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 Marcel-Bich/marcel-bich-claude-marketplace --skill sandboxgit clone --depth 1 https://github.com/Marcel-Bich/marcel-bich-claude-marketplaceWrote 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/marcel-bich/marcel-bich-claude-marketplace/sandbox)<a href="https://agentmods.dev/skills/marcel-bich/marcel-bich-claude-marketplace/sandbox"><img src="https://agentmods.dev/badge/skills/marcel-bich/marcel-bich-claude-marketplace/sandbox/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/marcel-bich/marcel-bich-claude-marketplace/sandbox"><img src="https://agentmods.dev/badge/skills/marcel-bich/marcel-bich-claude-marketplace/sandbox.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 | $0.00189 | $0.01570 |
| Opus 5 | $0.00095 | $0.00785 |
| Sonnet 5 | $0.00038 | $0.00314 |
| Haiku 4.5 | $0.00019 | $0.00157 |
Grade A, and why
sandbox 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 12d 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 — 113 lines — stays where its author put it; the contents beside it link to each section on GitHub.
sandbox - writing pre-work for clarify items
Clarify items often hang on a knowledge gap that is NOT a product decision: a missing
measurement, a mockup, or a proof that something is feasible. The plan / clarify role
(role-plan) must not touch production code and must not commit. The sandbox gives it a place
to do writing pre-work OFF to the side - no production code, no git, no interference with the
task / build agent - so the clarify question can be answered with evidence instead of guesswork.
Two folders
.credo/sandbox-tmp/= UNVERSIONED work in progress. One folder per item:.credo/sandbox-tmp/<id>-<slug>/with aREADME.md. This is where pre-work is built..credo/sandbox/= the PROMOTION TARGET for accepted, version-worthy artifacts. It follows the credo folder-versioning policy: in an untracked repo it stays local; in a version-tracked repo (CREDO_VERSION_TRACKED=1) it IS versioned.docs/is NOT the promotion target. Extracting a promoted artifact intodocs/is a SEPARATE step the user prompts for explicitly; it never happens automatically.
exclude behavior (owned by credo-init)
The git-exclude is managed by credo-init in a single managed block in .git/info/exclude
(see the credo-init policy). Do not write that block from anywhere else.
- Default (untracked,
CREDO_VERSION_TRACKEDunset): all of.credo/**is excluded, so bothsandbox-tmp/andsandbox/stay local. Nothing extra is needed. - Tracked (
CREDO_VERSION_TRACKED=1):.credo/**is versioned EXCEPT the entries credo-init lists, which include.credo/sandbox-tmp/. So WIP stays local even in a tracked repo, while the promotedsandbox/is versioned.
The helper scripts/credo-sandbox-init.sh never writes the managed block; it only WARNS when
sandbox-tmp is not effectively git-excluded and points at /credo:setup to refresh it.
Reference search order
When resolving a sandbox reference for an item, ALWAYS look in this order:
.credo/sandbox/<name>/(promoted, accepted artifact) - use this if present..credo/sandbox-tmp/<name>/(WIP) - fall back to this.
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.
- 12d ago First seen · 113 lines · 189 tokens per session scan A 7dcbf72d32c7
sandbox is a skill published in the GitHub repository Marcel-Bich/marcel-bich-claude-marketplace (13 stars, last pushed 2d ago), licensed MIT. It adds 189 tokens to every session and 1,570 once invoked, about $0.0009 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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