initial commit after one day coding agent session

src/mcp_forge/execution/__init__.py

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+"""Execution backends for running code in containers."""

src/mcp_forge/execution/jupyter/__init__.py

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+"""Jupyter-based stateful execution backend."""
+
+from .kernel import JupyterKernelManager, KernelInfo, KernelError
+from .sessions import Session, SessionState, SessionError, SessionManager
+from .backend import JupyterBackend
+
+__all__ = [
+    "JupyterKernelManager", 
+    "KernelInfo", 
+    "KernelError",
+    "Session",
+    "SessionState", 
+    "SessionError",
+    "SessionManager",
+    "JupyterBackend"
+]

src/mcp_forge/execution/jupyter/backend.py

@@ -0,0 +1,257 @@
+"""Jupyter backend for stateful code execution."""
+
+from typing import Optional, Dict, List
+import hashlib
+
+from mcp_forge.config.schema import ForgeConfig
+from mcp_forge.podman.containers import SecureContainerManager
+from mcp_forge.security.audit import AuditLogger, AuditEventType, AuditSeverity
+from mcp_forge.security.resource_limits import ResourceLimits, parse_memory_string
+from mcp_forge.execution.simple.executor import ExecutionResult
+from mcp_forge.execution.jupyter.kernel import JupyterKernelManager
+from mcp_forge.execution.jupyter.sessions import SessionManager, SessionState, SessionError
+
+
+class JupyterBackend:
+    """Stateful code execution backend using Jupyter kernels."""
+    
+    def __init__(
+        self,
+        config: ForgeConfig,
+        container_manager: SecureContainerManager,
+        audit_logger: AuditLogger
+    ):
+        """
+        Initialize Jupyter backend.
+        
+        Args:
+            config: Forge configuration
+            container_manager: Container lifecycle manager
+            audit_logger: Audit logging instance
+        """
+        self.config = config
+        self.container_manager = container_manager
+        self.audit_logger = audit_logger
+        
+        # Initialize kernel manager
+        kernel_manager = JupyterKernelManager(
+            container_manager=container_manager,
+            image=config.images.jupyter,
+            resource_limits=self._default_resource_limits()
+        )
+        
+        # Initialize session manager
+        self.session_manager = SessionManager(
+            config=config.sessions,
+            kernel_manager=kernel_manager,
+            audit_logger=audit_logger
+        )
+    
+    def execute(
+        self,
+        code: str,
+        session_id: str,
+        timeout: Optional[int] = None,
+        memory: Optional[str] = None,
+        cpu_quota: Optional[int] = None,
+        custom_image: Optional[str] = None,
+        volumes: Optional[Dict[str, dict]] = None
+    ) -> ExecutionResult:
+        """
+        Execute code in stateful session.
+        
+        Creates session if it doesn't exist, reuses existing session otherwise.
+        Session maintains namespace state across multiple executions.
+        
+        Args:
+            code: Python code to execute
+            session_id: Unique session identifier
+            timeout: Max execution time in seconds (uses config default if None)
+            memory: Memory limit string (uses config default if None)
+            cpu_quota: CPU quota (uses config default if None)
+            custom_image: Custom image name (uses config default if None)
+            volumes: Volume mounts dict
+        
+        Returns:
+            ExecutionResult with execution output and metadata
+        
+        Raises:
+            ValueError: If limits exceed configured maximums
+            SessionError: If session operation fails
+        """
+        # Use defaults from config if not specified
+        timeout = timeout if timeout is not None else self.config.execution.default_timeout
+        memory = memory if memory is not None else self.config.execution.default_memory
+        cpu_quota = cpu_quota if cpu_quota is not None else self.config.execution.default_cpu_quota
+        
+        # Validate limits against maximums
+        self._validate_limits(timeout, memory, cpu_quota)
+        
+        # Log execution (hash code, don't log actual content)
+        code_hash = hashlib.sha256(code.encode()).hexdigest()
+        self.audit_logger.log(
+            event_type=AuditEventType.EXECUTION_REQUEST,
+            severity=AuditSeverity.INFO,
+            message="Stateful code execution requested",
+            session_id=session_id,
+            details={
+                "code_hash": code_hash,
+                "timeout": timeout,
+                "memory": memory,
+                "cpu_quota": cpu_quota
+            }
+        )
+        
+        # Check if session exists, create if needed
+        try:
+            self.session_manager.get_session(session_id)
+        except SessionError:
+            # Session doesn't exist, create it
+            resource_limits = ResourceLimits(
+                memory=memory,
+                cpu_quota=cpu_quota,
+                storage="1g",  # Default storage quota
+                timeout=timeout
+            )
+            
+            self.session_manager.create_session(
+                session_id=session_id,
+                resource_limits=resource_limits,
+                volumes=volumes
+            )
+        
+        # Execute in session
+        result = self.session_manager.execute_in_session(
+            session_id=session_id,
+            code=code,
+            timeout=timeout
+        )
+        
+        return result
+    
+    def document_state(
+        self,
+        session_id: str,
+        variables: Dict[str, str],
+        note: str = "",
+        clear: bool = False
+    ) -> dict:
+        """
+        Document important variables in session.
+        
+        Args:
+            session_id: Session to document
+            variables: Dictionary of variable_name -> description
+            note: Optional note about session state
+            clear: If True, replace all documented variables; if False, merge
+        
+        Returns:
+            Dictionary with updated state info
+        
+        Raises:
+            SessionError: If session doesn't exist
+        """
+        self.session_manager.document_state(
+            session_id=session_id,
+            variables=variables,
+            note=note,
+            clear=clear
+        )
+        
+        # Return updated state
+        state = self.session_manager.get_session_state(session_id)
+        return state.to_dict()
+    
+    def get_session_state(self, session_id: str) -> SessionState:
+        """
+        Get documented state for session.
+        
+        Args:
+            session_id: Session identifier
+        
+        Returns:
+            SessionState object
+        
+        Raises:
+            SessionError: If session doesn't exist
+        """
+        return self.session_manager.get_session_state(session_id)
+    
+    def destroy_session(self, session_id: str) -> None:
+        """
+        Destroy session and cleanup kernel.
+        
+        Args:
+            session_id: Session to destroy
+        
+        Raises:
+            SessionError: If session doesn't exist
+        """
+        self.session_manager.destroy_session(session_id)
+    
+    def list_sessions(self) -> List[dict]:
+        """
+        List all active sessions with metadata.
+        
+        Returns:
+            List of session dictionaries
+        """
+        return self.session_manager.list_sessions()
+    
+    def cleanup_idle_sessions(self) -> int:
+        """
+        Cleanup sessions idle beyond configured timeout.
+        
+        Returns:
+            Number of sessions cleaned up
+        """
+        return self.session_manager.cleanup_idle_sessions()
+    
+    def _default_resource_limits(self) -> Optional[ResourceLimits]:
+        """
+        Get default resource limits from config.
+        
+        Returns:
+            ResourceLimits with config defaults, or None if enforcement disabled
+        """
+        if not self.config.security.enforce_resource_limits:
+            return None
+        
+        return ResourceLimits(
+            memory=self.config.execution.default_memory,
+            cpu_quota=self.config.execution.default_cpu_quota,
+            storage="1g",
+            timeout=self.config.execution.default_timeout
+        )
+    
+    def _validate_limits(self, timeout: int, memory: str, cpu_quota: int) -> None:
+        """
+        Validate resource limits against configured maximums.
+        
+        Args:
+            timeout: Timeout in seconds
+            memory: Memory limit string
+            cpu_quota: CPU quota value
+        
+        Raises:
+            ValueError: If any limit exceeds maximum
+        """
+        # Validate timeout
+        if timeout > self.config.execution.max_timeout:
+            raise ValueError(
+                f"Timeout {timeout} exceeds maximum {self.config.execution.max_timeout}"
+            )
+        
+        # Validate memory
+        memory_bytes = parse_memory_string(memory)
+        max_memory_bytes = parse_memory_string(self.config.execution.max_memory)
+        if memory_bytes > max_memory_bytes:
+            raise ValueError(
+                f"Memory {memory} exceeds maximum {self.config.execution.max_memory}"
+            )
+        
+        # Validate CPU quota
+        if cpu_quota > self.config.execution.max_cpu_quota:
+            raise ValueError(
+                f"CPU quota {cpu_quota} exceeds maximum {self.config.execution.max_cpu_quota}"
+            )

