diff --git a/tests/agent/test_context_compressor.py b/tests/agent/test_context_compressor.py
index d8691fdf87c..dca10bb4462 100644
--- a/tests/agent/test_context_compressor.py
+++ b/tests/agent/test_context_compressor.py
@@ -65,11 +65,11 @@ class TestCompress:
         assert result == msgs
 
     def test_truncation_fallback_no_client(self, compressor):
-        # compressor has client=None and abort_on_summary_failure=False (default),
-        # so the LEGACY fallback path inserts a static "summary unavailable"
-        # placeholder and the middle window is dropped.
+        # Simulate "no summarizer available" explicitly. call_llm can otherwise
+        # discover the developer's real auxiliary credentials from auth state.
         msgs = [{"role": "system", "content": "System prompt"}] + self._make_messages(10)
-        result = compressor.compress(msgs)
+        with patch("agent.context_compressor.call_llm", side_effect=RuntimeError("no provider")):
+            result = compressor.compress(msgs)
         assert len(result) < len(msgs)
         # Should keep system message and last N
         assert result[0]["role"] == "system"
diff --git a/tests/conftest.py b/tests/conftest.py
index 3cdce42c495..0514702546b 100644
--- a/tests/conftest.py
+++ b/tests/conftest.py
@@ -358,6 +358,10 @@ def _hermetic_environment(tmp_path, monkeypatch):
     monkeypatch.setenv("AWS_EC2_METADATA_DISABLED", "true")
     monkeypatch.setenv("AWS_METADATA_SERVICE_TIMEOUT", "1")
     monkeypatch.setenv("AWS_METADATA_SERVICE_NUM_ATTEMPTS", "1")
+    # Tirith auto-installs from GitHub when enabled and missing. Unit tests
+    # should never perform that implicit network/bootstrap path; Tirith-specific
+    # tests opt back in by patching the security config directly.
+    monkeypatch.setenv("TIRITH_ENABLED", "false")
 
     # 5. Reset plugin singleton so tests don't leak plugins from
     #    ~/.hermes/plugins/ (which, per step 3, is now empty — but the
diff --git a/tests/gateway/test_runner_startup_failures.py b/tests/gateway/test_runner_startup_failures.py
index 438553f34ed..b82062e4090 100644
--- a/tests/gateway/test_runner_startup_failures.py
+++ b/tests/gateway/test_runner_startup_failures.py
@@ -207,6 +207,7 @@ async def test_start_gateway_replace_force_uses_terminate_pid(monkeypatch, tmp_p
         lambda **kwargs: 0,
     )
     monkeypatch.setattr("gateway.status.terminate_pid", lambda pid, force=False: calls.append((pid, force)))
+    monkeypatch.setattr("gateway.status._pid_exists", lambda pid: True)
     monkeypatch.setattr("gateway.run.os.getpid", lambda: 100)
     monkeypatch.setattr("gateway.run.os.kill", lambda pid, sig: None)
     monkeypatch.setattr("time.sleep", lambda _: None)
diff --git a/tests/tools/test_tirith_security.py b/tests/tools/test_tirith_security.py
index b47c7a5ff58..6c771c6d482 100644
--- a/tests/tools/test_tirith_security.py
+++ b/tests/tools/test_tirith_security.py
@@ -831,7 +831,8 @@ class TestDiskFailureMarker:
         with patch("tools.tirith_security._failure_marker_path", return_value=marker):
             from tools.tirith_security import _mark_install_failed, _is_install_failed_on_disk
             _mark_install_failed("cosign_missing")
-            assert _is_install_failed_on_disk()  # cosign still absent
+            with patch("tools.tirith_security.shutil.which", return_value=None):
+                assert _is_install_failed_on_disk()  # cosign still absent
 
             # Now cosign appears on PATH
             with patch("tools.tirith_security.shutil.which", return_value="/usr/local/bin/cosign"):
diff --git a/tests/tools/test_voice_mode.py b/tests/tools/test_voice_mode.py
index 4c7ba74bd6e..3f7ada8c4a2 100644
--- a/tests/tools/test_voice_mode.py
+++ b/tests/tools/test_voice_mode.py
@@ -10,6 +10,18 @@ from unittest.mock import MagicMock, patch
 import pytest
 
 
+def _non_wsl_proc_version(real_open):
+    """Return an open() shim that makes host WSL detection deterministic."""
+    def _fake_open(file, *args, **kwargs):
+        if file == "/proc/version":
+            from io import StringIO
+
+            return StringIO("Linux test-kernel")
+        return real_open(file, *args, **kwargs)
+
+    return _fake_open
+
+
 # ============================================================================
 # Fixtures
 # ============================================================================
@@ -68,6 +80,7 @@ class TestDetectAudioEnvironment:
         monkeypatch.delenv("SSH_CONNECTION", raising=False)
         monkeypatch.setattr("tools.voice_mode._import_audio",
                             lambda: (MagicMock(), MagicMock()))
+        monkeypatch.setattr("builtins.open", _non_wsl_proc_version(open))
 
         from tools.voice_mode import detect_audio_environment
         result = detect_audio_environment()
@@ -225,6 +238,7 @@ class TestDetectAudioEnvironment:
         monkeypatch.setattr("tools.voice_mode.shutil.which", lambda cmd: "/data/data/com.termux/files/usr/bin/termux-microphone-record" if cmd == "termux-microphone-record" else None)
         monkeypatch.setattr("tools.voice_mode._termux_api_app_installed", lambda: True)
         monkeypatch.setattr("tools.voice_mode._import_audio", lambda: (_ for _ in ()).throw(ImportError("no audio libs")))
+        monkeypatch.setattr("builtins.open", _non_wsl_proc_version(open))
 
         from tools.voice_mode import detect_audio_environment
         result = detect_audio_environment()