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Creating Interfaces

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Francesco Caracciolo edited this page May 13, 2026 · 1 revision

Creating Interfaces

Interfaces allow third-party applications, messaging services, and custom UIs to interact with Newelle programmatically. This guide explains how to create custom interfaces.

Architecture Overview

Interfaces extend the Interface base class. There are two tiers:

  1. Interface — Minimal base class with lifecycle management (start/stop, state files, cross-process detection)
  2. ChatInterface — Extends Interface with per-user persistent chats, slash command dispatch, LLM-with-tools execution, and tool interaction tracking

Most chat-style interfaces (Telegram, web services) should extend ChatInterface.

classDiagram
    Handler <|-- Interface
    Interface <|-- ChatInterface
    ChatInterface <|-- APIInterface
    ChatInterface <|-- TelegramInterface
    Interface <|-- GUIAPIInterface

    class Interface {
        +start()
        +stop()
        +is_running()
        +is_locally_running()
        +set_controller(controller)
        +_write_state_file()
        +_clear_state_file()
        +check_external_running(key, path)
        +stop_external(key, path)
    }
    class ChatInterface {
        +get_or_create_chat(user_id)
        +process_message(user_id, text, on_chunk, on_tool_event)
        +try_handle_command(user_id, text)
        +run_command(name, user_id, args)
        +handle_tool_interaction(user_id, tool_name, result, interaction_id)
        +resolve_pending_interaction(interaction_id, option_index)
    }
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Interface Base Class

Minimal implementation example:

from .handlers.interfaces.interface import Interface
from .handlers.extra_settings import ExtraSettings
import threading

class MyInterface(Interface):
    key = "my-interface"
    name = "My Custom Interface"

    @staticmethod
    def get_extra_requirements() -> list:
        return ["some-package"]

    def get_extra_settings(self) -> list:
        return [
            ExtraSettings.EntrySetting(
                key="api_key",
                title="API Key",
                description="API key for the service",
                default="",
                password=True,
            ),
            ExtraSettings.SpinSetting(
                key="port",
                title="Port",
                description="Port to listen on",
                default=8080,
                min=1,
                max=65535,
                step=1,
            ),
        ]

    def start(self):
        """Called when the interface is started."""
        if self.controller is None:
            return
        if not self.is_installed():
            print("Dependencies not installed")
            return
        # Start your server/service here
        self._write_state_file()
        print("Interface started")

    def stop(self):
        """Called when the interface is stopped."""
        self._clear_state_file()
        print("Interface stopped")

    def _is_locally_running(self):
        """Return True if this instance is running in the current process."""
        return False  # Replace with actual check

Interface Lifecycle

  1. start() — Called when the user enables the interface. Start your server/service here. Call self._write_state_file() after starting.
  2. stop() — Called when the user disables the interface. Call self._clear_state_file() to clean up.
  3. is_running() — Checks if the interface is running (locally or in another process).
  4. is_locally_running() — Override _is_locally_running() to check the current process.

State Files & Cross-Process Detection

Newelle uses JSON state files to track interface processes across different instances:

# State file is automatically written to:
# {path}/interface_states/{key}.json

# File format:
{
    "pid": 12345,
    "key": "my-interface",
    "started_at": "2024-01-01T12:00:00"
}

# Check if running in another process:
Interface.check_external_running("my-interface", path)

# Stop an external interface:
Interface.stop_external("my-interface", path)

State files are cleaned up automatically when processes are dead.

ChatInterface — Chat-Style Interfaces

ChatInterface is the recommended base class for text-channel interfaces (bots, API endpoints, messaging apps). It provides:

  • Per-user persistent chats — Each user gets a dedicated chat under a named folder
  • Slash command dispatch — Built-in commands (/new, /models, /model, /profile, /tools, etc.)
  • LLM execution with tools — Full agent pipeline with streaming and tool callbacks
  • Tool interaction tracking — Pause/resume for tools that need user input

Subclass Requirements

Your subclass must set class-level attributes:

class MyBotInterface(ChatInterface):
    key = "my-bot"
    name = "My Bot Interface"

    # ChatInterface folder/chat config
    folder_name = "My Bot Chats"   # Folder name for this interface's chats
    folder_color = "#3584e4"       # Folder color
    folder_icon = "folder-symbolic"
    chat_name_prefix = "🤖 MyBot"  # Prefix for auto-generated chat names

Processing Messages

The main entry point is process_message():

def process_message(
    self,
    user_id,         # Identifies the per-user persistent chat
    text,            # The user's message text
    on_chunk=None,   # Optional: called with each text delta during streaming
    on_tool_event=None,  # Optional: called when a tool result arrives
) -> str:
    """Run text through the full LLM-with-tools pipeline. BLOCKING — call from a thread."""

