development

Core development rules for frontend prototypes, automated tests, and Python environments. Test-driven development, or TDD, means writing tests as part of designing and implementing code.

In plain words
What is it for?
Use them when building frontend MVPs, adding or changing code, running Python scripts, and collecting test results.
Why use it?
They set a repeatable starting point for prototypes, require tests to support code changes, and keep Python dependencies isolated in virtual environments.

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/jpke/cursor-vibe-coding-template/development
Clone the repo
git clone --depth 1 https://github.com/jpke/cursor-vibe-coding-template

Made for: Cursor.

Per session 0 Nothing until a file matches its globs; then the whole rule loads.
When invoked 326 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 $0.00000 $0.00326
Opus 5 $0.00000 $0.00163
Sonnet 5 $0.00000 $0.00065
Haiku 4.5 $0.00000 $0.00033

Measured yesterday against content hash d93928d67868, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

development 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 yesterday.

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/development.mdc · 19 lines

What it actually says

Frontend Development

  • MVP Development Workflow:
    • Start with HTML: Every application MVP, regardless of its final platform (e.g., mobile app), should begin as a basic HTML page. This enables rapid prototyping and iteration.
    • Styling Guidelines: If you provide a design.json file, I will use it as the primary guideline for all styling and visual design choices.

Testing Strategy

  • Test-Driven Development: Adopt a TDD approach where possible. At a minimum, ensure that unit tests are created or updated for any new or modified code.
  • Test Completion: All tests must be passing before a coding task is considered complete.
  • Test Output: All test reports, artifacts, and error logs must be output to a common tests_output/ directory at the project root.

Python Environment Management

  • Virtual Environments: Always use a virtual environment (venv) when running Python scripts. Check for an existing venv in the current or parent directories before creating a new one. Activate the venv before installing packages or executing scripts.
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. yesterday First seen · 19 lines · 0 tokens per session scan A d93928d67868

Subscribe to this mod's changes

development is a cursor rule published in the GitHub repository jpke/cursor-vibe-coding-template (16 stars, last pushed 1y ago), licensed MIT. It costs nothing until one of its globs matches a file; then it loads 326 tokens. 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.