fix: pin validated DNS for SSRF-safe fetches

maintainer edit: keep MCP HTTP SSRF checks strict, pin validated DNS for direct web_fetch and HTTP/SSE MCP requests, preserve explicit and environment proxy compatibility, and cover the proxy/redirect/rebinding cases with tests.

docs/configuration.md

@@ -1600,18 +1600,21 @@ nanobot uses a shared SSRF guard for built-in web fetches and HTTP/SSE MCP conne
 
 Keep whitelist entries as narrow as possible, such as a single host CIDR (`192.168.1.50/32`). The whitelist is global for the shared SSRF guard; it is not limited to one tool or one MCP server.
 
+HTTP/SSE MCP connections use the same process-wide proxy environment behavior as `web_fetch`: proxied targets use the configured proxy, and URLs excluded by `NO_PROXY` remain DNS-pinned direct connections.
+
 > [!TIP]
-> Use `proxy` in `tools.web` to route all web requests (search + fetch) through a proxy:
+> Use `proxy` in `tools.web` to route web requests through a proxy:
 > ```json
 > { "tools": { "web": { "proxy": "http://127.0.0.1:7890" } } }
 > ```
+> `web_fetch` applies DNS pinning for direct connections. When an explicit `tools.web.proxy` or a process-wide proxy environment variable applies to the target URL, nanobot still validates the requested URL locally, but DNS resolution for the outbound fetch happens at the proxy; configure only trusted proxies. URLs excluded by `NO_PROXY` keep the DNS-pinned direct path unless `tools.web.proxy` is configured.
 
 ### `tools.web`
 
 | Option | Type | Default | Description |
 |--------|------|---------|-------------|
 | `enable` | boolean | `true` | Enable or disable all built-in web tools (`web_search` + `web_fetch`) |
-| `proxy` | string or null | `null` | Proxy for all web requests, for example `http://127.0.0.1:7890` |
+| `proxy` | string or null | `null` | Proxy for web requests, for example `http://127.0.0.1:7890`. `web_fetch` DNS pinning applies only to direct connections; proxied fetches rely on the configured proxy as the trusted network exit. |
 | `userAgent` | string or null | `null` | User-Agent header for all web requests. If null, a browser one will be used |
 
 ### Web Search

nanobot/agent/tools/mcp.py

@@ -25,6 +25,8 @@ from nanobot.bus.events import (
 )
 from nanobot.security.network import (
     PinnedDNSAsyncTransport,
+    env_proxy_applies_to_url,
+    httpx_env_proxy_mounts,
     resolve_url_target,
     validate_url_target,
 )
@@ -179,12 +181,14 @@ async def _probe_http_url(url: str, timeout: float = 3.0) -> bool:
     port = parsed.port
     if not port:
         port = 443 if parsed.scheme == "https" else 80
-    ok, _, resolved_ips = resolve_url_target(url, allow_loopback=True)
+    ok, _, resolved_ips = resolve_url_target(url)
     if not ok:
         return False
+    if env_proxy_applies_to_url(url):
+        return True
+    for target_host in resolved_ips or (host,):
         try:
-        target_host = resolved_ips[0] if resolved_ips else host
+            _reader, writer = await asyncio.wait_for(
-        reader, writer = await asyncio.wait_for(
                 asyncio.open_connection(target_host, port),
                 timeout=timeout,
             )
@@ -193,6 +197,7 @@ async def _probe_http_url(url: str, timeout: float = 3.0) -> bool:
                 await asyncio.wait_for(writer.wait_closed(), timeout=0.2)
             return True
         except (OSError, asyncio.TimeoutError):
+            continue
     return False
 
 
@@ -215,9 +220,17 @@ def _redact_url(url: str) -> str:
         return "<redacted-url>"
 
