feat(nix): container-aware CLI — auto-route all subcommands into managed container

When container.enable = true, the host `hermes` CLI transparently execs
every subcommand into the managed Docker/Podman container. A symlink
bridge (~/.hermes -> /var/lib/hermes/.hermes) unifies state between host
and container so sessions, config, and memories are shared.

CLI changes:
- Global routing before subcommand dispatch (all commands forwarded)
- docker exec with -u exec_user, env passthrough (TERM, COLORTERM,
  LANG, LC_ALL), TTY-aware flags
- Retry with spinner on failure (TTY: 5s, non-TTY: 10s silent)
- Hard fail instead of silent fallback
- HERMES_DEV=1 env var bypasses routing for development
- No routing messages (invisible to user)

NixOS module changes:
- container.hostUsers option: lists users who get ~/.hermes symlink
  and automatic hermes group membership
- Activation script creates symlink bridge (with backup of existing
  ~/.hermes dirs), writes exec_user to .container-mode
- Cleanup on disable: removes symlinks + .container-mode + stops service
- Warning when hostUsers set without addToSystemPackages

tests/hermes_cli/test_container_aware_cli.py

@@ -0,0 +1,354 @@
+"""Tests for container-aware CLI routing (NixOS container mode).
+
+When container.enable = true in the NixOS module, the activation script
+writes a .container-mode metadata file. The host CLI detects this and
+execs into the container instead of running locally.
+"""
+import os
+from pathlib import Path
+from unittest.mock import MagicMock, patch
+
+import pytest
+
+from hermes_cli.config import (
+    _is_inside_container,
+    get_container_exec_info,
+)
+
+
+# =============================================================================
+# _is_inside_container
+# =============================================================================
+
+
+def test_is_inside_container_dockerenv():
+    """Detects /.dockerenv marker file."""
+    with patch("os.path.exists") as mock_exists:
+        mock_exists.side_effect = lambda p: p == "/.dockerenv"
+        assert _is_inside_container() is True
+
+
+def test_is_inside_container_containerenv():
+    """Detects Podman's /run/.containerenv marker."""
+    with patch("os.path.exists") as mock_exists:
+        mock_exists.side_effect = lambda p: p == "/run/.containerenv"
+        assert _is_inside_container() is True
+
+
+def test_is_inside_container_cgroup_docker():
+    """Detects 'docker' in /proc/1/cgroup."""
+    with patch("os.path.exists", return_value=False), \
+         patch("builtins.open", create=True) as mock_open:
+        mock_open.return_value.__enter__ = lambda s: s
+        mock_open.return_value.__exit__ = MagicMock(return_value=False)
+        mock_open.return_value.read = MagicMock(
+            return_value="12:memory:/docker/abc123\n"
+        )
+        assert _is_inside_container() is True
+
+
+def test_is_inside_container_false_on_host():
+    """Returns False when none of the container indicators are present."""
+    with patch("os.path.exists", return_value=False), \
+         patch("builtins.open", side_effect=OSError("no such file")):
+        assert _is_inside_container() is False
+
+
+# =============================================================================
+# get_container_exec_info
+# =============================================================================
+
+
+@pytest.fixture
+def container_env(tmp_path, monkeypatch):
+    """Set up a fake HERMES_HOME with .container-mode file."""
+    hermes_home = tmp_path / ".hermes"
+    hermes_home.mkdir()
+    monkeypatch.setenv("HERMES_HOME", str(hermes_home))
+    monkeypatch.delenv("HERMES_DEV", raising=False)
+
+    container_mode = hermes_home / ".container-mode"
+    container_mode.write_text(
+        "# Written by NixOS activation script. Do not edit manually.\n"
+        "backend=podman\n"
+        "container_name=hermes-agent\n"
+        "exec_user=hermes\n"
+        "hermes_bin=/data/current-package/bin/hermes\n"
+    )
+    return hermes_home
+
+
+def test_get_container_exec_info_returns_metadata(container_env):
+    """Reads .container-mode and returns all fields including exec_user."""
+    with patch("hermes_cli.config._is_inside_container", return_value=False):
+        info = get_container_exec_info()
+
+    assert info is not None
+    assert info["backend"] == "podman"
+    assert info["container_name"] == "hermes-agent"
+    assert info["exec_user"] == "hermes"
+    assert info["hermes_bin"] == "/data/current-package/bin/hermes"
+
+
+def test_get_container_exec_info_none_inside_container(container_env):
+    """Returns None when we're already inside a container."""
+    with patch("hermes_cli.config._is_inside_container", return_value=True):
+        info = get_container_exec_info()
+
