rein-plan

rein-plan is a cursor rule for Cursor from jstxn/rein. It costs 31 tokens per session (750 once invoked), scanned A, original, MIT.

A planning step that breaks a complex coding task into ordered actions with risks, checkpoints, and rollback boundaries.

In plain words
What is it for?
Use it when work spans multiple files or modules, when order matters, or when clarified requirements need to be handed to implementation.
Why use it?
It makes dependencies and partial-failure risks visible before implementation begins.

Cursor rule for Cursor

Written for Cursor: installed under .cursor/.

Good fit Use it when work spans multiple files or modules, when order matters, or when clarified requirements need to be handed to implementation.

Compare 6 cursor rules from other repositories ↓
Install with agentmods
npx agentmods add rules/jstxn/rein/rein-plan
View source ↗ jstxn/rein
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.

Clone the repo
git clone --depth 1 https://github.com/jstxn/rein

Made for: Cursor.

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 rein-plan

README.md
[![agentmods](https://agentmods.dev/badge/rules/jstxn/rein/rein-plan.svg)](https://agentmods.dev/rules/jstxn/rein/rein-plan)
Your own site
<a href="https://agentmods.dev/rules/jstxn/rein/rein-plan"><img src="https://agentmods.dev/badge/rules/jstxn/rein/rein-plan.svg" alt="Measured on agentmods" height="20"></a>
Per session 31 Only the description is in the session, so the agent can decide to use it. The body loads when it is invoked.
When invoked 750 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 $0.00031 $0.00750
Opus 5 $0.00015 $0.00375
Sonnet 5 $0.00006 $0.00150
Haiku 4.5 $0.00003 $0.00075

Measured 7d ago against content hash 6b0224090b3e, method: parsed. Prices are Anthropic first-party input rates as of 2026-09-07, from the pricing page.

Security

Grade A, and why

rein-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 7d 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.

.cursor/rules/rein-plan.mdc · 73 lines

How it starts

The opening of the file, as written. The whole thing — 73 lines — stays where its author put it; the contents beside it link to each section on GitHub.

rein-plan

Use this after triage and before implementation when the work involves multiple files, multiple concerns, or a non-obvious execution order.

When To Use

  • The task touches more than two files or modules
  • The execution order matters (migrations before code, types before consumers)
  • There are dependencies between subtasks
  • The risk of a partial implementation is high
  • A completed rein-interview spec bundle already exists and should drive the plan

When Not To Use

  • The task is a single-file, single-concern change
  • Triage already produced a clear, linear path
  • The user explicitly asks to skip planning

Interview Handoff

Before planning, check whether there is a completed rein-interview artifact to consume.

Artifact priority:

  1. If the user provides --from-interview <slug|path>, use that artifact.
  2. If the user provides or references a rein interview handoff --to plan result, use its sourceResult and recommendedSkillInvocation.
  3. Otherwise, look under .rein/specs/ for rein-interview-*/result.json.
  4. If one clearly matches the current task, use it.
  5. If several plausible artifacts exist, prefer the most recent completed one whose intent, desiredOutcome, or inScope matches the task.
  6. If no relevant artifact exists, proceed with normal planning.

When a result.json artifact is available:

  • treat it as the primary source of truth for intent, desired outcome, in-scope, out-of-scope, constraints, acceptance criteria, assumptions, technical context, and execution bridge
  • use spec.md or the transcript only if result.json is insufficient
  • do not silently drift away from the artifact without naming the conflict
  • if the live repo facts conflict with the artifact, call out the mismatch in the plan
  • if the artifact is missing core planning fields, stop and report that the interview bundle is incomplete rather than planning from a hollow result

Steps

  1. Load the relevant rein-interview result.json first when available.
  2. List every discrete subtask required to complete the work.
  3. Identify dependencies between subtasks. Order them so each step has its prerequisites satisfied.
  4. Write each step in change -> verify form.
  5. For each step, state:
    • what changes
    • why this is the minimum sufficient change
    • what must stay untouched
    • what could go wrong
    • how to verify the step succeeded before moving on
  6. Reject speculative abstraction, flexibility, or helper extraction unless the plan explicitly justifies it.
  7. Identify the first safe checkpoint — the earliest point where the repo is in a valid state and work can be paused or reviewed.
  8. Identify rollback boundaries — points where a partial revert is clean rather than destructive.
  9. Flag any step that requires a decision the user has not yet made.

Read the full file on GitHub · 73 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. 7d ago First seen · 73 lines · 31 tokens per session scan A 6b0224090b3e

Subscribe to this mod's changes

rein-plan is a cursor rule published in the GitHub repository jstxn/rein (12 stars, last pushed 4mo ago), licensed MIT. It adds 31 tokens to every session and 750 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.