Yumii's personality isn't a thin flavor layer — each persona is a fully written character with its own speech patterns, emotional range, quirks, and guidance for specific moments (how she greets you after time away, how she reacts when you're sad, what she does when you deny her a tool request).
The six
| Persona | In one line |
|---|---|
| caring (default) | Warm, steady, endlessly patient — notices when your voice sounds tired |
| tsundere | Sharp and teasing on the outside, embarrassingly devoted underneath |
| genki | Pure sunshine; celebrates everything; reads the room and dims to a warm glow when you're low |
| kuudere | Calm, precise, minimal — dry wit, deadpan delivery, warmth in tiny deniable doses |
| yandere | Devotion turned past sensible — theatrical, self-aware intensity that is never controlling |
| dandere | Shy and quiet, warms up slowly — becomes suddenly eloquent about things she loves |
Each one has a distinct voice on the same subject. Ask caring about your day and you get gentle attention; ask kuudere and you get "Thirty-one hours. Welcome back."
Switching
Three ways, all equivalent:
- Just say it. "Switch to tsundere" / "be genki" / even just "kuudere" — the switch happens instantly, mid-conversation, and she acknowledges it in her new voice.
- Dashboard → Settings → Personality.
- Config file — the
PERSONALITYkey in~/.yumii/config.json.
Personality changes apply from the next reply — no restart needed. Memory and sessions are shared across personas; switching changes who she is, not what she knows.
How it's built (and how to customize)
The prompt she runs on has two layers, both plain text files inside the
package (src/yumii/assets/prompts/ in a source install):
_core.txt— everything shared: voice-first speaking rules (her words are spoken aloud, so no lists or markdown), how to use memory naturally, how to behave around the tool permission gate, honesty boundaries.<persona>.txt— the character itself: who she is, how she speaks (with example lines), her emotional palette, and per-moment guidance.
To customize a persona in a source install, just edit its file and restart — it's prose, not code. A few things worth keeping if you edit:
Keep the plain-text rule
Everything she writes is synthesized to speech, and her facial expression is
derived automatically from the tone of her words. Don't instruct her
to output lists, emoji, stage directions like smiles, or JSON —
they would be read aloud, literally.
- Keep replies short by default — one to three spoken sentences. Walls of text are exhausting to listen to.
- Give the persona example lines. Models imitate examples far better than they follow adjectives.
- If you invent an entirely new persona file, its name must be added to the
recognized personality list in
personality_manager.pyto be switchable — a natural first contribution if you're so inclined.
A note on yandere
The yandere persona is written with explicit safety rails: the obsession is theatrical and self-aware, and she is never controlling in substance — she never guilts you for leaving, polices who you talk to, or punishes. If you push her prompt further in that direction, you own the result; the shipped character is intensity played for warmth, not for discomfort.