refactor(agent-loop): remove tmux, run claude directly via Popen (#120)

Replace the tmux-based agent launcher with a direct subprocess.Popen
call. Claude sessions can't be attached to anyway, so the tmux layer
added complexity with no benefit. State now tracks a PID instead of a
tmux session name; liveness is checked with os.kill(pid, 0).

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

scripts/test_agent_loop.py

@@ -0,0 +1,132 @@
+#!/usr/bin/env python3
+"""Tests for agent_loop.py."""
+import io
+import json
+import os
+import tempfile
+import unittest
+from pathlib import Path
+from unittest.mock import MagicMock, patch
+
+import sys
+sys.path.insert(0, str(Path(__file__).parent))
+
+import agent_loop
+
+
+class TestStateFile(unittest.TestCase):
+    def setUp(self):
+        self._tmp = tempfile.NamedTemporaryFile(delete=False, suffix=".json")
+        self._tmp.close()
+        self._orig = agent_loop.STATE_FILE
+        agent_loop.STATE_FILE = Path(self._tmp.name)
+        Path(self._tmp.name).unlink()  # Start with no state file.
+
+    def tearDown(self):
+        agent_loop.STATE_FILE = self._orig
+        Path(self._tmp.name).unlink(missing_ok=True)
+
+    def test_write_state_stores_pid(self):
+        agent_loop._write_state(12345, 91, "issue")
+        data = json.loads(Path(self._tmp.name).read_text())
+        self.assertEqual(data["pid"], 12345)
+        self.assertNotIn("tmux_session", data)
+
+    def test_write_state_stores_issue_and_kind(self):
+        agent_loop._write_state(99, 7, "ci-fix")
+        data = json.loads(Path(self._tmp.name).read_text())
+        self.assertEqual(data["issue"], 7)
+        self.assertEqual(data["type"], "ci-fix")
+        self.assertIn("started_at", data)
+
+    def test_read_state_returns_none_when_missing(self):
+        self.assertIsNone(agent_loop._read_state())
+
+    def test_read_and_write_roundtrip(self):
+        agent_loop._write_state(42, 10, "issue")
+        state = agent_loop._read_state()
+        self.assertIsNotNone(state)
+        self.assertEqual(state["pid"], 42)
+        self.assertEqual(state["issue"], 10)
+
+    def test_clear_state_removes_file(self):
+        agent_loop._write_state(1, None, "ci-fix")
+        agent_loop._clear_state()
+        self.assertIsNone(agent_loop._read_state())
+
+
+class TestAgentAlive(unittest.TestCase):
+    def test_own_pid_is_alive(self):
+        self.assertTrue(agent_loop._agent_alive({"pid": os.getpid()}))
+
+    def test_nonexistent_pid_is_dead(self):
+        self.assertFalse(agent_loop._agent_alive({"pid": 999999999}))
+
+    def test_missing_pid_returns_false(self):
+        self.assertFalse(agent_loop._agent_alive({}))
+        self.assertFalse(agent_loop._agent_alive({"pid": None}))
+
+
+class TestKillAgent(unittest.TestCase):
+    def test_kill_sends_sigkill(self):
+        with patch("agent_loop.os.kill") as mock_kill:
+            agent_loop._kill_agent({"pid": 1234})
+            mock_kill.assert_called_once_with(1234, 9)
+
+    def test_kill_ignores_missing_process(self):
+        with patch("agent_loop.os.kill", side_effect=ProcessLookupError):
+            agent_loop._kill_agent({"pid": 1234})  # Should not raise.
+
+    def test_kill_noop_when_no_pid(self):
+        with patch("agent_loop.os.kill") as mock_kill:
+            agent_loop._kill_agent({})
+            mock_kill.assert_not_called()
+
+
+class TestStartAgent(unittest.TestCase):
+    def _make_mock_proc(self, pid=42):
+        proc = MagicMock()
+        proc.pid = pid
+        proc.stdin = io.BytesIO()
+        return proc
+
+    def test_start_agent_returns_pid(self):
+        mock_proc = self._make_mock_proc(pid=42)
+        with tempfile.TemporaryDirectory() as tmpdir:
+            with patch("agent_loop.subprocess.Popen", return_value=mock_proc):
+                with patch.object(agent_loop.Path, "home", return_value=Path(tmpdir)):
+                    result = agent_loop._start_agent("do something", "issue-99")
+        self.assertEqual(result, 42)
+
+    def test_start_agent_uses_popen_not_tmux(self):
+        mock_proc = self._make_mock_proc(pid=7)
+        with tempfile.TemporaryDirectory() as tmpdir:
+            with patch("agent_loop.subprocess.Popen", return_value=mock_proc) as mock_popen:
+                with patch("agent_loop.subprocess.run") as mock_run:
+                    with patch.object(agent_loop.Path, "home", return_value=Path(tmpdir)):
+                        agent_loop._start_agent("prompt", "ci-fix")
+            mock_popen.assert_called_once()
+            mock_run.assert_not_called()
+
+    def test_start_agent_passes_session_name_to_claude(self):
+        mock_proc = self._make_mock_proc(pid=7)
+        with tempfile.TemporaryDirectory() as tmpdir:
+            with patch("agent_loop.subprocess.Popen", return_value=mock_proc) as mock_popen:
+                with patch.object(agent_loop.Path, "home", return_value=Path(tmpdir)):
+                    agent_loop._start_agent("prompt", "issue-55")
+            cmd = mock_popen.call_args[0][0]
+            self.assertIn("issue-55", cmd)
+            self.assertIn("claude", cmd[0])
+
+    def test_start_agent_uses_start_new_session(self):
+        mock_proc = self._make_mock_proc(pid=7)
+        with tempfile.TemporaryDirectory() as tmpdir:
+            with patch("agent_loop.subprocess.Popen", return_value=mock_proc) as mock_popen:
+                with patch.object(agent_loop.Path, "home", return_value=Path(tmpdir)):
+                    agent_loop._start_agent("prompt", "issue-55")
+            kwargs = mock_popen.call_args[1]
+            self.assertTrue(kwargs.get("start_new_session"))
+
+
+if __name__ == "__main__":
+    unittest.main()