 
+def _pinned_transport_kwargs() -> dict[str, object]:
+    kwargs: dict[str, object] = {"transport": PinnedDNSAsyncTransport()}
+    mounts = httpx_env_proxy_mounts()
+    if mounts:
+        kwargs["mounts"] = mounts
+    return kwargs
+
+
 async def _validate_mcp_request_url(request: httpx.Request) -> None:
     """Validate each outgoing MCP HTTP request, including redirect targets."""
-    ok, error = validate_url_target(str(request.url), allow_loopback=True)
+    ok, error = validate_url_target(str(request.url))
     if not ok:
         raise httpx.RequestError(
             f"Blocked unsafe MCP URL {_redact_url(str(request.url))} ({error})",
@@ -884,7 +897,7 @@ async def connect_mcp_servers(
                         follow_redirects=True,
                         timeout=timeout,
                         auth=auth,
-                        transport=PinnedDNSAsyncTransport(allow_loopback=True),
+                        **_pinned_transport_kwargs(),
                     )
 
                 read, write = await server_stack.enter_async_context(
@@ -902,7 +915,7 @@ async def connect_mcp_servers(
                         event_hooks={"request": [_validate_mcp_request_url]},
                         follow_redirects=True,
                         timeout=httpx.Timeout(30.0, connect=10.0),
-                        transport=PinnedDNSAsyncTransport(allow_loopback=True),
+                        **_pinned_transport_kwargs(),
                     )
                 )
                 read, write, _ = await server_stack.enter_async_context(

nanobot/agent/tools/web.py

@@ -124,6 +124,26 @@ def _pinned_dns_transport() -> httpx.AsyncBaseTransport:
     return PinnedDNSAsyncTransport()
 
 
+def _fetch_client_kwargs(proxy: str | None, timeout: float) -> dict[str, Any]:
+    from nanobot.security.network import httpx_env_proxy_mounts
+
+    kwargs: dict[str, Any] = {"timeout": timeout}
+    if proxy:
+        kwargs["proxy"] = proxy
+    else:
+        kwargs["transport"] = _pinned_dns_transport()
+        mounts = httpx_env_proxy_mounts()
+        if mounts:
+            kwargs["mounts"] = mounts
+    return kwargs
+
+
+def _unsafe_url_request_error(exc: BaseException) -> str | None:
+    from nanobot.security.network import UnsafeURLRequestError
+
+    return str(exc) if isinstance(exc, UnsafeURLRequestError) else None
+
+
 async def _get_with_safe_redirects(
     client: httpx.AsyncClient,
     url: str,
@@ -136,7 +156,13 @@ async def _get_with_safe_redirects(
         if not is_valid:
             return None, f"Redirect blocked: {error_msg}"
 
+        try:
             response = await client.get(current_url, headers=headers, follow_redirects=False)
+        except httpx.RequestError as exc:
+            unsafe_error = _unsafe_url_request_error(exc)
+            if unsafe_error is not None:
+                return None, f"Redirect blocked: {unsafe_error}"
+            raise
         is_redirect = 300 <= response.status_code < 400
         if not is_redirect:
             return response, None
@@ -175,7 +201,13 @@ async def _stream_with_safe_redirects(
             headers=headers,
             follow_redirects=False,
         )
+        try:
             response = await stream.__aenter__()
+        except httpx.RequestError as exc:
+            unsafe_error = _unsafe_url_request_error(exc)
+            if unsafe_error is not None:
+                return None, None, f"Redirect blocked: {unsafe_error}"
+            raise
         is_redirect = 300 <= response.status_code < 400
         if not is_redirect:
             return response, stream, None
@@ -963,17 +995,11 @@ class WebFetchTool(Tool):
         is_valid, error_msg = _validate_url_safe(url)
         if not is_valid:
             return json.dumps({"error": f"URL validation failed: {error_msg}", "url": url}, ensure_ascii=False)
-        if self.proxy:
-            return json.dumps({
-                "error": "web_fetch proxy is incompatible with DNS-pinned SSRF protection",
-                "url": url,
-            }, ensure_ascii=False)
 
