Bound extension job and window-alias state

Two service-worker leaks. Running jobs were only bounded by their watchdog, so
a command flood could hold many timers and results for up to JOB_TIMEOUT_MS;
cap concurrent jobs at 32 and reject beyond that, since a clear error beats an
unresponsive worker. Window aliases were never removed, so storage kept an
entry for every window the user had ever renamed.

Prune aliases against the live window set on list, rename, and close rather
than only on close, because windows also disappear without going through
windows.close.

Also extract the repeated job summary in perf.status into a helper.

README.md

@@ -70,6 +70,11 @@ For better remote-response compression, install the optional `fast` extra:
 uv tool install "real-browser-cli[fast]"
 ```
 
+To expose the conservative MCP tool surface, install the optional `mcp` extra:
+```sh
+uv tool install "real-browser-cli[mcp]"
+```
+
 To upgrade later:
 
 ```sh
@@ -141,6 +146,89 @@ browser-cli/
 
 ---
 
+## Stateless MCP server
+The optional MCP adapter exposes a small, typed subset of the Python SDK for
+MCP hosts such as Claude Desktop, Claude Code, Cursor, or VS Code. It controls
+the same real browser; it does not launch a headless browser or duplicate the
+browser command implementation.
+
+Install and run the local stdio server:
+```sh
+uv tool install "real-browser-cli[mcp]"
+browser-cli-mcp
+```
+
+Example MCP host configuration:
+```json
+{
+  "mcpServers": {
+    "browser-cli": {
+      "command": "browser-cli-mcp"
+    }
+  }
+}
+```
+
+The server is stateless at the MCP layer. Every tool call creates a fresh
+`BrowserCLI` SDK client, and browser state remains in the real browser. Pass
+`browser`, `remote`, and `key` on a tool call when a specific local profile or
+authenticated browser-cli remote is required.
+
+`browser_navigate`, `browser_tabs_close`, and `browser_screenshot` take an
+optional `tab_id` and act on the active tab when it is omitted, so a caller
+does not need a preceding `browser_tabs_list` round trip. `browser_tabs_close`
+reports the tab it closed.
+
+Available tools:
+- `browser_tabs_list`, `browser_tabs_open`, `browser_tabs_close`
+- `browser_navigate`, `browser_page_info`
+- `browser_extract_text`, `browser_extract_markdown`
+- `browser_dom_query`, `browser_dom_click`, `browser_dom_type`
+- `browser_screenshot`
+
+Generic JavaScript evaluation, raw browser commands, storage writes, and
+session import are intentionally not exposed.
+
+### Pinning one browser and naming tools
+Set `BROWSER_CLI_PROFILE` to pin every call from an MCP server to one browser,
+so tools do not have to pass `browser` and listing tools do not fan out across
+all connected browsers:
+```json
+{
+  "mcpServers": {
+    "browser-cli-testing": {
+      "command": "browser-cli-mcp",
+      "env": {
+        "BROWSER_CLI_PROFILE": "testing",
+        "BROWSER_CLI_MCP_TOOL_PREFIX": ""
+      }
+    }
+  }
+}
+```
+`BROWSER_CLI_REMOTE` and `BROWSER_CLI_KEY` pin an authenticated remote the same
+way. Explicit `browser`, `remote`, and `key` tool arguments still win.
+
+Tool names carry a `browser_` prefix by default so they stay unambiguous in
+hosts that expose raw MCP tool names. Hosts that already prefix tools with the
+server name produce stutter such as `browser_cli_testing_browser_tabs_list`;
+setting `BROWSER_CLI_MCP_TOOL_PREFIX` to an empty string drops the built-in
+prefix and yields `browser_cli_testing_tabs_list`. Any other value replaces the
+prefix.
+
+For local development and testing, Streamable HTTP is also available:
+```sh
+browser-cli-mcp --transport streamable-http --port 8000
+# endpoint: http://127.0.0.1:8000/mcp
+```
+
+HTTP uses stateless JSON responses and intentionally refuses non-loopback bind
+addresses because this MCP endpoint has no independent authentication. For a
+browser on another machine, keep MCP local and pass an authenticated
+browser-cli `remote` target to each tool call.
+
+---
+
 ## CLI reference
 During source development, commands are usually run as `uv run browser-cli [--browser ALIAS] <command>`. After tool installation, use `browser-cli ...` directly. Add `--remote HOST[:PORT]` and optionally `--key PATH` to target a browser exposed by `browser-cli serve`.
 

browser_cli/client/core.py

@@ -151,21 +151,25 @@ def active_browser_targets(*, include_remotes: bool = True, key=None, suppress_p
     targets.extend(_remote_browser_targets(key=key, suppress_pq_warning=suppress_pq_warning))
   return targets
 
-def _cached_client_row(target: BrowserTarget) -> dict | None:
+def _cached_client_row(target: BrowserTarget, *, scoped: bool = False) -> dict | None:
   """Build a clients row from a target's discovery data, skipping a roundtrip.
 
   Returns None when the remote didn't advertise its version (older serve), so
-  callers fall back to an explicit ``clients.list`` query.
+  callers fall back to an explicit ``clients.list`` query. When *scoped* is
+  true, the caller already selected one remote host, so render profile-only
+  labels instead of adding a host group header.
   """
   if target.version is None and target.extension_version is None:
     return None
-  return {
-    "profile": target.display_name,
-    "profileGroup": target.display_group,
+  row = {
+    "profile": target.profile if scoped else target.display_name,
     "name": target.browser_name or "",
     "version": target.version or "",
     "extensionVersion": target.extension_version or "",
   }
+  if target.display_group and not scoped:
+    row["profileGroup"] = target.display_group
+  return row
 
 def _rows_from_result(result, label: str, profile_group: str | None) -> list[dict]:
   rows = []
@@ -249,18 +253,17 @@ def collect_browser_clients(
     if targets:
       uncached = []
       for target in targets:
-        cached = _cached_client_row(target)
+        cached = _cached_client_row(target, scoped=True)
         if cached is not None:
           rows.append(cached)
         else:
           uncached.append(target)
       results = _run_concurrent([
         (lambda t=t: _client_rows_async(
-          t.display_name,
+          t.profile,
           profile=t.profile,
           remote=remote,
           key=key,
-          profile_group=t.display_group,
         ))
         for t in uncached
       ])

browser_cli/client/messages.py

@@ -5,8 +5,8 @@ import uuid
 from typing import Any
 
 from browser_cli import transport
-from browser_cli.endpoints import _normalize_endpoint
 from browser_cli.errors import BrowserNotConnected
+from browser_cli.remote.registry import resolve_remote_endpoint
 
 def base_message(command: str, args: dict | None) -> dict:
   return {"id": str(uuid.uuid4()), "command": command, "args": args or {}}
@@ -14,7 +14,7 @@ def base_message(command: str, args: dict | None) -> dict:
 def requested_target(profile: str | None, remote: str | None) -> tuple[str | None, str | None]:
   requested_profile = profile or os.environ.get("BROWSER_CLI_PROFILE")
   remote_endpoint = remote or os.environ.get("BROWSER_CLI_REMOTE")
-  return requested_profile, _normalize_endpoint(remote_endpoint) if remote_endpoint else None
+  return requested_profile, resolve_remote_endpoint(remote_endpoint) if remote_endpoint else None
 
 def encode_payload(msg: dict) -> bytes:
   return json.dumps(msg).encode("utf-8")

browser_cli/mcp/__init__.py

@@ -0,0 +1,5 @@
+"""Stateless Model Context Protocol adapter for browser-cli."""
+
+from browser_cli.mcp.server import create_server, main
+
+__all__ = ["create_server", "main"]

