# Copyright (c) Microsoft. All rights reserved.

"""FastAPI server implementation."""

from __future__ import annotations

import asyncio
import importlib.metadata
import inspect
import json
import logging
import os
import secrets
import uuid
from collections.abc import AsyncGenerator, Awaitable, Callable
from contextlib import asynccontextmanager
from typing import Any, cast

from fastapi import FastAPI, HTTPException, Request
from fastapi.middleware.cors import CORSMiddleware
from fastapi.responses import JSONResponse, StreamingResponse
from fastapi.staticfiles import StaticFiles

from ._deployment import DeploymentManager
from ._discovery import EntityDiscovery
from ._executor import AgentFrameworkExecutor
from ._mapper import MessageMapper
from ._openai import OpenAIExecutor
from .models import AgentFrameworkRequest, MetaResponse, OpenAIError
from .models._discovery_models import Deployment, DeploymentConfig, DiscoveryResponse, EntityInfo

logger = logging.getLogger(__name__)


def _extract_error_details(body: object) -> tuple[str | None, str | None, str | None]:
    """Extract typed OpenAI-style error payload fields."""
    if not isinstance(body, dict):
        return None, None, None

    body_dict = cast(dict[str, object], body)
    error_obj = body_dict.get("error")
    if not isinstance(error_obj, dict):
        return None, None, None

    error_dict = cast(dict[str, object], error_obj)
    message = error_dict.get("message")
    error_type = error_dict.get("type")
    code = error_dict.get("code")

    return (
        message if isinstance(message, str) else None,
        error_type if isinstance(error_type, str) else None,
        code if isinstance(code, str) else None,
    )


# Get package version
try:
    __version__ = importlib.metadata.version("agent-framework-devui")
except importlib.metadata.PackageNotFoundError:
    __version__ = "0.0.0"  # Fallback for development mode


# No AuthMiddleware class needed - we'll use the decorator pattern instead


class DevServer:
    """Development Server - OpenAI compatible API server for debugging agents."""

    def __init__(
        self,
        entities_dir: str | None = None,
        port: int = 8080,
        host: str = "127.0.0.1",
        cors_origins: list[str] | None = None,
        ui_enabled: bool = True,
        mode: str = "developer",
        auth_enabled: bool = True,
        auth_token: str | None = None,
    ) -> None:
        """Initialize the development server.

        Args:
            entities_dir: Directory to scan for entities
            port: Port to run server on
            host: Host to bind server to
            cors_origins: List of allowed CORS origins
            ui_enabled: Whether to enable the UI
            mode: Server mode - 'developer' (full access, verbose errors) or 'user' (restricted APIs, generic errors)
            auth_enabled: Whether to require Bearer token auth on /v1/* endpoints. Defaults to True.
            auth_token: Bearer token. If None and auth_enabled, falls back to the DEVUI_AUTH_TOKEN
                environment variable. Loopback binds may use an auto-generated token logged at startup.
        """
        self.entities_dir = entities_dir
        self.port = port
        self.host = host

        # CORS default is same-origin only (empty allowlist) on every host. The
        # previous wildcard-on-localhost default let any webpage the developer
        # visited read DevUI's responses cross-origin. Callers who need a real
        # cross-origin dev frontend pass an explicit allowlist.
        if cors_origins is None:
            cors_origins = []

        self.cors_origins = cors_origins
        self.ui_enabled = ui_enabled
        self.mode = mode
        self.auth_enabled = auth_enabled
        self.auth_token = self._resolve_auth_token(host, auth_enabled, auth_token)
        self.executor: AgentFrameworkExecutor | None = None
        self.openai_executor: OpenAIExecutor | None = None
        self.deployment_manager = DeploymentManager()
        self._app: FastAPI | None = None
        self._pending_entities: list[Any] | None = None
        self._running_tasks: dict[str, asyncio.Task[Any]] = {}  # Track running response tasks for cancellation

    def set_pending_entities(self, entities: list[Any]) -> None:
        """Set in-memory entities to register on startup."""
        self._pending_entities = entities

    _AUTH_LOOPBACK_HOSTS = frozenset({"127.0.0.1", "localhost"})
    _LOOPBACK_HOSTS = frozenset({"127.0.0.1", "localhost", "[::1]", "::1"})

    @classmethod
    def _is_auth_loopback_host(cls, host: str) -> bool:
        """Return True when unauthenticated DevUI may be limited to local loopback."""
        return host.lower() in cls._AUTH_LOOPBACK_HOSTS

    def _loopback_allowed_hosts(self) -> frozenset[str] | None:
        """Return the Host-header allowlist when bound to a loopback interface, else None.

        Returning None disables Host-header enforcement (e.g. for 0.0.0.0 / public binds,
        where the operator is intentionally exposing the service).
        """
        host = self.host.lower()
        if host not in self._LOOPBACK_HOSTS:
            return None
        return self._LOOPBACK_HOSTS

    @classmethod
    def _resolve_auth_token(cls, host: str, auth_enabled: bool, auth_token: str | None) -> str | None:
        """Resolve the active Bearer token. Returns None when auth is disabled."""
        is_loopback = cls._is_auth_loopback_host(host)
        if not auth_enabled:
            if not is_loopback:
                raise ValueError(
                    "DevUI authentication cannot be disabled for non-loopback hosts. "
                    "Bind to 127.0.0.1/localhost for no-auth local development, or enable auth and provide "
                    "DEVUI_AUTH_TOKEN or auth_token for network-reachable binds."
                )
            return None
        if auth_token:
            return auth_token
        env_token = os.getenv("DEVUI_AUTH_TOKEN")
        if env_token:
            return env_token
        if not is_loopback:
            raise ValueError("DEVUI_AUTH_TOKEN or auth_token is required when DevUI is bound to a non-loopback host.")
        generated = secrets.token_urlsafe(32)
        logger.info("=" * 70)
        logger.info("DevUI authentication enabled with auto-generated token:")
        logger.info(f"   {generated}")
        logger.info("Pass it as: Authorization: Bearer <token>")
        logger.info("=" * 70)
        return generated

    def _is_dev_mode(self) -> bool:
        """Check if running in developer mode.

        Returns:
            True if in developer mode, False if in user mode
        """
        return self.mode == "developer"

    def _format_error(self, error: Exception, context: str = "Operation") -> str:
        """Format error message based on server mode.

        In developer mode: Returns detailed error message for debugging.
        In user mode: Returns generic message and logs details internally.

        Args:
            error: The exception that occurred
            context: Description of the operation that failed (e.g., "Request execution")

        Returns:
            Formatted error message appropriate for the current mode
        """
        if self._is_dev_mode():
            # Developer mode: Show full error details for debugging
            return f"{context} failed: {error!s}"

        # User mode: Generic message to user, detailed logging internally
        logger.error(f"{context} failed: {error}", exc_info=True)
        return f"{context} failed"

    def _require_developer_mode(self, feature: str = "operation") -> None:
        """Check if current mode allows developer operations.

