implementation

An implementation instruction set for making approved code changes within the project's documented engineering method. It defines how to check the repository context, stay within scope, and validate the result.

In plain words
What is it for?
Use it when implementing an approved plan, reviewing the required project documents, applying the defined engineering contract, and producing validated production code.
Why use it?
It prevents unapproved feature work, architectural drift, speculative abstractions, and unrelated refactoring. It keeps implementation aligned with the active plan and project conventions.

Command for Codex

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 commands/pueraeternis/agentic-project-template/implementation
Clone the repo
git clone --depth 1 https://github.com/pueraeternis/agentic-project-template

Made for: Codex.

Per session 0 Only the description is in the session, so the agent can decide to use it. The body loads when it is invoked.
When invoked 369 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 $0.00000 $0.00369
Opus 5 $0.00000 $0.00185
Sonnet 5 $0.00000 $0.00074
Haiku 4.5 $0.00000 $0.00037

Measured 2d ago against content hash 6093bba9ee13, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

implementation 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.

.codex/prompts/implementation.md · 99 lines

What it actually says

Implementation Prompt

Implement the requested changes using the Agentic Engineering Methodology.


Objective

Implement the approved engineering contract.

The implementation should:

  • remain within the approved scope;
  • preserve repository consistency;
  • respect the documented architecture;
  • follow the documented engineering conventions;
  • produce production-ready code.

Repository Context

Before implementation, review the repository in the following order:

  1. AGENTS.md
  2. docs/project/PROJECT.md
  3. docs/project/ROADMAP.md
  4. docs/project/ARCHITECTURE.md
  5. docs/project/ENGINEERING.md
  6. Relevant ADRs
  7. Active implementation plan
  8. docs/project/PROGRESS.md

Confirm that implementation is authorized by an active approved plan.


Implementation Rules

Implement only the approved scope.

Respect:

  • architectural boundaries;
  • engineering conventions;
  • repository organization;
  • project validation requirements.

Do not:

  • redesign the architecture;
  • modify project goals;
  • introduce unrelated refactoring;
  • implement future roadmap phases;
  • add speculative abstractions;
  • silently expand scope.

Prefer the simplest implementation that satisfies the documented requirements.


Documentation

If implementation changes:

  • architecture;
  • engineering decisions;
  • repository workflow;
  • permanent project knowledge;

update the appropriate documentation as part of the same change.

Do not leave the repository in an inconsistent state.


Validation

Before considering the implementation complete:

  • verify the acceptance criteria;
  • execute the validation workflow defined in ENGINEERING.md;
  • ensure documentation is consistent;
  • confirm no unrelated changes remain.

Deliverable

Provide:

  1. Implementation Summary
  2. Files Changed
  3. Validation Performed
  4. Documentation Updated
  5. Follow-up Work Requiring a New Implementation Plan

Do not propose additional features unless explicitly requested.

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 · 99 lines · 0 tokens per session scan A 6093bba9ee13

Subscribe to this mod's changes

implementation is a command published in the GitHub repository pueraeternis/agentic-project-template (2 stars, last pushed 2mo ago), licensed MIT. It costs nothing until one of its globs matches a file; then it loads 369 tokens. 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.