browser_cli/mcp/naming.py

@@ -0,0 +1,39 @@
+"""Tool-name prefixing for the MCP surface.
+
+Hosts differ in how they namespace MCP tools. Hosts that already prefix tool
+names with the server name turn the built-in ``browser_`` prefix into stutter
+(``browser_cli_testing_browser_tabs_list``), while hosts that expose raw names
+need the prefix to keep ``navigate`` or ``screenshot`` unambiguous. The prefix
+is therefore configurable per MCP server process.
+"""
+from __future__ import annotations
+
+import os
+import re
+
+TOOL_PREFIX_ENV = "BROWSER_CLI_MCP_TOOL_PREFIX"
+DEFAULT_TOOL_PREFIX = "browser_"
+
+_VALID_PREFIX = re.compile(r"\A[a-z][a-z0-9_]*\Z")
+
+def resolve_tool_prefix(environ: dict[str, str] | None = None) -> str:
+  """Return the configured tool-name prefix, defaulting to ``browser_``.
+
+  An empty value disables prefixing for hosts that namespace tools themselves.
+  """
+  configured = (environ if environ is not None else os.environ).get(TOOL_PREFIX_ENV)
+  if configured is None:
+    return DEFAULT_TOOL_PREFIX
+  prefix = configured.strip()
+  if not prefix:
+    return ""
+  if not _VALID_PREFIX.match(prefix):
+    raise ValueError(
+      f"{TOOL_PREFIX_ENV} must be lowercase letters, digits, and underscores starting "
+      f"with a letter, or empty to disable prefixing; got {configured!r}"
+    )
+  return prefix if prefix.endswith("_") else f"{prefix}_"
+
+def tool_name(base: str, prefix: str) -> str:
+  """Apply *prefix* to a bare tool name such as ``tabs_list``."""
+  return f"{prefix}{base}"

browser_cli/mcp/serialization.py

@@ -0,0 +1,19 @@
+"""Convert browser-cli SDK models into MCP structured-output values."""
+from __future__ import annotations
+
+from dataclasses import fields, is_dataclass
+from typing import Any
+
+def structured(value: Any) -> Any:
+  """Return JSON-compatible data without private SDK binding fields."""
+  if is_dataclass(value) and not isinstance(value, type):
+    return {
+      field.name: structured(getattr(value, field.name))
+      for field in fields(value)
+      if not field.name.startswith("_")
+    }
+  if isinstance(value, dict):
+    return {str(key): structured(item) for key, item in value.items()}
+  if isinstance(value, (list, tuple, set)):
+    return [structured(item) for item in value]
+  return value

browser_cli/mcp/server.py

@@ -0,0 +1,231 @@
+"""Stateless MCP server exposing a conservative browser-cli tool surface.
+
+The MCP process stores no browser client, tab ID, or navigation state. Every
+call constructs a fresh :class:`browser_cli.BrowserCLI`; the real browser is
+the sole owner of browser state.
+"""
+from __future__ import annotations
+
+import argparse
+import base64
+import os
+from collections.abc import Callable
+from typing import Any, Literal
+from urllib.parse import urlsplit
+
+from browser_cli import BrowserCLI
+from browser_cli.mcp.naming import resolve_tool_prefix, tool_name
+from browser_cli.mcp.serialization import structured
+from browser_cli.mcp.targets import resolve_tab_id
+
+ClientFactory = Callable[..., BrowserCLI]
+
+_SERVER_INSTRUCTIONS = """Control a real, user-visible browser through browser-cli.
+The server is stateless: pass browser, remote, and key on each tool call when a
+specific target is required. Tool calls affect the user's actual browser. Read
+current tabs/page state instead of assuming IDs or content from an earlier call.
+"""
+
+def _client(factory: ClientFactory, browser: str | None, remote: str | None, key: str | None) -> BrowserCLI:
+  """Build a fresh client, making MCP process environment defaults explicit.
+
+  Explicit values are important for SDK multi-browser routing: leaving
+  ``browser=None`` would fan out list/count calls before lower transport code
+  gets a chance to consult ``BROWSER_CLI_PROFILE``.
+  """
+  return factory(
+    browser=browser or os.environ.get("BROWSER_CLI_PROFILE"),
+    remote=remote or os.environ.get("BROWSER_CLI_REMOTE"),
+    key=key or os.environ.get("BROWSER_CLI_KEY"),
+  )
+
+def _screenshot_bytes(data_url: str) -> tuple[bytes, str]:
+  """Decode a browser screenshot data URL into bytes and an MCP image format."""
+  header, separator, payload = data_url.partition(",")
+  if not separator or ";base64" not in header:
+    raise ValueError("Browser returned an invalid screenshot data URL")
+  media_type = header[5:].split(";", 1)[0].lower()
+  image_format = "jpeg" if media_type in {"image/jpeg", "image/jpg"} else "png"
+  return base64.b64decode(payload, validate=True), image_format
+
+def create_server(*, client_factory: ClientFactory = BrowserCLI, tool_prefix: str | None = None):
+  """Create the MCP server. Supplying *client_factory* keeps tests browser-free."""
+  try:
+    from mcp.server import MCPServer
+    from mcp.server.mcpserver import Image
+  except ImportError as exc:  # pragma: no cover - exercised without the optional extra
+    raise RuntimeError(
+      "MCP support is not installed. Install real-browser-cli with the 'mcp' extra: "
+      "uv tool install 'real-browser-cli[mcp]'"
+    ) from exc
+
+  prefix = resolve_tool_prefix() if tool_prefix is None else tool_prefix
+  mcp = MCPServer(
+    "browser-cli",
+    description="Control a real running browser through the browser-cli SDK.",
+    instructions=_SERVER_INSTRUCTIONS,
+  )
+
+  @mcp.tool(name=tool_name("tabs_list", prefix))
+  def tabs_list(
+    browser: str | None = None,
+    remote: str | None = None,
+    key: str | None = None,
+  ) -> list[dict[str, Any]]:
+    """List current tabs. Optionally target a browser alias or authenticated remote."""
+    return structured(_client(client_factory, browser, remote, key).tabs.list())
+
+  @mcp.tool(name=tool_name("tabs_open", prefix))
+  def tabs_open(
+    url: str,
+    wait: bool = False,
+    timeout: float = 30.0,
+    background: bool = False,
+    focus: bool = False,
+    browser: str | None = None,
+    remote: str | None = None,
+    key: str | None = None,
+  ) -> dict[str, Any]:
+    """Open a URL in a new real-browser tab and return its current metadata."""
+    tab = _client(client_factory, browser, remote, key).tabs.open(
+      url, wait=wait, timeout=timeout, background=background, focus=focus
+    )
+    return structured(tab)
+
+  @mcp.tool(name=tool_name("tabs_close", prefix))
+  def tabs_close(
+    tab_id: int | None = None,
+    browser: str | None = None,
+    remote: str | None = None,
+    key: str | None = None,
+  ) -> dict[str, int]:
+    """Close a tab, defaulting to the active tab. This changes the real browser."""
+    client = _client(client_factory, browser, remote, key)
+    target = resolve_tab_id(client, tab_id)
+    return {"closed": client.tabs.close(target), "tab_id": target}
+
+  @mcp.tool(name=tool_name("navigate", prefix))
+  def navigate(
+    url: str,
+    tab_id: int | None = None,
+    browser: str | None = None,
+    remote: str | None = None,
+    key: str | None = None,
+  ) -> dict[str, Any]:
+    """Navigate a tab to a URL, defaulting to the active tab, and return it."""
+    client = _client(client_factory, browser, remote, key)
+    target = resolve_tab_id(client, tab_id)
+    client.nav.to(target, url)
+    return structured(client.tabs.status(target))
+
+  @mcp.tool(name=tool_name("page_info", prefix))
+  def page_info(
+    browser: str | None = None,
+    remote: str | None = None,
+    key: str | None = None,
+  ) -> dict[str, Any]:
+    """Return title, URL, readiness, language, and metadata for the active page."""
+    return structured(_client(client_factory, browser, remote, key).page.info())
+
+  @mcp.tool(name=tool_name("extract_text", prefix))
+  def extract_text(
+    browser: str | None = None,
+    remote: str | None = None,
+    key: str | None = None,
+  ) -> str:
+    """Extract plain text from the active page."""
+    return _client(client_factory, browser, remote, key).extract.text()
+
+  @mcp.tool(name=tool_name("extract_markdown", prefix))
+  def extract_markdown(
+    selector: str | None = None,
+    browser: str | None = None,
+    remote: str | None = None,
+    key: str | None = None,
+  ) -> str:
+    """Extract clean Markdown from the active page or an optional CSS selector."""
+    return _client(client_factory, browser, remote, key).extract.markdown(selector)
+
+  @mcp.tool(name=tool_name("dom_query", prefix))
+  def dom_query(
+    selector: str,
+    browser: str | None = None,
+    remote: str | None = None,
+    key: str | None = None,
+  ) -> list[dict[str, Any]]:
+    """Return elements matching a CSS selector on the active page."""
+    return structured(_client(client_factory, browser, remote, key).dom.query(selector))
+
+  @mcp.tool(name=tool_name("dom_click", prefix))
+  def dom_click(
+    selector: str,
+    browser: str | None = None,
+    remote: str | None = None,
+    key: str | None = None,
+  ) -> dict[str, Any]:
+    """Click the first matching element, then return current active-page info."""
+    client = _client(client_factory, browser, remote, key)
+    client.dom.click(selector)
+    return structured(client.page.info())
+
+  @mcp.tool(name=tool_name("dom_type", prefix))
+  def dom_type(
+    selector: str,
+    text: str,
+    browser: str | None = None,
+    remote: str | None = None,
+    key: str | None = None,
+  ) -> dict[str, bool]:
+    """Type text into the first element matching a CSS selector."""
+    _client(client_factory, browser, remote, key).dom.type(selector, text)
+    return {"typed": True}
+
+  @mcp.tool(name=tool_name("screenshot", prefix), structured_output=False)
+  def screenshot(
+    tab_id: int | None = None,
+    format: Literal["png", "jpeg"] = "png",
+    quality: int | None = None,
+    browser: str | None = None,
+    remote: str | None = None,
+    key: str | None = None,
+  ) -> Any:
+    """Capture the visible area of the active or specified tab as an image."""
+    data_url = _client(client_factory, browser, remote, key).tabs.screenshot(
+      tab_id, format=format, quality=quality
+    )
+    data, actual_format = _screenshot_bytes(data_url)
+    return Image(data=data, format=actual_format)
+
+  return mcp
+
+def _parser() -> argparse.ArgumentParser:
+  parser = argparse.ArgumentParser(description="Run the stateless browser-cli MCP server.")
+  parser.add_argument("--transport", choices=("stdio", "streamable-http"), default="stdio")
+  parser.add_argument("--host", default="127.0.0.1", help="HTTP bind host (streamable-http only).")
+  parser.add_argument("--port", type=int, default=8000, help="HTTP bind port (streamable-http only).")
+  parser.add_argument("--path", default="/mcp", help="MCP endpoint path (streamable-http only).")
+  return parser
+
+def main(argv: list[str] | None = None) -> None:
+  """Run over stdio, or stateless Streamable HTTP when explicitly selected."""
+  args = _parser().parse_args(argv)
+  mcp = create_server()
+  if args.transport == "stdio":
+    mcp.run()
+    return
+  if args.host not in {"127.0.0.1", "localhost", "::1"}:
+    raise SystemExit(
+      "Refusing to expose the unauthenticated MCP server beyond localhost. "
+      "Use browser-cli's authenticated remote transport from a local MCP server instead."
+    )
+  mcp.run(
+    transport="streamable-http",
+    host=args.host,
+    port=args.port,
+    streamable_http_path=args.path,
+    stateless_http=True,
+    json_response=True,
+  )
+
+if __name__ == "__main__":
+  main()

