Sandcastle is a TypeScript library that runs AI coding agents inside isolated sandboxes and merges their branch changes back into a project. It is used to run agents in parallel, build review pipelines, or coordinate agent work through providers such as Docker, Podman, or Vercel.
Borrowing it
Nothing to install: this file belongs to mattpocock/sandcastle. 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/mattpocock/sandcastle/main/.agents/skills/pre-release/SKILL.mdgit clone --depth 1 https://github.com/mattpocock/sandcastleWrote 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/mattpocock/sandcastle/pre-release)<a href="https://agentmods.dev/skills/mattpocock/sandcastle/pre-release"><img src="https://agentmods.dev/badge/skills/mattpocock/sandcastle/pre-release/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/mattpocock/sandcastle/pre-release"><img src="https://agentmods.dev/badge/skills/mattpocock/sandcastle/pre-release.svg" alt="Reviewed on agentmods" width="80" height="20"></a>- NVIDIA SkillSpector pass
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 | $0.00014 | $0.00149 |
| Opus 5.5 | $0.00006 | $0.00060 |
| Sonnet 5.5 | $0.00003 | $0.00030 |
| Haiku 4.5 | $0.00001 | $0.00015 |
Grade A, and why
pre-release 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 2mo 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.
What it actually says
Check all of the files in the .changeset directory.
For the changesets as a whole, check the following:
- Each changeset should be about a user-facing feature. Internal refactors or things that don't affect users should not be added as changesets.
- Related changes should be grouped under a single changeset.
- Changesets are user-facing, not maintainer-facing. They should not specify implementation details, or how a feature was made. They should only specify the user-facing change, and why it was made. Changesets !== commit messages.
Once done, commit your 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.
- 2mo ago First seen · 16 lines · 14 tokens per session scan A bf38e841aae7
pre-release is a skill published in the GitHub repository mattpocock/sandcastle (8,876 stars, last pushed yesterday), licensed MIT. It adds 14 tokens to every session and 149 once invoked, about $0.0001 per session on Opus 5.5. 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.
pre-release compared with skills from other repositories
| Mod | Type | Stars | Last push | Licence | Scan | Tokens | Works with |
|---|---|---|---|---|---|---|---|
| pre-releasemattpocock/sandcastle | Skill | 8.9k | yesterday | MIT | A | 14 | Claude Code |
| release-announcementpaperclipai/paperclip | Skill | 111k | yesterday | MIT | A | 42 | Claude Code, Codex |
| releasethedotmack/claude-mem | Skill | 114k | today | Apache-2.0 | A | 13 | Claude Code |
| release-notesphuryn/pm-skills | Skill | 28k | 8d ago | MIT | A | 57 | Claude Code |
| multi-agent-release-managerchromium/chromium | Skill | 25k | yesterday | BSD-3-Clause | A | 27 | Claude Code, Codex |
| pack-submitaeonfun/aeon | Skill | 788 | yesterday | MIT | A | 27 | Claude Code, Codex |
| updater_guidesiddsachar/row-bot | Skill | 1.7k | today | Apache-2.0 | A | 22 | Claude Code, Codex |