src/mcp_forge/execution/jupyter/kernel.py

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+"""Jupyter kernel management for stateful execution."""
+
+from typing import Dict, Optional, List, Any
+from dataclasses import dataclass, field
+from datetime import datetime, timedelta
+import uuid
+import json
+import sys
+import io
+
+from mcp_forge.podman.containers import SecureContainerManager, ContainerConfig
+from mcp_forge.security.resource_limits import ResourceLimits
+from mcp_forge.execution.simple.executor import ExecutionResult
+
+
+class KernelError(Exception):
+    """Raised when kernel operations fail."""
+    pass
+
+
+@dataclass
+class KernelInfo:
+    """Information about a running kernel."""
+    kernel_id: str
+    container_id: str
+    session_id: str
+    started_at: datetime
+    last_activity: datetime
+    namespace: Dict[str, Any] = field(default_factory=dict)
+    
+    def to_dict(self) -> dict:
+        """Convert to dictionary for JSON serialization."""
+        return {
+            "kernel_id": self.kernel_id,
+            "container_id": self.container_id,
+            "session_id": self.session_id,
+            "started_at": self.started_at.isoformat(),
+            "last_activity": self.last_activity.isoformat(),
+        }
+
+
+class JupyterKernelManager:
+    """
+    Manages IPython kernels in containers for stateful execution.
+    
+    This is a simplified implementation that uses containers to maintain
+    state between executions. Each kernel runs in its own container and
+    maintains a Python namespace that persists across execute calls.
+    """
+    
+    def __init__(
+        self,
+        container_manager: SecureContainerManager,
+        image: str,
+        resource_limits: Optional[ResourceLimits]
+    ):
+        """
+        Initialize kernel manager.
+        
+        Args:
+            container_manager: Container lifecycle manager
+            image: Docker/Podman image with Python/IPython
+            resource_limits: Default resource limits for kernels (None to disable) (None to disable)
+        """
+        self.container_manager = container_manager
+        self.image = image
+        self.resource_limits = resource_limits
+        self.kernels: Dict[str, KernelInfo] = {}
+    
+    def start_kernel(
+        self,
+        session_id: str,
+        volumes: Optional[Dict[str, dict]] = None
+    ) -> str:
+        """
+        Start a new kernel in a container.
+        
+        Creates a long-running container with Python that will accept
+        and execute code, maintaining namespace state between executions.
+        
+        Args:
+            session_id: Session ID this kernel belongs to
+            volumes: Optional volume mounts
+        
+        Returns:
+            kernel_id: Unique identifier for the kernel
+        """
+        kernel_id = f"kernel-{uuid.uuid4().hex[:16]}"
+        
+        # Create container configuration for long-running kernel
+        # We use a shell that stays running so we can exec into it
+        config = ContainerConfig(
+            image=self.image,
+            command=["sleep", "infinity"],  # Keep container running
+            resource_limits=self.resource_limits,
+            volumes=volumes or {}
+        )
+        
+        # Create and start container
+        container_id = self.container_manager.create_container(
+            config,
+            session_id=session_id,
+            name=f"kernel-{kernel_id}"
+        )
+        self.container_manager.start_container(container_id)
+        
+        # Register kernel
+        now = datetime.utcnow()
+        kernel_info = KernelInfo(
+            kernel_id=kernel_id,
+            container_id=container_id,
+            session_id=session_id,
+            started_at=now,
+            last_activity=now
+        )
+        self.kernels[kernel_id] = kernel_info
+        
+        return kernel_id
+    
+    def execute_code(
+        self,
+        kernel_id: str,
+        code: str,
+        timeout: int = 300
+    ) -> ExecutionResult:
+        """
+        Execute code in the kernel.
+        
+        This is a simplified implementation that:
+        1. Validates kernel exists
+        2. Wraps code to capture output and maintain namespace
+        3. Executes in the kernel's container
+        4. Returns results
+        
+        Args:
+            kernel_id: ID of kernel to execute in
+            code: Python code to execute
+            timeout: Maximum execution time
+        
+        Returns:
+            ExecutionResult with output and status
+        
+        Raises:
+            KernelError: If kernel not found or execution fails
+        """
+        if kernel_id not in self.kernels:
+            raise KernelError(f"Kernel {kernel_id} not found")
+        
+        kernel_info = self.kernels[kernel_id]
+        
+        # Update activity
+        kernel_info.last_activity = datetime.utcnow()
+        
+        # For simplified implementation, we execute code by creating
+        # a Python script that:
+        # 1. Loads namespace from kernel_info
+        # 2. Executes user code
+        # 3. Saves namespace back
+        # 4. Returns result as JSON
+        
+        # Execute in container using Python
+        # In real implementation, this would use docker exec or similar
+        # For now, we simulate execution with proper stdout/stderr capture
+        import time
+        start_time = time.time()
+        
+        try:
+            # Capture stdout and stderr
+            stdout_capture = io.StringIO()
+            stderr_capture = io.StringIO()
+            old_stdout = sys.stdout
+            old_stderr = sys.stderr
+            
+            result_value = None
+            error = None
+            
+            try:
+                # Redirect stdout/stderr
+                sys.stdout = stdout_capture
+                sys.stderr = stderr_capture
+                
+                # Execute and update namespace
+                exec_globals = kernel_info.namespace.copy()
+                exec(code, exec_globals)
+                
+                # Update kernel namespace
+                kernel_info.namespace.update(exec_globals)
+                
+                # Try to get result from last expression
+                result_value = exec_globals.get('_', None)
+                
+            except SyntaxError as e:
+                error = f"SyntaxError: {e.msg}"
+                stderr_capture.write(f"{error}\n")
+            except Exception as e:
+                error = f"{type(e).__name__}: {str(e)}"
+                stderr_capture.write(f"{error}\n")
+            finally:
+                # Restore stdout/stderr
+                sys.stdout = old_stdout
+                sys.stderr = old_stderr
+            
+            # Get captured output
+            stdout = stdout_capture.getvalue()
+            stderr = stderr_capture.getvalue()
+            
+            execution_time = time.time() - start_time
+            
+            return ExecutionResult(
+                success=(error is None),
+                stdout=stdout,
+                stderr=stderr,
+                result=result_value,
+                execution_time=execution_time,
+                exit_code=0 if error is None else 1,
+                error=error
+            )
+            
+        except Exception as e:
+            execution_time = time.time() - start_time
+            return ExecutionResult(
+                success=False,
+                stdout="",
+                stderr="",
+                result=None,
+                execution_time=execution_time,
+                exit_code=1,
+                error=f"Execution failed: {str(e)}"
+            )
+    
+    def shutdown_kernel(self, kernel_id: str) -> None:
+        """
+        Shutdown kernel and cleanup container.
+        
+        Args:
+            kernel_id: ID of kernel to shutdown
+        
+        Raises:
+            KernelError: If kernel not found
+        """
+        if kernel_id not in self.kernels:
+            raise KernelError(f"Kernel {kernel_id} not found")
+        
+        kernel_info = self.kernels[kernel_id]
+        
+        # Stop and remove container
+        try:
+            self.container_manager.stop_container(kernel_info.container_id, timeout=10)
+            self.container_manager.remove_container(kernel_info.container_id)
+        except Exception as e:
+            # Log but don't fail - best effort cleanup
+            pass
+        
+        # Remove from registry
+        del self.kernels[kernel_id]
+    
+    def inspect_namespace(self, kernel_id: str) -> List[str]:
+        """
+        Get list of variables in kernel namespace.
+        
+        Args:
+            kernel_id: ID of kernel to inspect
+        
+        Returns:
+            List of variable names (excluding private vars)
+        
+        Raises:
+            KernelError: If kernel not found
+        """
+        if kernel_id not in self.kernels:
+            raise KernelError(f"Kernel {kernel_id} not found")
+        
+        kernel_info = self.kernels[kernel_id]
+        
+        # Filter out private variables and builtins
+        variables = [
+            name for name in kernel_info.namespace.keys()
+            if not name.startswith('_') and name not in ['__builtins__']
+        ]
+        
+        return variables
+    
+    def get_variable_info(
+        self,
+        kernel_id: str,
+        variable_name: str
+    ) -> Dict[str, Any]:
+        """
+        Get information about a variable.
+        
+        Args:
+            kernel_id: ID of kernel
+            variable_name: Name of variable to inspect
+        
+        Returns:
+            Dictionary with type, size, and repr info
+        
+        Raises:
+            KernelError: If kernel or variable not found
+        """
+        if kernel_id not in self.kernels:
+            raise KernelError(f"Kernel {kernel_id} not found")
+        
+        kernel_info = self.kernels[kernel_id]
+        
+        if variable_name not in kernel_info.namespace:
+            raise KernelError(f"Variable {variable_name} not found in kernel namespace")
+        
+        value = kernel_info.namespace[variable_name]
+        
+        info = {
+            "type": type(value).__name__,
+            "repr": repr(value)[:100],  # Truncate long reprs
+        }
+        
+        # Add size for sized objects
+        if hasattr(value, '__len__'):
+            try:
+                info["size"] = len(value)
+            except:
+                pass
+        
+        # Add shape for array-like objects
+        if hasattr(value, 'shape'):
+            try:
+                info["shape"] = value.shape
+            except:
+                pass
+        
+        return info
+    
+    def restart_kernel(self, kernel_id: str) -> None:
+        """
+        Restart kernel (reset namespace).
+        
+        Args:
+            kernel_id: ID of kernel to restart
+        
+        Raises:
+            KernelError: If kernel not found
+        """
+        if kernel_id not in self.kernels:
+            raise KernelError(f"Kernel {kernel_id} not found")
+        
+        # Clear namespace to reset state
+        kernel_info = self.kernels[kernel_id]
+        kernel_info.namespace.clear()
+        kernel_info.last_activity = datetime.utcnow()
+    
+    def cleanup_idle_kernels(self, idle_timeout: timedelta) -> int:
+        """
+        Cleanup kernels idle longer than timeout.
+        
+        Args:
+            idle_timeout: Maximum idle time before cleanup
+        
+        Returns:
+            Number of kernels cleaned up
+        """
+        now = datetime.utcnow()
+        kernels_to_remove = []
+        
+        for kernel_id, kernel_info in self.kernels.items():
+            idle_time = now - kernel_info.last_activity
+            if idle_time > idle_timeout:
+                kernels_to_remove.append(kernel_id)
+        
+        # Shutdown idle kernels
+        for kernel_id in kernels_to_remove:
+            try:
+                self.shutdown_kernel(kernel_id)
+            except Exception:
+                # Best effort cleanup
+                pass
+        
+        return len(kernels_to_remove)
+    
+    def _wrap_code_with_namespace(self, code: str, namespace: Dict[str, Any]) -> str:
+        """
+        Wrap code to load/save namespace.
+        
+        This is a helper for the real implementation where code would be
+        executed in a container with namespace persistence.
+        
+        Args:
+            code: User code to wrap
+            namespace: Current namespace state
+        
+        Returns:
+            Wrapped code with namespace handling
+        """
+        # In real implementation, this would serialize namespace,
+        # inject it into container execution, run code, and extract
+        # updated namespace.
+        # For this simplified version, we don't need the wrapping
+        # since we're executing directly in Python.
+        return code

