diff --git a/docs/floating-ai-integration-guide.md b/docs/floating-ai-integration-guide.md
index 64f3b68..69b14a6 100644
--- a/docs/floating-ai-integration-guide.md
+++ b/docs/floating-ai-integration-guide.md
@@ -33,8 +33,8 @@ Steps MUST be implemented in order. Each step lists its prerequisites.
 |------|-------|--------|
 | 1 | Extract shared `useAIChat` hook | [x] 2026-02-27 |
 | 2 | Create section registry + `FloatingChatContext` | [x] 2026-02-27 |
-| 3 | Create double-click hook | [ ] |
-| 4 | Build `FloatingChat` component | [ ] |
+| 3 | Create double-click hook | [x] 2026-02-27 |
+| 4 | Build `FloatingChat` component | [x] 2026-02-27 |
 | 5 | Add `ai:action` IPC side-channel | [ ] |
 | 6 | Pass `uiContext` through to the AI | [ ] |
 | 7 | Implement morph animation (FLIP) | [ ] |
@@ -452,7 +452,7 @@ function AppShellInner({ children }: AppShellProps) {
 
 ## Step 4: Build `FloatingChat` Component
 
-**Status**: [ ]
+**Status**: [x] 2026-02-27
 **Prerequisites**: Steps 1-3 completed
 **Creates**: `src/renderer/components/ai/FloatingChat.tsx`
 **Modifies**: `src/renderer/components/layout/AppShell.tsx` (render the portal)
diff --git a/src/renderer/components/ai/AIChatPanel.tsx b/src/renderer/components/ai/AIChatPanel.tsx
index 5059b6a..3443a62 100644
--- a/src/renderer/components/ai/AIChatPanel.tsx
+++ b/src/renderer/components/ai/AIChatPanel.tsx
@@ -461,7 +461,7 @@ function ChatInput({
 
