fix: --host filter now limits multi-host stack operations to single host (#175)

* fix: --host filter now limits multi-host stack operations to single host

Previously, when using `-H host` with a multi-host stack like `glances: all`,
the command would find the stack (correct) but then operate on ALL hosts for
that stack (incorrect). For example, `cf down -H nas` with `glances` would
stop glances on all 5 hosts instead of just nas.

Now, when `--host` is specified:
- `cf down -H nas` only stops stacks on nas, including only the nas instance
  of multi-host stacks
- `cf up -H nas` only starts stacks on nas (skips migration logic since
  host is explicitly specified)

Added tests for the new filter_host behavior in both executor and CLI.

* fix: Apply filter_host to logs and ps commands as well

Same bug as up/down: when using `-H host` with multi-host stacks,
logs and ps would show results from all hosts instead of just the
filtered host.

* fix: Don't remove multi-host stacks from state when host-filtered

When using `-H host` with a multi-host stack, we only stop one instance.
The stack is still running on other hosts, so we shouldn't remove it
from state entirely.

This prevents issues where:
- `cf apply` would try to re-start the stack
- `cf ps` would show incorrect running status
- Orphan detection would be confused

Added tests to verify state is preserved for host-filtered multi-host
operations and removed for full stack operations.

* refactor: Introduce StackSelection dataclass for cleaner context passing

Instead of passing filter_host separately through multiple layers,
bundle the selection context into a StackSelection dataclass:

- stacks: list of selected stack names
- config: the loaded Config
- host_filter: optional host filter from -H flag

This provides:
1. Cleaner APIs - context travels together instead of being scattered
2. is_instance_level() method - encapsulates the check for whether
   this is an instance-level operation (host-filtered multi-host stack)
3. Future extensibility - can add more context (dry_run, verbose, etc.)

Updated all callers of get_stacks() to use the new return type.

* Revert "refactor: Introduce StackSelection dataclass for cleaner context passing"

This reverts commit e6e9eed93e.

* feat: Proper per-host state tracking for multi-host stacks

- Add `remove_stack_host()` to remove a single host from a multi-host stack's state
- Add `add_stack_host()` to add a single host to a stack's state
- Update `down` command to use `remove_stack_host` for host-filtered multi-host stacks
- Update `up` command to use `add_stack_host` for host-filtered operations

This ensures the state file accurately reflects which hosts each stack is running on,
rather than just tracking if it's running at all.

* fix: Use set comparisons for host list tests

Host lists may be reordered during YAML save/load, so test for
set equality rather than list equality.

* refactor: Merge remove_stack_host into remove_stack as optional parameter

Instead of a separate function, `remove_stack` now takes an optional
`host` parameter. When specified, it removes only that host from
multi-host stacks. This reduces API surface and follows the existing
pattern.

* fix: Restore deterministic host list sorting and add filter_host test

- Restore sorting of list values in _sorted_dict for consistent YAML output
- Add test for logs --host passing filter_host to run_on_stacks

src/compose_farm/cli/lifecycle.py

@@ -37,6 +37,7 @@ from compose_farm.operations import (
     up_stacks,
 )
 from compose_farm.state import (
+    add_stack_host,
     get_orphaned_stacks,
     get_stack_host,
     get_stacks_needing_migration,
@@ -73,6 +74,23 @@ def up(
                 cfg, stack_list, build_up_cmd(pull=pull, build=build, service=service), raw=True
             )
         )
+    elif host:
+        # For host-filtered up, use run_on_stacks to only affect that host
+        # (skips migration logic, which is intended when explicitly specifying a host)
+        results = run_async(
+            run_on_stacks(
+                cfg,
+                stack_list,
+                build_up_cmd(pull=pull, build=build),
+                raw=True,
+                filter_host=host,
+            )
+        )
+        # Update state for successful host-filtered operations
+        for result in results:
+            if result.success:
+                base_stack = result.stack.split("@")[0]
+                add_stack_host(cfg, base_stack, host)
     else:
         results = run_async(up_stacks(cfg, stack_list, raw=True, pull=pull, build=build))
     maybe_regenerate_traefik(cfg, results)
@@ -116,17 +134,20 @@ def down(
 
     stack_list, cfg = get_stacks(stacks or [], all_stacks, config, host=host)
     raw = len(stack_list) == 1
-    results = run_async(run_on_stacks(cfg, stack_list, "down", raw=raw))
+    results = run_async(run_on_stacks(cfg, stack_list, "down", raw=raw, filter_host=host))
 
