </div>
+            )}
+            {children}
+        </div>
+    )
+}
diff --git a/packages/web/src/features/chat/components/chatBox/index.ts b/packages/web/src/features/chat/components/chatBox/index.ts
index 94fcf52fc..b35b49675 100644
--- a/packages/web/src/features/chat/components/chatBox/index.ts
+++ b/packages/web/src/features/chat/components/chatBox/index.ts
@@ -1 +1,2 @@
-export { ChatBox } from "./chatBox";
\ No newline at end of file
+export { ChatBox } from "./chatBox";
+export type { ChatBoxHandle } from "./chatBox";
diff --git a/packages/web/src/features/chat/constants.ts b/packages/web/src/features/chat/constants.ts
index db518d2aa..1306bb7a5 100644
--- a/packages/web/src/features/chat/constants.ts
+++ b/packages/web/src/features/chat/constants.ts
@@ -12,3 +12,35 @@ export const SET_CHAT_STATE_SESSION_STORAGE_KEY = 'setChatState';
 export const PENDING_CHAT_SUBMISSION_SESSION_STORAGE_KEY = 'pendingChatSubmission';
 export const DISABLED_MCP_SERVER_IDS_LOCAL_STORAGE_KEY = 'disabledMcpServerIds';
 export const MCP_OAUTH_DRAFT_SESSION_STORAGE_KEY = 'mcpOAuthDraft';
+
+// Single upper bound on the total attachment text submitted per turn (text is
+// inlined and re-emitted every turn). ~256KB ≈ 65-85K tokens: enough for a few
+// files or a large log while leaving room for retrieval, history, and output.
+export const ATTACHMENT_MAX_TURN_TEXT_BYTES = 256 * 1024; // 256KB per turn
+
+// A plain-text paste at or above either of these thresholds is automatically
+// converted into a text attachment instead of being inserted inline
+export const ATTACHMENT_PASTE_AUTO_CONVERT_MIN_CHARS = 1500;
+export const ATTACHMENT_PASTE_AUTO_CONVERT_MIN_LINES = 15;
+
+// Allowlist for inline-text attachments. Files are accepted if their MIME type
+// starts with `text/`, exactly matches an entry here, or their extension is in
+// ATTACHMENT_ALLOWED_TEXT_EXTENSIONS. Many code files report an empty MIME type
+// in the browser, hence the extension fallback.
+export const ATTACHMENT_ALLOWED_TEXT_MIME_TYPES = [
+    'application/json',
+    'application/xml',
+    'application/x-yaml',
+    'application/yaml',
+    'application/csv',
+    'application/toml',
+];
+
+export const ATTACHMENT_ALLOWED_TEXT_EXTENSIONS = [
+    'txt', 'md', 'markdown', 'log', 'csv', 'tsv', 'json', 'jsonl', 'yaml', 'yml',
+    'toml', 'ini', 'cfg', 'conf', 'env', 'xml', 'html', 'css', 'scss',
+    'js', 'jsx', 'ts', 'tsx', 'mjs', 'cjs', 'py', 'rb', 'go', 'rs', 'java',
+    'kt', 'kts', 'c', 'h', 'cpp', 'cc', 'hpp', 'cs', 'php', 'swift', 'scala',
+    'sh', 'bash', 'zsh', 'sql', 'graphql', 'gql', 'proto', 'dockerfile',
+    'gitignore', 'tf', 'tfvars', 'lua', 'r', 'pl', 'dart', 'vue', 'svelte',
+];
diff --git a/packages/web/src/features/chat/types.ts b/packages/web/src/features/chat/types.ts
index 659551d4f..321a1b915 100644
--- a/packages/web/src/features/chat/types.ts
+++ b/packages/web/src/features/chat/types.ts
@@ -103,6 +103,24 @@ export type SBChatMessageToolTypes = {
     };
 };
 