 /* ---------- ChatMarkdown: lightweight markdown renderer ---------- */
 
-function ChatMarkdown({ content }: { content: string }) {
+export function ChatMarkdown({ content }: { content: string }) {
   return (
     <div className="prose prose-sm dark:prose-invert max-w-none [&>*:first-child]:mt-0 [&>*:last-child]:mb-0">
       <ReactMarkdown
diff --git a/src/renderer/components/ai/FloatingChat.tsx b/src/renderer/components/ai/FloatingChat.tsx
new file mode 100644
index 0000000..bc30cb5
--- /dev/null
+++ b/src/renderer/components/ai/FloatingChat.tsx
@@ -0,0 +1,339 @@
+import { useCallback, useEffect, useMemo, useRef, useState } from 'react';
+import { createPortal } from 'react-dom';
+import { AnimatePresence, motion } from 'framer-motion';
+import { useRouterState } from '@tanstack/react-router';
+import { X, ArrowUp, Sparkles, GripHorizontal } from 'lucide-react';
+import {
+  useFloatingChat,
+  CHAT_WIDTH,
+  CHAT_HEIGHT,
+  PADDING,
+} from '@/context/FloatingChatContext';
+import { useAIChat, type ChatContext } from '@/hooks/useAIChat';
+import { ChatMarkdown } from '@/components/ai/AIChatPanel';
+import { Badge } from '@/components/ui/badge';
+import { ScrollArea } from '@/components/ui/scroll-area';
+import { Skeleton } from '@/components/ui/skeleton';
+
+interface DragState {
+  startX: number;
+  startY: number;
+  originX: number;
+  originY: number;
+}
+
+function FloatingChatInner() {
+  const { state, sections, close } = useFloatingChat();
+  const routerState = useRouterState();
+  const prevPathRef = useRef(routerState.location.pathname);
+
+  // Active section lookup
+  const activeSection = sections.get(state.activeSectionId ?? '');
+
+  // Chat context derived from active section
+  const chatContext = useMemo<ChatContext>(
+    () => ({
+      type: activeSection?.projectId ? 'project' : 'global',
+      projectId: activeSection?.projectId,
+      uiContext: activeSection?.label,
+    }),
+    [activeSection?.projectId, activeSection?.label],
+  );
+
+  const {
+    messages,
+    input,
+    setInput,
+    isStreaming,
+    streamingContent,
+    handleSend,
+    clearMessages,
+  } = useAIChat(chatContext);
+
+  // ---- Position & drag state ----
+
+  const containerRef = useRef<HTMLDivElement>(null);
+  const headerRef = useRef<HTMLDivElement>(null);
+  const dragRef = useRef<DragState | null>(null);
+  const posRef = useRef({ x: state.position.x, y: state.position.y });
+  const [posState, setPosState] = useState({
+    x: state.position.x,
+    y: state.position.y,
+  });
+
+  // Sync from context when position changes externally (new section opened)
+  useEffect(() => {
+    posRef.current = { x: state.position.x, y: state.position.y };
+    setPosState({ x: state.position.x, y: state.position.y });
+  }, [state.position.x, state.position.y]);
+
+  // ---- Drag handlers ----
+
+  const onPointerDown = useCallback((e: React.PointerEvent) => {
+    e.preventDefault();
+    headerRef.current?.setPointerCapture(e.pointerId);
+    dragRef.current = {
+      startX: e.clientX,
+      startY: e.clientY,
+      originX: posRef.current.x,
+      originY: posRef.current.y,
+    };
+  }, []);
+
+  const onPointerMove = useCallback((e: React.PointerEvent) => {
+    const d = dragRef.current;
+    if (!d) return;
+
+    const dx = e.clientX - d.startX;
+    const dy = e.clientY - d.startY;
+
+    let newX = d.originX + dx;
+    let newY = d.originY + dy;
+
+    newX = Math.max(
+      PADDING,
+      Math.min(newX, window.innerWidth - CHAT_WIDTH - PADDING),
+    );
+    newY = Math.max(
+      PADDING,
+      Math.min(newY, window.innerHeight - CHAT_HEIGHT - PADDING),
+    );
+
+    posRef.current = { x: newX, y: newY };
+
+    const el = containerRef.current;
+    if (el) {
+      el.style.left = `${newX}px`;
+      el.style.top = `${newY}px`;
+    }
+  }, []);
+
+  const onPointerUp = useCallback(() => {
+    if (!dragRef.current) return;
+    dragRef.current = null;
+    setPosState({ ...posRef.current });
+  }, []);
+
+  // ---- Close on Escape ----
+
+  useEffect(() => {
+    if (!state.isOpen) return;
+    const handler = (e: KeyboardEvent) => {
+      if (e.key === 'Escape') {
+        e.stopPropagation();
+        close();
+      }
+    };
+    document.addEventListener('keydown', handler);
+    return () => document.removeEventListener('keydown', handler);
+  }, [state.isOpen, close]);
+
+  // ---- Close on route change ----
+
+  useEffect(() => {
+    const currentPath = routerState.location.pathname;