        Args:
            feature: Name of the feature being accessed (for error message)

        Raises:
            HTTPException: If in user mode
        """
        if self.mode == "user":
            logger.warning(f"Blocked {feature} access in user mode")
            raise HTTPException(
                status_code=403,
                detail={
                    "error": {
                        "message": f"Access denied: {feature} requires developer mode",
                        "type": "permission_denied",
                        "code": "developer_mode_required",
                        "current_mode": self.mode,
                    }
                },
            )

    async def _ensure_executor(self) -> AgentFrameworkExecutor:
        """Ensure executor is initialized."""
        if self.executor is None:
            logger.info("Initializing Agent Framework executor...")

            # Create components directly
            entity_discovery = EntityDiscovery(self.entities_dir)
            message_mapper = MessageMapper()
            self.executor = AgentFrameworkExecutor(entity_discovery, message_mapper)

            # Discover entities from directory
            discovered_entities = await self.executor.discover_entities()
            logger.info(f"Discovered {len(discovered_entities)} entities from directory")

            # Register any pending in-memory entities
            if self._pending_entities:
                discovery = self.executor.entity_discovery
                for entity in self._pending_entities:
                    try:
                        entity_info = await discovery.create_entity_info_from_object(entity, source="in_memory")
                        discovery.register_entity(entity_info.id, entity_info, entity)
                        logger.info(f"Registered in-memory entity: {entity_info.id}")
                    except Exception as e:
                        logger.error(f"Failed to register in-memory entity: {e}")
                self._pending_entities = None  # Clear after registration

            # Get the final entity count after all registration
            all_entities = self.executor.entity_discovery.list_entities()
            logger.info(f"Total entities available: {len(all_entities)}")

        return self.executor

    async def _ensure_openai_executor(self) -> OpenAIExecutor:
        """Ensure OpenAI executor is initialized.

        Returns:
            OpenAI executor instance

        Raises:
            ValueError: If OpenAI executor cannot be initialized
        """
        if self.openai_executor is None:
            # Initialize local executor first to get conversation_store
            local_executor = await self._ensure_executor()

            # Create OpenAI executor with shared conversation store
            self.openai_executor = OpenAIExecutor(local_executor.conversation_store)

            if self.openai_executor.is_configured:
                logger.info("OpenAI proxy mode available (OPENAI_API_KEY configured)")
            else:
                logger.info("OpenAI proxy mode disabled (OPENAI_API_KEY not set)")

        return self.openai_executor

    async def _cleanup_entities(self) -> None:
        """Cleanup entity resources (close clients, MCP tools, credentials, etc.)."""
        if not self.executor:
            return

        logger.info("Cleaning up entity resources...")
        entities = self.executor.entity_discovery.list_entities()
        closed_count = 0
        mcp_tools_closed = 0
        credentials_closed = 0
        hook_count = 0

        for entity_info in entities:
            entity_id = entity_info.id

            try:
                # Step 1: Execute registered cleanup hooks (NEW)
                cleanup_hooks = self.executor.entity_discovery.get_cleanup_hooks(entity_id)
                for hook in cleanup_hooks:
                    try:
                        if inspect.iscoroutinefunction(hook):
                            await hook()
                        else:
                            hook()
                        hook_count += 1
                        logger.debug(f"✓ Executed cleanup hook for: {entity_id}")
                    except Exception as e:
                        logger.warning(f"⚠ Cleanup hook failed for {entity_id}: {e}")

                # Step 2: Close chat clients and their credentials (EXISTING)
                entity_obj = self.executor.entity_discovery.get_entity_object(entity_id)

                if entity_obj and hasattr(entity_obj, "client"):
                    client = entity_obj.client

                    # Close the chat client itself
                    if hasattr(client, "close") and callable(client.close):
                        if inspect.iscoroutinefunction(client.close):
                            await client.close()
                        else:
                            client.close()
                        closed_count += 1
                        logger.debug(f"Closed client for entity: {entity_info.id}")

                    # Close credentials attached to chat clients (e.g., AzureCliCredential)
                    credential_attrs = ["credential", "async_credential", "_credential", "_async_credential"]
                    for attr in credential_attrs:
                        if hasattr(client, attr):
                            cred = getattr(client, attr)
                            if cred and hasattr(cred, "close") and callable(cred.close):
                                try:
                                    if inspect.iscoroutinefunction(cred.close):
                                        await cred.close()
                                    else:
                                        cred.close()
                                    credentials_closed += 1
                                    logger.debug(f"Closed credential for entity: {entity_info.id}")
                                except Exception as e:
                                    logger.warning(f"Error closing credential for {entity_info.id}: {e}")

                # Close MCP tools (framework tracks them in mcp_tools)
                if entity_obj and hasattr(entity_obj, "mcp_tools"):
                    for mcp_tool in entity_obj.mcp_tools:
                        if hasattr(mcp_tool, "close") and callable(mcp_tool.close):
                            try:
                                if inspect.iscoroutinefunction(mcp_tool.close):
                                    await mcp_tool.close()
                                else:
                                    mcp_tool.close()
                                mcp_tools_closed += 1
                                tool_name = getattr(mcp_tool, "name", "unknown")
                                logger.debug(f"Closed MCP tool '{tool_name}' for entity: {entity_info.id}")
                            except Exception as e:
                                logger.warning(f"Error closing MCP tool for {entity_info.id}: {e}")

            except Exception as e:
                logger.warning(f"Error cleaning up entity {entity_id}: {e}")

        if hook_count > 0:
            logger.info(f"✓ Executed {hook_count} cleanup hook(s)")
        if closed_count > 0:
            logger.info(f"✓ Closed {closed_count} entity client(s)")
        if credentials_closed > 0:
            logger.info(f"✓ Closed {credentials_closed} credential(s)")
        if mcp_tools_closed > 0:
            logger.info(f"✓ Closed {mcp_tools_closed} MCP tool(s)")

        # Close OpenAI executor if it exists
        if self.openai_executor:
            try:
                await self.openai_executor.close()
                logger.info("Closed OpenAI executor")
            except Exception as e:
                logger.warning(f"Error closing OpenAI executor: {e}")

    def create_app(self) -> FastAPI:
        """Create the FastAPI application."""

