diff --git a/tests/test_clink_codex_agent.py b/tests/test_clink_codex_agent.py
index e788ea6..cdee3cd 100644
--- a/tests/test_clink_codex_agent.py
+++ b/tests/test_clink_codex_agent.py
@@ -1,4 +1,5 @@
 import asyncio
+import shutil
 from pathlib import Path
 
 import pytest
@@ -41,7 +42,11 @@ async def _run_agent_with_process(monkeypatch, agent, role, process):
     async def fake_create_subprocess_exec(*_args, **_kwargs):
         return process
 
+    def fake_which(executable_name):
+        return f"/usr/bin/{executable_name}"
+
     monkeypatch.setattr(asyncio, "create_subprocess_exec", fake_create_subprocess_exec)
+    monkeypatch.setattr(shutil, "which", fake_which)
     return await agent.run(role=role, prompt="do something", files=[], images=[])
 
 
diff --git a/tests/test_clink_gemini_agent.py b/tests/test_clink_gemini_agent.py
index e67ff2d..9165684 100644
--- a/tests/test_clink_gemini_agent.py
+++ b/tests/test_clink_gemini_agent.py
@@ -1,4 +1,5 @@
 import asyncio
+import shutil
 from pathlib import Path
 
 import pytest
@@ -41,7 +42,11 @@ async def _run_agent_with_process(monkeypatch, agent, role, process):
     async def fake_create_subprocess_exec(*_args, **_kwargs):
         return process
 
+    def fake_which(executable_name):
+        return f"/usr/bin/{executable_name}"
+
     monkeypatch.setattr(asyncio, "create_subprocess_exec", fake_create_subprocess_exec)
+    monkeypatch.setattr(shutil, "which", fake_which)
     return await agent.run(role=role, prompt="do something", files=[], images=[])