+    assert info is None
+
+
+def test_get_container_exec_info_none_without_file(tmp_path, monkeypatch):
+    """Returns None when .container-mode doesn't exist (native mode)."""
+    hermes_home = tmp_path / ".hermes"
+    hermes_home.mkdir()
+    monkeypatch.setenv("HERMES_HOME", str(hermes_home))
+    monkeypatch.delenv("HERMES_DEV", raising=False)
+
+    with patch("hermes_cli.config._is_inside_container", return_value=False):
+        info = get_container_exec_info()
+
+    assert info is None
+
+
+def test_get_container_exec_info_skipped_when_hermes_dev(container_env, monkeypatch):
+    """Returns None when HERMES_DEV=1 is set (dev mode bypass)."""
+    monkeypatch.setenv("HERMES_DEV", "1")
+
+    with patch("hermes_cli.config._is_inside_container", return_value=False):
+        info = get_container_exec_info()
+
+    assert info is None
+
+
+def test_get_container_exec_info_not_skipped_when_hermes_dev_zero(container_env, monkeypatch):
+    """HERMES_DEV=0 does NOT trigger bypass — only '1' does."""
+    monkeypatch.setenv("HERMES_DEV", "0")
+
+    with patch("hermes_cli.config._is_inside_container", return_value=False):
+        info = get_container_exec_info()
+
+    assert info is not None
+
+
+def test_get_container_exec_info_defaults():
+    """Falls back to defaults for missing keys."""
+    import tempfile
+
+    with tempfile.TemporaryDirectory() as tmpdir:
+        hermes_home = Path(tmpdir) / ".hermes"
+        hermes_home.mkdir()
+        (hermes_home / ".container-mode").write_text(
+            "# minimal file with no keys\n"
+        )
+
+        with patch("hermes_cli.config._is_inside_container", return_value=False), \
+             patch("hermes_cli.config.get_hermes_home", return_value=hermes_home), \
+             patch.dict(os.environ, {}, clear=False):
+            os.environ.pop("HERMES_DEV", None)
+            info = get_container_exec_info()
+
+        assert info is not None
+        assert info["backend"] == "docker"
+        assert info["container_name"] == "hermes-agent"
+        assert info["exec_user"] == "hermes"
+        assert info["hermes_bin"] == "/data/current-package/bin/hermes"
+
+
+def test_get_container_exec_info_docker_backend(container_env):
+    """Correctly reads docker backend with custom exec_user."""
+    (container_env / ".container-mode").write_text(
+        "backend=docker\n"
+        "container_name=hermes-custom\n"
+        "exec_user=myuser\n"
+        "hermes_bin=/opt/hermes/bin/hermes\n"
+    )
+
+    with patch("hermes_cli.config._is_inside_container", return_value=False):
+        info = get_container_exec_info()
+
+    assert info["backend"] == "docker"
+    assert info["container_name"] == "hermes-custom"
+    assert info["exec_user"] == "myuser"
+    assert info["hermes_bin"] == "/opt/hermes/bin/hermes"
+
+
+# =============================================================================
+# _exec_in_container
+# =============================================================================
+
+
+def test_exec_in_container_constructs_correct_command():
+    """Exec command includes -u exec_user, -e env vars, TTY flags."""
+    from hermes_cli.main import _exec_in_container
+
+    container_info = {
+        "backend": "docker",
+        "container_name": "hermes-agent",
+        "exec_user": "hermes",
+        "hermes_bin": "/data/current-package/bin/hermes",
+    }
+
+    with patch("shutil.which", return_value="/usr/bin/docker"), \
+         patch("subprocess.run") as mock_run, \
+         patch("sys.stdin") as mock_stdin, \
+         patch.dict(os.environ, {"TERM": "xterm-256color", "LANG": "en_US.UTF-8"},
+                    clear=False), \
+         pytest.raises(SystemExit) as exc_info:
+        mock_stdin.isatty.return_value = True
+        # First call = probe (inspect), second = exec
+        mock_run.return_value = MagicMock(returncode=0)
+
+        _exec_in_container(container_info, ["chat", "-m", "opus"])
+
+    assert exc_info.value.code == 0
+    assert mock_run.call_count == 2  # probe + exec
+    cmd = mock_run.call_args_list[1][0][0]  # second call = exec
+    # Runtime and exec
+    assert cmd[0] == "/usr/bin/docker"
+    assert cmd[1] == "exec"
+    # TTY flags
+    assert "-it" in cmd
+    # User flag
+    idx_u = cmd.index("-u")
+    assert cmd[idx_u + 1] == "hermes"
+    # Env passthrough
+    e_indices = [i for i, v in enumerate(cmd) if v == "-e"]
+    e_values = [cmd[i + 1] for i in e_indices]
+    assert "TERM=xterm-256color" in e_values
+    assert "LANG=en_US.UTF-8" in e_values
+    # Container + binary + args
+    assert "hermes-agent" in cmd
+    assert "/data/current-package/bin/hermes" in cmd
+    assert "chat" in cmd
+
+
+def test_exec_in_container_non_tty_uses_i_only():
+    """Non-TTY mode uses -i instead of -it."""
