test(bedrock): make the botocore stub windows airtight — kills the vendored-import flake

CI flake mechanism (PR #92617 red, reproduced standalone): tests plant
fake botocore modules via patch.dict; when the REAL botocore.exceptions
is first imported in an interpreter state where a fake parent is (or
was) installed, its 'from botocore.vendored import requests' resolves
against a module with no __path__ and every exception test in the worker
dies with "No module named 'botocore.vendored'" — ordering-dependent,
so green locally, red in CI workers.

Defenses (both, in depth):
- test_bedrock_adapter.py pre-imports the real botocore.exceptions at
  module scope, before any test can stub sys.modules — later imports are
  cache hits that can never re-execute the vendored import under a
  poisoned parent. Proven standalone: fake-parent repro fails without
  the pre-import, succeeds with it.
- autouse _boto_sys_modules_hygiene fixtures in all three files that
  plant fake boto* modules (adapter, integration, model-picker):
  snapshot every boto* sys.modules entry before each test, evict+restore
  after — no stub window can leak state into a later test regardless of
  worker ordering.
- importorskip targets botocore.exceptions (the module the tests
  actually need) instead of bare botocore, so a torn install skips
  instead of erroring.

148/148 across the four affected suites.

tests/agent/test_bedrock_adapter.py

@@ -16,6 +16,57 @@ from unittest.mock import MagicMock, patch
 
 import pytest
 
+# ---------------------------------------------------------------------------
+# botocore import hygiene (anti-flake, Aug 2026)
+#
+# Several tests in this file plant fake ``botocore`` modules in sys.modules
+# (to run without the real package / without touching the AWS credential
+# chain). The real package's ``botocore.exceptions`` lazily executes
+# ``from botocore.vendored import requests`` on FIRST import — if that first
+# import happens while a fake parent is (or was) installed, the chain
+# resolves against a module with no real __path__ and the whole file's
+# exception tests die with ``No module named 'botocore.vendored'`` — but
+# only in interpreter states where nothing imported it earlier (the exact
+# CI-vs-local flake on PR #92617).
+#
+# Two defenses, both required:
+#   1. Import the real exception types HERE, at module scope, before any
+#      test can stub sys.modules. Once cached, later ``from
+#      botocore.exceptions import X`` is a dict hit and can never
+#      re-execute the vendored import under a poisoned parent.
+#   2. An autouse fixture snapshots every boto* sys.modules entry before
+#      each test and restores it after, so no stub window can leak state
+#      into a later test regardless of ordering.
+# ---------------------------------------------------------------------------
+
+try:  # pragma: no cover - exercised implicitly by every exception test
+    from botocore.exceptions import (  # noqa: F401
+        ClientError as _RealClientError,
+        ConnectionClosedError as _RealConnectionClosedError,
+    )
+except Exception:  # botocore genuinely not installed / torn — tests skip
+    _RealClientError = _RealConnectionClosedError = None
+
+_BOTO_PREFIXES = ("botocore", "boto3")
+
+
+@pytest.fixture(autouse=True)
+def _boto_sys_modules_hygiene():
+    """Restore every boto* sys.modules entry after each test (see above)."""
+    import sys as _sys
+
+    saved = {
+        name: mod
+        for name, mod in _sys.modules.items()
+        if name.split(".", 1)[0] in _BOTO_PREFIXES
+    }
+    yield
+    for name in [
+        n for n in _sys.modules if n.split(".", 1)[0] in _BOTO_PREFIXES
+    ]:
+        _sys.modules.pop(name, None)
+    _sys.modules.update(saved)
+
 
 @contextmanager
 def _mock_botocore_session(*, return_value=None, side_effect=None):
@@ -923,7 +974,7 @@ class TestIsStaleConnectionError:
 
 
     def test_detects_botocore_read_timeout(self):
-        pytest.importorskip("botocore", reason="botocore required for Bedrock exception tests")
+        pytest.importorskip("botocore.exceptions", reason="botocore (with working exceptions module) required")
         from agent.bedrock_adapter import is_stale_connection_error
         from botocore.exceptions import ReadTimeoutError
         exc = ReadTimeoutError(endpoint_url="https://bedrock.example")
@@ -962,7 +1013,7 @@ class TestCallConverseInvalidatesOnStaleError:
 
 
     def test_converse_stream_evicts_client_on_stale_error(self):
-        pytest.importorskip("botocore", reason="botocore required for Bedrock exception tests")
+        pytest.importorskip("botocore.exceptions", reason="botocore (with working exceptions module) required")
         from agent.bedrock_adapter import (
             _bedrock_runtime_client_cache,
             call_converse_stream,
@@ -988,7 +1039,7 @@ class TestCallConverseInvalidatesOnStaleError:
 
     def test_converse_does_not_evict_on_non_stale_error(self):
         """Non-stale errors (e.g. ValidationException) leave the client cache alone."""
-        pytest.importorskip("botocore", reason="botocore required for Bedrock exception tests")
+        pytest.importorskip("botocore.exceptions", reason="botocore (with working exceptions module) required")
         from agent.bedrock_adapter import (
             _bedrock_runtime_client_cache,
             call_converse,
@@ -1040,7 +1091,7 @@ class TestStreamingAccessDeniedDetection:
         )
 
     def test_matches_access_denied_client_error(self):
-        pytest.importorskip("botocore", reason="botocore required for Bedrock exception tests")
+        pytest.importorskip("botocore.exceptions", reason="botocore (with working exceptions module) required")
         from agent.bedrock_adapter import is_streaming_access_denied_error
         assert is_streaming_access_denied_error(self._denied_client_error()) is True
 