        @asynccontextmanager
        async def lifespan(app: FastAPI) -> AsyncGenerator[None]:
            # Startup
            logger.info("Starting Agent Framework Server")
            await self._ensure_executor()
            await self._ensure_openai_executor()  # Initialize OpenAI executor
            try:
                yield
            finally:
                # Shutdown
                logger.info("Shutting down Agent Framework Server")

                # Cleanup entity resources (e.g., close credentials, clients)
                if self.executor:
                    await self._cleanup_entities()

        app = FastAPI(
            title="Agent Framework Server",
            description="OpenAI-compatible API server for Agent Framework and other AI frameworks",
            version=__version__,
            lifespan=lifespan,
        )

        # Middleware registration order matters: Starlette wraps later-added
        # middleware around earlier-added ones, so the LAST registered runs
        # outermost (sees the request first). We want Host-header enforcement
        # to run before CORS/auth, so it is registered last below.

        # Add CORS middleware
        # Note: allow_credentials cannot be True when allow_origins is ["*"]
        # For localhost dev with wildcard origins, credentials are disabled
        # For network deployments with specific origins or empty list, credentials can be enabled
        allow_credentials = self.cors_origins != ["*"]

        app.add_middleware(
            CORSMiddleware,
            allow_origins=self.cors_origins,
            allow_credentials=allow_credentials,
            allow_methods=["*"],
            allow_headers=["*"],
        )

        # Bearer-token authentication. Enabled by default; opt out via
        # DevServer(auth_enabled=False) for embedded/test scenarios.
        if self.auth_enabled and self.auth_token:
            expected_token = self.auth_token
            logger.info("Authentication middleware enabled")

            @app.middleware("http")
            async def auth_middleware(request: Request, call_next: Callable[[Request], Awaitable[Any]]) -> Any:
                """Validate Bearer token authentication.

                Skips authentication for health, the UI shell, static assets, and OPTIONS preflight.
                """
                if request.method == "OPTIONS":
                    return await call_next(request)

                if request.url.path in ["/health", "/"] or request.url.path.startswith("/assets"):
                    return await call_next(request)

                auth_header = request.headers.get("Authorization")
                if not auth_header or not auth_header.startswith("Bearer "):
                    return JSONResponse(
                        status_code=401,
                        content={
                            "error": {
                                "message": (
                                    "Missing or invalid Authorization header. Expected: Authorization: Bearer <token>"
                                ),
                                "type": "authentication_error",
                                "code": "missing_token",
                            }
                        },
                    )

                token = auth_header.replace("Bearer ", "", 1).strip()
                if not secrets.compare_digest(token, expected_token):
                    return JSONResponse(
                        status_code=401,
                        content={
                            "error": {
                                "message": "Invalid authentication token",
                                "type": "authentication_error",
                                "code": "invalid_token",
                            }
                        },
                    )

                return await call_next(request)

            _ = auth_middleware

        # Host-header allowlist for loopback binds: on a loopback interface, only
        # accept requests whose Host header names a loopback address. Registered LAST
        # so it runs outermost, rejecting non-loopback Host values before CORS/auth
        # (and before CORS can short-circuit a preflight on a rebound request).
        allowed_hosts = self._loopback_allowed_hosts()
        if allowed_hosts is not None:
            expected_hosts = allowed_hosts

            @app.middleware("http")
            async def host_header_middleware(request: Request, call_next: Callable[[Request], Awaitable[Any]]) -> Any:
                host_header = request.headers.get("host", "")
                hostname = host_header.split(":", 1)[0].lower()
                if hostname and hostname not in expected_hosts:
                    return JSONResponse(
                        status_code=400,
                        content={
                            "error": {
                                "message": (
                                    f"Invalid Host header '{host_header}'. DevUI is bound to a "
                                    "loopback interface and only accepts requests addressed to it."
                                ),
                                "type": "invalid_host",
                                "code": "host_not_allowed",
                            }
                        },
                    )
                return await call_next(request)

            _ = host_header_middleware

        self._register_routes(app)
        self._mount_ui(app)

        return app

    def _register_routes(self, app: FastAPI) -> None:
        """Register API routes."""

        @app.get("/health")
        async def health_check() -> dict[str, Any]:
            """Health check endpoint."""
            executor = await self._ensure_executor()
            # Use list_entities() to avoid re-discovering and re-registering entities
            entities = executor.entity_discovery.list_entities()

            return {"status": "healthy", "entities_count": len(entities), "framework": "agent_framework"}

        @app.get("/meta", response_model=MetaResponse)
        async def get_meta() -> MetaResponse:
            """Get server metadata and configuration."""
            # Ensure executors are initialized to check capabilities
            openai_executor = await self._ensure_openai_executor()

            return MetaResponse(
                ui_mode=self.mode,  # type: ignore[arg-type]
                version=__version__,
                framework="agent_framework",
                runtime="python",  # Python DevUI backend
                capabilities={
                    "instrumentation": os.getenv("ENABLE_INSTRUMENTATION") == "true",
                    "openai_proxy": openai_executor.is_configured,
                    "deployment": True,  # Deployment feature is available
                },
                auth_required=self.auth_enabled,
            )

        @app.get("/v1/entities", response_model=DiscoveryResponse)
        async def discover_entities() -> DiscoveryResponse:
            """List all registered entities."""
            try:
                executor = await self._ensure_executor()
                # Use list_entities() instead of discover_entities() to get already-registered entities
                entities = executor.entity_discovery.list_entities()
                return DiscoveryResponse(entities=entities)
            except Exception as e:
                logger.error(f"Error listing entities: {e}")
                raise HTTPException(status_code=500, detail=f"Entity listing failed: {e!s}") from e

        @app.get("/v1/entities/{entity_id}/info", response_model=EntityInfo)
        async def get_entity_info(entity_id: str) -> EntityInfo:
            """Get detailed information about a specific entity (triggers lazy loading)."""
            try:
                executor = await self._ensure_executor()
                entity_info = executor.get_entity_info(entity_id)

                if not entity_info:
                    raise HTTPException(status_code=404, detail=f"Entity {entity_id} not found")

                # Trigger lazy loading if entity not yet loaded
                # This will import the module and enrich metadata
                # Pass checkpoint_manager to ensure workflows get checkpoint storage injected
                entity_obj = await executor.entity_discovery.load_entity(
                    entity_id, checkpoint_manager=executor.checkpoint_manager
                )

                # Get updated entity info (may have been enriched during load)
                entity_info = executor.get_entity_info(entity_id) or entity_info

