fix(browser): self-review pass — dead-import, log levels, future-proofing

Addresses findings from two self-review passes pre-merge.

First pass (3-agent parallel review):

1. plugins/browser/browser_use/provider.py: drop the
   ``_ = managed_nous_tools_enabled`` dead-import-hider in
   _get_config_or_none(). The import was actively misleading — the
   helper IS used in _get_config() (separate method, separate import),
   not here. The "keep static analysis happy" comment was wrong about
   what the helper does in this scope.

2. agent/browser_provider.py: drop ``pragma: no cover`` from
   is_configured() / provider_name() backward-compat aliases. They ARE
   covered by ``TestLegacyAbcAliases`` — the pragma would have masked
   future regressions.

3. tools/browser_tool.py: refactor _is_legacy_provider_registry_overridden()
   to compare against a module-frozen _DEFAULT_PROVIDER_REGISTRY snapshot
   instead of hardcoded set of 3 keys. Future maintainers adding a 4th
   built-in provider now just extend _PROVIDER_REGISTRY; the override
   detection adapts automatically. Previously the hardcoded
   ``set(...) != {"browserbase", "browser-use", "firecrawl"}`` would flip
   True forever on any 4-key registry, silently routing every install
   onto the legacy fixture path.

4. tools/browser_tool.py: when explicit ``browser.cloud_provider`` is set
   but the registry has no matching plugin (typo, uninstalled plugin,
   discovery failure), emit a WARNING with actionable text instead of
   silently falling through to auto-detect. Legacy code surfaced a typed
   credentials error via direct class instantiation; this log restores
   the signal in the post-migration path.

5. agent/browser_registry.py: trim the triple-redundant _LEGACY_PREFERENCE
   documentation. Module docstring + 13-line block-comment + 5-line
   inline comment was repeating the same point. Kept the docstring and
   trimmed the block-comment to 5 lines.

6. agent/browser_registry.py: upgrade is_available()-raised logging from
   DEBUG to WARNING with exc_info=True. A provider's availability check
   throwing is unusual enough that users debugging "no cloud provider"
   need the traceback in logs.

7. tests/plugins/browser/check_parity_vs_main.py: drop dead top-level
   imports (os, shutil, tempfile — only referenced inside the
   SUBPROCESS_SCRIPT string literal that runs in a child process).

Second pass (architecture + claim-verification review):

8. tools/browser_tool.py: rewrite the inline comment in _get_cloud_provider
   auto-detect branch. Prior text claimed it "routes through the plugin
   registry's legacy preference walk so third-party plugins still get a
   chance to be selected when they're explicitly configured" — false on
   both counts. The branch uses module-level legacy class aliases
   (BrowserUseProvider / BrowserbaseProvider) directly; third-party
   plugins are intentionally reachable only via explicit
   ``browser.cloud_provider``. Corrected comment now matches behaviour
   and cross-references _LEGACY_PREFERENCE for the firecrawl gate
   rationale.

9. tools/browser_tool.py + tests/tools/test_managed_browserbase_and_modal.py:
   drop the unused ``get_active_browser_provider as
   _registry_get_active_browser_provider`` alias from the
   ``from agent.browser_registry import ...`` block. It was never
   referenced; matching test-stub line in the agent.browser_registry
   SimpleNamespace also dropped. ``get_provider`` is still imported (used
   by the explicit-config dispatch path at line 535).

10. plugins/browser/firecrawl/provider.py: align emergency_cleanup()
    with the early-guard pattern used in browserbase + browser_use
    plugins. Previously firecrawl tried the DELETE and relied on
    ``_headers()`` raising ValueError to trip a "missing credentials"
    warning; same final outcome but a different control flow that read
    like a bug to a maintainer skimming the three modules. Now: if
    is_available() is False, log+return early — identical shape to the
    other two providers.

Verification: 54/54 unit tests + 13/13 parity scenarios still pass.

agent/browser_provider.py

@@ -166,10 +166,10 @@ class BrowserProvider(abc.ABC):
     # and :attr:`name`; they may override ``is_configured`` / ``provider_name``
     # for compatibility with the legacy ABC but it is not required.
 
-    def is_configured(self) -> bool:  # pragma: no cover - trivial delegation
+    def is_configured(self) -> bool:
         """Backward-compat alias for :meth:`is_available`."""
         return self.is_available()
 
-    def provider_name(self) -> str:  # pragma: no cover - trivial delegation
+    def provider_name(self) -> str:
         """Backward-compat alias returning :attr:`display_name`."""
         return self.display_name

agent/browser_registry.py

@@ -99,19 +99,11 @@ def get_provider(name: str) -> Optional[BrowserProvider]:
 # ---------------------------------------------------------------------------
 