+    from hermes_cli.main import _exec_in_container
+
+    container_info = {
+        "backend": "docker",
+        "container_name": "hermes-agent",
+        "exec_user": "hermes",
+        "hermes_bin": "/data/current-package/bin/hermes",
+    }
+
+    with patch("shutil.which", return_value="/usr/bin/docker"), \
+         patch("subprocess.run") as mock_run, \
+         patch("sys.stdin") as mock_stdin, \
+         pytest.raises(SystemExit):
+        mock_stdin.isatty.return_value = False
+        mock_run.return_value = MagicMock(returncode=0)
+
+        _exec_in_container(container_info, ["sessions", "list"])
+
+    cmd = mock_run.call_args[0][0]
+    # Should have -i but NOT -it
+    assert "-i" in cmd
+    assert "-it" not in cmd
+
+
+def test_exec_in_container_no_runtime_hard_fails():
+    """Hard fails when runtime not found (no fallback)."""
+    from hermes_cli.main import _exec_in_container
+
+    container_info = {
+        "backend": "podman",
+        "container_name": "hermes-agent",
+        "exec_user": "hermes",
+        "hermes_bin": "/data/current-package/bin/hermes",
+    }
+
+    with patch("shutil.which", return_value=None), \
+         patch("subprocess.run") as mock_run, \
+         patch("sys.stdin") as mock_stdin, \
+         pytest.raises(SystemExit) as exc_info:
+        mock_stdin.isatty.return_value = True
+        _exec_in_container(container_info, ["chat"])
+
+    mock_run.assert_not_called()
+    assert exc_info.value.code != 0
+
+
+def test_exec_in_container_tty_retries_on_container_failure():
+    """TTY mode retries on docker exit codes 125-127, then hard fails."""
+    from hermes_cli.main import _exec_in_container
+
+    container_info = {
+        "backend": "docker",
+        "container_name": "hermes-agent",
+        "exec_user": "hermes",
+        "hermes_bin": "/data/current-package/bin/hermes",
+    }
+
+    with patch("shutil.which", return_value="/usr/bin/docker"), \
+         patch("subprocess.run") as mock_run, \
+         patch("sys.stdin") as mock_stdin, \
+         patch("sys.stderr"), \
+         patch("time.sleep") as mock_sleep, \
+         pytest.raises(SystemExit) as exc_info:
+        mock_stdin.isatty.return_value = True
+        # Probe succeeds (container visible), exec returns 125 (container stopped mid-run)
+        mock_run.side_effect = [MagicMock(returncode=0)] + \
+            [MagicMock(returncode=125)] * 5
+        _exec_in_container(container_info, ["chat"])
+
+    assert mock_sleep.call_count == 4  # 5 exec attempts, 4 sleeps
+    assert exc_info.value.code == 1
+
+
+def test_exec_in_container_non_tty_retries_silently_exits_126():
+    """Non-TTY mode retries on container failures then exits 126."""
+    from hermes_cli.main import _exec_in_container
+
+    container_info = {
+        "backend": "docker",
+        "container_name": "hermes-agent",
+        "exec_user": "hermes",
+        "hermes_bin": "/data/current-package/bin/hermes",
+    }
+
+    with patch("shutil.which", return_value="/usr/bin/docker"), \
+         patch("subprocess.run") as mock_run, \
+         patch("sys.stdin") as mock_stdin, \
+         patch("sys.stderr"), \
+         patch("time.sleep") as mock_sleep, \
+         pytest.raises(SystemExit) as exc_info:
+        mock_stdin.isatty.return_value = False
+        # Probe succeeds, exec returns 126 repeatedly
+        mock_run.side_effect = [MagicMock(returncode=0)] + \
+            [MagicMock(returncode=126)] * 10
+        _exec_in_container(container_info, ["sessions", "list"])
+
+    assert mock_sleep.call_count == 9  # 10 exec attempts, 9 sleeps
+    assert exc_info.value.code == 126
+
+
+def test_exec_in_container_propagates_hermes_exit_code():
+    """Non-zero exit from hermes inside container is propagated, not retried."""
+    from hermes_cli.main import _exec_in_container
+
+    container_info = {
+        "backend": "docker",
+        "container_name": "hermes-agent",
+        "exec_user": "hermes",
+        "hermes_bin": "/data/current-package/bin/hermes",
+    }
+
+    with patch("shutil.which", return_value="/usr/bin/docker"), \
+         patch("subprocess.run") as mock_run, \
+         patch("sys.stdin") as mock_stdin, \
+         patch("time.sleep") as mock_sleep, \
+         pytest.raises(SystemExit) as exc_info:
+        mock_stdin.isatty.return_value = True
+        # Probe succeeds (returncode=0), exec returns 1 (hermes error)
+        mock_run.side_effect = [
+            MagicMock(returncode=0),  # probe
+            MagicMock(returncode=1),  # exec — hermes error, not docker failure
+        ]
+        _exec_in_container(container_info, ["chat"])
+
+    mock_sleep.assert_not_called()  # No retries
+    assert mock_run.call_count == 2  # probe + one exec attempt
+    assert exc_info.value.code == 1