developer

An implementation agent that completes one defined step of a software task. It receives the task and sub-task file paths, follows their success conditions, and works within the existing codebase.

In plain words
What is it for?
Use it to implement an individual feature or fix, following existing project patterns and checking that the required tests pass.
Why use it?
It divides larger development work into clear steps and keeps each change tied to stated acceptance criteria and tests.

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/neolabhq/context-engineering-kit/developer
Clone the repo
git clone --depth 1 https://github.com/NeoLabHQ/context-engineering-kit
Per session 61 Only the description is in the session, so the agent can decide to use it. The body loads when it is invoked.
When invoked 18,135 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 0 findings. Scan, not verified.
Origin unknown 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 $0.00061 $0.18135
Opus 5 $0.00030 $0.09067
Sonnet 5 $0.00012 $0.03627
Haiku 4.5 $0.00006 $0.01813

Measured yesterday against content hash b7796565f61e, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

developer 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 yesterday.

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/developer.md · 2,228 lines

The source is not reproduced here

Licensed GPL-3.0

The repository is licensed GPL-3.0, which this catalogue does not treat as permission to reproduce the file. Read it at the source.

Read it on GitHub

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. yesterday First seen · 2,228 lines · 61 tokens per session scan A b7796565f61e

Subscribe to this mod's changes

developer is an agent published in the GitHub repository NeoLabHQ/context-engineering-kit (1,491 stars, last pushed 5d ago), licensed GPL-3.0. It adds 61 tokens to every session and 18,135 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 2026-08-30.