                # For workflows, populate additional detailed information
                if entity_info.type == "workflow" and entity_obj:
                    # Entity object already loaded by load_entity() above
                    # Get workflow structure
                    workflow_dump: dict[str, Any] | str | None = None
                    if hasattr(entity_obj, "to_dict") and callable(getattr(entity_obj, "to_dict", None)):
                        try:
                            workflow_dump = entity_obj.to_dict()  # type: ignore[attr-defined]
                        except Exception:
                            workflow_dump = None
                    elif hasattr(entity_obj, "to_json") and callable(getattr(entity_obj, "to_json", None)):
                        try:
                            raw_dump = entity_obj.to_json()  # type: ignore[attr-defined]
                        except Exception:
                            workflow_dump = None
                        else:
                            if isinstance(raw_dump, (bytes, bytearray)):
                                try:
                                    raw_dump = raw_dump.decode()
                                except Exception:
                                    raw_dump = raw_dump.decode(errors="replace")
                            if isinstance(raw_dump, str):
                                try:
                                    parsed_dump = json.loads(raw_dump)
                                except Exception:
                                    workflow_dump = raw_dump
                                else:
                                    if isinstance(parsed_dump, dict):
                                        parsed_dump_dict = cast(dict[str, Any], parsed_dump)
                                        workflow_dump = {str(k): v for k, v in parsed_dump_dict.items()}
                                    else:
                                        workflow_dump = raw_dump
                            else:
                                workflow_dump = raw_dump
                    elif hasattr(entity_obj, "__dict__"):
                        workflow_dump = {k: v for k, v in entity_obj.__dict__.items() if not k.startswith("_")}

                    # Get input schema information
                    input_schema = {}
                    input_type_name = "Unknown"
                    start_executor_id = ""

                    try:
                        from ._utils import (
                            extract_executor_message_types,
                            generate_input_schema,
                            select_primary_input_type,
                        )

                        start_executor = entity_obj.get_start_executor()
                    except Exception as e:
                        logger.debug(f"Could not extract input info for workflow {entity_id}: {e}")
                    else:
                        if start_executor:
                            start_executor_id = getattr(start_executor, "executor_id", "") or getattr(
                                start_executor, "id", ""
                            )

                            message_types = extract_executor_message_types(start_executor)
                            input_type = select_primary_input_type(message_types)

                            if input_type:
                                input_type_name = getattr(input_type, "__name__", str(input_type))

                                # Generate schema using comprehensive schema generation
                                input_schema = generate_input_schema(input_type)

                    if not input_schema:
                        input_schema = {"type": "string"}
                        if input_type_name == "Unknown":
                            input_type_name = "string"

                    # Get executor list
                    executor_list = []
                    if hasattr(entity_obj, "executors") and entity_obj.executors:
                        executor_list = [getattr(ex, "executor_id", str(ex)) for ex in entity_obj.executors]

                    # Create copy of entity info and populate workflow-specific fields
                    # Note: DevUI provides runtime checkpoint storage for ALL workflows via conversations
                    update_payload: dict[str, Any] = {
                        "workflow_dump": workflow_dump,
                        "input_schema": input_schema,
                        "input_type_name": input_type_name,
                        "start_executor_id": start_executor_id,
                    }
                    if executor_list:
                        update_payload["executors"] = executor_list
                    return entity_info.model_copy(update=update_payload)

                # For non-workflow entities, return as-is
                return entity_info

            except HTTPException:
                raise
            except ValueError as e:
                # ValueError from load_entity - could be "not found" or "failed to load"
                error_str = str(e)
                error_msg = self._format_error(e, "Entity loading")
                # Use 404 for "not found", 422 for load failures (entity exists but can't load)
                if "not found" in error_str.lower() and "failed to load" not in error_str.lower():
                    raise HTTPException(status_code=404, detail=error_msg) from e
                # Entity exists but failed to load (e.g., missing env vars, import errors)
                raise HTTPException(status_code=422, detail=error_msg) from e
            except Exception as e:
                error_msg = self._format_error(e, "Entity info retrieval")
                raise HTTPException(status_code=500, detail=error_msg) from e

        @app.post("/v1/entities/{entity_id}/reload")
        async def reload_entity(entity_id: str) -> dict[str, Any]:
            """Hot reload entity (clears cache, will reimport on next access).

            This enables hot reload during development - edit entity code, call this endpoint,
            and the next execution will use the updated code without server restart.
            """
            self._require_developer_mode("entity hot reload")
            try:
                executor = await self._ensure_executor()

                # Check if entity exists
                entity_info = executor.get_entity_info(entity_id)
                if not entity_info:
                    raise HTTPException(status_code=404, detail=f"Entity {entity_id} not found")

                # Check if entity is in-memory (cannot be reloaded)
                if entity_info.source == "in_memory":
                    raise HTTPException(
                        status_code=400,
                        detail="In-memory entities cannot be reloaded. "
                        "They only exist in memory and have no source files to reload from.",
                    )

                # Invalidate cache
                executor.entity_discovery.invalidate_entity(entity_id)

                return {
                    "success": True,
                    "message": f"Entity '{entity_id}' cache cleared. Will reload on next access.",
                }

            except HTTPException:
                raise
            except Exception as e:
                logger.error(f"Error reloading entity {entity_id}: {e}")
                raise HTTPException(status_code=500, detail=f"Failed to reload entity: {e!s}") from e

        # ============================================================================
        # Deployment Endpoints
        # ============================================================================

        @app.post("/v1/deployments")
        async def create_deployment(config: DeploymentConfig) -> StreamingResponse:
            """Deploy entity to Azure Container Apps with streaming events.

            Returns SSE stream of deployment progress events.
            """
            self._require_developer_mode("deployment")
            try:
                executor = await self._ensure_executor()

                # Validate entity exists and supports deployment
                entity_info = executor.get_entity_info(config.entity_id)
                if not entity_info:
                    raise HTTPException(status_code=404, detail=f"Entity {config.entity_id} not found")

                if not entity_info.deployment_supported:
                    reason = entity_info.deployment_reason or "Deployment not supported for this entity"
                    raise HTTPException(status_code=400, detail=reason)

                # Get entity path from metadata
                from pathlib import Path

                entity_path_str = entity_info.metadata.get("path")
                if not entity_path_str:
                    raise HTTPException(
                        status_code=400,
                        detail="Entity path not found in metadata (in-memory entities cannot be deployed)",
                    )

                entity_path = Path(entity_path_str)

                # Stream deployment events
                async def event_generator() -> AsyncGenerator[str]:
                    async for event in self.deployment_manager.deploy(config, entity_path):
                        # Format as SSE
                        import json

                        yield f"data: {json.dumps(event.model_dump())}\n\n"

                return StreamingResponse(event_generator(), media_type="text/event-stream")

            except HTTPException:
                raise
            except Exception as e:
                error_msg = self._format_error(e, "Deployment creation")
                raise HTTPException(status_code=500, detail=error_msg) from e

        @app.get("/v1/deployments")
        async def list_deployments(entity_id: str | None = None) -> list[Deployment]:
            """List all deployments, optionally filtered by entity."""
            self._require_developer_mode("deployment listing")
            try:
                return await self.deployment_manager.list_deployments(entity_id)
            except Exception as e:
                error_msg = self._format_error(e, "Deployment listing")
                raise HTTPException(status_code=500, detail=error_msg) from e

