core

A set of rules that controls whether the coding agent is planning changes or making them. It requires the user to approve a plan before the agent edits the code.

In plain words
What is it for?
Use it when you want to review a plan before code changes happen, then explicitly switch to making those changes.
Why use it?
It prevents unapproved changes and makes the agent’s current working mode clear. It also creates a predictable approval step between discussing work and applying it.

Cursor rule

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 rules/barisercan/cursorrules/core
Clone the repo
git clone --depth 1 https://github.com/barisercan/cursorrules
Per session 256 This file is loaded in full into every session.
When invoked 256 The same file — it is already loaded in full.
Security scan A 0 findings. Scan, not verified.
Origin 94% copy Near-identical to another mod 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 $0.00256 $0.00256
Opus 5 $0.00128 $0.00128
Sonnet 5 $0.00051 $0.00051
Haiku 4.5 $0.00026 $0.00026

Measured 2d ago against content hash 5c397b95ba85, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

core 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.

Origin

This is a copy

94% identical to core — 7 lines differ, which has more behind it and is treated as the original. This page carries a canonical link to it rather than competing with it.

core.mdc · 23 lines

What it actually says


description: Define core operation modes (Plan vs Act) with explicit user approval workflow globs: "**/*" alwaysApply: true

Core Rules

You have two modes of operation:

  1. Plan mode - You will work with the user to define a plan, you will gather all the information you need to make the changes but will not make any changes
  2. Act mode - You will make changes to the codebase based on the plan
  • You start in plan mode and will not move to act mode until the plan is approved by the user.
  • You will print # Mode: PLAN when in plan mode and # Mode: ACT when in act mode at the beginning of each response.
  • Unless the user explicity asks you to move to act mode, by typing ACT you will stay in plan mode.
  • You will move back to plan mode after every response and when the user types PLAN.
  • If the user asks you to take an action while in plan mode you will remind them that you are in plan mode and that they need to approve the plan first.
  • When in plan mode always output the full updated plan in every response.
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 · 23 lines · 256 tokens per session scan A 5c397b95ba85

Subscribe to this mod's changes

core is a cursor rule published in the GitHub repository barisercan/cursorrules (35 stars, last pushed 1y ago), licensed MIT. It adds 256 tokens to every session, about $0.0013 per session on Opus 5. A static security scan graded it A with 0 findings. It is 94% identical to core, differing in 7 lines, and is treated as a copy.