diff --git a/backend/tests/test_skill_mutation_host_lifecycle.py b/backend/tests/test_skill_mutation_host_lifecycle.py
index ad5a4ccc39..3cc3ab8685 100644
--- a/backend/tests/test_skill_mutation_host_lifecycle.py
+++ b/backend/tests/test_skill_mutation_host_lifecycle.py
@@ -1,6 +1,7 @@
 """The host owns recovery even when every extension is disabled."""
 
 import asyncio
+import os
 import threading
 from contextlib import contextmanager
 from types import SimpleNamespace
@@ -21,6 +22,8 @@ from deerflow.persistence.skill_mutations.model import SkillOwnerRow, SkillPropo
 from deerflow.persistence.user.model import UserRow
 from deerflow.runtime.events.store.db import DbRunEventStore
 
+pytestmark = pytest.mark.skipif(os.name != "posix", reason="host skill mutation tests require POSIX filesystem primitives")
+
 
 @pytest_asyncio.fixture
 async def durable(tmp_path):
diff --git a/backend/tests/test_skill_mutation_package_cost.py b/backend/tests/test_skill_mutation_package_cost.py
index 7e17c2c248..e83d3d766a 100644
--- a/backend/tests/test_skill_mutation_package_cost.py
+++ b/backend/tests/test_skill_mutation_package_cost.py
@@ -1,5 +1,6 @@
 """Reproducible local capture measurements; not a model/provider benchmark."""
 
+import os
 import statistics
 import time
 
@@ -7,6 +8,8 @@ import pytest
 
 from deerflow.skills.mutations.assets import capture_package
 
+pytestmark = pytest.mark.skipif(os.name != "posix", reason="package capture requires POSIX filesystem primitives")
+
 
 @pytest.mark.parametrize("files,size", [(4, 1024), (256, 65535)])
 def test_capture_cost_at_typical_and_package_limit(tmp_path, files, size):
diff --git a/backend/tests/test_skill_mutation_validation.py b/backend/tests/test_skill_mutation_validation.py
index 5f30babce2..6a0d14859d 100644
--- a/backend/tests/test_skill_mutation_validation.py
+++ b/backend/tests/test_skill_mutation_validation.py
@@ -54,6 +54,7 @@ def test_non_finite_frontmatter_has_stable_error_code():
         validate_candidate(content, content, "example")
 
 
+@pytest.mark.skipif(os.name != "posix", reason="package capture requires POSIX filesystem primitives")
 def test_package_snapshot_covers_support_bytes_and_execute_flags(tmp_path):
     (tmp_path / "SKILL.md").write_text(BASE, encoding="utf-8")
     support = tmp_path / "script.sh"
@@ -68,6 +69,7 @@ def test_package_snapshot_covers_support_bytes_and_execute_flags(tmp_path):
     assert before_mode.digest != capture_package(tmp_path).digest
 
 
+@pytest.mark.skipif(os.name != "posix", reason="package capture requires POSIX filesystem primitives")
 def test_snapshot_detached_from_live_files(tmp_path):
     main = tmp_path / "SKILL.md"
     main.write_text(BASE, encoding="utf-8")
@@ -109,6 +111,7 @@ def test_automatic_capture_rejects_links_and_special_files(tmp_path, kind):
         capture_package(root)
 
 
+@pytest.mark.skipif(os.name != "posix", reason="package capture requires POSIX filesystem primitives")
 def test_snapshot_never_returns_a_partially_captured_package(tmp_path):
     (tmp_path / "SKILL.md").write_text(BASE, encoding="utf-8")
     for index in range(256):
diff --git a/backend/tests/test_skill_mutations.py b/backend/tests/test_skill_mutations.py
index cf9a540672..de53c6f160 100644
--- a/backend/tests/test_skill_mutations.py
+++ b/backend/tests/test_skill_mutations.py
@@ -2,6 +2,7 @@
 
 import asyncio
 import importlib.util
+import os
 from dataclasses import asdict, dataclass
 from types import SimpleNamespace
 
@@ -24,6 +25,8 @@ from deerflow.skills.mutations.repository import SkillMutationRepository
 from deerflow.skills.mutations.scanner import ScanVerdict
 from deerflow.skills.storage.user_scoped_skill_storage import UserScopedSkillStorage
 
+pytestmark = pytest.mark.skipif(os.name != "posix", reason="host skill mutation tests require POSIX filesystem primitives")
+
 CONTENT = "---\nname: example\ndescription: Before\n---\nA\n"
 NEW = CONTENT.replace("\nA\n", "\nB\n")
 
diff --git a/backend/tests/test_skill_sdk_enrollment.py b/backend/tests/test_skill_sdk_enrollment.py
index 65392bad31..f25089b993 100644
--- a/backend/tests/test_skill_sdk_enrollment.py
+++ b/backend/tests/test_skill_sdk_enrollment.py
@@ -47,6 +47,9 @@ def sdk_home(tmp_path):
     sessions = sessionmaker(engine, expire_on_commit=False)
     with sessions.begin() as session:
         session.add(UserRow(id="owner", email="owner@example.test"))
+    # Release the fixture's pooled SQLite connection before SDK subprocesses
+    # exercise database removal, which Windows forbids while the file is open.
+    engine.dispose()
     repository = SkillMutationRepository(sessions)
     yield tmp_path, config, root, repository
     engine.dispose()
@@ -84,6 +87,7 @@ else:
     return json.loads(result.stdout.splitlines()[-1])
 
 
+@pytest.mark.skipif(os.name != "posix", reason="package capture requires POSIX filesystem primitives")
 @pytest.mark.parametrize(
     "action",
     [
@@ -105,6 +109,7 @@ def test_fresh_sdk_refuses_enrolled_owner_without_gateway_runtime(sdk_home, acti
     assert after.mutation_seq == before.mutation_seq
 
 
+@pytest.mark.skipif(os.name != "posix", reason="package capture requires POSIX filesystem primitives")
 def test_fresh_sdk_global_toggle_cannot_bypass_another_enrolled_owner(sdk_home):
     _, _, root, repository = sdk_home
     repository.observe("owner", "example", capture_package(root).digest, True, exists=True)
diff --git a/backend/tests/test_skill_storage_support_files.py b/backend/tests/test_skill_storage_support_files.py
index 94fbbcdd15..3baacc25fa 100644
--- a/backend/tests/test_skill_storage_support_files.py
+++ b/backend/tests/test_skill_storage_support_files.py
@@ -124,6 +124,7 @@ def _write_literal(path: Path, data: bytes) -> None:
         path.write_bytes(data)
 
 
+@pytest.mark.skipif(os.name == "nt", reason="Windows cannot create reserved AUX device names")
 def test_remove_preexisting_nonportable_support_file(storage, skill_dir):
     """Deletion of a stored non-portable name succeeds; creating one still fails."""
     target = skill_dir / "scripts" / "AUX.py"