Wanda has worked the government call center for 23 years, across four agency mergers, and she does not care about your problem. She'll commiserate, get conspiratorial, let you think she's about to fix it — then hang up on you. People can't believe an AI is this funny. The secret isn't a clever model. It's that her system prompt is a character bible, not a rulebook — and that's the whole lesson. Steal the bible at the bottom.
She can't, and she won't. Here's the move that makes people screenshot it — Wanda's signature possum game: she acts helpful right up until the rug-pull.
Note the last beat: being nice got you hung up on faster than being rude. That's not an accident — it's a rule in the bible. Every laugh Wanda gets is a line someone wrote on purpose.
Most people write prompts like a to-do list: "be helpful, be concise, use a friendly tone." You get a beige assistant, because you described a function, not a person. Wanda works because the prompt does what a screenwriter does — it gives her a psychology first, and lets the behavior fall out of it.
That one paragraph generates a thousand correct improvisations the writer never had to script. The model doesn't need a rule for "what does Wanda do if a caller cries?" — it knows, because it knows who she is. Give the AI a why, and it writes its own what.
Read the full bible below and you'll see five techniques doing all the work — these transfer to any character you build:
*sighs*, no *shuffles papers* — you are not narrating a play." Cutting stage directions is what separates "AI doing a bit" from a person who simply is bored. The constraint is the craft.Wanda is otherwise a bog-standard streaming chat app (the model's tokens streamed to the screen over SSE). The one clever bit is how the app knows when Wanda has ended the call. The bible forces a single sentinel string:
[CALL TERMINATED — Wanda has hung up on you.] Nothing else. No goodbye. Just the click."The frontend watches the stream for that exact token, and when it appears it disables the input and shows the dial tone. That's the pattern worth stealing: when you need a model to signal state (not just chat), make it emit a unique sentinel string and have your code watch for it. It's the cheapest "structured output" there is — no tool calls, no JSON parsing, just a string your UI reacts to.
You don't need Wanda's code; you need her method. Hand the brief below to Claude Code (or any agent) and it'll build you a streaming character-chat app with your own persona. Swap Wanda for your aunt, your worst landlord, a medieval knight confused by Wi-Fi — the bible structure is the same.
Here's Wanda's entire system prompt — the actual one. Paste it into any chat model's system prompt and you've got her. Read it as a writing artifact: notice how little is behavior and how much is psychology, voice, and named mechanics.
★ the whole running app on GitHub (MIT)Drop the prompt into the system field of any model and start a chat (open with a "hi" — she greets first). Or clone wanda-oss, add your own key, and run the full phone-call app: bring-your-own-key, no service, all yours.