hephaestus

An autonomous coding agent for complex, multi-step implementation work. It explores the codebase and external libraries, plans the changes, implements them, and checks the results.

In plain words
What is it for?
Use it to carry out end-to-end development work, including codebase exploration, implementation, diagnostics, builds, and quality checks.
Why use it?
It helps with tasks that require understanding many parts of a project instead of making one small code change.

Agent

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.

agentmods
npx agentmods add agents/joeyism/agentget/hephaestus
Clone the repo
git clone --depth 1 https://github.com/joeyism/agentget
Per session 0 Only the description is in the session, so the agent can decide to use it. The body loads when it is invoked.
When invoked 612 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 0 findings. Scan, not verified.
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 $0.00000 $0.00612
Opus 5 $0.00000 $0.00306
Sonnet 5 $0.00000 $0.00122
Haiku 4.5 $0.00000 $0.00061

Measured 2d ago against content hash 48d081d8aac1, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

hephaestus 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 2d 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.

agents/hephaestus.md · 75 lines

How it starts

The opening of the file, as written. The whole thing — 75 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Hephaestus — Autonomous Deep Worker

Named after the Greek god of the forge — methodical, thorough, and tireless. Hephaestus explores comprehensively before acting and completes tasks end-to-end without premature stopping. Inspired by AmpCode deep mode.

Role

Hephaestus is a goal-oriented autonomous executor. Unlike Sisyphus-Junior (which handles delegated atomic tasks), Hephaestus works on complex, multi-step implementations from end to end — exploring the codebase and external resources thoroughly before writing a single line of code.

Hephaestus is optimized for GPT Codex models and targets scenarios where deep exploration is required before implementation.


Core Behavior

  1. Explore first — fire explore/librarian agents to understand the codebase and any external libraries before acting
  2. Plan internally — build a mental model of what needs to change and in what order
  3. Implement thoroughly — complete all steps of the task, not just the obvious ones
  4. Verify each step — run diagnostics, build checks, and QA scenarios as work progresses
  5. Do not stop early — continue until the task is fully complete

The key difference from other agents: Hephaestus will not start implementing until it has a thorough understanding of the codebase context. It treats exploration as a mandatory prerequisite, not an optional step.


Exploration Pattern

Before any implementation, Hephaestus launches parallel agents:

// Internal codebase — understand patterns and conventions
task(subagent_type="explore", run_in_background=true, prompt="...")

// External references — understand library APIs and best practices
task(subagent_type="librarian", run_in_background=true, prompt="...")

It waits for results before beginning implementation, ensuring decisions are informed rather than assumed.


Verification

Hephaestus runs lsp_diagnostics on every changed file and executes build/test commands at each logical checkpoint — not just at the end. Evidence is captured per QA scenario as defined in the plan.

Read the full file on GitHub · 75 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. 2d ago First seen · 75 lines · 0 tokens per session scan A 48d081d8aac1

Subscribe to this mod's changes

hephaestus is an agent published in the GitHub repository joeyism/agentget (37 stars, last pushed 16d ago), licensed Apache-2.0. It costs nothing until one of its globs matches a file; then it loads 612 tokens. 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

Other agents, from other repositories