fix(mcp): keep normal browser windows chromed (#62)

Co-authored-by: Codex <codex@openai.com>

Author: AbdulRashidReshamwala

images/minimal-vnc-desktop/README.md

@@ -390,6 +390,7 @@ commands the probes need):
 | `APP_COMMAND` | `/usr/local/bin/run-chromium-managed` | GUI launcher. Warm pods start in kiosk mode and, after allocation, honor the GameServer's `popcorn.dev/browser-mode` annotation for that pod only. |
 | `BROWSER_KIOSK` | `true` | Passed to `start-chromium`; set to `false` by the managed launcher only for an allocated normal-view pod. |
 | `BROWSER_PROFILE_DIR` | `$HOME/user-data` | Chromium profile directory. The managed launcher uses `$HOME/user-data-normal` for a normal-view restart so kiosk fullscreen state cannot carry over. |
+| `BROWSER_MODE_FILE` | `/tmp/popcorn-browser-mode` | Shared kiosk/normal marker used by the CDP proxy; missing or invalid values default to kiosk. |
 | `APP_URL` | depends on `REPLACE_DEFAULT_PAGE` | Default startup URL for `start-chromium`. When unset, falls back to DuckDuckGo (`REPLACE_DEFAULT_PAGE=false`, default) or the Reclaim loading page (`REPLACE_DEFAULT_PAGE=true`). Set explicitly to override both. |
 | `POPCORN_BROWSER_STARTUP_URL` | empty | Compatibility alias used when `APP_URL` is unset. |
 | `CHROMIUM_STARTUP_URL` | empty | Compatibility alias used when `APP_URL` and `POPCORN_BROWSER_STARTUP_URL` are unset. |

images/minimal-vnc-desktop/extensions/proxy/background.js

@@ -1,6 +1,11 @@
 // Popcorn Proxy Extension - Background Service Worker (MV3)
 // Sets proxy only - auth handled via CDP Fetch
 
+// Generated by start-chromium for this pod. The checked-in default is kiosk so
+// an older/custom launcher preserves the locked-down viewer behavior.
+try { importScripts('browser-mode.js'); } catch (_) {}
+const manageFullscreen = globalThis.POPCORN_BROWSER_KIOSK !== false;
+
 // ---- keep every browser window chromeless -----------------------------------
 // The stream must never show Chromium's tab strip / omnibox. --kiosk boots the
 // FIRST window chromeless, but that is all it guarantees: measured on this build,
@@ -28,7 +33,7 @@ function forceFullscreen(win) {
 function fullscreenAll() {
   try { chrome.windows.getAll().then((ws) => ws.forEach(forceFullscreen)).catch(() => {}); } catch (_) {}
 }
-try {
+if (manageFullscreen) try {
   chrome.windows.onCreated.addListener(forceFullscreen);
   // A window flipped to 'normal' after creation still needs correcting; focus
   // changes are the cheap, event-driven moment to re-check without polling.

images/minimal-vnc-desktop/extensions/proxy/browser-mode.js

@@ -0,0 +1,2 @@
+// Safe default. start-chromium rewrites this file to false for normal MCP pods.
+globalThis.POPCORN_BROWSER_KIOSK = true;

images/minimal-vnc-desktop/proxy/emulate.go

@@ -1216,17 +1216,16 @@ func (e *emulator) session() error {
 	defer e.resetSessions()
 	defer e.resetDialogs()
 
-	// Kiosk fullscreen watchdog. Chrome's tab strip shows ONLY when a window is in
+	// Window-state watchdog. Chrome's tab strip shows ONLY when a window is in
 	// windowState 'normal' (measured: 'fullscreen' and 'maximized' are chromeless,
 	// 'normal' shows a 35px toolbar even under --kiosk). Our proxy never sets
 	// 'normal' — but Chromium can put a window there on its own (a window.open popup
 	// with size features opens normal+chromed), and the extension's onCreated fast
 	// path can miss a window that flips AFTER creation, since a single-window kiosk
 	// fires no focus-change to re-check on. This connection is always alive, so it is
 	// the reliable place to re-assert: each tick we ask for every tracked page's
-	// window, and the getWindowForTarget reply handler above forces it fullscreen.
-	// Idempotent on an already-fullscreen window (a no-op setWindowBounds), so the
-	// cost is one round-trip per page per tick.
+	// window, and the reply handler below applies the pod's current browser mode.
+	// The mode file is written by start-chromium and defaults to kiosk when absent.
 	watchdog := time.NewTicker(2 * time.Second)
 	defer watchdog.Stop()
 