+    if (prevPathRef.current !== currentPath && state.isOpen) {
+      close();
+    }
+    prevPathRef.current = currentPath;
+  }, [routerState.location.pathname, state.isOpen, close]);
+
+  // ---- Clear messages on close ----
+
+  const prevOpenRef = useRef(state.isOpen);
+  useEffect(() => {
+    if (prevOpenRef.current && !state.isOpen) {
+      clearMessages();
+    }
+    prevOpenRef.current = state.isOpen;
+  }, [state.isOpen, clearMessages]);
+
+  // ---- Window resize: keep within bounds ----
+
+  useEffect(() => {
+    if (!state.isOpen) return;
+    const handler = () => {
+      const pos = posRef.current;
+      const clampedX = Math.max(
+        PADDING,
+        Math.min(pos.x, window.innerWidth - CHAT_WIDTH - PADDING),
+      );
+      const clampedY = Math.max(
+        PADDING,
+        Math.min(pos.y, window.innerHeight - CHAT_HEIGHT - PADDING),
+      );
+      posRef.current = { x: clampedX, y: clampedY };
+      setPosState({ x: clampedX, y: clampedY });
+    };
+    window.addEventListener('resize', handler);
+    return () => window.removeEventListener('resize', handler);
+  }, [state.isOpen]);
+
+  // ---- Auto-scroll messages ----
+
+  const scrollRef = useRef<HTMLDivElement>(null);
+  const scrollToBottom = useCallback(() => {
+    const el = scrollRef.current;
+    if (el) el.scrollTo({ top: el.scrollHeight });
+  }, []);
+
+  useEffect(() => {
+    scrollToBottom();
+  }, [messages, streamingContent, scrollToBottom]);
+
+  // ---- Auto-focus input on open ----
+
+  const inputRef = useRef<HTMLTextAreaElement>(null);
+  useEffect(() => {
+    if (state.isOpen) {
+      const timer = setTimeout(() => inputRef.current?.focus(), 100);
+      return () => clearTimeout(timer);
+    }
+  }, [state.isOpen]);
+
+  // ---- Input handling ----
+
+  const handleKeyDown = (e: React.KeyboardEvent<HTMLTextAreaElement>) => {
+    if (e.key === 'Enter' && !e.shiftKey) {
+      e.preventDefault();
+      handleSend();
+    }
+  };
+
+  return (
+    <AnimatePresence>
+      {state.isOpen && (
+        <motion.div
+          ref={containerRef}
+          key="floating-chat"
+          layout
+          layoutId={state.morphTargetId ?? undefined}
+          initial={{ opacity: 0, scale: 0.92, y: 8 }}
+          animate={{ opacity: 1, scale: 1, y: 0 }}
+          exit={{ opacity: 0, scale: 0.92, y: 8 }}
+          transition={{ type: 'spring', stiffness: 400, damping: 30 }}
+          style={{
+            position: 'fixed',
+            left: posState.x,
+            top: posState.y,
+            width: state.position.width,
+            height: CHAT_HEIGHT,
+            zIndex: 9999,
+          }}
+          className="rounded-xl border border-border bg-background/95 backdrop-blur-xl shadow-2xl flex flex-col overflow-hidden"
+        >
+          {/* ---- Header ---- */}
+          <div
+            ref={headerRef}
+            className="flex items-center gap-2 px-3 py-2 border-b border-border/50 cursor-grab active:cursor-grabbing select-none"
+            onPointerDown={onPointerDown}
+            onPointerMove={onPointerMove}
+            onPointerUp={onPointerUp}
+          >
+            <GripHorizontal
+              size={14}
+              className="text-muted-foreground shrink-0"
+            />
+            <Badge variant="outline" className="text-[10px] truncate">
+              {activeSection?.label ?? 'Chat'}
+            </Badge>
+            <button
+              onClick={close}
+              className="ml-auto flex h-6 w-6 items-center justify-center rounded-md hover:bg-muted transition-colors"
+            >
+              <X size={14} />
+            </button>
+          </div>
+
+          {/* ---- Messages ---- */}
+          <ScrollArea className="flex-1 min-h-0" viewportRef={scrollRef}>
+            <div className="flex flex-col gap-3 p-3">
+              {messages.map((msg) => {
+                if (msg.role === 'user') {
+                  return (
+                    <div key={msg.id} className="flex justify-end">
+                      <div className="ml-auto max-w-[85%] rounded-xl bg-muted px-3 py-1.5">
+                        <p className="text-xs whitespace-pre-wrap">
+                          {msg.content}
+                        </p>
+                      </div>
+                    </div>
+                  );
+                }
+
+                if (msg.error) {
+                  return (
+                    <div key={msg.id} className="mr-auto max-w-[85%]">
+                      <p className="text-xs text-destructive whitespace-pre-wrap">
