refactor: replace code mode tabs with persistent Browse | Agent split + collapsible terminal

Removes the Browse/Agent/Terminal tab switcher from the code section.
Browse (file tree + viewer) is now the left pane, Agent chat is a
fixed 420px right pane, and Terminal is a collapsible strip at the
bottom — all visible simultaneously.

Made-with: Cursor

app/[workspace]/project/[projectId]/build/page.tsx

@@ -211,31 +211,6 @@ function LayoutsContent({ surfaces, projectId, workspace, activeSurfaceId, onSel
 
 // ── Shared mode tab bar ───────────────────────────────────────────────────────
 
-type CodeMode = "browse" | "agent" | "terminal";
-
-function ModeTabs({ mode, onChange }: { mode: CodeMode; onChange: (m: CodeMode) => void }) {
-  const tabs: { id: CodeMode; label: string }[] = [
-    { id: "browse",   label: "Browse" },
-    { id: "agent",    label: "Agent" },
-    { id: "terminal", label: "Terminal" },
-  ];
-  return (
-    <div style={{ display: "flex", borderBottom: "1px solid #e8e4dc", background: "#fff", flexShrink: 0, padding: "0 16px" }}>
-      {tabs.map(t => (
-        <button key={t.id} onClick={() => onChange(t.id)} style={{
-          padding: "10px 14px", border: "none", background: "transparent", cursor: "pointer",
-          fontSize: "0.76rem", fontWeight: mode === t.id ? 600 : 450,
-          color: mode === t.id ? "#1a1a1a" : "#a09a90",
-          borderBottom: mode === t.id ? "2px solid #1a1a1a" : "2px solid transparent",
-          fontFamily: "Outfit, sans-serif", whiteSpace: "nowrap",
-        }}>
-          {t.label}
-        </button>
-      ))}
-    </div>
-  );
-}
-
 // ── Agent mode ────────────────────────────────────────────────────────────────
 
 interface AgentSession {
@@ -800,23 +775,39 @@ function AgentMode({ projectId, appName, appPath }: { projectId: string; appName
   );
 }
 
-// ── Terminal mode (Phase 4 placeholder) ───────────────────────────────────────
+// ── Terminal panel — collapsible bottom strip ─────────────────────────────────
+
+function TerminalPanel({ appName }: { appName: string }) {
+  const [open, setOpen] = useState(false);
+  const PANEL_HEIGHT = 220;
 
-function TerminalMode({ appName }: { appName: string }) {
   return (
-    <div style={{ flex: 1, display: "flex", flexDirection: "column", background: "#1a1a1a", overflow: "hidden" }}>
+    <div style={{ flexShrink: 0, borderTop: "1px solid #2d2d2d", background: "#1a1a1a", display: "flex", flexDirection: "column", height: open ? PANEL_HEIGHT : 32, transition: "height 0.2s ease", overflow: "hidden" }}>
-      <div style={{ flex: 1, display: "flex", alignItems: "center", justifyContent: "center", flexDirection: "column", gap: 14, padding: 40, textAlign: "center" }}>
+      {/* Header / toggle bar */}
-        <div style={{ width: 52, height: 52, borderRadius: 13, background: "#252526", display: "flex", alignItems: "center", justifyContent: "center", fontSize: "1.3rem" }}>⌨</div>
+      <button
-        <div>
+        onClick={() => setOpen(o => !o)}
-          <div style={{ fontSize: "0.88rem", fontWeight: 600, color: "#d4d4d4", marginBottom: 6, fontFamily: "Outfit, sans-serif" }}>Terminal — Phase 4</div>
+        style={{
-          <div style={{ fontSize: "0.78rem", color: "#6b6560", maxWidth: 300, lineHeight: 1.6, fontFamily: "Outfit, sans-serif" }}>
+          display: "flex", alignItems: "center", gap: 8, padding: "0 14px",
+          height: 32, flexShrink: 0, width: "100%", border: "none",
+          background: "transparent", cursor: "pointer", textAlign: "left",
+        }}
+      >
+        <span style={{ fontSize: "0.58rem", color: "#555", transform: open ? "rotate(180deg)" : "none", transition: "transform 0.2s", display: "inline-block" }}>▲</span>
+        <span style={{ fontSize: "0.68rem", fontWeight: 600, color: "#6b6560", letterSpacing: "0.07em", textTransform: "uppercase", fontFamily: "Outfit, sans-serif" }}>Terminal</span>
+        {appName && <span style={{ fontSize: "0.65rem", color: "#3a3a3a", fontFamily: "IBM Plex Mono, monospace" }}>{appName}</span>}
+        <span style={{ marginLeft: "auto", fontSize: "0.6rem", color: "#3a3a3a", fontFamily: "Outfit, sans-serif" }}>Phase 4</span>
+      </button>
+
+      {/* Body */}
+      {open && (
+        <div style={{ flex: 1, display: "flex", alignItems: "center", justifyContent: "center", flexDirection: "column", gap: 10, padding: "16px 24px", textAlign: "center" }}>
+          <div style={{ fontSize: "0.78rem", color: "#6b6560", lineHeight: 1.6, fontFamily: "Outfit, sans-serif", maxWidth: 340 }}>
             {appName
-              ? `A live shell into the ${appName} container via xterm.js + Theia PTY. Coming in Phase 4.`
+              ? `Live shell into the ${appName} container via xterm.js + Theia PTY — coming in Phase 4.`
-              : "Select an app first, then open a live shell into its container."}
+              : "Select an app from the left, then open a live shell into its container."}
           </div>
         </div>
-        <div style={{ marginTop: 4, padding: "7px 18px", background: "#252526", color: "#555", borderRadius: 7, fontSize: "0.77rem", fontFamily: "Outfit, sans-serif" }}>Coming in Phase 4</div>
+      )}
-      </div>
     </div>
   );
 }
@@ -968,12 +959,6 @@ function BuildHubInner() {
 
