feat(browser): reuse system Chrome/Edge, bundle playwright for desktop

agent/tools/browser/browser_env.py

@@ -0,0 +1,290 @@
+"""
+Browser environment detection and capability resolution.
+
+Centralizes everything about *where* a usable browser engine comes from, so
+both the runtime (browser_service) and the installer (cli/commands/install)
+agree on the same decisions:
+
+  - Whether the `playwright` Python package is importable.
+  - Whether a system Chrome / Edge is installed (Playwright can drive it via
+    the `channel="chrome"/"msedge"` launcher, no download needed).
+  - Where Playwright's own Chromium download lives (redirected to the writable
+    data dir so it survives frozen/desktop app updates).
+
+Resolution priority (see resolve_engine):
+  1. system-chrome  -> drive the user's installed Chrome / Edge (zero download)
+  2. playwright-chromium -> Playwright's own Chromium, if already downloaded
+  3. none -> nothing usable yet; caller should trigger onboarding
+"""
+
+import os
+import sys
+import shutil
+from typing import Optional, Dict, Any
+
+from common.log import logger
+
+
+# Playwright browser channels we accept for the "system-chrome" mode, in
+# preference order. "chrome" covers stable Google Chrome; "msedge" is the
+# Chromium-based Edge shipped on every Windows 10/11.
+_PREFERRED_CHANNELS = ("chrome", "msedge", "chrome-beta", "msedge-beta")
+
+
+def get_data_root() -> str:
+    """Writable data root (~/.cow on desktop, else CWD-based).
+
+    Mirrors the logic in common/log.py without importing config, to avoid a
+    circular import. The desktop build sets COW_DATA_DIR; source deployments
+    fall back to the current working directory.
+    """
+    data_dir = os.environ.get("COW_DATA_DIR")
+    if data_dir:
+        return os.path.expanduser(data_dir)
+    return os.getcwd()
+
+
+def browsers_download_dir() -> str:
+    """Directory Playwright downloads its Chromium into.
+
+    We pin it under the writable data root (~/.cow/ms-playwright) rather than
+    Playwright's default (~/.cache/ms-playwright or %USERPROFILE%). This keeps
+    the frozen desktop build self-contained and makes the download survive app
+    updates. Set as PLAYWRIGHT_BROWSERS_PATH for both install and runtime.
+    """
+    return os.path.join(get_data_root(), "ms-playwright")
+
+
+def apply_browsers_path_env() -> None:
+    """Point Playwright at our pinned download dir via env var (idempotent).
+
+    Only set it when not already provided by the user, so power users can
+    override the location. Must run before importing playwright's launcher.
+    """
+    if not os.environ.get("PLAYWRIGHT_BROWSERS_PATH"):
+        os.environ["PLAYWRIGHT_BROWSERS_PATH"] = browsers_download_dir()
+
+
+def is_frozen() -> bool:
+    """True when running inside a PyInstaller-frozen bundle (desktop backend).
+
+    In this mode sys.executable is the frozen exe (no pip), so the installer
+    must skip `pip install` and only download the browser binary.
+    """
+    return bool(getattr(sys, "frozen", False))
+
+
+def is_desktop() -> bool:
+    """True when running as the Electron desktop client (dev or packaged).
+
+    The desktop shell always sets COW_DESKTOP=1 (see python-manager.ts), both in
+    `npm run dev` (runs app.py with the user's Python) and in the packaged build
+    (frozen exe). Desktop users have no `cow` CLI, so onboarding must point them
+    at the in-chat `/install-browser` command rather than a terminal command.
+    """
+    return os.environ.get("COW_DESKTOP") == "1"
+
+
+def has_playwright_package() -> bool:
+    """True if the `playwright` Python package can be imported."""
+    try:
+        import playwright  # noqa: F401
+        return True
+    except Exception:
+        return False
+
+
+def _windows_program_dirs() -> list:
+    dirs = []
+    for var in ("PROGRAMFILES", "PROGRAMFILES(X86)", "LOCALAPPDATA"):
+        val = os.environ.get(var)
+        if val:
+            dirs.append(val)
+    return dirs
+
+
+def detect_system_chrome() -> Optional[Dict[str, str]]:
+    """Locate an installed Chromium-based browser Playwright can drive.
+
+    Returns a dict {"channel": <playwright channel>, "path": <exe path>} for
+    the first match, or None. The `channel` is what we hand to Playwright's
+    launcher; `path` is only informational (Playwright resolves the channel on
+    its own, but we keep the path for logging / onboarding messages).
+    """
+    candidates = []
+
+    if sys.platform == "darwin":
+        candidates = [
+            ("chrome", "/Applications/Google Chrome.app/Contents/MacOS/Google Chrome"),
+            ("msedge", "/Applications/Microsoft Edge.app/Contents/MacOS/Microsoft Edge"),
+            ("chrome-beta", "/Applications/Google Chrome Beta.app/Contents/MacOS/Google Chrome Beta"),
+        ]
+    elif sys.platform == "win32":
+        prog_dirs = _windows_program_dirs()
+        for base in prog_dirs:
+            candidates.append(("chrome", os.path.join(base, "Google", "Chrome", "Application", "chrome.exe")))
+            candidates.append(("msedge", os.path.join(base, "Microsoft", "Edge", "Application", "msedge.exe")))
+    else:
+        # Linux: rely on PATH lookups for the common binaries.
+        path_lookups = [
+            ("chrome", "google-chrome"),
+            ("chrome", "google-chrome-stable"),
+            ("chrome", "chromium"),
+            ("chrome", "chromium-browser"),
+            ("msedge", "microsoft-edge"),
+        ]
+        for channel, binary in path_lookups:
