Initial commit: hardened DeerFlow factory

Vendored deer-flow upstream (bytedance/deer-flow) plus prompt-injection
hardening:

- New deerflow.security package: content_delimiter, html_cleaner,
  sanitizer (8 layers — invisible chars, control chars, symbols, NFC,
  PUA, tag chars, horizontal whitespace collapse with newline/tab
  preservation, length cap)
- New deerflow.community.searx package: web_search, web_fetch,
  image_search backed by a private SearX instance, every external
  string sanitized and wrapped in <<<EXTERNAL_UNTRUSTED_CONTENT>>>
  delimiters
- All native community web providers (ddg_search, tavily, exa,
  firecrawl, jina_ai, infoquest, image_search) replaced with hard-fail
  stubs that raise NativeWebToolDisabledError at import time, so a
  misconfigured tool.use path fails loud rather than silently falling
  back to unsanitized output
- Native client back-doors (jina_client.py, infoquest_client.py)
  stubbed too
- Native-tool tests quarantined under tests/_disabled_native/
  (collect_ignore_glob via local conftest.py)
- Sanitizer Layer 7 fix: only collapse horizontal whitespace, preserve
  newlines and tabs so list/table structure survives
- Hardened runtime config.yaml references only the searx-backed tools
- Factory overlay (backend/) kept in sync with deer-flow tree as a
  reference / source

See HARDENING.md for the full audit trail and verification steps.

deer-flow/backend/packages/harness/deerflow/sandbox/middleware.py

@@ -0,0 +1,83 @@
+import logging
+from typing import NotRequired, override
+
+from langchain.agents import AgentState
+from langchain.agents.middleware import AgentMiddleware
+from langgraph.runtime import Runtime
+
+from deerflow.agents.thread_state import SandboxState, ThreadDataState
+from deerflow.sandbox import get_sandbox_provider
+
+logger = logging.getLogger(__name__)
+
+
+class SandboxMiddlewareState(AgentState):
+    """Compatible with the `ThreadState` schema."""
+
+    sandbox: NotRequired[SandboxState | None]
+    thread_data: NotRequired[ThreadDataState | None]
+
+
+class SandboxMiddleware(AgentMiddleware[SandboxMiddlewareState]):
+    """Create a sandbox environment and assign it to an agent.
+
+    Lifecycle Management:
+    - With lazy_init=True (default): Sandbox is acquired on first tool call
+    - With lazy_init=False: Sandbox is acquired on first agent invocation (before_agent)
+    - Sandbox is reused across multiple turns within the same thread
+    - Sandbox is NOT released after each agent call to avoid wasteful recreation
+    - Cleanup happens at application shutdown via SandboxProvider.shutdown()
+    """
+
+    state_schema = SandboxMiddlewareState
+
+    def __init__(self, lazy_init: bool = True):
+        """Initialize sandbox middleware.
+
+        Args:
+            lazy_init: If True, defer sandbox acquisition until first tool call.
+                      If False, acquire sandbox eagerly in before_agent().
+                      Default is True for optimal performance.
+        """
+        super().__init__()
+        self._lazy_init = lazy_init
+
+    def _acquire_sandbox(self, thread_id: str) -> str:
+        provider = get_sandbox_provider()
+        sandbox_id = provider.acquire(thread_id)
+        logger.info(f"Acquiring sandbox {sandbox_id}")
+        return sandbox_id
+
+    @override
+    def before_agent(self, state: SandboxMiddlewareState, runtime: Runtime) -> dict | None:
+        # Skip acquisition if lazy_init is enabled
+        if self._lazy_init:
+            return super().before_agent(state, runtime)
+
+        # Eager initialization (original behavior)
+        if "sandbox" not in state or state["sandbox"] is None:
+            thread_id = (runtime.context or {}).get("thread_id")
+            if thread_id is None:
+                return super().before_agent(state, runtime)
+            sandbox_id = self._acquire_sandbox(thread_id)
+            logger.info(f"Assigned sandbox {sandbox_id} to thread {thread_id}")
+            return {"sandbox": {"sandbox_id": sandbox_id}}
+        return super().before_agent(state, runtime)
+
+    @override
+    def after_agent(self, state: SandboxMiddlewareState, runtime: Runtime) -> dict | None:
+        sandbox = state.get("sandbox")
+        if sandbox is not None:
+            sandbox_id = sandbox["sandbox_id"]
+            logger.info(f"Releasing sandbox {sandbox_id}")
+            get_sandbox_provider().release(sandbox_id)
+            return None
+
+        if (runtime.context or {}).get("sandbox_id") is not None:
+            sandbox_id = runtime.context.get("sandbox_id")
+            logger.info(f"Releasing sandbox {sandbox_id} from context")
+            get_sandbox_provider().release(sandbox_id)
+            return None
+
+        # No sandbox to release
+        return super().after_agent(state, runtime)