 
-# Legacy preference order — preserves behaviour for users who set no
+# Legacy auto-detect order — used when no ``browser.cloud_provider`` is set.
-# ``browser.cloud_provider`` config key. Matches the historic auto-detect
+# Matches the pre-migration walk in :func:`tools.browser_tool._get_cloud_provider`.
-# order in :func:`tools.browser_tool._get_cloud_provider` (Browser Use first
+# Firecrawl is intentionally absent so users with ``FIRECRAWL_API_KEY`` set
-# because it covers both managed Nous gateway and direct API key; Browserbase
+# for web-extract don't get silently routed to a paid cloud browser. See
-# second as the older direct-credentials fallback). Filtered by
+# :func:`_resolve` for the full rationale.
-# ``is_available()`` at walk time so we don't surface a provider the user
-# has no credentials for.
-#
-# Note: ``firecrawl`` is intentionally absent. Pre-migration, the auto-detect
-# branch only considered Browser Use → Browserbase; Firecrawl was reachable
-# only via an explicit ``browser.cloud_provider: firecrawl`` config key.
-# Preserving that gate prevents users with a ``FIRECRAWL_API_KEY`` set for
-# web-extract from accidentally getting routed to a (paid) cloud browser.
 _LEGACY_PREFERENCE = (
     "browser-use",
     "browserbase",
@@ -159,7 +151,10 @@ def _resolve(configured: Optional[str]) -> Optional[BrowserProvider]:
         try:
             return bool(p.is_available())
         except Exception as exc:  # noqa: BLE001
-            logger.debug("provider %s.is_available() raised %s", p.name, exc)
+            logger.warning(
+                "Browser provider %s.is_available() raised %s — treating as unavailable",
+                p.name, exc, exc_info=True,
+            )
             return False
 
     # 1. Explicit "local" short-circuit.

plugins/browser/browser_use/provider.py

@@ -130,9 +130,10 @@ class BrowserUseBrowserProvider(BrowserProvider):
         # managed_tool_gateway pulls in the Nous auth stack which can be
         # heavy and is not needed for direct-API-key users.
         from tools.managed_tool_gateway import resolve_managed_tool_gateway
-        from tools.tool_backend_helpers import managed_nous_tools_enabled, prefers_gateway
+        from tools.tool_backend_helpers import prefers_gateway
 
-        # 1. Direct API key path (unless user explicitly prefers gateway).
+        # Direct API key wins unless the user has explicitly opted into the
+        # managed Nous gateway via ``tool_gateway.browser: gateway``.
         api_key = os.environ.get("BROWSER_USE_API_KEY")
         if api_key and not prefers_gateway("browser"):
             return {
@@ -141,16 +142,10 @@ class BrowserUseBrowserProvider(BrowserProvider):
                 "managed_mode": False,
             }
 
-        # 2. Managed Nous gateway path.
         managed = resolve_managed_tool_gateway("browser-use")
         if managed is None:
             return None
 
-        # Hold reference to managed_nous_tools_enabled so static analysis
-        # doesn't flag the import as unused — the helper is consulted by
-        # _get_config() below to compose a more accurate error message.
-        _ = managed_nous_tools_enabled
-
         return {
             "api_key": managed.nous_user_token,
             "base_url": managed.gateway_origin.rstrip("/"),

plugins/browser/firecrawl/provider.py

@@ -130,17 +130,18 @@ class FirecrawlBrowserProvider(BrowserProvider):
             return False
 
     def emergency_cleanup(self, session_id: str) -> None:
+        if not self.is_available():
+            logger.warning(
+                "Cannot emergency-cleanup Firecrawl session %s — missing credentials",
+                session_id,
+            )
+            return
         try:
             requests.delete(
                 f"{self._api_url()}/v2/browser/{session_id}",
                 headers=self._headers(),
                 timeout=5,
             )
-        except ValueError:
-            logger.warning(
-                "Cannot emergency-cleanup Firecrawl session %s — missing credentials",
-                session_id,
-            )
         except Exception as e:
             logger.debug(
                 "Emergency cleanup failed for Firecrawl session %s: %s", session_id, e

tests/plugins/browser/check_parity_vs_main.py

@@ -19,11 +19,8 @@ Run from the PR worktree:
 from __future__ import annotations
 
 import json
-import os
-import shutil
 import subprocess
 import sys
-import tempfile
 from pathlib import Path
 
 

tests/tools/test_managed_browserbase_and_modal.py

@@ -106,7 +106,6 @@ def _install_fake_tools_package():
         BrowserProvider=_StubBrowserProvider,
     )
     sys.modules["agent.browser_registry"] = types.SimpleNamespace(
-        get_active_browser_provider=lambda: None,
         get_provider=lambda name: None,
         list_providers=lambda: [],
         register_provider=lambda provider: None,

tools/browser_tool.py

@@ -90,7 +90,6 @@ except Exception:
 # shims for callers that import them from this module.
 from agent.browser_provider import BrowserProvider as CloudBrowserProvider  # noqa: F401  (legacy alias)
 from agent.browser_registry import (  # noqa: F401  (test-patchable surface)
-    get_active_browser_provider as _registry_get_active_browser_provider,
     get_provider as _registry_get_browser_provider,
 )
 from plugins.browser.browserbase.provider import (  # noqa: F401  (legacy import surface)
@@ -425,6 +424,10 @@ _PROVIDER_REGISTRY: Dict[str, type] = {
     "browser-use": BrowserUseProvider,
     "firecrawl": FirecrawlProvider,
 }
+# Frozen copy of the import-time _PROVIDER_REGISTRY, used by
+# ``_is_legacy_provider_registry_overridden`` to detect test-time
+# monkeypatching. NEVER mutate this dict.
+_DEFAULT_PROVIDER_REGISTRY: Dict[str, type] = dict(_PROVIDER_REGISTRY)
 
 _cached_cloud_provider: Optional[CloudBrowserProvider] = None
 _cloud_provider_resolved = False
@@ -442,25 +445,23 @@ _browser_engine_resolved = False
 def _is_legacy_provider_registry_overridden() -> bool:
     """Return True when a test has patched ``_PROVIDER_REGISTRY`` to a custom value.
 