-    # Remove from state on success
+    # Update state on success
     # For multi-host stacks, result.stack is "stack@host", extract base name
-    removed_stacks: set[str] = set()
+    updated_stacks: set[str] = set()
     for result in results:
         if result.success:
             base_stack = result.stack.split("@")[0]
-            if base_stack not in removed_stacks:
-                remove_stack(cfg, base_stack)
-                removed_stacks.add(base_stack)
+            if base_stack not in updated_stacks:
+                # When host is specified for multi-host stack, removes just that host
+                # Otherwise removes entire stack from state
+                filter_host = host if host and cfg.is_multi_host(base_stack) else None
+                remove_stack(cfg, base_stack, filter_host)
+                updated_stacks.add(base_stack)
 
     maybe_regenerate_traefik(cfg, results)
     report_results(results)

src/compose_farm/cli/monitoring.py

@@ -248,7 +248,7 @@ def logs(
         cmd += " -f"
     if service:
         cmd += f" {service}"
-    results = run_async(run_on_stacks(cfg, stack_list, cmd))
+    results = run_async(run_on_stacks(cfg, stack_list, cmd, filter_host=host))
     report_results(results)
 
 
@@ -272,7 +272,7 @@ def ps(
         print_error("--service requires exactly one stack")
         raise typer.Exit(1)
     cmd = f"ps {service}" if service else "ps"
-    results = run_async(run_on_stacks(cfg, stack_list, cmd))
+    results = run_async(run_on_stacks(cfg, stack_list, cmd, filter_host=host))
     report_results(results)
 
 

src/compose_farm/executor.py

@@ -392,13 +392,17 @@ async def run_on_stacks(
     *,
     stream: bool = True,
     raw: bool = False,
+    filter_host: str | None = None,
 ) -> list[CommandResult]:
     """Run a docker compose command on multiple stacks in parallel.
 
-    For multi-host stacks, runs on all configured hosts.
-    Note: raw=True only makes sense for single-stack operations.
+    For multi-host stacks, runs on all configured hosts unless filter_host is set,
+    in which case only the filtered host is affected. raw=True only makes sense
+    for single-stack operations.
     """
-    return await run_sequential_on_stacks(config, stacks, [compose_cmd], stream=stream, raw=raw)
+    return await run_sequential_on_stacks(
+        config, stacks, [compose_cmd], stream=stream, raw=raw, filter_host=filter_host
+    )
 
 
 async def _run_sequential_stack_commands(
@@ -418,6 +422,33 @@ async def _run_sequential_stack_commands(
     return CommandResult(stack=stack, exit_code=0, success=True)
 
 
+async def _run_sequential_stack_commands_on_host(
+    config: Config,
+    stack: str,
+    host_name: str,
+    commands: list[str],
+    *,
+    stream: bool = True,
+    raw: bool = False,
+    prefix: str | None = None,
+) -> CommandResult:
+    """Run multiple compose commands sequentially for a stack on a specific host.
+
+    Used when --host filter is applied to a multi-host stack.
+    """
+    stack_dir = config.get_stack_dir(stack)
+    host = config.hosts[host_name]
+    label = f"{stack}@{host_name}"
+
+    for cmd in commands:
+        _print_compose_command(host_name, stack, cmd)
+        command = f'cd "{stack_dir}" && docker compose {cmd}'
+        result = await run_command(host, command, label, stream=stream, raw=raw, prefix=prefix)
+        if not result.success:
+            return result
+    return CommandResult(stack=label, exit_code=0, success=True)
+
+
 async def _run_sequential_stack_commands_multi_host(
     config: Config,
     stack: str,
@@ -469,11 +500,13 @@ async def run_sequential_on_stacks(
     *,
     stream: bool = True,
     raw: bool = False,
+    filter_host: str | None = None,
 ) -> list[CommandResult]:
     """Run sequential commands on multiple stacks in parallel.
 