browser_cli/mcp/targets.py

@@ -0,0 +1,16 @@
+"""Tab targeting for the MCP surface.
+
+MCP callers pay a full round trip for every extra tool call, so tools that act
+on a tab accept an optional ``tab_id`` and fall back to the browser's current
+active tab. Resolution happens here rather than by forwarding ``None`` into the
+SDK, so the acting tool always knows which tab it touched and can report it.
+"""
+from __future__ import annotations
+
+from browser_cli import BrowserCLI
+
+def resolve_tab_id(client: BrowserCLI, tab_id: int | None) -> int:
+  """Return *tab_id*, or the ID of the currently active tab when it is ``None``."""
+  if tab_id is not None:
+    return tab_id
+  return client.tabs.active().id

browser_cli/remote/pool.py

@@ -26,6 +26,7 @@ from browser_cli.framing import frame
 # hand back one the server has just timed out and closed.
 _MAX_IDLE_SECONDS = max(5, REMOTE_SESSION_IDLE_TIMEOUT - 5)
 _MAX_PER_ENDPOINT = 8
+_MAX_ENDPOINTS = 64
 
 class PooledConnection:
   __slots__ = ("sock", "secret", "last_used")
@@ -56,10 +57,32 @@ def checkout(endpoint: str) -> PooledConnection | None:
       _close(conn.sock)  # too old — assume the server has dropped it
   return None
 
+def _prune_endpoints_locked(now: float) -> None:
+  """Keep the number of endpoint buckets bounded for long-running SDK users."""
+  for endpoint, bucket in list(_POOL.items()):
+    fresh = [conn for conn in bucket if now - conn.last_used <= _MAX_IDLE_SECONDS]
+    if fresh:
+      _POOL[endpoint] = fresh
+    else:
+      for conn in bucket:
+        _close(conn.sock)
+      _POOL.pop(endpoint, None)
+
+  while len(_POOL) >= _MAX_ENDPOINTS:
+    oldest_endpoint, bucket = min(
+      _POOL.items(),
+      key=lambda item: min(conn.last_used for conn in item[1]) if item[1] else 0.0,
+    )
+    for conn in bucket:
+      _close(conn.sock)
+    _POOL.pop(oldest_endpoint, None)
+
 def checkin(endpoint: str, conn: PooledConnection) -> None:
   """Return a still-healthy connection to the pool for reuse."""
   conn.last_used = time.monotonic()
   with _LOCK:
+    if endpoint not in _POOL and len(_POOL) >= _MAX_ENDPOINTS:
+      _prune_endpoints_locked(conn.last_used)
     bucket = _POOL.setdefault(endpoint, [])
     if len(bucket) >= _MAX_PER_ENDPOINT:
       _close(conn.sock)

browser_cli/remote/registry.py

@@ -22,6 +22,32 @@ def load_remotes() -> dict[str, dict[str, str]]:
   # Normalize keys so old entries stored as "domain:443" match current lookups.
   return {_normalize_endpoint(str(endpoint)): cfg for endpoint, cfg in data.items() if isinstance(cfg, dict)}
 
