Hi HN! We're excited to introduce "Karl" – a virtual friend you can text to share what's on your mind.

We created Karl because we found it incredibly helpful to have a sounding board and someone I could talk to anytime, day or night.

Karl isn't meant to replace real friendships but rather to act as a mediator and an additional point of contact. He remembers important details you share and can connect the dots between past events and current decisions.

Anyone can message Karl by texting +1 (844) 619-7958 . There’s no separate app or website – just text to start a conversation. The first ten messages are free, after which Karl charges 10 per month to continue (and to help cover Karl's dining habits).

On the backend, we primarily use 4o (OpenAI) to handle message flow and identify important memories. All the code for LLM calls, context management, and tool use is custom-built, as we found frameworks like Langchain to be too much overhead.

Moving forward, we plan to run a fine-tuned 4o-mini model and experiment with other providers. Texting is powered by Twilio (and FYI – getting a non-sandbox phone number is quite a process), and we use Postgres (via Supabase) to store conversations and context. The entire service runs on Render.

We’re also working on new features like proactive check-ins and smarter memory handling.

Karl is currently in early alpha. We'd love feedback from the HN community at hello@heykarl.xyz. Please say hi, and we hope you have some great conversations!