plan

A planning workflow that breaks an approved PRD into independent feature plans. A PRD is a product requirements document describing what should be built.

In plain words
What is it for?
Use it after design to choose feature boundaries, make architectural decisions, and create implementation-ready plans.
Why use it?
It turns a large product request into smaller vertical slices that can be implemented and checked separately while keeping each one tied to user needs.

Skill for Claude CodeCodex

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 skills/bugroger/beastmode/plan
Any agent
npx skills add BugRoger/beastmode --skill plan
Clone the repo
git clone --depth 1 https://github.com/BugRoger/beastmode

Made for: Claude Code, Codex.

Per session 30 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 3,377 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 $0.00030 $0.03377
Opus 5 $0.00015 $0.01688
Sonnet 5 $0.00006 $0.00675
Haiku 4.5 $0.00003 $0.00338

Measured 2d ago against content hash 2d5629bb6e8e, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

plan 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.

plugin/skills/plan/SKILL.md · 370 lines

How it starts

The opening of the file, as written. The whole thing — 370 lines — stays where its author put it; the contents beside it link to each section on GitHub.

/plan

Decompose a PRD into independent feature plans. Each feature is a vertical slice that can be implemented separately via /implement.

Guiding Principles

  • No Plan Mode — this skill manages its own flow. EnterPlanMode/ExitPlanMode restrict Write/Edit tools and break the workflow.
  • Session metadata is the source of truth — the session-start hook injects a metadata block with epic-id, epic-slug, parent artifacts, and output-target. Use these values verbatim — do NOT re-derive, re-extract, or generate alternatives.
  • Thin vertical slices — each feature cuts through all relevant layers end-to-end, independently implementable
  • Features map to user stories — every feature traces back to at least one PRD user story; no orphan features
  • Wave number is the sole ordering primitive — no explicit dependency graph between features, just wave numbers
  • Architectural, not procedural — feature plans describe WHAT to build, not step-by-step HOW; /implement discovers file paths and generates code

Phase 1: Execute

0. Check Research Trigger

Research triggers if ANY:

  • Arguments contain research keywords
  • Design references unfamiliar technology
  • Complex integration required

If triggered, spawn an Explore agent as the researcher. It receives the research topic and returns findings with sources. Save findings, summarize to user and continue to next step.

1. Explore Codebase

Understand:

  • Existing patterns, conventions, and architecture
  • Module boundaries and interfaces
  • Test structure and commands
  • Dependencies and build tools

2. Identify Durable Architectural Decisions

Before slicing into features, identify high-level decisions that span the entire design and are unlikely to change during implementation:

  • Route structures and API contracts
  • Schema shapes and data models
  • Authentication and authorization approach
  • Service boundaries and module interfaces
  • Shared infrastructure choices
  • Deep modules (per Ousterhout's A Philosophy of Software Design): look for opportunities where a simple, narrow interface can hide significant implementation complexity. Prefer modules whose public surface rarely changes even as internals evolve. Flag shallow modules — those whose interface is nearly as complex as their implementation — as candidates for consolidation or redesign.

Read the full file on GitHub · 370 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 · 370 lines · 30 tokens per session scan A 2d5629bb6e8e

Subscribe to this mod's changes

plan is a skill published in the GitHub repository BugRoger/beastmode (16 stars, last pushed 4mo ago), licensed MIT. It adds 30 tokens to every session and 3,377 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 2026-08-30.

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