diff --git a/CHANGELOG.md b/CHANGELOG.md
index f8c67069..17f0d9d5 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -34,6 +34,15 @@ PyPI version — not the changelog header.
 
 ### Fixed
 
+- **Two more non-hermetic ai_mail tests made deterministic (PR659).** With the full
+  suite now running on varied CI runners, `test_get_pid_cwd_darwin_failure` and
+  `test_is_zombie_linux_no_proc` intermittently failed: they called the real `lsof`
+  (via `subprocess.run`) and real `open("/proc/…")` for a fixed PID (999 / 99999),
+  so on a runner where that PID happened to exist they returned a non-`None` result
+  instead of the expected failure. Mocked `subprocess.run` and `builtins.open` so the
+  tests assert the failure contract without touching real process/`/proc` state.
+  Test-only; deterministic across repeated runs.
+
 - **Windows CI cross-platform fixes — `windows-setup` green (PR659).** Fixing the
   telegram collection errors unmasked 14 pre-existing Windows-only failures across
   six branches. Two root causes. **(1) pid-liveness tests** (ai_mail, flow, hooks,
diff --git a/src/aipass/ai_mail/tests/test_wake.py b/src/aipass/ai_mail/tests/test_wake.py
index a36c1a01..00063866 100644
--- a/src/aipass/ai_mail/tests/test_wake.py
+++ b/src/aipass/ai_mail/tests/test_wake.py
@@ -273,6 +273,12 @@ def test_get_pid_cwd_darwin(monkeypatch, tmp_path):
 
 def test_get_pid_cwd_darwin_failure(monkeypatch):
     """macOS: lsof failure returns None."""
+
+    class FailedResult:
+        returncode = 1
+        stdout = ""
+
+    monkeypatch.setattr(subprocess, "run", lambda *a, **kw: FailedResult())
     assert _get_pid_cwd_darwin("999") is None
 
 
@@ -309,6 +315,14 @@ def test_is_zombie_linux_zombie(monkeypatch, tmp_path):
 
 def test_is_zombie_linux_no_proc(monkeypatch):
     """Missing /proc entry returns False (not zombie, just gone)."""
+    _real_open = open
+
+    def _fake_open(path, *a, **kw):
+        if "/proc/99999/" in str(path):
+            raise FileNotFoundError(path)
+        return _real_open(path, *a, **kw)
+
+    monkeypatch.setattr("builtins.open", _fake_open)
     assert _is_zombie_linux(99999) is False