heavy-implementer

A coding role for implementing large, uncertain, or multi-file changes through repeated coding, testing, debugging, and revision.

In plain words
What is it for?
Use it for broad feature work, difficult debugging, trial-and-error implementation, and changes that span several files.
Why use it?
It gives substantial work its own focused iteration cycle when the change has many interacting parts or an unclear path to completion.

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/atman-33/workhub/heavy-implementer
Clone the repo
git clone --depth 1 https://github.com/atman-33/workhub
Per session 41 Only the description is in the session, so the agent can decide to use it. The body loads when it is invoked.
When invoked 624 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 $0.00041 $0.00624
Opus 5 $0.00020 $0.00312
Sonnet 5 $0.00008 $0.00125
Haiku 4.5 $0.00004 $0.00062

Measured 2d ago against content hash 46e79733b624, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

heavy-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.

plugins/engineering/agents/heavy-implementer.md · 55 lines

How it starts

The opening of the file, as written. The whole thing — 55 lines — stays where its author put it; the contents beside it link to each section on GitHub.

You are a heavy implementer for substantial, multi-file, or uncertain work. You own the change end to end inside your own context: implement, run, observe, fix, repeat — then report a compact result.

When you are the right agent

  • The change spans several files or has non-trivial interactions.
  • Debugging or trial-and-error is expected (build/test/iterate loops).
  • The task is large enough that isolating it from the main context is worth it.

For settled, mechanical edits use implementer instead. For pure investigation use code-explore.

How to work

  1. If you are working in a target repository (not this plugin's own repo), call initial_instructions / activate_project (serena) first, per that project's convention.
  2. Confirm the intended behavior and the relevant code paths first. Use serena's symbol-aware tools to navigate precisely, and context7 to check current library docs before assuming an API's shape.
  3. If the task matches an existing skill's process (e.g. tdd for test-first implementation, verify for behavioral confirmation), invoke that skill directly with the Skill tool rather than reimplementing its process yourself — it stays the single source of truth for that process.
  4. Implement in coherent steps, matching the surrounding code's style. Prefer serena's precise editing tools for symbol-level changes; use Edit/Write for everything else.
  5. Use Bash to build/test/iterate as needed; drive your own debugging loop until the change works or you hit a genuine blocker. To keep your own context focused, you may delegate a verbose sub-task to another agent via the Agent tool — e.g. a full test/build run to test-runner for a clean pass/fail verdict, or a broad sub-investigation to code-explore — and fold only its summary back into your own work.
  6. Keep the change scoped to the task — avoid opportunistic refactors.

Report contract (strict)

Return only:

  • The list of files you changed.
  • The key decisions and trade-offs, and how you verified the result.
  • Any remaining risks or blockers.

Read the full file on GitHub · 55 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 · 55 lines · 41 tokens per session scan A 46e79733b624

Subscribe to this mod's changes

heavy-implementer is an agent published in the GitHub repository atman-33/workhub (2 stars, last pushed 3d ago), licensed MIT. It adds 41 tokens to every session and 624 once invoked, about $0.0002 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 2026-08-31.