         # Detect and fetch images directly to avoid Jina's textual image captioning
         try:
             async with httpx.AsyncClient(
-                transport=_pinned_dns_transport(),
+                **_fetch_client_kwargs(self.proxy, 15.0),
-                timeout=15.0,
             ) as client:
                 r, stream, redirect_error = await _stream_with_safe_redirects(
                     client,
@@ -995,6 +1021,9 @@ class WebFetchTool(Tool):
                     if stream is not None:
                         await stream.__aexit__(None, None, None)
         except Exception as e:
+            unsafe_error = _unsafe_url_request_error(e)
+            if unsafe_error is not None:
+                return json.dumps({"error": f"URL validation failed: {unsafe_error}", "url": url}, ensure_ascii=False)
             logger.debug("Pre-fetch image detection failed for {}: {}", url, e)
 
         result = None
@@ -1044,8 +1073,7 @@ class WebFetchTool(Tool):
         """Local fallback using readability-lxml."""
         try:
             async with httpx.AsyncClient(
-                timeout=30.0,
+                **_fetch_client_kwargs(self.proxy, 30.0),
-                transport=_pinned_dns_transport(),
             ) as client:
                 r, redirect_error = await _get_with_safe_redirects(
                     client,

nanobot/security/network.py

@@ -8,6 +8,7 @@ import re
 import socket
 from contextlib import contextmanager, suppress
 from urllib.parse import urlparse
+from urllib.request import getproxies, proxy_bypass
 
 import httpx
 
@@ -25,7 +26,6 @@ _BLOCKED_NETWORKS = [
 ]
 
 _URL_RE = re.compile(r"https?://[^\s\"'`;|<>]+", re.IGNORECASE)
-
 _allowed_networks: list[ipaddress.IPv4Network | ipaddress.IPv6Network] = []
 
 
@@ -113,6 +113,66 @@ def validate_url_target(url: str, *, allow_loopback: bool = False) -> tuple[bool
     return ok, error
 
 
+def env_proxy_applies_to_url(url: str) -> bool:
+    """Return True when process proxy settings would proxy this URL."""
+    try:
+        parsed = urlparse(url)
+    except Exception:
+        return False
+    if parsed.scheme not in {"http", "https"} or not parsed.hostname:
+        return False
+
+    proxies = getproxies()
+    proxy_url = proxies.get(parsed.scheme) or proxies.get("all")
+    if not proxy_url:
+        return False
+
+    host = parsed.hostname
+    if parsed.port is not None:
+        host = f"[{host}]:{parsed.port}" if ":" in host else f"{host}:{parsed.port}"
+    return not proxy_bypass(host)
+
+
+def httpx_env_proxy_mounts() -> dict[str, httpx.AsyncBaseTransport | None]:
+    """Build HTTPX proxy mounts while leaving direct routes to the base transport."""
+    proxies = getproxies()
+    mounts: dict[str, httpx.AsyncBaseTransport | None] = {}
+    for scheme in ("http", "https", "all"):
+        proxy_url = proxies.get(scheme)
+        if proxy_url:
+            if "://" not in proxy_url:
+                proxy_url = f"http://{proxy_url}"
+            mounts[f"{scheme}://"] = httpx.AsyncHTTPTransport(proxy=httpx.Proxy(proxy_url))
+
+    if not mounts:
+        return {}
+
+    no_proxy = proxies.get("no", "")
+    if no_proxy == "*":
+        return {}
+    for entry in no_proxy.split(","):
+        pattern = _no_proxy_mount_pattern(entry.strip())
+        if pattern:
+            mounts[pattern] = None
+    return mounts
+
+
+def _no_proxy_mount_pattern(hostname: str) -> str | None:
+    if not hostname:
+        return None
+    if "://" in hostname:
+        return hostname
+
+    unbracketed = hostname.strip("[]")
+    with suppress(ValueError):
+        addr = ipaddress.ip_address(unbracketed)
+        return f"all://[{addr}]" if addr.version == 6 else f"all://{addr}"
+
+    if hostname.lower() == "localhost":
+        return "all://localhost"
+    return f"all://*{hostname}"
+
+
 @contextmanager
 def pin_resolved_url_dns(url: str, resolved_ips: tuple[str, ...]):
     """Pin DNS lookups for the URL hostname to previously validated IPs.
@@ -152,6 +212,10 @@ def pin_resolved_url_dns(url: str, resolved_ips: tuple[str, ...]):
         socket.getaddrinfo = original_getaddrinfo
 
