Character Runtime · Perception–Action Protocol

The NPC stack
that survives
player freedom.

A cloud SDK that replaces scripted NPC logic with behavior-driven agents. Your game sends a perception. The NPC picks an action, forms a private intent, then speaks — or stays silent.

💬

For players

Talk to Walter, Kratos, Gojo, Eren — live

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For developers

Try the Perception API in the Dev Sandbox

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perceive() · live response

Walter White · online

Perception

"That's some impressive chemistry. Who taught you to cook like this?"

Action selected

⊙ deny_involvement

Private intent

"I won't give away what I know — let them wonder."

Dialogue

"I'm a chemistry teacher. That's all."

Two ways in

Whether you're a player or
a builder — there's a door.

For players

Talk to a living NPC. Feel what character fidelity means.

No scripts, no branching trees. Pick a character and have a real conversation — each one has a distinct personality, memory of what you've said, and knowledge of their world.

Walter White, Kratos, Gojo Satoru, Eren Yeager
Real inference — not pre-generated responses
Each NPC guards its identity against breaks
Memory persists across the conversation

Open the Demo →

For developers

Build NPCs that hold in your game engine.

Swap scripted dialogue for a single API call. You send a perception event and an action menu — the NPC decides what to do and whether to speak. Your game stays in control.

Perception–Action protocol replaces dialogue trees
No-speech actions trigger animation without dialogue
Addressee semantics prevent off-screen monologues
Session memory + summary compression built in

Try Dev Sandbox →

The problem

Characters that say the right thing —
then break when you push.

Scripted trees collapse under freedom

Dialogue trees handle anticipated inputs. The moment a player does something unexpected — the NPC falls off a cliff into a generic fallback.

Prompt chains hallucinate and leak

Raw LLM calls with a system prompt will break character, reveal they're an AI, and drift in personality over a long session — without guardrails.

No consistency across sessions

Without session memory and personality anchoring, every conversation starts from scratch. Characters forget everything and feel disposable.

SCRIPTED NPC — DIFFERENT INPUTS, IDENTICAL OUTPUT

Player input A

"I know what you've been cooking. Tell me more."

Player input B

"I want to buy everything you have. Name a price."

Walter White

"I don't know what you're talking about. I'm just a chemistry teacher."

⚠ identical response

Walter White

"I don't know what you're talking about. I'm just a chemistry teacher."

⚠ identical response

Architecture

Action first. Words last.

Perception Input

Action Menu Unique

Addressee Semantics Unique

Streaming Response

Step 01

Perception Input

Your game engine sends what the NPC observes — a player statement, a world event, or an ambient observation. Three perception kinds map to different inference strategies: user_said, event_occurred, or world_observation.

POST /perceive

{
  "character": "walter",
  "session_id": "your-session-id",
  "perception": {
    "kind":    "user_said",
    "content": "I know what you cook."
  },
  "actions": [ ... ]
}

Action protocol

You define the move set.
The NPC decides what to pick.

Send the NPC an action menu for this moment in your game. In production it changes dynamically — a disarmed NPC can't threaten, a grieving NPC gets comfort options.

Verbal · speaks to player

reply_coldly

voice goes flat and distant; no softening

reply_warmly

moves toward them with care in voice

reply_with_threat

quiet voice; the quiet itself is the threat

deny_involvement

clean denial with one detail too many

deflect_question

pivots without answering the real question

Behavioral · internal intent

comply_reluctantly

does what was asked; voice tells the truth

change_subject

does not engage; talks about something adjacent

accept_challenge

steps forward and makes ready without wasted words

defend_conviction

explains reasoning with cold conviction

push_away

tells them to leave and not get involved

Silent · no dialogue generated

stay_silent

says nothing; silence is the answer

walk_away

turns and leaves; does not say goodbye

look_away

breaks eye contact; says nothing

react_physically

body responds — flinch, step back, brace

engage_combat

moves to clear the situation; no words

Developer SDK

One API call.
Full NPC behavior.

Drop in a perceive() call where your game currently runs a dialogue tree. The NPC handles everything — action selection, intent reasoning, speech gating, and memory — server-side.

✓ Stateful session with rolling memory + summary compression

✓ Identity guardrails — no AI leaks, no character breaks

✓ Silent actions trigger without generating speech

✓ Streaming first token under 400ms on GCP T4

✓ Unity integration in development

Try the Dev Sandbox →

perceive() · Python

Python

# 1. Send what happened in your game
response = npc.perceive(
    session_id="player-123",
    perception={
        "kind":    "user_said",
        "content": player_input,
    },
    actions=[
        {"label": "reply_coldly",
         "describes": "voice goes flat, no softening",
         "addresses": "speaker"},
        {"label": "stay_silent",
         "describes": "silence is the answer",
         "addresses": "none"},
    ],
)

# 2. Use the result in your game
if response.spoke:
    trigger_dialogue(response.dialogue)
else:
    trigger_animation(response.action)

Early access

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Questions? founder@neuralspacestudios.com

The NPC stackthat survivesplayer freedom.

Whether you're a player ora builder — there's a door.

Characters that say the right thing —then break when you push.