+            found = shutil.which(binary)
+            if found:
+                return {"channel": channel, "path": found}
+
+    for channel, path in candidates:
+        if path and os.path.exists(path):
+            return {"channel": channel, "path": path}
+
+    return None
+
+
+def has_downloaded_chromium() -> bool:
+    """True if Playwright already has a Chromium download available.
+
+    We check our pinned download dir for a chromium-* folder. This is a
+    lightweight heuristic (avoids importing/launching Playwright just to probe)
+    and matches how Playwright lays browsers out on disk.
+    """
+    download_dir = browsers_download_dir()
+    if not os.path.isdir(download_dir):
+        return False
+    try:
+        for name in os.listdir(download_dir):
+            # Playwright names its browser dirs like "chromium-1140",
+            # "chromium_headless_shell-1140".
+            if name.startswith("chromium"):
+                return True
+    except OSError:
+        pass
+    return False
+
+
+def resolve_engine(config: Optional[Dict[str, Any]] = None) -> Dict[str, Any]:
+    """Decide which browser engine to use, given config and environment.
+
+    Returns a dict describing the launch strategy:
+        {
+            "mode": "system-chrome" | "playwright-chromium" | "none",
+            "channel": Optional[str],   # for system-chrome
+            "path": Optional[str],      # for system-chrome (informational)
+            "has_playwright": bool,
+            "reason": str,              # human-readable, for logging / onboarding
+        }
+
+    Config keys under tools.browser that influence this:
+      - engine: "auto" (default) | "system-chrome" | "chromium"
+          Force a specific engine. "auto" prefers system Chrome, then falls
+          back to a downloaded Chromium.
+      - prefer_system_browser: bool (default True). When False under "auto",
+          skip system Chrome and go straight to Playwright's Chromium.
+    """
+    config = config or {}
+    apply_browsers_path_env()
+
+    has_pw = has_playwright_package()
+    engine_pref = str(config.get("engine", "auto")).strip().lower()
+    prefer_system = config.get("prefer_system_browser", True)
+
+    if not has_pw:
+        return {
+            "mode": "none",
+            "channel": None,
+            "path": None,
+            "has_playwright": False,
+            "reason": "playwright package not available",
+        }
+
+    system = None
+    if engine_pref in ("auto", "system-chrome") and prefer_system:
+        system = detect_system_chrome()
+
+    if engine_pref == "system-chrome":
+        # Explicitly requested: use system Chrome if found, else report none.
+        if system:
+            return {
+                "mode": "system-chrome",
+                "channel": system["channel"],
+                "path": system["path"],
+                "has_playwright": True,
+                "reason": f"using system browser ({system['channel']})",
+            }
+        return {
+            "mode": "none",
+            "channel": None,
+            "path": None,
+            "has_playwright": True,
+            "reason": "engine=system-chrome but no Chrome/Edge found",
+        }
+
+    if engine_pref == "chromium":
+        # Explicitly requested Playwright's own Chromium.
+        if has_downloaded_chromium():
+            return {
+                "mode": "playwright-chromium",
+                "channel": None,
+                "path": None,
+                "has_playwright": True,
+                "reason": "using downloaded Playwright Chromium",
+            }
+        return {
+            "mode": "none",
+            "channel": None,
+            "path": None,
+            "has_playwright": True,
+            "reason": "engine=chromium but Chromium not downloaded yet",
+        }
+
+    # auto: system Chrome first, then downloaded Chromium.
+    if system:
+        return {
+            "mode": "system-chrome",
+            "channel": system["channel"],
+            "path": system["path"],
+            "has_playwright": True,
+            "reason": f"auto: using system browser ({system['channel']})",
+        }
+    if has_downloaded_chromium():
+        return {
+            "mode": "playwright-chromium",
+            "channel": None,
+            "path": None,
+            "has_playwright": True,
+            "reason": "auto: using downloaded Playwright Chromium",
+        }
+
+    return {
+        "mode": "none",
+        "channel": None,
+        "path": None,
+        "has_playwright": True,
+        "reason": "no system Chrome/Edge and no downloaded Chromium",
+    }
+
+
+def capability_summary(config: Optional[Dict[str, Any]] = None) -> Dict[str, Any]:
+    """High-level browser capability status, for onboarding / diagnostics.
+
+    Combines resolve_engine with raw detection flags so the UI / tool layer can
+    craft a helpful message (e.g. "Chrome detected, click to enable" vs
+    "no browser, will download ~150MB").
+    """
+    engine = resolve_engine(config)
+    system = detect_system_chrome()
+    return {
+        "ready": engine["mode"] != "none",
+        "engine": engine,
+        "has_playwright": engine["has_playwright"],
+        "has_system_chrome": system is not None,
+        "system_chrome": system,
+        "has_downloaded_chromium": has_downloaded_chromium(),
+        "is_frozen": is_frozen(),
+        "is_desktop": is_desktop(),
+        "browsers_dir": browsers_download_dir(),
+    }

