The missing piece in a self-hosted CalDAV stack: a web UI for Tasks.org

Tasks.org syncs Android tasks to CalDAV cleanly. There is no web UI for that data. After a year of reaching for my phone to edit a todo at my desk, I built one. Here is the gap I noticed in the self-hosted ecosystem, and how I closed it without breaking the standards-first contract most of us signed up for.

The result is open source at github.com/spy4x/caldav-tasks-web and live at todos.antonshubin.com.

The gap in the stack

Tasks.org is the strongest Android task manager and it syncs to CalDAV. The data lives on a server you control. The moment you sit at a desk, that data is unreachable from a browser — no conformant client exists for the web.

The data is fine. The standard is fine. The clients are missing.

Why I didn't reach for Nextcloud Tasks

Nextcloud is a whole suite, not a CalDAV server. People who chose Radicale or Stalwart on purpose shouldn't need to deploy a Nextcloud instance to edit a todo on desktop. The fix had to assume the CalDAV server is the only piece already running.

If you run Radicale, Nextcloud, Baikal, or Stalwart — that is your calendar server. This PWA is the missing task UI for it.

Architecture: CalDAV as the only source of truth

VTODO files live on the CalDAV server. The PWA is a stateless client. SQLite in the API container holds user accounts and AES-GCM-encrypted server credentials and nothing else. Switch CalDAV servers and no todos move.

That property mattered enough to me that I tested it. The deployed instance runs on Stalwart now; it ran on Radicale before that. The migration was a config string change. Zero todos moved. That is the test the architecture had to pass.

CQRS in a UI app, and why it fits

The read/write split maps cleanly onto CalDAV's GET versus PROPPATCH/PUT/DELETE. Each side tests in isolation; the CalDAV adapter is the only piece that knows the protocol. Radicale and Stalwart both speak through the same PROPFIND/PROPPATCH/PUT/DELETE interface, so adding a third server is a new adapter class, not a chain of if (serverType === ...) blocks.

The CalDAV XML responses vary more than they should. Radicale uses the default namespace and emits lowercase <d:response>. Stalwart emits uppercase <D:response> and <A:response> for the caldav namespace. Substring-matching "calendar" in the response body matches the user's principal home on top of actual calendars. The parsers have to be case-insensitive, prefix-tolerant, and filter calendars by <(prefix:)?calendar/> inside <resourcetype>. The bug-fix branch for this is its own commit on the public repo — anyone hitting the same issue against Stalwart will find it.

Preact Signals instead of hooks

VTODO state changes constantly — status, priority, due date, percent complete, complete vs active, filters, sort, tag toggles. Signals give surgical UI updates without a virtual DOM tree of hooks to debug. A hook-based version of this project would have spent most of its life chasing re-render storms.

The hooks-vs-signals debate is a real one and the right answer depends on the app. For a heavily stateful list of items with frequent mutations and dense filtering, signals win on clarity and on raw update count. The codebase is roughly half the size it would be in React.

Single binary on a single box

The deploy is a deno task deploy that rsyncs the project to a Hetzner box behind Traefik and runs docker compose up -d --build. Same Traefik that fronts the CalDAV server. Same SQLite file gets backed up by the same restic job that backs up the CalDAV data.

There is no Kubernetes. There is no service mesh. The whole stack fits on a single $20/month box and stays there. A real engineer reading this knows that's the right shape for a personal productivity tool.

What it cost and what it doesn't do

What it does: lists every CalDAV calendar with its colors, renders a touch-first task list with filters and tags and due dates, full VTODO editing, Kanban view, recurring tasks, multi-server per account. Credentials encrypted with AES-GCM at rest. PWA so it installs on a phone home screen.

What it doesn't do: no sync engine (it is a client, not a server). Single user per install. No recurring-task editor yet. No native mobile wrapper. No team features.

I built it for myself. I am sharing it in case it is useful to someone else running the same stack.

What would help

A second pair of eyes on the CalDAV adapter against Nextcloud Tasks and Baikal. They speak the standard but emit different propstat shapes for properties Radicale and Stalwart happily skip. UI feedback, especially on tablets — I have tested on phone and desktop but not on a 10-inch iPad. If you run Tasks.org on Android, this pairs with it directly — open an issue if anything breaks.

Closing

Self-hosting is a stance, not a chore. Every SaaS-shaped tool that wants to be the source of truth is a small erosion of that stance. The gap in the self-hosted CalDAV stack was real, and fixing it didn't need to be enterprise-grade — it just needed to honour the contract: the server you trust, the format you control, the data you already have.

If you already run Radicale or Stalwart and want a desktop UI for the same data your Android phone sees, try it. The deploy script in the README is five commands.