+// A user-provided file attachment. The `text` variant carries the file's
+// extracted text inline (used for text/code/structured files); binary
+// attachments (images, PDFs) will later add a `blob` variant that references
+// stored bytes by id instead of inlining them.
+export const textAttachmentSchema = z.object({
+    kind: z.literal('text'),
+    filename: z.string(),
+    mediaType: z.string(),
+    sizeBytes: z.number(),
+    text: z.string(),
+});
+export type TextAttachment = z.infer<typeof textAttachmentSchema>;
+
+export const attachmentDataSchema = z.discriminatedUnion('kind', [
+    textAttachmentSchema,
+]);
+export type AttachmentData = z.infer<typeof attachmentDataSchema>;
+
 export type SBChatMessageDataParts = {
     // The `source` data type allows us to know what sources the LLM saw
     // during retrieval.
@@ -112,6 +130,8 @@ export type SBChatMessageDataParts = {
     "mcp-server": { sanitizedName: string; faviconUrl: string },
     // The `mcp-failed-server` data type surfaces MCP servers that failed to load their tools.
     "mcp-failed-server": { serverName: string },
+    // A user-provided file attachment included with the message.
+    "attachment": AttachmentData,
 }
 
 export type SBChatMessage = UIMessage<
diff --git a/packages/web/src/features/chat/useCreateNewChatThread.ts b/packages/web/src/features/chat/useCreateNewChatThread.ts
index f030f186d..ef5018ccf 100644
--- a/packages/web/src/features/chat/useCreateNewChatThread.ts
+++ b/packages/web/src/features/chat/useCreateNewChatThread.ts
@@ -9,7 +9,7 @@ import { useRouter } from "next/navigation";
 import { createChat } from "./actions";
 import { isServiceError } from "@/lib/utils";
 import { createPathWithQueryParams } from "@/lib/utils";
-import { SearchScope, SetChatStatePayload } from "./types";
+import { AttachmentData, SearchScope, SetChatStatePayload } from "./types";
 import { DISABLED_MCP_SERVER_IDS_LOCAL_STORAGE_KEY, SELECTED_SEARCH_SCOPES_LOCAL_STORAGE_KEY, SET_CHAT_STATE_SESSION_STORAGE_KEY } from "./constants";
 import { useSessionStorage } from "usehooks-ts";
 
@@ -19,7 +19,7 @@ export const useCreateNewChatThread = () => {
     const router = useRouter();
     const [, setChatState] = useSessionStorage<SetChatStatePayload | null>(SET_CHAT_STATE_SESSION_STORAGE_KEY, null);
 
-    const createNewChatThread = useCallback(async (children: Descendant[], overrideSearchScopes?: SearchScope[], overrideDisabledMcpServerIds?: string[]) => {
+    const createNewChatThread = useCallback(async (children: Descendant[], overrideSearchScopes?: SearchScope[], overrideDisabledMcpServerIds?: string[], attachments: AttachmentData[] = []) => {
         const text = slateContentToString(children);
         const mentions = getAllMentionElements(children);
 
@@ -41,7 +41,7 @@ export const useCreateNewChatThread = () => {
 
         const selectedSearchScopes = overrideSearchScopes ?? storedScopes;
         const disabledMcpServerIds = overrideDisabledMcpServerIds ?? storedDisabledMcpServerIds;
-        const inputMessage = createUIMessage(text, mentions.map((mention) => mention.data), selectedSearchScopes, disabledMcpServerIds);
+        const inputMessage = createUIMessage(text, mentions.map((mention) => mention.data), selectedSearchScopes, disabledMcpServerIds, attachments);
 
