toolhive-studio: Skill for Claude Code

.claude/skills/devcontainer-dev/SKILL.md

devcontainer-dev is a skill for Claude Code from stacklok/toolhive-studio. It costs 0 tokens per session (3,647 once invoked), scanned B, original, Apache-2.0.

A container-based development environment for ToolHive Studio, an Electron desktop application. It runs the application, display system, backend, database support, and Docker-in-Docker inside an isolated container accessed through a browser-based noVNC screen.

In plain words
What is it for?
Use it to run, test, or debug ToolHive Studio and the containers it starts, including from local worktrees or GitHub Codespaces.
Why use it?
It lets each worktree run in isolation, reducing conflicts with software installed on the host computer and making experiments safer.

Skill for Claude Code

Written for Claude Code: allowed-tools in frontmatter. Also seen: mentions CLAUDE.md.

This is stacklok/toolhive-studio's own configuration. It tells Claude Code how to work on toolhive-studio itself, so it is not a mod to install elsewhere. Copy it as a starting point and replace the rules that are about this project. Everything toolhive-studio configures →

Reuse

Borrowing it

Nothing to install: this file belongs to stacklok/toolhive-studio. Take a copy, put it at the same path in your own repository, and replace the rules that are about this project with yours.

Copy the file
curl -O https://raw.githubusercontent.com/stacklok/toolhive-studio/main/.claude/skills/devcontainer-dev/SKILL.md
Clone the repo
git clone --depth 1 https://github.com/stacklok/toolhive-studio

Made for: Claude Code.

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 devcontainer-dev

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

Your own site · 80×15
<a href="https://agentmods.dev/skills/stacklok/toolhive-studio/devcontainer-dev"><img src="https://agentmods.dev/badge/skills/stacklok/toolhive-studio/devcontainer-dev.svg" alt="Reviewed on agentmods" width="80" height="20"></a>
Per session 0 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 3,647 The whole file, excluding the scripts and references it only reads on demand.
Security scan B 1 finding. 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: 9 findings, up to high

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 →

  • high Privilege Escalation · line 44
    Potential security issue detected. Manual review is recommended.
    Fix: Review the flagged content for security risks. Ensure no credentials, secrets, or sensitive data are exposed.
  • high Tool Misuse · line 135
    Tool parameters are crafted to achieve unintended or unsafe behavior. Parameter abuse can bypass intended safety checks (e.g. shell=True, --force, dangerous glob patterns).
    Fix: Validate all tool parameters against an allowlist. Reject dangerous parameter values (shell=True, --force, -rf /) and use safe defaults.
  • high Tool Misuse · line 214
    Tool calls are chained to bypass individual safety checks or escalate capabilities beyond what any single tool call would allow.
    Fix: Limit tool chaining depth and validate the output of each tool before passing it to the next. Require explicit user approval for multi-step chains.
  • high Privilege Escalation · line 244
    Code accesses credential files (SSH keys, AWS credentials, etc.). This could indicate credential theft attempts.
    Fix: Remove references to credential paths. Use environment variables or secrets managers. For docs, use placeholder paths (e.g., /path/to/config). Never load .env or token files in production code paths.
  • medium Prompt Injection · line 30
    Large whitespace padding was detected (a block of blank lines or a long run of spaces). This can push injected instructions below or to the right of the visible area so a human reviewer never sees them while the agent still reads them. Manual review of the hidden content is recommended.
    Fix: Remove the large whitespace padding (blank-line blocks or long space runs) and review any content hidden below or to the right of it. Keep skill files compact and reviewable so no instructions can be
  • medium Rogue Agent · line 81
    Skill establishes unauthorized persistence across sessions via cron jobs, startup scripts, or state files. Session persistence allows an attacker to maintain access beyond the current interaction.
    Fix: Remove any persistence mechanisms (cron jobs, startup scripts, state files). Skills should not maintain state across sessions without explicit user consent.
  • medium Privilege Escalation · line 208
    Commands invoke sudo or root privileges. Verify this elevated access is necessary and justified.
    Fix: Avoid sudo/root unless strictly required. Prefer least-privilege patterns. If elevation is needed, document the justification and scope.
  • medium Privilege Escalation · line 214
    Commands invoke sudo or root privileges. Verify this elevated access is necessary and justified.
    Fix: Avoid sudo/root unless strictly required. Prefer least-privilege patterns. If elevation is needed, document the justification and scope.
  • medium MCP Rug Pull · line 258
    npx commands without a version suffix (e.g. @1.0.0) create a rug-pull risk if the upstream server is compromised and publishes a malicious update.
    Fix: Pin the version: npx @scope/[email protected]
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 $0.00000 $0.03647
Opus 5.5 $0.00000 $0.01459
Sonnet 5.5 $0.00000 $0.00729
Haiku 4.5 $0.00000 $0.00365

Measured 2mo ago against content hash 9e710a0f8730, method: parsed. Prices are Anthropic first-party input rates as of 2026-10-07, from the pricing page.

Security

Grade B, and why

devcontainer-dev scanned grade B with 1 finding 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.

Asks for rootmediumPrivilege escalation

A mod that escalates privileges can change anything on the machine, not only the project.

sudo modprobe iptable_nat iptable_filter ip_tables
.claude/skills/devcontainer-dev/SKILL.md · 277 lines

How it starts

The opening of the file, as written. The whole thing — 277 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Containerized Dev Environment

An isolated, cross-platform test environment for ToolHive Studio. The whole Electron app — including its backend thv binary and the MCP-server containers it spawns — runs inside a single devcontainer. You interact with the UI via a noVNC browser tab.

The entire stack (Node, Electron, display server, window manager, VNC server, Docker-in-Docker, DBus, keyring) lives in the container. Nothing is installed on the host. That's the whole point: every worktree can have its own container and its own experiments, with zero risk of contaminating the user's global installs.


Entry point

pnpm devContainer:dev

runs scripts/devcontainer-dev.sh on the host. The script is "smart":

  • If executed on the host: runs devcontainer up to build/start the container, then devcontainer exec to run the entrypoint inside it.
  • If executed inside a container (detected via /.dockerenv): skips the build step and just runs the entrypoint directly. This path is used by GitHub Codespaces.

The three scripts

Script Runs on Purpose
scripts/devcontainer-dev.sh host Picks a host port, kills stale processes, starts readiness poller, opens browser when ready, devcontainer execs the entrypoint.
scripts/devcontainer-entrypoint.sh in container Cleans stale X/VNC state, starts Xvfb, fluxbox, x11vnc, websockify/noVNC, dbus, gnome-keyring, then runs pnpm start.
scripts/devcontainer-post-start.sh in container postStartCommand in devcontainer.json. In Codespaces (detected via $CODESPACES) it nohup-launches the entrypoint in the background so the noVNC preview pane opens without user action.

Read the full file on GitHub · 277 lines

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 · 277 lines · 0 tokens per session scan B 9e710a0f8730

Subscribe to this mod's changes

devcontainer-dev is a skill published in the GitHub repository stacklok/toolhive-studio (173 stars, last pushed today), licensed Apache-2.0. It costs nothing until one of its globs matches a file; then it loads 3,647 tokens. A static security scan graded it B with 1 finding (asks for root). No closer match exists in the catalogue, so it is treated as the original; first seen 2026-08-30.

Related

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