diff --git a/.buildkite/test_areas/misc.yaml b/.buildkite/test_areas/misc.yaml
index 198def78e03c..5cbd074cba07 100644
--- a/.buildkite/test_areas/misc.yaml
+++ b/.buildkite/test_areas/misc.yaml
@@ -574,7 +574,9 @@ steps:
   - tools/pre_commit/test_tethering_allowlist.txt
   - tests/tools/test_check_test_tethering.py
   - tools/pre_commit/check_agent_files.py
+  - tools/pre_commit/check_forbidden_imports.py
   - tests/tools/test_check_agent_files.py
+  - tests/tools/test_check_forbidden_imports.py
   - tests/tool_parsers
   - tests/tokenizers_
   - tests/parser
@@ -626,6 +628,7 @@ steps:
   - pytest -v -s config
   - pytest -v -s tools/test_check_test_tethering.py
   - pytest -v -s tools/test_check_agent_files.py
+  - pytest -v -s tools/test_check_forbidden_imports.py
 
 - label: ":computer: (CPU) Reasoning + Renderers"
   key: cpu-reasoning-renderers
diff --git a/tests/tools/test_check_forbidden_imports.py b/tests/tools/test_check_forbidden_imports.py
new file mode 100644
index 000000000000..7ee8d795e744
--- /dev/null
+++ b/tests/tools/test_check_forbidden_imports.py
@@ -0,0 +1,57 @@
+# SPDX-License-Identifier: Apache-2.0
+# SPDX-FileCopyrightText: Copyright contributors to the vLLM project
+"""Portable proof imports stay local to exact files and import families."""
+
+import subprocess
+import sys
+from pathlib import Path
+
+import pytest
+
+from tools.pre_commit.check_forbidden_imports import check_file
+
+
+@pytest.mark.parametrize(
+    ("name", "source", "expected"),
+    [
+        ("native_semantic_collector.py", "import base64\nimport re\n", 0),
+        ("native_tensor_artifact_transport.py", "import base64\nimport re\n", 0),
+        ("native_tensor_witness.py", "import base64\n", 0),
+        ("native_tensor_runtime_contract.py", "import re\n", 0),
+        ("neighbor.py", "import base64\n", 1),
+        ("neighbor.py", "import re\n", 1),
+        ("native_tensor_witness.py", "import re\n", 1),
+        ("native_tensor_runtime_contract.py", "import base64\n", 1),
+        ("native_semantic_collector.py", "import pickle\n", 1),
+    ],
+)
+def test_portable_exception_preserves_other_files_and_rules(
+    tmp_path, monkeypatch, name, source, expected
+):
+    monkeypatch.chdir(tmp_path)
+    path = Path("vllm/plugins") / name
+    path.parent.mkdir(parents=True)
+    path.write_text(source)
+    assert check_file(str(path)) == expected
+
+
+def test_canonical_protocol_modules_import_without_site_packages():
+    root = Path(__file__).resolve().parents[2]
+    # Namespace shells load the actual protocol bytes without starting vLLM.
+    # The isolated interpreter cannot import C-extension fast-codec packages.
+    script = """
+import importlib, pathlib, sys, types
+root = pathlib.Path(sys.argv[1])
+for name, path in [('vllm', root / 'vllm'),
+                   ('vllm.plugins', root / 'vllm/plugins')]:
+    package = types.ModuleType(name)
+    package.__path__ = [str(path)]
+    sys.modules[name] = package
+for name in ['native_semantic_collector', 'native_tensor_artifact_transport',
+             'native_tensor_runtime_contract', 'native_tensor_witness',
+             'native_attention_operator_observer', 'native_phase_drain']:
+    module = importlib.import_module('vllm.plugins.' + name)
+    assert pathlib.Path(module.__file__).parent == root / 'vllm/plugins'
+assert not {'pybase64', 'regex', 'torch', 'torch_npu'} & sys.modules.keys()
+"""
+    subprocess.run([sys.executable, "-I", "-S", "-c", script, str(root)], check=True)
diff --git a/tools/pre_commit/check_forbidden_imports.py b/tools/pre_commit/check_forbidden_imports.py
index d80a8e1fd26d..834941e5e9bb 100644
--- a/tools/pre_commit/check_forbidden_imports.py
+++ b/tools/pre_commit/check_forbidden_imports.py
@@ -87,6 +87,14 @@ class ForbiddenImport:
             "or 'import pybase64 as base64'."
         ),
         allowed_pattern=re.compile(r"^\s*import\s+pybase64(\s*|\s+as\s+base64\s*)$"),
+        # These bounded protocol modules must also run in an independent
+        # stdlib-only, cross-architecture evidence replayer. Other imports in
+        # these files remain checked; inference code retains the fast imports.
+        allowed_files={
+            "vllm/plugins/native_semantic_collector.py",
+            "vllm/plugins/native_tensor_artifact_transport.py",
+            "vllm/plugins/native_tensor_witness.py",
+        },
     ),
     "re": ForbiddenImport(
         # regex has no equivalent of the private sre modules
@@ -96,7 +104,13 @@ class ForbiddenImport:
         ),
         tip="Replace 'import re' with 'import regex as re' or 'import regex'.",
         allowed_pattern=re.compile(r"^\s*import\s+regex(\s*|\s+as\s+re\s*)$"),
-        allowed_files={"setup.py"},
+        # Exact portable protocol files only; do not exempt their directory.
+        allowed_files={
+            "setup.py",
+            "vllm/plugins/native_semantic_collector.py",
+            "vllm/plugins/native_tensor_artifact_transport.py",
+            "vllm/plugins/native_tensor_runtime_contract.py",
+        },
     ),
     "triton": ForbiddenImport(
         pattern=r"^(from|import)\s+triton(\s|\.|$)",
diff --git a/vllm/plugins/native_semantic_collector.py b/vllm/plugins/native_semantic_collector.py
index 0a2afd724df6..1cb2f0a3954d 100644
--- a/vllm/plugins/native_semantic_collector.py
+++ b/vllm/plugins/native_semantic_collector.py
@@ -11,9 +11,11 @@
 from __future__ import annotations
 
