diff --git a/lazarus/__init__.py b/lazarus/__init__.py
new file mode 100644
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+++ b/lazarus/__init__.py
@@ -0,0 +1 @@
+"""Lazarus Pit — Agent resurrection pool and mission cell isolation."""
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diff --git a/lazarus/cell.py b/lazarus/cell.py
new file mode 100644
index 00000000..1d428257
--- /dev/null
+++ b/lazarus/cell.py
@@ -0,0 +1,145 @@
+"""Mission cell lifecycle — create, load, save, destroy."""
+
+from __future__ import annotations
+
+import json
+import logging
+import os
+import tempfile
+from dataclasses import dataclass, field, asdict
+from datetime import datetime, timezone
+from pathlib import Path
+from typing import Literal
+
+log = logging.getLogger(__name__)
+
+CellState = Literal["pending", "active", "archived", "destroyed"]
+
+
+@dataclass
+class MissionCell:
+    """Represents a mission cell — an ephemeral project workspace."""
+
+    id: str
+    name: str
+    repo_url: str
+    created_at: str
+    state: CellState
+    agents: list[str]
+    cell_path: str
+    home_path: str
+
+    def to_dict(self) -> dict:
+        return {
+            "id": self.id,
+            "name": self.name,
+            "repo_url": self.repo_url,
+            "created_at": self.created_at,
+            "state": self.state,
+            "agents": list(self.agents),
+            "cell_path": self.cell_path,
+            "home_path": self.home_path,
+        }
+
+    @classmethod
+    def from_dict(cls, data: dict) -> MissionCell:
+        return cls(
+            id=data["id"],
+            name=data["name"],
+            repo_url=data["repo_url"],
+            created_at=data["created_at"],
+            state=data["state"],
+            agents=list(data.get("agents", [])),
+            cell_path=data["cell_path"],
+            home_path=data.get("home_path", ""),
+        )
+
+
+def create_cell(
+    mission_id: str,
+    name: str,
+    repo_url: str,
+    base_path: Path,
+    home_path: str = "",
+) -> MissionCell:
+    """Create a new mission cell directory structure and return a MissionCell."""
+    cell_path = base_path / mission_id
+    cell_path.mkdir(parents=True, exist_ok=True)
+
+    # Create required subdirectories
+    (cell_path / "workspace").mkdir(exist_ok=True)
+    (cell_path / "logs").mkdir(exist_ok=True)
+    (cell_path / "snapshots").mkdir(exist_ok=True)
+
+    created_at = datetime.now(timezone.utc).isoformat()
+
+    cell = MissionCell(
+        id=mission_id,
+        name=name,
+        repo_url=repo_url,
+        created_at=created_at,
+        state="pending",
+        agents=[],
+        cell_path=str(cell_path),
+        home_path=home_path,
+    )
+
+    # Write roster.json placeholder
+    roster_path = cell_path / "roster.json"
+    _atomic_write(roster_path, {"agents": []})
+
+    # Write cell.json
+    save_cell(cell)
+
+    log.info("Created mission cell %s at %s", mission_id, cell_path)
+    return cell
+
+
+def destroy_cell(cell: MissionCell, cleanup_dirs: bool = False) -> None:
+    """Mark a cell as destroyed and optionally remove its directories."""
+    cell.state = "destroyed"
+    save_cell(cell)
+
+    if cleanup_dirs:
+        import shutil
+        cell_dir = Path(cell.cell_path)
+        if cell_dir.exists():
+            shutil.rmtree(cell_dir)
+            log.info("Removed cell directory %s", cell_dir)
+
+    log.info("Destroyed mission cell %s", cell.id)
+
+
+def load_cell(cell_path: Path) -> MissionCell:
+    """Load a MissionCell from a cell.json file at cell_path."""
+    cell_json = Path(cell_path) / "cell.json"
+    with open(cell_json, "r", encoding="utf-8") as fh:
+        data = json.load(fh)
+    return MissionCell.from_dict(data)
+
+
+def save_cell(cell: MissionCell) -> None:
+    """Atomically save a MissionCell to cell.json in its cell_path."""
+    cell_path = Path(cell.cell_path)
+    cell_path.mkdir(parents=True, exist_ok=True)
+    target = cell_path / "cell.json"
+    _atomic_write(target, cell.to_dict())
+    log.debug("Saved cell %s to %s", cell.id, target)
+
+
+# ─── helpers ──────────────────────────────────────────────────────────────────
+
+def _atomic_write(path: Path, data: dict) -> None:
+    """Write JSON atomically via a temp file + rename."""
+    path.parent.mkdir(parents=True, exist_ok=True)
+    fd, tmp = tempfile.mkstemp(dir=path.parent, suffix=".tmp")
+    try:
+        with os.fdopen(fd, "w", encoding="utf-8") as fh:
+            json.dump(data, fh, indent=2)
+        os.replace(tmp, path)
+    except Exception:
+        try:
+            os.unlink(tmp)
+        except OSError:
+            pass
+        raise
diff --git a/lazarus/cli.py b/lazarus/cli.py
new file mode 100644
index 00000000..e996af4c
--- /dev/null
+++ b/lazarus/cli.py
@@ -0,0 +1,162 @@
+"""Lazarus CLI — invite agents, manage mission cells."""
+
+from __future__ import annotations
+
+import argparse
+import json
+import platform
+import sys
+import uuid
+from pathlib import Path
+
+from lazarus.cell import MissionCell, create_cell, load_cell
+from lazarus.isolation import setup_level1_isolation
+from lazarus.roster import DEFAULT_REGISTRY_PATH, MissionRoster
+
+
+def _default_base_path() -> Path:
+    if platform.system() == "Linux":
+        return Path("/var/missions")
+    return Path.home() / ".nexus" / "missions"
+
+
+# ─── command handlers ─────────────────────────────────────────────────────────
+
+
+def cmd_invite(args: argparse.Namespace) -> int:
+    """Create or load a mission cell and invite an agent."""