+def resolve_remote_endpoint(endpoint: str | None) -> str | None:
+  """Resolve a user-supplied remote alias to a remembered endpoint.
+
+  Domain-like remotes without an explicit port still default to :443 when no
+  matching remembered remote exists. If the user remembered exactly one
+  explicit-port remote for the same host (for example
+  ``browser-host.example:8765``), use that endpoint so ``--remote
+  browser-host.example`` targets the stored service instead of assuming HTTPS.
+  """
+  if not endpoint:
+    return None
+  normalized = _normalize_endpoint(endpoint)
+  host, sep, _port = normalized.rpartition(":")
+  if sep:
+    return normalized
+
+  remotes = load_remotes()
+  explicit_matches = []
+  for remote_endpoint in remotes:
+    remote_host, remote_sep, remote_port = remote_endpoint.rpartition(":")
+    if remote_sep and remote_host == normalized and remote_port != "443":
+      explicit_matches.append(remote_endpoint)
+  if len(explicit_matches) == 1:
+    return explicit_matches[0]
+  return normalized
+
 def is_valid_key_spec(value: str) -> bool:
   """Return True for 'agent', 'agent:<selector>', or a plausible key file path."""
   return value == "agent" or value.startswith("agent:") or (

browser_cli/serve/security.py

@@ -70,19 +70,48 @@ class RateLimiter:
   ``rate`` is the sustained refill in tokens/second; ``burst`` is the bucket
   capacity (defaults to ``rate``). ``rate <= 0`` disables limiting entirely.
   Thread-safe so it can be shared across all connections of one serve process.
+
+  The bucket table is capped. Without that bound, a long-running public server
+  could retain one entry per ever-seen identity/IP forever; GC cannot reclaim
+  those entries because the limiter still references them.
   """
 
-  def __init__(self, rate: float, burst: float | None = None) -> None:
+  def __init__(self, rate: float, burst: float | None = None, max_buckets: int = 4096) -> None:
     self.rate = float(rate)
     self.capacity = float(burst) if burst is not None else max(float(rate), 1.0)
+    self.max_buckets = max(1, int(max_buckets))
     self._buckets: dict[str, tuple[float, float]] = {}
     self._lock = threading.Lock()
 
+  def _prune_locked(self, now: float) -> None:
+    """Drop idle/full buckets, then oldest buckets, until the table is bounded."""
+    if len(self._buckets) < self.max_buckets or self.rate <= 0:
+      return
+
+    # Once a bucket has fully refilled, keeping it around carries no useful
+    # throttling state. Use at least 60s so normal active identities are not
+    # churned out aggressively on high-rate configs.
+    idle_seconds = max(60.0, (self.capacity / self.rate) * 2)
+    full_epsilon = 1e-9
+    for bucket_key, (tokens, last) in list(self._buckets.items()):
+      refilled = min(self.capacity, tokens + (now - last) * self.rate)
+      if refilled >= self.capacity - full_epsilon and now - last >= idle_seconds:
+        self._buckets.pop(bucket_key, None)
+
+    # If an attacker keeps creating fresh identities faster than they go idle,
+    # still keep memory bounded. Evict the oldest identity state; that may reset
+    # throttling for that identity, but bounded memory is more important here.
+    while len(self._buckets) >= self.max_buckets:
+      oldest_key = min(self._buckets, key=lambda k: self._buckets[k][1])
+      self._buckets.pop(oldest_key, None)
+
   def allow(self, key: str) -> bool:
     if self.rate <= 0:
       return True
     now = time.monotonic()
     with self._lock:
+      if key not in self._buckets and len(self._buckets) >= self.max_buckets:
+        self._prune_locked(now)
       tokens, last = self._buckets.get(key, (self.capacity, now))
       tokens = min(self.capacity, tokens + (now - last) * self.rate)
       if tokens < 1.0:

extension/manifest.json

@@ -1,7 +1,7 @@
 {
   "manifest_version": 3,
   "name": "browser-cli",
-  "version": "0.16.4",
+  "version": "0.16.6",
   "description": "Control your browser from the terminal or Python SDK",
   "browser_specific_settings": {
     "gecko": {

extension/src/classes/JobManager.ts

@@ -15,6 +15,11 @@ import type { Job, Serializable, ErrorLike, DispatchArgs } from '../types';
 // jobs only need to survive long enough for the CLI to poll their result.
 export const MAX_FINISHED_JOBS = 20;
 
+// Cap simultaneously running background jobs. A hung job has a watchdog, but a
+// command flood could still pin many timers/results for up to JOB_TIMEOUT_MS.
+// Rejecting above this bound keeps service-worker memory predictable.
+export const MAX_RUNNING_JOBS = 32;
+
 // Watchdog: if a runner never resolves/rejects (e.g. executeScript against a
 // dead tab), finalize the job as an error so its persist interval stops instead
 // of writing to api.storage.local every second forever.
@@ -77,6 +82,11 @@ export class JobManager {
   }
 
   async start(command: string, args: DispatchArgs, runner: JobRunner) {
+    const runningCount = [...this.jobs.values()].filter(job => job.status === "running").length;
+    if (runningCount >= MAX_RUNNING_JOBS) {
+      throw new Error(`too many background jobs running (${runningCount}); wait for jobs to finish or cancel one`);
+    }
+
     const jobId = `${Date.now().toString(36)}-${Math.random().toString(36).slice(2, 10)}`;
     const job: Job = {
       id: jobId,

extension/src/commands/perf.ts

@@ -1,7 +1,7 @@
 import { getLargeOperationThrottle, getPerformanceProfile, hasAudibleTabs, setPerformanceProfile } from '../core';
 import { CommandGroup } from '../classes/CommandGroup';
 import type { CommandEntry } from '../classes/CommandGroup';
-import type { PerfSetProfileArgs, JobIdArgs } from '../types';
+import type { Job, PerfSetProfileArgs, JobIdArgs } from '../types';
 
 // PerfCommands also owns the jobs.* status/cancel queries: they read the same
 // JobManager (ctx.jobs) that perf.status reports, and there is no dedicated
@@ -15,15 +15,8 @@ export class PerfCommands extends CommandGroup {
     "jobs.cancel":      (a: JobIdArgs) => this.ctx.jobs.cancel(a),
   };
 
-  private async perfStatus() {
-    const profile = await getPerformanceProfile();
-    const audible = await hasAudibleTabs();
-    const throttle = await getLargeOperationThrottle(0, "auto");
+  private jobSummary(job: Job) {
     return {
-      performanceProfile: profile,
-      audible,
-      throttle,
-      jobs: this.ctx.jobs.list().map(job => ({
       id: job.id,
       command: job.command,
       status: job.status,
@@ -32,7 +25,18 @@ export class PerfCommands extends CommandGroup {
       total: job.total,
       percent: job.percent,
       cancelRequested: job.cancelRequested,
-      })),
+    };
+  }
+
+  private async perfStatus() {
+    const profile = await getPerformanceProfile();
+    const audible = await hasAudibleTabs();
+    const throttle = await getLargeOperationThrottle(0, "auto");
+    return {
+      performanceProfile: profile,
+      audible,
+      throttle,
+      jobs: this.ctx.jobs.list().map(job => this.jobSummary(job)),
     };
   }
 }

extension/src/commands/windows.ts

@@ -14,9 +14,31 @@ export class WindowsCommands extends CommandGroup {
     "windows.open":   (a: WindowsOpenArgs) => this.windowsOpen(a),
   };
 
+  private async activeWindowIds(): Promise<Set<number>> {
+    const windows = await api.windows.getAll({});
+    return new Set(windows.map(w => w.id).filter(id => typeof id === "number"));
+  }
+
+  private async pruneAliases(activeIds?: Set<number>): Promise<Record<string, string>> {
+    const aliases = await getAliases();
+    const liveIds = activeIds || await this.activeWindowIds();
+    const pruned: Record<string, string> = {};
+    let changed = false;
+    for (const [id, alias] of Object.entries(aliases)) {
+      if (liveIds.has(Number(id))) {
+        pruned[id] = alias;
+      } else {
+        changed = true;
+      }
+    }
+    if (changed) await api.storage.local.set({ windowAliases: pruned });
+    return pruned;
+  }
+
   private async windowsList() {
     const windows = await api.windows.getAll({ populate: true });
-    const aliases = await getAliases();
+    const activeIds = new Set(windows.map(w => w.id).filter(id => typeof id === "number"));
+    const aliases = await this.pruneAliases(activeIds);
     return windows.map(w => ({
       id: w.id,
       alias: aliases[w.id] || null,
@@ -27,7 +49,7 @@ export class WindowsCommands extends CommandGroup {
   }
 