 
+class UnsafeURLRequestError(httpx.RequestError):
+    """Raised when an outgoing request is rejected by URL safety validation."""
+
+
 class PinnedDNSAsyncTransport(httpx.AsyncBaseTransport):
     """HTTPX transport that pins each request to the IPs validated for its URL."""
 
@@ -170,7 +234,7 @@ class PinnedDNSAsyncTransport(httpx.AsyncBaseTransport):
         url = str(request.url)
         ok, error, resolved_ips = resolve_url_target(url, allow_loopback=self._allow_loopback)
         if not ok:
-            raise httpx.RequestError(error, request=request)
+            raise UnsafeURLRequestError(error, request=request)
         async with self._resolver_lock:
             with pin_resolved_url_dns(url, resolved_ips):
                 return await self._inner.handle_async_request(request)

tests/security/test_security_network.py

@@ -11,11 +11,21 @@ import pytest
 from nanobot.security.network import (
     configure_ssrf_whitelist,
     contains_internal_url,
+    env_proxy_applies_to_url,
+    httpx_env_proxy_mounts,
     pin_resolved_url_dns,
     resolve_url_target,
     validate_url_target,
 )
 
+_PROXY_ENV_VARS = ("HTTP_PROXY", "HTTPS_PROXY", "ALL_PROXY", "http_proxy", "https_proxy", "all_proxy")
+
+
+@pytest.fixture(autouse=True)
+def _clear_proxy_env(monkeypatch: pytest.MonkeyPatch) -> None:
+    for name in (*_PROXY_ENV_VARS, "NO_PROXY", "no_proxy"):
+        monkeypatch.delenv(name, raising=False)
+
 
 def _fake_resolve(host: str, results: list[str]):
     """Return a getaddrinfo mock that maps the given host to fake IP results."""
@@ -184,6 +194,18 @@ def test_allows_normal_https():
         assert ok
 
 
+def test_env_proxy_helpers_respect_no_proxy(monkeypatch):
+    monkeypatch.setenv("HTTPS_PROXY", "http://proxy.example:8080")
+    monkeypatch.setenv("NO_PROXY", "localhost,127.0.0.1,::1")
+
+    assert env_proxy_applies_to_url("https://example.com/page")
+    assert not env_proxy_applies_to_url("http://localhost:8765/mcp")
+
+    mounts = httpx_env_proxy_mounts()
+    assert any(transport is None for transport in mounts.values())
+    assert any(transport is not None for transport in mounts.values())
+
+
 # ---------------------------------------------------------------------------
 # contains_internal_url — shell command scanning
 # ---------------------------------------------------------------------------

tests/tools/test_mcp_probe.py

@@ -9,6 +9,16 @@ import pytest
 
 from nanobot.agent.tools.mcp import _probe_http_url, connect_mcp_servers
 from nanobot.agent.tools.registry import ToolRegistry
+from nanobot.security.network import configure_ssrf_whitelist
+
+_PROXY_ENV_VARS = ("HTTP_PROXY", "HTTPS_PROXY", "ALL_PROXY", "http_proxy", "https_proxy", "all_proxy")
+
+
+@pytest.fixture(autouse=True)
+def _clear_proxy_env(monkeypatch: pytest.MonkeyPatch) -> None:
+    for name in (*_PROXY_ENV_VARS, "NO_PROXY", "no_proxy"):
+        monkeypatch.delenv(name, raising=False)
+
 
