Borrowing it
Nothing to install: this file belongs to joshsymonds/savecraft.gg. Take a copy, put it at the same path in your own repository, and replace the rules that are about this project with yours.
curl -O https://raw.githubusercontent.com/joshsymonds/savecraft.gg/main/.claude/skills/working-on-factorio/SKILL.mdgit clone --depth 1 https://github.com/joshsymonds/savecraft.ggWrote 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/joshsymonds/savecraft.gg/working-on-factorio)<a href="https://agentmods.dev/skills/joshsymonds/savecraft.gg/working-on-factorio"><img src="https://agentmods.dev/badge/skills/joshsymonds/savecraft.gg/working-on-factorio/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/joshsymonds/savecraft.gg/working-on-factorio"><img src="https://agentmods.dev/badge/skills/joshsymonds/savecraft.gg/working-on-factorio.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 | $0.00096 | $0.01684 |
| Opus 5 | $0.00048 | $0.00842 |
| Sonnet 5 | $0.00019 | $0.00337 |
| Haiku 4.5 | $0.00010 | $0.00168 |
Grade A, and why
working-on-factorio 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 9d 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 — 149 lines — stays where its author put it; the contents beside it link to each section on GitHub.
Working on the Factorio Plugin
Factorio uses a hybrid mod + daemon architecture — unique among Savecraft plugins. A Lua mod writes JSON to script-output/savecraft/, the daemon watches via fsnotify, and a thin WASM parser converts to ndjson. Design doc: plugins/factorio/README.md.
Architecture
plugins/factorio/
├── mod/ # Factorio Lua mod (control.lua, info.json)
├── parser/ # WASM pass-through parser (JSON → ndjson)
├── reference/ # WASM reference modules (recipe_lookup, ratio_calculator)
│ ├── data/ # Generated Go struct literals (*_gen.go)
│ └── views/ # Svelte reference views (ratio-calculator.svelte)
├── tools/
│ ├── datagen/ # Parses data-raw-dump.json → generated Go files
│ └── spritesheet/ # Packs icon PNGs into sprite sheet + manifest
├── sprites/ # Generated sprite sheets (items.png, fluids.png + JSON manifests)
├── plugin.toml # Plugin metadata, sources = ["wasm", "mod"]
└── Justfile
Verification
cd plugins/factorio
just test # Parser + reference module tests (32 tests)
just build # Build parser.wasm + reference.wasm
just datagen # Regenerate from data-raw-dump.json
just spritesheet # Regenerate sprite sheets from .reference/ PNGs
Full suite: just test-go (all Go) + just test-worker (all Worker) + just build-views (view compilation).
View changes require just build-views + committing views.gen.ts. See working-on-views skill for details. CI does not rebuild views — forgetting this ships stale HTML.
Key Conventions
Recipe Disambiguation
Never guess which recipe to use. When multiple non-recycling recipes produce the same item (e.g., solid-fuel from 3 oil sources), resolveRecipe() returns an error listing the options. The AI uses recipe_lookup (product query) to find options, picks contextually, and passes the explicit recipe name via the recipe or recipe_overrides parameters.
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.
- 9d ago First seen · 149 lines · 96 tokens per session scan A 9579f706f42e
working-on-factorio is a skill published in the GitHub repository joshsymonds/savecraft.gg (12 stars, last pushed 1mo ago), licensed Apache-2.0. It adds 96 tokens to every session and 1,684 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.
Other skills, from other repositories
gameobject-component-destroy
Destroy one or more Components from a target GameObject. Missing (null) components are skipped — they cannot be destroyed. Use 'gameobject-find' and 'gameobject-component-get' to identify the components first.
unity-version-split
Split a C# file into Unity 6.5+ and pre-Unity 6.5 variants. Use when a file needs different implementations for different Unity versions due to API changes (e.g., EntityId vs int, GetEntityId vs GetInstanceID).
unity-addressables
Manage Addressables groups, entries, profiles and content builds (com.unity.addressables, reflection-based).
playtest-report
Generates a structured playtest report template or analyzes existing playtest notes into a structured format. Use this to standardize playtest feedback collection and analysis.
motion
How an agent turns a character mesh into a usable animated FBX — and how to judge whether the result is shippable.
unity-manual-component
Manually add, configure, reorder, and copy components on GameObjects using Unity Editor UI. For one-off Inspector workflows that do not need REST automation.