   private async windowsRename({ windowId, name }: WindowsRenameArgs) {
-    const aliases = await getAliases();
+    const aliases = await this.pruneAliases();
     aliases[windowId] = name;
     await api.storage.local.set({ windowAliases: aliases });
     return { windowId, name };
@@ -35,6 +57,11 @@ export class WindowsCommands extends CommandGroup {
 
   private async windowsClose({ windowId }: WindowsCloseArgs) {
     await api.windows.remove(windowId);
+    const aliases = await this.pruneAliases();
+    if (windowId in aliases) {
+      delete aliases[windowId];
+      await api.storage.local.set({ windowAliases: aliases });
+    }
     return { windowId };
   }
 

extension/test/jobs.test.ts

@@ -1,7 +1,7 @@
 // @ts-nocheck
 import { test, mock } from 'node:test';
 import assert from 'node:assert/strict';
-import { JobManager, JOB_TIMEOUT_MS, MAX_FINISHED_JOBS, pruneFinishedJobs } from '../src/classes/JobManager';
+import { JobManager, JOB_TIMEOUT_MS, MAX_FINISHED_JOBS, MAX_RUNNING_JOBS, pruneFinishedJobs } from '../src/classes/JobManager';
 import { makeChromeMock } from './chrome-mock';
 
 // Drain pending microtasks (finalize() chains several awaits). setImmediate is
@@ -129,6 +129,21 @@ test('JobManager: a runner that settles after the watchdog cannot resurrect the
   mock.timers.reset();
 });
 
+test('JobManager: rejects new background jobs above the running-job cap', async () => {
+  mock.timers.enable({ apis: ['setInterval', 'setTimeout'] });
+  globalThis.chrome = makeChromeMock();
+  const mgr = new JobManager();
+  for (let i = 0; i < MAX_RUNNING_JOBS; i++) {
+    await mgr.start(`running${i}`, {}, () => new Promise(() => {}));
+  }
+  await assert.rejects(
+    () => mgr.start('overflow', {}, async () => 'nope'),
+    /too many background jobs running/,
+  );
+  assert.equal(mgr.list().filter(job => job.status === 'running').length, MAX_RUNNING_JOBS);
+  mock.timers.reset();
+});
+
 test('JobManager: persisted set keeps running jobs even past the finished cap', async () => {
   mock.timers.enable({ apis: ['setInterval', 'setTimeout'] });
   globalThis.chrome = makeChromeMock();

extension/test/windows.test.ts

@@ -0,0 +1,69 @@
+// @ts-nocheck
+import { test } from 'node:test';
+import assert from 'node:assert/strict';
+import { WindowsCommands } from '../src/commands/windows';
+import { makeChromeMock } from './chrome-mock';
+
+function makeWindowsChromeMock(windows) {
+  const chrome = makeChromeMock();
+  chrome.windows = {
+    getAll: async () => windows,
+    remove: async () => {},
+    create: async () => ({ id: 99 }),
+  };
+  return chrome;
+}
+
+test('windows.list prunes aliases for closed windows', async () => {
+  globalThis.chrome = makeWindowsChromeMock([
+    { id: 1, focused: true, state: 'normal', tabs: [{ id: 10 }] },
+    { id: 2, focused: false, state: 'minimized', tabs: [] },
+  ]);
+  globalThis.chrome.storage.local._store.windowAliases = {
+    1: 'main',
+    2: 'side',
+    999: 'closed',
+  };
+
+  const commands = new WindowsCommands({ jobs: {} });
+  const result = await commands.commands['windows.list']({});
+
+  assert.deepEqual(result.map(w => [w.id, w.alias]), [[1, 'main'], [2, 'side']]);
+  assert.deepEqual(globalThis.chrome.storage.local._store.windowAliases, { 1: 'main', 2: 'side' });
+});
+
+test('windows.rename prunes stale aliases before saving the new name', async () => {
+  globalThis.chrome = makeWindowsChromeMock([
+    { id: 1, focused: true, state: 'normal', tabs: [] },
+    { id: 2, focused: false, state: 'normal', tabs: [] },
+  ]);
+  globalThis.chrome.storage.local._store.windowAliases = {
+    1: 'main',
+    999: 'closed',
+  };
+
+  const commands = new WindowsCommands({ jobs: {} });
+  await commands.commands['windows.rename']({ windowId: 2, name: 'work' });
+
+  assert.deepEqual(globalThis.chrome.storage.local._store.windowAliases, { 1: 'main', 2: 'work' });
+});
+
+test('windows.close removes the closed window alias immediately', async () => {
+  let removed = null;
+  globalThis.chrome = makeWindowsChromeMock([
+    { id: 1, focused: true, state: 'normal', tabs: [] },
+    { id: 2, focused: false, state: 'normal', tabs: [] },
+  ]);
+  globalThis.chrome.windows.remove = async id => { removed = id; };
+  globalThis.chrome.storage.local._store.windowAliases = {
+    1: 'main',
+    2: 'side',
+    999: 'closed',
+  };
+
+  const commands = new WindowsCommands({ jobs: {} });
+  await commands.commands['windows.close']({ windowId: 2 });
+
+  assert.equal(removed, 2);
+  assert.deepEqual(globalThis.chrome.storage.local._store.windowAliases, { 1: 'main' });
+});

pyproject.toml

@@ -1,6 +1,6 @@
 [project]
 name = "real-browser-cli"
-version = "0.16.4"
+version = "0.16.6"
 description = "Control your real running browser from the terminal or Python SDK"
 readme = "README.md"
 license = { file = "LICENSE" }
@@ -22,9 +22,13 @@ Issues = "https://git.yiprawr.dev/Automatisation/browser-cli/issues"
 [project.optional-dependencies]
 # Better/faster remote response compression than the stdlib zlib/gzip fallback.
 fast = ["zstandard>=0.22"]
+mcp = [
+    "mcp>=2,<3",
+]
 
 [project.scripts]
 browser-cli = "browser_cli.cli:main"
+browser-cli-mcp = "browser_cli.mcp.server:main"
 
 [dependency-groups]
 dev = [

tests/conftest.py

@@ -12,6 +12,18 @@ from browser_cli.remote import pool as _remote_pool
 
 TEST_BROWSER_PROFILE = "testing"
 
+@pytest.fixture(autouse=True)
+def _isolate_remote_registry(monkeypatch, tmp_path):
+  """Point the remembered-remote registry at an empty throwaway file.
+
+  Endpoint resolution consults remembered remotes, so without this a developer
+  who has remembered ``host:8765`` sees different results than CI for the same
+  code. Tests that need remembered entries still monkeypatch the path themselves.
+  """
+  monkeypatch.setattr(
+    "browser_cli.remote.registry.REMOTE_REGISTRY_PATH", tmp_path / "empty-remotes.json"
+  )
+
 @pytest.fixture(autouse=True)
 def _clear_remote_pool():
   """Close any pooled remote connections between tests so a connection opened

tests/test_cli.py

@@ -294,29 +294,52 @@ def test_clients_reads_registry_with_trailing_garbage(tmp_path):
   assert "0.8.2" in result.output
 
 def test_clients_remote_uses_remote_endpoint_without_local_registry():
-  def fake_send_command(command, args=None, profile=None, remote=None, key=None):
-    assert command == "clients.list"
-    assert profile is None
-    assert remote == "127.0.0.1:8765"
-    return [{"name": "Chrome", "version": "1", "extensionVersion": "2.3.4"}]
+  target = BrowserTarget(
+    profile="work",
+    display_name="127.0.0.1:work",
+    socket_path="",
+    remote="127.0.0.1:8765",
+    browser_name="Chrome",
+    display_group="127.0.0.1",
+    version="1",
+    extension_version="2.3.4",
+  )
 