@@ -1060,7 +1111,7 @@ class TestCallConverseStreamIamFallback:
     streaming action — InvokeModel-only policies keep working."""
 
     def test_falls_back_to_converse_on_streaming_denial(self):
-        pytest.importorskip("botocore", reason="botocore required for Bedrock exception tests")
+        pytest.importorskip("botocore.exceptions", reason="botocore (with working exceptions module) required")
         from agent.bedrock_adapter import (
             _bedrock_runtime_client_cache,
             call_converse_stream,

tests/agent/test_bedrock_integration.py

@@ -14,6 +14,33 @@ from unittest.mock import MagicMock, patch
 import pytest
 
 
+_BOTO_PREFIXES = ("botocore", "boto3")
+
+
+@pytest.fixture(autouse=True)
+def _boto_sys_modules_hygiene():
+    """Snapshot/restore boto* sys.modules around every test.
+
+    Tests here plant fake botocore/boto3 modules; a fake that leaks (or a
+    real submodule first-imported inside a stub window) poisons later
+    imports of the real ``botocore.exceptions`` with
+    ``No module named 'botocore.vendored'`` (PR #92617 CI flake). This
+    fixture makes stub windows airtight regardless of test ordering.
+    """
+    import sys as _sys
+
+    saved = {
+        name: mod
+        for name, mod in _sys.modules.items()
+        if name.split(".", 1)[0] in _BOTO_PREFIXES
+    }
+    yield
+    for name in [n for n in _sys.modules if n.split(".", 1)[0] in _BOTO_PREFIXES]:
+        _sys.modules.pop(name, None)
+    _sys.modules.update(saved)
+
+
+
 class TestProviderRegistry:
     """Verify Bedrock is registered in PROVIDER_REGISTRY."""
 

tests/hermes_cli/test_bedrock_model_picker.py

@@ -20,6 +20,34 @@ from contextlib import contextmanager
 from types import ModuleType
 from unittest.mock import MagicMock, patch
 
+import pytest
+
+_BOTO_PREFIXES = ("botocore", "boto3")
+
+
+@pytest.fixture(autouse=True)
+def _boto_sys_modules_hygiene():
+    """Snapshot/restore boto* sys.modules around every test.
+
+    Tests here plant fake botocore/boto3 modules; a fake that leaks (or a
+    real submodule first-imported inside a stub window) poisons later
+    imports of the real ``botocore.exceptions`` with
+    ``No module named 'botocore.vendored'`` (PR #92617 CI flake). This
+    fixture makes stub windows airtight regardless of test ordering.
+    """
+    import sys as _sys
+
+    saved = {
+        name: mod
+        for name, mod in _sys.modules.items()
+        if name.split(".", 1)[0] in _BOTO_PREFIXES
+    }
+    yield
+    for name in [n for n in _sys.modules if n.split(".", 1)[0] in _BOTO_PREFIXES]:
+        _sys.modules.pop(name, None)
+    _sys.modules.update(saved)
+
+
 from agent.bedrock_adapter import BEDROCK_OPENAI_RESPONSES_MODEL_IDS
 
 _MANTLE_MODELS = list(BEDROCK_OPENAI_RESPONSES_MODEL_IDS)

tests/run_agent/test_streaming.py

@@ -1490,7 +1490,7 @@ class TestBedrockIamStreamingFallback:
         return agent
 
     def test_iam_denial_falls_back_inline_and_disables_streaming(self):
-        pytest.importorskip("botocore", reason="botocore required for Bedrock tests")
+        pytest.importorskip("botocore.exceptions", reason="botocore (with working exceptions module) required")
         from botocore.exceptions import ClientError
 
         agent = self._make_bedrock_agent()
@@ -1614,7 +1614,7 @@ class TestBedrockStreamLivenessWatchdog:
         """A Bedrock stream that opens then stops yielding events trips the
         watchdog: it bumps the cross-turn stale streak and raises TimeoutError
         instead of hanging forever."""
-        pytest.importorskip("botocore", reason="botocore required for Bedrock tests")
+        pytest.importorskip("botocore.exceptions", reason="botocore (with working exceptions module) required")
         import threading as _t
 
         # Tiny stale timeout so the watchdog trips quickly; give-up threshold
@@ -1647,7 +1647,7 @@ class TestBedrockStreamLivenessWatchdog:
     def test_pre_elevated_streak_aborts_before_streaming(self, monkeypatch):
         """A streak already past the give-up threshold aborts at entry with
         RuntimeError — Bedrock never even opens a stream (cross-turn breaker)."""
-        pytest.importorskip("botocore", reason="botocore required for Bedrock tests")
+        pytest.importorskip("botocore.exceptions", reason="botocore (with working exceptions module) required")
 
         monkeypatch.setenv("HERMES_STREAM_STALE_GIVEUP", "5")
 
@@ -1669,7 +1669,7 @@ class TestBedrockStreamLivenessWatchdog:
     def test_successful_stream_resets_streak(self, monkeypatch):
         """A Bedrock stream that completes normally clears any prior stale
         streak so a recovered provider doesn't carry it into later turns."""
-        pytest.importorskip("botocore", reason="botocore required for Bedrock tests")
+        pytest.importorskip("botocore.exceptions", reason="botocore (with working exceptions module) required")
 
         monkeypatch.setenv("HERMES_STREAM_STALE_TIMEOUT", "60")