 # ---------------------------------------------------------------------------
 # _probe_http_url unit tests
@@ -23,9 +33,11 @@ async def test_probe_returns_true_for_open_port(tmp_path):
 
     server = await asyncio.start_server(_close_connection, "127.0.0.1", 0)
     port = server.sockets[0].getsockname()[1]
+    configure_ssrf_whitelist(["127.0.0.1/32"])
     try:
         assert await _probe_http_url(f"http://127.0.0.1:{port}/mcp") is True
     finally:
+        configure_ssrf_whitelist([])
         server.close()
         await server.wait_closed()
 
@@ -51,6 +63,55 @@ async def test_probe_rejects_public_name_resolving_to_loopback():
         assert await _probe_http_url("http://example.com:8765/mcp") is False
 
 
+@pytest.mark.asyncio
+async def test_probe_skips_direct_tcp_when_global_proxy_env_is_set(monkeypatch):
+    def _resolver(hostname, port, family=0, type_=0):
+        return [(socket.AF_INET, socket.SOCK_STREAM, 0, "", ("93.184.216.34", 0))]
+
+    async def _open_connection(*args, **kwargs):
+        raise AssertionError("global proxy env should skip direct TCP probe")
+
+    monkeypatch.setenv("HTTPS_PROXY", "http://proxy.example:8080")
+    monkeypatch.setenv("NO_PROXY", "localhost,127.0.0.1,::1")
+    monkeypatch.setattr("nanobot.agent.tools.mcp.asyncio.open_connection", _open_connection)
+
+    with patch("nanobot.security.network.socket.getaddrinfo", _resolver):
+        assert await _probe_http_url("https://mcp.example.com/mcp") is True
+
+
+@pytest.mark.asyncio
+async def test_probe_tries_next_validated_ip_when_first_is_unreachable(monkeypatch):
+    attempts: list[tuple[str, int]] = []
+
+    class FakeWriter:
+        def close(self):
+            return None
+
+        async def wait_closed(self):
+            return None
+
+    def _resolver(hostname, port, family=0, type_=0):
+        return [
+            (socket.AF_INET, socket.SOCK_STREAM, 0, "", ("93.184.216.34", 0)),
+            (socket.AF_INET, socket.SOCK_STREAM, 0, "", ("93.184.216.35", 0)),
+        ]
+
+    async def _open_connection(host: str, port: int):
+        attempts.append((host, port))
+        if host == "93.184.216.34":
+            raise OSError("first address unreachable")
+        return object(), FakeWriter()
+
+    monkeypatch.setattr("nanobot.security.network.socket.getaddrinfo", _resolver)
+    monkeypatch.setattr("nanobot.agent.tools.mcp.asyncio.open_connection", _open_connection)
+
+    assert await _probe_http_url("http://mcp.example:8765/mcp") is True
+    assert attempts == [
+        ("93.184.216.34", 8765),
+        ("93.184.216.35", 8765),
+    ]
+
+
 # ---------------------------------------------------------------------------
 # connect_mcp_servers skips unreachable HTTP servers
 # ---------------------------------------------------------------------------

tests/tools/test_mcp_tool.py

@@ -23,6 +23,8 @@ from nanobot.agent.tools.mcp import (
 from nanobot.agent.tools.registry import ToolRegistry, is_tool_error_result
 from nanobot.config.schema import MCPServerConfig
 
+_PROXY_ENV_VARS = ("HTTP_PROXY", "HTTPS_PROXY", "ALL_PROXY", "http_proxy", "https_proxy", "all_proxy")
+
 
 class _FakeTextContent:
     def __init__(self, text: str) -> None:
@@ -50,6 +52,12 @@ def fake_mcp_runtime() -> dict[str, object | None]:
     return {"session": None}
 