   with patch.dict(os.environ, {}, clear=True), patch(
     "browser_cli.commands.clients.REGISTRY_PATH", Path("/nonexistent/browser-cli-registry.json")
-  ), patch("browser_cli.client.core.send_command", side_effect=fake_send_command) as send_command:
+  ), patch("browser_cli.client.core.remote_browser_targets", return_value=[target]), patch(
+    "browser_cli.client.core.send_command"
+  ) as send_command:
     result = CliRunner().invoke(main, ["--remote", "127.0.0.1:8765", "clients"])
 
   assert result.exit_code == 0
-  send_command.assert_called_once()
-  assert "remote" in result.output
+  send_command.assert_not_called()
+  assert "work" in result.output
+  assert "127.0.0.1" not in result.output
   assert "Chrome" in result.output
   assert "2.3.4" in result.output
 
 def test_clients_remote_respects_global_browser_route():
-  with patch.dict(os.environ, {}, clear=True), patch("browser_cli.client.core.send_command", return_value=[]) as send_command:
+  target = BrowserTarget(
+    profile="work",
+    display_name="127.0.0.1:work",
+    socket_path="",
+    remote="127.0.0.1:8765",
+    browser_name="Chrome",
+    display_group="127.0.0.1",
+    version="1",
+    extension_version="2.3.4",
+  )
+
+  with patch.dict(os.environ, {}, clear=True), patch(
+    "browser_cli.client.core.remote_browser_targets", return_value=[target]
+  ), patch("browser_cli.client.core.send_command") as send_command:
     result = CliRunner().invoke(main, ["--remote", "127.0.0.1:8765", "--browser", "work", "clients"])
 
-  assert result.exit_code == 1
-  send_command.assert_called_once_with("clients.list", profile="work", remote="127.0.0.1:8765", key=None)
+  assert result.exit_code == 0
+  send_command.assert_not_called()
+  assert "work" in result.output
+  assert "127.0.0.1" not in result.output
 
 def test_clients_browser_alias_resolves_to_remote():
   """--browser <host> without --remote resolves the alias, fetches all targets from that remote,

tests/test_client.py

@@ -356,7 +356,7 @@ def test_active_browser_targets_includes_remote_targets(monkeypatch, tmp_path):
   assert targets[0].display_group == "browser-host.example"
 
 def test_looks_like_domain():
-  assert _looks_like_domain("browsercli.yiprawr.dev") is True
+  assert _looks_like_domain("browser-host.example") is True
   assert _looks_like_domain("browser-host.example") is True
   assert _looks_like_domain("sub.domain.org") is True
   assert _looks_like_domain("localhost") is False
@@ -365,17 +365,17 @@ def test_looks_like_domain():
   assert _looks_like_domain("host") is False  # no dot
 
 def test_normalize_endpoint_strips_443_for_domains():
-  assert _normalize_endpoint("browsercli.yiprawr.dev:443") == "browsercli.yiprawr.dev"
-  assert _normalize_endpoint("browsercli.yiprawr.dev") == "browsercli.yiprawr.dev"
+  assert _normalize_endpoint("browser-host.example:443") == "browser-host.example"
+  assert _normalize_endpoint("browser-host.example") == "browser-host.example"
   assert _normalize_endpoint("203.0.113.1:443") == "203.0.113.1:443"  # IP: keep port
   assert _normalize_endpoint("localhost:443") == "localhost:443"     # localhost: keep port
   assert _normalize_endpoint("host:8765") == "host:8765"         # non-443 port: unchanged
-  assert _normalize_endpoint("browsercli.yiprawr.dev:8765") == "browsercli.yiprawr.dev:8765"
+  assert _normalize_endpoint("browser-host.example:8765") == "browser-host.example:8765"
 
 def test_resolve_connect_endpoint_adds_443_for_domain():
-  assert _resolve_connect_endpoint("browsercli.yiprawr.dev") == "browsercli.yiprawr.dev:443"
-  assert _resolve_connect_endpoint("browsercli.yiprawr.dev:443") == "browsercli.yiprawr.dev:443"
-  assert _resolve_connect_endpoint("browsercli.yiprawr.dev:8765") == "browsercli.yiprawr.dev:8765"
+  assert _resolve_connect_endpoint("browser-host.example") == "browser-host.example:443"
+  assert _resolve_connect_endpoint("browser-host.example:443") == "browser-host.example:443"
+  assert _resolve_connect_endpoint("browser-host.example:8765") == "browser-host.example:8765"
   assert _resolve_connect_endpoint("host:8765") == "host:8765"
 
 def test_resolve_connect_endpoint_raises_for_bare_non_domain():
@@ -399,9 +399,9 @@ def test_send_command_normalizes_domain_port_443(monkeypatch):
 
   monkeypatch.setattr("browser_cli.client.core._send_remote", fake_send_remote)
 
-  result = send_command("tabs.list", remote="browsercli.yiprawr.dev:443")
+  result = send_command("tabs.list", remote="browser-host.example:443")
   assert result == "ok"
-  assert sent_to["endpoint"] == "browsercli.yiprawr.dev"  # stored/routed without port
+  assert sent_to["endpoint"] == "browser-host.example"  # stored/routed without port
 
 def test_send_command_domain_without_port_defaults_to_443(monkeypatch):
   """--remote domain (no port) is treated as :443."""
@@ -420,14 +420,14 @@ def test_send_command_domain_without_port_defaults_to_443(monkeypatch):
 
   monkeypatch.setattr("browser_cli.client.core._send_remote", fake_send_remote)
 
-  result = send_command("tabs.list", remote="browsercli.yiprawr.dev")
+  result = send_command("tabs.list", remote="browser-host.example")
   assert result == "ok"
-  assert sent_to["endpoint"] == "browsercli.yiprawr.dev"
+  assert sent_to["endpoint"] == "browser-host.example"
 
 def test_domain_display_name_omits_port(monkeypatch, tmp_path):
   """Domain endpoints stored without :443 display as 'domain:profile', not 'domain:443:profile'."""
   remotes_path = tmp_path / "remotes.json"
-  endpoint = "browsercli.yiprawr.dev"
+  endpoint = "browser-host.example"
   remotes_path.write_text(json.dumps({endpoint: {}}), encoding="utf-8")
   monkeypatch.setattr("browser_cli.client.targets.REGISTRY_PATH", tmp_path / "missing-registry.json")
   monkeypatch.setattr("browser_cli.remote.registry.REMOTE_REGISTRY_PATH", remotes_path)
@@ -440,13 +440,13 @@ def test_domain_display_name_omits_port(monkeypatch, tmp_path):
   targets = active_browser_targets()
 
   assert len(targets) == 1
-  assert targets[0].display_name == "browsercli.yiprawr.dev:automatisation"
+  assert targets[0].display_name == "browser-host.example:automatisation"
   assert targets[0].remote == endpoint
 
 def test_domain_display_name_backward_compat_with_stored_443(monkeypatch, tmp_path):
   """Old remotes.json with :443 still displays cleanly without the port."""
   remotes_path = tmp_path / "remotes.json"
-  endpoint = "browsercli.yiprawr.dev:443"  # old format
+  endpoint = "browser-host.example:443"  # old format
   remotes_path.write_text(json.dumps({endpoint: {}}), encoding="utf-8")
   monkeypatch.setattr("browser_cli.client.targets.REGISTRY_PATH", tmp_path / "missing-registry.json")
   monkeypatch.setattr("browser_cli.remote.registry.REMOTE_REGISTRY_PATH", remotes_path)
@@ -459,7 +459,7 @@ def test_domain_display_name_backward_compat_with_stored_443(monkeypatch, tmp_pa
   targets = active_browser_targets()
 
   assert len(targets) == 1
-  assert targets[0].display_name == "browsercli.yiprawr.dev:automatisation"
+  assert targets[0].display_name == "browser-host.example:automatisation"
 
 def test_send_command_explicit_key_does_not_persist_remote_key(monkeypatch, tmp_path):
   """--key is a one-shot override; use `browser-cli remote trust` to remember it."""
@@ -681,7 +681,8 @@ def test_collect_browser_clients_with_explicit_remote_lists_all_targets(monkeypa
 
   rows = collect_browser_clients(remote="browser-host.example:8765", registry_path=tmp_path / "missing-registry.json")
 
