Module runner_env 

The environment a native runner starts with, beyond what the daemon has.

A runner inherits the daemon’s environment, and a service’s environment is not a login shell’s. On macOS launchd starts the agent with PATH=/usr/bin:/bin:/usr/sbin:/sbin and no LANG, so a job finds no Homebrew tool (actions/cache falls back from zstd to gzip and never hits), and nothing the operator put in a shell profile reaches it. A classic runner gets those from the .env and .path files its config.sh writes; a just-in-time runner never runs config.sh.

Two things fill the gap, applied to every native runner in this order, each overriding the one before:

1. Platform defaults (platform_defaults): on macOS, Homebrew’s directories ahead of the inherited PATH and a UTF-8 LANG; on Windows, a profile of the runner’s own (USERPROFILE, HOME, APPDATA, LOCALAPPDATA) inside the attempt, so concurrent jobs stop sharing the service account’s ~/.bun, npm cache and pnpm store. Linux has none.
2. The host’s runner.env (RunnerEnv): KEY=VALUE lines in the configuration directory, edited with runner-manager host env. A name set here replaces the platform default of the same name outright.

The per-attempt temporary directory (TMPDIR, TEMP, TMP) is applied last and cannot be overridden, and neither can GitHub’s ACTIONS_RUNNER_INPUT_* inputs, one of which carries the JIT configuration: RESERVED_NAMES and RESERVED_PREFIX.

Not a secret store

The file is plain text in the configuration directory and every runner’s environment can read it back. Nothing here logs or prints a value except host env show, which exists to show them; errors name a line or a variable, never what it was set to.

Structs

Inherited

What the daemon’s own environment holds, as far as the defaults care.

RunnerEnv

The parsed runner.env: ordered, one entry per name.

Enums

RunnerEnvError

Why a runner.env line or assignment was refused, or the file could not be read or written. No variant carries a value.

RunnerPlatform

Which platform’s defaults to compute. A parameter rather than a cfg so that every leg of CI tests every platform’s rules.

Constants

DIRECTORY_VARIABLES

The platform_defaults that name a directory the caller must create. Creating them creates the profile directory above them too.

MACOS_DEFAULT_LANG

The LANG a macOS runner gets when the daemon has none. It is what config.sh would have recorded from a default macOS terminal, and without a UTF-8 locale Ruby, CocoaPods and Python mis-handle non-ASCII text.

MACOS_SYSTEM_PATH

The PATH launchd gives a service, kept behind Homebrew’s directories when the daemon has no PATH of its own.

MACOS_TOOL_DIRECTORIES

macOS directories put ahead of the inherited PATH, when they exist and are not on it already: Apple Silicon Homebrew, then Intel Homebrew.

RESERVED_NAMES

Names runner.env may not set, compared without regard to case: the temporary directory is per attempt, and cleanup and isolation rely on it.

RESERVED_PREFIX

The prefix of every name runner.env may not set: the listener reads each such variable as a command-line input, including the JIT configuration that registers it.

RUNNER_ENV_FILE

The file’s name inside the configuration directory.

RUNNER_HOME_DIR

The directory inside an attempt that is its runner’s profile on Windows.

WINDOWS_PROFILE_VARIABLES

The variables platform_defaults sets on Windows, in order: the profile directory twice, then its roaming and local application data.

Functions

path_in

The runner.env path for a configuration directory.

platform_defaults

The variables platform sets for a runner whose attempt directory is runtime, before runner.env is applied.

runner_environment

The variables a native runner starts with on top of the daemon’s environment, in the order they must be applied: the platform defaults, then file. Applied in order the last value for a name wins, as it does for Command::env, so file overrides a default of the same name.

split_assignment

Splits a NAME=VALUE command-line argument.