Frontier Engineer

Frontier Engineer is an agent for Claude Code from jnPiyush/AgentX. It costs 63 tokens per session (6,155 once invoked), scanned A, original, Apache-2.0.

A software-engineering agent for implementing features, fixing bugs, and writing tests through a staged development process. It covers research, planning, implementation, testing, and review, with checkpoints between phases.

In plain words
What is it for?
Use it for feature development, bug fixes, regression tests, implementation planning, code cleanup, and final review.
Why use it?
It provides a repeatable path from a request to reviewed, tested code and makes the expected project context explicit before changes begin.

Agent for Claude Code

Written for Claude Code: user-invocable in frontmatter. Also seen: model in frontmatter; mentions subagents.

Needs its repository: it reads a path above its own folder, which exists only inside the repository. The line is **Shared Protocols**: Follow [WORKFLOW.md](../../docs/WORKFLOW.md#handoff-flow) for handoff workflow and agent communication..

Good fit Use it for feature development, bug fixes, regression tests, implementation planning, code cleanup, and final review.

Compare 6 agents from other repositories ↓
Install

Getting it into your agent

It runs from inside its repository, so the clone comes first — what it calls does not travel with the file alone.

Clone the repo
git clone --depth 1 https://github.com/jnPiyush/AgentX
agentmods
npx agentmods add agents/jnpiyush/agentx/engineer

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 Frontier Engineer

README.md
[![agentmods](https://agentmods.dev/badge/agents/jnpiyush/agentx/engineer/github.svg)](https://agentmods.dev/agents/jnpiyush/agentx/engineer)
Your own site
<a href="https://agentmods.dev/agents/jnpiyush/agentx/engineer"><img src="https://agentmods.dev/badge/agents/jnpiyush/agentx/engineer/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 Frontier Engineer

Your own site · 80×15
<a href="https://agentmods.dev/agents/jnpiyush/agentx/engineer"><img src="https://agentmods.dev/badge/agents/jnpiyush/agentx/engineer.svg" alt="Reviewed on agentmods" width="80" height="20"></a>
Per session 63 Only the description is in the session, so the agent can decide to use it. The body loads when it is invoked.
When invoked 6,155 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 $0.00063 $0.06155
Opus 5.5 $0.00025 $0.02462
Sonnet 5.5 $0.00013 $0.01231
Haiku 4.5 $0.00006 $0.00615

Measured 4d ago against content hash 2cfd62b04adc, method: parsed. Prices are Anthropic first-party input rates as of 2026-10-07, from the pricing page.

Security

Grade A, and why

Frontier Engineer 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 4d 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.

.github/agents/engineer.agent.md · 506 lines

How it starts

The opening of the file, as written. The whole thing — 506 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Software Engineer Agent

You implement features, fix bugs, and write tests. PRDs, architecture, UX specs, CI/CD pipelines and review documents belong to other roles; route those requests to the owning agent (architecture questions go to the Architect).

You implement through Compound Engineering: read the full artifact chain, choose an approach deliberately, plan concretely, implement carefully, test rigorously, and review critically before handoff.

Trigger & Status

  • Trigger: type:story, type:bug, or Status = Ready (with ADR + Spec complete)
  • Status Flow: Ready -> In Progress -> In Review (scoped evidence ready; owning loop completes after final independent verdict when applicable)
  • Bugs: Skip PM/Architect phases. Write failing regression test first, then fix.

Compound Engineering Pipeline

Follow the ordered phases below; each gate must pass before the next phase.

Quick Phase Reference

Phase MUST Load Skill MUST Produce
1. Research karpathy-guidelines, iterative-loop, core-principles, testing, language instruction Current graph slice + artifact summary + ambiguity list + reuse inventory
2. Brainstorm core-principles Chosen approach + rationale
3. Plan api-design, database if applicable File inventory + test plan + reuse decision per item
4. Design core-principles Interfaces + DRY/reuse check
5. Implement Language instruction, ai-agent-development and prompt-engineering if needs:ai, systematic-debugging if 2+ fixes failed Committed code + loop started
5b. Scrub scrub Read-only advisory report; cosmetic findings LOW; cleanup deferred for consent
6. Test readiness testing, ai-evaluation if needs:ai, verification-before-completion Cases authored + ACs mapped + non-test checks; suites deferred
7. Review code-review, security Output score >=70% + code-quality rubric >=80%

Skills live at .github/skills/<category>/<skill>/SKILL.md; Skills.md maps names to paths.

Read the full file on GitHub · 506 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. 4d ago Changed · +10 lines 2cfd62b04adc
  2. 7d ago Changed · +14 lines · -2 tokens per session 1d5f06feeeb3
  3. 20d ago Changed · +6 lines 6d56a7778077
  4. 23d ago Changed · -47 lines f560db19e5d4
  5. 29d ago Changed · +13 lines 02908d057453
  6. 1mo ago Changed · +2 tokens per session 8e613dcacf23
  7. 1mo ago Changed · +44 lines c7195cc75998
  8. 1mo ago First seen · 466 lines · 63 tokens per session scan A d3e02b6c4ccc

Subscribe to this mod's changes

Frontier Engineer is an agent published in the GitHub repository jnPiyush/AgentX (16 stars, last pushed 3d ago), licensed Apache-2.0. It adds 63 tokens to every session and 6,155 once invoked, about $0.0003 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.

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