-  assert [row["profile"] for row in rows] == ["browser-host.example:main", "browser-host.example:work"]
+  assert [row["profile"] for row in rows] == ["main", "work"]
+  assert [row.get("profileGroup") for row in rows] == [None, None]
   assert [row["name"] for row in rows] == ["Chrome", "Firefox"]
 
 def test_collect_browser_clients_with_explicit_remote_and_browser_filters_target(monkeypatch, tmp_path):
@@ -696,7 +697,8 @@ def test_collect_browser_clients_with_explicit_remote_and_browser_filters_target
 
   rows = collect_browser_clients(remote="browser-host.example:8765", browser_alias="work", registry_path=tmp_path / "missing-registry.json")
 
-  assert [row["profile"] for row in rows] == ["browser-host.example:work"]
+  assert [row["profile"] for row in rows] == ["work"]
+  assert rows[0].get("profileGroup") is None
 
 def test_collect_browser_clients_falls_back_when_version_unknown(monkeypatch, tmp_path):
   """An older remote (no advertised version) still triggers a clients.list query."""

tests/test_mcp.py

@@ -0,0 +1,241 @@
+"""Tests for the optional stateless MCP adapter."""
+from __future__ import annotations
+
+import base64
+from types import SimpleNamespace
+
+import pytest
+
+pytest.importorskip("mcp")
+
+from mcp import Client
+from mcp.types import ImageContent
+
+from browser_cli.mcp.serialization import structured
+from browser_cli.mcp.naming import resolve_tool_prefix
+from browser_cli.mcp.server import _screenshot_bytes, create_server, main
+from browser_cli.models import Tab
+
+class FakeClient:
+  instances: list["FakeClient"] = []
+
+  def __init__(self, browser=None, remote=None, key=None):
+    self.target = (browser, remote, key)
+    self.calls: list[tuple] = []
+    self.tabs = SimpleNamespace(
+      list=self.tabs_list,
+      open=self.tabs_open,
+      close=self.tabs_close,
+      active=self.tabs_active,
+      status=self.tabs_status,
+      screenshot=self.tabs_screenshot,
+    )
+    self.nav = SimpleNamespace(to=self.navigate_to)
+    self.page = SimpleNamespace(info=self.page_info)
+    self.extract = SimpleNamespace(text=self.extract_text, markdown=self.extract_markdown)
+    self.dom = SimpleNamespace(query=self.dom_query, click=self.dom_click, type=self.dom_type)
+    self.instances.append(self)
+
+  def tabs_list(self):
+    return [{"id": 7, "title": "Example", "url": "https://example.com"}]
+
+  def tabs_open(self, url, **kwargs):
+    self.calls.append(("open", url, kwargs))
+    return {"id": 8, "title": "Opened", "url": url}
+
+  def tabs_close(self, tab_id):
+    self.calls.append(("close", tab_id))
+    return 1
+
+  def tabs_active(self):
+    self.calls.append(("active",))
+    return SimpleNamespace(id=7)
+
+  def tabs_status(self, tab_id):
+    self.calls.append(("status", tab_id))
+    return {"id": tab_id, "title": "Navigated", "url": "https://example.com/next"}
+
+  def tabs_screenshot(self, tab_id, **kwargs):
+    self.calls.append(("screenshot", tab_id, kwargs))
+    return "data:image/png;base64," + base64.b64encode(b"png-data").decode()
+
+  def navigate_to(self, tab_id, url):
+    self.calls.append(("navigate", tab_id, url))
+
+  def page_info(self):
+    return {"title": "Example", "url": "https://example.com"}
+
+  def extract_text(self):
+    return "Page text"
+
+  def extract_markdown(self, selector=None):
+    return f"# Page {selector or ''}".rstrip()
+
+  def dom_query(self, selector):
+    return [{"tag": "button", "selector": selector}]
+
+  def dom_click(self, selector):
+    self.calls.append(("click", selector))
+
+  def dom_type(self, selector, text):
+    self.calls.append(("type", selector, text))
+
+@pytest.fixture(autouse=True)
+def clear_instances():
+  FakeClient.instances.clear()
+
+@pytest.fixture
+def anyio_backend():
+  return "asyncio"
+
+@pytest.fixture
+async def client():
+  server = create_server(client_factory=FakeClient)
+  async with Client(server, raise_exceptions=True) as connected:
+    yield connected
+
+@pytest.mark.anyio
+async def test_each_tool_call_constructs_a_fresh_targeted_client(client, monkeypatch):
+  monkeypatch.delenv("BROWSER_CLI_PROFILE", raising=False)
+  monkeypatch.delenv("BROWSER_CLI_REMOTE", raising=False)
+  monkeypatch.delenv("BROWSER_CLI_KEY", raising=False)
+  first = await client.call_tool("browser_tabs_list", {
+    "browser": "work",
+    "remote": "browser-host.example:443",
+    "key": "agent",
+  })
+  second = await client.call_tool("browser_page_info", {})
+
+  assert first.structured_content == {
+    "result": [{"id": 7, "title": "Example", "url": "https://example.com"}]
+  }
+  assert second.structured_content == {
+    "title": "Example",
+    "url": "https://example.com",
+  }
+  assert len(FakeClient.instances) == 2
+  assert FakeClient.instances[0].target == ("work", "browser-host.example:443", "agent")
+  assert FakeClient.instances[1].target == (None, None, None)
+
+@pytest.mark.anyio
+async def test_environment_pins_all_calls_to_one_browser(client, monkeypatch):
+  monkeypatch.setenv("BROWSER_CLI_PROFILE", "testing")
+  monkeypatch.delenv("BROWSER_CLI_REMOTE", raising=False)
+  monkeypatch.delenv("BROWSER_CLI_KEY", raising=False)
+
+  await client.call_tool("browser_tabs_list", {})
+
+  assert FakeClient.instances[-1].target == ("testing", None, None)
+
+def test_tool_prefix_defaults_to_browser_and_is_configurable():
+  assert resolve_tool_prefix({}) == "browser_"
+  assert resolve_tool_prefix({"BROWSER_CLI_MCP_TOOL_PREFIX": ""}) == ""
+  assert resolve_tool_prefix({"BROWSER_CLI_MCP_TOOL_PREFIX": "web"}) == "web_"
+  assert resolve_tool_prefix({"BROWSER_CLI_MCP_TOOL_PREFIX": "web_"}) == "web_"
+  with pytest.raises(ValueError):
+    resolve_tool_prefix({"BROWSER_CLI_MCP_TOOL_PREFIX": "9-bad prefix"})
+
+@pytest.mark.anyio
+async def test_hosts_that_namespace_tools_can_drop_the_builtin_prefix():
+  server = create_server(client_factory=FakeClient, tool_prefix="")
+  async with Client(server, raise_exceptions=True) as connected:
+    names = {tool.name for tool in (await connected.list_tools()).tools}
+
+  assert "tabs_list" in names
+  assert not any(name.startswith("browser_") for name in names)
+
+@pytest.mark.anyio
+async def test_explicit_target_overrides_environment_pin(client, monkeypatch):
+  monkeypatch.setenv("BROWSER_CLI_PROFILE", "testing")
+  monkeypatch.delenv("BROWSER_CLI_REMOTE", raising=False)
+  monkeypatch.delenv("BROWSER_CLI_KEY", raising=False)
+
+  await client.call_tool("browser_tabs_list", {"browser": "main"})
+
+  assert FakeClient.instances[-1].target == ("main", None, None)
+
+@pytest.mark.anyio
+async def test_mutating_tools_use_sdk_and_return_fresh_state(client):
+  opened = await client.call_tool("browser_tabs_open", {
+    "url": "https://example.com",
+    "wait": True,
+    "focus": True,
+  })
+  navigated = await client.call_tool("browser_navigate", {
+    "tab_id": 8,
+    "url": "https://example.com/next",
+  })
+  clicked = await client.call_tool("browser_dom_click", {"selector": "#submit"})
+  typed = await client.call_tool("browser_dom_type", {"selector": "#name", "text": "Daniel"})
+
+  assert opened.structured_content == {
+    "id": 8, "title": "Opened", "url": "https://example.com"
+  }
+  assert navigated.structured_content["id"] == 8
+  assert clicked.structured_content["url"] == "https://example.com"
+  assert typed.structured_content == {"typed": True}
+  assert FakeClient.instances[0].calls == [
+    ("open", "https://example.com", {
+      "wait": True, "timeout": 30.0, "background": False, "focus": True
+    })
+  ]
+  assert FakeClient.instances[1].calls == [
+    ("navigate", 8, "https://example.com/next"), ("status", 8)
+  ]
+
+@pytest.mark.anyio
+async def test_tab_tools_default_to_the_active_tab(client):
+  navigated = await client.call_tool("browser_navigate", {"url": "https://example.com/next"})
+  closed = await client.call_tool("browser_tabs_close", {})
+
+  assert navigated.structured_content["id"] == 7
+  assert closed.structured_content == {"closed": 1, "tab_id": 7}
+  assert FakeClient.instances[0].calls == [
+    ("active",), ("navigate", 7, "https://example.com/next"), ("status", 7)
+  ]
+  assert FakeClient.instances[1].calls == [("active",), ("close", 7)]
+
+@pytest.mark.anyio
+async def test_screenshot_returns_image_content(client):
+  result = await client.call_tool("browser_screenshot", {"tab_id": 7, "format": "png"})
+
+  assert result.structured_content is None
+  assert len(result.content) == 1
+  assert isinstance(result.content[0], ImageContent)
+  assert result.content[0].data == base64.b64encode(b"png-data").decode()
+  assert result.content[0].mime_type == "image/png"
+
+def test_screenshot_decoder_rejects_non_data_url():
+  with pytest.raises(ValueError, match="invalid screenshot"):
+    _screenshot_bytes("not-an-image")
+
+def test_sdk_dataclass_serialization_does_not_traverse_bound_client():
+  tab = Tab(id=7, window_id=1, active=True, title="Example")
+  tab._browser = SimpleNamespace(secret="must not be serialized")
+
+  result = structured(tab)
+
+  assert result["id"] == 7
+  assert result["window_id"] == 1
+  assert "_browser" not in result
+
+def test_http_server_refuses_non_local_bind(monkeypatch):
+  monkeypatch.setattr("browser_cli.mcp.server.create_server", lambda: SimpleNamespace(run=lambda **kwargs: None))
+
+  with pytest.raises(SystemExit, match="Refusing to expose"):
+    main(["--transport", "streamable-http", "--host", "0.0.0.0"])
+
+def test_http_server_enables_stateless_json_transport(monkeypatch):
+  calls = []
+  monkeypatch.setattr("browser_cli.mcp.server.create_server", lambda: SimpleNamespace(run=lambda **kwargs: calls.append(kwargs)))
+
+  main(["--transport", "streamable-http", "--port", "9000", "--path", "/browser"])
+
+  assert calls == [{
+    "transport": "streamable-http",
+    "host": "127.0.0.1",
+    "port": 9000,
+    "streamable_http_path": "/browser",
+    "stateless_http": True,
+    "json_response": True,
+  }]