        @app.get("/v1/deployments/{deployment_id}")
        async def get_deployment(deployment_id: str) -> Deployment:
            """Get deployment by ID."""
            self._require_developer_mode("deployment details")
            try:
                deployment = await self.deployment_manager.get_deployment(deployment_id)
                if not deployment:
                    raise HTTPException(status_code=404, detail=f"Deployment {deployment_id} not found")
                return deployment
            except HTTPException:
                raise
            except Exception as e:
                logger.error(f"Error getting deployment: {e}")
                raise HTTPException(status_code=500, detail=f"Failed to get deployment: {e!s}") from e

        @app.delete("/v1/deployments/{deployment_id}")
        async def delete_deployment(deployment_id: str) -> dict[str, Any]:
            """Delete deployment from Azure Container Apps."""
            self._require_developer_mode("deployment deletion")
            try:
                await self.deployment_manager.delete_deployment(deployment_id)
                return {"success": True, "message": f"Deployment {deployment_id} deleted successfully"}
            except ValueError as e:
                raise HTTPException(status_code=404, detail=str(e)) from e
            except Exception as e:
                logger.error(f"Error deleting deployment: {e}")
                raise HTTPException(status_code=500, detail=f"Failed to delete deployment: {e!s}") from e

        # Convenience endpoint: deploy specific entity
        @app.post("/v1/entities/{entity_id}/deploy")
        async def deploy_entity(entity_id: str, config: DeploymentConfig) -> StreamingResponse:
            """Convenience endpoint to deploy entity (shortcuts to /v1/deployments)."""
            self._require_developer_mode("deployment")
            # Override entity_id from path parameter
            config.entity_id = entity_id
            return await create_deployment(config)

        # ============================================================================
        # Response/Conversation Endpoints
        # ============================================================================

        @app.post("/v1/responses")
        async def create_response(request: AgentFrameworkRequest, raw_request: Request) -> Any:
            """OpenAI Responses API endpoint - routes to local or OpenAI executor."""
            try:
                # Check if frontend requested OpenAI proxy mode
                proxy_mode = raw_request.headers.get("X-Proxy-Backend")

                if proxy_mode == "openai":
                    # Route to OpenAI executor
                    logger.info("🔀 Routing to OpenAI proxy mode")
                    openai_executor = await self._ensure_openai_executor()

                    if not openai_executor.is_configured:
                        error = OpenAIError.create(
                            "OpenAI proxy mode not configured. Set OPENAI_API_KEY environment variable."
                        )
                        return JSONResponse(status_code=503, content=error.to_dict())

                    # Execute via OpenAI with dedicated streaming method
                    if request.stream:
                        return StreamingResponse(
                            self._stream_openai_execution(openai_executor, request),
                            media_type="text/event-stream",
                            headers={
                                "Cache-Control": "no-cache",
                                "Connection": "keep-alive",
                            },
                        )
                    return await openai_executor.execute_sync(request)

                # Route to local Agent Framework executor (original behavior)
                raw_body = await raw_request.body()
                logger.info(f"Raw request body: {raw_body.decode()}")
                logger.info(f"Parsed request: metadata={request.metadata}")

                # Get entity_id from metadata
                entity_id = request.get_entity_id()
                logger.info(f"Extracted entity_id: {entity_id}")

                if not entity_id:
                    error = OpenAIError.create("Missing entity_id in metadata. Provide metadata.entity_id in request.")
                    return JSONResponse(status_code=400, content=error.to_dict())

                # Get executor and validate entity exists
                executor = await self._ensure_executor()
                try:
                    entity_info = executor.get_entity_info(entity_id)
                    logger.info(f"Found entity: {entity_info.name} ({entity_info.type})")
                except Exception:
                    error = OpenAIError.create(f"Entity not found: {entity_id}")
                    return JSONResponse(status_code=404, content=error.to_dict())

                # Execute request
                if request.stream:
                    # Generate response ID for tracking
                    response_id = f"resp_{uuid.uuid4().hex[:8]}"
                    logger.info(f"[CANCELLATION] Creating response {response_id} for entity {entity_id}")

                    # Inject response_id into extra_body for trace context
                    if request.extra_body is None:
                        request.extra_body = {}
                    request.extra_body["response_id"] = response_id

                    return StreamingResponse(
                        self._stream_with_cancellation(executor, request, response_id),
                        media_type="text/event-stream",
                        headers={
                            "Cache-Control": "no-cache",
                            "Connection": "keep-alive",
                            "X-Response-ID": response_id,  # Include ID for debugging/tracking
                        },
                    )
                return await executor.execute_sync(request)

            except Exception as e:
                error_msg = self._format_error(e, "Request execution")
                error = OpenAIError.create(error_msg)
                return JSONResponse(status_code=500, content=error.to_dict())

        @app.post("/v1/responses/{response_id}/cancel")
        async def cancel_response(response_id: str) -> dict[str, Any]:
            """Cancel a running response execution.

            This endpoint allows explicit cancellation of a running stream.
            Note: Cancellation also happens automatically when the client disconnects.
            """
            logger.info(f"[CANCELLATION] Cancel request received for {response_id}")

            if task := self._running_tasks.get(response_id):
                if not task.done():
                    logger.info(f"[CANCELLATION] Cancelling task for {response_id}")
                    task.cancel()
                    # Wait briefly for cancellation to propagate
                    try:  # noqa: SIM105
                        await asyncio.wait_for(task, timeout=0.5)
                    except (asyncio.CancelledError, asyncio.TimeoutError):
                        pass
                    return {"status": "cancelled", "response_id": response_id}
                logger.warning(f"[CANCELLATION] Task already completed for {response_id}")
                return {"status": "already_completed", "response_id": response_id}
            logger.warning(f"[CANCELLATION] No task found for {response_id}")
            return {"status": "not_found", "response_id": response_id}

        # ========================================
        # OpenAI Conversations API (Standard)
        # ========================================

        @app.post("/v1/conversations", response_model=None)
        async def create_conversation(raw_request: Request) -> dict[str, Any] | JSONResponse:
            """Create a new conversation - routes to OpenAI or local based on mode."""
            try:
                # Parse request body
                request_data = await raw_request.json()

                # Check if frontend requested OpenAI proxy mode
                proxy_mode = raw_request.headers.get("X-Proxy-Backend")

                if proxy_mode == "openai":
                    # Create conversation in OpenAI
                    openai_executor = await self._ensure_openai_executor()
                    if not openai_executor.is_configured:
                        error = OpenAIError.create(
                            "OpenAI proxy mode not configured. Set OPENAI_API_KEY environment variable.",
                            type="configuration_error",
                            code="openai_not_configured",
                        )
                        return JSONResponse(status_code=503, content=error.to_dict())

