diff --git a/components/layout/project-shell.tsx b/components/layout/project-shell.tsx
index 3adb5e3..89eac67 100644
--- a/components/layout/project-shell.tsx
+++ b/components/layout/project-shell.tsx
@@ -1,7 +1,7 @@
 "use client";
 
 import { usePathname, useSearchParams, useRouter } from "next/navigation";
-import { ReactNode, Suspense } from "react";
+import { ReactNode, Suspense, useRef, useState, useCallback } from "react";
 import Link from "next/link";
 import { signOut, useSession } from "next-auth/react";
 import { CooChat } from "./coo-chat";
@@ -24,7 +24,9 @@ interface ProjectShellProps {
   creationMode?: "fresh" | "chat-import" | "code-import" | "migration";
 }
 
-const CHAT_W = 320;
+const CHAT_W_DEFAULT = 320;
+const CHAT_W_MIN = 200;
+const CHAT_W_MAX = 560;
 
 const SECTIONS = [
   { id: "build",  label: "Build",  path: "build" },
@@ -61,6 +63,34 @@ function ProjectShellInner({
   const router = useRouter();
   const { data: session } = useSession();
 
+  const [chatWidth, setChatWidth] = useState(CHAT_W_DEFAULT);
+  const dragging = useRef(false);
+  const startX = useRef(0);
+  const startW = useRef(0);
+
+  const onDragStart = useCallback((e: React.MouseEvent) => {
+    dragging.current = true;
+    startX.current = e.clientX;
+    startW.current = chatWidth;
+    document.body.style.cursor = "col-resize";
+    document.body.style.userSelect = "none";
+
+    const onMove = (e: MouseEvent) => {
+      if (!dragging.current) return;
+      const delta = e.clientX - startX.current;
+      setChatWidth(Math.min(CHAT_W_MAX, Math.max(CHAT_W_MIN, startW.current + delta)));
+    };
+    const onUp = () => {
+      dragging.current = false;
+      document.body.style.cursor = "";
+      document.body.style.userSelect = "";
+      document.removeEventListener("mousemove", onMove);
+      document.removeEventListener("mouseup", onUp);
+    };
+    document.addEventListener("mousemove", onMove);
+    document.addEventListener("mouseup", onUp);
+  }, [chatWidth]);
+
   const activeSection =
     pathname?.includes("/build")  ? "build"  :
     pathname?.includes("/growth") ? "market" :
@@ -98,7 +128,7 @@ function ProjectShellInner({
 
           {/* Left — aligns with chat panel */}
           <div style={{
-            width: CHAT_W, flexShrink: 0,
+            width: chatWidth, flexShrink: 0,
             display: "flex", alignItems: "center",
             padding: "0 14px", gap: 9,
             borderRight: "1px solid #e8e4dc",
@@ -218,11 +248,11 @@ function ProjectShellInner({
 
           {/* Left: Assist chat — persistent */}
           <div style={{
-            width: CHAT_W, flexShrink: 0,
-            borderRight: "1px solid #e8e4dc",
+            width: chatWidth, flexShrink: 0,
             background: "#fff",
             display: "flex", flexDirection: "column",
             overflow: "hidden",
+            position: "relative",
           }}>
             <div style={{
               height: 44, flexShrink: 0,
@@ -245,6 +275,20 @@ function ProjectShellInner({
             <CooChat projectId={projectId} />
           </div>
 
+          {/* Drag handle */}
+          <div
+            onMouseDown={onDragStart}
+            style={{
+              width: 5, flexShrink: 0, cursor: "col-resize",
+              background: "transparent",
+              borderLeft: "1px solid #e8e4dc",
+              transition: "background 0.15s",
+              zIndex: 5,
+            }}
+            onMouseEnter={e => (e.currentTarget.style.background = "#e8e4dc")}
+            onMouseLeave={e => (e.currentTarget.style.background = "transparent")}
+          />
+
           {/* Right: content */}
           <div style={{ flex: 1, overflow: "hidden", minWidth: 0 }}>
             {children}