hephaestus-build

hephaestus-build is a skill for Claude Code from agentlas-ai/Agentlas-OS. It costs 60 tokens per session (2,083 once invoked), scanned A, original, Apache-2.0.

A command for building an Agentlas agent or multi-agent team, including packaging an existing local or external agent into the Agentlas structure.

In plain words
What is it for?
Use it when creating agents, assembling teams, or converting existing Claude, Codex, or Gemini workspaces.
Why use it?
It provides a defined build process for turning an agent idea or existing workspace into reusable Agentlas architecture.

Skill for Claude Code

Written for Claude Code: ${CLAUDE_PLUGIN_ROOT variable. Also seen: mentions CLAUDE.md; mentions Claude Code; mentions AGENTS.md.

Runs only inside a plugin — its command needs a path that Claude Code sets for a plugin’s own hooks and for nothing else, and the catalogue could not identify which plugin ships it.

Good fit Use it when creating agents, assembling teams, or converting existing Claude, Codex, or Gemini workspaces.

Compare 6 skills from other repositories ↓
About the project

Agentlas OS is a local-first system for creating, storing, borrowing, and running specialist AI agents and temporary agent teams through supported hosts and models. It serves people who want reusable agents that remain available across computers and model workspaces, and the catalogue contains its skills, commands, hooks, agents, instructions, plugin, and rule.

agentlas-ai/Agentlas-OS · 1,105 stars · on GitHub · agentlas.cloud

Install

Getting it into your agent

There is no command for this one: it runs only inside a plugin, and the catalogue could not identify which plugin ships it. The source is linked below.

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 hephaestus-build

README.md
[![agentmods](https://agentmods.dev/badge/skills/agentlas-ai/agentlas-os/hephaestus-build.svg)](https://agentmods.dev/skills/agentlas-ai/agentlas-os/hephaestus-build)
Your own site
<a href="https://agentmods.dev/skills/agentlas-ai/agentlas-os/hephaestus-build"><img src="https://agentmods.dev/badge/skills/agentlas-ai/agentlas-os/hephaestus-build.svg" alt="Measured on agentmods" height="20"></a>
Per session 60 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 2,083 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.
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 $0.00060 $0.02083
Opus 5 $0.00030 $0.01042
Sonnet 5 $0.00012 $0.00417
Haiku 4.5 $0.00006 $0.00208

Measured 5d ago against content hash e8ea1c576201, method: parsed. Prices are Anthropic first-party input rates as of 2026-09-08, from the pricing page.

Security

Grade A, and why

hephaestus-build 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 5d 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.

codex/plugins/agentlas-core-engine-meta-agent/skills/hephaestus-build/SKILL.md · 157 lines

How it starts

The opening of the file, as written. The whole thing — 157 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Hephaestus Build

Procedure

  1. Treat this as the public Codex build surface. Do not expose or ask the user to invoke the older internal support skill names.

  2. Resolve the trusted engine root before reading any build contract:

    ENGINE=""
    for candidate in \
      "${CODEX_PLUGIN_ROOT:-}" \
      "${CLAUDE_PLUGIN_ROOT:-}" \
      "${PLUGIN_ROOT:-}" \
      "$HOME/.agentlas/runtime/current/host_adapters/codex/plugins/agentlas-core-engine-meta-agent" \
      "$HOME/.agentlas/runtime/current/host_adapters/claude/plugins/agentlas-core-engine-meta-agent" \
      "$HOME/.agentlas/runtime/current" \
      "."
    do
      if [ -n "$candidate" ] && [ -f "$candidate/AGENTS.md" ] && [ -f "$candidate/package-contract.json" ] && [ -f "$candidate/contracts/builder-interview-research-gate.md" ]; then
        ENGINE="$candidate"
        break
      fi
    done
    [ -n "$ENGINE" ] || { echo "Hephaestus engine not found. Run the installer first." >&2; exit 1; }
    RUNNER=""
    for candidate in "$HOME/.agentlas/runtime/current/bin/hephaestus" "$ENGINE/bin/hephaestus"; do
      if [ -x "$candidate" ]; then RUNNER="$candidate"; break; fi
    done
    [ -n "$RUNNER" ] || { echo "Hephaestus runner not found." >&2; exit 1; }
    

    For an interactive request whose first argument is session, do not resolve a generic PACKAGE_TARGET and do not ask for a JSON/JSONL export. Ask first: "이 세션에서 만든 에이전트를 기본 전역 Agentlas 에이전트 폴더에 만들까요? 다른 위치를 원하면 경로를 알려주세요. 별도 위치를 지정하지 않으면 전역 폴더에 만듭니다." If no alternate location is named, use AGENTLAS_AGENT_HOME or ~/.agentlas/agentlas-agent and create a new safe-slug child package. If a destination is supplied, validate that exact folder. Never overwrite an existing child. The current conversation is the source; do not inspect recent sessions or host databases.

    For every other build request, take exactly one folder explicitly named or confirmed by the user as PACKAGE_TARGET. If none was named, or multiple candidates exist, stop and ask. Never default to ., the cwd, or $ENGINE. Run "$RUNNER" contract resolve-target "$PACKAGE_TARGET" --base "$PWD" and set PACKAGE_ROOT only to the status-ok receipt's exact package_root. Nonzero or error receipts are blockers.

Read the full file on GitHub · 157 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. 5d ago First seen · 157 lines · 60 tokens per session scan A e8ea1c576201

Subscribe to this mod's changes

hephaestus-build is a skill published in the GitHub repository agentlas-ai/Agentlas-OS (1,105 stars, last pushed 2d ago), licensed Apache-2.0. It adds 60 tokens to every session and 2,083 once invoked, about $0.0003 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 2026-09-03.

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