typescript-patterns

typescript-patterns is a cursor rule for Cursor from prisma/orm. It costs 0 tokens per session (465 once invoked), scanned A, original, Apache-2.0.

A collection of TypeScript and architecture rules for a specific codebase. It covers interfaces, factory functions, type predicates, generic parameters, and limits on unsafe casts.

In plain words
What is it for?
It guides TypeScript design, object construction, type narrowing, generic definitions, and test-only exceptions.
Why use it?
It gives contributors consistent ways to structure code and keeps unsafe type workarounds out of production code.

Cursor rule for Cursor ✓ vendor

Written for Cursor: a Cursor rule (.mdc). Also seen: installed under .agents/ (shared by several agents).

Good fit It guides TypeScript design, object construction, type narrowing, generic definitions, and test-only exceptions.

Compare 6 cursor rules from other repositories ↓
Install with agentmods
npx agentmods add rules/prisma/orm/typescript-patterns
About the project

Prisma ORM is a Node.js and TypeScript database toolkit that lets applications work with databases through a programming interface instead of writing every query directly in SQL. Developers use it with databases including PostgreSQL, MySQL, MariaDB, SQL Server, SQLite, MongoDB, and CockroachDB. The catalogue add-ons provide agent rules, skills, hooks, agents, and other workflows for using Prisma.

prisma/orm · 47,608 stars · on GitHub · prisma.io

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/prisma/orm

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 typescript-patterns

README.md
[![agentmods](https://agentmods.dev/badge/rules/prisma/orm/typescript-patterns.svg)](https://agentmods.dev/rules/prisma/orm/typescript-patterns)
Your own site
<a href="https://agentmods.dev/rules/prisma/orm/typescript-patterns"><img src="https://agentmods.dev/badge/rules/prisma/orm/typescript-patterns.svg" alt="Measured on agentmods" height="20"></a>
Per session 0 Nothing until a file matches its globs; then the whole rule loads.
When invoked 465 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 $0.00000 $0.00465
Opus 5 $0.00000 $0.00233
Sonnet 5 $0.00000 $0.00093
Haiku 4.5 $0.00000 $0.00047

Measured 4d ago against content hash 44c60e2769f8, method: parsed. Prices are Anthropic first-party input rates as of 2026-09-07, from the pricing page.

Security

Grade A, and why

typescript-patterns 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 4d 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.

.agents/rules/typescript-patterns.mdc · 32 lines

What it actually says

TypeScript and Architecture Patterns

This rulecard is intentionally short. For deeper examples, see docs/reference/typescript-patterns.md.

Focused rulecards

  • .cursor/rules/generic-parameters.mdc — Generic parameter defaults
  • .cursor/rules/interface-factory-pattern.mdc — Interface-based design + factory functions
  • .cursor/rules/type-predicates.mdc — Replace blind casts with type predicates
  • .cursor/rules/test-mocking-patterns.mdc — Type assertions and mocking patterns in tests

Quick reminders

  • No blind casts in production: as unknown as X is forbidden outside tests. Prefer type predicates or fix the type surface.
  • Export interfaces; construct via factories: keep classes as private implementation details.
  • No generic defaults unless meaningful: defaults are semantics, not “flexibility”.
  • Test-only escapes: @ts-expect-error and double casts are acceptable only in test files, with a short explanation.
  • Key id-like string parameters on the map they come from: a Record<string, string> constraint widens 'pg/int8@1' to string; keyof CT & string preserves the literal and gives completions. Reach for the keyed union whenever a string is semantically an id from a known map.
  • ReturnType of an overloaded function resolves to the last overload. Adding a new last overload, or reordering the existing ones so a different signature ends up last, silently retypes every ReturnType<typeof fn> consumer; an overload inserted earlier leaves them alone. Order overloads most-specific first and most general last, and pin the inferred type with a type test so a change to the last signature fails loudly.
  • .cursor/rules/no-inline-imports.mdc
  • .cursor/rules/object-hasown.mdc
  • .cursor/rules/prefer-assertions-over-defensive-checks.mdc
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. 4d ago First seen · 32 lines · 0 tokens per session scan A 44c60e2769f8

Subscribe to this mod's changes

typescript-patterns is a cursor rule published in the GitHub repository prisma/orm (47,608 stars, last pushed 4d ago), licensed Apache-2.0. It costs nothing until one of its globs matches a file; then it loads 465 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 2026-09-03.