tests/test_remote_pool.py

@@ -43,6 +43,39 @@ def test_checkin_caps_pool_size():
     b.close()
   pool.close_all()
 
+def test_checkin_caps_endpoint_buckets():
+  pool.close_all()
+  peers = []
+  try:
+    for i in range(pool._MAX_ENDPOINTS + 5):
+      a, b = _socketpair()
+      peers.append(b)
+      pool.checkin(f"host-{i}:443", pool.PooledConnection(a, b"secret"))
+    assert len(pool._POOL) <= pool._MAX_ENDPOINTS
+  finally:
+    for peer in peers:
+      peer.close()
+    pool.close_all()
+
+def test_checkin_prunes_stale_endpoint_buckets():
+  pool.close_all()
+  old_a, old_b = _socketpair()
+  old = pool.PooledConnection(old_a, b"secret")
+  pool.checkin("old:443", old)
+  old.last_used -= pool._MAX_IDLE_SECONDS + 1
+  peers = [old_b]
+  try:
+    for i in range(pool._MAX_ENDPOINTS):
+      a, b = _socketpair()
+      peers.append(b)
+      pool.checkin(f"new-{i}:443", pool.PooledConnection(a, b"secret"))
+    assert "old:443" not in pool._POOL
+    assert len(pool._POOL) <= pool._MAX_ENDPOINTS
+  finally:
+    for peer in peers:
+      peer.close()
+    pool.close_all()
+
 def test_session_inner_message_strips_auth_fields():
   msg = {
     "id": "1", "command": "tabs.list", "args": {}, "user_agent": "browser-cli/1",

tests/test_remote_registry.py

@@ -23,6 +23,23 @@ def test_save_remote_with_key_and_remove(monkeypatch, tmp_path):
   assert remote_registry.remove_remote("browser-host.example:443") is True
   assert remote_registry.load_remotes() == {}
 
+def test_resolve_remote_endpoint_prefers_remembered_explicit_port(monkeypatch, tmp_path):
+  path = tmp_path / "remotes.json"
+  monkeypatch.setattr(remote_registry, "REMOTE_REGISTRY_PATH", path)
+  path.write_text(json.dumps({"browser-host.example": {}, "browser-host.example:8765": {}}), encoding="utf-8")
+
+  assert remote_registry.resolve_remote_endpoint("browser-host.example") == "browser-host.example:8765"
+
+def test_resolve_remote_endpoint_keeps_bare_domain_without_unique_port_match(monkeypatch, tmp_path):
+  path = tmp_path / "remotes.json"
+  monkeypatch.setattr(remote_registry, "REMOTE_REGISTRY_PATH", path)
+  path.write_text(
+    json.dumps({"browser-host.example:8765": {}, "browser-host.example:9000": {}}),
+    encoding="utf-8",
+  )
+
+  assert remote_registry.resolve_remote_endpoint("browser-host.example") == "browser-host.example"
+
 def test_remote_add_list_remove_cli(monkeypatch, tmp_path):
   path = tmp_path / "remotes.json"
   monkeypatch.setattr(remote_registry, "REMOTE_REGISTRY_PATH", path)

tests/test_serve_security.py

@@ -181,6 +181,23 @@ def test_rate_limiter_is_per_key():
   assert limiter.allow("a") is False
   assert limiter.allow("b") is False
 
+def test_rate_limiter_caps_identity_buckets():
+  limiter = RateLimiter(rate=0.0001, burst=1, max_buckets=3)
+  for i in range(10):
+    assert limiter.allow(f"key-{i}") is True
+  assert len(limiter._buckets) <= 3
+
+def test_rate_limiter_prunes_refilled_idle_buckets(monkeypatch):
+  current = 1000.0
+  monkeypatch.setattr("browser_cli.serve.security.time.monotonic", lambda: current)
+  limiter = RateLimiter(rate=1, burst=2, max_buckets=2)
+  assert limiter.allow("old") is True
+  current += 120.0
+  assert limiter.allow("a") is True
+  assert limiter.allow("b") is True
+  assert "old" not in limiter._buckets
+  assert len(limiter._buckets) <= 2
+
 # ── ServeSecurity ────────────────────────────────────────────────────────────────
 
 def test_effective_policy_prefers_per_key_override():