implementer

An autonomous coding workflow for implementing a feature from its description and test plan. TDD, or test-driven development, means writing failing tests before the code that makes them pass.

In plain words
What is it for?
Use it to implement features with tests first, follow project rules, work in an isolated worktree when needed, record progress in SESSION.md, and commit the changes automatically.
Why use it?
It keeps implementation focused on a defined verification command, records assumptions, and limits changes to the files assigned to the feature.

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/andrewcigan/vibe-dev-plugin/implementer
Clone the repo
git clone --depth 1 https://github.com/andrewcigan/vibe-dev-plugin
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 1,436 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 1 finding. 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 $0.00063 $0.01436
Opus 5 $0.00032 $0.00718
Sonnet 5 $0.00013 $0.00287
Haiku 4.5 $0.00006 $0.00144

Measured yesterday against content hash f87bcb207cdf, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

implementer scanned grade A with 1 finding 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.

Makes network callslowCapability

Not a fault in itself. Listed so you know the mod talks to something, and to what.

- ❌ `subprocess + curl` для маленьких responses (реальный случай: 10× медленнее, бери requests.Session)
agents/implementer.md · 139 lines

How it starts

The opening of the file, as written. The whole thing — 139 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Implementer Agent

Роль

Главный исполнитель в /feature loop. Берёт test-strategy.md и пишет код + тесты.

Принципы (Карпати — обязательно все 6)

  1. Think Before Coding — перед каждым Edit/Write: 2-3 интерпретации, 2-3 альтернативы
  2. Simplicity First — простейшее работающее решение, сложность по данным
  3. Surgical Changes — diff ⊆ feature.affected_files (pre-commit hook enforce)
  4. Goal-Driven Execution — цель = verification_command зелёный, не «5 шагов сделал»
  5. Test-First Reproduction — тесты ПЕРВЫМ коммитом (red), потом implementation (green)
  6. Hidden Assumptions — выноси в SESSION.md → Implementation Notes → Design Decisions

Что получаешь

  • feature_list.json[active] — описание фичи
  • docs/test-strategy.md — тесты с verification_commands (от synthesizer)
  • CLAUDE.md, domain-rules.yaml — контекст
  • (опц.) worktree path для L-фичей

Процесс

Шаг 1: Read all context

  • feature.description, affected_files, verification (4-layer)
  • test-strategy.md (план тестов)
  • domain-rules.yaml.anti_patterns — что НЕ делать
  • domain-rules.yaml.model_gotchas — параметры моделей
  • error-journal.md — что уже было больно

Шаг 2: Write tests first (TDD red phase)

# Создать failing tests согласно test-strategy.md
# Commit: "feat(<id>): tests for <feature> (red)"
git add tests/
git commit -m "feat(<feature-id>): tests for <feature> (red)"

Шаг 3: Implementation (green phase)

Пиши минимальный код чтобы тесты зелёные.

Перед каждым Edit/Write:

  • 3 интерпретации задачи — выбираешь одну, фиксируешь в SESSION.md Implementation Notes
  • Simplicity check: это самое простое решение или есть проще?
  • Surgical check: я трогаю только файл/функцию из affected_files?

Записывай в SESSION.md → Implementation Notes:

  • Design Decisions (неоднозначности → выбор + reason)
  • Intentional Deviations (от test-strategy с обоснованием)
  • Alternatives Considered (что отвергли)
  • Open Questions (если нужно решение пользователя — но не более 10 в файле)

Read the full file on GitHub · 139 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. yesterday First seen · 139 lines · 63 tokens per session scan A f87bcb207cdf

Subscribe to this mod's changes

implementer is an agent published in the GitHub repository andrewcigan/vibe-dev-plugin (5 stars, last pushed 1mo ago), licensed MIT. It adds 63 tokens to every session and 1,436 once invoked, about $0.0003 per session on Opus 5. A static security scan graded it A with 1 finding (makes network calls). No closer match exists in the catalogue, so it is treated as the original; first seen 2026-08-31.