Privacy notice

Draft, under legal review

Last updated 28 October 2026

This notice says what personal data Kiln holds, where it goes and how long it is kept. Kiln is run by Hellmai Ltd (company number 16412231, registered in England and Wales).

Who is responsible

Hellmai Ltd is the controller of the data Kiln holds about your account and your builds. Contact: privacy@lumenflow.cloud.

For the people who use an app you build, you are the controller and Hellmai Ltd hosts the data for you. Processor terms for that are not in place yet.

What Kiln holds

For each account and app Kiln stores:

Account: your email address, display name and role.
What you give Kiln: prompts, plans, uploaded references (photos and links), brand settings and connection settings.
What Kiln makes: build runs and their events, check reports, versions of the app’s code, costs, and the app’s own database and users.
Sign-in records: the time and network address of sign-in attempts that use the passcode, kept to stop repeated guessing.
Logs: operational logs, such as lockouts, role changes and errors.

Why Kiln uses it

To give you access, plan and build your apps, host previews and published apps, limit spend, keep Kiln secure and answer your requests.

The legal bases are the agreement to give you Kiln (contract) and Hellmai’s interest in keeping Kiln secure and within its spend limits (legitimate interests). Kiln does not rely on consent.

Where it goes

Your prompts, plans, uploaded references and parts of your app’s code are sent through our model routing service to model providers so they can write the plan and the code. Where an app has an AI feature, the text its users type goes the same way, identified only by a salted code and not by their account.

The providers are Amazon Bedrock (London, eu-west-2, where that route is enabled), Mistral AI, OpenAI, Anthropic and Google. Traffic can reach United States regions only where the residency setting allows it. Hellmai does not use your content to train models. The providers handle it under their own terms.

Kiln is hosted on AWS in London (eu-west-2), which also holds its encrypted backups. GitHub receives an app’s code when you export it.

The sub-processors page lists every provider with its purpose and region.

Transfers outside the UK

Data moves from the UK to the EU, which the UK treats as adequate. Model providers, Stripe, Expo, GitHub and the sign-in edges of our platform database are in the United States. The safeguards for those transfers are being confirmed with legal advisers.

How long Kiln keeps it

Kiln has no general retention schedule yet. What it does today:

Account record: kept while the account exists. There is no self-service deletion. Ask by email and it is removed by hand.
Prompts, plans, build runs, check reports, versions and uploaded references: kept with the app. There is no fixed or automatic deletion period for these yet.
Short-lived build progress events: deleted after 30 days by default.
A deleted app: its running services and databases are removed. Kiln keeps the app’s history (prompts, plans, runs and reports) as an audit record, and the app’s workspace on our platform is not removed automatically. Both are deleted on request.
A sleeping preview keeps its data until the app is deleted.
Backups: encrypted nightly backups of app databases are kept in AWS in London for 35 days, and replaced versions for 7 days more. Data you delete can stay in backups for up to about 42 days.
Sign-in records and server logs: no fixed period yet.

Your rights

Under UK GDPR you can ask for a copy of your data, for it to be corrected or erased, to limit or object to its use, and to receive it in a portable form. Email the privacy address above from the address on your account. Hellmai answers within one month. There are no self-service controls for these yet, apart from the app export, which gives you an app’s code, history, database, users and settings.

If you are unhappy with an answer you can complain to the Information Commissioner’s Office (ico.org.uk).

Security

Secrets that Kiln stores for you are encrypted. Backups are encrypted. Kiln checks every build for exposed secrets and for missing database access rules before a preview or a publish. Kiln has not had an external security test, and no system is free of risk.

Children

Kiln is for people aged 18 and over.

Changes

Hellmai can change this notice. The date at the top of the page shows when it last changed.