Tendies

Tendies is a self-hosted trading PWA built around Capital.com market data and execution. It is optimized for mobile Safari and standalone iOS PWA use, with real-time charting, position planning, background-resume handling, and a custom chart orchestration layer on top of TradingView Lightweight Charts.

Stack

• SvelteKit 2
• Svelte 5
• TypeScript
• TradingView Lightweight Charts
• IndexedDB for local candle cache and state restore
• Node adapter for self-hosted deployment

What is interesting here

• iOS PWA resilience: the app handles resume, visibility gaps, and background wake-up edge cases that appear in real mobile usage.
• Functional core / imperative shell chart integration: Svelte reactivity captures intent, while a single RAF flush owns chart mutations.
• Structured runtime telemetry: chart, viewport, resume, and trading flows emit typed logs to make production-only timing bugs diagnosable.
• Local-first UX: the app keeps enough local state to restore quickly after reloads and intermittent mobile suspension.

The architectural rationale lives in architectural_decisions.md and decisions.md.

Getting started

Requirements

• Node.js 20+
• npm
• A Capital.com account

Install

npm install

Run in development

npm run dev

The Vite dev server binds to 0.0.0.0:24536. If mkcert certificates exist under ~/.local/share/mkcert/pwa/, HTTPS is enabled automatically for local iPhone/PWA testing.

Build

npm run build

This project uses @sveltejs/adapter-node. For a production-style local run after build:

node build

Authentication and local env

This repo does not ship live credentials.

For local development, you can optionally create a .env from .env.example to prefill the login form:

cp .env.example .env

These values are for local development only. Do not commit .env, and do not use this PUBLIC_* autofill path as a public demo deployment strategy.

iPhone / PWA testing

iOS standalone PWA behavior was a core design target for this project. For HTTPS-based local testing:

1. Generate a local certificate with mkcert.
2. Place the generated files at ~/.local/share/mkcert/pwa/key.pem and ~/.local/share/mkcert/pwa/cert.pem.
3. Start the dev server and open the app from your iPhone on the same network.
4. If you need the mkcert root CA, the app exposes it from /api/cert for manual installation on the test device.

Current status

• Personal tool, not a multi-tenant product
• No formal test suite yet
• Documentation focuses on design decisions and runtime observability