@@ -5,7 +5,7 @@
 import json
 import sys
 
-from cuda.pathfinder._dynamic_libs.load_dl_common import LoadedDL
+from cuda.pathfinder._dynamic_libs.load_dl_common import DynamicLibNotFoundError, LoadedDL
 from cuda.pathfinder._utils.platform_aware import IS_WINDOWS
 
 if IS_WINDOWS:
@@ -15,7 +15,10 @@
 
 
 def _probe_canary_abs_path(libname: str) -> str | None:
-    loaded: LoadedDL | None = load_with_system_search(libname)
+    try:
+        loaded: LoadedDL | None = load_with_system_search(libname)
+    except DynamicLibNotFoundError:
+        return None
     if loaded is None:
         return None
     abs_path = loaded.abs_path
 
@@ -78,28 +78,28 @@ def _resolve_system_loaded_abs_path_in_subprocess(libname: str) -> str | None:
     This keeps any side-effects of loading the canary library scoped to the
     child process instead of polluting the current process.
     """
-    try:
-        result = run_in_spawned_child_process(
-            probe_canary_abs_path_and_print_json,
-            args=(libname,),
-            timeout=10.0,
-        )
-    except (OSError, RuntimeError):
-        return None
-    if result.returncode != 0:
-        return None
+    result = run_in_spawned_child_process(
+        probe_canary_abs_path_and_print_json,
+        args=(libname,),
+        timeout=10.0,
+        rethrow=True,
+    )
 
     # Read the final non-empty stdout line in case earlier lines are emitted.
     lines = [line for line in result.stdout.splitlines() if line.strip()]
     if not lines:
-        return None
+        raise RuntimeError(f"Canary probe child process produced no stdout payload for {libname!r}")
     try:
         payload = json.loads(lines[-1])
     except json.JSONDecodeError:
-        return None
+        raise RuntimeError(
+            f"Canary probe child process emitted invalid JSON payload for {libname!r}: {lines[-1]!r}"
+        ) from None
     if isinstance(payload, str):
         return payload
-    return None
+    if payload is None:
+        return None
+    raise RuntimeError(f"Canary probe child process emitted unexpected payload for {libname!r}: {payload!r}")
 
 
 def _try_ctk_root_canary(finder: _FindNvidiaDynamicLib) -> str | None:
 
@@ -13,6 +13,7 @@
 from cuda.pathfinder._dynamic_libs.load_dl_common import LoadedDL
 from cuda.pathfinder._dynamic_libs.load_nvidia_dynamic_lib import (
     _load_lib_no_cache,
+    _resolve_system_loaded_abs_path_in_subprocess,
     _try_ctk_root_canary,
 )
 from cuda.pathfinder._utils.platform_aware import IS_WINDOWS
@@ -140,6 +141,58 @@ def test_try_via_ctk_root_regular_lib(tmp_path):
     assert _FindNvidiaDynamicLib("cudart").try_via_ctk_root(str(ctk_root)) == str(cudart_lib)
 
 
+# ---------------------------------------------------------------------------
+# _resolve_system_loaded_abs_path_in_subprocess
+# ---------------------------------------------------------------------------
+
+
+def test_subprocess_probe_returns_abs_path_on_string_payload(mocker):
+    result = mocker.Mock(stdout='"/usr/local/cuda/lib64/libcudart.so.13"\n')
+    mocker.patch(f"{_MODULE}.run_in_spawned_child_process", return_value=result)
+
+    assert _resolve_system_loaded_abs_path_in_subprocess("cudart") == "/usr/local/cuda/lib64/libcudart.so.13"
+
+
+def test_subprocess_probe_returns_none_on_null_payload(mocker):
+    result = mocker.Mock(stdout="null\n")
+    mocker.patch(f"{_MODULE}.run_in_spawned_child_process", return_value=result)
+
+    assert _resolve_system_loaded_abs_path_in_subprocess("cudart") is None
+
+
+def test_subprocess_probe_raises_on_child_failure(mocker):
+    mocker.patch(
+        f"{_MODULE}.run_in_spawned_child_process",
+        side_effect=ChildProcessError("child failed"),
+    )
+    with pytest.raises(ChildProcessError, match="child failed"):
+        _resolve_system_loaded_abs_path_in_subprocess("cudart")
+
+
+def test_subprocess_probe_raises_on_empty_stdout(mocker):
+    result = mocker.Mock(stdout=" \n \n")
+    mocker.patch(f"{_MODULE}.run_in_spawned_child_process", return_value=result)
+
+    with pytest.raises(RuntimeError, match="produced no stdout payload"):
+        _resolve_system_loaded_abs_path_in_subprocess("cudart")
+
+
+def test_subprocess_probe_raises_on_invalid_json_payload(mocker):
+    result = mocker.Mock(stdout="not-json\n")
+    mocker.patch(f"{_MODULE}.run_in_spawned_child_process", return_value=result)
+
+    with pytest.raises(RuntimeError, match="invalid JSON payload"):
+        _resolve_system_loaded_abs_path_in_subprocess("cudart")
+
+
+def test_subprocess_probe_raises_on_unexpected_json_payload(mocker):
+    result = mocker.Mock(stdout='{"path": "/usr/local/cuda/lib64/libcudart.so.13"}\n')
+    mocker.patch(f"{_MODULE}.run_in_spawned_child_process", return_value=result)
+
+    with pytest.raises(RuntimeError, match="unexpected payload"):
+        _resolve_system_loaded_abs_path_in_subprocess("cudart")
+
+
 # ---------------------------------------------------------------------------
 # _try_ctk_root_canary
 # ---------------------------------------------------------------------------