AI Engineer — LLM Systems & Model Training

About the role

You own the brain behind every character. You run two tracks in parallel: the LLM system that makes conversations feel consistent, personal and alive today, and our own models trained on data you source and shape. Each feeds the other — production conversations become training data, and trained models replace prompts where they win on quality or cost. This is the first dedicated hire on the model layer; the architecture is yours to define.

Key responsibilities

• Architect a modular system-prompt framework — character identity, voice and style guides, world rules and safety layers composed per character and per context, versioned and testable.
• Build long-term memory — what to remember, summarization, retrieval (RAG / vector DB), user-profile extraction, recall at the right moment, forgetting and correction.
• Own response management — persona consistency, tone and length control, emotional-context handling, anti-repetition, multi-turn coherence, guardrails and refusals that stay in character.
• Select and orchestrate models — frontier APIs and open-weight bases chosen on quality, license, size, language coverage and serving cost; routing, fallback, streaming, latency and cost per conversation.
• Lead the training-data pipeline — sourcing, consent, cleaning, de-duplication, PII removal, quality filtering, labelling and dataset versioning, including turning live conversations into training data.
• Generate and curate synthetic dialogue data; write annotation guidelines and manage labelling vendors.
• Train our own models — continued pre-training, SFT, LoRA and preference tuning (DPO / RLHF) for character- and domain-specialized models.
• Distil, quantize and deploy on GPU inference stacks (e.g. vLLM, TensorRT-LLM); own the compute budget.
• Build evaluation across both tracks — golden sets, LLM-as-judge, persona-drift and safety red-teaming, A/B tests tied to retention and engagement — so prompt and model versions compete on the same metrics.
• Ship in English, Cantonese (including colloquial written Cantonese) and Mandarin.

About you

• 4+ years in ML or software engineering, with 1+ years shipping LLM products to real users.
• Deep, hands-on prompt engineering — system-prompt design, few-shot, structured output, tool calling, prompt testing.
• You have built memory or RAG systems in production.
• You have fine-tuned open-weight LLMs (DeepSeek, Qwen, Llama, Mistral, Gemma or similar) and built the dataset yourself.
• Strong Python and PyTorch; comfortable with Hugging Face, distributed training and cloud GPUs.
• Experimentation rigor — you can tell us about an eval or test that failed and what you changed.
• Startup mindset — you ship fast, own outcomes and work directly with the founders.
• English and Chinese required; Japanese is a strong plus.

About us

We are a funding-backed team working at the frontier of generative AI, building a next-generation AI social gaming platform — where AI-driven characters, stories, and interactive experiences bring people together in entirely new ways. Our characters hold long, personal, multi-session conversations with every player. You will work directly with the founding team and see your work live with real users.