                    # Use OpenAI client to create conversation
                    from openai import APIStatusError, AsyncOpenAI, AuthenticationError, PermissionDeniedError

                    client = AsyncOpenAI(
                        api_key=openai_executor.api_key,
                        base_url=openai_executor.base_url,
                    )

                    try:
                        metadata = request_data.get("metadata")
                        logger.debug(f"Creating OpenAI conversation with metadata: {metadata}")
                        conversation = await client.conversations.create(metadata=metadata)
                        logger.info(f"Created OpenAI conversation: {conversation.id}")
                        return conversation.model_dump()
                    except AuthenticationError as e:
                        # 401 - Invalid API key or authentication issue
                        logger.error(f"OpenAI authentication error creating conversation: {e}")
                        message, error_type, code = _extract_error_details(e.body if hasattr(e, "body") else None)
                        error = OpenAIError.create(
                            message=message or str(e),
                            type=error_type or "authentication_error",
                            code=code or "invalid_api_key",
                        )
                        return JSONResponse(status_code=401, content=error.to_dict())
                    except PermissionDeniedError as e:
                        # 403 - Permission denied
                        logger.error(f"OpenAI permission denied creating conversation: {e}")
                        message, error_type, code = _extract_error_details(e.body if hasattr(e, "body") else None)
                        error = OpenAIError.create(
                            message=message or str(e),
                            type=error_type or "permission_denied",
                            code=code or "insufficient_permissions",
                        )
                        return JSONResponse(status_code=403, content=error.to_dict())
                    except APIStatusError as e:
                        # Other OpenAI API errors (rate limit, etc.)
                        logger.error(f"OpenAI API error creating conversation: {e}")
                        message, error_type, code = _extract_error_details(e.body if hasattr(e, "body") else None)
                        error = OpenAIError.create(
                            message=message or str(e),
                            type=error_type or "api_error",
                            code=code or "unknown_error",
                        )
                        return JSONResponse(
                            status_code=e.status_code if hasattr(e, "status_code") else 500, content=error.to_dict()
                        )

                # Local mode - use DevUI conversation store
                metadata = request_data.get("metadata")
                executor = await self._ensure_executor()
                conversation = executor.conversation_store.create_conversation(metadata=metadata)
                return conversation.model_dump()
            except HTTPException:
                raise
            except Exception as e:
                logger.error(f"Error creating conversation: {e}", exc_info=True)
                error = OpenAIError.create(f"Failed to create conversation: {e!s}")
                return JSONResponse(status_code=500, content=error.to_dict())

        @app.get("/v1/conversations")
        async def list_conversations(
            agent_id: str | None = None,
            entity_id: str | None = None,
            type: str | None = None,
        ) -> dict[str, Any]:
            """List conversations, optionally filtered by agent_id, entity_id, and/or type.

            Query Parameters:
            - agent_id: Filter by agent_id (for agent conversations)
            - entity_id: Filter by entity_id (for workflow sessions or other entities)
            - type: Filter by conversation type (e.g., "workflow_session")

            Multiple filters can be combined (AND logic).
            """
            try:
                executor = await self._ensure_executor()

                # Build filter criteria
                filters: dict[str, str] = {}
                if agent_id:
                    filters["agent_id"] = agent_id
                if entity_id:
                    filters["entity_id"] = entity_id
                if type:
                    filters["type"] = type

                # Apply filters
                conversations = await executor.conversation_store.list_conversations_by_metadata(filters)

                return {
                    "object": "list",
                    "data": [conv.model_dump() for conv in conversations],
                    "has_more": False,
                }
            except HTTPException:
                raise
            except Exception as e:
                logger.error(f"Error listing conversations: {e}")
                raise HTTPException(status_code=500, detail=f"Failed to list conversations: {e!s}") from e

        @app.get("/v1/conversations/{conversation_id}")
        async def retrieve_conversation(conversation_id: str) -> dict[str, Any]:
            """Get conversation - OpenAI standard."""
            try:
                executor = await self._ensure_executor()
                conversation = executor.conversation_store.get_conversation(conversation_id)
                if not conversation:
                    raise HTTPException(status_code=404, detail="Conversation not found")
                return conversation.model_dump()
            except HTTPException:
                raise
            except Exception as e:
                logger.error(f"Error getting conversation {conversation_id}: {e}")
                raise HTTPException(status_code=500, detail=f"Failed to get conversation: {e!s}") from e

        @app.post("/v1/conversations/{conversation_id}")
        async def update_conversation(conversation_id: str, request_data: dict[str, Any]) -> dict[str, Any]:
            """Update conversation metadata - OpenAI standard."""
            try:
                executor = await self._ensure_executor()
                metadata = request_data.get("metadata", {})
                conversation = executor.conversation_store.update_conversation(conversation_id, metadata=metadata)
                return conversation.model_dump()
            except ValueError as e:
                raise HTTPException(status_code=404, detail=str(e)) from e
            except HTTPException:
                raise
            except Exception as e:
                logger.error(f"Error updating conversation {conversation_id}: {e}")
                raise HTTPException(status_code=500, detail=f"Failed to update conversation: {e!s}") from e

        @app.delete("/v1/conversations/{conversation_id}")
        async def delete_conversation(conversation_id: str) -> dict[str, Any]:
            """Delete conversation - OpenAI standard."""
            try:
                executor = await self._ensure_executor()
                result = executor.conversation_store.delete_conversation(conversation_id)
                return result.model_dump()
            except ValueError as e:
                raise HTTPException(status_code=404, detail=str(e)) from e
            except HTTPException:
                raise
            except Exception as e:
                logger.error(f"Error deleting conversation {conversation_id}: {e}")
                raise HTTPException(status_code=500, detail=f"Failed to delete conversation: {e!s}") from e

        @app.post("/v1/conversations/{conversation_id}/items")
        async def create_conversation_items(conversation_id: str, request_data: dict[str, Any]) -> dict[str, Any]:
            """Add items to conversation - OpenAI standard."""
            try:
                executor = await self._ensure_executor()
                items = request_data.get("items", [])
                conv_items = await executor.conversation_store.add_items(conversation_id, items=items)
                return {"object": "list", "data": [item.model_dump() for item in conv_items]}
            except ValueError as e:
                raise HTTPException(status_code=404, detail=str(e)) from e
            except HTTPException:
                raise
            except Exception as e:
                logger.error(f"Error adding items to conversation {conversation_id}: {e}")
                raise HTTPException(status_code=500, detail=f"Failed to add items: {e!s}") from e

