kastell-careful

kastell-careful is a skill for Claude Code from kastelldev/kastell. It costs 26 tokens per session (640 once invoked), scanned A, original, Apache-2.0.

A safety guard for Kastell commands that delete or restore servers. It requires explicit confirmation before those operations can proceed.

In plain words
What is it for?
Use it during Kastell sessions that may run destroy, server-delete, or restore commands.
Why use it?
It reduces the chance of accidentally destroying or restoring the wrong server or losing work.

Skill for Claude Code

Written for Claude Code: disable-model-invocation in frontmatter.

Part of the kastell plugin — 4 skills, 1 agent, 4 hooks, 1 MCP server shipped together

Good fit Use it during Kastell sessions that may run destroy, server-delete, or restore commands.

Compare 6 skills from other repositories ↓
Install with agentmods
npx agentmods add skills/kastelldev/kastell/kastell-careful
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.

Any agent
npx skills add kastelldev/kastell --skill kastell-careful
Clone the repo
git clone --depth 1 https://github.com/kastelldev/kastell

Made for: Claude Code.

Or install kastell, the plugin that ships this one along with the rest of its 4 skills, 1 agent, 4 hooks, 1 MCP server.

Wrote 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.

agentmods badge for kastell-careful

README.md
[![agentmods](https://agentmods.dev/badge/skills/kastelldev/kastell/kastell-careful/github.svg)](https://agentmods.dev/skills/kastelldev/kastell/kastell-careful)
Your own site
<a href="https://agentmods.dev/skills/kastelldev/kastell/kastell-careful"><img src="https://agentmods.dev/badge/skills/kastelldev/kastell/kastell-careful/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.

agentmods 80×15 button for kastell-careful

Your own site · 80×15
<a href="https://agentmods.dev/skills/kastelldev/kastell/kastell-careful"><img src="https://agentmods.dev/badge/skills/kastelldev/kastell/kastell-careful.svg" alt="Reviewed on agentmods" width="80" height="20"></a>
Per session 26 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 640 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 0 findings. A grade says what 26 rules found in the file — not that it is safe. Third-party audits
  • NVIDIA SkillSpector warn 7 Sept 2026
SkillSpector: 1 finding, up to medium

These are SkillSpector’s own severities. On a checked sample its high-severity flags on skills were ~96% false positives — a documented command, a public API, a “never do X” rule — so we show them as a caution to read, not a verdict. Why →

  • medium Excessive Agency · line 46
    Skill enables autonomous high-impact decisions without human-in-the-loop verification. Critical operations (destructive commands, financial transactions, data deletion) should require explicit user confirmation.
    Fix: Add human-in-the-loop confirmation for destructive, irreversible, or high-impact operations. Never auto-execute commands that modify files, send data, or alter system state.
How audits are shown
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 5.1 $0.00026 $0.00640
Opus 5.5 $0.00010 $0.00256
Sonnet 5.5 $0.00005 $0.00128
Haiku 4.5 $0.00003 $0.00064

Measured 2mo ago against content hash b075db808b60, method: parsed. Prices are Anthropic first-party input rates as of 2026-10-07, from the pricing page.

Security

Grade A, and why

kastell-careful 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.

kastell-plugin/skills/kastell-careful/SKILL.md · 65 lines

What it actually says

Kastell Careful

Purpose

Safety guard that intercepts kastell destroy and kastell restore commands. Requires explicit confirmation before any destructive operation proceeds.

When to Use

Invoke /kastell:careful before a session that involves server destruction or restoration. The skill-scoped prompt hook activates and monitors all Bash commands until the skill session ends.

Current State

Changed files: !git diff --name-only 2>/dev/null || echo "Not a git repo" Uncommitted: !git status --short 2>/dev/null || echo "Not a git repo"

How It Works

Three layers of protection work together:

Layer 1: Plugin hooks.json — Always active (plugin scope). Silently blocks kastell destroy and kastell server-delete via command hook (regex match, exit 2). No confirmation offered — hard block.

Layer 2: This skill's prompt hook — Active only during /kastell:careful session. Uses an LLM to detect destroy AND restore intent in any Bash command. Returns {"decision": "block"} with a reason message explaining the block. Covers restore which Layer 1 does NOT cover.

Layer 3: KASTELL_SAFE_MODE — Runtime guard embedded in CLI code itself (isSafeMode()). Last line of defense at the application layer.

The three layers are complementary: Layer 1 stops silent automation, Layer 2 provides in-session confirmation UX with semantic understanding, Layer 3 enforces safe mode at execution time.

Scope

Only kastell destroy and kastell restore are intercepted. Other commands (including kastell audit, kastell lock, kastell status) pass through without delay.

Confirmation Flow

When a destructive command is detected:

  1. Hook blocks execution
  2. Reason message shown to user explaining what was detected
  3. User must explicitly confirm to proceed (re-invoke with approval)
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. 2mo ago First seen · 65 lines · 26 tokens per session scan A b075db808b60

Subscribe to this mod's changes

kastell-careful is a skill published in the GitHub repository kastelldev/kastell (59 stars, last pushed 1mo ago), licensed Apache-2.0. It adds 26 tokens to every session and 640 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.

Related

kastell-careful compared with skills from other repositories

kastell-careful next to 6 skills from other repositories
ModTypeStarsLast pushLicenceScanTokensWorks with
kastell-carefulkastelldev/kastellSkill591mo agoApache-2.0A26Claude Code
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coolifyericrisco/rsc-harnessSkill5032d agoMITB100Claude Code, Codex
harbor-daytonaav/harborSkill3.3k6d agoApache-2.0A67Claude Code
boost-modulesav/harborSkill3.3k6d agoApache-2.0A0Claude Code, Codex
dockerericrisco/rsc-harnessSkill5032d agoMITB86Claude Code, Codex
agentbox-setupmadarco/agentboxSkill5701mo agoMITB38Claude Code