agent/tools/browser/browser_service.py

@@ -326,12 +326,19 @@ class BrowserService:
         # - persistent: launch with launch_persistent_context using a user_data_dir
         #   so cookies / login state survive across runs (default).
         # - fresh: classic launch + new_context, clean state every run.
+        #
+        # Within persistent/fresh, the actual Chromium binary is resolved by
+        # browser_env.resolve_engine(): a system Chrome/Edge (channel-based, zero
+        # download) is preferred, falling back to Playwright's own downloaded
+        # Chromium. `self._channel` is the Playwright channel ("chrome"/"msedge")
+        # when driving a system browser, else None (bundled Chromium).
         cdp_endpoint = self._config.get("cdp_endpoint") or ""
         persistent_flag = self._config.get("persistent", True)
         user_data_dir_cfg = self._config.get("user_data_dir")
         if user_data_dir_cfg is None:
             user_data_dir_cfg = _DEFAULT_USER_DATA_DIR
 
+        self._channel: Optional[str] = None
         self._cdp_endpoint: str = cdp_endpoint.strip() if isinstance(cdp_endpoint, str) else ""
         if self._cdp_endpoint:
             self._launch_mode = "cdp"
@@ -343,6 +350,22 @@ class BrowserService:
             self._launch_mode = "fresh"
             self._user_data_dir = ""
 
+        # Resolve which browser engine to drive (system Chrome vs downloaded
+        # Chromium). Deferred detection failures are surfaced at launch time.
+        if self._launch_mode != "cdp":
+            try:
+                from agent.tools.browser.browser_env import resolve_engine
+                engine = resolve_engine(self._config)
+                if engine["mode"] == "system-chrome":
+                    self._channel = engine["channel"]
+                    logger.info(f"[Browser] Engine resolved: {engine['reason']}")
+                elif engine["mode"] == "playwright-chromium":
+                    logger.info(f"[Browser] Engine resolved: {engine['reason']}")
+                else:
+                    logger.info(f"[Browser] No ready engine yet: {engine['reason']}")
+            except Exception as e:
+                logger.debug(f"[Browser] Engine resolution skipped: {e}")
+
         # Idle auto-release
         idle_cfg = self._config.get("idle_timeout")
         self._idle_timeout: float = float(idle_cfg) if idle_cfg is not None else self._IDLE_TIMEOUT_DEFAULT
@@ -428,6 +451,14 @@ class BrowserService:
 
     def _launch_browser(self):
         """Launch / connect Chromium on the background thread."""
+        # Point Playwright at our pinned download dir before any launch so a
+        # bundled-Chromium fallback finds the browser downloaded to ~/.cow.
+        try:
+            from agent.tools.browser.browser_env import apply_browsers_path_env
+            apply_browsers_path_env()
+        except Exception as e:
+            logger.debug(f"[Browser] apply_browsers_path_env skipped: {e}")
+
         if self._headless is None:
             headless_cfg = self._config.get("headless")
             self._headless = headless_cfg if headless_cfg is not None else _should_use_headless()
@@ -475,12 +506,20 @@ class BrowserService:
         logger.info("[Browser] Browser ready")
 