src/mcp_forge/execution/jupyter/sessions.py

@@ -0,0 +1,426 @@
+"""Session management for stateful execution."""
+
+from typing import Dict, Optional, List, Any
+from dataclasses import dataclass, field
+from datetime import datetime, timedelta
+
+from mcp_forge.execution.jupyter.kernel import JupyterKernelManager
+from mcp_forge.config.schema import SessionConfig
+from mcp_forge.security.audit import AuditLogger, AuditEventType, AuditSeverity
+from mcp_forge.security.resource_limits import ResourceLimits
+from mcp_forge.execution.simple.executor import ExecutionResult
+
+
+class SessionError(Exception):
+    """Raised when session operations fail."""
+    pass
+
+
+@dataclass
+class SessionState:
+    """Documented state for a session."""
+    session_id: str
+    documented_variables: Dict[str, str] = field(default_factory=dict)
+    note: str = ""
+    last_updated: datetime = field(default_factory=datetime.utcnow)
+    all_variables: List[str] = field(default_factory=list)
+    introspection: Dict[str, dict] = field(default_factory=dict)
+    
+    def to_dict(self) -> dict:
+        """Convert to dictionary for JSON serialization."""
+        return {
+            "session_id": self.session_id,
+            "documented_variables": self.documented_variables,
+            "note": self.note,
+            "last_updated": self.last_updated.isoformat(),
+            "all_variables": self.all_variables,
+            "introspection": self.introspection
+        }
+
+
+class Session:
+    """Stateful execution session."""
+    
+    def __init__(
+        self,
+        session_id: str,
+        kernel_id: str,
+        created_at: datetime,
+        resource_limits: ResourceLimits
+    ):
+        """
+        Initialize session.
+        
+        Args:
+            session_id: Unique session identifier
+            kernel_id: ID of associated kernel
+            created_at: Session creation timestamp
+            resource_limits: Resource limits for this session
+        """
+        self.session_id = session_id
+        self.kernel_id = kernel_id
+        self.created_at = created_at
+        self.last_activity = created_at
+        self.resource_limits = resource_limits
+        self.state = SessionState(session_id=session_id)
+        self.documented_variables: Dict[str, str] = {}
+        self.documentation_note: Optional[str] = None
+    
+    def update_activity(self) -> None:
+        """Update last activity timestamp."""
+        self.last_activity = datetime.utcnow()
+    
+    def is_idle(self, timeout: timedelta) -> bool:
+        """
+        Check if session is idle beyond timeout.
+        
+        Args:
+            timeout: Maximum idle time
+        
+        Returns:
+            True if session has been idle longer than timeout
+        """
+        now = datetime.utcnow()
+        idle_time = now - self.last_activity
+        return idle_time > timeout
+    
+    def to_dict(self) -> dict:
+        """Convert to dictionary for serialization."""
+        return {
+            "session_id": self.session_id,
+            "kernel_id": self.kernel_id,
+            "created_at": self.created_at.isoformat(),
+            "last_activity": self.last_activity.isoformat(),
+            "state": self.state.to_dict()
+        }
+
+
+class SessionManager:
+    """Manages stateful execution sessions."""
+    
+    def __init__(
+        self,
+        config: SessionConfig,
+        kernel_manager: JupyterKernelManager,
+        audit_logger: AuditLogger
+    ):
+        """
+        Initialize session manager.
+        
+        Args:
+            config: Session configuration
+            kernel_manager: Kernel lifecycle manager
+            audit_logger: Audit logging instance
+        """
+        self.config = config
+        self.kernel_manager = kernel_manager
+        self.audit_logger = audit_logger
+        self.sessions: Dict[str, Session] = {}
+    
+    def create_session(
+        self,
+        session_id: str,
+        resource_limits: ResourceLimits,
+        volumes: Optional[Dict[str, dict]] = None
+    ) -> Session:
+        """
+        Create new stateful session.
+        
+        Args:
+            session_id: Unique identifier for session
+            resource_limits: Resource limits for session
+            volumes: Optional volume mounts
+        
+        Returns:
+            Created Session object
+        
+        Raises:
+            SessionError: If session_id already exists
+            SessionError: If max concurrent sessions exceeded
+        """
+        if session_id in self.sessions:
+            raise SessionError(f"Session {session_id} already exists")
+        
+        # Check max concurrent limit
+        self._enforce_max_concurrent()
+        
+        # Start kernel
+        kernel_id = self.kernel_manager.start_kernel(session_id, volumes=volumes)
+        
+        # Create session
+        now = datetime.utcnow()
+        session = Session(
+            session_id=session_id,
+            kernel_id=kernel_id,
+            created_at=now,
+            resource_limits=resource_limits
+        )
+        
+        self.sessions[session_id] = session
+        
+        # Log session creation
+        self.audit_logger.log(
+            event_type=AuditEventType.SESSION_CREATE,
+            severity=AuditSeverity.INFO,
+            message=f"Session created: {session_id}",
+            session_id=session_id,
+            details={
+                "kernel_id": kernel_id,
+                "memory": resource_limits.memory_bytes,
+                "cpu_quota": resource_limits.cpu_quota
+            }
+        )
+        
+        return session
+    
+    def session_exists(self, session_id: str) -> bool:
+        """
+        Check if session exists.
+        
+        Args:
+            session_id: Session identifier
+        
+        Returns:
+            True if session exists, False otherwise
+        """
+        return session_id in self.sessions
+    
+    def get_session(self, session_id: str) -> Session:
+        """
+        Get session by ID.
+        
+        Args:
+            session_id: Session identifier
+        
+        Returns:
+            Session object
+        
+        Raises:
+            SessionError: If session doesn't exist
+        """
+        if session_id not in self.sessions:
+            raise SessionError(f"Session {session_id} not found")
+        
+        return self.sessions[session_id]
+    
+    async def document_variables(
+        self,
+        session_id: str,
+        variables: Dict[str, str],
+        note: Optional[str] = None,
+        clear: bool = False
+    ) -> Dict:
+        """
+        Document important variables in a session.
+        
+        Args:
+            session_id: Session identifier
+            variables: Dict mapping variable names to descriptions
+            note: Optional general note about session state
+            clear: Whether to clear existing documentation first
+        
+        Returns:
+            Result dict with success status and documented count
+        """
+        session = self.get_session(session_id)
+        
+        if clear:
+            session.documented_variables = {}
+        
+        # Store variable documentation in session
+        if not hasattr(session, 'documented_variables'):
+            session.documented_variables = {}
+        
+        session.documented_variables.update(variables)
+        
+        if note:
+            session.documentation_note = note
+        
+        return {
+            "success": True,
+            "documented_count": len(variables),
+            "total_documented": len(session.documented_variables)
+        }
+    
+    def execute_in_session(
+        self,
+        session_id: str,
+        code: str,
+        timeout: int = 300
+    ) -> ExecutionResult:
+        """
+        Execute code in session kernel.
+        
+        Args:
+            session_id: Session to execute in
+            code: Python code to execute
+            timeout: Maximum execution time
+        
+        Returns:
+            ExecutionResult with output
+        
+        Raises:
+            SessionError: If session doesn't exist
+        """
+        session = self.get_session(session_id)
+        
+        # Update activity
+        session.update_activity()
+        
+        # Execute in kernel
+        result = self.kernel_manager.execute_code(
+            session.kernel_id,
+            code,
+            timeout=timeout
+        )
+        
+        return result
+    
+    def document_state(
+        self,
+        session_id: str,
+        variables: Dict[str, str],
+        note: str = "",
+        clear: bool = False
+    ) -> None:
+        """
+        Document important variables in session.
+        
+        Updates session.state with variable descriptions and runs
+        introspection to capture current namespace state.
+        
+        Args:
+            session_id: Session to document
+            variables: Dictionary of variable_name -> description
+            note: Optional note about session state
+            clear: If True, replace all documented variables; if False, merge
+        
+        Raises:
+            SessionError: If session doesn't exist
+        """
+        session = self.get_session(session_id)
+        
+        # Update documented variables
+        if clear:
+            session.state.documented_variables = variables.copy()
+        else:
+            session.state.documented_variables.update(variables)
+        
+        # Update note if provided
+        if note:
+            session.state.note = note
+        
+        # Run introspection to get current namespace state
+        session.state.all_variables = self.kernel_manager.inspect_namespace(session.kernel_id)
+        
+        # Get variable info for documented variables
+        session.state.introspection = {}
+        for var_name in variables.keys():
+            if var_name in session.state.all_variables:
+                try:
+                    info = self.kernel_manager.get_variable_info(session.kernel_id, var_name)
+                    session.state.introspection[var_name] = info
+                except Exception:
+                    # Variable might not exist yet
+                    pass
+        
+        # Update timestamp
+        session.state.last_updated = datetime.utcnow()
+        session.update_activity()
+    
+    def get_session_state(self, session_id: str) -> SessionState:
+        """
+        Get documented state for session.
+        
+        Args:
+            session_id: Session identifier
+        
+        Returns:
+            SessionState object
+        
+        Raises:
+            SessionError: If session doesn't exist
+        """
+        session = self.get_session(session_id)
+        return session.state
+    
+    def destroy_session(self, session_id: str) -> None:
+        """
+        Destroy session and cleanup kernel.
+        
+        Args:
+            session_id: Session to destroy
+        
+        Raises:
+            SessionError: If session doesn't exist
+        """
+        session = self.get_session(session_id)
+        
+        # Shutdown kernel
+        try:
+            self.kernel_manager.shutdown_kernel(session.kernel_id)
+        except Exception as e:
+            # Log but continue with cleanup
+            self.audit_logger.log(
+                event_type=AuditEventType.SESSION_DESTROY,
+                severity=AuditSeverity.WARNING,
+                message=f"Error shutting down kernel for session {session_id}",
+                session_id=session_id,
+                error=str(e)
+            )
+        
+        # Remove session
+        del self.sessions[session_id]
+        
+        # Log destruction
+        self.audit_logger.log(
+            event_type=AuditEventType.SESSION_DESTROY,
+            severity=AuditSeverity.INFO,
+            message=f"Session destroyed: {session_id}",
+            session_id=session_id
+        )
+    
+    def cleanup_idle_sessions(self) -> int:
+        """
+        Cleanup sessions idle beyond configured timeout.
+        
+        Returns:
+            Number of sessions cleaned up
+        """
+        timeout = timedelta(seconds=self.config.idle_timeout)
+        sessions_to_remove = []
+        
+        for session_id, session in self.sessions.items():
+            if session.is_idle(timeout):
+                sessions_to_remove.append(session_id)
+        
+        # Destroy idle sessions
+        for session_id in sessions_to_remove:
+            try:
+                self.destroy_session(session_id)
+            except Exception:
+                # Best effort cleanup
+                pass
+        
+        return len(sessions_to_remove)
+    
+    def list_sessions(self) -> List[dict]:
+        """
+        List all active sessions with metadata.
+        
+        Returns:
+            List of session dictionaries
+        """
+        return [session.to_dict() for session in self.sessions.values()]
+    
+    def _enforce_max_concurrent(self) -> None:
+        """
+        Enforce max concurrent sessions limit.
+        
+        Raises:
+            SessionError: If at max concurrent sessions
+        """
+        if len(self.sessions) >= self.config.max_concurrent:
+            raise SessionError(
+                f"Maximum concurrent sessions ({self.config.max_concurrent}) reached"
+            )

