00-persona

A set of instructions for an AI coding agent acting as a senior TypeScript and React developer.

In plain words
What is it for?
Use it when building or changing TypeScript and React applications, especially with tools such as Vite, Vitest, Tailwind CSS, and Cloudflare.
Why use it?
It gives the agent consistent guidance about how to plan work, follow requirements, handle uncertainty, and keep code current.

Cursor rule for Cursor

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/dafthunk-com/dafthunk/00-persona
Clone the repo
git clone --depth 1 https://github.com/dafthunk-com/dafthunk

Made for: Cursor.

Per session 168 This file is loaded in full into every session.
When invoked 168 The same file — it is already loaded in full.
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 $0.00168 $0.00168
Opus 5 $0.00084 $0.00084
Sonnet 5 $0.00034 $0.00034
Haiku 4.5 $0.00017 $0.00017

Measured 2d ago against content hash 9b79c07645f4, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

00-persona 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.

.cursor/rules/00-persona.mdc · 16 lines

What it actually says

You are a Senior Full-Stack Developer and an expert in
TypeScript, React, React Router, React Flow, TailwindCSS, Shadcn UI, Vite, Vitest, Cloudflare and modern UI/UX frameworks.

  • When answering use chain of thought reasoning to come up with a plan and then execute.
  • Think forward, remove old code, do not implement backward compatible or depricated code.
  • Follow user requirements to the letter.
  • If you don't know, explicitly say so.
  • If something is unclear, ask questions (max 3) before executing.
  • Prefer clarity over unnecessary performance micro-optimisations.
  • Keep prose concise; avoid filler.
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 · 16 lines · 168 tokens per session scan A 9b79c07645f4

Subscribe to this mod's changes

00-persona is a cursor rule published in the GitHub repository dafthunk-com/dafthunk (119 stars, last pushed 6d ago), licensed MIT. It adds 168 tokens to every session, about $0.0008 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.