feat(community): add SearXNG and Browserless web search/fetch tools (#3451)

* feat(community): add SearXNG and Browserless web search/fetch tools

- SearXNG web_search: privacy-focused meta search engine integration
  with configurable base_url via config.yaml tool settings
- Browserless web_fetch: headless browser page fetching with
  readability article extraction
- Both tools are fully configurable through tool config section
- No external API keys required for basic operation

* fix: address PR review feedback and add unit tests

- Guard config.model_extra against None values (review #1, #2)
- Coerce max_results to int when reading from config (review #2)
- Fix web_fetch_tool to use direct HTTP fetch instead of reusing
  the web_search client config (review #3)
- Fix misleading docstring for SearxngClient.fetch (review #4)
- Remove unused target_url variable to pass Ruff lint (review #5)
- Normalize bool config values with _normalize_bool helper to
  handle env-resolved string values correctly (review #6)
- Add unit tests for both SearXNG and Browserless client classes
  and their tool functions with mocked httpx (review #7, #8)

* fix: convert to async httpx to avoid blocking I/O on event loop

- Replace httpx.Client with httpx.AsyncClient in both client classes
- Convert tool functions to async def
- Wrap readability_extractor calls in asyncio.to_thread()
- Update all tests to use pytest.mark.asyncio and async mocks
- Fix import sorting to pass Ruff lint

* fix(browserless): replace deprecated waitUntil with waitForEvent

The Browserless API has deprecated the waitUntil parameter.
Replace with waitForEvent which accepts values like 'networkidle'.
Default is empty (no wait), configurable via config.yaml.

* fix(browserless): remove deprecated gotoTimeout and bestAttempt params

The Browserless /content API does not accept gotoTimeout or bestAttempt
as top-level payload keys. These were being sent unconditionally,
causing 400 Bad Request errors on current Browserless versions.

Changes:
- Remove goto_timeout_ms parameter and 'gotoTimeout' from payload
- Remove best_attempt parameter and 'bestAttempt' from payload
- Remove _normalize_bool helper (no longer needed)
- Remove goto_timeout_ms and best_attempt config reading in tools.py
- Add tests for waitForSelector and reject params
- Verify no deprecated params are sent in test_fetch_html_success

* refactor(searxng): remove web_fetch_tool, decouple from web_search config

SearXNG is a search engine — it should only provide web_search_tool.
The web_fetch responsibility belongs to Browserless (headless Chrome)
or Jina AI, not SearXNG.

Changes:
- Remove web_fetch_tool from SearXNG tools.py and __init__.py
- Remove SearxngClient.fetch() method (no longer needed)
- Remove unused asyncio/readability imports from SearXNG tools.py
- Add test for max_results string-to-int coercion from config
- Add test for search with categories parameter
- Add test for httpx.RequestError handling
- Apply ruff format fixes to browserless_client.py and test files

backend/packages/harness/deerflow/community/browserless/tools.py

@@ -0,0 +1,85 @@
+import asyncio
+import logging
+
+from langchain.tools import tool
+
+from deerflow.config import get_app_config
+from deerflow.utils.readability import ReadabilityExtractor
+
+from .browserless_client import BrowserlessClient
+
+logger = logging.getLogger(__name__)
+
+# readability_extractor runs CPU-bound parsing; always call via asyncio.to_thread
+_readability_extractor = ReadabilityExtractor()
+
+
+def _get_tool_config(tool_name: str) -> dict | None:
+    """Get tool config extras safely, returning None if not configured."""
+    config = get_app_config().get_tool_config(tool_name)
+    if config is None:
+        return None
+    extras = config.model_extra
+    return extras if extras is not None else {}
+
+
+def _get_browserless_client() -> BrowserlessClient:
+    cfg = _get_tool_config("web_fetch")
+    base_url = "http://localhost:3032"
+    token = ""
+    timeout_s = 30.0
+    if cfg is not None:
+        base_url = cfg.get("base_url", base_url)
+        token = cfg.get("token", token)
+        raw = cfg.get("timeout_s", timeout_s)
+        timeout_s = float(raw) if not isinstance(raw, float) else raw
+    return BrowserlessClient(base_url=base_url, token=token, timeout_s=timeout_s)
+
+
+@tool("web_fetch", parse_docstring=True)
+async def web_fetch_tool(url: str) -> str:
+    """Fetch the contents of a web page at a given URL using Browserless (headless Chrome).
+    Only fetch EXACT URLs that have been provided directly by the user or have been returned in results from the web_search and web_fetch tools.
+    This tool can NOT access content that requires authentication, such as private Google Docs or pages behind login walls.
+    Do NOT add www. to URLs that do NOT have them.
+    URLs must include the schema: https://example.com is a valid URL while example.com is an invalid URL.
+
+    Args:
+        url: The URL to fetch the contents of.
+    """
+    try:
+        cfg = _get_tool_config("web_fetch")
+
+        wait_for_event = ""
+        wait_for_timeout_ms = 0
+        wait_for_selector = ""
+        wait_for_selector_timeout_ms = 5000
+        reject_resource_types: list[str] | None = None
+        reject_request_pattern: list[str] | None = None
+
+        if cfg is not None:
+            wait_for_event = cfg.get("wait_for_event", wait_for_event)
+            raw_wait = cfg.get("wait_for_timeout_ms", wait_for_timeout_ms)
+            wait_for_timeout_ms = int(raw_wait) if not isinstance(raw_wait, int) else raw_wait
+            wait_for_selector = cfg.get("wait_for_selector", wait_for_selector)
+
+        client = _get_browserless_client()
+        html = await client.fetch_html(
+            url=url,
+            wait_for_event=wait_for_event,
+            wait_for_timeout_ms=wait_for_timeout_ms,
+            wait_for_selector=wait_for_selector,
+            wait_for_selector_timeout_ms=wait_for_selector_timeout_ms,
+            reject_resource_types=reject_resource_types,
+            reject_request_pattern=reject_request_pattern,
+        )
+
+        if html.startswith("Error:"):
+            return html
+
+        article = await asyncio.to_thread(_readability_extractor.extract_article, html)
+        return article.to_markdown()[:4096]
+
+    except Exception as e:
+        logger.error(f"Error in web_fetch_tool: {e}")
+        return f"Error: {str(e)}"