diff --git a/python/lib/sift_client/_tests/pytest_plugin/conftest.py b/python/lib/sift_client/_tests/pytest_plugin/conftest.py
index 783a12bf4..7afee768d 100644
--- a/python/lib/sift_client/_tests/pytest_plugin/conftest.py
+++ b/python/lib/sift_client/_tests/pytest_plugin/conftest.py
@@ -9,13 +9,17 @@
   block inside ``pytest_configure``, useful for inspecting internal state
   without running tests against a real backend
 
-Every test in this suite invokes the inner session via
-``pytester.runpytest_subprocess(...)`` rather than ``pytester.runpytest(...)``.
-``runpytest`` runs the inner pytest in-process, which re-imports the Sift
-plugin on each test; the plugin transitively imports numpy, whose C
-extensions refuse to initialize twice in one process and raise
-``cannot load module more than once per process``. Spawning a subprocess
-gives each inner session a fresh interpreter and sidesteps that guard.
+The offline-log tests (``test_hierarchy.py``, ``test_pass_fail.py``) drive the
+inner session in-process via ``pytester.runpytest_inprocess(...)``. This is
+fast because the outer session already preloads the plugin (``pyproject.toml``
+sets ``addopts = "... -p sift_client.pytest_plugin ..."``), so the numpy C
+extensions the plugin pulls in are imported once for the whole outer process
+and reused by every inner run — no per-test interpreter spawn, and no
+``cannot load module more than once per process`` re-init guard to trip.
+
+Tests that need true process isolation (fresh env vars, credential and
+connection resolution, ini parsing) still use ``pytester.runpytest_subprocess(...)``
+so the inner session starts from a clean interpreter.
 """
 
 from __future__ import annotations
diff --git a/python/lib/sift_client/_tests/pytest_plugin/test_hierarchy.py b/python/lib/sift_client/_tests/pytest_plugin/test_hierarchy.py
index 1efd4e817..9e0dd52e0 100644
--- a/python/lib/sift_client/_tests/pytest_plugin/test_hierarchy.py
+++ b/python/lib/sift_client/_tests/pytest_plugin/test_hierarchy.py
@@ -76,7 +76,7 @@ def test_b(self):
             """
         )
     )
-    result = pytester.runpytest_subprocess("-v")
+    result = pytester.runpytest_inprocess("-v")
     result.assert_outcomes(passed=2)
     steps = capture.load_steps(log_file)
     by_name = _by_name(steps)
@@ -97,7 +97,7 @@ def test_a(self):
             """
         )
     )
-    result = pytester.runpytest_subprocess("-v")
+    result = pytester.runpytest_inprocess("-v")
     result.assert_outcomes(passed=1)
     steps = capture.load_steps(log_file)
     by_name = _by_name(steps)
@@ -125,7 +125,7 @@ def test_a(self, v):
             """
         )
     )
-    result = pytester.runpytest_subprocess("-v")
+    result = pytester.runpytest_inprocess("-v")
     result.assert_outcomes(passed=2)
     steps = capture.load_steps(log_file)
     by_name = _by_name(steps)
@@ -150,7 +150,7 @@ def test_y(self):
             """
         )
     )
-    result = pytester.runpytest_subprocess("-v")
+    result = pytester.runpytest_inprocess("-v")
     result.assert_outcomes(passed=2)
     steps = capture.load_steps(log_file)
     by_name = _by_name(steps)
@@ -175,7 +175,7 @@ def test_free():
             """
         )
     )
-    result = pytester.runpytest_subprocess("-v")
+    result = pytester.runpytest_inprocess("-v")
     result.assert_outcomes(passed=2)
     steps = capture.load_steps(log_file)
     by_name = _by_name(steps)
@@ -205,7 +205,7 @@ def test_b(self):
             """
         )
     )
-    result = pytester.runpytest_subprocess("-v")
+    result = pytester.runpytest_inprocess("-v")
     result.assert_outcomes(passed=2)
     steps = capture.load_steps(log_file)
     by_name = _by_name(steps)
@@ -230,7 +230,7 @@ def test_b(self):
             """
         )
     )
-    result = pytester.runpytest_subprocess("-v")
+    result = pytester.runpytest_inprocess("-v")
     result.assert_outcomes(passed=2)
     steps = capture.load_steps(log_file)
     by_name = _by_name(steps)
@@ -252,7 +252,7 @@ def test_a(self):
             '''
         )
     )
-    result = pytester.runpytest_subprocess("-v")
+    result = pytester.runpytest_inprocess("-v")
     result.assert_outcomes(passed=1)
     steps = capture.load_steps(log_file)
     by_name = _by_name(steps)
@@ -284,7 +284,7 @@ def test_y(self, w):
             """
         )
     )
-    result = pytester.runpytest_subprocess("-v")
+    result = pytester.runpytest_inprocess("-v")
     result.assert_outcomes(passed=2)
     steps = capture.load_steps(log_file)