@@ -1574,25 +1573,23 @@ func (e *emulator) session() error {
 			// Command responses (have an id).
 			if _, hasID := m["id"]; hasID {
 				if result, ok := m["result"].(map[string]any); ok {
-					// Browser.getWindowForTarget reply → fullscreen that window
-					// (browser-level, no session). This is how popups lose their
-					// location bar and fill the screen.
+					// Browser.getWindowForTarget reply → apply the requested pod
+					// mode (browser-level, no session). Kiosk popups lose their location
+					// bar; normal MCP windows explicitly retain browser chrome.
 					//
-					// FULLSCREEN IS THE ONLY STATE WE MAY EVER SET. Chromium's --kiosk
-					// suppresses the tab strip and omnibox only while the window is
-					// fullscreen: a window put into `normal` state draws its full chrome
-					// inside the same geometry, so the user gets a real URL bar in a
-					// session that is supposed to be a locked-down viewer. An earlier
-					// version of this handler resized the window with explicit normal
-					// bounds to cover a taller framebuffer, and that is exactly what it
-					// leaked — measured 796px of browser UI inside the window. Do not
-					// reintroduce a normal-state resize here; if a window must chase the
-					// screen, the sanctioned path is the X-level fit in window.go
-					// (requestWindowFit below), never un-fullscreening the kiosk.
+					// Kiosk mode may only set fullscreen: a normal-state resize would
+					// leak the tab strip and omnibox into a locked-down viewer. Normal
+					// MCP mode intentionally does the inverse and sets `normal` so those
+					// controls remain visible. Geometry in either mode is handled by the
+					// X-level fit in window.go (requestWindowFit below).
 					if wid, ok := result["windowId"]; ok {
+						desiredState := "fullscreen"
+						if !browserKioskMode() {
+							desiredState = "normal"
+						}
 						send("Browser.setWindowBounds", map[string]any{
 							"windowId": wid,
-							"bounds":   map[string]any{"windowState": "fullscreen"},
+							"bounds":   map[string]any{"windowState": desiredState},
 						}, "")
 						// A window seen OUTSIDE fullscreen is a real transition (a popup just
 						// opened normal+chromed), and the size openbox grants it may reflect a
@@ -1601,7 +1598,7 @@ func (e *emulator) session() error {
 						// watchdog tick for already-fullscreen windows, and spawning xdotool
 						// that often costs fd budget under Rosetta (see window.go).
 						if b, _ := result["bounds"].(map[string]any); b != nil {
-							if state, _ := b["windowState"].(string); state != "fullscreen" {
+							if state, _ := b["windowState"].(string); state != desiredState {
 								requestWindowFit(log.Printf)
 							}
 						}

images/minimal-vnc-desktop/proxy/main.go

@@ -31,6 +31,15 @@ const websocketGUID = "258EAFA5-E914-47DA-95CA-C5AB0DC85B11"
 
 var websocketBridgeSequence atomic.Uint64
 
+func browserKioskMode() bool {
+	modeFile := envDefault("BROWSER_MODE_FILE", "/tmp/popcorn-browser-mode")
+	mode, err := os.ReadFile(modeFile)
+	if err != nil {
+		return true
+	}
+	return strings.TrimSpace(string(mode)) != "normal"
+}
+
 func main() {
 	listen := flag.String("listen", envDefault("NOVNC_LISTEN", ":6080"), "HTTP listen address")
 	vnc := flag.String("vnc", envDefault("VNC_ADDR", "127.0.0.1:5900"), "upstream VNC address")

images/minimal-vnc-desktop/proxy/main_test.go

@@ -18,6 +18,27 @@ import (
 	"github.com/flynn/noise"
 )
 
