Your T1 Arc guide.

Install on your phone.

T1 Arc supports Android 8.0 and newer. You do not need to build anything or use a computer.

1. Open the latest official T1 Arc release on your Android phone.
2. Under Assets, download the phone APK. Its name starts with T1-Arc-v and ends with .apk. The version number in the middle changes with updates.
3. Open the download. If Android asks, allow installs from the browser or Files app opening it, then return to the installer.
4. Choose Install, open T1 Arc and follow the onboarding tour.

Files with Wear or a face name are optional watch downloads. Source code, .sha256 and .build.json files are not the phone app.

Updating keeps your records.

Create an encrypted backup, download the newer phone APK and install it over the existing app. Do not uninstall first: Android removes local app data when you uninstall. If Android reports a signature or package conflict, keep your working installation and contact support.

In the app, About T1 Arc → Check for updates performs a manual check. Nothing downloads or installs automatically.

Backups and a new phone.

Export an encrypted backup and keep its password separately. Restore it in T1 Arc on the new phone, then reconnect your services and grant Android permissions. Backups exclude service passwords and API keys. There is no password-recovery service.

Meet Tarv1s.

Ask about your recorded glucose, insulin, food and health. Supported exact questions are calculated on the phone. Broader questions can use an optional direct OpenAI connection.

The answer shown on the website is a real local calculation. Its expanded details show the period, number of readings and coverage. Answers should acknowledge missing evidence; a pattern does not establish a medical cause.

Free local answers. Optional paid AI.

T1 Arc is free, with no subscription or AI markup. If you connect OpenAI, its API usage is billed directly to your own account. A ChatGPT subscription does not include API credit.

The cost varies with the model, selected evidence and answer length. Check OpenAI’s current API prices and your usage dashboard. Set suitable spend controls before use; budget alerts alone are not a spending cap.

For scale: at GPT-5.6 Luna’s standard text rates checked on 17 September 2026, 10,000 input tokens and 2,000 billed output tokens cost US$0.0044 — less than half a US cent. This is an illustration, not an average or a promise. Longer context, reasoning, repeat requests, tax and currency conversion can change the total. The model pricing linked above is authoritative.

Connect your own key.

1. Open the OpenAI API platform, create a dedicated project and review its billing and spending controls.
2. Create a standard project API key. Keep it private.
3. In T1 Arc, open Tarv1s → conversation history → Tarv1s settings.
4. Paste your key and choose Save key on this phone. The first broader question checks service access and billing.

Saving the key does not send health records. When you submit an eligible question, the question and bounded relevant evidence go directly from the phone to OpenAI, together with a random safety identifier and normal connection metadata. T1 Arc’s maintainer does not receive that request.

OpenAI’s own API data controls apply. The key uses Android secure storage and is excluded from backups. A compromised phone or modified app can put it at risk; use a dedicated project and revoke the key if exposed.

Saved answers are snapshots. Later imports do not rewrite them. Tarv1s does not calculate insulin doses or replace medical advice.

When will records arrive?

A successful connection check means the source answered. It does not mean it supplied a new record. Check when the measurement happened.

Cloud glucose

LibreLinkUp, Dexcom Share and Medtrum can only supply readings already uploaded to their cloud. Your sensor or controller must get them there first.

Glooko

Delayed insulin, pump and glucose history. Recent-history checks become due about hourly, but records may already be behind when Glooko supplies them. There is no guaranteed delay. Today’s insulin total can be incomplete and change later.

Health Connect

Foreground checks become due about every five minutes. A wearable may need to sync with its own app before that app writes records to Health Connect.

Hevy

Checks for saved or changed workouts become due about every 30 minutes. You can also choose Sync new and changed workouts.

Nightscout, xDrip and notifications

Delivery depends on the configured uploader, local service or notification-producing app, and the permissions you grant.

These are scheduling intervals, not delivery guarantees. Android can defer background work, and providers, permissions, battery restrictions and the network also affect it. Historical backfills may take longer.

If glucose stops updating.

1. Compare the reading time with the provider’s official app or display.
2. If both are old, check the uploading device and its connection.
3. If the official app is current, open the source in T1 Arc Settings and use its connection check. Check any error, account region and network or VPN.
4. If it repeats, send a reviewed problem report from Help and support.