        @app.get("/v1/conversations/{conversation_id}/items")
        async def list_conversation_items(
            conversation_id: str, limit: int = 100, after: str | None = None, order: str = "asc"
        ) -> dict[str, Any]:
            """List conversation items - OpenAI standard."""
            try:
                executor = await self._ensure_executor()
                items, has_more = await executor.conversation_store.list_items(
                    conversation_id, limit=limit, after=after, order=order
                )
                # Handle both Pydantic models and dicts (some stores return raw dicts)
                serialized_items: list[dict[str, Any]] = []
                for item in items:
                    if hasattr(item, "model_dump"):
                        serialized_items.append(item.model_dump())
                    elif isinstance(item, dict):
                        item_dict = cast(dict[str, Any], item)
                        serialized_items.append({str(k): v for k, v in item_dict.items()})
                    else:
                        logger.warning(f"Unexpected item type: {type(item)}, converting to dict")
                        serialized_items.append({str(k): v for k, v in dict(item).items()})

                # Get stored traces for context inspection (DevUI extension)
                traces = executor.conversation_store.get_traces(conversation_id)

                return {
                    "object": "list",
                    "data": serialized_items,
                    "has_more": has_more,
                    "metadata": {
                        "traces": traces,  # Trace events for token usage, timing, LLM context
                    },
                }
            except ValueError as e:
                raise HTTPException(status_code=404, detail=str(e)) from e
            except HTTPException:
                raise
            except Exception as e:
                logger.error(f"Error listing items for conversation {conversation_id}: {e}")
                raise HTTPException(status_code=500, detail=f"Failed to list items: {e!s}") from e

        @app.get("/v1/conversations/{conversation_id}/items/{item_id}")
        async def retrieve_conversation_item(conversation_id: str, item_id: str) -> dict[str, Any]:
            """Get specific conversation item - OpenAI standard.

            Supports checkpoint items - returns full checkpoint state in metadata.full_checkpoint.
            """
            try:
                executor = await self._ensure_executor()
                item = await executor.conversation_store.get_item(conversation_id, item_id)
                if not item:
                    raise HTTPException(status_code=404, detail="Item not found")
                # Handle both Pydantic models and dicts
                result: dict[str, Any]
                if hasattr(item, "model_dump"):
                    result = item.model_dump()
                elif isinstance(item, dict):
                    item_dict = cast(dict[str, Any], item)
                    result = {str(k): v for k, v in item_dict.items()}
                else:
                    result = {"value": item}
                return result
            except HTTPException:
                raise
            except Exception as e:
                logger.error(f"Error getting item {item_id} from conversation {conversation_id}: {e}")
                raise HTTPException(status_code=500, detail=f"Failed to get item: {e!s}") from e

        @app.delete("/v1/conversations/{conversation_id}/items/{item_id}")
        async def delete_conversation_item(conversation_id: str, item_id: str) -> dict[str, Any]:
            """Delete conversation item - supports checkpoint deletion."""
            try:
                executor = await self._ensure_executor()

                # Check if this is a checkpoint item
                if item_id.startswith("checkpoint_"):
                    # Extract checkpoint_id from item_id (format: "checkpoint_{checkpoint_id}")
                    checkpoint_id = item_id[len("checkpoint_") :]
                    storage = executor.checkpoint_manager.get_checkpoint_storage(conversation_id)
                    deleted = await storage.delete(checkpoint_id)

                    if not deleted:
                        raise HTTPException(status_code=404, detail="Checkpoint not found")

                    return {
                        "id": item_id,
                        "object": "item.deleted",
                        "deleted": True,
                    }
                # For other items, delegate to conversation store (if it supports deletion)
                raise HTTPException(status_code=501, detail="Deletion of non-checkpoint items not implemented")

            except HTTPException:
                raise
            except ValueError as e:
                raise HTTPException(status_code=404, detail=str(e)) from e
            except Exception as e:
                logger.error(f"Error deleting item {item_id} from conversation {conversation_id}: {e}")
                raise HTTPException(status_code=500, detail=f"Failed to delete item: {e!s}") from e

        # ============================================================================
        # Checkpoint Management - Now handled through conversation items API
        # Checkpoints are exposed as conversation items with type="checkpoint"
        # ============================================================================

        registered_route_handlers = (
            health_check,
            get_meta,
            discover_entities,
            get_entity_info,
            reload_entity,
            create_deployment,
            list_deployments,
            get_deployment,
            delete_deployment,
            deploy_entity,
            create_response,
            cancel_response,
            create_conversation,
            list_conversations,
            retrieve_conversation,
            update_conversation,
            delete_conversation,
            create_conversation_items,
            list_conversation_items,
            retrieve_conversation_item,
            delete_conversation_item,
        )
        _ = registered_route_handlers

    async def _stream_execution(
        self, executor: AgentFrameworkExecutor, request: AgentFrameworkRequest
    ) -> AsyncGenerator[str]:
        """Stream execution directly through executor."""
        try:
            # Collect events for final response.completed event
            events: list[Any] = []

            # Get conversation_id for trace storage
            conversation_getter = getattr(request, "_get_conversation_id", None)
            conversation_id = conversation_getter() if callable(conversation_getter) else None

            # Stream all events
            async for event in executor.execute_streaming(request):
                events.append(event)

                # Store trace events for context inspection (persisted with conversation)
                if conversation_id and hasattr(event, "type") and event.type == "response.trace.completed":
                    try:
                        trace_data = event.data if hasattr(event, "data") else None
                        if trace_data and isinstance(conversation_id, str):
                            executor.conversation_store.add_trace(conversation_id, trace_data)
                    except Exception as e:
                        logger.debug(f"Failed to store trace event: {e}")

                # IMPORTANT: Check model_dump_json FIRST because to_json() can have newlines (pretty-printing)
                # which breaks SSE format. model_dump_json() returns single-line JSON.
                if hasattr(event, "model_dump_json"):
                    payload = event.model_dump_json()  # type: ignore[attr-defined]
                elif hasattr(event, "to_json") and callable(getattr(event, "to_json", None)):
                    payload = event.to_json()  # type: ignore[attr-defined]
                    # Strip newlines from pretty-printed JSON for SSE compatibility
                    payload = payload.replace("\n", "").replace("\r", "")
                elif isinstance(event, dict):
                    # Handle plain dict events (e.g., error events from executor)
                    payload = json.dumps(event)
                elif hasattr(event, "to_dict") and callable(getattr(event, "to_dict", None)):
                    payload = json.dumps(event.to_dict())  # type: ignore[attr-defined]
                else:
                    payload = json.dumps(str(event))
                yield f"data: {payload}\n\n"

            # Aggregate to final response and emit response.completed event (OpenAI standard)
            from .models import ResponseCompletedEvent

            final_response = await executor.message_mapper.aggregate_to_response(events, request)

            # The sequence number for response.completed should be the next number after all events
            # The last event in the list should have the highest sequence number so far
            # We need to increment from that
            last_seq = 0
            for event in reversed(events):
                sequence_number = getattr(event, "sequence_number", None)
                if isinstance(sequence_number, int):
                    last_seq = sequence_number
                    break

            completed_event = ResponseCompletedEvent(
                type="response.completed",
                response=final_response,
                sequence_number=last_seq + 1,
            )
            yield f"data: {completed_event.model_dump_json()}\n\n"

            # Send final done event
            yield "data: [DONE]\n\n"

        except Exception as e:
            logger.error(f"Error in streaming execution: {e}", exc_info=True)
            error_event = {"id": "error", "object": "error", "error": {"message": str(e), "type": "execution_error"}}
            yield f"data: {json.dumps(error_event)}\n\n"

    async def _stream_openai_execution(
        self, executor: OpenAIExecutor, request: AgentFrameworkRequest
    ) -> AsyncGenerator[str]:
        """Stream execution through OpenAI executor.