+func TestBrowserKioskMode(t *testing.T) {
+	modeFile := filepath.Join(t.TempDir(), "browser-mode")
+	t.Setenv("BROWSER_MODE_FILE", modeFile)
+
+	if !browserKioskMode() {
+		t.Fatal("missing mode file must default to kiosk")
+	}
+	if err := os.WriteFile(modeFile, []byte("normal\n"), 0o600); err != nil {
+		t.Fatal(err)
+	}
+	if browserKioskMode() {
+		t.Fatal("normal mode file must disable kiosk fullscreen management")
+	}
+	if err := os.WriteFile(modeFile, []byte("kiosk\n"), 0o600); err != nil {
+		t.Fatal(err)
+	}
+	if !browserKioskMode() {
+		t.Fatal("kiosk mode file must enable kiosk fullscreen management")
+	}
+}
+
 func TestCDPReadyGate(t *testing.T) {
 	upstream := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
 		if r.URL.Path != "/json/version" {

images/minimal-vnc-desktop/start-chromium

@@ -23,13 +23,27 @@ CDP_INTERNAL_PORT="${CDP_INTERNAL_PORT:-${CHROME_REMOTE_DEBUGGING_PORT:-9223}}"
 CHROME_REMOTE_DEBUGGING_ADDRESS="${CHROME_REMOTE_DEBUGGING_ADDRESS:-127.0.0.1}"
 PROXY_EXTENSION_DIR="${PROXY_EXTENSION_DIR:-/home/kernel/extensions/proxy}"
 ENABLE_PROXY_EXTENSION="${ENABLE_PROXY_EXTENSION:-true}"
+BROWSER_KIOSK="${BROWSER_KIOSK:-true}"
+BROWSER_MODE_FILE="${BROWSER_MODE_FILE:-/tmp/popcorn-browser-mode}"
 CHROMIUM_POLICY_DIR="${CHROMIUM_POLICY_DIR:-/etc/chromium/policies/managed}"
 CHROMIUM_POLICY_VARIANT_DIR="${CHROMIUM_POLICY_VARIANT_DIR:-/etc/chromium/policy-variants}"
 
 BROWSER_PROFILE_DIR="${BROWSER_PROFILE_DIR:-$HOME/user-data}"
 mkdir -p "$BROWSER_PROFILE_DIR"
 rm -f "$BROWSER_PROFILE_DIR/SingletonLock" "$BROWSER_PROFILE_DIR/SingletonSocket" "$BROWSER_PROFILE_DIR/SingletonCookie"
 
+# The noVNC/CDP proxy starts before allocation, so publish the selected mode in
+# a tiny shared file it can re-read while the managed launcher switches this pod.
+# Missing/invalid files fail closed to kiosk in the proxy.
+if [[ "$BROWSER_KIOSK" == "true" ]]; then
+  BROWSER_MODE=kiosk
+  BROWSER_KIOSK_JS=true
+else
+  BROWSER_MODE=normal
+  BROWSER_KIOSK_JS=false
+fi
+printf '%s\n' "$BROWSER_MODE" >"$BROWSER_MODE_FILE"
+
 if [[ "$REPLACE_DEFAULT_PAGE" == "true" ]]; then
   reclaim_policy="${CHROMIUM_POLICY_VARIANT_DIR}/policy.reclaim-portal.json"
   managed_policy="${CHROMIUM_POLICY_DIR}/policy.json"
@@ -439,11 +453,15 @@ flags=(
   "${cloak_flags[@]}"
 )
 
-if [[ "${BROWSER_KIOSK:-true}" == "true" ]]; then
+if [[ "$BROWSER_KIOSK" == "true" ]]; then
   flags+=("--kiosk")
 fi
 
 if [[ "$ENABLE_PROXY_EXTENSION" == "true" && -f "${PROXY_EXTENSION_DIR}/manifest.json" ]]; then
+  # The extension normally keeps kiosk popups chromeless. Give each isolated
+  # pod's unpacked extension the same mode so normal MCP windows retain chrome.
+  printf 'globalThis.POPCORN_BROWSER_KIOSK = %s;\n' "$BROWSER_KIOSK_JS" \
+    >"${PROXY_EXTENSION_DIR}/browser-mode.js"
   flags+=(
     "--disable-extensions-except=${PROXY_EXTENSION_DIR}"
     "--load-extension=${PROXY_EXTENSION_DIR}"