Record World

What it does

When your agent uses it

• Scores on itself
• Does something weird on the /sim page
• Eval-tidy / eval-pitch numbers move and you want to see why
• After touching brain/

Example prompts

• “does something weird”
• “record the sim”
• “video of the soccer”
• “/record-world”

Workflow steps

3 steps, taken from the first numbered list in SKILL.md.

1. 1events.txt — every brain state transition, fall (with the state,
2. 2sheet.png — Read it (it is an image). Header: scenario, seed,
3. 3world.mp4 — for the human. Attach it to the PR or SendUserFile it.

What it can do on your machine

Read from SKILL.md and the folder at commit bbf0326. It shows what the files ask for, not the result of running them.

• Tool permissions

  Pre-approves nothing: there is no allowed-tools line, so your agent's usual permission prompts apply.

  From allowed-tools in the SKILL.md frontmatter.

• Runs code

  Shell commands in SKILL.md call:

  • uv

  From the folder's file list and the shell code blocks in SKILL.md.

• Network

  No URLs in SKILL.md. Its commands use uv, which can reach the network depending on how they are called.

  From URLs in SKILL.md, links to its own repository left out.

• Credentials

  Names no API keys, tokens, secrets or passwords.

  From names ending in _API_KEY, _TOKEN, _SECRET, _KEY or _PASSWORD in SKILL.md.

Context cost

Record World loads about 1.2k tokens when it runs. Until then it costs about 217 tokens; SKILL.md has 517 words of instructions outside code blocks.

Always · name and description, kept in context so the agent knows when to use it

~217

When it runs · the whole SKILL.md, loaded when a task matches

~1.2k

Estimates: characters ÷ 4, the usual rule of thumb; real counts depend on the model's tokenizer. Scripts and assets cost tokens only if the agent reads them.

Safety

Automated static check — not a guarantee. Review scripts before installing. It scans the text of SKILL.md for risky patterns (piping downloads into a shell, reading credential files, hidden Unicode, destructive commands); files beside SKILL.md are not scanned.

SKILL.md

The full file from jonathanhawkins/microduck-lab at commit bbf0326, republished under its Apache-2.0 licence (© jonathanhawkins). 517 words, ~1,169 tokens.

name

record-world

description

Record a /sim WORLD scenario — the living room, the playroom tidy loop, a soccer pitch, any scenario JSON — to an mp4, a captioned contact sheet and an events log, headless and under a seed, then READ the sheet and the log to see what the ducks actually did. This is the debugging eye for the lab's world mode: the same brains, policies, team boards, tether and kickoff rule as duck-lab, minus the socket. Use when a duck falls, stalls, crowds, scores on itself or "does something weird" on the /sim page, when eval-tidy / eval-pitch numbers move and you want to see why, after touching brain/, world/, sensors/ or a scenario, and to capture a clip for a PR. Trigger on: "record the sim", "video of the soccer", "what is the duck doing in the living room", "watch the tidy loop", "show me the pitch", "why did it fall on the pitch", "record a scenario".

uv run record-world pitch-2v2 --seconds 30 --out /tmp/rw-pitch                          # a 2v2 match, whole-floor camera
uv run record-world living-room --seconds 20 --camera follow:d0 --out /tmp/rw-room     # follow one duck (wander brain)
uv run record-world playroom --seconds 120 --skip 60 --brain d0=tidy --out /tmp/rw-tidy # tidy loop, minute 2 only
uv run record-world scenarios/my-room.json --seed 3 --tether-ms 250 --out /tmp/rw-mine  # a user scenario, over a tether

© jonathanhawkins, Apache-2.0. Rendered from Markdown: HTML in the file is shown as text, images as links, and headings moved down two levels. Raw file

Files

Just SKILL.md in .claude/skills/record-world of jonathanhawkins/microduck-lab.

Open the folder on GitHubat commit bbf0326