Extending the CLI

Extending the CLI

Hermes exposes protected extension hooks on HermesCLI so wrapper CLIs can add widgets, keybindings, and layout customizations without overriding the 1000+ line run() method. This keeps your extension decoupled from internal changes.

Extension points

There are five extension seams available:

Hook	Purpose	Override when…
_get_extra_tui_widgets()	Inject widgets into the layout	You need a persistent UI element (panel, status line, mini-player)
_register_extra_tui_keybindings(kb, *, input_area)	Add keyboard shortcuts	You need hotkeys (toggle panels, transport controls, modal shortcuts)
_build_tui_layout_children(**widgets)	Full control over widget ordering	You need to reorder or wrap existing widgets (rare)
process_command()	Add custom slash commands	You need /mycommand handling (pre-existing hook)
_build_tui_style_dict()	Custom prompt_toolkit styles	You need custom colors or styling (pre-existing hook)

The first three are new protected hooks. The last two already existed.

Quick start: a wrapper CLI

#!/usr/bin/env python3
"""my_cli.py — Example wrapper CLI that extends Hermes."""

from cli import HermesCLI
from prompt_toolkit.layout import FormattedTextControl, Window
from prompt_toolkit.filters import Condition


class MyCLI(HermesCLI):

    def __init__(self, **kwargs):
        super().__init__(**kwargs)
        self._panel_visible = False

    def _get_extra_tui_widgets(self):
        """Add a toggleable info panel above the status bar."""
        cli_ref = self
        return [
            Window(
                FormattedTextControl(lambda: "📊 My custom panel content"),
                height=1,
                filter=Condition(lambda: cli_ref._panel_visible),
            ),
        ]

    def _register_extra_tui_keybindings(self, kb, *, input_area):
        """F2 toggles the custom panel."""
        cli_ref = self

        @kb.add("f2")
        def _toggle_panel(event):
            cli_ref._panel_visible = not cli_ref._panel_visible

    def process_command(self, cmd: str) -> bool:
        """Add a /panel slash command."""
        if cmd.strip().lower() == "/panel":
            self._panel_visible = not self._panel_visible
            state = "visible" if self._panel_visible else "hidden"
            print(f"Panel is now {state}")
            return True
        return super().process_command(cmd)


if __name__ == "__main__":
    cli = MyCLI()
    cli.run()

Run it:

cd ~/.hermes/hermes-agent
source .venv/bin/activate
python my_cli.py

Hook reference

_get_extra_tui_widgets()

Returns a list of prompt_toolkit widgets to insert into the TUI layout. Widgets appear between the spacer and the status bar — above the input area but below the main output.

def _get_extra_tui_widgets(self) -> list:
    return []  # default: no extra widgets

Each widget should be a prompt_toolkit container (e.g., Window, ConditionalContainer, HSplit). Use ConditionalContainer or filter=Condition(...) to make widgets toggleable.

from prompt_toolkit.layout import ConditionalContainer, Window, FormattedTextControl
from prompt_toolkit.filters import Condition

def _get_extra_tui_widgets(self):
    return [
        ConditionalContainer(
            Window(FormattedTextControl("Status: connected"), height=1),
            filter=Condition(lambda: self._show_status),
        ),
    ]

_register_extra_tui_keybindings(kb, *, input_area)

Called after Hermes registers its own keybindings and before the layout is built. Add your keybindings to kb.

def _register_extra_tui_keybindings(self, kb, *, input_area):
    pass  # default: no extra keybindings

Parameters:

• kb — The KeyBindings instance for the prompt_toolkit application
• input_area — The main TextArea widget, if you need to read or manipulate user input

def _register_extra_tui_keybindings(self, kb, *, input_area):
    cli_ref = self

    @kb.add("f3")
    def _clear_input(event):
        input_area.text = ""

    @kb.add("f4")
    def _insert_template(event):
        input_area.text = "/search "

Avoid conflicts with built-in keybindings: Enter (submit), Escape Enter (newline), Ctrl-C (interrupt), Ctrl-D (exit), Tab (auto-suggest accept). Function keys F2+ and Ctrl-combinations are generally safe.

_build_tui_layout_children(**widgets)

Override this only when you need full control over widget ordering. Most extensions should use _get_extra_tui_widgets() instead.

def _build_tui_layout_children(self, *, sudo_widget, secret_widget,
    approval_widget, clarify_widget, model_picker_widget=None,
    spinner_widget=None, spacer, status_bar, input_rule_top,
    image_bar, input_area, input_rule_bot, voice_status_bar,
    completions_menu) -> list:

The default implementation returns (any None widgets are filtered out):

[
    Window(height=0),       # anchor
    sudo_widget,            # sudo password prompt (conditional)
    secret_widget,          # secret input prompt (conditional)
    approval_widget,        # dangerous command approval (conditional)
    clarify_widget,         # clarify question UI (conditional)
    model_picker_widget,    # model picker overlay (conditional)
    spinner_widget,         # thinking spinner (conditional)
    spacer,                 # fills remaining vertical space
    *self._get_extra_tui_widgets(),  # YOUR WIDGETS GO HERE
    status_bar,             # model/token/context status line
    input_rule_top,         # ─── border above input
    image_bar,              # attached images indicator
    input_area,             # user text input
    input_rule_bot,         # ─── border below input
    voice_status_bar,       # voice mode status (conditional)
    completions_menu,       # autocomplete dropdown
]

Layout diagram

The default layout from top to bottom:

1. Output area — scrolling conversation history
2. Spacer
3. Extra widgets — from _get_extra_tui_widgets()
4. Status bar — model, context %, elapsed time
5. Image bar — attached image count
6. Input area — user prompt
7. Voice status — recording indicator
8. Completions menu — autocomplete suggestions

Tips

• Invalidate the display after state changes: call self._invalidate() to trigger a prompt_toolkit redraw.
• Access agent state: self.agent, self.model, self.conversation_history are all available.
• Custom styles: Override _build_tui_style_dict() and add entries for your custom style classes.
• Slash commands: Override process_command(), handle your commands, and call super().process_command(cmd) for everything else.
• Don’t override run() unless absolutely necessary — the extension hooks exist specifically to avoid that coupling.