Apps — Plexi Docs

Plexi apps render into panes through PGAP. The Python SDK is the default authoring path.

Python apps are sandboxed, not native subprocesses: they run through the CPython-in-WASM adapter inside their own wasmtime::Store, the same component boundary a Rust WASM app gets. Capabilities gate host APIs such as net.http, secrets.get, and ai.query on top of that sandbox.

Create an App

From inside a Plexi workspace:

plexi app init my-app

Outside a workspace, use --global.

This scaffolds a new app folder with:

my-app/
  manifest.toml    ← capabilities, entry point, metadata
  main.py          ← your app code
  tests/test_app.py ← AppHarness smoke tests
  .venv/           ← isolated Python runtime

Validate the app and write screenshots:

plexi app check ./my-app --png-dir /tmp/my-app-shots

Open an App

Pass the path to the app folder:

plexi app open ./my-app

The app opens in a pane. Use this during development; no marketplace install is required.

The App Pattern

SDK v3 apps are module-level init, update, and view functions. view() returns a component tree and must stay pure:

#!/usr/bin/env python3
from __future__ import annotations

from plexi_sdk import state
from plexi_sdk.effects import SetState, SetTitle
from plexi_sdk.events import KeyEvent
from plexi_sdk.ui import AppBar, Column, FooterKeys, Text


def init(size, args):
    return [SetTitle("My App"), SetState({"count": 0})]


def update(event):
    if isinstance(event, KeyEvent) and event.key == "return" and event.pressed:
        return [SetState({"count": state.get("count", 0) + 1})]
    return []


def view():
    return Column([
        AppBar("My App"),
        Text(str(state.get("count", 0)), bold=True),
        FooterKeys([("return", "increment")]),
    ], grow=True)

Canvas apps also return from view(): use Canvas(...) components and RenderFrame events for animation.

Capabilities

Declare what your app needs in manifest.toml:

[app.capabilities]
capabilities = ["secrets.get", "net.http"]

Common capabilities: secrets.get, net.http, fs.read, fs.write, ai.query, audio.record, timer.

Logging

Use plexi_sdk.log from init() or update(). Log lines are tagged with the app process in the host log.

from plexi_sdk import log


def init(size, args):
    log.info("my-app initialized")
    return []