 
+@pytest.fixture(autouse=True)
+def _clear_proxy_env(monkeypatch: pytest.MonkeyPatch) -> None:
+    for name in (*_PROXY_ENV_VARS, "NO_PROXY", "no_proxy"):
+        monkeypatch.delenv(name, raising=False)
+
+
 @pytest.fixture(autouse=True)
 def _fake_mcp_module(
     monkeypatch: pytest.MonkeyPatch, fake_mcp_runtime: dict[str, object | None]
@@ -712,6 +720,8 @@ async def test_connect_mcp_servers_logs_stdio_pollution_hint(
 @pytest.mark.parametrize(
     "config",
     [
+        MCPServerConfig(url="http://127.0.0.1:9/sse"),
+        MCPServerConfig(type="streamableHttp", url="http://127.0.0.1:9/mcp"),
         MCPServerConfig(url="http://169.254.169.254/sse"),
         MCPServerConfig(type="streamableHttp", url="http://169.254.169.254/mcp"),
     ],
@@ -742,6 +752,93 @@ async def test_connect_mcp_servers_rejects_unsafe_http_urls_before_probe(
     assert any("blocked unsafe URL" in warning for warning in warnings)
 
 
+@pytest.mark.asyncio
+async def test_validate_mcp_request_url_rejects_loopback_without_whitelist() -> None:
+    from nanobot.security.network import configure_ssrf_whitelist
+
+    configure_ssrf_whitelist([])
+    request = httpx.Request("GET", "http://127.0.0.1/private")
+
+    with pytest.raises(httpx.RequestError, match="Blocked unsafe MCP URL"):
+        await mcp_mod._validate_mcp_request_url(request)
+
+
+@pytest.mark.asyncio
+@pytest.mark.parametrize(
+    "config",
+    [
+        MCPServerConfig(type="sse", url="https://mcp.example.com/sse"),
+        MCPServerConfig(type="streamableHttp", url="https://mcp.example.com/mcp"),
+    ],
+)
+async def test_connect_mcp_servers_env_proxy_adds_proxy_mounts_and_keeps_pinned_transport(
+    config: MCPServerConfig,
+    fake_mcp_runtime: dict[str, object | None],
+    monkeypatch: pytest.MonkeyPatch,
+) -> None:
+    fake_mcp_runtime["session"] = _make_fake_session(["demo"])
+    client_kwargs: list[dict[str, object]] = []
+
+    async def _reachable(_url: str) -> bool:
+        return True
+
+    def _validate(_url: str) -> tuple[bool, str]:
+        return True, ""
+
+    class FakeAsyncClient:
+        def __init__(self, *args: object, **kwargs: object) -> None:
+            client_kwargs.append(kwargs)
+
+        async def __aenter__(self) -> object:
+            return self
+
+        async def __aexit__(self, exc_type: object, exc: object, tb: object) -> bool:
+            return False
+
+    @asynccontextmanager
+    async def _capturing_sse_client(_url: str, httpx_client_factory=None):
+        assert httpx_client_factory is not None
+        async with httpx_client_factory():
+            pass
+        yield object(), object()
+
+    @asynccontextmanager
+    async def _capturing_streamable_http_client(_url: str, http_client=None):
+        assert http_client is not None
+        yield object(), object(), object()
+
+    monkeypatch.setenv("HTTPS_PROXY", "http://proxy.example:8080")
+    monkeypatch.setenv("NO_PROXY", "localhost,127.0.0.1,::1")
+    monkeypatch.setattr(mcp_mod, "validate_url_target", _validate)
+    monkeypatch.setattr(mcp_mod, "_probe_http_url", _reachable)
+    monkeypatch.setattr(mcp_mod.httpx, "AsyncClient", FakeAsyncClient)
+    monkeypatch.setattr(sys.modules["mcp.client.sse"], "sse_client", _capturing_sse_client)
+    monkeypatch.setattr(
+        sys.modules["mcp.client.streamable_http"],
+        "streamable_http_client",
+        _capturing_streamable_http_client,
+    )
+
+    registry = ToolRegistry()
+    stacks = await connect_mcp_servers({"remote": config}, registry)
+    for stack in stacks.values():
+        await stack.aclose()
+
+    assert client_kwargs
+    assert all("transport" in kwargs for kwargs in client_kwargs)
+    assert all("mounts" in kwargs for kwargs in client_kwargs)
+
+
+def test_mcp_http_clients_no_proxy_env_keeps_pinned_direct_route(monkeypatch):
+    monkeypatch.setenv("HTTPS_PROXY", "http://proxy.example:8080")
+    monkeypatch.setenv("NO_PROXY", "mcp.example.com")
+
+    kwargs = mcp_mod._pinned_transport_kwargs()
+
+    assert "transport" in kwargs
+    assert any(transport is None for transport in kwargs["mounts"].values())
+
+
 @pytest.mark.asyncio
 @pytest.mark.parametrize(
     ("config", "expected_transport"),