+    base_path = Path(args.base_path) if args.base_path else _default_base_path()
+    mission_id: str = args.mission or str(uuid.uuid4())
+    roster = MissionRoster(Path(args.registry) if args.registry else DEFAULT_REGISTRY_PATH)
+
+    # Create or load cell
+    cell_dir = base_path / mission_id
+    if (cell_dir / "cell.json").exists():
+        cell = load_cell(cell_dir)
+    else:
+        cell = create_cell(
+            mission_id=mission_id,
+            name=args.name or mission_id,
+            repo_url=args.repo,
+            base_path=base_path,
+        )
+
+    # Level 1 isolation
+    setup_level1_isolation(cell)
+
+    # Register mission and invite agent
+    roster.add_mission(cell)
+    entry = roster.invite_agent(mission_id, args.agent, role=args.role)
+    roster.save()
+
+    summary = {
+        "mission_id": mission_id,
+        "agent": args.agent,
+        "role": entry.role,
+        "status": entry.status,
+        "cell_path": cell.cell_path,
+        "repo_url": cell.repo_url,
+        "invited_at": entry.invited_at,
+    }
+    print(json.dumps(summary, indent=2))
+    return 0
+
+
+def cmd_list(args: argparse.Namespace) -> int:
+    """List missions, optionally filtered by state."""
+    roster = MissionRoster(Path(args.registry) if args.registry else DEFAULT_REGISTRY_PATH)
+    missions = roster.list_missions(state=args.state)
+    print(json.dumps(missions, indent=2))
+    return 0
+
+
+def cmd_status(args: argparse.Namespace) -> int:
+    """Show details of a specific mission."""
+    roster = MissionRoster(Path(args.registry) if args.registry else DEFAULT_REGISTRY_PATH)
+    mission = roster.get_mission(args.mission_id)
+    if mission is None:
+        print(f"Mission {args.mission_id!r} not found.", file=sys.stderr)
+        return 1
+    agents = roster.list_agents(args.mission_id)
+    output = dict(mission)
+    output["agent_count"] = len(agents)
+    output["agents"] = [a.to_dict() for a in agents]
+    print(json.dumps(output, indent=2))
+    return 0
+
+
+def cmd_depart(args: argparse.Namespace) -> int:
+    """Mark an agent as departed from a mission."""
+    roster = MissionRoster(Path(args.registry) if args.registry else DEFAULT_REGISTRY_PATH)
+    try:
+        entry = roster.depart_agent(args.mission, args.agent)
+    except KeyError as exc:
+        print(f"Error: {exc}", file=sys.stderr)
+        return 1
+    roster.save()
+    print(json.dumps(entry.to_dict(), indent=2))
+    return 0
+
+
+# ─── argument parsing ─────────────────────────────────────────────────────────
+
+
+def _build_parser() -> argparse.ArgumentParser:
+    parser = argparse.ArgumentParser(
+        prog="lazarus",
+        description="Lazarus Pit — agent invitation and mission cell management",
+    )
+    parser.add_argument(
+        "--registry",
+        default=None,
+        help="Path to mission roster JSON (default: ~/.nexus/mission-roster.json)",
+    )
+
+    sub = parser.add_subparsers(dest="command", required=True)
+
+    # invite
+    p_invite = sub.add_parser("invite", help="Invite an agent to a mission")
+    p_invite.add_argument("agent", help="Agent name to invite")
+    p_invite.add_argument("--mission", default=None, help="Mission ID (UUID generated if omitted)")
+    p_invite.add_argument("--repo", required=True, help="Repository URL for the mission")
+    p_invite.add_argument("--base-path", default=None, help="Base directory for mission cells")
+    p_invite.add_argument("--role", default="contributor", help="Agent role (default: contributor)")
+    p_invite.add_argument("--name", default=None, help="Human-readable mission name")
+
+    # list
+    p_list = sub.add_parser("list", help="List missions")
+    p_list.add_argument("--state", default=None, help="Filter by state (pending/active/archived/destroyed)")
+
+    # status
+    p_status = sub.add_parser("status", help="Show mission status")
+    p_status.add_argument("mission_id", help="Mission ID")
+
+    # depart
+    p_depart = sub.add_parser("depart", help="Mark agent as departed")
+    p_depart.add_argument("agent", help="Agent name")
+    p_depart.add_argument("--mission", required=True, help="Mission ID")
+
+    return parser
+
+
+def main(argv: list[str] | None = None) -> int:
+    parser = _build_parser()
+    args = parser.parse_args(argv)
+
+    dispatch = {
+        "invite": cmd_invite,
+        "list": cmd_list,
+        "status": cmd_status,
+        "depart": cmd_depart,
+    }
+
+    handler = dispatch.get(args.command)
+    if handler is None:
+        parser.print_help()
+        return 1
+
+    return handler(args)
+
+
+if __name__ == "__main__":
+    sys.exit(main())
diff --git a/lazarus/harness.py b/lazarus/harness.py
new file mode 100644
index 00000000..fba994cd
--- /dev/null
+++ b/lazarus/harness.py
@@ -0,0 +1,165 @@
+"""Hermes harness mission-cell mode — wraps agent lifecycle in a mission cell."""
+
+from __future__ import annotations
+
+import asyncio
+import json
+import logging
+import os
+from datetime import datetime, timezone
+from pathlib import Path
+from typing import Any, Awaitable
+
+try:
+    import websockets  # type: ignore[import]
+except ImportError:  # pragma: no cover
+    websockets = None  # type: ignore[assignment]
+
+from lazarus.cell import MissionCell, load_cell
+from lazarus.isolation import setup_level1_isolation
+
+log = logging.getLogger(__name__)
+
+DEFAULT_HERMES_WS_URL = "ws://localhost:8000/ws"
+
+
+class MissionCellHarness:
+    """
+    Wraps agent execution in a mission cell with Hermes WS telemetry.
+
+    Usage::
+
+        harness = MissionCellHarness("myagent", "/var/missions/<uuid>")
+        await harness.run_with_harness(my_coroutine())
+    """
+
+    def __init__(
+        self,
+        agent_name: str,
+        cell_path: str | Path,
+        hermes_ws_url: str = DEFAULT_HERMES_WS_URL,
+        home_path: str | None = None,
+    ) -> None:
+        self.agent_name = agent_name
+        self.cell_path = Path(cell_path)
+        self.hermes_ws_url = hermes_ws_url
+        self.home_path = home_path
+
+        self._cell: MissionCell | None = None
+        self._ws: Any = None  # websockets connection
+        self._ws_connected = False
+
+    # ─── public API ───────────────────────────────────────────────────────────
+
+    async def start(self) -> None:
+        """Load cell, set up isolation, emit agent_joined telemetry."""