src/mcp_forge/execution/simple/__init__.py

@@ -0,0 +1,6 @@
+"""Simple (stateless) execution backend."""
+
+from .executor import CodeExecutor, ExecutionResult
+from .backend import SimpleBackend
+
+__all__ = ["CodeExecutor", "ExecutionResult", "SimpleBackend"]

src/mcp_forge/execution/simple/backend.py

@@ -0,0 +1,184 @@
+"""Simple (stateless) execution backend."""
+
+from typing import Optional, Dict
+import hashlib
+
+from mcp_forge.config.schema import ForgeConfig
+from mcp_forge.podman.containers import SecureContainerManager
+from mcp_forge.security.audit import AuditLogger, AuditEventType, AuditSeverity
+from mcp_forge.security.resource_limits import ResourceLimits, parse_memory_string
+from mcp_forge.execution.simple.executor import CodeExecutor, ExecutionResult
+
+
+class SimpleBackend:
+    """Stateless code execution backend."""
+    
+    def __init__(
+        self,
+        config: ForgeConfig,
+        container_manager: SecureContainerManager,
+        audit_logger: AuditLogger
+    ):
+        """
+        Initialize simple backend.
+        
+        Args:
+            config: Forge configuration
+            container_manager: Container lifecycle manager
+            audit_logger: Audit logging instance
+        """
+        self.config = config
+        self.container_manager = container_manager
+        self.audit_logger = audit_logger
+    
+    def execute(
+        self,
+        code: str,
+        timeout: Optional[int] = None,
+        memory: Optional[str] = None,
+        cpu_quota: Optional[int] = None,
+        custom_image: Optional[str] = None,
+        volumes: Optional[Dict[str, dict]] = None,
+        injection_code: Optional[str] = None,
+        bridge_socket_path: Optional[str] = None
+    ) -> ExecutionResult:
+        """
+        Execute Python code in stateless container.
+        
+        Each execution creates a fresh container with no persistent state.
+        Resource limits default to configuration values but can be overridden
+        within configured maximums.
+        
+        Args:
+            code: Python code to execute
+            timeout: Max execution time in seconds (uses config default if None)
+            memory: Memory limit string (uses config default if None)
+            cpu_quota: CPU quota (uses config default if None)
+            custom_image: Custom image name (uses config default if None)
+            volumes: Volume mounts dict
+            injection_code: Optional MCP tool injection code to prepend
+            bridge_socket_path: Optional path to MCP bridge socket for mounting
+        
+        Returns:
+            ExecutionResult with execution output and metadata
+        
+        Raises:
+            ValueError: If limits exceed configured maximums
+        """
+        # Use defaults from config if not specified
+        timeout = timeout if timeout is not None else self.config.execution.default_timeout
+        memory = memory if memory is not None else self.config.execution.default_memory
+        cpu_quota = cpu_quota if cpu_quota is not None else self.config.execution.default_cpu_quota
+        
+        # Validate limits against maximums
+        self._validate_limits(timeout, memory, cpu_quota)
+        
+        # Get image
+        image = self._get_image(custom_image)
+        
+        # Create resource limits (or None if disabled)
+        resource_limits = None
+        if self.config.security.enforce_resource_limits:
+            resource_limits = ResourceLimits(
+                memory=memory,
+                cpu_quota=cpu_quota,
+                storage="1g",  # Default storage quota
+                timeout=timeout
+            )
+        
+        # Log execution (hash code, don't log actual content)
+        code_hash = hashlib.sha256(code.encode()).hexdigest()
+        self.audit_logger.log(
+            event_type=AuditEventType.EXECUTION_REQUEST,
+            severity=AuditSeverity.INFO,
+            message="Code execution requested",
+            details={
+                "code_hash": code_hash,
+                "image": image,
+                "timeout": timeout,
+                "memory": memory,
+                "cpu_quota": cpu_quota
+            }
+        )
+        
+        # Create executor and execute
+        executor = CodeExecutor(
+            container_manager=self.container_manager,
+            image=image,
+            resource_limits=resource_limits
+        )
+        
+        result = executor.execute(
+            code, 
+            timeout=timeout, 
+            injection_code=injection_code,
+            bridge_socket_path=bridge_socket_path
+        )
+        
+        # Log result
+        self.audit_logger.log(
+            event_type=AuditEventType.EXECUTION_REQUEST,
+            severity=AuditSeverity.INFO,
+            message="Code execution completed",
+            details={
+                "code_hash": code_hash,
+                "success": result.success,
+                "execution_time": result.execution_time,
+                "exit_code": result.exit_code
+            }
+        )
+        
+        return result
+    
+    def _validate_limits(
+        self,
+        timeout: int,
+        memory: str,
+        cpu_quota: int
+    ) -> None:
+        """
+        Validate resource limits against configuration maximums.
+        
+        Args:
+            timeout: Timeout in seconds
+            memory: Memory limit string
+            cpu_quota: CPU quota value
+        
+        Raises:
+            ValueError: If any limit exceeds maximum
+        """
+        # Validate timeout
+        if timeout > self.config.execution.max_timeout:
+            raise ValueError(
+                f"timeout {timeout}s exceeds maximum {self.config.execution.max_timeout}s"
+            )
+        
+        # Validate memory
+        memory_bytes = parse_memory_string(memory)
+        max_memory_bytes = parse_memory_string(self.config.execution.max_memory)
+        if memory_bytes > max_memory_bytes:
+            raise ValueError(
+                f"memory {memory} exceeds maximum {self.config.execution.max_memory}"
+            )
+        
+        # Validate CPU quota
+        if cpu_quota > self.config.execution.max_cpu_quota:
+            raise ValueError(
+                f"cpu_quota {cpu_quota} exceeds maximum {self.config.execution.max_cpu_quota}"
+            )
+    
+    def _get_image(self, custom_image: Optional[str]) -> str:
+        """
+        Get image name, defaulting to configured image.
+        
+        Args:
+            custom_image: Optional custom image name
+        
+        Returns:
+            Image name to use
+        """
+        if custom_image is not None:
+            return custom_image
+        
+        # Default to Python 3.11
+        return self.config.images.python_3_11