tests/tools/test_web_fetch_security.py

@@ -21,6 +21,13 @@ from nanobot.security.workspace_access import (
 )
 
 _REAL_GETADDRINFO = socket.getaddrinfo
+_PROXY_ENV_VARS = ("HTTP_PROXY", "HTTPS_PROXY", "ALL_PROXY", "http_proxy", "https_proxy", "all_proxy")
+
+
+@pytest.fixture(autouse=True)
+def _clear_proxy_env(monkeypatch: pytest.MonkeyPatch) -> None:
+    for name in (*_PROXY_ENV_VARS, "NO_PROXY", "no_proxy"):
+        monkeypatch.delenv(name, raising=False)
 
 
 def _fake_resolve_private(hostname, port, family=0, type_=0):
@@ -31,6 +38,49 @@ def _fake_resolve_public(hostname, port, family=0, type_=0):
     return [(socket.AF_INET, socket.SOCK_STREAM, 0, "", ("93.184.216.34", 0))]
 
 
+def _patch_web_fetch_fake_client(monkeypatch: pytest.MonkeyPatch) -> list[dict]:
+    client_kwargs: list[dict] = []
+
+    class FakeStreamResponse:
+        status_code = 200
+        headers = {"content-type": "text/html"}
+        url = "https://example.com/page"
+
+        async def __aenter__(self):
+            return self
+
+        async def __aexit__(self, exc_type, exc, tb):
+            return False
+
+    class FakeJinaResponse:
+        status_code = 200
+
+        def raise_for_status(self):
+            return None
+
+        def json(self):
+            return {"data": {"title": "Example", "content": "Hello", "url": "https://example.com/page"}}
+
+    class FakeClient:
+        def __init__(self, *args, **kwargs):
+            client_kwargs.append(kwargs)
+
+        async def __aenter__(self):
+            return self
+
+        async def __aexit__(self, exc_type, exc, tb):
+            return False
+
+        def stream(self, method, url, headers=None, **kwargs):
+            return FakeStreamResponse()
+
+        async def get(self, url, headers=None, **kwargs):
+            return FakeJinaResponse()
+
+    monkeypatch.setattr(web_module.httpx, "AsyncClient", FakeClient)
+    return client_kwargs
+
+
 @pytest.mark.asyncio
 async def test_web_fetch_blocks_private_ip():
     tool = WebFetchTool()
@@ -148,16 +198,80 @@ async def test_safe_redirect_requests_use_independent_pinned_dns_concurrently(mo
 