+        self._cell = load_cell(self.cell_path)
+        setup_level1_isolation(self._cell)
+
+        await self._connect_hermes()
+        await self._emit_mission_event("agent_joined")
+        log.info(
+            "MissionCellHarness started for agent=%s mission=%s",
+            self.agent_name,
+            self._cell.id,
+        )
+
+    async def stop(self) -> None:
+        """Emit agent_departed telemetry and save state."""
+        await self._emit_mission_event("agent_departed")
+
+        if self._ws is not None:
+            try:
+                await self._ws.close()
+            except Exception as exc:
+                log.debug("WS close error (ignored): %s", exc)
+            self._ws_connected = False
+
+        log.info(
+            "MissionCellHarness stopped for agent=%s", self.agent_name
+        )
+
+    def get_env(self) -> dict[str, str]:
+        """Return environment variables for the mission cell context."""
+        cell = self._cell
+        env: dict[str, str] = {}
+
+        if cell:
+            env["MISSION_CELL_PATH"] = str(self.cell_path)
+            env["MISSION_ID"] = cell.id
+        else:
+            env["MISSION_CELL_PATH"] = str(self.cell_path)
+            env["MISSION_ID"] = ""
+
+        env["AGENT_NAME"] = self.agent_name
+
+        if self.home_path:
+            env["HOME"] = self.home_path
+        else:
+            env["HOME"] = os.environ.get("HOME", str(Path.home()))
+
+        return env
+
+    def write_mission_log(self, message: str) -> None:
+        """Write a timestamped log entry to the cell's logs directory."""
+        if self._cell is None:
+            log.warning("Cannot write mission log: cell not loaded")
+            return
+
+        logs_dir = Path(self._cell.cell_path) / "logs"
+        logs_dir.mkdir(parents=True, exist_ok=True)
+
+        log_file = logs_dir / "mission.log"
+        timestamp = datetime.now(timezone.utc).isoformat()
+        line = f"[{timestamp}] [{self.agent_name}] {message}\n"
+
+        with open(log_file, "a", encoding="utf-8") as fh:
+            fh.write(line)
+
+    async def run_with_harness(self, coro: Awaitable[Any]) -> Any:
+        """Start harness, run coro, stop harness. Returns coro result."""
+        await self.start()
+        try:
+            return await coro
+        finally:
+            await self.stop()
+
+    # ─── internals ────────────────────────────────────────────────────────────
+
+    async def _connect_hermes(self) -> None:
+        """Attempt WebSocket connection to Hermes; fail gracefully."""
+        try:
+            import websockets  # type: ignore[import]
+
+            self._ws = await websockets.connect(self.hermes_ws_url)
+            self._ws_connected = True
+            log.info("Connected to Hermes at %s", self.hermes_ws_url)
+        except Exception as exc:
+            log.warning("Could not connect to Hermes WS: %s", exc)
+            self._ws_connected = False
+
+    async def _emit_mission_event(self, event: str) -> None:
+        """Send a mission_event message to Hermes."""
+        cell = self._cell
+        mission_id = cell.id if cell else ""
+        payload = {
+            "type": "mission_event",
+            "event": event,
+            "mission_id": mission_id,
+            "agent_name": self.agent_name,
+            "timestamp": datetime.now(timezone.utc).isoformat(),
+        }
+
+        if self._ws_connected and self._ws is not None:
+            try:
+                await self._ws.send(json.dumps(payload))
+                log.debug("Emitted %s for agent=%s", event, self.agent_name)
+            except Exception as exc:
+                log.warning("Failed to emit %s telemetry: %s", event, exc)
+                self._ws_connected = False
+        else:
+            log.debug(
+                "Hermes not connected; %s event not sent (agent=%s)",
+                event,
+                self.agent_name,
+            )
diff --git a/lazarus/isolation.py b/lazarus/isolation.py
new file mode 100644
index 00000000..08490897
--- /dev/null
+++ b/lazarus/isolation.py
@@ -0,0 +1,170 @@
+"""Level 1 isolation — directory setup and AppArmor profile generation."""
+
+from __future__ import annotations
+
+import logging
+import platform
+import subprocess
+from dataclasses import dataclass
+from pathlib import Path
+
+from lazarus.cell import MissionCell
+
+log = logging.getLogger(__name__)
+
+_APPARMOR_TEMPLATE = """\
+#include <tunables/global>
+
+profile nexus-mission-{cell_id} flags=(attach_disconnected,mediate_deleted) {{
+  #include <abstractions/base>
+
+  # Allow read access to agent home
+  "{home_path}/" r,
+  "{home_path}/**" r,
+
+  # Allow read/write access to cell workspace
+  "{workspace_path}/" rw,
+  "{workspace_path}/**" rwkl,
+
+  # Allow read/write access to cell logs
+  "{logs_path}/" rw,
+  "{logs_path}/**" rwkl,
+
+  # Deny writes to home path
+  deny "{home_path}/**" w,
+
+  # Deny access to other agent home dirs
+  deny "/root/wizards/**" rw,
+
+  # Deny network access by default
+  deny network,
+
+  # Basic system access
+  /bin/** ix,
+  /usr/bin/** ix,
+  /lib/** r,
+  /usr/lib/** r,
+  /proc/self/** r,
+}}
+"""
+
+
+@dataclass
+class IsolationManifest:
+    """Result of setting up Level 1 isolation for a mission cell."""
+
+    cell_id: str
+    workspace_path: Path
+    logs_path: Path
+    apparmor_profile_path: Path | None
+    platform: str
+
+
+def setup_level1_isolation(cell: MissionCell) -> IsolationManifest:
+    """
+    Set up Level 1 isolation for a mission cell.
+
+    Creates the proper directory structure with permissions and writes
+    an AppArmor profile (Linux) or just a profile file (other platforms).
+
+    Returns an IsolationManifest describing what was set up.
+    """
+    cell_path = Path(cell.cell_path)
+    workspace_path = cell_path / "workspace"
+    logs_path = cell_path / "logs"
+
+    workspace_path.mkdir(parents=True, exist_ok=True)
+    logs_path.mkdir(parents=True, exist_ok=True)
+
+    # Set restrictive permissions on the workspace (owner-only)
+    try:
+        workspace_path.chmod(0o700)
+        logs_path.chmod(0o700)
+    except OSError as exc:
+        log.warning("Could not set directory permissions: %s", exc)
+
+    apparmor_profile_path: Path | None = None
+    sys_platform = platform.system()
+
+    if cell.home_path:
+        profile_path = cell_path / f"nexus-mission-{cell.id}.apparmor"
+        apparmor_profile_path = write_apparmor_profile(cell, profile_path)
+
+    log.info(
+        "Level 1 isolation set up for cell %s (platform=%s)", cell.id, sys_platform
+    )
+    return IsolationManifest(
+        cell_id=cell.id,
+        workspace_path=workspace_path,
+        logs_path=logs_path,
+        apparmor_profile_path=apparmor_profile_path,
+        platform=sys_platform,
+    )
+
+
+def write_apparmor_profile(cell: MissionCell, output_path: Path) -> Path:
+    """
+    Write an AppArmor profile for the mission cell to output_path.
