feat(tmux): spawn teammates in windows when USE_TMUX_WINDOWS is set

README.md

@@ -64,7 +64,7 @@ Or add to `~/.config/opencode/opencode.json` (OpenCode):
 |------|-------------|
 | `team_create` | Create a new agent team. One team per server session. |
 | `team_delete` | Delete a team and all its data. Fails if teammates are still active. |
-| `spawn_teammate` | Spawn a teammate in a tmux pane (Claude or OpenCode backend). |
+| `spawn_teammate` | Spawn a teammate in tmux (pane by default, window when `USE_TMUX_WINDOWS` is set). |
 | `send_message` | Send direct messages, broadcasts, shutdown/plan approval responses. |
 | `read_inbox` | Read messages from an agent's inbox. |
 | `poll_inbox` | Long-poll an inbox for new messages (up to 30s). |
@@ -73,12 +73,12 @@ Or add to `~/.config/opencode/opencode.json` (OpenCode):
 | `task_update` | Update task status, owner, dependencies, or metadata. |
 | `task_list` | List all tasks for a team. |
 | `task_get` | Get full details of a specific task. |
-| `force_kill_teammate` | Forcibly kill a teammate's tmux pane and clean up. |
+| `force_kill_teammate` | Forcibly kill a teammate's tmux pane/window and clean up. |
 | `process_shutdown_approved` | Remove a teammate after graceful shutdown approval. |
 
 ## How it works
 
-- **Spawning**: Teammates launch in tmux panes via `tmux split-window`. Backend can be Claude (`claude`) or OpenCode (`opencode`). Each gets a unique agent ID (`name@team`) and color.
+- **Spawning**: Teammates launch in tmux via `tmux split-window` (default) or `tmux new-window` when `USE_TMUX_WINDOWS` is set. Backend can be Claude (`claude`) or OpenCode (`opencode`). Each gets a unique agent ID (`name@team`) and color.
 - **Messaging**: JSON-based inboxes under `~/.claude/teams/<team>/inboxes/`. File locking (`fcntl`) prevents corruption from concurrent reads/writes.
 - **Tasks**: JSON task files under `~/.claude/tasks/<team>/`. Tasks have status tracking, ownership, and dependency management (`blocks`/`blockedBy`).
 - **Concurrency safety**: Atomic writes via `tempfile` + `os.replace` for config. `fcntl` file locks for inbox operations.

src/claude_teams/server.py

@@ -25,13 +25,14 @@
     discover_opencode_models,
     kill_tmux_pane,
     spawn_teammate,
+    use_tmux_windows,
 )
 
 logger = logging.getLogger(__name__)
 
 
 _SPAWN_TOOL_BASE_DESCRIPTION = (
-    "Spawn a new teammate in a tmux pane. The teammate receives its initial "
+    "Spawn a new teammate in a tmux {target}. The teammate receives its initial "
     "prompt via inbox and begins working autonomously. Names must be unique "
     "within the team."
 )
@@ -44,7 +45,8 @@ def _build_spawn_description(
     opencode_server_url: str | None = None,
     opencode_agents: list[dict] | None = None,
 ) -> str:
-    parts = [_SPAWN_TOOL_BASE_DESCRIPTION]
+    tmux_target = "window" if use_tmux_windows() else "pane"
+    parts = [_SPAWN_TOOL_BASE_DESCRIPTION.format(target=tmux_target)]
     backends = []
     if claude_binary:
         backends.append("'claude' (default, models: sonnet, opus, haiku)")
@@ -162,7 +164,7 @@ def spawn_teammate_tool(
     plan_mode_required: bool = False,
     backend_type: Literal["claude", "opencode"] = "claude",
 ) -> dict:
-    """Spawn a new teammate in a tmux pane. Description is dynamically updated
+    """Spawn a new teammate in tmux. Description is dynamically updated
     at startup with available backends and models."""
     ls = _get_lifespan(ctx)
     opencode_agent = None
@@ -558,9 +560,9 @@ def read_config(team_name: str) -> dict:
 
 @mcp.tool
 def force_kill_teammate(team_name: str, agent_name: str, ctx: Context) -> dict:
-    """Forcibly kill a teammate's tmux pane. Use when graceful shutdown via
+    """Forcibly kill a teammate's tmux target. Use when graceful shutdown via
     send_message(type='shutdown_request') is not possible or not responding.
-    Kills the tmux pane, removes member from config, and resets their tasks."""
+    Kills the tmux pane/window, removes member from config, and resets their tasks."""
     oc_url = _get_lifespan(ctx).get("opencode_server_url")
     config = teams.read_config(team_name)
     member = None

src/claude_teams/spawner.py

@@ -1,5 +1,6 @@
 from __future__ import annotations
 
+import os
 import shlex
 import shutil
 import subprocess
@@ -33,6 +34,27 @@ def discover_harness_binary(name: str) -> str | None:
     return shutil.which(name)
 