 import argparse
+import base64
 import hashlib
 import json
 import os
+import re
 import socket
 import socketserver
 import stat
@@ -23,9 +25,6 @@
 from pathlib import Path
 from typing import Any
 
-import pybase64 as base64
-import regex as re
-
 MAX_FRAME = 65536
 MAPPING = "ecpa-native-request-id-mapping/v1"
 UPLOAD = "ecpa-native-block-table-upload/v1"
diff --git a/vllm/plugins/native_tensor_artifact_transport.py b/vllm/plugins/native_tensor_artifact_transport.py
index 09496012ab08..8f0f1e9531ba 100644
--- a/vllm/plugins/native_tensor_artifact_transport.py
+++ b/vllm/plugins/native_tensor_artifact_transport.py
@@ -6,16 +6,15 @@
 from __future__ import annotations
 
 import argparse
+import base64
 import json
 import os
+import re
 import stat
 import time
 from pathlib import Path
 from typing import TYPE_CHECKING, Any
 
-import pybase64 as base64
-import regex as re
-
 if TYPE_CHECKING or (__package__ and __package__.startswith("vllm.")):
     from . import native_semantic_collector as native
     from . import native_tensor_runtime_contract as runtime_contract
diff --git a/vllm/plugins/native_tensor_runtime_contract.py b/vllm/plugins/native_tensor_runtime_contract.py
index d6f094af0fb7..2d084a1f75c7 100644
--- a/vllm/plugins/native_tensor_runtime_contract.py
+++ b/vllm/plugins/native_tensor_runtime_contract.py
@@ -5,10 +5,9 @@
 
 from __future__ import annotations
 
+import re
 from typing import TYPE_CHECKING
 
-import regex as re
-
 if TYPE_CHECKING or (__package__ and __package__.startswith("vllm.")):
     from . import native_tensor_witness as witness
 else:
diff --git a/vllm/plugins/native_tensor_witness.py b/vllm/plugins/native_tensor_witness.py
index 4e8845c90dc2..69c748b89e90 100644
--- a/vllm/plugins/native_tensor_witness.py
+++ b/vllm/plugins/native_tensor_witness.py
@@ -5,12 +5,11 @@
 
 from __future__ import annotations
 
+import base64
 import hashlib
 import time
 from typing import Any, cast
 
-import pybase64 as base64
-
 SCHEMA = "ecpa-selected-KV-materialization-source-candidate/v1"
 _sink: Any = None