What Is Sunlith? The Beginner's Guide to the Android Calendar Your Coding Assistant Can Edit
CodexFuse Team · 2026-11-05T22:22:51.705Z · 17 min read min read
What Is Sunlith? The Beginner's Guide to the Android Calendar Your Coding Assistant Can Edit
What Is Sunlith?
What is Sunlith? Sunlith is a free, open-source Android calendar app that lets a coding assistant on your computer read, create, change, and delete events on your phone. It is a sunlith android calendar with a twist: instead of syncing through Google, it pairs your phone with a small Node.js companion over Wi-Fi or Tailscale, so your assistant talks to the calendars stored on the device itself.
The project is brand new. The repository was created on November 4, 2026, by GitHub user SunSinD, and it carries the plain tagline "A clean calendar app." It is published under the Apache License 2.0, and the app itself has no subscription of its own, though the coding assistant you connect may need its own account.
Sunlith is also easy to confuse with two unrelated names, so check the spelling before you download anything. Sunlitt is a sunlight-tracking app, and SunLith Energy is a solar and lithium company. Neither has anything to do with this calendar.
Sunlith ships as an APK from its GitHub releases page, and the release notes publish a SHA-256 hash for the file. Before you install any APK from the internet, check its fingerprint with a SHA-256 hash generator so the file you downloaded matches the one the author published. The companion runs on your own computer, not on a rented server, but the pattern will feel familiar if you already run services on VPS hosting, where a small machine you control quietly does work for you in the background.
Sunlith at a Glance
| Fact | Detail |
|---|---|
| What it is | An open-source Android calendar app with a computer companion for coding assistants |
| Platform | Android 8.0 or newer; companion runs on Windows, macOS, and Linux with Node.js 22 or newer |
| License | Apache License 2.0 |
| Price | Free, with no subscription of its own; your assistant may need its own account |
| Latest release | v0.2.0, published November 5, 2026, adding the direct phone connection |
| Repo created | November 4, 2026 |
| Assistant connection | Local MCP companion over stdio; eight assistant guides, plus Gemini CLI in the setup guide |
| Google account | Not needed in direct mode; a separate Google connection remains available |
On the phone, Sunlith works as an ordinary calendar first. It shows month, week, and day views, supports all-day dates, repeat presets, notes, locations, and reminders, and includes a resizable agenda widget that shows 1 to 31 days. It uses the calendars already stored on your phone, and you can create an on-device calendar or import and export .ics files through the system file picker.
Android 8.0, released on August 21, 2017, is a low bar that covers most Android phones still in use, though the version itself stopped receiving OS updates in 2021.
The assistant half is what makes it different. The app has no built-in model and no chat of its own. Its private calendar server runs only while you enable the computer connection, and the phone shows a notification the whole time it is on.
How Sunlith Works in Five Steps
Sunlith connects three pieces: the Android app on your phone, a Node.js companion on your computer, and the coding assistant you already use. The setup takes five steps.
- Install the Sunlith APK on your Android phone.
- Open Settings, then Computer connection, and choose which calendars to share.
- Save the pairing file and send it privately to your computer.
- Start the Node.js companion on your computer.
- Add the companion as an MCP server in your coding assistant, then ask it to manage your calendar.
The pairing file is the key to the whole arrangement. It contains an access key, so send it privately and never paste its contents into a chat or publish it anywhere. The companion verifies the phone certificate before it sends the pairing key, and pairing grants access only to the calendars you chose.
The connection itself is private by design. It uses HTTPS with a pinned phone certificate, and your computer and phone must be on the same Wi-Fi network or the same private Tailscale network. Sunlith provides no public relay, so there is no cloud middleman holding your events.
You can stop the connection or unpair it at any time. The phone keeps showing its notification while the connection is on, so you always know when your assistant can reach your calendar.
Which Coding Assistants Work With Sunlith?
People phrase the wish plainly: "claude code edit android calendar." With Sunlith, that wish works through the local MCP companion, which lets Claude Code list calendars and create, change, or delete events on the phone you paired. That is the whole pitch of the sunlith coding assistant calendar: your assistant edits the calendar you already carry, instead of asking you to move your life into another app.
