foldyard

A guide to working inside a foldyard development box, an isolated virtual machine that runs a project from a mounted repository.

In plain words
What is it for?
Checking the current foldyard mode, verifying the host-box boundary, using worktrees, handling credentials and network access, and diagnosing why configuration or compose changes did not apply.
Why use it?
It explains the boundary between the host computer and the box, including limits around pushing code, credentials, network access, and configuration changes.

Skill for Claude CodeCodex

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.

agentmods
npx agentmods add skills/daaain/claude-code-log/foldyard
Any agent
npx skills add daaain/claude-code-log --skill foldyard
Clone the repo
git clone --depth 1 https://github.com/daaain/claude-code-log

Made for: Claude Code, Codex.

Per session 100 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 1,253 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 0 findings. Scan, not verified.
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 $0.00100 $0.01253
Opus 5 $0.00050 $0.00626
Sonnet 5 $0.00020 $0.00251
Haiku 4.5 $0.00010 $0.00125

Measured 2d ago against content hash 0f662918c6ad, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

foldyard 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 2d 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.

.claude/skills/foldyard/SKILL.md · 85 lines

How it starts

The opening of the file, as written. The whole thing — 85 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Working in (and on) a foldyard dev box

Foldyard runs this project inside a rootless VM that mounts only this repo. You are almost certainly in the box — a container in that VM — and the person you're working with is on the host (their Mac). That split explains nearly everything below.

Check where you are: fy mode prints the posture and says which side it's reading from. fy verify proves the boundary (it exits non-zero if any of it is false).

The four facts that will save you the most time

  1. You cannot push. No credential to the git remote reaches the box, by design. Read and commit locally; the human pushes. Don't try to work around it — there is nothing to find.
  2. You hold no real secrets, and can't grant yourself any. Posture state lives in the host's home, outside the mount. fy mode shows posture anywhere; setting it is host-only.
  3. Your egress goes through the host's proxy and may be allow-listed or walled. A blocked host is a decision, not a bug — ask; don't route around it.
  4. The engine socket you have is real and bounded to this VM. docker/podman commands work and act on the live dev stack — including anything a test suite's mocks let slip.

Ask the tool, don't guess

Foldyard is introspectable, and its own output is always current — prefer it over any summary (including this one):

question command
what can this environment do right now? fy mode (posture), fy state (desired vs observed)
what's broken / missing? fy doctor — one line per check, each with its fix
is the isolation intact? fy verify
what does this verb do? fy --help, fy <verb> --help
the manual, offline, by topic fy docs — then fy docs <topic>
what does the config let the host do? fy config widenings

fy docs serves this install's documentation, so it can't drift from the code you're running. Start with fy docs quickstart, fy docs modes, fy docs networking, fy docs security; the ADRs (fy docs adr-0001 …) carry the reasoning behind each design decision.

Read the full file on GitHub · 85 lines

Files

What ships with it

3 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. 2d ago First seen · 85 lines · 100 tokens per session scan A 0f662918c6ad

Subscribe to this mod's changes

foldyard is a skill published in the GitHub repository daaain/claude-code-log (1,201 stars, last pushed 2d ago), licensed MIT. It adds 100 tokens to every session and 1,253 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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