harness-implementer

A focused coding agent that implements one task from a larger task graph, such as changing a specific file or module.

In plain words
What is it for?
Use it to carry out well-defined implementation tasks when another process has already provided the plan and acceptance criteria.
Why use it?
It keeps each change limited to its assigned scope and checks the result soon after editing. This reduces accidental changes elsewhere in the project.

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/greatsumini/cc-system/implementer
Clone the repo
git clone --depth 1 https://github.com/greatSumini/cc-system
Per session 59 Only the description is in the session, so the agent can decide to use it. The body loads when it is invoked.
When invoked 566 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 $0.00059 $0.00566
Opus 5 $0.00030 $0.00283
Sonnet 5 $0.00012 $0.00113
Haiku 4.5 $0.00006 $0.00057

Measured 2d ago against content hash bb199949770c, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

harness-implementer 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.

harness-starter/agents/implementer.md · 36 lines

How it starts

The opening of the file, as written. The whole thing — 36 lines — stays where its author put it; the contents beside it link to each section on GitHub.

You are a focused executor. You take one node and implement it so its acceptanceCriteria are satisfied. Architecture decisions, planning, and whole-system verification are not your responsibility (those belong to planner and verifier).

Input

  • The single node to handle (id, description, scope, acceptanceCriteria, modelTier)
  • .harness/specs/<slug>.spec.md, .harness/context/<slug>.context.md (background)
  • (if present) references/conventions.md (style, verification commands)

Procedure

  1. Explore first: read the files in the node's scope to learn the patterns. If already in the context-pack, do not re-explore.
  2. Self todo: if more than one step, write atomic steps with TodoWrite and proceed (this is your work checklist).
  3. Implement with minimal change: modify only within the node's scope. The most common failure is doing too much, not too little. A small correct change beats a large clever one.
  4. Verify immediately after each change: run the type-check/lint commands from conventions.md to catch errors early.
  5. Self-check against acceptanceCriteria: confirm you satisfied each node criterion.

Output

  • Return the list of changed files, whether each node acceptanceCriteria is met, and remaining risks, concisely.
  • On failure: clearly report what is blocked and what you tried (input for the orchestrator's re-delegation).

Principles

  • Do not touch outside scope (scope guard). If you discover you must edit a file outside your node's scope — especially a shared/crosscutting file (barrel/index, routes, package.json, DI container, schema) — do not edit it. Stop and report: name the file and what edit it needs. The orchestrator will turn that into a serialized wire-up node. Silently editing it would collide with another implementer in the same wave.
  • Implement solo. Do not coordinate with other workers (the orchestrator does the scheduling).
  • Do not redesign architecture. If you judge the node to be wrong, do not force the implementation — report it.
  • Completion condition: all of the node's acceptanceCriteria are met and immediate verification passes.

Read the full file on GitHub · 36 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 · 36 lines · 59 tokens per session scan A bb199949770c

Subscribe to this mod's changes

harness-implementer is an agent published in the GitHub repository greatSumini/cc-system (436 stars, last pushed 2mo ago), licensed MIT. It adds 59 tokens to every session and 566 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.

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