+
+    On non-Linux platforms this just writes the file without attempting to load it.
+    Returns the path to the written profile.
+    """
+    cell_path = Path(cell.cell_path)
+    workspace_path = cell_path / "workspace"
+    logs_path = cell_path / "logs"
+    home_path = cell.home_path or str(Path.home())
+
+    profile_content = _APPARMOR_TEMPLATE.format(
+        cell_id=cell.id,
+        home_path=home_path,
+        workspace_path=str(workspace_path),
+        logs_path=str(logs_path),
+    )
+
+    output_path.parent.mkdir(parents=True, exist_ok=True)
+    output_path.write_text(profile_content, encoding="utf-8")
+    log.info("Wrote AppArmor profile to %s", output_path)
+    return output_path
+
+
+def load_apparmor_profile(profile_path: Path) -> bool:
+    """
+    Attempt to load an AppArmor profile via apparmor_parser.
+
+    On non-Linux platforms or when apparmor_parser is absent, this is a no-op
+    and returns False gracefully.
+
+    Returns True if the profile was loaded successfully.
+    """
+    if platform.system() != "Linux":
+        log.debug(
+            "AppArmor load skipped: not on Linux (platform=%s)", platform.system()
+        )
+        return False
+
+    try:
+        result = subprocess.run(
+            ["apparmor_parser", "-r", str(profile_path)],
+            capture_output=True,
+            text=True,
+            timeout=10,
+        )
+        if result.returncode == 0:
+            log.info("Loaded AppArmor profile from %s", profile_path)
+            return True
+        else:
+            log.warning(
+                "apparmor_parser failed (rc=%d): %s",
+                result.returncode,
+                result.stderr.strip(),
+            )
+            return False
+    except FileNotFoundError:
+        log.debug("apparmor_parser not found; skipping profile load")
+        return False
+    except subprocess.TimeoutExpired:
+        log.warning("apparmor_parser timed out loading %s", profile_path)
+        return False
+    except Exception as exc:
+        log.warning("Unexpected error loading AppArmor profile: %s", exc)
+        return False
diff --git a/lazarus/roster.py b/lazarus/roster.py
new file mode 100644
index 00000000..8eda453f
--- /dev/null
+++ b/lazarus/roster.py
@@ -0,0 +1,184 @@
+"""Mission roster registry — tracks all missions and agents."""
+
+from __future__ import annotations
+
+import json
+import logging
+import os
+import tempfile
+from dataclasses import dataclass
+from datetime import datetime, timezone
+from pathlib import Path
+from typing import Literal
+
+from lazarus.cell import MissionCell
+
+log = logging.getLogger(__name__)
+
+DEFAULT_REGISTRY_PATH = Path.home() / ".nexus" / "mission-roster.json"
+
+EntryStatus = Literal["invited", "active", "departed"]
+
+
+@dataclass
+class RosterEntry:
+    """An agent's participation record in a mission."""
+
+    mission_id: str
+    agent_name: str
+    invited_at: str
+    accepted_at: str | None
+    role: str
+    status: EntryStatus
+
+    def to_dict(self) -> dict:
+        return {
+            "mission_id": self.mission_id,
+            "agent_name": self.agent_name,
+            "invited_at": self.invited_at,
+            "accepted_at": self.accepted_at,
+            "role": self.role,
+            "status": self.status,
+        }
+
+    @classmethod
+    def from_dict(cls, data: dict) -> RosterEntry:
+        return cls(
+            mission_id=data["mission_id"],
+            agent_name=data["agent_name"],
+            invited_at=data["invited_at"],
+            accepted_at=data.get("accepted_at"),
+            role=data.get("role", "contributor"),
+            status=data["status"],
+        )
+
+
+class MissionRoster:
+    """Registry of all missions and their agent rosters."""
+
+    def __init__(self, registry_path: Path = DEFAULT_REGISTRY_PATH) -> None:
+        self.registry_path = Path(registry_path)
+        self._data: dict = {}
+        self._load()
+
+    # ─── internal I/O ─────────────────────────────────────────────────────────
+
+    def _load(self) -> None:
+        if self.registry_path.exists():
+            with open(self.registry_path, "r", encoding="utf-8") as fh:
+                self._data = json.load(fh)
+        else:
+            self._data = {"schema_version": "1", "missions": {}}
+
+    def save(self) -> None:
+        """Atomically persist the registry to disk."""
+        self.registry_path.parent.mkdir(parents=True, exist_ok=True)
+        fd, tmp = tempfile.mkstemp(dir=self.registry_path.parent, suffix=".tmp")
+        try:
+            with os.fdopen(fd, "w", encoding="utf-8") as fh:
+                json.dump(self._data, fh, indent=2)
+            os.replace(tmp, self.registry_path)
+        except Exception:
+            try:
+                os.unlink(tmp)
+            except OSError:
+                pass
+            raise
+        log.debug("Saved mission roster to %s", self.registry_path)
+
+    # ─── missions ─────────────────────────────────────────────────────────────
+
+    def add_mission(self, cell: MissionCell) -> None:
+        """Register a new mission from a MissionCell."""
+        missions: dict = self._data.setdefault("missions", {})
+        if cell.id not in missions:
+            missions[cell.id] = {
+                "id": cell.id,
+                "name": cell.name,
+                "repo_url": cell.repo_url,
+                "created_at": cell.created_at,
+                "state": cell.state,
+                "cell_path": cell.cell_path,
+                "agents": [],
+            }
+            log.info("Registered mission %s in roster", cell.id)
+        else:
+            log.debug("Mission %s already in roster, skipping add", cell.id)
+
+    def get_mission(self, mission_id: str) -> dict | None:
+        return self._data.get("missions", {}).get(mission_id)
+
+    def list_missions(self, state: str | None = None) -> list[dict]:
+        missions = list(self._data.get("missions", {}).values())
+        if state is not None:
+            missions = [m for m in missions if m.get("state") == state]
+        return missions
+
+    # ─── agents ───────────────────────────────────────────────────────────────
+
+    def invite_agent(
+        self,
+        mission_id: str,
+        agent_name: str,
+        role: str = "contributor",
+    ) -> RosterEntry:
+        """Invite an agent to a mission; returns the new RosterEntry."""
