Changelog - 2026-08-22

Logger color follows the environment

Behavior ChangeEnhancement

In one line. Console log lines are colorized in development and plain everywhere else.

What changed

• Color is now a decision, not a constant. The console transport used to call winston's colorizer unconditionally in text format. It now asks resolveLoggerColorize() first.
• APP_ENV_LOGGER_COLOR is the override. Set it to true or false to decide for yourself, in any environment.
• NO_COLOR is honored. The no-color.org convention, which most CLI tools already follow.
• ICustomLoggerOptions gained colorize. An application building its own winston logger can pass the decision in directly.

The first rule that matches wins:

Rule	Result
APP_ENV_LOGGER_COLOR is set	That value
NO_COLOR is set and non-empty	Off
NODE_ENV is local, debug, development, dev or sit - or unset	On
Anything else, including production, staging, uat and unrecognized names	Off

That last row is the same fail-closed boundary the error sanitizer draws. Color is a terminal affordance for our own engineers; every other environment ships its lines to a file or an aggregator, where an escape code is noise every grep has to strip.

Who is affected

• Anyone running with NODE_ENV=production, staging or uat. Console lines lose their color. Nothing else about them changes - same timestamp, same label, same message.
• Anyone running in development. Nothing changes.
• Applications on the pino provider. The rule is a veto only. When it allows color, pino-pretty still applies its own terminal detection, so piping to a file stays clean.
• File and UDP transports. Untouched. They never colorized, in any environment.

If you want the color back

APP_ENV_LOGGER_COLOR=true

That works in any environment, and it beats NO_COLOR.

See Logger reference - Color for the full rules.