src/mcp_forge/execution/simple/executor.py

@@ -0,0 +1,222 @@
+"""Code execution in isolated containers."""
+
+from typing import Any, Optional
+from dataclasses import dataclass, asdict
+import json
+import time
+import textwrap
+import uuid
+
+from mcp_forge.podman.containers import SecureContainerManager, ContainerConfig
+from mcp_forge.security.resource_limits import ResourceLimits
+
+
+@dataclass
+class ExecutionResult:
+    """Result of code execution."""
+    success: bool
+    stdout: str
+    stderr: str
+    result: Optional[Any]
+    execution_time: float
+    exit_code: int
+    error: Optional[str] = None
+    
+    def to_dict(self) -> dict:
+        """Convert to dictionary for JSON serialization."""
+        return asdict(self)
+
+
+class CodeExecutor:
+    """Executes Python code in isolated containers."""
+    
+    def __init__(
+        self,
+        container_manager: SecureContainerManager,
+        image: str,
+        resource_limits: ResourceLimits
+    ):
+        self.container_manager = container_manager
+        self.image = image
+        self.resource_limits = resource_limits
+    
+    def execute(
+        self,
+        code: str,
+        timeout: Optional[int] = None,
+        injection_code: Optional[str] = None,
+        bridge_socket_path: Optional[str] = None
+    ) -> ExecutionResult:
+        """
+        Execute Python code in a fresh container.
+        
+        Process:
+        1. Create container with code
+        2. Start container
+        3. Wait for completion (with timeout)
+        4. Capture stdout/stderr
+        5. Extract result from last expression
+        6. Cleanup container
+        
+        Args:
+            code: Python code to execute
+            timeout: Maximum execution time in seconds
+            injection_code: Optional MCP tool injection code to prepend
+            bridge_socket_path: Optional path to MCP bridge socket for mounting
+        
+        Returns:
+            ExecutionResult with stdout, stderr, result, and timing
+        """
+        start_time = time.time()
+        container_id = None
+        
+        # Use provided timeout or default from resource limits
+        exec_timeout = timeout if timeout is not None else self.resource_limits.timeout
+        
+        try:
+            # Prepare code wrapper (with injection if provided)
+            wrapped_code = self._prepare_code(code, injection_code=injection_code)
+            
+            # Generate a session ID for this execution to register the container
+            import uuid
+            session_id = f"simple-exec-{uuid.uuid4().hex[:12]}"
+            
+            # Set up volumes for MCP bridge socket if provided
+            volumes = {}
+            if bridge_socket_path:
+                volumes[bridge_socket_path] = {
+                    "bind": bridge_socket_path,
+                    "mode": "rw"
+                }
+            
+            # Create container configuration
+            config = ContainerConfig(
+                image=self.image,
+                command=["python", "-c", wrapped_code],
+                resource_limits=self.resource_limits,
+                volumes=volumes if volumes else None
+            )
+            
+            # Create and start container with session_id for proper registration
+            container_id = self.container_manager.create_container(config, session_id=session_id)
+            self.container_manager.start_container(container_id)
+            
+            # Wait for completion
+            exit_code = self.container_manager.wait_for_container(
+                container_id,
+                timeout=exec_timeout
+            )
+            
+            # Get logs
+            stdout, stderr = self.container_manager.get_container_logs(container_id)
+            
+            # Parse output to extract result
+            result, error = self._parse_output(stdout)
+            
+            execution_time = time.time() - start_time
+            
+            return ExecutionResult(
+                success=(exit_code == 0 and error is None),
+                stdout=stdout,
+                stderr=stderr,
+                result=result,
+                execution_time=execution_time,
+                exit_code=exit_code,
+                error=error
+            )
+            
+        except TimeoutError as e:
+            execution_time = time.time() - start_time
+            return ExecutionResult(
+                success=False,
+                stdout="",
+                stderr="",
+                result=None,
+                execution_time=execution_time,
+                exit_code=-1,
+                error=f"Execution timeout: {str(e)}"
+            )
+            
+        finally:
+            # Cleanup container
+            if container_id is not None:
+                try:
+                    self.container_manager.remove_container(container_id)
+                except Exception:
+                    pass  # Best effort cleanup
+    
+    def _prepare_code(self, code: str, injection_code: Optional[str] = None) -> str:
+        """
+        Wrap code to capture result and handle errors.
+        
+        Wraps code in try/except and captures:
+        - Last expression result
+        - Exceptions with traceback
+        - Execution metadata
+        
+        Args:
+            code: User code to execute
+            injection_code: Optional MCP tool injection code to prepend
+        
+        Returns wrapped code that outputs JSON to stdout.
+        """
+        # Prepend injection code if provided
+        if injection_code:
+            full_code = injection_code + "\n\n" + code
+        else:
+            full_code = code
+            
+        # Escape the code for embedding in exec string
+        escaped_code = full_code.replace('\\', '\\\\').replace('"', '\\"').replace('\n', '\\n')
+        
+        wrapper_template = '''
+import sys
+import json
+import traceback
+
+def __mcp_execute():
+    result = None
+    error = None
+    
+    try:
+        # Execute user code
+        exec_globals = {}
+        exec("""%s""", exec_globals)
+        
+        # Try to get result from last expression
+        result = exec_globals.get('_', None)
+        
+    except SyntaxError as e:
+        error = f"SyntaxError: {e.msg} (line {e.lineno})"
+    except Exception as e:
+        error = f"{type(e).__name__}: {str(e)}"
+    
+    # Output result as JSON
+    print(json.dumps({"result": result, "error": error}))
+
+__mcp_execute()
+'''
+        
+        return wrapper_template % escaped_code
+    
+    def _parse_output(self, stdout: str) -> tuple[Optional[Any], Optional[str]]:
+        """
+        Parse execution output to extract result and error.
+        
+        Returns:
+            (result, error_message)
+        """
+        if not stdout:
+            return None, None
+        
+        try:
+            # First line should be JSON output
+            lines = stdout.split('\n', 1)
+            json_line = lines[0]
+            
+            data = json.loads(json_line)
+            return data.get("result"), data.get("error")
+            
+        except (json.JSONDecodeError, ValueError):
+            # If can't parse JSON, treat entire output as result
+            return None, None