feat: auto-install missing agent deps on startup (#215)

* feat: auto-install missing agent deps on startup

* fix: patch HERMES_HOME in test_skips_when_agent_dir_missing to prevent real agent fallback

The test patched HERMES_WEBUI_AGENT_DIR to a nonexistent path but left
HERMES_HOME unpatched. In the full test suite HERMES_HOME resolves to the
real hermes agent dir, causing the fallback in _agent_dir() to find and
use it — making auto_install_agent_deps() call pip instead of returning
False. Fix: also patch HERMES_HOME to a nonexistent dir in env_overrides.

---------

Co-authored-by: Nathan Esquenazi <nesquena@gmail.com>

tests/test_sprint32.py

@@ -0,0 +1,71 @@
+from pathlib import Path
+from unittest.mock import MagicMock, patch
+import subprocess
+from api.startup import auto_install_agent_deps
+
+class TestAutoInstallAgentDeps:
+    def test_installs_from_requirements_txt(self, tmp_path):
+        agent_dir = tmp_path / 'hermes-agent'
+        agent_dir.mkdir()
+        req = agent_dir / 'requirements.txt'
+        req.write_text('pyyaml\n')
+        with patch.dict('os.environ', {'HERMES_WEBUI_AGENT_DIR': str(agent_dir)}, clear=False):
+            with patch('subprocess.run') as mock_run:
+                mock_run.return_value = MagicMock(returncode=0, stderr='')
+                assert auto_install_agent_deps() is True
+                args = mock_run.call_args[0][0]
+                assert '-r' in args and str(req) in args
+
+    def test_falls_back_to_pyproject(self, tmp_path):
+        agent_dir = tmp_path / 'hermes-agent'
+        agent_dir.mkdir()
+        (agent_dir / 'pyproject.toml').write_text('[project]\nname="hermes-agent"\n')
+        with patch.dict('os.environ', {'HERMES_WEBUI_AGENT_DIR': str(agent_dir)}, clear=False):
+            with patch('subprocess.run') as mock_run:
+                mock_run.return_value = MagicMock(returncode=0, stderr='')
+                assert auto_install_agent_deps() is True
+                args = mock_run.call_args[0][0]
+                assert str(agent_dir) in args and '-r' not in args
+
+    def test_skips_when_agent_dir_missing(self, tmp_path, capsys):
+        missing = tmp_path / 'nonexistent-agent'
+        # Patch both HERMES_WEBUI_AGENT_DIR and HERMES_HOME so the fallback
+        # path (HERMES_HOME/hermes-agent) also resolves to a nonexistent dir,
+        # preventing the real agent dir from being found in the test environment.
+        env_overrides = {
+            'HERMES_WEBUI_AGENT_DIR': str(missing),
+            'HERMES_HOME': str(tmp_path / 'no-hermes-home'),
+        }
+        with patch.dict('os.environ', env_overrides, clear=False):
+            with patch('subprocess.run') as mock_run:
+                assert auto_install_agent_deps() is False
+                assert not mock_run.called
+        assert 'skipped' in capsys.readouterr().out.lower()
+
+    def test_skips_when_no_install_file(self, tmp_path, capsys):
+        agent_dir = tmp_path / 'hermes-agent'
+        agent_dir.mkdir()
+        with patch.dict('os.environ', {'HERMES_WEBUI_AGENT_DIR': str(agent_dir)}, clear=False):
+            with patch('subprocess.run') as mock_run:
+                assert auto_install_agent_deps() is False
+                assert not mock_run.called
+        assert 'skipped' in capsys.readouterr().out.lower()
+
+    def test_tolerates_pip_failure(self, tmp_path, capsys):
+        agent_dir = tmp_path / 'hermes-agent'
+        agent_dir.mkdir()
+        (agent_dir / 'requirements.txt').write_text('somepkg\n')
+        with patch.dict('os.environ', {'HERMES_WEBUI_AGENT_DIR': str(agent_dir)}, clear=False):
+            with patch('subprocess.run') as mock_run:
+                mock_run.return_value = MagicMock(returncode=1, stderr='ERROR: could not find package')
+                assert auto_install_agent_deps() is False
+        assert 'failed' in capsys.readouterr().out.lower() or 'pip' in capsys.readouterr().out.lower()
+
+    def test_tolerates_timeout(self, tmp_path, capsys):
+        agent_dir = tmp_path / 'hermes-agent'
+        agent_dir.mkdir()
+        (agent_dir / 'requirements.txt').write_text('somepkg\n')
+        with patch.dict('os.environ', {'HERMES_WEBUI_AGENT_DIR': str(agent_dir)}, clear=False):
+            with patch('subprocess.run', side_effect=subprocess.TimeoutExpired('pip', 120)):
+                assert auto_install_agent_deps() is False
+        assert 'timed out' in capsys.readouterr().out.lower()