+                        {msg.content}
+                      </p>
+                    </div>
+                  );
+                }
+
+                return (
+                  <div key={msg.id} className="mr-auto max-w-[85%]">
+                    <div className="flex items-center gap-1 mb-0.5">
+                      <Sparkles size={12} className="text-foreground" />
+                      <span className="text-[10px] font-semibold">Adiuva</span>
+                    </div>
+                    <div className="pl-4 text-xs">
+                      <ChatMarkdown content={msg.content} />
+                    </div>
+                  </div>
+                );
+              })}
+
+              {/* Streaming indicator */}
+              {isStreaming && (
+                <div className="mr-auto max-w-[85%]">
+                  <div className="flex items-center gap-1 mb-0.5">
+                    <Sparkles size={12} className="text-foreground" />
+                    <span className="text-[10px] font-semibold">Adiuva</span>
+                  </div>
+                  {streamingContent ? (
+                    <div className="pl-4 text-xs">
+                      <ChatMarkdown content={streamingContent} />
+                    </div>
+                  ) : (
+                    <div className="space-y-1.5 pl-4">
+                      <Skeleton className="h-3 w-36" />
+                      <Skeleton className="h-3 w-24" />
+                    </div>
+                  )}
+                </div>
+              )}
+            </div>
+          </ScrollArea>
+
+          {/* ---- Input bar ---- */}
+          <div className="border-t border-border/50 p-2">
+            <div className="flex items-center gap-1.5 rounded-lg bg-muted/50 px-2.5 py-1.5">
+              <textarea
+                ref={inputRef}
+                value={input}
+                onChange={(e) => setInput(e.target.value)}
+                onKeyDown={handleKeyDown}
+                placeholder="Ask about this section..."
+                rows={1}
+                className="flex-1 resize-none bg-transparent text-xs placeholder:text-muted-foreground outline-none max-h-16 overflow-y-auto"
+                style={{ fieldSizing: 'content' } as React.CSSProperties}
+              />
+              <button
+                onClick={() => handleSend()}
+                disabled={!input.trim() || isStreaming}
+                className="flex h-6 w-6 shrink-0 items-center justify-center rounded-md bg-primary text-primary-foreground transition-all hover:bg-primary/90 active:scale-95 disabled:opacity-40 disabled:cursor-not-allowed"
+              >
+                <ArrowUp size={12} />
+              </button>
+            </div>
+          </div>
+        </motion.div>
+      )}
+    </AnimatePresence>
+  );
+}
+
+export function FloatingChatPortal() {
+  return createPortal(<FloatingChatInner />, document.body);
+}
diff --git a/src/renderer/components/layout/AppShell.tsx b/src/renderer/components/layout/AppShell.tsx
index f8e7512..1641772 100644
--- a/src/renderer/components/layout/AppShell.tsx
+++ b/src/renderer/components/layout/AppShell.tsx
@@ -56,6 +56,7 @@ import {
 import { Input } from '@/components/ui/input';
 import { Button } from '@/components/ui/button';
 import { AIChatPanel } from '@/components/ai/AIChatPanel';
+import { FloatingChatPortal } from '@/components/ai/FloatingChat';
 import { useTheme } from '@/components/theme-provider';
 import { FloatingChatProvider } from '@/context/FloatingChatContext';
 
@@ -267,6 +268,9 @@ function AppShellInner({ children }: AppShellProps) {
       </SidebarInset>
     </SidebarProvider>
 
+    {/* Floating AI Chat — portal to document.body */}
+    <FloatingChatPortal />
+
     {/* AI Token Dialog — rendered outside Sidebar to avoid layout conflicts */}
     <Dialog open={tokenDialogOpen} onOpenChange={(open) => {
       setTokenDialogOpen(open);
diff --git a/src/renderer/context/FloatingChatContext.tsx b/src/renderer/context/FloatingChatContext.tsx
index 05978be..ded1c7b 100644
--- a/src/renderer/context/FloatingChatContext.tsx
+++ b/src/renderer/context/FloatingChatContext.tsx
@@ -44,9 +44,9 @@ interface FloatingChatContextValue {
 
 // ---------- Constants ----------
 
-const CHAT_WIDTH = 380;
-const CHAT_HEIGHT = 420;
-const PADDING = 16;
+export const CHAT_WIDTH = 380;
+export const CHAT_HEIGHT = 420;
+export const PADDING = 16;
 
 // ---------- Position computation ----------