fix(edit): make the test-weakening guard opt-in

src/lemoncrow/gateway/adapters/mcp_server.py

@@ -7023,8 +7023,9 @@ def _looks_like_test_path(path: str) -> bool:
 # fixing the code. We trip ONLY on that signal -- additive edits (new tests or
 # assertions) and in-place assertion modifications pass freely. Heuristic and
 # language-fuzzy by design: it errs toward allowing, surfacing a counterexample +
-# rollback only on a clear net assertion-removal or skip/xfail addition. Operator
-# off-switch: LEMONCROW_TEST_CONTRACT_GUARD=0.
+# rollback only on a clear net assertion-removal or skip/xfail addition. Off by
+# default (it blocked legitimate test-only cleanup); opt in with
+# LEMONCROW_TEST_CONTRACT_GUARD=1.
 _ASSERTION_RE = re.compile(r"\bassert|\bexpect\s*\(|\bEXPECT_|\bASSERT_|\.should\b")
 _SKIP_XFAIL_RE = re.compile(
     r"@(?:pytest\.mark\.)?(?:skip|skipif|xfail)\b|@unittest\.skip|\bt\.Skip[a-zA-Z]*\("
@@ -7033,8 +7034,8 @@ def _looks_like_test_path(path: str) -> bool:
 
 
 def _test_contract_guard_enabled() -> bool:
-    """Whether the test-weakening guard runs (operator off-switch, default on)."""
-    return os.environ.get("LEMONCROW_TEST_CONTRACT_GUARD", "").strip().lower() not in ("0", "false", "no", "off")
+    """Whether the test-weakening guard runs (operator opt-in, default off)."""
+    return os.environ.get("LEMONCROW_TEST_CONTRACT_GUARD", "").strip().lower() in ("1", "true", "yes", "on")
 
 
 def _classify_test_weakening(old_content: str, new_content: str) -> str | None:

tests/gateway/cli/test_runtime.py

@@ -168,6 +168,7 @@ def test_owned_edit_blocks_test_weakening(tmp_path, monkeypatch) -> None:
     # The owned runtime no longer publishes a self-authorize bypass; an edit that
     # WEAKENS a test (removes an assertion) is rolled back by the detector.
     monkeypatch.setenv("CLAUDE_WORKSPACE_ROOT", str(tmp_path))
+    monkeypatch.setenv("LEMONCROW_TEST_CONTRACT_GUARD", "1")
     target = tmp_path / "tests" / "test_contract.py"
     target.parent.mkdir()
     target.write_text("def test_x():\n    assert value == 'old'\n    assert other == 1\n", encoding="utf-8")

tests/gateway/test_mcp_tool_handlers.py

@@ -1367,6 +1367,7 @@ def test_smart_edit_blocks_test_assertion_removal(
     # roll back and surface a counterexample (the detector trips only on weakening).
     _ = store_root
     monkeypatch.chdir(tmp_path)
+    monkeypatch.setenv("LEMONCROW_TEST_CONTRACT_GUARD", "1")
     target = Path("tests/test_parser.py")
     target.parent.mkdir()
     target.write_text("def test_x():\n    assert compute() == 5\n    assert other() == 9\n", encoding="utf-8")
@@ -1396,11 +1397,43 @@ def test_smart_edit_blocks_test_assertion_removal(
     assert "assert compute() == 5" in target.read_text(encoding="utf-8")
 
 
+def test_smart_edit_test_contract_guard_off_by_default(
+    store_root: Path, tmp_path: Path, monkeypatch: pytest.MonkeyPatch
+) -> None:
+    _ = store_root
+    monkeypatch.chdir(tmp_path)
+    monkeypatch.delenv("LEMONCROW_TEST_CONTRACT_GUARD", raising=False)
+    target = Path("tests/test_parser.py")
+    target.parent.mkdir()
+    target.write_text("def test_x():\n    assert compute() == 5\n    assert other() == 9\n", encoding="utf-8")
+
+    payload = _result(
+        _call(
+            "edit",
+            {
+                "edits": [
+                    {
+                        "file_path": str(target),
+                        "old_string": "    assert compute() == 5\n    assert other() == 9\n",
+                        "new_string": "    assert other() == 9\n",
+                    }
+                ],
+                "post_edit_hooks": False,
+            },
+        )
+    )
+
+    assert payload.get("rolled_back") is not True
+    assert "test_weakening" not in payload
+    assert "assert compute() == 5" not in target.read_text(encoding="utf-8")
+
+
 def test_smart_edit_blocks_test_skip_addition(
     store_root: Path, tmp_path: Path, monkeypatch: pytest.MonkeyPatch
 ) -> None:
     _ = store_root
     monkeypatch.chdir(tmp_path)
+    monkeypatch.setenv("LEMONCROW_TEST_CONTRACT_GUARD", "1")
     target = Path("tests/test_parser.py")
     target.parent.mkdir()
     target.write_text("def test_x():\n    assert compute() == 5\n", encoding="utf-8")
@@ -1432,6 +1465,7 @@ def test_smart_edit_allows_additive_test_edit(
     # Adding a new assertion to an existing test passes freely -- no friction.
     _ = store_root
     monkeypatch.chdir(tmp_path)
+    monkeypatch.setenv("LEMONCROW_TEST_CONTRACT_GUARD", "1")
     target = Path("tests/test_parser.py")
     target.parent.mkdir()
     target.write_text("def test_x():\n    assert compute() == 5\n", encoding="utf-8")
@@ -1464,6 +1498,7 @@ def test_smart_edit_allows_assertion_value_change(
     # assertions and passes -- the detector guards removal/skip, not value edits.
     _ = store_root
     monkeypatch.chdir(tmp_path)
+    monkeypatch.setenv("LEMONCROW_TEST_CONTRACT_GUARD", "1")
     target = Path("tests/test_parser.py")
     target.parent.mkdir()
     target.write_text("def test_x():\n    assert compute() == 5\n", encoding="utf-8")
@@ -1496,6 +1531,7 @@ def test_smart_edit_allows_test_weakening_paired_with_production_change(
     # as a genuine refactor (contract moved with the code), not a reward-hack.
     _ = store_root
     monkeypatch.chdir(tmp_path)
+    monkeypatch.setenv("LEMONCROW_TEST_CONTRACT_GUARD", "1")
     test_file = Path("tests/test_parser.py")
     test_file.parent.mkdir()
     test_file.write_text("def test_x():\n    assert compute() == 5\n    assert other() == 9\n", encoding="utf-8")