-    For multi-host stacks, runs on all configured hosts.
-    Note: raw=True only makes sense for single-stack operations.
+    For multi-host stacks, runs on all configured hosts unless filter_host is set,
+    in which case only the filtered host is affected. raw=True only makes sense
+    for single-stack operations.
     """
     # Skip prefix for single-stack operations (command line already shows context)
     prefix: str | None = "" if len(stacks) == 1 else None
@@ -483,12 +516,20 @@ async def run_sequential_on_stacks(
     single_host_tasks = []
 
     for stack in stacks:
-        if config.is_multi_host(stack):
+        if config.is_multi_host(stack) and filter_host is None:
+            # Multi-host stack without filter: run on all hosts
             multi_host_tasks.append(
                 _run_sequential_stack_commands_multi_host(
                     config, stack, commands, stream=stream, raw=raw, prefix=prefix
                 )
             )
+        elif config.is_multi_host(stack) and filter_host is not None:
+            # Multi-host stack with filter: run only on filtered host
+            single_host_tasks.append(
+                _run_sequential_stack_commands_on_host(
+                    config, stack, filter_host, commands, stream=stream, raw=raw, prefix=prefix
+                )
+            )
         else:
             single_host_tasks.append(
                 _run_sequential_stack_commands(

src/compose_farm/state.py

@@ -112,10 +112,46 @@ def set_multi_host_stack(config: Config, stack: str, hosts: list[str]) -> None:
         state[stack] = hosts
 
 
-def remove_stack(config: Config, stack: str) -> None:
-    """Remove a stack from the state (after down)."""
+def remove_stack(config: Config, stack: str, host: str | None = None) -> None:
+    """Remove a stack from the state (after down).
+
+    If host is provided, only removes that host from a multi-host stack.
+    If the list becomes empty, removes the stack entirely.
+    For single-host stacks with host specified, removes only if host matches.
+    """
     with _modify_state(config) as state:
+        if stack not in state:
+            return
+        if host is None:
             state.pop(stack, None)
+            return
+        current = state[stack]
+        if isinstance(current, list):
+            new_hosts = [h for h in current if h != host]
+            if new_hosts:
+                state[stack] = new_hosts
+            else:
+                del state[stack]
+        elif current == host:
+            del state[stack]
+
+
+def add_stack_host(config: Config, stack: str, host: str) -> None:
+    """Add a single host to a stack's state.
+
+    For multi-host stacks, adds the host to the list if not present.
+    For single-host stacks or new entries, sets the host directly.
+    """
+    with _modify_state(config) as state:
+        current = state.get(stack)
+        if current is None:
+            state[stack] = host
+        elif isinstance(current, list):
+            if host not in current:
+                state[stack] = [*current, host]
+        elif current != host:
+            # Convert single host to list
+            state[stack] = [current, host]
 
 
 def get_stacks_needing_migration(config: Config) -> list[str]:

tests/test_cli_lifecycle.py

@@ -437,3 +437,132 @@ class TestDownOrphaned:
             )
 