 
 @pytest.mark.asyncio
-async def test_web_fetch_rejects_proxy_because_upstream_dns_cannot_be_pinned():
+async def test_web_fetch_proxy_remains_supported(monkeypatch):
-    tool = WebFetchTool(proxy="http://proxy.example:8080")
+    tool = WebFetchTool(proxy="http://config-proxy.example:7890")
+    client_kwargs = _patch_web_fetch_fake_client(monkeypatch)
+
+    monkeypatch.setenv("HTTPS_PROXY", "http://env-proxy.example:8080")
+    monkeypatch.setenv("NO_PROXY", "example.com")
 
     with patch("nanobot.security.network.socket.getaddrinfo", _fake_resolve_public):
         result = await tool.execute(url="https://example.com/page")
 
+    data = json.loads(result)
+    assert data["extractor"] == "jina"
+    assert all(kwargs["proxy"] == "http://config-proxy.example:7890" for kwargs in client_kwargs)
+    assert all("mounts" not in kwargs for kwargs in client_kwargs)
+    assert all("transport" not in kwargs for kwargs in client_kwargs)
+
+
+@pytest.mark.asyncio
+async def test_web_fetch_env_proxy_adds_proxy_mounts_and_keeps_pinned_transport(monkeypatch):
+    tool = WebFetchTool()
+    client_kwargs = _patch_web_fetch_fake_client(monkeypatch)
+
+    monkeypatch.setenv("HTTPS_PROXY", "http://proxy.example:8080")
+    monkeypatch.setenv("NO_PROXY", "localhost,127.0.0.1,::1")
+
+    with patch("nanobot.security.network.socket.getaddrinfo", _fake_resolve_public):
+        result = await tool.execute(url="https://example.com/page")
+
+    data = json.loads(result)
+    assert data["extractor"] == "jina"
+    fetch_kwargs = [kwargs for kwargs in client_kwargs if kwargs.get("timeout") == 15.0]
+    assert fetch_kwargs
+    assert all("transport" in kwargs for kwargs in fetch_kwargs)
+    assert all("mounts" in kwargs for kwargs in fetch_kwargs)
+
+
+def test_web_fetch_no_proxy_env_keeps_pinned_direct_route(monkeypatch):
+    monkeypatch.setenv("HTTPS_PROXY", "http://proxy.example:8080")
+    monkeypatch.setenv("NO_PROXY", "example.com")
+
+    kwargs = web_module._fetch_client_kwargs(None, 15.0)
+
+    assert "transport" in kwargs
+    assert any(transport is None for transport in kwargs["mounts"].values())
+
+
+@pytest.mark.asyncio
+async def test_web_fetch_does_not_fallback_after_pinned_dns_rebind_rejection(monkeypatch):
+    calls = {"evil.example": 0}
+
+    def _rebinding_resolver(hostname, port, family=0, type_=0, proto=0, flags=0):
+        host = str(hostname).rstrip(".").lower()
+        calls[host] += 1
+        ip = "93.184.216.34" if calls[host] <= 2 else "169.254.169.254"
+        return [(socket.AF_INET, socket.SOCK_STREAM, 0, "", (ip, 0))]
+
+    tool = WebFetchTool()
+
+    async def _unexpected_jina(*args, **kwargs):
+        raise AssertionError("Jina fallback should not run after an SSRF rejection")
+
+    async def _unexpected_readability(*args, **kwargs):
+        raise AssertionError("Readability fallback should not run after an SSRF rejection")
+
+    monkeypatch.setattr(tool, "_fetch_jina", _unexpected_jina)
+    monkeypatch.setattr(tool, "_fetch_readability", _unexpected_readability)
+
+    with patch("nanobot.security.network.socket.getaddrinfo", _rebinding_resolver):
+        result = await tool.execute(url="http://evil.example/page")
+
     data = json.loads(result)
     assert "error" in data
-    assert "proxy" in data["error"].lower()
+    assert "blocked" in data["error"].lower()
-    assert "dns-pinned" in data["error"].lower()
+    assert calls["evil.example"] == 3
 
 
 @pytest.mark.asyncio