First-run setup offers eight assistant guides, and the setup guide also covers Gemini CLI, so nine assistants are documented in total. Each guide gives the config file and the command to check the connection.
| Assistant | Setup | Check command |
|---|---|---|
| Codex | codex mcp add, or ~/.codex/config.toml | codex mcp list |
| Claude | claude mcp add | claude mcp list |
| Cursor | ~/.cursor/mcp.json | See the setup guide |
| Grok | ~/.grok/config.toml | grok mcp doctor sunlith |
| OpenCode | ~/.config/opencode/opencode.json | opencode mcp list |
| Antigravity | ~/.gemini/config/mcp_config.json | /mcp |
| Muse Code | ~/.config/muse/settings.json | /mcp |
| Pi | ~/.pi/agent/mcp.json | pi mcp list |
| Gemini CLI | Covered in the setup guide | See the setup guide |
One honest note matters here. The eight guides are host-side setup instructions, not claims of live account testing. The companion itself was tested with the official MCP SDK client over stdio, and end-to-end use in each client has not been tested by the author.
If you have never driven one of these tools from the terminal, our guide to how to use Claude Code walks through the basics first.
What Your Assistant Can Do With Your Calendar
Once paired, the companion can read, create, change, and delete events directly on your phone, including on-device calendars. The direct mode uses seven calendar tool names, plus an import tool for calendar files.
| Action | What happens |
|---|---|
| List calendars | Shows the calendars you chose to share during pairing |
| List events | Returns up to 100 items per page; each event query covers at most 366 days |
| Create events | Adds a new event, with notes, location, and reminders |
| Change events | Reads the current etag first, then applies the change |
| Delete events | Removes the event from the phone calendar |
| Import a calendar file | Direct import accepts files up to 256 KiB; larger files use the phone picker |
| Check the time | Uses the phone clock and timezone by default |
The numbers in that table are small, but they set real expectations. A 366-day window is just over a year, so one query covers a full year of events. The 256 KiB import cap is 262,144 bytes, which is plenty for a personal backup but too small for a large exported archive, so big files go through the phone picker instead.
Sunlith also works without any computer at all. You can ask a mobile assistant that can create files for a downloadable .ics attachment with your event details, open or share it with Sunlith, choose a destination calendar, and confirm the import. Compatible Android assistants can also open an event draft for you to review and save.
These handoffs need no computer and no Google account.
What Sunlith Cannot Do Yet
Sunlith is honest about its limits, and the list is long because the project is days old. Knowing the limits before you install it saves you from discovering them on a meeting that matters.
| Limit | Detail |
|---|---|
| Guest meetings | The editor blocks meetings with attendee records, and the companion adds no guests and sends no invitations |
| Recurring events | Edits and deletes apply to the whole series only; single-occurrence edits and "this and following" splits are blocked |
| Connection type | There is no HTTP MCP gateway; the companion is a local stdio MCP server, and a client without local stdio MCP support needs another adapter |
| Background reliability | Phone background restrictions can interrupt the connection, and it does not start automatically after reboot |
| Network reach | Computer and phone must share Wi-Fi or a private Tailscale network; no public relay is provided |
| Desktop experience | Command-line companion only; no desktop calendar, browser setup wizard, or native desktop installer |
| Other accounts | No CalDAV adapter and no Outlook or Microsoft Graph adapter |
The meeting limit is the one most people will hit first. If an event already has guests, the companion rejects edits and deletes of it, so you still need your regular calendar app for those events. Recurrence is also basic: it accepts a single simple RRULE with daily, weekly, monthly, or yearly frequency, and complex recurring exceptions are blocked.
The background limit matters just as much. A foreground service alone does not guarantee network access while the phone is in deep idle, and the author's own testing notes say real-device Tailscale connectivity and Samsung battery behavior still need phone testing. Keep Sunlith running with its connection notification, and allow background battery use if your phone stops it.
Sunlith vs Google Calendar: What Changes When You Skip Google
The obvious question is why anyone needs Sunlith when Google Calendar already exists. The sunlith vs google calendar comparison comes down to where your events live and who has to approve the connection.
| Question | Sunlith direct mode | Google Calendar |
|---|---|---|
| Needs a Google account? | No | Yes |
| Where events live | On your phone, in Android storage | On Google servers |
| Phone-only calendars | Yes, including on-device calendars | No; Google only sees Google-account calendars |
| How an assistant connects | Local MCP companion over pinned HTTPS | Hosted Calendar MCP server at calendarmcp.googleapis.com |
| What setup requires | APK, Node.js 22 companion, pairing file | Developer Preview membership, a Google Cloud project, and OAuth |
| Guest meetings | Blocked | Supported |
| Maturity | Two days old, pre-1.0, 1 star | Mature and widely used |
Google does now offer an official hosted Calendar MCP server, and it lets agents list calendars, retrieve events, check availability, and create, update, and delete events. But it is gated behind membership in the Google Workspace Developer Preview Program, a Google Cloud project, and an OAuth setup, and for Claude it requires an Enterprise, Pro, Max, or Team plan. It is not a built-in feature of the Google Calendar app, and it only reaches Google-account calendars.
