required-key-undefined-fields

required-key-undefined-fields is a cursor rule for Codex from prisma/orm. It costs 0 tokens per session (264 once invoked), scanned A, original, Apache-2.0.

A TypeScript coding rule for representing possibly absent fields in internal input objects. It requires the field to be present with an explicit `undefined` value.

In plain words
What is it for?
It guides the design and construction of internal TypeScript input types, intermediate objects, and schema or entity nodes.
Why use it?
It prevents existing code from silently missing a newly added field during construction. It applies to internal types, not user-facing options.

Cursor rule for Codex

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 · 47,601 stars · on GitHub

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/prisma/orm/required-key-undefined-fields
Clone the repo
git clone --depth 1 https://github.com/prisma/orm

Made for: Codex.

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 required-key-undefined-fields

README.md
[![agentmods](https://agentmods.dev/badge/rules/prisma/orm/required-key-undefined-fields.svg)](https://agentmods.dev/rules/prisma/orm/required-key-undefined-fields)
Your own site
<a href="https://agentmods.dev/rules/prisma/orm/required-key-undefined-fields"><img src="https://agentmods.dev/badge/rules/prisma/orm/required-key-undefined-fields.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 264 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 $0.00264
Opus 5 $0.00000 $0.00132
Sonnet 5 $0.00000 $0.00053
Haiku 4.5 $0.00000 $0.00026

Measured yesterday against content hash bf6b7b27cb47, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

required-key-undefined-fields 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.

.agents/rules/required-key-undefined-fields.mdc · 28 lines

What it actually says

Required keys typed | undefined for internal input types

On internal construction-input types (IR node inputs, producer→builder handoff types), a value that may legitimately be absent is a required key typed | undefined, not an optional key:

// Do
readonly withCheck: string | undefined;

// Don't
readonly withCheck?: string;

Every construction site then states the absence explicitly (withCheck: undefined) instead of silently omitting the key — an omitted field is a compile error, so a new field can never be silently skipped by an existing caller.

Scope

  • Applies to internal inputs: *IRInput, *SchemaNodeInput, entity constructor inputs, producer→builder IR types.
  • Does NOT apply to user-facing authoring options or machine-rendered literals (e.g. generated migration source), where omission is the natural spelling — type those with optional keys.
  • Do not restate this convention in doc comments on each type; the declaration (x: T | undefined) already says it.

Related: use-if-defined.mdc (spreading optional values into such objects).

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 · 28 lines · 0 tokens per session scan A bf6b7b27cb47

Subscribe to this mod's changes

required-key-undefined-fields is a cursor rule published in the GitHub repository prisma/orm (47,601 stars, last pushed 2d ago), licensed Apache-2.0. It costs nothing until one of its globs matches a file; then it loads 264 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.