        OpenAI events are already in final format - no conversion or aggregation needed.
        Just serialize and stream them as SSE.

        Args:
            executor: OpenAI executor instance
            request: Request to execute

        Yields:
            SSE-formatted event strings
        """
        try:
            # Stream events from OpenAI - they're already ResponseStreamEvent objects
            async for event in executor.execute_streaming(request):
                # Handle error dicts from executor
                if isinstance(event, dict):
                    payload = json.dumps(event)
                    yield f"data: {payload}\n\n"
                    continue

                # OpenAI SDK events have model_dump_json() - use it for single-line JSON
                if hasattr(event, "model_dump_json"):
                    payload = event.model_dump_json()  # type: ignore[attr-defined]
                    yield f"data: {payload}\n\n"
                else:
                    # Fallback (shouldn't happen with OpenAI SDK)
                    logger.warning(f"Unexpected event type from OpenAI: {type(event)}")
                    payload = json.dumps(str(event))
                    yield f"data: {payload}\n\n"

            # OpenAI already sends response.completed event - no aggregation needed!
            # Just send [DONE] marker
            yield "data: [DONE]\n\n"

        except Exception as e:
            logger.error(f"Error in OpenAI streaming execution: {e}", exc_info=True)
            # Emit proper response.failed event
            import os

            error_event = {
                "type": "response.failed",
                "response": {
                    "id": f"resp_{os.urandom(16).hex()}",
                    "status": "failed",
                    "error": {
                        "message": str(e),
                        "type": "internal_error",
                        "code": "streaming_error",
                    },
                },
            }
            yield f"data: {json.dumps(error_event)}\n\n"

    async def _stream_with_cancellation(
        self, executor: AgentFrameworkExecutor, request: AgentFrameworkRequest, response_id: str
    ) -> AsyncGenerator[str]:
        """Stream execution with automatic cancellation on client disconnect.

        This wrapper adds cancellation support to the execution stream:
        1. Tracks the execution as an asyncio Task
        2. Detects client disconnection via GeneratorExit
        3. Cancels the task when client disconnects
        4. Propagates CancelledError through the execution chain

        Args:
            executor: Agent Framework executor instance
            request: Request to execute
            response_id: Unique ID for this response/execution

        Yields:
            SSE-formatted event strings from the original stream
        """
        task = None

        async def execution_wrapper() -> AsyncGenerator[str]:
            """Inner wrapper to handle the actual execution."""
            try:
                logger.debug(f"[CANCELLATION] Starting execution for {response_id}")

                async for chunk in self._stream_execution(executor, request):
                    # Check if we're being cancelled
                    current_task = asyncio.current_task()
                    if current_task and current_task.cancelled():
                        logger.info(f"[CANCELLATION] Detected cancellation, breaking stream for {response_id}")
                        break
                    yield chunk

            except asyncio.CancelledError:
                logger.info(f"[CANCELLATION] Execution cancelled via CancelledError for {response_id}")
                # Emit cancellation event to client (if still connected)
                cancelled_event = {
                    "type": "response.cancelled",
                    "response_id": response_id,
                    "message": "Execution cancelled by user",
                }
                yield f"data: {json.dumps(cancelled_event)}\n\n"
                raise
            except Exception as e:
                logger.error(f"[CANCELLATION] Error in cancellable execution for {response_id}: {e}")
                raise

        try:
            # Get or create the current task and track it
            task = asyncio.current_task()
            if task:
                self._running_tasks[response_id] = task
                logger.debug(f"[CANCELLATION] Tracking task {task.get_name()} for response {response_id}")
            else:
                logger.warning(f"[CANCELLATION] No current task found to track for {response_id}")

            # Stream the execution
            async for chunk in execution_wrapper():
                yield chunk

            logger.debug(f"[CANCELLATION] Stream completed normally for {response_id}")

        except GeneratorExit:
            # Client disconnected - this is raised when the generator is closed
            logger.info(f"[CANCELLATION] Client disconnected, initiating cancellation for {response_id}")

            if task and not task.done():
                logger.info(f"[CANCELLATION] Cancelling task for disconnected client {response_id}")
                task.cancel()
                # Give it a moment to cancel gracefully
                # Note: We should NOT use asyncio.shield here as it prevents cancellation
                try:
                    await asyncio.wait_for(task, timeout=1.0)
                except (asyncio.CancelledError, asyncio.TimeoutError):
                    logger.debug(f"[CANCELLATION] Task cancelled successfully for {response_id}")
                except Exception as e:
                    logger.warning(f"[CANCELLATION] Error during task cancellation for {response_id}: {e}")
            raise  # Re-raise GeneratorExit to properly close the generator

        except asyncio.CancelledError:
            logger.info(f"[CANCELLATION] Stream cancelled for {response_id}")
            raise

        except Exception as e:
            logger.error(f"[CANCELLATION] Unexpected error in stream for {response_id}: {e}")
            raise

        finally:
            # Clean up tracking
            if response_id in self._running_tasks:
                self._running_tasks.pop(response_id)
                logger.debug(f"[CANCELLATION] Cleaned up task tracking for {response_id}")

    def _mount_ui(self, app: FastAPI) -> None:
        """Mount the UI as static files."""
        from pathlib import Path

        ui_dir = Path(__file__).parent / "ui"
        if ui_dir.exists() and ui_dir.is_dir() and self.ui_enabled:
            app.mount("/", StaticFiles(directory=str(ui_dir), html=True), name="ui")

    def register_entities(self, entities: list[Any]) -> None:
        """Register entities to be discovered when server starts.

        Args:
            entities: List of entity objects to register
        """
        if self._pending_entities is None:
            self._pending_entities = []
        self._pending_entities.extend(entities)

    def get_app(self) -> FastAPI:
        """Get the FastAPI application instance."""
        if self._app is None:
            self._app = self.create_app()
        return self._app
