The example env file matches what the code reads

Every variable the code reads should be documented, and every documented variable should be one the code reads.

Why it is a rule

The example file is the only description of what a deployment must supply, and nothing links it to the code, so it drifts in both directions. An undocumented variable is one a production deployment silently runs without. A documented variable nothing reads is one operators keep setting for no reason.

What is expected

Add the variable with a comment describing what it does and its default. A live NAME=value, a commented # NAME=value, or a name leading an aligned comment table all count as documented.

What counts as a read

Direct property and index access on process.env and import.meta.env, Deno.env.get(...) and Bun.env.*, helper calls like envNumber("NAME"), and destructuring. const { API_URL, PORT = "3000" } = process.env counts each ALL_CAPS name it binds, renames included.

Limits

Matching is textual, so a name assembled at runtime from a prefix is missed. Writing variable names out in full keeps this rule working. Variables consumed outside the scanned sources, by a compose file or a container entrypoint, belong in the externallyConsumed option.