         assert exc_info.value.exit_code == 1
+
+
+class TestHostFilterMultiHost:
+    """Tests for --host filter with multi-host stacks."""
+
+    def _make_multi_host_config(self, tmp_path: Path) -> Config:
+        """Create a config with a multi-host stack."""
+        compose_dir = tmp_path / "compose"
+        compose_dir.mkdir()
+
+        # Create stack directories
+        for stack in ["single-host", "multi-host"]:
+            stack_dir = compose_dir / stack
+            stack_dir.mkdir()
+            (stack_dir / "docker-compose.yml").write_text("services: {}\n")
+
+        config_path = tmp_path / "compose-farm.yaml"
+        config_path.write_text("")
+
+        return Config(
+            compose_dir=compose_dir,
+            hosts={
+                "host1": Host(address="192.168.1.1"),
+                "host2": Host(address="192.168.1.2"),
+                "host3": Host(address="192.168.1.3"),
+            },
+            stacks={
+                "single-host": "host1",
+                "multi-host": ["host1", "host2", "host3"],  # runs on all 3 hosts
+            },
+            config_path=config_path,
+        )
+
+    def test_down_host_filter_limits_multi_host_stack(self, tmp_path: Path) -> None:
+        """--host filter should only run down on that host for multi-host stacks."""
+        cfg = self._make_multi_host_config(tmp_path)
+
+        with (
+            patch("compose_farm.cli.lifecycle.load_config_or_exit", return_value=cfg),
+            patch("compose_farm.cli.lifecycle.get_stacks") as mock_get_stacks,
+            patch("compose_farm.cli.lifecycle.run_on_stacks") as mock_run,
+            patch(
+                "compose_farm.cli.lifecycle.run_async",
+                return_value=[_make_result("multi-host@host1")],
+            ),
+            patch("compose_farm.cli.lifecycle.remove_stack"),
+            patch("compose_farm.cli.lifecycle.maybe_regenerate_traefik"),
+            patch("compose_farm.cli.lifecycle.report_results"),
+        ):
+            mock_get_stacks.return_value = (["multi-host"], cfg)
+
+            down(
+                stacks=None,
+                all_stacks=False,
+                orphaned=False,
+                host="host1",
+                config=None,
+            )
+
+            # Verify run_on_stacks was called with filter_host="host1"
+            mock_run.assert_called_once()
+            call_kwargs = mock_run.call_args.kwargs
+            assert call_kwargs.get("filter_host") == "host1"
+
+    def test_down_host_filter_removes_host_from_state(self, tmp_path: Path) -> None:
+        """--host filter should remove just that host from multi-host stack's state.
+
+        When stopping only one instance of a multi-host stack, we should update
+        state to remove just that host, not the entire stack.
+        """
+        cfg = self._make_multi_host_config(tmp_path)
+
+        with (
+            patch("compose_farm.cli.lifecycle.load_config_or_exit", return_value=cfg),
+            patch("compose_farm.cli.lifecycle.get_stacks") as mock_get_stacks,
+            patch("compose_farm.cli.lifecycle.run_on_stacks"),
+            patch(
+                "compose_farm.cli.lifecycle.run_async",
+                return_value=[_make_result("multi-host@host1")],
+            ),
+            patch("compose_farm.cli.lifecycle.remove_stack") as mock_remove,
+            patch("compose_farm.cli.lifecycle.maybe_regenerate_traefik"),
+            patch("compose_farm.cli.lifecycle.report_results"),
+        ):
+            mock_get_stacks.return_value = (["multi-host"], cfg)
+
+            down(
+                stacks=None,
+                all_stacks=False,
+                orphaned=False,
+                host="host1",
+                config=None,
+            )
+
+            # remove_stack should be called with the host parameter
+            mock_remove.assert_called_once_with(cfg, "multi-host", "host1")
+
+    def test_down_without_host_filter_removes_from_state(self, tmp_path: Path) -> None:
+        """Without --host filter, multi-host stacks SHOULD be removed from state."""
+        cfg = self._make_multi_host_config(tmp_path)
+
+        with (
+            patch("compose_farm.cli.lifecycle.load_config_or_exit", return_value=cfg),
+            patch("compose_farm.cli.lifecycle.get_stacks") as mock_get_stacks,
+            patch("compose_farm.cli.lifecycle.run_on_stacks"),
+            patch(
+                "compose_farm.cli.lifecycle.run_async",
+                return_value=[
+                    _make_result("multi-host@host1"),
+                    _make_result("multi-host@host2"),
+                    _make_result("multi-host@host3"),
+                ],
+            ),
+            patch("compose_farm.cli.lifecycle.remove_stack") as mock_remove,
+            patch("compose_farm.cli.lifecycle.maybe_regenerate_traefik"),
+            patch("compose_farm.cli.lifecycle.report_results"),
+        ):
+            mock_get_stacks.return_value = (["multi-host"], cfg)
+
+            down(
+                stacks=None,
+                all_stacks=False,
+                orphaned=False,
+                host=None,  # No host filter
+                config=None,
+            )
+
+            # remove_stack SHOULD be called with host=None when stopping all instances
+            mock_remove.assert_called_once_with(cfg, "multi-host", None)

tests/test_cli_logs.py

@@ -29,6 +29,28 @@ def _make_config(tmp_path: Path) -> Config:
     )
 
