env-validation-gate

A startup check for application environment settings, using a Zod schema to validate required values and provide them through a typed interface.

In plain words
What is it for?
Use it to define required environment variables, separate client and server settings, add a startup validation hook, and prevent direct process.env reads elsewhere.
Why use it?
It exposes missing or empty deployment settings when the app starts instead of allowing a hidden configuration mistake to cause failures later.

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/mission69b/t2000/env-validation-gate
Clone the repo
git clone --depth 1 https://github.com/mission69b/t2000

Made for: Cursor.

Per session 292 This file is loaded in full into every session.
When invoked 292 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 $0.00292 $0.00292
Opus 5 $0.00146 $0.00146
Sonnet 5 $0.00058 $0.00058
Haiku 4.5 $0.00029 $0.00029

Measured 2d ago against content hash 40d8dc876942, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

env-validation-gate 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/env-validation-gate.mdc · 24 lines

What it actually says

Env Validation Gate → .claude/skills/t2000-env-gate/SKILL.md

The invariant: every app with ≥1 REQUIRED env var validates at boot via a Zod schema and exposes values through a typed env proxy. Raw process.env.X reads outside the env module are banned (only NODE_ENV and NEXT_RUNTIME are exempt), and process.env.X || 'default' is banned outright — it masks a misconfig forever. Apps with ZERO required vars may validate inline instead.

Why: an empty-string var in the Vercel UI silently degraded production for ~4 days and surfaced three layers below the actual cause.

Read the full pattern before editing any env code: .claude/skills/t2000-env-gate/SKILL.md — the Zod schema shape, the client/server split, the boot hook, and the reference implementation at audric/apps/web-v3/lib/env.ts.

(Content moved there 2026-07-24 — do not re-inline it here; this file is a pointer so Cursor and Claude Code cannot drift.)

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 · 24 lines · 292 tokens per session scan A 40d8dc876942

Subscribe to this mod's changes

env-validation-gate is a cursor rule published in the GitHub repository mission69b/t2000 (23 stars, last pushed 2d ago), licensed MIT. It adds 292 tokens to every session, about $0.0015 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.