diff --git a/tbselenium/tbbinary.py b/tbselenium/tbbinary.py
index 8f98822..0d4890c 100644
--- a/tbselenium/tbbinary.py
+++ b/tbselenium/tbbinary.py
@@ -1,16 +1,86 @@
-from selenium.webdriver.firefox.firefox_binary import FirefoxBinary
+"""
+TBBinary — lightweight wrapper around the Tor Browser (Firefox) process.
 
+In Selenium < 4.40 this module subclassed ``FirefoxBinary``.  That class was
+deprecated in Selenium 4.x and fully removed in 4.40.0 (see
+https://github.com/SeleniumHQ/selenium/blob/trunk/py/CHANGES).
 
-class TBBinary(FirefoxBinary):
-    '''
-    Extend FirefoxBinary to better handle terminated browser processes.
-    '''
+The modern Selenium API no longer requires a ``FirefoxBinary`` object:
+``Options.binary`` accepts a plain filesystem path (str / ``pathlib.Path``),
+and the ``Service`` object owns the geckodriver life-cycle.  ``TBBinary`` is
+therefore re-implemented as a standalone helper that only manages the *browser*
+process itself — primarily to provide the ``kill()`` method that some callers
+rely on when the browser becomes unresponsive.
+"""
 
-    def kill(self):
-        """Kill the browser.
+from __future__ import annotations
 
-        This is useful when the browser is stuck.
+import subprocess
+from typing import IO, Optional
+
+
+class TBBinary:
+    """Manage the Tor Browser (Firefox) process independently of Selenium.
+
+    This class replaces the former ``FirefoxBinary``-based implementation and
+    is compatible with Selenium >= 4.40.0.
+
+    Parameters
+    ----------
+    firefox_path:
+        Absolute path to the ``firefox`` binary inside the Tor Browser bundle.
+    log_file:
+        Optional writable file-like object that receives the browser's stdout
+        and stderr output.  Pass ``None`` (the default) to discard output.
+    """
+
+    def __init__(
+        self,
+        firefox_path: str,
+        log_file: Optional[IO[str]] = None,
+    ) -> None:
+        self.firefox_path = firefox_path
+        self.log_file = log_file
+        self.process: Optional[subprocess.Popen] = None  # type: ignore[type-arg]
+
+    # ------------------------------------------------------------------
+    # Process control
+    # ------------------------------------------------------------------
+
+    def launch_browser(self, profile: str, timeout: int = 30) -> None:
+        """Start the Tor Browser process with a given Firefox profile.
+
+        Parameters
+        ----------
+        profile:
+            Path to the Firefox profile directory that should be used.
+        timeout:
+            Unused; kept for API compatibility with callers that previously
+            passed a timeout to the legacy ``FirefoxBinary.launch_browser()``.
+        """
+        sink = self.log_file or subprocess.DEVNULL
+        self.process = subprocess.Popen(
+            [self.firefox_path, "--profile", profile],
+            stdout=sink,
+            stderr=sink,
+        )
+
+    def kill(self) -> None:
+        """Forcefully terminate the browser process.
+
+        Safe to call even if the process has already exited or was never
+        started — in those cases the method is a no-op.
         """
-        if self.process and self.process.poll() is None:
+        if self.process is not None and self.process.poll() is None:
             self.process.kill()
             self.process.wait()
+
+    # ------------------------------------------------------------------
+    # Context-manager support
+    # ------------------------------------------------------------------
+
+    def __enter__(self) -> "TBBinary":
+        return self
+
+    def __exit__(self, *args: object) -> None:
+        self.kill()
diff --git a/tbselenium/tbdriver.py b/tbselenium/tbdriver.py
index 0b33979..ccde75f 100644
--- a/tbselenium/tbdriver.py
+++ b/tbselenium/tbdriver.py
@@ -90,10 +90,9 @@ def __init__(self,
                 log_path=tbb_logfile_path,
                 port=geckodriver_port
                 )
-        # options.binary is path to the Firefox binary and it can be a string
-        # or a FirefoxBinary object. If it's a string, it will be converted to
-        # a FirefoxBinary object.
-        # https://github.com/SeleniumHQ/selenium/blob/7cfd137085fcde932cd71af78642a15fd56fe1f1/py/selenium/webdriver/firefox/options.py#L54
+        # options.binary accepts a filesystem path (str) to the Firefox binary.
+        # FirefoxBinary was removed in Selenium 4.40.0; a plain string path is
+        # the correct way to configure the binary in modern Selenium.
         self.options.binary = self.tbb_fx_binary_path
         self.options.add_argument('--class')
         self.options.add_argument('"Tor Browser"')
@@ -309,7 +308,12 @@ def export_env_vars(self):
         prepend_to_env_var("PATH", self.tbb_browser_dir)
 
     def get_tb_binary(self, logfile=None):
-        """Return FirefoxBinary pointing to the TBB's firefox binary."""
+        """Return a TBBinary instance pointing to the Tor Browser's Firefox binary.
+
+        Note: this method is not called during normal driver initialisation.
+        It is provided as a convenience for callers that need to manage the
+        browser process directly (e.g. to forcefully kill a stuck browser).
+        """
         tbb_logfile = open(logfile, 'a+') if logfile else None
         return TBBinary(firefox_path=self.tbb_fx_binary_path,
                         log_file=tbb_logfile)