Companion Runtime

Q: What is a Claude Code skill and how does the Companion Runtime skill fit in?

A Claude Code skill is a SKILL.md file that lives under ~/.claude/skills/<name>/ and tells the Claude Code CLI agent how to perform a specific task (instructions, prompts, allowed tools). Skills are auto-discovered at session start. Companion Runtime is one of 67,000+ skills indexed in the open ClaudSkills catalog, classified under the General category. Learn more at https://claudskills.com/learn/what-is-skill-md/.

Category: General · Sub-category: ai-tooling · Last updated: 2026-10-25

ai:agent

Internal contract for invoking the agent-collaboration companion runtime (agent-companion.mjs). Use when a driver or subagent needs to construct companion CLI calls.

Security AStatic scan found no risk patternsHow grading works ›

From the source SKILL.md

The single shared runtime is ${CLAUDE_PLUGIN_ROOT}/scripts/agent-companion.mjs. There is one runtime, not one per harness — per-harness CLI construction lives in adapters/<harness>.mjs (buildCommand), not here. This contract is the faithful generalization of codex-plugin-cc's codex-cli-runtime skill.

What this skill does

Companion Runtime is a community-contributed Claude Code skill in the ai-tooling sub-category. It ships as a SKILL.md file that Claude Code auto-discovers under ~/.claude/skills/companion-runtime/ and loads when your prompt matches the skill's trigger.

When to invoke it: Use when a driver or subagent needs to construct companion CLI calls.

Who uses this skill

The Companion Runtime Claude Code skill is built for Claude Code users and developers across all disciplines looking for general-purpose AI assistance. It's part of ClaudSkills (also referred to as Claude Skills or Claude Code Skills) — the open community-curated registry of 211,000+ SKILL.md files for Anthropic's Claude Code agent and the wider Claude ecosystem (Claude API, Claude Agent SDK).

How to install

Free

Manual install (2 steps)

mkdir -p ~/.claude/skills/companion-runtime
curl -L https://claudskills.com/skills/companion-runtime/SKILL.md \
  -o ~/.claude/skills/companion-runtime/SKILL.md

Or just download SKILL.md directly and drop it into ~/.claude/skills/companion-runtime/. Claude Code auto-discovers it on next session.

Skills live at ~/.claude/skills/companion-runtime/SKILL.md on macOS/Linux, or %USERPROFILE%\.claude\skills\companion-runtime\SKILL.md on Windows. See the full install guide for step-by-step instructions.

📱 Install from your phone or desktop Telegram

Open @claudskills_bot on Telegram, tap Open Desktop App, and the desktop app installs this skill for you. Or share the bot link with a colleague — they get the same one-tap install. Learn more →

Pro

One-click install via the desktop app

The ClaudSkills desktop app installs any skill directly into ~/.claude/skills/ with one click — no terminal required. Pro starts at $9/mo or $149 lifetime.

Pro

For the full experience including quality scoring and one-click install features for each skill — upgrade to Pro.

See pricing → Download desktop app

Frequently asked questions

How do I install the Companion Runtime Claude Code skill?

Install via the ClaudSkills desktop app (one click) or copy SKILL.md from the source repository to ~/.claude/skills/companion-runtime/SKILL.md and restart Claude Code. Both flows are detailed at claudskills.com/install/.

What does the Companion Runtime skill do?

Internal contract for invoking the agent-collaboration companion runtime (agent-companion.mjs). Use when a driver or subagent needs to construct companion CLI calls.

Is this skill free to install?

Yes. ClaudSkills is an open registry — every skill keeps its source repository's license, and manual install via copy is free. ClaudSkills Pro ($9/mo, $79/yr, or $149 one-time) adds one-click install via the desktop app and a multi-signal Quality Score.

When should I use the Companion Runtime skill?

Use Companion Runtime when your Claude Code task falls under the General category — specifically in the ai tooling area. Claude Code auto-discovers installed skills and invokes the right one based on the task description, so you can also ask Claude directly (e.g. "use Companion Runtime" or describe the task and let Claude pick). Browse related skills at /category/general/.

What is a Claude Code skill and how does the Companion Runtime skill fit in?

A Claude Code skill is a SKILL.md file that lives under ~/.claude/skills/<name>/ and tells the Claude Code CLI agent how to perform a specific task (instructions, prompts, allowed tools). Skills are auto-discovered at session start. Companion Runtime is one of 67,000+ skills indexed in the open ClaudSkills catalog, classified under the General category. Learn more at /learn/what-is-a-claude-skill/.

Attribution & license

Source: https://github.com/danielskiftesvik/agent-collaboration/blob/c180731c17019cbbf30c1e5b835f1359849dc589/skills/companion-runtime/SKILL.md
License: Apache-2.0
Author: danielskiftesvik

Cite this skill

If you reference this skill in a blog post, paper, or documentation, you can cite it as:

APA

danielskiftesvik. (2026). Companion Runtime [Claude Code skill]. ClaudSkills. https://claudskills.com/skills/companion-runtime/

BibTeX

@misc{companion-runtime-2026,
  author    = {danielskiftesvik},
  title     = {Companion Runtime [Claude Code skill]},
  year      = {2026},
  publisher = {ClaudSkills},
  url       = {https://claudskills.com/skills/companion-runtime/}
}

Embed this skill

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Badge

[![ClaudSkills](https://claudskills.com/badge/companion-runtime.svg)](https://claudskills.com/skills/companion-runtime/?utm_source=badge&utm_medium=readme&utm_campaign=skill_badge)

Security scan

Grade A · scanned 2026-10-25 — free static scan against the OWASP Agentic Skills Top 10.

No risk patterns were found in any of the ten OWASP-aligned categories. How grading works ›

✓ Prompt injection
✓ Data exfiltration
✓ Supply chain
✓ Reverse shell
✓ Credentials
✓ Execution
✓ Filesystem
✓ Persistence
✓ Obfuscation
✓ Network

Show this grade on your repo (click to copy):

[![Security: A](https://img.shields.io/badge/Security-A-2e7d32)](https://claudskills.com/skills/companion-runtime/#security)

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Part of ClaudSkills — the open registry for Claude Skills & Claude Code Skills. · What's New · Install guide · About · llms.txt

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