diff --git a/backend/apps/agents/tools/ssrf_guard.py b/backend/apps/agents/tools/ssrf_guard.py
index 08b98b3e..1a9621e1 100644
--- a/backend/apps/agents/tools/ssrf_guard.py
+++ b/backend/apps/agents/tools/ssrf_guard.py
@@ -62,6 +62,11 @@ def p_is_forbidden_ip(ip_str: str) -> bool:
         ip = ipaddress.ip_address(ip_str)
     except ValueError:
         return True  # unparseable -> block
+    # v6 can carry a v4 target (v4-mapped ::ffff:, 6to4 2002::) and routes to it; judge by the embedded v4 or a private host slips past the v6 list.
+    if ip.version == 6:
+        embedded = ip.ipv4_mapped or ip.sixtofour
+        if embedded is not None:
+            ip = embedded
     if ip.is_loopback:
         return False
     if ip.version == 4:
diff --git a/backend/tests/test_ssrf_guard.py b/backend/tests/test_ssrf_guard.py
new file mode 100644
index 00000000..b8490afd
--- /dev/null
+++ b/backend/tests/test_ssrf_guard.py
@@ -0,0 +1,49 @@
+"""Regression tests for the SSRF guard.
+
+Covers the plain ranges and the v4-in-v6 smuggling bypass: a private/metadata
+v4 target hidden inside a v6 address (v4-mapped ::ffff:, 6to4 2002::) used to
+slip past the v6-only blocklist. Surfaced while running the OPENSAGE
+comprehension-gap probe against this module.
+"""
+
+import pytest
+
+from apps.agents.tools.ssrf_guard import SSRFBlocked, _is_forbidden_ip, assert_safe_url
+
+
+@pytest.mark.parametrize(
+    "ip_str, forbidden",
+    [
+        # plain ranges still behave
+        ("10.0.0.1", True),
+        ("169.254.169.254", True),            # cloud metadata
+        ("8.8.8.8", False),                   # public
+        ("127.0.0.1", False),                 # loopback intentionally allowed
+        ("::1", False),                       # v6 loopback allowed
+        ("2606:4700::1", False),              # public v6
+        ("fe80::1", True),                    # v6 link-local
+        ("not-an-ip", True),                  # unparseable -> block
+        # the bypass: a v4 target smuggled inside a v6 address
+        ("::ffff:10.0.0.1", True),            # v4-mapped private
+        ("::ffff:169.254.169.254", True),     # v4-mapped cloud metadata
+        ("2002:0a00:0001::1", True),          # 6to4 of 10.0.0.1
+        ("::ffff:127.0.0.1", False),          # v4-mapped loopback stays allowed
+        ("::ffff:8.8.8.8", False),            # v4-mapped public stays allowed
+    ],
+)
+def test_is_forbidden_ip(ip_str, forbidden):
+    assert _is_forbidden_ip(ip_str) is forbidden
+
+
+@pytest.mark.asyncio
+async def test_assert_safe_url_blocks_v4_mapped_metadata():
+    # IP-literal host short-circuits before DNS, so this needs no network.
+    with pytest.raises(SSRFBlocked):
+        await assert_safe_url("http://[::ffff:169.254.169.254]/latest/meta-data/")
+
+
+@pytest.mark.asyncio
+async def test_assert_safe_url_allows_v4_mapped_loopback():
+    # App Builder previews on loopback must keep working, even v4-mapped.
+    url = "http://[::ffff:127.0.0.1]:8731/"
+    assert await assert_safe_url(url) == url