+        mission = self._require_mission(mission_id)
+        agents: list[dict] = mission.setdefault("agents", [])
+
+        # Check for existing entry
+        for entry_dict in agents:
+            if entry_dict["agent_name"] == agent_name:
+                log.warning(
+                    "Agent %s already in mission %s roster", agent_name, mission_id
+                )
+                return RosterEntry.from_dict(entry_dict)
+
+        entry = RosterEntry(
+            mission_id=mission_id,
+            agent_name=agent_name,
+            invited_at=datetime.now(timezone.utc).isoformat(),
+            accepted_at=None,
+            role=role,
+            status="invited",
+        )
+        agents.append(entry.to_dict())
+        log.info("Invited %s to mission %s as %s", agent_name, mission_id, role)
+        return entry
+
+    def accept_invitation(self, mission_id: str, agent_name: str) -> RosterEntry:
+        """Mark an invitation as accepted; status becomes 'active'."""
+        entry_dict = self._require_agent_entry(mission_id, agent_name)
+        entry_dict["status"] = "active"
+        entry_dict["accepted_at"] = datetime.now(timezone.utc).isoformat()
+        log.info("Agent %s accepted invitation to mission %s", agent_name, mission_id)
+        return RosterEntry.from_dict(entry_dict)
+
+    def depart_agent(self, mission_id: str, agent_name: str) -> RosterEntry:
+        """Mark an agent as departed from a mission."""
+        entry_dict = self._require_agent_entry(mission_id, agent_name)
+        entry_dict["status"] = "departed"
+        log.info("Agent %s departed mission %s", agent_name, mission_id)
+        return RosterEntry.from_dict(entry_dict)
+
+    def list_agents(self, mission_id: str) -> list[RosterEntry]:
+        """Return all RosterEntry objects for a mission."""
+        mission = self._require_mission(mission_id)
+        return [RosterEntry.from_dict(e) for e in mission.get("agents", [])]
+
+    # ─── helpers ──────────────────────────────────────────────────────────────
+
+    def _require_mission(self, mission_id: str) -> dict:
+        missions = self._data.get("missions", {})
+        if mission_id not in missions:
+            raise KeyError(f"Mission {mission_id!r} not found in roster")
+        return missions[mission_id]
+
+    def _require_agent_entry(self, mission_id: str, agent_name: str) -> dict:
+        mission = self._require_mission(mission_id)
+        for entry_dict in mission.get("agents", []):
+            if entry_dict["agent_name"] == agent_name:
+                return entry_dict
+        raise KeyError(
+            f"Agent {agent_name!r} not found in mission {mission_id!r} roster"
+        )
diff --git a/tests/test_lazarus_cell.py b/tests/test_lazarus_cell.py
new file mode 100644
index 00000000..8df7103c
--- /dev/null
+++ b/tests/test_lazarus_cell.py
@@ -0,0 +1,110 @@
+"""Tests for lazarus.cell — MissionCell lifecycle."""
+
+from __future__ import annotations
+
+import json
+import sys
+from pathlib import Path
+
+import pytest
+
+sys.path.insert(0, str(Path(__file__).parent.parent))
+
+from lazarus.cell import MissionCell, create_cell, destroy_cell, load_cell, save_cell
+
+
+def test_create_cell_creates_directories(tmp_path: Path) -> None:
+    """workspace/, logs/, and snapshots/ subdirs are created under the cell dir."""
+    cell = create_cell(
+        mission_id="test-mission-1",
+        name="Test Mission",
+        repo_url="https://github.com/test/repo",
+        base_path=tmp_path,
+    )
+
+    cell_dir = tmp_path / "test-mission-1"
+    assert cell_dir.is_dir()
+    assert (cell_dir / "workspace").is_dir()
+    assert (cell_dir / "logs").is_dir()
+    assert (cell_dir / "snapshots").is_dir()
+
+
+def test_create_cell_writes_cell_json(tmp_path: Path) -> None:
+    """cell.json is created and contains valid mission metadata."""
+    cell = create_cell(
+        mission_id="test-mission-2",
+        name="Another Mission",
+        repo_url="https://github.com/test/another",
+        base_path=tmp_path,
+    )
+
+    cell_json_path = tmp_path / "test-mission-2" / "cell.json"
+    assert cell_json_path.exists()
+
+    with open(cell_json_path) as fh:
+        data = json.load(fh)
+
+    assert data["id"] == "test-mission-2"
+    assert data["name"] == "Another Mission"
+    assert data["repo_url"] == "https://github.com/test/another"
+    assert data["state"] == "pending"
+    assert isinstance(data["agents"], list)
+
+
+def test_save_and_load_cell(tmp_path: Path) -> None:
+    """Round-trip: save a cell, load it back, fields match."""
+    cell = create_cell(
+        mission_id="roundtrip-mission",
+        name="Roundtrip",
+        repo_url="https://github.com/test/roundtrip",
+        base_path=tmp_path,
+    )
+    # Mutate and save
+    cell.state = "active"
+    cell.agents.append("agentA")
+    save_cell(cell)
+
+    loaded = load_cell(tmp_path / "roundtrip-mission")
+    assert loaded.id == "roundtrip-mission"
+    assert loaded.state == "active"
+    assert "agentA" in loaded.agents
+    assert loaded.repo_url == "https://github.com/test/roundtrip"
+
+
+def test_cell_state_transitions(tmp_path: Path) -> None:
+    """State changes are persisted correctly through save/load."""
+    cell = create_cell(
+        mission_id="state-mission",
+        name="State Test",
+        repo_url="https://github.com/test/state",
+        base_path=tmp_path,
+    )
+    assert cell.state == "pending"
+
+    cell.state = "active"
+    save_cell(cell)
+
+    reloaded = load_cell(tmp_path / "state-mission")
+    assert reloaded.state == "active"
+
+    reloaded.state = "archived"
+    save_cell(reloaded)
+
+    final = load_cell(tmp_path / "state-mission")
+    assert final.state == "archived"
+
+
+def test_destroy_cell_marks_destroyed(tmp_path: Path) -> None:
+    """destroy_cell sets state to 'destroyed' and persists it."""
