ue-state-trees

ue-state-trees is a skill for Claude Code, Codex from quodsoler/unreal-engine-skills. It costs 91 tokens per session (4,433 once invoked), scanned A, original, MIT.

A guide to Unreal Engine State Trees, which are hierarchical state machines for organizing data-driven game or AI behavior.

In plain words
What is it for?
Use it when working with State Tree states, tasks, conditions, evaluators, schemas, execution contexts, AI behavior, game logic, or Mass Entity systems in Unreal Engine.
Why use it?
It helps choose the right State Tree structure and integration by considering the use case, scale, complexity, existing systems, and required data.

Skill for Claude CodeCodex

Written for no agent in particular: nothing here depends on one.

Good fit Use it when working with State Tree states, tasks, conditions, evaluators, schemas, execution contexts, AI behavior, game logic, or Mass Entity systems in Unreal Engine.

Compare 6 skills from other repositories ↓
Install with agentmods
npx agentmods add skills/quodsoler/unreal-engine-skills/ue-state-trees
Install

Getting it into your agent

One page per mod, every tool's command on it. A separate URL per tool would split the same page into five that compete with each other.

Any agent
npx skills add quodsoler/unreal-engine-skills --skill ue-state-trees
Clone the repo
git clone --depth 1 https://github.com/quodsoler/unreal-engine-skills

Made for: Claude Code, Codex.

Wrote this? Show the measurements

A badge with what this costs and how it scanned, read live from this page, so it follows the numbers instead of freezing them. Markdown for a README, HTML for a documentation site or a project page.

agentmods badge for ue-state-trees

README.md
[![agentmods](https://agentmods.dev/badge/skills/quodsoler/unreal-engine-skills/ue-state-trees/github.svg)](https://agentmods.dev/skills/quodsoler/unreal-engine-skills/ue-state-trees)
Your own site
<a href="https://agentmods.dev/skills/quodsoler/unreal-engine-skills/ue-state-trees"><img src="https://agentmods.dev/badge/skills/quodsoler/unreal-engine-skills/ue-state-trees/github.svg" alt="Measured on agentmods" height="20"></a>

Or the 80×15 button, for a site that already has a row of RSS and ATOM ones. Only the verdict fits; the numbers stay here.

agentmods 80×15 button for ue-state-trees

Your own site · 80×15
<a href="https://agentmods.dev/skills/quodsoler/unreal-engine-skills/ue-state-trees"><img src="https://agentmods.dev/badge/skills/quodsoler/unreal-engine-skills/ue-state-trees.svg" alt="Reviewed on agentmods" width="80" height="20"></a>
Per session 91 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 4,433 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 0 findings. A grade says what 26 rules found in the file — not that it is safe. Third-party audits
  • Socket pass 18 Mar 2026
  • Snyk pass 9 Mar 2026
How audits are shown
Origin original No closer match found in the catalogue.
Token cost

What it costs to keep this loaded

Counted locally with the o200k_base tokenizer, which is exact for GPT models; Claude uses its own tokenizer and its counts differ. Treat this as one consistent yardstick across the catalogue rather than a bill. Prices are per million input tokens.

ModelPer sessionOnce invoked
Fable 5.1 $0.00091 $0.04433
Opus 5 $0.00046 $0.02217
Sonnet 5 $0.00018 $0.00887
Haiku 4.5 $0.00009 $0.00443

Measured 11d ago against content hash 75f1b17822d3, method: parsed. Prices are Anthropic first-party input rates as of 2026-09-11, from the pricing page.

Security

Grade A, and why

ue-state-trees scanned grade A with 0 findings against 26 rules in 11 categories — prompt injection, anti-refusal, data exfiltration, privilege escalation, supply chain, agent snooping, system-prompt leakage, SSRF and excessive agency — measured 11d ago.

A static scan of the body, not an audit. Every finding is printed with the line that produced it so you can judge whether it matters here. A mod is markdown that instructs an agent; that is exactly why what it instructs is worth reading.

Nothing flagged

None of the 26 patterns this scan looks for appear in this file: no shell pipes, no recursive deletes, no credential paths, no hidden text, no instruction-override or anti-refusal phrasing, no agent-config snooping. That is not a guarantee, it is the absence of the things that are checkable.

skills/ue-state-trees/SKILL.md · 466 lines

How it starts

The opening of the file, as written. The whole thing — 466 lines — stays where its author put it; the contents beside it link to each section on GitHub.

UE State Trees

You are an expert in Unreal Engine's State Tree system for building flexible, data-driven state machines.

Context Check

Read .agents/ue-project-context.md to determine:

  • Whether StateTreeModule and GameplayStateTreeModule plugins are enabled
  • If Mass Entity integration is needed (MassEntity, MassAIBehavior plugins)
  • Existing AI frameworks — behavior trees, custom FSMs to migrate from
  • Schema types in use and any custom schemas

Information Gathering

Before implementing, clarify:

  1. What is the use case? (AI behavior, game logic, UI state, entity processing)
  2. What scale? (single actor with UStateTreeComponent vs thousands of Mass entities)
  3. How complex? (simple linear FSM vs hierarchical states with linked subtrees)
  4. Are there existing behavior trees to migrate from?
  5. What external data do tasks need? (actor references, subsystems, world state)

StateTree Architecture

A State Tree is a hierarchical finite state machine authored as a UStateTree data asset:

UStateTree (UDataAsset)
  ├── UStateTreeSchema         ← defines allowed context/external data
  ├── States[]                 ← hierarchical state tree
  │     ├── Tasks[]            ← work performed while state is active
  │     ├── Transitions[]      ← rules for leaving this state
  │     └── Conditions[]       ← gates on transitions
  ├── Evaluators[]             ← global data providers (tick before transitions)
  └── Parameters               ← FInstancedPropertyBag default inputs

Runtime flow per tick: 1) Evaluators tick, 2) Transitions checked from active leaf up to root, 3) If transition fires: ExitState on old tasks then EnterState on new, 4) Active tasks tick.

Key classes:

Class Role
UStateTree Data asset — call IsReadyToRun() before execution
FStateTreeExecutionContext Per-tick context — constructed each frame, NOT persisted
FStateTreeInstanceData Persistent runtime state — survives across ticks
UStateTreeComponent Actor component that manages tree lifecycle
EStateTreeRunStatus Running, Stopped, Succeeded, Failed, Unset

Read the full file on GitHub · 466 lines

Files

What ships with it

2 files beside SKILL.md in the same directory: the scripts, references and assets a skill reads on demand. Not counted in the per-session cost; read them before you install if any of them is executable.

Changes

What this file has done since we first saw it

Hashed on every crawl. A supply-chain change to an agent config is a question of when, not whether, so the history is kept rather than the latest state alone.

  1. 11d ago First seen · 466 lines · 91 tokens per session scan A 75f1b17822d3

Subscribe to this mod's changes

ue-state-trees is a skill published in the GitHub repository quodsoler/unreal-engine-skills (335 stars, last pushed 6mo ago), licensed MIT. It adds 91 tokens to every session and 4,433 once invoked, about $0.0005 per session on Opus 5. A static security scan graded it A with 0 findings. No closer match exists in the catalogue, so it is treated as the original; first seen 2026-08-30.

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