         setIsLoading(true);
         const response = await createChat({ source: 'sourcebot-web-client' });
diff --git a/packages/web/src/features/chat/utils.ts b/packages/web/src/features/chat/utils.ts
index 108bd9cc2..15a4907ff 100644
--- a/packages/web/src/features/chat/utils.ts
+++ b/packages/web/src/features/chat/utils.ts
@@ -4,6 +4,7 @@ import type { ChatStatus, DynamicToolUIPart, ToolUIPart } from "ai";
 import { Descendant, Editor, Point, Range, Transforms } from "slate";
 import { ANSWER_TAG, FILE_REFERENCE_PREFIX, FILE_REFERENCE_REGEX } from "./constants";
 import {
+    AttachmentData,
     CustomEditor,
     CustomText,
     FileReference,
@@ -187,7 +188,7 @@ export const addLineNumbers = (source: string, lineOffset = 1) => {
     return source.split('\n').map((line, index) => `${index + lineOffset}: ${line}`).join('\n');
 }
 
-export const createUIMessage = (text: string, mentions: MentionData[], selectedSearchScopes: SearchScope[], disabledMcpServerIds: string[] = []): CreateUIMessage<SBChatMessage> => {
+export const createUIMessage = (text: string, mentions: MentionData[], selectedSearchScopes: SearchScope[], disabledMcpServerIds: string[] = [], attachments: AttachmentData[] = []): CreateUIMessage<SBChatMessage> => {
     // Converts applicable mentions into sources.
     const sources: Source[] = mentions
         .map((mention) => {
@@ -217,6 +218,10 @@ export const createUIMessage = (text: string, mentions: MentionData[], selectedS
                 type: 'data-source',
                 data,
             })) as UIMessagePart<{ source: Source }, SBChatMessageToolTypes>[],
+            ...attachments.map((data) => ({
+                type: 'data-attachment',
+                data,
+            })) as UIMessagePart<{ attachment: AttachmentData }, SBChatMessageToolTypes>[],
         ],
         metadata: {
             selectedSearchScopes,
@@ -405,6 +410,42 @@ export const getUserMessageText = (message: Pick<SBChatMessage, 'parts'>): strin
     return message.parts.find((part) => part.type === 'text')?.text ?? '';
 }
 
+// Extracts the inline-text attachments a user included with a message.
+export const getUserMessageAttachments = (message: Pick<SBChatMessage, 'parts'>): AttachmentData[] => {
+    return message.parts
+        .filter((part) => part.type === 'data-attachment')
+        .map((part) => part.data);
+}
+
+// Neutralizes `</attachment>`/`</attachments>` sequences in a body so it can't
+// close its own wrapper early. Unrelated markup (e.g. `</div>`) is left intact.
+const escapeAttachmentBody = (text: string): string => {
+    return text.replace(/<(\/attachments?>)/gi, '&lt;$1');
+}
+
+// Formats a user message's text attachments into a delimited block to inline
+// into the turn's content. Returns '' when there are none. Size is bounded at
+// submit, so nothing is truncated here.
+export const formatAttachmentsForPrompt = (attachments: AttachmentData[]): string => {
+    const textAttachments = attachments.filter((attachment) => attachment.kind === 'text');
+    if (textAttachments.length === 0) {
+        return '';
+    }
+
+    const blocks = textAttachments.map((attachment) => {
+        const text = escapeAttachmentBody(attachment.text);
+        // Keep the filename on a single line and escape quotes so the body
+        // can't break out of the tag (the client also sanitizes via
+        // sanitizeFilename).
+        const filename = attachment.filename
+            .replace(/\s+/g, ' ')
+            .replace(/"/g, '&quot;');
+        return `<attachment filename="${filename}" media-type="${attachment.mediaType}">\n${text}\n</attachment>`;
+    });
+
+    return `<attachments>\n${blocks.join('\n')}\n</attachments>`;
+}
+
 // Attempts to find the part of the assistant's message
 // that contains the answer.
 export const getAnswerPartFromAssistantMessage = (message: SBChatMessage, isTurnInProgress: boolean): TextUIPart | undefined => {
diff --git a/yarn.lock b/yarn.lock
index ce21f594b..c0c1cb7ad 100644
--- a/yarn.lock
+++ b/yarn.lock
@@ -9512,6 +9512,7 @@ __metadata:
     react-day-picker: "npm:^9.14.0"
     react-device-detect: "npm:^2.2.3"
     react-dom: "npm:19.2.4"
+    react-dropzone: "npm:^15.0.0"
     react-email: "npm:^6.1.4"
     react-grab: "npm:^0.1.23"
     react-hook-form: "npm:^7.53.0"
@@ -9542,6 +9543,7 @@ __metadata:
     typescript-eslint: "npm:^8.56.1"
     use-stick-to-bottom: "npm:^1.1.3"
     usehooks-ts: "npm:^3.1.0"
+    uuid: "npm:^14.0.0"
     vite-tsconfig-paths: "npm:^5.1.3"
     vitest: "npm:^4.1.4"
     vitest-mock-extended: "npm:^4.0.0"
@@ -11634,6 +11636,13 @@ __metadata:
   languageName: node
   linkType: hard
 