     def _launch_fresh(self, launch_args: List[str], viewport: Dict[str, int], user_agent: str):
-        """Classic launch: brand new Chromium with an empty context."""
-        logger.info(f"[Browser] Launching Chromium (fresh, headless={self._headless})")
-        self._browser = self._playwright.chromium.launch(
-            headless=self._headless,
-            args=launch_args,
-        )
+        """Classic launch: brand new Chromium with an empty context.
+
+        When `self._channel` is set (e.g. "chrome"/"msedge"), Playwright drives
+        the user's installed system browser instead of its own Chromium.
+        """
+        engine_label = f"system:{self._channel}" if self._channel else "chromium"
+        logger.info(f"[Browser] Launching {engine_label} (fresh, headless={self._headless})")
+        launch_kwargs: Dict[str, Any] = {
+            "headless": self._headless,
+            "args": launch_args,
+        }
+        if self._channel:
+            launch_kwargs["channel"] = self._channel
+        self._browser = self._playwright.chromium.launch(**launch_kwargs)
         self._context = self._browser.new_context(
             viewport=viewport,
             user_agent=user_agent,
@@ -491,18 +530,25 @@ class BrowserService:
     def _launch_persistent(self, launch_args: List[str], viewport: Dict[str, int], user_agent: str):
         """Launch Chromium with a persistent user_data_dir so login state survives."""
         os.makedirs(self._user_data_dir, exist_ok=True)
+        engine_label = f"system:{self._channel}" if self._channel else "chromium"
         logger.info(
-            f"[Browser] Launching Chromium (persistent, headless={self._headless}, "
+            f"[Browser] Launching {engine_label} (persistent, headless={self._headless}, "
             f"profile={self._user_data_dir})"
         )
+        persistent_kwargs: Dict[str, Any] = {
+            "user_data_dir": self._user_data_dir,
+            "headless": self._headless,
+            "args": launch_args,
+            "viewport": viewport,
+            "user_agent": user_agent,
+        }
+        # When driving a system browser, let it use its real UA instead of the
+        # spoofed Chromium one (avoids UA/engine mismatch on real Chrome/Edge).
+        if self._channel:
+            persistent_kwargs["channel"] = self._channel
+            persistent_kwargs.pop("user_agent", None)
         try:
-            self._context = self._playwright.chromium.launch_persistent_context(
-                user_data_dir=self._user_data_dir,
-                headless=self._headless,
-                args=launch_args,
-                viewport=viewport,
-                user_agent=user_agent,
-            )
+            self._context = self._playwright.chromium.launch_persistent_context(**persistent_kwargs)
         except Exception as e:
             # Profile is locked when another Chromium instance already holds it.
             msg = str(e).lower()

agent/tools/browser/browser_tool.py

@@ -185,6 +185,40 @@ class BrowserTool(BaseTool):
                     f"({ip_str}), request blocked for security"
                 )
 
+    def _check_engine_ready(self) -> Optional[ToolResult]:
+        """Return an actionable onboarding message if no browser engine is ready.
+
+        Returns None when a system Chrome/Edge or a downloaded Chromium is
+        available (so the tool can proceed). Otherwise returns a ToolResult with
+        clear guidance so the agent asks the user to enable the browser instead
+        of surfacing a raw Playwright launch error. CDP mode is exempt (the
+        endpoint is external and validated at connect time).
+        """
+        if self.config.get("cdp_endpoint"):
+            return None
+        try:
+            from agent.tools.browser.browser_env import capability_summary
+            summary = capability_summary(self.config)
+        except Exception as e:
+            logger.debug(f"[Browser] capability probe failed: {e}")
+            return None
+
+        if summary.get("ready"):
+            return None
+
+        # Desktop clients (dev or packaged) have no `cow` CLI — onboard via the
+        # in-chat `/install-browser` command. Source / web / server installs use
+        # the `cow install-browser` terminal command.
+        install_hint = (
+            "reply `/install-browser`" if summary.get("is_desktop")
+            else "run `cow install-browser` in a terminal"
+        )
+        return ToolResult.fail(
+            f"Browser tool not ready. Ask the user to {install_hint} (installs a browser engine; "
+            "skipped automatically if Google Chrome is already installed). "
+            "Do not retry until the user confirms."
+        )
+
     def execute(self, args: Dict[str, Any]) -> ToolResult:
         action = args.get("action", "").strip().lower()
         if not action:
@@ -195,6 +229,13 @@ class BrowserTool(BaseTool):
             valid = ", ".join(sorted(self._ACTION_MAP.keys()))
             return ToolResult.fail(f"Unknown action '{action}'. Valid actions: {valid}")
 
+        # Preflight: on desktop the playwright package is bundled but the browser
+        # binary may be missing; return actionable onboarding instead of a cryptic
+        # launch failure.
+        not_ready = self._check_engine_ready()
+        if not_ready is not None:
+            return not_ready
+
         try:
             return handler(self, args)
         except Exception as e: