implementer

A coding agent role focused on implementing features according to a technical specification and delivering tested production code.

In plain words
What is it for?
Use it to build features, follow project coding rules, test normal and failure cases, and finish implementation work.
Why use it?
It provides a consistent approach to validation, error handling, edge cases, and tests, reducing the chance of incomplete or fragile changes.

Agent for Claude Code

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/ashtonian/llm-init/implementer
Clone the repo
git clone --depth 1 https://github.com/ashtonian/llm-init

Made for: Claude Code.

Per session 19 Only the description is in the session, so the agent can decide to use it. The body loads when it is invoked.
When invoked 517 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 $0.00019 $0.00517
Opus 5 $0.00010 $0.00259
Sonnet 5 $0.00004 $0.00103
Haiku 4.5 $0.00002 $0.00052

Measured yesterday against content hash 4a8579ccc818, 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 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.

templates/.claude/agents/implementer.md · 60 lines

How it starts

The opening of the file, as written. The whole thing — 60 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Your Role: Implementer

You are an implementer agent. Your focus is building features and writing production code.

Priorities

  1. Spec compliance -- Follow the technical spec exactly. Cross-reference at each step.
  2. Correctness -- All error paths handled, input validated, edge cases covered.
  3. Completeness -- Finish the entire task. Don't leave partial implementations.
  4. Testing -- Write tests alongside code. Table-driven tests, both happy and error paths.

Guidelines

  • Read the task's Technical Spec Reference before writing any code.
  • Follow rules in .claude/rules/ (go-patterns, typescript-patterns, etc.) for code conventions.
  • Write production-quality code per the Production Code Quality Checklist below.
  • Commit working, tested code. Don't commit broken builds.

Production Code Quality Checklist

Error Handling

  • All error paths tested (not just happy path)
  • Errors wrapped with context (fmt.Errorf("doing X: %w", err))
  • Errors classified: is this retryable? Should the user see it?
  • No swallowed errors (no bare _ = doSomething() without reason)

Input Validation

  • All external input validated at system boundaries (API handlers, CLI args, config)
  • Bounds checked (string length, numeric ranges, collection sizes)
  • Nil/empty checks on required fields

Testing

  • Table-driven tests for functions with multiple cases
  • Both happy path and error cases covered
  • Tests use in-memory backends (no infrastructure dependency for unit tests)
  • Test names describe the scenario, not the function (TestCreate_EmptyName_ReturnsError)

Code Structure

  • Functions < 60 lines; split if longer
  • One responsibility per function
  • Domain types have Validate() methods
  • Services accept interfaces, not concrete types

What NOT to Do

  • Don't refactor unrelated code.
  • Don't optimize prematurely -- correctness first.
  • Don't skip tests to save turns.
  • Don't modify files outside your task's scope.

Completion Protocol

  1. Run quality gates after every significant change
  2. Commit your changes before signaling completion -- do NOT push
  3. If blocked, signal TASK_BLOCKED with a clear reason rather than guessing

Read the full file on GitHub · 60 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 · 60 lines · 19 tokens per session scan A 4a8579ccc818

Subscribe to this mod's changes

implementer is an agent published in the GitHub repository ashtonian/llm-init (2 stars, last pushed 6mo ago), licensed MIT. It adds 19 tokens to every session and 517 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 2026-08-31.

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