diff --git a/clink/agents/base.py b/clink/agents/base.py
index fface9c..4d821c3 100644
--- a/clink/agents/base.py
+++ b/clink/agents/base.py
@@ -6,6 +6,7 @@ import asyncio
 import logging
 import os
 import shlex
+import shutil
 import tempfile
 import time
 from collections.abc import Sequence
@@ -65,6 +66,17 @@ class BaseCLIAgent:
         # The runner simply executes the configured CLI command for the selected role.
         command = self._build_command(role=role)
         env = self._build_environment()
+
+        # Resolve executable path for cross-platform compatibility (especially Windows)
+        executable_name = command[0]
+        resolved_executable = shutil.which(executable_name)
+        if resolved_executable is None:
+            raise CLIAgentError(
+                f"Executable '{executable_name}' not found in PATH for CLI '{self.client.name}'. "
+                f"Ensure the command is installed and accessible."
+            )
+        command[0] = resolved_executable
+
         sanitized_command = list(command)
 
         cwd = str(self.client.working_dir) if self.client.working_dir else None
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=[])