Sunlith's direct mode skips Google entirely, which is its whole advantage and its whole risk at once. You keep your events on your own phone with no account and no cloud, but you take on a two-day-old beta with a dev-signed APK instead of a mature service. The first three releases of Sunlith could only control Google Calendar, by the way.
The direct phone connection that makes the Google comparison interesting arrived only in v0.2.0.
Sunlith also keeps a separate Google connection for people who prefer account sync. That mode needs your own Google Desktop OAuth client, requests only the calendar.events and calendar.calendarlist.readonly scopes, and cannot change sharing permissions or create and delete calendars. OAuth apps in external testing mode usually need authorization again after seven days.
The Pairing Model: Wi-Fi, Tailscale, and a Pinned Certificate
Sunlith's security story is refreshingly simple: nothing leaves your local network, and the pairing file is the only secret. The companion speaks the Model Context Protocol, the open standard that lets AI tools call outside data sources, and it does so over a private connection that only you set up.
Tailscale is the reason the pairing works away from home. Third-party explainers describe Tailscale as a WireGuard-based mesh VPN that puts your phone and computer on the same private network, called a tailnet, so they can reach each other directly without port forwarding or a public relay. Sunlith's own guide recommends the phone's Tailscale address for a stable connection, because a Wi-Fi address can change and force you to pair again or update the baseUrl in the private file.
Three rules keep the pairing safe. First, treat the pairing file like a password, because it contains an access key. Second, remember that the companion verifies the phone certificate before sending the pairing key, so a stranger on your network cannot impersonate your phone.
Third, pairing grants access only to the calendars you chose, so a calendar you never shared stays out of reach.
Ordinary phone requests have a ten-second network deadline, and imports allow up to three minutes. That is generous for a local connection, and it is one more sign that Sunlith expects your phone and computer to be close, either on the same Wi-Fi or on the same tailnet.
How to Check the Project Before You Install It
Early software deserves a check before it touches your calendar, and Sunlith makes the check easy because everything is public. Read the release notes, confirm the download hash, and look at the test record before you trust it with real events.
Start with the releases page. Four releases shipped in about five and a half hours, and the notes say plainly what each one changed, including the warning that v0.1.0 was a beta testing build. Then verify the download: the v0.2.0 APK has a published SHA-256 of b76ae486868cc1a0a624360e0c87c2a7da03a3a5083614cd425041da6870e9c9, and the release ships a SHA256SUMS.txt file so you can check every file in the download.
Know what you are installing, too. The published APK is signed with a development key, and production signing is planned before a stable release. That is normal for a project this young, but it means you should install the published APK for updates, because a local or CI build with a different key will not preserve your app data.
Back up important calendars before testing changes or imports, because imports are not one transaction and they report unsupported records instead of failing cleanly. The test record is genuinely solid for a two-day-old project: the verified build passed 20 Android unit tests, 43 tests on an API 30 emulator, 44 on an API 36 emulator, and 31 desktop MCP tests, and the v0.2.0 direct-connection checks added 44 desktop tests plus 27 API 30 and 27 API 36 tests each. A full backup import moved 215 events with zero skipped, and a retry correctly detected all 215 as duplicates.
Who Sunlith Fits — and Who Should Wait
| You | |
|---|---|
| Fits | You live in Claude, Codex, Cursor, or another supported assistant and want it to manage your schedule |
| Fits | You keep calendars on your phone and do not want a Google account in the middle |
| Fits | You enjoy testing early open-source tools and you back up your data first |
| Wait | Your calendar is full of meetings with guests and attendees |
| Wait | You need to edit single occurrences of recurring events |
| Wait | You want a polished, supported product rather than a days-old beta |
| Wait | You are uncomfortable installing an APK that is not production-signed |
Sunlith fits a narrow person right now: a developer whose coding assistant already runs their workday, who keeps calendars on an Android phone, and who is happy to trade polish for control. Everyone else should watch the repository and wait for a stable release. CodexFuse does not offer a Sunlith tool, and this article is a guide to the project, not a promise of one.
