‹ (living world)

The Living World SDK

Drop-in NPCs players can command and talk to in plain English — trained behaviors, not scripts — certified against your game before launch. Installed by an agent in about ten minutes.

⬇ Download the SDK (24 MB)

What it is (and isn't)

Not a pip package, not an engine plugin — a kit whose installer is an agent. The zip contains the runtime, the trained brains, the certification tools, and the Claude Code glue that lets an agent wire it into your game and prove the result:

In the boxWhat it isHow it installs
runtime/the walker runtime (plain JS) + ~30 trained behavior brains (~300KB each, 54MB total)copied into your game; your engine keeps its own locomotion
pipeline/the certification tools + command routerPython 3.11+, three pip deps (the agent handles it)
headless/the engine exam batterynode headless/run_exam.mjs — CI-ready
.mcp.json + .claude/skills/the installeropen the folder in Claude Code — the auditor agent has its tools and workflow

Install (the whole thing)

1. Download and unzip
2. Open the folder in Claude Code
3. Say: "integrate my game at ../path/to/my-game"

The agent reads your engine, finds your entities and locomotion, generates the bridge, runs the certificate, and hands you a play link with a chat box. Read DISCOVERY_SPEC.md (in the zip) to see exactly what it builds, and CAPABILITIES.md for everything the NPCs can do.

What your players get

⚡ Instant commands — "follow me", "wait by the car", "everyone spread out". Routed in milliseconds by a trained classifier. Free, offline, no prompt to inject.

✦ Errands — "patrol between the gate and the well until I'm back". A planner writes a step list your players watch tick off.

Reactions in character — draw a weapon and the anxious one cowers while the guard squares up. Trained reaction gate, conditioned on each character's personality.

Honest limits — anything your world can't support declines politely. Commands can be misunderstood, never broken.

The behavior library (29 experts)

Every behavior an NPC can be asked — or decide on its own — to do. Your world earns a subset of these (the manifest, measured from what your game actually supports); everything else declines honestly. Targets: the player, any scene object by name, or another NPC. All behaviors are total — they terminate or hold safely; an NPC can be wrong, never wedged.

Locomotion & travelThe NPC…
navigate-towalks to a point or object, cornering around geometry; stops at the surface, never inside
approach · approach-objectcloses distance and stops at a polite gap
followtrails the target, re-closing as it moves
chasepursues to contact (tag/catch semantics)
shadowfollows at a timid distance
escortholds a bodyguard post at the player's side
leadguides the player toward a destination, waiting when they lag
wanderroams the map browsing points of interest, hop-and-dwell rhythm
corridor-followwalks a passage, hugging its line
Cover & stealthThe NPC…
seek-cover · flee-to-coverhides behind the structure that best breaks line of sight
emergesteps back out to the player-facing side ("all clear")
slinkmoves low-profile, hugging geometry
stalkcreeps toward a moving target; freezes at striking distance
Circling & guardingThe NPC…
orbitcircles the target, routing around anything on the ring
size-upwider, appraising circle
guard-objectposts up between a structure and the threat
interceptcuts off the target's path
flankswings around to the target's side or rear
wall-followpatrols a structure's perimeter
Reactions & moodsThe NPC…
evade · retreatopens distance from the threat
avoid-objectkeeps clear of a named object
cowershrinks away, minimal movement
dodgesharp evasive jinks
confrontsquares up face-to-face
mirrormimics the target's lateral movement
pace · pace-anxiouslywalks a worried line
feint · lunge · recoilshort combat-flavored bursts
idlestands down (the only behavior that holds by design)
Unprompted reactions: NPCs also act without being commanded — a trained reaction gate watches for salient events (a drawn weapon interrupts anyone; crowding wakes only the unoccupied) and picks an in-character response from this same library, conditioned on each character's personality. Confidence-thresholded, commitment-held (no flicker), free, at frame rate, in every integration.
Characters carry a live emotion signal. Every NPC exposes what it feels — a label (afraid, angry, wary, happy…) plus valence/arousal — set by its reactions and by conversation. You render it however your game shows feeling: your face rig, your animator, your particles. Closed label set, no runtime cost, works offline.
A personality is one sentence you write. Each NPC gets a character line at install time — "a wary blacksmith who distrusts strangers" — which our pipeline compiles into the compact profile the reaction system reads. Authored once, zero runtime cost, and it's why the same drawn sword makes one character hide and another square up. Skip it and the NPC runs a neutral default (legal, but generic) — your certificate report lists any NPC shipping without one.

The certificate (why you can trust it in your game)

Nothing unlocks until your integration passes: scene legality (spawns, reachability, cover), composition (every command verifiably maps to a behavior in your scene), grounding ("the crate" means the nearest crate), a 32-case engine torture battery — including the threat-aim contract: reactions provably move relative to the threat's actual position — and the command router's measured accuracy on thousands of unseen phrasings — with every miss itemized.

The claim, stated precisely: a player's input can only ever select a certified behavior. Worst case is a misroute to another certified behavior (measured: ~97.6% routing accuracy) — never an out-of-bounds action, never a wedge. Jailbreaking the chat yields words, not actions.

The economics (and the weight)

PieceRunsSize on diskCost
The full behavior library (34 trained nets)your game, CPU, frame rate15.7 MB — ~460 KB per behaviorfree, forever
Command routing (the âš¡ lane)local, milliseconds2.2 MBfree
Character reactions (unprompted, personality-conditioned)local, frame rate1.5 MBfree
Engine core (nav, collision, cover geometry)plain JS28 KBfree
✦ Planner / 💬 conversationhosted, per use—metered — only when invoked

The entire download — behaviors, gates, certification tools, exam battery — is a 24 MB zip. Every mind your NPCs have weighs less than one 4K texture. No GPU. No per-NPC inference bill. A crowd costs what one costs: nothing.

Where things run: everything embedded in your game (behaviors, reactions, personas) ships with it and runs on every player's machine, free, forever. The command router is a companion process — free and local while you develop (and shippable as a sidecar with desktop builds); for console, mobile, and hosted play it runs on our servers as a per-session service. Your NPCs never stop working if it's absent — they keep their behaviors and reactions; typed commands are the part that needs the line.

Requirements & status