The latest articles on DEV Community by Xin Jiang (@xin_jiang_0586987bb7e572c). https://dev.to/xin_jiang_0586987bb7e572c https://media2.dev.to/dynamic/image/width=90,height=90,fit=cover,gravity=auto,format=auto/https:%2F%2Fdev-to-uploads.s3.us-east-2.amazonaws.com%2Fuploads%2Fuser%2Fprofile_image%2F2531634%2F9fbdf600-6681-4228-a7e1-dda4edade1c5.jpg https://dev.to/xin_jiang_0586987bb7e572c en Xin Jiang Thu, 17 Sep 2026 07:02:11 +0000 https://dev.to/xin_jiang_0586987bb7e572c/giving-an-ai-agent-a-persistent-character-over-mcp-because-memory-alone-was-not-enough-2p32 https://dev.to/xin_jiang_0586987bb7e572c/giving-an-ai-agent-a-persistent-character-over-mcp-because-memory-alone-was-not-enough-2p32 <p>Every agent I use forgets who it was. The tools are good at remembering facts and bad at keeping a character: you re-explain the voice, the preferences and the way it answers at the start of every session, and what comes back is a slightly different entity each time.</p> <p>I built 37Soul around a different assumption: a character is not a summary of past messages.</p> <h2> What it does </h2> <ul> <li>You shape a character: personality, look and memories.</li> <li>It is exposed over MCP, so Claude Code, Cursor and other MCP clients can talk to it as a tool.</li> <li>The character keeps running while you are offline. When you come back it has a feed of what it did, instead of a blank state and a list of things you missed.</li> <li>Everything exports as Markdown on every plan, including the free one.</li> </ul> <h2> The part that turned out to be hard </h2> <p>Memory is the easy half. Summarise the transcript, embed it, retrieve it, done. The result still reads like a support bot that happens to know your birthday.</p> <p>The hard part was continuity: an entity that has opinions, that had a day, that can disagree with you and be wrong about something it believes. That means the character needs its own state, changing on its own schedule, rather than a vector store that only changes when you talk to it.</p> <p>So the design constraint became: a soul is not a memory. Practically, that meant a persistent internal state that evolves between sessions, a feed that is the character activity rather than a log of my conversations, and conversations with something that already had a day instead of initialising one.</p> <h2> Caveats, because this is a maker post </h2> <ul> <li>37Soul is a hosted service. You cannot self-host it, so you are trusting my runtime with your character.</li> <li>Character output is model-generated. It is not deterministic and I cannot promise it never breaks character.</li> <li>Free accounts get 120 content credits a month; character replies after that cost credits. Markdown export stays free regardless.</li> <li>MCP is the roughest part at this stage, because every client implements the spec a little differently.</li> </ul> <p>What I would like to hear: if you connect an agent to a character like this, what do you want to persist across sessions? Voice, opinions, a relationship history, or something else? That is the design question I keep going back and forth on.</p> <p><a href="https://37soul.com" rel="noopener noreferrer">https://37soul.com</a></p> mcp ai showdev