+"attr-accept@npm:^2.2.4":
+  version: 2.2.5
+  resolution: "attr-accept@npm:2.2.5"
+  checksum: 10c0/9b4cb82213925cab2d568f71b3f1c7a7778f9192829aac39a281e5418cd00c04a88f873eb89f187e0bf786fa34f8d52936f178e62cbefb9254d57ecd88ada99b
+  languageName: node
+  linkType: hard
+
 "available-typed-arrays@npm:^1.0.7":
   version: 1.0.7
   resolution: "available-typed-arrays@npm:1.0.7"
@@ -15092,6 +15101,15 @@ __metadata:
   languageName: node
   linkType: hard
 
+"file-selector@npm:^2.1.0":
+  version: 2.1.2
+  resolution: "file-selector@npm:2.1.2"
+  dependencies:
+    tslib: "npm:^2.7.0"
+  checksum: 10c0/fe827e0e95410aacfcc3eabc38c29cc36055257f03c1c06b631a2b5af9730c142ad2c52f5d64724d02231709617bda984701f52bd1f4b7aca50fb6585a27c1d2
+  languageName: node
+  linkType: hard
+
 "fill-range@npm:^7.1.1":
   version: 7.1.1
   resolution: "fill-range@npm:7.1.1"
@@ -20476,6 +20494,19 @@ __metadata:
   languageName: node
   linkType: hard
 
+"react-dropzone@npm:^15.0.0":
+  version: 15.0.0
+  resolution: "react-dropzone@npm:15.0.0"
+  dependencies:
+    attr-accept: "npm:^2.2.4"
+    file-selector: "npm:^2.1.0"
+    prop-types: "npm:^15.8.1"
+  peerDependencies:
+    react: ">= 16.8 || 18.0.0"
+  checksum: 10c0/fb7b48a709fdd26273707f7aca5c0e77fce2b9c9201122645d3ecfb07ecfbb89e2495273ea141994f0ed0838ee79f27832c0855b2c598b377b342c3965608b54
+  languageName: node
+  linkType: hard
+
 "react-email@npm:^6.1.4":
   version: 6.1.4
   resolution: "react-email@npm:6.1.4"
@@ -23231,7 +23262,7 @@ __metadata:
   languageName: node
   linkType: hard
 
-"tslib@npm:^2.0.0, tslib@npm:^2.1.0, tslib@npm:^2.4.0, tslib@npm:^2.6.2, tslib@npm:^2.8.0, tslib@npm:^2.8.1":
+"tslib@npm:^2.0.0, tslib@npm:^2.1.0, tslib@npm:^2.4.0, tslib@npm:^2.6.2, tslib@npm:^2.7.0, tslib@npm:^2.8.0, tslib@npm:^2.8.1":
   version: 2.8.1
   resolution: "tslib@npm:2.8.1"
   checksum: 10c0/9c4759110a19c53f992d9aae23aac5ced636e99887b51b9e61def52611732872ff7668757d4e4c61f19691e36f4da981cd9485e869b4a7408d689f6bf1f14e62