feat(nix): container-aware CLI — auto-route hermes chat into managed container

hermes_cli/config.py

@@ -141,6 +141,68 @@ def managed_error(action: str = "modify configuration"):
     print(format_managed_message(action), file=sys.stderr)
 
 
+# =============================================================================
+# Container-aware CLI (NixOS container mode)
+# =============================================================================
+
+def _is_inside_container() -> bool:
+    """Detect if we're already running inside a Docker/Podman container."""
+    # Standard Docker/Podman indicators
+    if os.path.exists("/.dockerenv"):
+        return True
+    # Podman uses /run/.containerenv
+    if os.path.exists("/run/.containerenv"):
+        return True
+    # Check cgroup for container runtime evidence (works for both Docker & Podman)
+    try:
+        with open("/proc/1/cgroup", "r") as f:
+            cgroup = f.read()
+            if "docker" in cgroup or "podman" in cgroup or "/lxc/" in cgroup:
+                return True
+    except (OSError, IOError):
+        pass
+    return False
+
+
+def get_container_exec_info() -> Optional[dict]:
+    """Read container mode metadata from HERMES_HOME/.container-mode.
+
+    Returns a dict with keys: backend, container_name, hermes_bin
+    or None if container mode is not active or we're already inside the container.
+
+    The .container-mode file is written by the NixOS activation script when
+    container.enable = true. It tells the host CLI to exec into the container
+    instead of running locally.
+    """
+    if _is_inside_container():
+        return None
+
+    container_mode_file = get_hermes_home() / ".container-mode"
+    if not container_mode_file.exists():
+        return None
+
+    try:
+        info = {}
+        with open(container_mode_file, "r") as f:
+            for line in f:
+                line = line.strip()
+                if "=" in line and not line.startswith("#"):
+                    key, _, value = line.partition("=")
+                    info[key.strip()] = value.strip()
+
+        backend = info.get("backend", "docker")
+        container_name = info.get("container_name", "hermes-agent")
+        hermes_bin = info.get("hermes_bin", "/data/current-package/bin/hermes")
+
+        return {
+            "backend": backend,
+            "container_name": container_name,
+            "hermes_bin": hermes_bin,
+        }
+    except (OSError, IOError):
+        return None
+
+
 # =============================================================================
 # Config paths
 # =============================================================================

hermes_cli/main.py

@@ -528,6 +528,56 @@ def _resolve_last_cli_session() -> Optional[str]:
     return None
 
 
+def _exec_in_container(container_info: dict, cli_args: list):
+    """Replace the current process with a command inside the managed container.
+
+    Uses os.execvp to hand off to docker/podman exec, preserving the TTY
+    so the interactive CLI works seamlessly inside the container.
+
+    Args:
+        container_info: dict with backend, container_name, hermes_bin
+        cli_args: the original CLI arguments (everything after 'hermes')
+    """
+    import shutil
+    import subprocess
+
+    backend = container_info["backend"]
+    container_name = container_info["container_name"]
+    hermes_bin = container_info["hermes_bin"]
+
+    # Find the container runtime on PATH
+    runtime = shutil.which(backend)
+    if not runtime:
+        print(f"Warning: {backend} not found on PATH, falling back to host CLI.",
+              file=sys.stderr)
+        return  # Fall through to normal CLI
+
+    # Check if the container is actually running
+    try:
+        result = subprocess.run(
+            [runtime, "inspect", "--format", "{{.State.Running}}", container_name],
+            capture_output=True, text=True, timeout=5
+        )
+        if result.returncode != 0 or result.stdout.strip().lower() != "true":
+            print(f"Warning: container '{container_name}' is not running, falling back to host CLI.",
+                  file=sys.stderr)
+            return
+    except (subprocess.TimeoutExpired, OSError):
+        return  # Fall through on any error
+
+    # Filter out --host flag from forwarded args (it's not meaningful inside)
+    forwarded_args = [a for a in cli_args if a != "--host"]
+
+    # Build the exec command
+    exec_cmd = [runtime, "exec", "-it", container_name, hermes_bin] + forwarded_args
+
+    print(f"Routing to container '{container_name}' via {backend}...",
+          file=sys.stderr)
+
+    # Replace the current process — this never returns on success
+    os.execvp(runtime, exec_cmd)
+
+
 def _resolve_session_by_name_or_id(name_or_id: str) -> Optional[str]:
     """Resolve a session name (title) or ID to a session ID.
 
@@ -556,6 +606,21 @@ def _resolve_session_by_name_or_id(name_or_id: str) -> Optional[str]:
 
 def cmd_chat(args):
     """Run interactive chat CLI."""
+    # ── Container-aware routing ──────────────────────────────────────────
+    # When NixOS container mode is active and we're on the host, exec into
+    # the managed container instead of running locally. --host bypasses this.
+    if not getattr(args, "host", False):
+        try:
+            from hermes_cli.config import get_container_exec_info
+            container_info = get_container_exec_info()
+            if container_info:
+                _exec_in_container(container_info, sys.argv[1:])
+                # _exec_in_container calls os.execvp which replaces the process.
+                # If we get here, the exec failed.
+                sys.exit(1)
+        except Exception:
+            pass  # Fall through to normal CLI on any detection error
+
     # Resolve --continue into --resume with the latest CLI session or by name
     continue_val = getattr(args, "continue_last", None)
     if continue_val and not getattr(args, "resume", None):
@@ -4386,6 +4451,12 @@ def main():
         default=None,
         help="Session source tag for filtering (default: cli). Use 'tool' for third-party integrations that should not appear in user session lists."
     )
+    chat_parser.add_argument(
+        "--host",
+        action="store_true",
+        default=False,
+        help="Run on the host even when NixOS container mode is active (bypass container exec)"
+    )
     chat_parser.set_defaults(func=cmd_chat)
 
     # =========================================================================

nix/nixosModules.nix

@@ -611,6 +611,22 @@
           chown ${cfg.user}:${cfg.group} ${cfg.stateDir}/.hermes/.managed
           chmod 0644 ${cfg.stateDir}/.hermes/.managed
 
+          # Container mode metadata — tells the host CLI to exec into the
+          # container instead of running locally. Removed when container mode
+          # is disabled so the host CLI falls back to native execution.
+          ${if cfg.container.enable then ''
+            cat > ${cfg.stateDir}/.hermes/.container-mode <<'HERMES_CONTAINER_MODE_EOF'
+# Written by NixOS activation script. Do not edit manually.
+backend=${cfg.container.backend}
+container_name=${containerName}
+hermes_bin=${containerDataDir}/current-package/bin/hermes
+HERMES_CONTAINER_MODE_EOF
+            chown ${cfg.user}:${cfg.group} ${cfg.stateDir}/.hermes/.container-mode
+            chmod 0644 ${cfg.stateDir}/.hermes/.container-mode
+          '' else ''
+            rm -f ${cfg.stateDir}/.hermes/.container-mode
+          ''}
+
           # Seed auth file if provided
           ${lib.optionalString (cfg.authFile != null) ''
             ${if cfg.authFileForceOverwrite then ''