pig uses environment variables in three ways:

• Variables such as PIG_OFFLINE configure the pig process.
• pig sets process markers so child processes can identify pig as the launching agent.
• Commands run by the LLM-callable shell tools receive PIG_* variables describing the current session.

Provider API-key variables are documented separately in Provider Authentication.

bin/pig sets two process markers at startup, so they cover every mode, RPC included:

• AI_AGENT=pig is a generic marker that lets tooling identify pig as the agent that launched the process.
• PIG_CODING_AGENT=true is pig-specific and lets child processes detect that they run inside pig.

Child processes inherit both markers. They are not session-specific and are not set automatically when pig is embedded through the SDK.

Commands run by the bash and powershell tools receive the current pig session state:

Variable	Description
PIG_SESSION_ID	Current session ID
PIG_SESSION_FILE	Absolute path to the current session JSONL file; unset for --no-session sessions, which still have an ID
PIG_PROVIDER	Currently selected model provider
PIG_MODEL	Currently selected model ID
PIG_REASONING_LEVEL	Current effective reasoning level: off, minimal, low, medium, high, xhigh, or max

A variable whose value is unknown is left unset rather than set empty, and values inherited from a parent pig are removed first. The values are resolved when each command starts. Switching models or changing the reasoning level therefore affects the next shell command without restarting pig. PIG_PROVIDER and PIG_MODEL identify the selected pig model, not a different upstream model that a router may choose internally.

When asked which model or provider is running, inspect these variables instead of inferring the answer from the system prompt:

printf '%s/%s\n' "$PIG_PROVIDER" "$PIG_MODEL"
printf 'reasoning=%s session=%s\n' "$PIG_REASONING_LEVEL" "$PIG_SESSION_ID"

The session file can be inspected directly when the session is persistent:

if [ -n "$PIG_SESSION_FILE" ]; then
  tail -n 1 "$PIG_SESSION_FILE"
fi

These variables are injected into the LLM-callable bash and powershell tools. They are not injected into user-entered ! or !! commands.

Pig\CodingAgent\Tools\BashTool and PowerShellTool take the session environment as a closure, sessionEnvironment, that answers a SessionEnvironment when each command starts. pig's own bash and powershell tools are given one; a shell tool an extension builds gets the session variables only if it passes one too. Injection happens before spawnHook, so a hook receives the variables in the SpawnContext's env:

use Pig\CodingAgent\Tools\BashTool;
use Pig\CodingAgent\Tools\SessionEnvironment;
use Pig\CodingAgent\Tools\SpawnContext;

$bashTool = new BashTool(
    $cwd,
    sessionEnvironment: fn (): ?SessionEnvironment => $ctx->session !== null ? SessionEnvironment::of($ctx->session) : null,
    spawnHook: fn (SpawnContext $spawn): SpawnContext => $spawn->withEnv([...$spawn->env, 'CI' => '1']),
);

Disable session metadata independently of the spawn hook:

$powershellTool = new PowerShellTool(
    $cwd,
    exposeSessionEnvironment: false,
    spawnHook: fn (SpawnContext $spawn): SpawnContext => $spawn,
);

When disabled, pig removes inherited values for these variables so nested pig processes do not expose stale parent-session metadata. BashTool also takes commandPrefix and shellPath.

These variables are read by pig itself:

Variable	Description
PIG_CODING_AGENT_DIR	Override the agent directory; default is ~/.pig/agent. A leading ~ is expanded
PIG_CODING_AGENT_SESSION_DIR	Override session storage; overridden by --session-dir, and overrides the sessionDir setting
PI_CODING_AGENT_DIR, PI_HOME	Where pi's own directory is (default ~/.pi/agent), whose auth.json and sessions pig shares
PIG_PACKAGE_DIR	Override the package directory (where CHANGELOG.md is read), useful for Nix/Guix store paths
PIG_OFFLINE	1, true, or yes disables startup network activity, including model catalog refreshes and package installs, and refuses /bug uploads; --offline sets it
PIG_SKIP_VERSION_CHECK	Any non-empty value disables the Packagist latest-version request; --offline sets it
PIG_THEME	Initial theme for this run, like --use-theme; --use-theme wins
PIG_TELEMETRY	Override enableInstallTelemetry (the provider attribution headers): 1/true/yes turns them on, anything else off
PIG_CACHE_RETENTION	Set to long for extended provider prompt caching where supported
PIG_SHARE_VIEWER_URL	Override the viewer base URL /share prints (default https://pigagent.dev/session/)
PIG_OAUTH_CALLBACK_HOST	Address the OpenAI Codex sign-in callback server binds to (default 127.0.0.1); the redirect still names localhost
PIG_HARDWARE_CURSOR	Set to 1 to show the hardware cursor when the showHardwareCursor setting is unset; see Terminal setup
PIG_CLEAR_ON_SHRINK	Set to 1 to clear empty rows when the rendered content shrinks, when the terminal.clearOnShrink setting is unset
PIG_PROGRAM_STATUS	1 or 0 skips the OSC 7501 program-status query and assumes the terminal does or does not support it
PIG_HYPERLINKS	Override OSC 8 hyperlink detection with 1, 0, or auto
PIG_IMAGE_PROTOCOL	Override inline image detection with kitty, iterm2, none, or auto
PIG_TRUE_COLOR	Override truecolor detection with 1, 0, or auto
PIG_TUI_ESC_TIMEOUT	How long to wait after a lone ESC before treating it as Escape, in milliseconds; defaults to 100 over SSH and 10 otherwise. Increase if Alt-key input is misread as Escape
PIG_TUI_WRITE_LOG	Append every byte written to the terminal to this file; a directory gets one tui-<timestamp>-<pid>.log file per run
PIG_LOG_LEVEL (or LOG_LEVEL)	Log level for pig's own log: info, debug, or verbose
PIG_LOG_KEEP_DAYS (or LOG_KEEP_DAYS)	Days of log files to keep
PIG_TIMING	1 prints startup timings
VISUAL, EDITOR	External editor fallback when externalEditor is unset
https_proxy, HTTPS_PROXY, http_proxy, HTTP_PROXY	Proxy for outbound requests: HTTPS requests use https_proxy, then HTTPS_PROXY, then the HTTP proxy; HTTP requests use http_proxy, then HTTP_PROXY. ALL_PROXY is not read
no_proxy, NO_PROXY	Hosts reached directly; *.example.com and .example.com forms match subdomains
COMPOSER_BINARY	The composer executable pig update uses

Bundled extensions read their own variables: LLAMA_BASE_URL and LLAMA_API_KEY (llama.cpp router), ANTIGRAVITY_CLIENT_ID and ANTIGRAVITY_CLIENT_SECRET (pig-antigravity), CHROME_PATH (pig-web-search), and ADB_PATH (pig-android-use).

pig reads no PI_* fallback for its own variables, and does not read PIG_MODEL, PIG_PROVIDER, PIG_THINKING, PIG_TUI_MODE, or PIG_RADIUS_GATEWAY; choose a model with --model or the settings instead. PIG_MODEL and PIG_PROVIDER are only set for shell tool commands, as described above.

Provider credentials such as ANTHROPIC_API_KEY, OPENAI_API_KEY, and cloud-provider configuration are listed in Provider Authentication.