Callbacks:

# on_chunk: receives incremental text as it's generated
def on_chunk(delta: str):
    # delta is new text since last callback
    send_to_user(delta)

# on_tool_event: receives structured events for tool results
def on_tool_event(event: dict):
    # event format depends on type:
    #   {"type": "tool_result", "tool_name": "...", "display_text": "..."}
    #   {"type": "tool_interaction", "tool_name": "...", "interaction_id": "...", "options": [...]}
    if event.get("type") == "tool_result":
        send_status(f"Running tool: {event['tool_name']}")

Tool Interaction Handling

When a tool requires user input (requires_interaction=True), the LLM thread pauses. You need to:

  1. Present options to the user (buttons, keyboard, etc.)
  2. Override handle_tool_interaction() to deliver those options:
def handle_tool_interaction(self, user_id, tool_name, result, interaction_id):
    """Called when a tool needs user input. Deliver options to the user."""
    options = self._pending_interactions.get(interaction_id, {}).get("options", [])
    # Send options to user via your interface's UI
    for opt in options:
        send_button(user_id, opt.title, callback_data=f"choice_{interaction_id}_{i}")
  1. Call resolve_pending_interaction() when the user chooses:
def on_user_choice(self, interaction_id: str, option_index: int):
    success = self.resolve_pending_interaction(interaction_id, option_index)
    if success:
        # The LLM thread unblocks and continues
        pass

Built-in Commands

ChatInterface provides these commands out of the box:

Command Description
/start Welcome message with available commands
/new [name] Create a new persistent chat
/models List available LLM providers and models
/model [provider:]model Switch model
/profile <name> Switch profile
/prompts List available prompts
/tools [toggle <name>] List/manage tools
/scheduled View scheduled tasks
/skill <name> Execute a skill command
/cd [path] Change working directory
/list_chats List all chats
/peek <chat_id> Preview a chat
/resume <chat_id> Switch to a different chat
/autoexec Toggle auto command execution
/option <n> Choose a pending interaction option

Per-User Chat Management

# Get or create a chat for a user (auto-creates folder if needed)
chat_id = self.get_or_create_chat(user_id)

# The chat is saved automatically and persists across restarts

Full Example: A Simple CLI Chat Interface

from .handlers.interfaces.chat_interface import ChatInterface
from .handlers.extra_settings import ExtraSettings
import threading

class CLIChatInterface(ChatInterface):
    key = "cli-chat"
    name = "CLI Chat Interface"
    folder_name = "CLI Chats"
    folder_color = "#33d17a"
    chat_name_prefix = "⌨️ CLI"

    def __init__(self, settings, path):
        super().__init__(settings, path)
        self._running = False
        self._thread = None

    def start(self):
        if self.controller is None:
            return
        self._running = True
        self._thread = threading.Thread(target=self._run_loop, daemon=True)
        self._thread.start()
        self._write_state_file()
        print("CLI Chat interface started")

    def _run_loop(self):
        print("Type /help for commands, /quit to exit")
        while self._running:
            try:
                text = input("> ")
                if text == "/quit":
                    break
                if text.startswith("/"):
                    resp = self.try_handle_command("cli-user", text)
                    if resp:
                        print(resp)
                else:
                    print("Thinking...", end="\r")
                    result = self.process_message("cli-user", text)
                    print(result)
            except (EOFError, KeyboardInterrupt):
                break

    def stop(self):
        self._running = False
        self._clear_state_file()
        print("CLI Chat interface stopped")

    def _is_locally_running(self):
        return self._running and self._thread is not None and self._thread.is_alive()

Adding Interfaces as Extensions

Extensions can provide interface handlers:

from .handlers.descriptors import HandlerDescription

class MyCustomExtension(NewelleExtension):
    def get_interface_handlers(self) -> list[dict]:
        return [
            HandlerDescription(
                key="my-interface",
                title="My Interface",
                description="Description of my interface",
                handler_class=MyInterfaceHandler,
            )
        ]

Or if contributing to Newelle directly, add the handler to AVAILABLE_INTERFACES in constants.py.

Built-in Interfaces Reference

OpenAI Compatible API (api)

Exposes the current LLM as an OpenAI-compatible API server (FastAPI + uvicorn).

Endpoints:

  • POST /v1/chat/completions — Standard chat completions
  • POST /v2/chat/completions — Agent endpoint with tools, commands, per-user persistent chat
  • GET /v1/models — List available models
  • POST /v1/audio/speech — TTS endpoint
  • POST /v1/audio/transcriptions — STT endpoint
  • POST /v1/embeddings — Embedding endpoint

Newelle GUI API (gui-api)

Full REST API for building alternative UIs or integrating deeply with Newelle.

Key endpoints:

  • GET/POST /api/chats — Chat management
  • GET /api/chats/{id}/history — Message history
  • POST /api/messages/run-llm — Run LLM with tools
  • GET/POST /api/prompts — Prompt management
  • GET/POST /api/tools — Tool management
  • GET/POST /api/profiles — Profile management
  • GET/PATCH /api/settings — Settings management
  • GET/POST /api/folders — Folder management
  • POST /api/interfaces/{key}/start — Interface control
  • GET /api/chats/{id}/stream — SSE streaming with tool support
  • POST /api/tts/play — TTS playback
  • POST /api/stt/recognize — STT recognition
  • POST /v1/chat/completions — OpenAI-compatible endpoint

Telegram Bot (telegram)

Chat with Newelle via Telegram. Supports:

  • Text messaging with streaming
  • Voice message transcription
  • Photo/image analysis (via vision-capable LLMs)
  • Inline keyboard for tool interactions
  • All ChatInterface built-in commands
  • Streaming via message drafts or edit-in-place mode

Tips

  • Thread safety: process_message() is blocking — always call it from a worker thread.
  • Controller access: self.controller gives you access to LLM handlers, tools, chats, profiles, and settings.
  • Error reporting: Set self._error to surface errors in the UI.
  • Dependencies: Use get_extra_requirements() to declare pip packages needed by your interface.

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