 
+def _make_multi_host_config(tmp_path: Path) -> Config:
+    """Create a config with a multi-host stack for testing."""
+    compose_dir = tmp_path / "compose"
+    compose_dir.mkdir()
+    for svc in ("single-host", "multi-host"):
+        svc_dir = compose_dir / svc
+        svc_dir.mkdir()
+        (svc_dir / "docker-compose.yml").write_text("services: {}\n")
+
+    return Config(
+        compose_dir=compose_dir,
+        hosts={
+            "host1": Host(address="192.168.1.1"),
+            "host2": Host(address="192.168.1.2"),
+        },
+        stacks={
+            "single-host": "host1",
+            "multi-host": ["host1", "host2"],
+        },
+    )
+
+
 def _make_result(stack: str) -> CommandResult:
     """Create a successful command result."""
     return CommandResult(stack=stack, exit_code=0, success=True, stdout="", stderr="")
@@ -205,3 +227,26 @@ class TestLogsHostFilter:
             )
 
         assert exc_info.value.exit_code == 1
+
+    def test_logs_host_filter_passes_filter_host_to_run_on_stacks(self, tmp_path: Path) -> None:
+        """--host should pass filter_host to run_on_stacks for multi-host stacks."""
+        cfg = _make_multi_host_config(tmp_path)
+        mock_run_async, _ = _mock_run_async_factory(["multi-host@host1"])
+
+        with (
+            patch("compose_farm.cli.common.load_config_or_exit", return_value=cfg),
+            patch("compose_farm.cli.monitoring.run_async", side_effect=mock_run_async),
+            patch("compose_farm.cli.monitoring.run_on_stacks") as mock_run,
+        ):
+            logs(
+                stacks=None,
+                all_stacks=False,
+                host="host1",
+                follow=False,
+                tail=None,
+                config=None,
+            )
+
+            mock_run.assert_called_once()
+            call_kwargs = mock_run.call_args.kwargs
+            assert call_kwargs.get("filter_host") == "host1"

tests/test_executor.py

@@ -229,6 +229,52 @@ class TestRunOnStacks:
         assert results[0].stack == "svc1"
         assert results[1].stack == "svc2"
 
+    async def test_run_on_stacks_filter_host_limits_multi_host(self) -> None:
+        """filter_host should only run on that host for multi-host stacks."""
+        config = Config(
+            compose_dir=Path("/tmp"),
+            hosts={
+                "host1": Host(address="192.168.1.1"),
+                "host2": Host(address="192.168.1.2"),
+                "host3": Host(address="192.168.1.3"),
+            },
+            stacks={"multi-svc": ["host1", "host2", "host3"]},  # multi-host stack
+        )
+
+        mock_result = CommandResult(stack="multi-svc@host1", exit_code=0, success=True)
+        with patch("compose_farm.executor.run_command", new_callable=AsyncMock) as mock_run:
+            mock_run.return_value = mock_result
+            results = await run_on_stacks(
+                config, ["multi-svc"], "down", stream=False, filter_host="host1"
+            )
+
+            # Should only call run_command once (for host1), not 3 times
+            assert mock_run.call_count == 1
+            # Result should be for the filtered host
+            assert len(results) == 1
+            assert results[0].stack == "multi-svc@host1"
+
+    async def test_run_on_stacks_no_filter_runs_all_hosts(self) -> None:
+        """Without filter_host, multi-host stacks run on all configured hosts."""
+        config = Config(
+            compose_dir=Path("/tmp"),
+            hosts={
+                "host1": Host(address="192.168.1.1"),
+                "host2": Host(address="192.168.1.2"),
+            },
+            stacks={"multi-svc": ["host1", "host2"]},  # multi-host stack
+        )
+
+        mock_result = CommandResult(stack="multi-svc", exit_code=0, success=True)
+        with patch("compose_farm.executor.run_command", new_callable=AsyncMock) as mock_run:
+            mock_run.return_value = mock_result
+            results = await run_on_stacks(config, ["multi-svc"], "down", stream=False)
+
+            # Should call run_command twice (once per host)
+            assert mock_run.call_count == 2
+            # Results should be for both hosts
+            assert len(results) == 2
+
 
 @linux_only
 class TestCheckPathsExist:

tests/test_state.py

@@ -6,6 +6,7 @@ import pytest
 
 from compose_farm.config import Config, Host
 from compose_farm.state import (
+    add_stack_host,
     get_orphaned_stacks,
     get_stack_host,
     get_stacks_not_in_state,
@@ -143,6 +144,110 @@ class TestRemoveStack:
         result = load_state(config)
         assert result["plex"] == "nas01"
 
