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.
npx skills add LichAmnesia/unreal-engine-agent-skills --skill ue5-spawn-frame-and-inheritancegit clone --depth 1 https://github.com/LichAmnesia/unreal-engine-agent-skillsWrote 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.
[](https://agentmods.dev/skills/lichamnesia/unreal-engine-agent-skills/ue5-spawn-frame-and-inheritance)<a href="https://agentmods.dev/skills/lichamnesia/unreal-engine-agent-skills/ue5-spawn-frame-and-inheritance"><img src="https://agentmods.dev/badge/skills/lichamnesia/unreal-engine-agent-skills/ue5-spawn-frame-and-inheritance/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.
<a href="https://agentmods.dev/skills/lichamnesia/unreal-engine-agent-skills/ue5-spawn-frame-and-inheritance"><img src="https://agentmods.dev/badge/skills/lichamnesia/unreal-engine-agent-skills/ue5-spawn-frame-and-inheritance.svg" alt="Reviewed on agentmods" width="80" height="20"></a>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.
| Model | Per session | Once invoked |
|---|---|---|
| Fable 5.1 | $0.00112 | $0.01474 |
| Opus 5 | $0.00056 | $0.00737 |
| Sonnet 5 | $0.00022 | $0.00295 |
| Haiku 4.5 | $0.00011 | $0.00147 |
Grade A, and why
ue5-spawn-frame-and-inheritance 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.
How it starts
The opening of the file, as written. The whole thing — 109 lines — stays where its author put it; the contents beside it link to each section on GitHub.
Spawn Frame and Inheritance
Two actors, same code, different results — one is standing still and one is moving. That is the whole class of bug this skill covers, and it has two independent causes that produce similar symptoms:
Reference frame. A solution computed in the mover's frame, applied in world space, without the conversion. The error is a constant offset in the direction of motion, scaling linearly with speed. It has a signature that makes it easy to recognize once seen and nearly impossible to find by inspection: the bias is always in the same direction relative to travel, and it disappears when the mover stops.
Frame timing. A value read at the wrong point in the tick order, so it is one step stale or one step ahead. Error scales with speed and with step size, moves when frame rate changes, and vanishes under a debugger's slow stepping.
Both look like a bug in whatever consumes the value. Neither is.
Settle the frame contract first
- Name the frame every quantity is expressed in — world, actor-local, or component-local — and write it into the variable names or the comment where it is computed. Most inheritance bugs are two correct calculations joined without a conversion.
- Decide what a spawned object inherits, explicitly: the spawner's velocity, part of it,
or none. All three are legitimate designs. Silence is what produces the bug, because the
engine's default is "none" and the intuition of everyone reading the code is "some". See
references/inheritance-rules.md. - Decide when in the frame the read happens and confirm what has updated by then —
movement, animation, physics. A transform read before the mover's movement update is one
step behind. See
references/tick-order.md. - Convert once, at a named boundary. Solve in whichever frame is convenient, then convert at a single clearly marked place rather than mixing frames through the computation.
- Test at speed. A stationary test passes for every bug in this skill. Nothing here is detectable at rest.
What ships with it
4 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.
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.
- 11d ago First seen · 109 lines · 112 tokens per session scan A bef9c00a5b39
ue5-spawn-frame-and-inheritance is a skill published in the GitHub repository LichAmnesia/unreal-engine-agent-skills (5 stars, last pushed 26d ago), licensed MIT. It adds 112 tokens to every session and 1,474 once invoked, about $0.0006 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 2026-08-31.
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