by V1kingLightning | 2026-03-11 17:09:53+00:00
Show HN: I built an AI agent platform where your companion learns who you are across every session
nexushubadventure.com — solo project, 3 months, vanilla JS + Firebase + Anthropic API

The pitch
Most AI chat tools reset every session. You re-explain yourself every time. I wanted the opposite: an AI companion that remembers you, watches how you engage, and quietly builds a model of who you are — automatically, across every session.
That's Nexus Hub Adventure. It's part AI agent console, part interactive storytelling platform, part TTRPG hub. The core bet: persistent identity for your AI companion.

What I actually built

Hot-swappable AI cartridges — personality prompts you can swap mid-session (a warm companion, a Socratic philosopher, a gaming intelligence, a project strategist). Each one reads your player save before every reply.
Automatic preference inference — every 8 turns, the agent quietly analyzes the conversation and extracts facts about you ("prefers short answers", "building a web app called Nexus Hub"), then writes them to your Firestore profile. Next session, those facts are already in the system prompt.
Cartridge Workshop — build your own AI persona with a full system prompt, memory settings, and token budget. Share it with a 6-character code. Import anyone else's. The cartridge layer is fully user-extensible.
CARE economy — you earn CARE currency just by using the platform (2 CARE per agent reply, 10 per logged session). Record of engagement, not a grind.
Ember Egg dragon — earn 1,000 CARE, log 10 sessions, and your egg hatches. The dragon is the long-term retention mechanic. It's yours — that's the whole point. (Active dragon behavior is on the roadmap — right now it's a milestone, being honest.)
SAVE_CODEs — portable campaign codes that work across Claude, ChatGPT, Gemini. Your story isn't locked to one model.

The stack
Vanilla JS frontend · Firebase Auth + Firestore · Vercel · Anthropic API (Claude Haiku 4.5 default, Sonnet 4.6 available). No framework. No ORM. Firestore documents are the entire persistence layer — including the personality cartridges, which anyone can patch by editing JSON.

What I'm most proud of
The Watson personality prompt. I engineered it to ask one good question rather than offer ten weak suggestions — "sit with them before solving." It produces coaching-quality dialogue from Haiku that you wouldn't expect from the underlying model. Prompt architecture as product differentiation.

What I'd love feedback on

The inference approach: running a background Haiku call every 8 turns to extract player facts. Does this pattern have a name? I'm effectively building a conversational profile automatically — the agent learns you through the conversation.
The CARE economy: does 1,000 CARE for egg hatch feel like a meaningful milestone or arbitrary? Current earn rate makes it roughly 2-3 weeks of regular play.
The Cartridge Workshop: is user-buildable/shareable AI personas a compelling enough hook on its own? I'm wondering if that should be the lead feature instead of the dragon.

P.S. The pipeline playground already supports multi-step agentic workflows — chain your custom agents through automatic sequences. Still rough, but it works.

Try it
nexushubadventure.com — free, bring your own Anthropic or free Groq API key. Alpha, moving fast; some features are still could use the feedback to make this better.

Built by Casey Holler. Everything persists. Nothing is lost.