Modal backend stubs

atropos/backends/modal_backend.py

@@ -0,0 +1,73 @@
+"""
+Modal tool backend (stub).
+
+We intentionally ship a placeholder implementation so AgentEnv can expose a
+backend switch without forcing Modal as a hard dependency for Hermes-Agent.
+
+When org access is available, this backend will be implemented by running a
+long-lived Modal worker (or pool) that owns N slots and exposes `execute_batch`.
+"""
+
+from __future__ import annotations
+
+from dataclasses import dataclass
+from typing import Any, Dict, List, Optional, Tuple
+
+from ..slots.executor import ExecutionResult
+from ..slots.slot import Slot
+from .base import ToolBackend
+
+
+@dataclass(frozen=True)
+class ModalBackendConfig:
+    # Placeholders for future implementation.
+    app_name: str = "atropos-sandbox"
+    function_name: str = "sandbox_server"
+    volume_name: Optional[str] = None
+    volume_mount_path: str = "/data"
+
+    @classmethod
+    def from_agent_env_config(cls, cfg: Any) -> "ModalBackendConfig":
+        return cls(
+            app_name=str(getattr(cfg, "modal_app_name", cls.app_name)),
+            function_name=str(getattr(cfg, "modal_function_name", cls.function_name)),
+            volume_name=(getattr(cfg, "modal_volume_name", None) or None),
+            volume_mount_path=str(getattr(cfg, "modal_volume_mount_path", cls.volume_mount_path)),
+        )
+
+
+class ModalToolBackend(ToolBackend):
+    def __init__(self, config: ModalBackendConfig):
+        self.config = config
+
+    @property
+    def default_timeout_s(self) -> Optional[float]:
+        return None
+
+    def _unavailable(self) -> RuntimeError:
+        return RuntimeError(
+            "Modal tool backend is not implemented yet. "
+            "Keep `--env.tool_pool_mode nomad` for now."
+        )
+
+    async def start(self) -> None:
+        raise self._unavailable()
+
+    async def stop(self, *, purge: bool = False) -> None:  # noqa: ARG002
+        # If start() isn't implemented, stop() is also unavailable.
+        raise self._unavailable()
+
+    async def acquire(self, trajectory_id: Optional[str] = None) -> Slot:  # noqa: ARG002
+        raise self._unavailable()
+
+    async def release(self, slot: Slot, *, reset_workspace: bool = False) -> None:  # noqa: ARG002
+        raise self._unavailable()
+
+    async def execute_batch(
+        self,
+        requests: List[Tuple[Slot, str, Dict[str, Any]]],
+        *,
+        timeout_s: Optional[float] = None,  # noqa: ARG002
+    ) -> List[ExecutionResult]:
+        raise self._unavailable()
+