A delayed or stale value is a last-known reading. Keep your medical device’s official display and alerts available.

Choose your sources.

The app offers LibreLinkUp, Dexcom Share, Medtrum, Nightscout and xDrip glucose connections, plus configurable notification capture. Glooko supplies historical records; Health Connect and Hevy bring in other health and activity information.

Choose the account’s actual provider region. Country preferences set defaults, but do not make every service available in every country or translate the English interface.

Real-account coverage varies. Nightscout and xDrip have been exercised with controlled services; that does not prove every uploader or device combination. Dexcom and Medtrum have not been validated with the creator’s own live accounts. These are independent integrations, not manufacturer endorsements.

Strava data comes through Health Connect, not a direct Strava sign-in. Health Connect requires the source app to write the record and you to grant T1 Arc access.

Keep food logging simple.

Use Scan, Read label, Quick carbs or Enter food in Add food. Saved foods, meals, recipes and copying from another day can make repeat entries quicker.

Barcode and search coverage varies. Label reading runs on the phone and proposes values for review; it can miss decimals, columns or small print. Check the label amount, units and every value before saving, then choose the portion you ate.

Choose the pack’s format, including for imported food. UK/EU carbohydrate is separate from fibre; do not subtract fibre again. US labels include fibre within Total Carbohydrate. The app keeps the declared values and does not automatically turn them into a treatment or dosing calculation.

Food, meal and recipe photos are optional and kept in the encrypted local database. A photo does not automatically estimate nutrition.

Which watch setup do I need?

The companion requires Wear OS 3 or newer. T1 Arc’s phone wizard installs the bundled companion on compatible watches. Use the step-by-step watch guide.

The five separate faces require Wear OS 4 or newer. The phone’s face chooser installs bundled designs on supported Wear OS 6 watches. Wear OS 3 uses the companion, tile or supported complications.

Wear OS 4 and 5 face installation needs the separate face APK and a computer. Use the watch installation instructions for that route; do not assume the phone face chooser installs it. You only need the faces you choose.

Earlier Samsung Tizen watches, fitness bands and Apple Watch are not supported. Galaxy Watch 8 has been tested physically; emulator checks do not establish physical testing of every watch.

If something does not work.

Open Settings → Help and support → Report a problem. Describe the steps and optionally add technical diagnostics. Read the preview before sending. Reports go privately to support, not to public GitHub issues.

The optional summary contains selected event codes, app/device details and times. It is not a complete native crash log and cannot guarantee the reason for every failure. You can also email support@t1arc.com.

Never send passwords, API keys, backups or a database. Public issues should use invented example data. See how support reports are handled. Support is not a medical or emergency service.

Open source. Open to ideas.

Explore T1 Arc on GitHub. Read the code, raise issues and propose changes through pull requests. Maintainer review is required before contributions are accepted. Using the app does not require a GitHub account.

Find the installation guide, regional capabilities, watch setup and contributing guide in the repository.

Software and media have different licences.

T1 Arc’s software is MIT licensed. The app includes third-party components and notices with their own terms. See the full software licence and third-party notices.

The website’s Android model is rendered with Three.js, under its MIT licence. Real app screenshots show the creator’s records, shared with permission, or explicitly labelled emulator examples.

The film’s music and narration are not reusable MIT assets. See the media terms below.

Demo credits and media use.

T1 Arc demo | AI narration: elevenlabs.io

• AI narration: George via ElevenLabs.
• Music: Signal Drift, created with Suno.
• App, demonstration and edit: T1 Arc.

The 90-second film is an edited demonstration, not a real-time performance benchmark. Some scenes show the creator’s own records with permission. The food scene shows a draft. The examples are not promised health outcomes.

The soundtrack and narration were made on free plans and shared as part of this personal, non-monetising project. Do not reuse them in a fork or commercial campaign without the necessary rights. A later subscription should not be assumed to change the rights attached to an earlier recording.

See Suno’s free-plan guidance and ElevenLabs’ publication guidance. The required narration credit is included in the film’s title.

Watch the film · Read the captions