-    Detected by comparing identity with the module-level defaults dict
+    Detected by spotting any registered class that *isn't* the canonical
-    populated above. Tests that ``monkeypatch.setattr(browser_tool,
+    plugin-backed class for that name. Tests that
-    "_PROVIDER_REGISTRY", ...)`` swap in a new object; identity differs
+    ``monkeypatch.setattr(browser_tool, "_PROVIDER_REGISTRY", ...)`` install
-    even when the contents happen to match. Used by ``_get_cloud_provider``
+    custom factories (`exploding_factory`, `lambda: fake_provider`, etc.);
-    to honour test-time overrides (which expect a factory-callable shape)
+    those entries fail the canonical-class identity check below.
-    instead of routing through the plugin registry.
+
+    Note: a future maintainer adding a 4th built-in provider only needs to
+    extend ``_DEFAULT_PROVIDER_REGISTRY`` below — they do NOT need to update
+    a hardcoded set of keys here. The detection just compares each registered
+    value against the corresponding canonical class.
     """
-    # The module-level _PROVIDER_REGISTRY is built once at import time. A test
-    # that swaps it via monkeypatch creates a new dict; we detect that via
-    # the registered class identities, not by ``is`` on the dict itself
-    # (the patch may install a dict whose values happen to be the same
-    # classes; treat that as "not overridden").
     try:
-        return (
+        for key, default_cls in _DEFAULT_PROVIDER_REGISTRY.items():
-            _PROVIDER_REGISTRY.get("browserbase") is not BrowserbaseProvider
+            if _PROVIDER_REGISTRY.get(key) is not default_cls:
-            or _PROVIDER_REGISTRY.get("browser-use") is not BrowserUseProvider
+                return True
-            or _PROVIDER_REGISTRY.get("firecrawl") is not FirecrawlProvider
+        # Extra keys not in the default registry → also an override.
-            or set(_PROVIDER_REGISTRY.keys()) != {"browserbase", "browser-use", "firecrawl"}
+        return len(_PROVIDER_REGISTRY) != len(_DEFAULT_PROVIDER_REGISTRY)
-        )
     except Exception:
         return False
 
@@ -532,6 +533,20 @@ def _get_cloud_provider() -> Optional[CloudBrowserProvider]:
                     # populated. Idempotent — cheap on subsequent calls.
                     _ensure_browser_plugins_loaded()
                     resolved = _registry_get_browser_provider(provider_key)
+                    if resolved is None:
+                        # Explicit config name unknown to the registry —
+                        # might be a typo, an uninstalled plugin, or a
+                        # registry-population failure. Warn the user
+                        # (legacy code would have surfaced a typed
+                        # credentials error via direct class instantiation;
+                        # post-migration we surface this WARNING instead).
+                        logger.warning(
+                            "browser.cloud_provider=%r is not a registered "
+                            "browser plugin; falling back to auto-detect "
+                            "(install the corresponding plugin or fix the "
+                            "config key spelling).",
+                            provider_key,
+                        )
             except Exception:
                 logger.warning(
                     "Failed to instantiate explicit cloud_provider %r; will retry on next call",
@@ -545,12 +560,15 @@ def _get_cloud_provider() -> Optional[CloudBrowserProvider]:
         logger.debug("Could not read cloud_provider from config: %s", e)
 
     if resolved is None:
-        # Auto-detect path. When tests have patched the per-class names
+        # Auto-detect path: Browser Use first (managed Nous gateway or
-        # on this module (BrowserUseProvider / BrowserbaseProvider), honour
+        # direct API key), then Browserbase (direct credentials). Uses
-        # them — the test_browser_cloud_provider_cache test relies on this.
+        # the legacy class names imported at the top of this module so
-        # Otherwise route through the plugin registry's legacy preference
+        # tests that ``monkeypatch.setattr(browser_tool, "BrowserUseProvider", ...)``
-        # walk so third-party plugins still get a chance to be selected
+        # keep driving this branch deterministically. Third-party browser
-        # when they're explicitly configured.
+        # plugins are intentionally NOT reachable from auto-detect — they
+        # participate only via explicit ``browser.cloud_provider: <name>``,
+        # mirroring the firecrawl gate documented on
+        # :data:`agent.browser_registry._LEGACY_PREFERENCE`.
         try:
             fallback_provider = BrowserUseProvider()
             if fallback_provider.is_configured():