 
+def use_tmux_windows() -> bool:
+    """Return True when teammate processes should be spawned in tmux windows."""
+    return os.environ.get("USE_TMUX_WINDOWS") is not None
+
+
+def build_tmux_spawn_args(command: str, name: str) -> list[str]:
+    """Build the tmux command used to spawn a teammate process."""
+    if use_tmux_windows():
+        return [
+            "tmux",
+            "new-window",
+            "-dP",
+            "-F",
+            "#{window_id}",
+            "-n",
+            f"@claude-team | {name}",
+            command,
+        ]
+    return ["tmux", "split-window", "-dP", "-F", "#{pane_id}", command]
+
+
 def discover_opencode_models(opencode_binary: str) -> list[str]:
     """Run ``opencode models --refresh`` and return available model names."""
     try:
@@ -201,7 +223,7 @@ def spawn_teammate(
             cmd = build_spawn_command(member, claude_binary, lead_session_id)
 
         result = subprocess.run(
-            ["tmux", "split-window", "-dP", "-F", "#{pane_id}", cmd],
+            build_tmux_spawn_args(cmd, name),
             capture_output=True,
             text=True,
             check=True,
@@ -236,4 +258,7 @@ def spawn_teammate(
 
 
 def kill_tmux_pane(pane_id: str) -> None:
+    if pane_id.startswith("@"):
+        subprocess.run(["tmux", "kill-window", "-t", pane_id], check=False)
+        return
     subprocess.run(["tmux", "kill-pane", "-t", pane_id], check=False)

tests/test_server.py

@@ -832,6 +832,16 @@ async def opencode_only_client(tmp_path: Path, monkeypatch):
 
 
 class TestBuildSpawnDescription:
+    def test_should_reference_tmux_pane_by_default(self, monkeypatch) -> None:
+        monkeypatch.delenv("USE_TMUX_WINDOWS", raising=False)
+        desc = _build_spawn_description("/bin/claude", None, [])
+        assert "tmux pane" in desc
+
+    def test_should_reference_tmux_window_when_enabled(self, monkeypatch) -> None:
+        monkeypatch.setenv("USE_TMUX_WINDOWS", "1")
+        desc = _build_spawn_description("/bin/claude", None, [])
+        assert "tmux window" in desc
+
     def test_both_backends_available(self) -> None:
         desc = _build_spawn_description(
             "/bin/claude",

tests/test_spawner.py

@@ -167,6 +167,29 @@ def test_updates_pane_id(self, mock_subprocess: MagicMock, team_dir: Path) -> No
         found = [m for m in config.members if m.name == "researcher"]
         assert found[0].tmux_pane_id == "%42"
 
+    @patch("claude_teams.spawner.subprocess")
+    def test_should_use_new_window_when_enabled(
+        self,
+        mock_subprocess: MagicMock,
+        team_dir: Path,
+        monkeypatch,
+    ) -> None:
+        monkeypatch.setenv("USE_TMUX_WINDOWS", "0")
+        mock_subprocess.run.return_value.stdout = "@42\n"
+        member = spawn_teammate(
+            TEAM,
+            "window-worker",
+            "Do research",
+            "/usr/local/bin/claude",
+            SESSION_ID,
+            base_dir=team_dir,
+        )
+        assert member.tmux_pane_id == "@42"
+        call_args = mock_subprocess.run.call_args[0][0]
+        assert call_args[:5] == ["tmux", "new-window", "-dP", "-F", "#{window_id}"]
+        assert "-n" in call_args
+        assert call_args[call_args.index("-n") + 1] == "@claude-team | window-worker"
+
     @patch("claude_teams.spawner.subprocess.run")
     def test_should_rollback_member_when_tmux_spawn_fails(
         self, mock_run: MagicMock, team_dir: Path
@@ -197,6 +220,15 @@ def test_calls_subprocess(self, mock_subprocess: MagicMock) -> None:
             ["tmux", "kill-pane", "-t", "%99"], check=False
         )
 
+    @patch("claude_teams.spawner.subprocess")
+    def test_calls_kill_window_for_window_target(
+        self, mock_subprocess: MagicMock
+    ) -> None:
+        kill_tmux_pane("@99")
+        mock_subprocess.run.assert_called_once_with(
+            ["tmux", "kill-window", "-t", "@99"], check=False
+        )
+
 
 class TestBuildOpencodeAttachCommand:
     def test_should_contain_attach_with_session_and_dir(self) -> None: