Inspiration
The text MUD is a dead genre — it died with dial-up. Kiroween's Resurrection track asked us to bring something dead back to life, so we resurrected the telnet-era MUD and rebuilt it for the age of agents.
What it does
You wake up in Yongning Prefecture as a 16-year-old outer disciple, at the very bottom of the cultivation ladder. There is no open world to grind and no quest marker to follow. There are only three places, three people, and your choices:
- The Sect Hall, where Sect Master Qingxu gives you the main quest and judges whether you are ready to advance.
- The Ghost Market, where the trader Yexiao will sell you anything — including a soul-lantern you may not survive paying for.
- The Nether Ferry, where the main quest ends, if you make it that far.
Each NPC is a LangGraph agent with its own memory and its own non-overlapping toolset. Qingxu only handles quests. Yaolao, the old alchemist, only answers from a strict RAG knowledge base of pill recipes and cultivation manuals — if it is not in the archive, he says so instead of inventing it. Yexiao only trades. Ask the wrong NPC for the wrong thing and they will send you to the right one, in character.
High-stakes actions — gambling your life for a treasure, brewing an unknown pill, crossing the ferry — pause for human confirmation via LangGraph interrupt. Cancel, and nothing changes. Confirm, and the trade is idempotent: the same request can never charge you twice.
How we built it
Built with Next.js + TypeScript + LangGraph.js, with a terminal-style UI, a typewriter narrative, and a deterministic rules engine for HP, spirit, energy, cultivation, and realms — from Qi Refining to Foundation Establishment. The rules are pure functions, covered by unit and property-based tests (38 tests passing), so the numbers never lie even when the NPCs do.
Kiro shaped the whole build: spec-driven development in .kiro/specs/, steering docs for the world bible and agent-friendly principles, hooks that run lint and game-rule tests on save, Kiro Crew for planner / coder / tester, and MCP for repository work.
Challenges we ran into
The trickiest bug was a silent one: tool results were lost because the reducer key the tool node wrote to didn't match the one the graph read. We caught it with an explicit tool round-trip test. We also had to design RAG without vector search — our model provider has no public embeddings API — so the alchemist uses strict keyword matching and says "no such record" instead of hallucinating.
What we learned
A supervisor agent must never hold its workers' tools, different workers' toolsets must never overlap, and every side effect belongs after an interrupt or behind an idempotency key.
What's next
More side quests, more realms beyond Foundation Establishment, and a second playable disciple.
Try it: https://youming-mud.vercel.app/ Code: https://github.com/sakuiy/youming-mud
Built With
- kiro
- langgraph.js
- next.js
- typescript