The First Two Days: Releases, Downloads, and Reception
Sunlith moved fast in its first two days, and the numbers tell that story better than adjectives. The repository is roughly 27 hours old at the time of writing, and it already has 11 commits, which averages about one commit every two and a half hours since it was created.
| When (UTC) | What happened |
|---|---|
| Nov 4, 18:56 | Repository created on GitHub |
| Nov 4, 22:32 | v0.1.0 beta: companion controls Google Calendar only |
| Nov 5, 01:39 | v0.1.1: calendar UI fixes and a new launcher icon |
| Nov 5, 02:14 | v0.1.2: artwork-only update |
| Nov 5, 04:03 | v0.2.0: adds the direct phone connection |
| Nov 5, 05:33 | Show HN post by the author: 2 points, 0 comments |
Four releases landed in 331 minutes, from 22:32 to 04:03, which is about one release every 110 minutes. The v0.2.0 APK is 20,335,436 bytes, about 19.4 MB, while the companion ZIP is 76,427 bytes, about 74.6 KB, so the phone app is roughly 266 times the size of the computer companion. Downloads were tiny at fetch time: 8 for the APK, 3 for the companion, and 1 for the checksum file, or 12 file downloads in total.
Reception so far is almost nonexistent, which is expected for a project this young. The Show HN post earned 2 points and 0 comments, the repository has a single star and 0 forks, and no independent explainer, how-to, review, or news article about Sunlith exists yet. That is also why this article leans on the repository's own README and docs: they are the only sources that exist, and they are unusually thorough for a two-day-old project.
Sunlith, SupaYatta, and the Agent-Tool Family
Sunlith opens the agent-calendar lane of the AI agent tools family, and it sits beside tools that do different jobs for the same kind of user. The closest sibling is SupaYatta, which watches coding-agent sessions. What SupaYatta is matters here because it draws the line clearly: SupaYatta watches sessions, while Sunlith edits calendars, so the two never compete for the same job.
The pattern is the same one this site has followed across the agent-tools family. Each new tool gets one page that covers its whole intent cluster, instead of splitting variations across rival articles. This page is the pillar for the agent-calendar lane, and it covers the whole cluster: what Sunlith is, the Android calendar it provides, the coding-assistant calendar connection, editing an Android calendar from Claude Code, and the Google Calendar comparison.
Sources
- Sunlith GitHub repository, README — github.com/SunSinD/Sunlith (fetched November 6, 2026)
- Sunlith releases — github.com/SunSinD/Sunlith/releases (fetched November 6, 2026)
- Sunlith setup guide, docs/AI-INTEGRATION.md — github.com/SunSinD/Sunlith/blob/main/docs/AI-INTEGRATION.md (fetched November 6, 2026)
- Sunlith testing record, docs/TESTING.md — github.com/SunSinD/Sunlith/blob/main/docs/TESTING.md (fetched November 6, 2026)
- Show HN: Sunlith, an Android calendar you can control through MCP — news.ycombinator.com/item?id=50375585 (posted November 5, 2026)
- Google Calendar MCP server guide — developers.google.com/workspace/calendar/api/guides/configure-mcp-server (fetched November 6, 2026)
- Google Calendar API v3 reference — developers.google.com/workspace/calendar/api/v3/reference (fetched November 6, 2026)
- Claude Code overview — code.claude.com/docs/en/overview.md (fetched November 6, 2026)
- Android Oreo — en.wikipedia.org/wiki/Android_Oreo (fetched November 6, 2026)
- Tailscale explainers (third-party descriptions) — rafaelpfister.ch, privacygear.nl, ssdnodes.com (fetched November 6, 2026)
Frequently Asked Questions
What is Sunlith?
Sunlith is a free, open-source Android calendar app that lets a coding assistant on your computer read, create, change, and delete events on your phone. It pairs the phone with a small Node.js companion over Wi-Fi or Tailscale using a pinned-certificate HTTPS connection, and it needs no Google account in direct mode. The project was created on November 4, 2026, and is published under the Apache License 2.0.
Can Claude Code edit my Android calendar with Sunlith?
Yes. Install the Sunlith APK, enable the computer connection, save the pairing file, start the Node.js companion, and add it as an MCP server with claude mcp add. Claude Code can then list calendars and create, change, or delete events on the calendars you shared.
It cannot edit meetings that already have guests, and it cannot change a single occurrence of a recurring event.
Does Sunlith need a Google account?
No, not in direct mode. Direct mode talks to the calendars stored on your phone, including on-device calendars, with no Google account at all. A separate Google connection remains available if you prefer account sync, but it needs your own Google Cloud project and Desktop OAuth client.
Is Sunlith safe to install?
It is early software, so treat it that way. The APK still carries development signing, production signing is planned before a stable release, and the project is only a couple of days old. Verify the published SHA-256 before installing, back up your calendars first, and only share the calendars you actually want your assistant to touch.
Can Sunlith edit meetings with guests?
No. Events that already have guests are off limits: the companion adds no guests and sends no invitations. It also rejects edits and deletes of events that already have guests, and recurring edits apply to the whole series only.
Use your regular calendar app for guest meetings.