   const setSection = (s: string) => router.push(`/${workspace}/project/${projectId}/build?section=${s}`, { scroll: false });
 
-  const codeMode = (searchParams.get("mode") as CodeMode | null) ?? "browse";
-  const setCodeMode = (m: CodeMode) => {
-    const sp = new URLSearchParams({ section: "code", ...(activeApp ? { app: activeApp, root: activeRoot } : {}), mode: m });
-    router.push(`/${workspace}/project/${projectId}/build?${sp.toString()}`, { scroll: false });
-  };
-
   return (
     <div style={{ display: "flex", height: "100%", fontFamily: "Outfit, sans-serif", overflow: "hidden" }}>
 
@@ -1014,14 +999,38 @@ function BuildHubInner() {
 
       {/* ── Content ── */}
       <div style={{ flex: 1, display: "flex", flexDirection: "column", overflow: "hidden", minWidth: 0 }}>
+
+        {/* Code section — persistent split: Browse (left) | Agent (right), Terminal (bottom) */}
         {section === "code" && (
           <div style={{ flex: 1, display: "flex", flexDirection: "column", overflow: "hidden" }}>
-            <ModeTabs mode={codeMode} onChange={setCodeMode} />
+            {/* Main split row */}
-            {codeMode === "browse"   && <CodeContent projectId={projectId} appName={activeApp} rootPath={activeRoot} />}
+            <div style={{ flex: 1, display: "flex", overflow: "hidden" }}>
-            {codeMode === "agent"    && <AgentMode projectId={projectId} appName={activeApp} appPath={activeRoot} />}
+              {/* Left: Browse */}
-            {codeMode === "terminal" && <TerminalMode appName={activeApp} />}
+              <div style={{ flex: 1, display: "flex", flexDirection: "column", overflow: "hidden", borderRight: "1px solid #e8e4dc", minWidth: 0 }}>
+                {/* Browse header */}
+                <div style={{ height: 32, flexShrink: 0, display: "flex", alignItems: "center", padding: "0 14px", borderBottom: "1px solid #e8e4dc", background: "#fff" }}>
+                  <span style={{ fontSize: "0.68rem", fontWeight: 700, color: "#a09a90", letterSpacing: "0.07em", textTransform: "uppercase", fontFamily: "Outfit, sans-serif" }}>Browse</span>
+                  {activeApp && <span style={{ marginLeft: 8, fontSize: "0.7rem", color: "#b5b0a6", fontFamily: "IBM Plex Mono, monospace" }}>{activeApp}</span>}
+                </div>
+                <CodeContent projectId={projectId} appName={activeApp} rootPath={activeRoot} />
+              </div>
+
+              {/* Right: Agent */}
+              <div style={{ width: 420, flexShrink: 0, display: "flex", flexDirection: "column", overflow: "hidden", background: "#fff" }}>
+                {/* Agent header */}
+                <div style={{ height: 32, flexShrink: 0, display: "flex", alignItems: "center", padding: "0 14px", borderBottom: "1px solid #e8e4dc" }}>
+                  <span style={{ fontSize: "0.68rem", fontWeight: 700, color: "#a09a90", letterSpacing: "0.07em", textTransform: "uppercase", fontFamily: "Outfit, sans-serif" }}>Agent</span>
+                  {activeApp && <span style={{ marginLeft: 8, fontSize: "0.7rem", color: "#b5b0a6", fontFamily: "IBM Plex Mono, monospace" }}>{activeApp}</span>}
+                </div>
+                <AgentMode projectId={projectId} appName={activeApp} appPath={activeRoot} />
+              </div>
+            </div>
+
+            {/* Bottom: Terminal (collapsible) */}
+            <TerminalPanel appName={activeApp} />
           </div>
         )}
+
         {section === "layouts" && (
           <LayoutsContent surfaces={surfaces} projectId={projectId} workspace={workspace} activeSurfaceId={activeSurfaceId} onSelectSurface={id => { setActiveSurfaceId(id); navigate({ section: "layouts", surface: id }); }} />
         )}