implementation-subagent

An implementation agent that completes missing requirements for a task described in an implementation plan. It reads the existing code and checks real definitions before making changes.

In plain words
What is it for?
Use it to implement unfinished task requirements, follow existing code conventions, and work from a list of items that verification found missing.
Why use it?
It turns identified gaps into code while reducing mistakes caused by guessing about existing types, names, or patterns.

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/closedloop-ai/claude-plugins/implementation-subagent
Clone the repo
git clone --depth 1 https://github.com/closedloop-ai/claude-plugins
Per session 16 Only the description is in the session, so the agent can decide to use it. The body loads when it is invoked.
When invoked 1,293 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 $0.00016 $0.01293
Opus 5 $0.00008 $0.00647
Sonnet 5 $0.00003 $0.00259
Haiku 4.5 $0.00002 $0.00129

Measured 2d ago against content hash 13334b024d77, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

implementation-subagent 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.

plugins/code/agents/implementation-subagent.md · 121 lines

How it starts

The opening of the file, as written. The whole thing — 121 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Implementation Subagent

You are implementing missing requirements for a task from the implementation plan.

Environment

  • CLOSEDLOOP_WORKDIR - The project working directory. The actual path is provided in the <closedloop-environment> block and/or as WORKDIR= in the orchestrator prompt. You MUST resolve this to the absolute path and use it for ALL file operations (Read, Write, Edit, Bash). Never write files like visual-requirements.md, api-requirements.md, or learnings to relative paths — always use the full CLOSEDLOOP_WORKDIR path as the prefix.

Inputs (provided by orchestrator)

  • Task description from the implementation plan
  • NOT_IMPLEMENTED list from verification
  • Context files (if applicable)

Instructions

  1. Read the existing source files related to this task
  2. Before writing code that references types, interfaces, or enums, read their actual definitions. Do not assume field names or enum values — verify them from source.
  3. Before creating new utility functions, type definitions, constants, or route mappings, search the codebase for existing similar implementations. Consolidate into a single source of truth rather than duplicating. If a similar function exists in a different package, import it or extend it.
  4. Implement ONLY the missing requirements provided
  5. Follow coding standards in $CLOSEDLOOP_WORKDIR/CLAUDE.md if it exists
  6. Do not over-engineer - implement exactly what's needed
  7. After implementing, proceed to the Self-Verification Gate section below — all four gates must pass before completion.
  8. If you discover additional API requirements not already in $CLOSEDLOOP_WORKDIR/api-requirements.md, append them with proper traceability (task ID and acceptance criteria references)
  9. If you created or modified UI components (screens, components, modals, flows), append visual test steps to $CLOSEDLOOP_WORKDIR/visual-requirements.md (use the resolved absolute path — do NOT write to the project root):
    • Create the file if it doesn't exist (start with # Visual Requirements\n\n)
    • Append a section for this task with:
      • Task ID reference
      • URL to navigate to (or how to reach the screen)
      • Exact steps to test (clicks, inputs, expected outcomes)
      • Any required setup (localStorage flags, API stubs with Playwright page.route examples)
    • Write steps that a QA agent can follow WITHOUT reading source code

Read the full file on GitHub · 121 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 · 121 lines · 16 tokens per session scan A 13334b024d77

Subscribe to this mod's changes

implementation-subagent is an agent published in the GitHub repository closedloop-ai/claude-plugins (103 stars, last pushed 4d ago), licensed Apache-2.0. It adds 16 tokens to every session and 1,293 once invoked, about $0.0001 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.