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Castor - Private AI Chat

140 BIG Developer Team Productivity

Private AI chat with local models, Gemini, OpenAI, voice, and vision.

Downloads
86+
on Google Play
Price
Free
No in-app purchases
Updated
Jul 31
2026 · v1.0.5
Get it onGoogle Play See alternatives

Screenshots

  • Castor - Private AI Chat screenshot 1
  • Castor - Private AI Chat screenshot 2

About Castor - Private AI Chat

Castor is a privacy-first AI chat application for Android.

**Key Features:**
* **On-device AI:** Run supported local models directly on your device with llama.cpp or LiteRT-LM.
* **Gemma support:** Use Gemma 4 E2B through the LiteRT-LM runtime with secure model delivery.
* **Multi-provider chat:** Switch between local AI, Google Gemini, and OpenAI depending on your task.
* **Vision support:** Attach images and chat about visual content with supported VLM models.
* **Voice tools:** Use Android speech recognition and text-to-speech where available.
* **Prompt templates:** Save and reuse your favorite instructions for repeated workflows.
* **Chat history:** Conversations are stored on your device so you can return to them later.

**About local models:**
* Some models require a first-time download. Wi-Fi is recommended.
* OpenCL acceleration is available on supported Adreno GPU devices.
* Local execution keeps eligible prompts and responses on your device.

Castor gives you a clean AI workspace that can move between private on-device inference and powerful cloud models.

What’s new

Version 1.0.5 · Updated July 31, 2026

- Changed local AI model download authentication to anonymous authentication, removing Google account selection and profile sharing. - Fixed an issue where the model download button was unavailable in some environments. - Improved stability.

Alternatives to Castor - Private AI Chat

Looking for apps like Castor - Private AI Chat? Here are 6 similar Android apps on Google Play. The highest rated is Tutor Lily: AI Language Tutor (4.1/5), and 5 of the 6 are free to download.

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