+    cell = create_cell(
+        mission_id="destroy-mission",
+        name="Destroy Test",
+        repo_url="https://github.com/test/destroy",
+        base_path=tmp_path,
+    )
+
+    destroy_cell(cell, cleanup_dirs=False)
+    assert cell.state == "destroyed"
+
+    reloaded = load_cell(tmp_path / "destroy-mission")
+    assert reloaded.state == "destroyed"
diff --git a/tests/test_lazarus_cli.py b/tests/test_lazarus_cli.py
new file mode 100644
index 00000000..5c65874b
--- /dev/null
+++ b/tests/test_lazarus_cli.py
@@ -0,0 +1,136 @@
+"""Tests for lazarus.cli — CLI commands."""
+
+from __future__ import annotations
+
+import json
+import sys
+from pathlib import Path
+from unittest.mock import MagicMock, patch
+
+import pytest
+
+sys.path.insert(0, str(Path(__file__).parent.parent))
+
+from lazarus.cli import main
+from lazarus.roster import MissionRoster
+
+
+def _run(argv: list[str], tmp_path: Path, capsys: pytest.CaptureFixture) -> tuple:
+    """Helper: run CLI with a tmp registry and capture stdout as JSON.
+
+    Prepends --registry before the subcommand so argparse sees it as a global arg.
+    """
+    registry = str(tmp_path / "roster.json")
+    rc = main(["--registry", registry, *argv])
+    out = capsys.readouterr().out
+    return json.loads(out), rc
+
+
+# Patch setup_level1_isolation globally for all CLI tests to avoid permission issues
+@pytest.fixture(autouse=True)
+def no_isolation():
+    with patch("lazarus.cli.setup_level1_isolation"):
+        yield
+
+
+def test_invite_creates_mission_cell(tmp_path: Path, capsys: pytest.CaptureFixture) -> None:
+    """invite creates a mission cell directory with cell.json."""
+    base = str(tmp_path / "missions")
+    result, rc = _run(
+        [
+            "invite", "agentAlpha",
+            "--repo", "https://github.com/test/repo",
+            "--base-path", base,
+        ],
+        tmp_path,
+        capsys,
+    )
+    assert rc == 0
+    mission_id = result["mission_id"]
+    cell_json = tmp_path / "missions" / mission_id / "cell.json"
+    assert cell_json.exists()
+
+
+def test_invite_adds_agent_to_roster(tmp_path: Path, capsys: pytest.CaptureFixture) -> None:
+    """After invite, the agent appears in the roster with status 'invited'."""
+    base = str(tmp_path / "missions")
+    registry = str(tmp_path / "roster.json")
+
+    rc = main([
+        "--registry", registry,
+        "invite", "agentBeta",
+        "--repo", "https://github.com/test/repo",
+        "--base-path", base,
+    ])
+    out = capsys.readouterr().out
+    result = json.loads(out)
+    assert rc == 0
+
+    roster = MissionRoster(Path(registry))
+    agents = roster.list_agents(result["mission_id"])
+    agent_names = [a.agent_name for a in agents]
+    assert "agentBeta" in agent_names
+
+
+def test_list_shows_missions(tmp_path: Path, capsys: pytest.CaptureFixture) -> None:
+    """list command shows missions that were previously created via invite."""
+    base = str(tmp_path / "missions")
+    registry = str(tmp_path / "roster.json")
+
+    # Create a mission first
+    main(["--registry", registry, "invite", "agentGamma",
+          "--repo", "https://github.com/test/repo", "--base-path", base])
+    capsys.readouterr()  # discard invite output
+
+    rc = main(["--registry", registry, "list"])
+    out = capsys.readouterr().out
+    missions = json.loads(out)
+
+    assert rc == 0
+    assert isinstance(missions, list)
+    assert len(missions) >= 1
+
+
+def test_status_shows_agents(tmp_path: Path, capsys: pytest.CaptureFixture) -> None:
+    """status command shows agent count for a mission."""
+    base = str(tmp_path / "missions")
+    registry = str(tmp_path / "roster.json")
+
+    main(["--registry", registry, "invite", "agentDelta",
+          "--repo", "https://github.com/test/repo", "--base-path", base])
+    invite_out = json.loads(capsys.readouterr().out)
+    mission_id = invite_out["mission_id"]
+
+    rc = main(["--registry", registry, "status", mission_id])
+    out = capsys.readouterr().out
+    status = json.loads(out)
+
+    assert rc == 0
+    assert status["agent_count"] >= 1
+    agent_names = [a["agent_name"] for a in status["agents"]]
+    assert "agentDelta" in agent_names
+
+
+def test_depart_updates_agent_status(tmp_path: Path, capsys: pytest.CaptureFixture) -> None:
+    """depart command marks an agent's status as 'departed'."""
+    base = str(tmp_path / "missions")
+    registry = str(tmp_path / "roster.json")
+
+    main(["--registry", registry, "invite", "agentEpsilon",
+          "--repo", "https://github.com/test/repo", "--base-path", base])
+    invite_out = json.loads(capsys.readouterr().out)
+    mission_id = invite_out["mission_id"]
+
+    rc = main(["--registry", registry, "depart", "agentEpsilon",
+               "--mission", mission_id])
+    out = capsys.readouterr().out
+    result = json.loads(out)
+
+    assert rc == 0
+    assert result["status"] == "departed"
+
+    # Verify persisted
+    roster = MissionRoster(Path(registry))
+    agents = roster.list_agents(mission_id)
+    epsilon = next(a for a in agents if a.agent_name == "agentEpsilon")
+    assert epsilon.status == "departed"
diff --git a/tests/test_lazarus_harness.py b/tests/test_lazarus_harness.py
new file mode 100644
index 00000000..6cc19052
--- /dev/null
+++ b/tests/test_lazarus_harness.py
@@ -0,0 +1,141 @@
+"""Tests for lazarus.harness — MissionCellHarness."""
