diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index e5a74ee..ef1ae00 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -11,6 +11,9 @@ permissions:
 jobs:
   checks:
     runs-on: ubuntu-latest
+    env:
+      # uv run re-syncs to the lockfile's default extras unless told not to; it removed the extras below before pytest.
+      UV_NO_SYNC: "1"
     steps:
       - uses: actions/checkout@v5
       - uses: astral-sh/setup-uv@v7
@@ -19,7 +22,7 @@ jobs:
       - uses: actions/setup-python@v6
         with:
           python-version-file: .python-version
-      - run: uv sync --group dev
+      - run: uv sync --group dev --extra hunt --extra semantic
       - run: uv run ruff format --check .
       - run: uv run ruff check .
       - run: uv run mypy src/openultrasast
diff --git a/tests/test_engine_trace.py b/tests/test_engine_trace.py
index 722e9c2..e95d1a9 100644
--- a/tests/test_engine_trace.py
+++ b/tests/test_engine_trace.py
@@ -4,6 +4,7 @@ from __future__ import annotations
 
 import importlib.util
 import json
+import os
 import subprocess
 import sys
 from collections import Counter
@@ -28,6 +29,21 @@ with pytest.MonkeyPatch.context() as patch:
 worker = sys.modules["engine_trace_worker"]
 
 
+@pytest.fixture(autouse=True)
+def _main_env_does_not_outlive_the_test():
+    """engine_trace.main pins GIT_NO_LAZY_FETCH for its own run; the variable must not leak into later tests.
+
+    Git 2.44 and newer honour it, and the partial-clone extraction test then fails on a refusal that has nothing
+    to do with extraction (seen in CI; the local git ignores the variable, so the leak was invisible here).
+    monkeypatch.delenv records nothing for an absent variable, so the restore is explicit."""
+    before = os.environ.get("GIT_NO_LAZY_FETCH")
+    yield
+    if before is None:
+        os.environ.pop("GIT_NO_LAZY_FETCH", None)
+    else:
+        os.environ["GIT_NO_LAZY_FETCH"] = before
+
+
 def row(**extra):
     return {
         "sink": "os.system(cmd)",