plan-eng

plan-eng is a skill for Claude Code, Codex from Dragoon0x/dragoon-skills. It costs 116 tokens per session (305 once invoked), scanned A, original, MIT.

A command that writes a structured engineering plan in Markdown, filled with facts about the current codebase. The plan covers the design, edge cases, tests, rollout, and review.

In plain words
What is it for?
Use it after a brief or before a substantial feature, such as adding user invitations, to prepare architecture decisions, a test matrix, migration steps, and a review checklist.
Why use it?
It turns a feature idea into an implementation outline grounded in the project's existing technology and quality standards.

Skill for Claude CodeCodex

Written for no agent in particular: nothing here depends on one. Also seen: reads .claude/ paths.

Good fit Use it after a brief or before a substantial feature, such as adding user invitations, to prepare architecture decisions, a test matrix, migration steps, and a review checklist.

Compare 6 skills from other repositories ↓
Install with agentmods
npx agentmods add skills/dragoon0x/dragoon-skills/plan-eng
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.

Any agent
npx skills add Dragoon0x/dragoon-skills --skill plan-eng
Clone the repo
git clone --depth 1 https://github.com/Dragoon0x/dragoon-skills

Made for: Claude Code, Codex.

Wrote this? Show the measurements

A badge with what this costs and how it scanned, read live from this page, so it follows the numbers instead of freezing them. Markdown for a README, HTML for a documentation site or a project page.

agentmods badge for plan-eng

README.md
[![agentmods](https://agentmods.dev/badge/skills/dragoon0x/dragoon-skills/plan-eng/github.svg)](https://agentmods.dev/skills/dragoon0x/dragoon-skills/plan-eng)
Your own site
<a href="https://agentmods.dev/skills/dragoon0x/dragoon-skills/plan-eng"><img src="https://agentmods.dev/badge/skills/dragoon0x/dragoon-skills/plan-eng/github.svg" alt="Measured on agentmods" height="20"></a>

Or the 80×15 button, for a site that already has a row of RSS and ATOM ones. Only the verdict fits; the numbers stay here.

agentmods 80×15 button for plan-eng

Your own site · 80×15
<a href="https://agentmods.dev/skills/dragoon0x/dragoon-skills/plan-eng"><img src="https://agentmods.dev/badge/skills/dragoon0x/dragoon-skills/plan-eng.svg" alt="Reviewed on agentmods" width="80" height="20"></a>
Per session 116 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 305 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 0 findings. A grade says what 26 rules found in the file — not that it is safe.
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 5.1 $0.00116 $0.00305
Opus 5 $0.00058 $0.00152
Sonnet 5 $0.00023 $0.00061
Haiku 4.5 $0.00012 $0.00030

Measured 9d ago against content hash b4d8f7dd5570, method: parsed. Prices are Anthropic first-party input rates as of 2026-09-09, from the pricing page.

Security

Grade A, and why

plan-eng 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 9d ago.

The scan reads SKILL.md. This mod also ships 1 executable file (scripts/plan-eng.js), listed below but not scanned — reading those needs a real analyzer, not pattern matching.

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.

skills/plan-eng/SKILL.md · 32 lines

What it actually says

/plan-eng

Generates an engineering plan template that respects the codebase's stack and current quality bar.

When to use

  • After /brief, before implementation
  • The user asks for "an engineering plan", "an architecture doc", "a design doc"
  • Non-trivial features (anything more than a one-file change)

Output sections

  • architecture (data model, api, state)
  • edge cases (forces at least 5)
  • test matrix (unit, integration, e2e, perf)
  • existing dependencies (auto-loaded from package.json)
  • migration / rollout (flags, backfill, rollback, observability)
  • review checklist (gated on /critique threshold)

Run it

dragoon plan-eng "add user invites"
dragoon plan-eng "add user invites" --apply
Files

What ships with it

1 file beside SKILL.md in the same directory: the scripts, references and assets a skill reads on demand. Not counted in the per-session cost; read them before you install if any of them is executable.

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. 9d ago First seen · 32 lines · 116 tokens per session scan A b4d8f7dd5570

Subscribe to this mod's changes

plan-eng is a skill published in the GitHub repository Dragoon0x/dragoon-skills (4 stars, last pushed 4mo ago), licensed MIT. It adds 116 tokens to every session and 305 once invoked, about $0.0006 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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