+    def test_remove_host_from_list(self, config: Config) -> None:
+        """Removes one host from a multi-host stack's list."""
+        state_file = config.get_state_path()
+        state_file.write_text("deployed:\n  glances:\n    - nas\n    - nuc\n    - hp\n")
+
+        remove_stack(config, "glances", "nas")
+
+        result = load_state(config)
+        assert set(result["glances"]) == {"nuc", "hp"}
+
+    def test_remove_last_host_removes_stack(self, config: Config) -> None:
+        """Removing the last host removes the stack entirely."""
+        state_file = config.get_state_path()
+        state_file.write_text("deployed:\n  glances:\n    - nas\n")
+
+        remove_stack(config, "glances", "nas")
+
+        result = load_state(config)
+        assert "glances" not in result
+
+    def test_remove_host_from_single_host_stack(self, config: Config) -> None:
+        """Removing host from single-host stack removes it if host matches."""
+        state_file = config.get_state_path()
+        state_file.write_text("deployed:\n  plex: nas\n")
+
+        remove_stack(config, "plex", "nas")
+
+        result = load_state(config)
+        assert "plex" not in result
+
+    def test_remove_wrong_host_from_single_host_stack(self, config: Config) -> None:
+        """Removing wrong host from single-host stack does nothing."""
+        state_file = config.get_state_path()
+        state_file.write_text("deployed:\n  plex: nas\n")
+
+        remove_stack(config, "plex", "nuc")
+
+        result = load_state(config)
+        assert result["plex"] == "nas"
+
+    def test_remove_host_from_nonexistent_stack(self, config: Config) -> None:
+        """Removing host from nonexistent stack doesn't error."""
+        state_file = config.get_state_path()
+        state_file.write_text("deployed:\n  plex: nas\n")
+
+        remove_stack(config, "unknown", "nas")  # Should not raise
+
+        result = load_state(config)
+        assert result["plex"] == "nas"
+
+
+class TestAddStackHost:
+    """Tests for add_stack_host function."""
+
+    def test_add_host_to_new_stack(self, config: Config) -> None:
+        """Adding host to new stack creates single-host entry."""
+        state_file = config.get_state_path()
+        state_file.write_text("deployed: {}\n")
+
+        add_stack_host(config, "plex", "nas")
+
+        result = load_state(config)
+        assert result["plex"] == "nas"
+
+    def test_add_host_to_list(self, config: Config) -> None:
+        """Adding host to existing list appends it."""
+        state_file = config.get_state_path()
+        state_file.write_text("deployed:\n  glances:\n    - nas\n    - nuc\n")
+
+        add_stack_host(config, "glances", "hp")
+
+        result = load_state(config)
+        assert set(result["glances"]) == {"nas", "nuc", "hp"}
+
+    def test_add_duplicate_host_to_list(self, config: Config) -> None:
+        """Adding duplicate host to list does nothing."""
+        state_file = config.get_state_path()
+        state_file.write_text("deployed:\n  glances:\n    - nas\n    - nuc\n")
+
+        add_stack_host(config, "glances", "nas")
+
+        result = load_state(config)
+        assert set(result["glances"]) == {"nas", "nuc"}
+
+    def test_add_second_host_converts_to_list(self, config: Config) -> None:
+        """Adding second host to single-host stack converts to list."""
+        state_file = config.get_state_path()
+        state_file.write_text("deployed:\n  plex: nas\n")
+
+        add_stack_host(config, "plex", "nuc")
+
+        result = load_state(config)
+        assert set(result["plex"]) == {"nas", "nuc"}
+
+    def test_add_same_host_to_single_host_stack(self, config: Config) -> None:
+        """Adding same host to single-host stack does nothing."""
+        state_file = config.get_state_path()
+        state_file.write_text("deployed:\n  plex: nas\n")
+
+        add_stack_host(config, "plex", "nas")
+
+        result = load_state(config)
+        assert result["plex"] == "nas"
+
 
 class TestGetOrphanedStacks:
     """Tests for get_orphaned_stacks function."""