Chat with the model you choose
Write, brainstorm, explain documents, and ask questions. Choose a different model for each conversation.
ACASTUS AI by ASTRIX
Your AI workspace. Your choice of models.
Chat, search the web, and work on code in one Windows app. Connect cloud models with your own API keys, or run supported local models on your PC.
Start free in your browser with Acastus on the web Beta. Website plans: Plus $5 a month, Pro $10 a month.
Checking the web server…
- Windows 10 and 11
- Free plan available
- Cloud provider charges may apply
What it does
From a question to getting things done
Find answers with sources
Search for current information and follow clickable sources to see where answers came from.
Work on real code Pro
Open a project folder and describe what you want to build or fix. Review proposed changes, run tests, and undo applied edits using checkpoints.
Models
Choose how your AI runs
Free cloud models
Connect a provider offering free models using your own API key. Provider limits apply.
Paid cloud models Pro
Use supported paid providers with Pro. You choose when to enable them, and provider usage is billed separately.
Local models
Run supported models on your own computer. ACASTUS helps you understand which models fit your hardware.
An API key connects ACASTUS to your account with an AI provider.
Privacy
Keep control of your data and spending
Stored on your PC
Your chats and settings are stored on your PC. Saved desktop API keys are encrypted using Windows.
Sent only where you choose
When you use a cloud model, the content needed for your request is sent to your selected provider. Local models run on your computer; web searches and online tools still connect to external services.
No surprise costs
Free-only mode is on by default. ACASTUS never silently switches you to a paid model. Usage figures are labeled as reported, estimated, or unknown.
Get started
Get started in three steps
- 1
Install ACASTUS
Install it on your Windows PC.
- 2
Connect a model
Use a provider API key, or set up a supported local model.
- 3
Start a conversation
Ask a question, attach a document, or search for information. With Pro, open a project folder to start a coding task.
Pricing
Start free. Upgrade when you need more.
Plans for Acastus on the web Beta at astrixz.com/ai. The Windows app is a separate free download.
Free
$0
- Iris: chat, web search with sources, and photos
- 1M usage per week, 20K every 3 hours
- Use it in your browser, nothing to install
- Built-in data tools
Plus
$5per month
- Everything in Free
- Hermes: faster, smarter answers
- 7M usage per week
- 200K usage every 3 hours
Pro
$10per month
- Everything in Plus
- Athena and Apollo: the strongest Acastus models, with deeper thinking
- 100M usage per week, 1M every 3 hours
Website plans, billed monthly, cancel any time. Your key arrives by email: paste it in Your plan on astrixz.com/ai. Plan keys work on the website only, not in the Windows app. When a subscription ends, its key stops working. Acastus on the web is in beta.
Download
Get ACASTUS AI free.
Windows 10 / 11Acastus AI Desktop · 43 MB · x64 · just open it and chatDownload for Windows
Android BetaAPK · 3 MB · Android 8+ · install from your phoneDownload Android beta
Acastus AI Desktop 1.0.1. Verify the download with SHA256SUMS.txt. Want the full Acastus workspace (your own models, Code, projects)? Download Acastus AI 2.16.7 (SHA256SUMS).
FAQ
Questions before you start
Is ACASTUS an AI model?
ACASTUS is an app that connects you to AI models and gives them a workspace with search, tools, and coding features.
Do I need a subscription?
No. Free works with no subscription. Plus ($5/month) and Pro ($10/month) are monthly plans for Acastus on the web (beta), cancel any time; your key stops working when the subscription ends. Connected providers in the Windows app may charge separately.
Can I use it offline?
Local-model chat can run without a cloud provider once the required model is installed. Cloud models, web search, and online data tools require internet access.
Do I need a powerful computer?
Hardware requirements depend on the model. Cloud models run with the provider; local models use your PC's memory and processing power.
Does web search need another key?
Some built-in sources work without one. Broader web search requires a supported search-provider key.
Can I use it on Android?
Yes, two ways. Open astrixz.com/ai in your phone's browser (nothing to install), or try the Android app beta, where anyone can chat with Iris free just like on the website: download the APK on your phone and open it (Android asks once to allow installs from your browser). It's a beta, so expect rough edges. Verify it with SHA256SUMS.txt.