+
+from __future__ import annotations
+
+import asyncio
+import json
+import sys
+from pathlib import Path
+from unittest.mock import AsyncMock, MagicMock, patch
+
+import pytest
+
+sys.path.insert(0, str(Path(__file__).parent.parent))
+
+from lazarus.cell import create_cell, save_cell
+from lazarus.harness import MissionCellHarness
+
+pytestmark = pytest.mark.asyncio
+
+
+def _make_cell_and_harness(
+    tmp_path: Path,
+    agent_name: str = "testAgent",
+) -> tuple[object, MissionCellHarness]:
+    cell = create_cell(
+        mission_id="harness-test-001",
+        name="Harness Test",
+        repo_url="https://github.com/test/repo",
+        base_path=tmp_path / "cells",
+    )
+    harness = MissionCellHarness(
+        agent_name=agent_name,
+        cell_path=Path(cell.cell_path),
+        hermes_ws_url="ws://localhost:8000/ws",
+    )
+    return cell, harness
+
+
+def test_harness_get_env_includes_cell_path(tmp_path: Path) -> None:
+    """get_env() returns a dict that includes MISSION_CELL_PATH and AGENT_NAME."""
+    cell, harness = _make_cell_and_harness(tmp_path)
+
+    # Load cell manually so get_env works without start()
+    from lazarus.cell import load_cell
+    harness._cell = load_cell(Path(cell.cell_path))
+
+    env = harness.get_env()
+    assert "MISSION_CELL_PATH" in env
+    assert env["MISSION_CELL_PATH"] == str(Path(cell.cell_path))
+    assert env["AGENT_NAME"] == "testAgent"
+    assert "MISSION_ID" in env
+    assert "HOME" in env
+
+
+def test_harness_get_env_uses_custom_home(tmp_path: Path) -> None:
+    """When home_path is provided, HOME in env equals that path."""
+    cell, _ = _make_cell_and_harness(tmp_path)
+    custom_home = str(tmp_path / "wizard_home")
+    harness = MissionCellHarness(
+        agent_name="agentX",
+        cell_path=Path(cell.cell_path),
+        home_path=custom_home,
+    )
+
+    from lazarus.cell import load_cell
+    harness._cell = load_cell(Path(cell.cell_path))
+
+    env = harness.get_env()
+    assert env["HOME"] == custom_home
+
+
+def test_harness_write_mission_log(tmp_path: Path) -> None:
+    """write_mission_log creates a log file in the cell's logs/ directory."""
+    cell, harness = _make_cell_and_harness(tmp_path)
+
+    from lazarus.cell import load_cell
+    harness._cell = load_cell(Path(cell.cell_path))
+
+    harness.write_mission_log("Hello from test")
+
+    log_file = Path(cell.cell_path) / "logs" / "mission.log"
+    assert log_file.exists()
+    content = log_file.read_text()
+    assert "Hello from test" in content
+    assert "testAgent" in content
+
+
+async def test_harness_start_emits_telemetry(tmp_path: Path) -> None:
+    """start() emits an agent_joined mission_event via WebSocket."""
+    cell, harness = _make_cell_and_harness(tmp_path)
+
+    mock_ws = AsyncMock()
+    mock_ws.send = AsyncMock()
+    mock_ws.close = AsyncMock()
+
+    sent_messages = []
+
+    async def capture_send(payload: str) -> None:
+        sent_messages.append(json.loads(payload))
+
+    mock_ws.send.side_effect = capture_send
+
+    with patch("lazarus.isolation.setup_level1_isolation"):
+        with patch("lazarus.harness.setup_level1_isolation"):
+            with patch("lazarus.harness.websockets") as mock_websockets:
+                mock_websockets.connect = AsyncMock(return_value=mock_ws)
+                harness._ws_connected = False
+
+                await harness.start()
+
+    assert any(
+        m.get("event") == "agent_joined" and m.get("type") == "mission_event"
+        for m in sent_messages
+    ), f"Expected agent_joined event; got: {sent_messages}"
+
+
+async def test_harness_stop_emits_departure_telemetry(tmp_path: Path) -> None:
+    """stop() emits an agent_departed mission_event via WebSocket."""
+    cell, harness = _make_cell_and_harness(tmp_path)
+
+    from lazarus.cell import load_cell
+    harness._cell = load_cell(Path(cell.cell_path))
+
+    mock_ws = AsyncMock()
+    mock_ws.close = AsyncMock()
+
+    sent_messages = []
+
+    async def capture_send(payload: str) -> None:
+        sent_messages.append(json.loads(payload))
+
+    mock_ws.send = AsyncMock(side_effect=capture_send)
+    harness._ws = mock_ws
+    harness._ws_connected = True
+
+    await harness.stop()
+
+    assert any(
+        m.get("event") == "agent_departed"
+        for m in sent_messages
+    ), f"Expected agent_departed event; got: {sent_messages}"
diff --git a/tests/test_lazarus_isolation.py b/tests/test_lazarus_isolation.py
new file mode 100644
index 00000000..fd992e25
--- /dev/null
+++ b/tests/test_lazarus_isolation.py
@@ -0,0 +1,107 @@
+"""Tests for lazarus.isolation — Level 1 isolation setup."""
+
+from __future__ import annotations
+
+import sys
+from pathlib import Path
+from unittest.mock import MagicMock, patch
+
+import pytest
+
+sys.path.insert(0, str(Path(__file__).parent.parent))
+
+from lazarus.cell import create_cell
+from lazarus.isolation import (
+    IsolationManifest,
+    load_apparmor_profile,
+    setup_level1_isolation,
+    write_apparmor_profile,
+)
+
+
+def _make_cell(tmp_path: Path, home_path: str = "") -> object:
+    return create_cell(
+        mission_id="iso-test-001",
+        name="Isolation Test",
+        repo_url="https://github.com/test/repo",
+        base_path=tmp_path / "cells",
+        home_path=home_path,
+    )
+
+
+def test_setup_isolation_creates_workspace(tmp_path: Path) -> None:
+    """setup_level1_isolation creates workspace and logs dirs."""
+    cell = _make_cell(tmp_path)
+    manifest = setup_level1_isolation(cell)
+
+    assert manifest.workspace_path.is_dir()
+    assert manifest.logs_path.is_dir()
+    assert isinstance(manifest, IsolationManifest)
+    assert manifest.cell_id == cell.id
+
+
+def test_write_apparmor_profile_creates_file(tmp_path: Path) -> None:
+    """write_apparmor_profile writes a file at the given output path."""
+    cell = _make_cell(tmp_path, home_path=str(tmp_path / "home" / "agentX"))
+    output_path = tmp_path / "test.apparmor"
+
+    result_path = write_apparmor_profile(cell, output_path)
+    assert result_path == output_path
+    assert output_path.exists()
+    assert output_path.stat().st_size > 0
+
+
+def test_apparmor_profile_content(tmp_path: Path) -> None:
+    """Profile file contains correct cell ID, workspace, logs, and home paths."""
