Design notes
Fit and alternatives
Why not just use a chatbot?
A chatbot can improvise a scene. A campaign also needs private preparation, rules that stay put, and a record that does not change when the context window does.
Why not use a general chatbot?
A normal conversation has no authoritative campaign record. Details can fall out of context or come back in a different form. Sylvia keeps the conversation separate from committed campaign state, so a confident sentence cannot quietly rewrite the campaign.
Why deterministic mechanics?
If the ruleset encodes a roll, resource, condition, or timing rule, the engine owns that result. Sylvia narrates what was committed. When a rule is not encoded, the decision remains honest GM judgement rather than pretending the engine calculated it.
Why a Campaign Plan?
Pure improvisation is easy to begin and hard to sustain. A Campaign Plan gives the GM acts, beats, private facts, and reveal conditions before play starts. Sylvia can revise that plan after the player changes direction; it is a guide, not a script.
Why not a closed roleplaying service?
A closed service decides which models, storage, rules, and product direction remain available. Sylvia GM is being built as free and open-source software with portable campaign data. You can use a hosted OpenAI-compatible provider or a local inference server that you already run.
Why is Builder separate?
Running a campaign and constructing its rules are different jobs. Sylvia needs bounded authority over live play. Builder needs room to make and validate rulesets, settings, and Campaign Plans without becoming a second writer in the GM conversation.