Environment variable works locally but not in release: check precedence and secret names

When an environment variable works locally but not in a release, check name spelling, load order, runtime scope, secret store mapping, and fallback values before changing application logic.

Configuration bugs often look like code bugs because the failing value is invisible. A local `.env` file may load before a default, while the release runtime reads from a secret store, platform setting, container variable, or build-time value. The same name can exist in several places with different values. The application may also read the variable during build, while the team changes it only at runtime.

A useful debug note avoids printing secrets. It records variable names, whether each one is present, which source supplied it, when it is read, and whether the fallback branch was used. For example, log “PAYMENT_MODE present from runtime config” rather than the value. If two names differ by a prefix or environment suffix, record both names and the selected one.

Precedence matters. Local files, shell exports, container env, platform secrets, build arguments, and framework config can override each other. A release can fail because the correct value exists but loses to an older default. It can also fail because the code reads a variable in the server process while the developer checks a client bundle setting.

The practical test is to build a small configuration report that says which source won without exposing the secret. If the report differs between local and release, fix the configuration path before touching feature code.

Environment variable works locally but not in release: check precedence and secret names

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