+    home = str(tmp_path / "home" / "agentX")
+    cell = _make_cell(tmp_path, home_path=home)
+    output_path = tmp_path / "test.apparmor"
+
+    write_apparmor_profile(cell, output_path)
+    content = output_path.read_text()
+
+    assert cell.id in content
+    assert "nexus-mission-" in content
+    assert "workspace" in content
+    assert "logs" in content
+    assert home in content
+    # Deny write to home
+    assert "deny" in content
+
+
+def test_load_apparmor_profile_noop_on_no_apparmor(tmp_path: Path) -> None:
+    """load_apparmor_profile returns False gracefully when apparmor_parser is absent."""
+    profile_path = tmp_path / "dummy.apparmor"
+    profile_path.write_text("# fake profile\n")
+
+    # Simulate apparmor_parser not found (FileNotFoundError from subprocess.run)
+    with patch("lazarus.isolation.platform.system", return_value="Linux"):
+        with patch(
+            "lazarus.isolation.subprocess.run",
+            side_effect=FileNotFoundError("apparmor_parser not found"),
+        ):
+            result = load_apparmor_profile(profile_path)
+
+    assert result is False
+
+
+def test_load_apparmor_profile_noop_on_non_linux(tmp_path: Path) -> None:
+    """load_apparmor_profile returns False on non-Linux platforms."""
+    profile_path = tmp_path / "dummy.apparmor"
+    profile_path.write_text("# fake profile\n")
+
+    with patch("lazarus.isolation.platform.system", return_value="Darwin"):
+        result = load_apparmor_profile(profile_path)
+
+    assert result is False
+
+
+def test_setup_isolation_writes_profile_when_home_path_set(tmp_path: Path) -> None:
+    """When home_path is set, setup_level1_isolation writes an AppArmor profile."""
+    home = str(tmp_path / "home" / "agentZ")
+    cell = _make_cell(tmp_path, home_path=home)
+
+    manifest = setup_level1_isolation(cell)
+
+    assert manifest.apparmor_profile_path is not None
+    assert manifest.apparmor_profile_path.exists()
diff --git a/tests/test_lazarus_roster.py b/tests/test_lazarus_roster.py
new file mode 100644
index 00000000..bfa28341
--- /dev/null
+++ b/tests/test_lazarus_roster.py
@@ -0,0 +1,122 @@
+"""Tests for lazarus.roster — MissionRoster registry."""
+
+from __future__ import annotations
+
+import json
+import sys
+from pathlib import Path
+
+import pytest
+
+sys.path.insert(0, str(Path(__file__).parent.parent))
+
+from lazarus.cell import create_cell
+from lazarus.roster import MissionRoster
+
+
+def _make_roster(tmp_path: Path) -> MissionRoster:
+    return MissionRoster(registry_path=tmp_path / "roster.json")
+
+
+def _make_cell(tmp_path: Path, mission_id: str = "m-001") -> object:
+    return create_cell(
+        mission_id=mission_id,
+        name="Test Mission",
+        repo_url="https://github.com/test/repo",
+        base_path=tmp_path / "cells",
+    )
+
+
+def test_add_mission_and_invite(tmp_path: Path) -> None:
+    """Can add a mission and invite an agent to it."""
+    roster = _make_roster(tmp_path)
+    cell = _make_cell(tmp_path)
+
+    roster.add_mission(cell)
+    entry = roster.invite_agent(cell.id, "agentA", role="contributor")
+
+    assert entry.agent_name == "agentA"
+    assert entry.status == "invited"
+    assert entry.role == "contributor"
+    assert entry.accepted_at is None
+
+
+def test_accept_invitation(tmp_path: Path) -> None:
+    """Accepting an invitation changes status from 'invited' to 'active'."""
+    roster = _make_roster(tmp_path)
+    cell = _make_cell(tmp_path)
+
+    roster.add_mission(cell)
+    roster.invite_agent(cell.id, "agentB")
+    entry = roster.accept_invitation(cell.id, "agentB")
+
+    assert entry.status == "active"
+    assert entry.accepted_at is not None
+
+
+def test_depart_agent(tmp_path: Path) -> None:
+    """Departing changes status to 'departed'."""
+    roster = _make_roster(tmp_path)
+    cell = _make_cell(tmp_path)
+
+    roster.add_mission(cell)
+    roster.invite_agent(cell.id, "agentC")
+    roster.accept_invitation(cell.id, "agentC")
+    entry = roster.depart_agent(cell.id, "agentC")
+
+    assert entry.status == "departed"
+
+
+def test_list_missions_filtered_by_state(tmp_path: Path) -> None:
+    """list_missions(state=...) filters correctly."""
+    roster = _make_roster(tmp_path)
+    cell1 = _make_cell(tmp_path, "m-001")
+    cell2 = _make_cell(tmp_path, "m-002")
+
+    roster.add_mission(cell1)
+    roster.add_mission(cell2)
+
+    # Both are 'pending' by default
+    pending = roster.list_missions(state="pending")
+    assert len(pending) == 2
+
+    # No active missions yet
+    active = roster.list_missions(state="active")
+    assert len(active) == 0
+
+
+def test_roster_persistence(tmp_path: Path) -> None:
+    """Save and reload the roster file; data survives the round-trip."""
+    registry_path = tmp_path / "roster.json"
+    roster = MissionRoster(registry_path=registry_path)
+    cell = _make_cell(tmp_path)
+
+    roster.add_mission(cell)
+    roster.invite_agent(cell.id, "agentD", role="lead")
+    roster.save()
+
+    # Load fresh from disk
+    roster2 = MissionRoster(registry_path=registry_path)
+    mission = roster2.get_mission(cell.id)
+    assert mission is not None
+    assert mission["id"] == cell.id
+
+    agents = roster2.list_agents(cell.id)
+    assert len(agents) == 1
+    assert agents[0].agent_name == "agentD"
+    assert agents[0].role == "lead"
+    assert agents[0].status == "invited"
+
+
+def test_list_agents(tmp_path: Path) -> None:
+    """list_agents returns all agents for a given mission."""
+    roster = _make_roster(tmp_path)
+    cell = _make_cell(tmp_path)
+
+    roster.add_mission(cell)
+    roster.invite_agent(cell.id, "alice")
+    roster.invite_agent(cell.id, "bob")
+
+    agents = roster.list_agents(cell.id)
+    names = {a.agent_name for a in agents}
+    assert names == {"alice", "bob"}