     by_name = _by_name(steps)
@@ -396,7 +396,7 @@ def test_c(self):
             """
         )
     )
-    result = pytester.runpytest_subprocess("-v")
+    result = pytester.runpytest_inprocess("-v")
     result.assert_outcomes(passed=2, failed=1)
     steps = capture.load_steps(log_file)
     by_name = _by_name(steps)
@@ -434,7 +434,7 @@ def test_b(self):
             """
         )
     )
-    result = pytester.runpytest_subprocess("-v")
+    result = pytester.runpytest_inprocess("-v")
     result.assert_outcomes(passed=2, failed=1)
     steps = capture.load_steps(log_file)
     by_name = _by_name(steps)
@@ -476,7 +476,7 @@ def test_b(self):
             """
         )
     )
-    result = pytester.runpytest_subprocess("-v")
+    result = pytester.runpytest_inprocess("-v")
     result.assert_outcomes(passed=2)
     steps = capture.load_steps(log_file)
     by_name = _by_name(steps)
@@ -499,7 +499,7 @@ def test_a(self):
             """
         )
     )
-    result = pytester.runpytest_subprocess("-v")
+    result = pytester.runpytest_inprocess("-v")
     result.assert_outcomes(passed=1)
     steps = capture.load_steps(log_file)
     by_name = _by_name(steps)
@@ -524,7 +524,7 @@ def test_a(v):
             """
         )
     )
-    result = pytester.runpytest_subprocess("-v")
+    result = pytester.runpytest_inprocess("-v")
     result.assert_outcomes(passed=2)
     steps = capture.load_steps(log_file)
     by_name = _by_name(steps)
@@ -565,7 +565,7 @@ def test_y(self):
             """
         ),
     )
-    result = pytester.runpytest_subprocess("-v")
+    result = pytester.runpytest_inprocess("-v")
     result.assert_outcomes(passed=2)
     steps = capture.load_steps(log_file)
     by_name = _by_name(steps)
@@ -593,7 +593,7 @@ def test_one():
             """
         )
     )
-    result = pytester.runpytest_subprocess("-v")
+    result = pytester.runpytest_inprocess("-v")
     result.assert_outcomes(passed=1)
     steps = capture.load_steps(log_file)
     by_name = _by_name(steps)
@@ -637,7 +637,7 @@ def test_two():
     )
     # ``importlib`` import mode is required so two packages with the same
     # name on disk don't collide during sys.path-based import.
-    result = pytester.runpytest_subprocess("-v", "--import-mode=importlib")
+    result = pytester.runpytest_inprocess("-v", "--import-mode=importlib")
     result.assert_outcomes(passed=2)
     steps = capture.load_steps(log_file)
     by_name = _by_name(steps)
@@ -666,7 +666,7 @@ def test_one():
             """
         )
     )
-    result = pytester.runpytest_subprocess("-v")
+    result = pytester.runpytest_inprocess("-v")
     result.assert_outcomes(passed=1)
     steps = capture.load_steps(log_file)
     by_name = _by_name(steps)
@@ -697,7 +697,7 @@ def test_a(self, v):
             """
         )
     )
-    result = pytester.runpytest_subprocess("-v")
+    result = pytester.runpytest_inprocess("-v")
     result.assert_outcomes(passed=2)
     steps = capture.load_steps(log_file)
     by_name = _by_name(steps)
@@ -730,7 +730,7 @@ def test_rail(v):
             """
         )
     )
-    result = pytester.runpytest_subprocess("-v")
+    result = pytester.runpytest_inprocess("-v")
     result.assert_outcomes(passed=2)
     steps = capture.load_steps(log_file)
     by_name = _by_name(steps)
@@ -759,7 +759,7 @@ def test_iso(voltage, component):
             """
         )
     )
-    result = pytester.runpytest_subprocess("-v")
+    result = pytester.runpytest_inprocess("-v")
     result.assert_outcomes(passed=4)
     steps = capture.load_steps(log_file)
     by_name = _by_name(steps)
@@ -798,7 +798,7 @@ def test_widget(widget):
             """
         )
     )
-    result = pytester.runpytest_subprocess("-v")
+    result = pytester.runpytest_inprocess("-v")
     result.assert_outcomes(passed=2)
     steps = capture.load_steps(log_file)
     by_name = _by_name(steps)
@@ -831,7 +831,7 @@ def test_two(w):
             """
         ),
     )
-    result = pytester.runpytest_subprocess("-v")
+    result = pytester.runpytest_inprocess("-v")
     result.assert_outcomes(passed=4)
     steps = capture.load_steps(log_file)
     by_name = _by_name(steps)
@@ -855,7 +855,7 @@ def test_chain(a, b):
             """
         )
     )
-    result = pytester.runpytest_subprocess("-v")
+    result = pytester.runpytest_inprocess("-v")
     result.assert_outcomes(passed=1)
     steps = capture.load_steps(log_file)
     leaf = next(s for s in steps if s["name"].startswith("b="))