diff --git a/eden/scm/edenscm/ext/tweakdefaults.py b/eden/scm/edenscm/ext/tweakdefaults.py
index 726cc123e2..01a843b13b 100644
--- a/eden/scm/edenscm/ext/tweakdefaults.py
+++ b/eden/scm/edenscm/ext/tweakdefaults.py
@@ -671,7 +671,7 @@ def statuscmd(orig, ui, repo, *pats, **opts):
             message = _("--root-relative not supported with patterns")
             hint = _("run from the repo root instead")
             raise error.Abort(message, hint=hint)
-    elif encoding.environ.get("HGPLAIN"):  # don't break automation
+    elif ui.plain():
         pass
     # Here's an ugly hack! If users are passing "re:" to make status relative,
     # hgwatchman will never refresh the full state and status will become and
diff --git a/eden/scm/edenscm/i18n.py b/eden/scm/edenscm/i18n.py
index 6700a6ba8b..cf27dc8237 100644
--- a/eden/scm/edenscm/i18n.py
+++ b/eden/scm/edenscm/i18n.py
@@ -17,6 +17,8 @@ import locale
 import os
 import sys
 
+import bindings
+
 from . import encoding, identity, pycompat
 
 
@@ -146,9 +148,12 @@ _plain = True
 
 
 def _getplain():
-    if "HGPLAIN" not in encoding.environ and "HGPLAINEXCEPT" not in encoding.environ:
+    plain = bindings.identity.envvar("PLAIN")
+    plainexcept = bindings.identity.envvar("PLAINEXCEPT")
+
+    if plain is None and plainexcept is None:
         return False
-    exceptions = encoding.environ.get("HGPLAINEXCEPT", "").strip().split(",")
+    exceptions = (plainexcept or "").strip().split(",")
     return "i18n" not in exceptions
 
 
diff --git a/eden/scm/edenscm/ui.py b/eden/scm/edenscm/ui.py
index 6f47d1854e..2e700fc58a 100644
--- a/eden/scm/edenscm/ui.py
+++ b/eden/scm/edenscm/ui.py
@@ -558,11 +558,13 @@ class ui(object):
         - False if feature is disabled by default and not included in HGPLAIN
         - True otherwise
         """
-        if "HGPLAIN" not in os.environ and "HGPLAINEXCEPT" not in os.environ:
+        plain = bindings.identity.envvar("PLAIN")
+        plainexcept = bindings.identity.envvar("PLAINEXCEPT")
+        if plain is None and plainexcept is None:
             return False
-        exceptions = encoding.environ.get("HGPLAINEXCEPT", "").strip().split(",")
+        exceptions = (plainexcept or "").strip().split(",")
         # TODO: add support for HGPLAIN=+feature,-feature syntax
-        if "+strictflags" not in encoding.environ.get("HGPLAIN", "").split(","):
+        if "+strictflags" not in (plain or "").split(","):
             exceptions.append("strictflags")
         if feature and exceptions:
             return feature not in exceptions
diff --git a/eden/scm/edenscmnative/bindings/modules/pyidentity/src/lib.rs b/eden/scm/edenscmnative/bindings/modules/pyidentity/src/lib.rs
index 70db9f6e52..f5bf8f8ea7 100644
--- a/eden/scm/edenscmnative/bindings/modules/pyidentity/src/lib.rs
+++ b/eden/scm/edenscmnative/bindings/modules/pyidentity/src/lib.rs
@@ -21,6 +21,7 @@ pub fn init_module(py: Python, package: &str) -> PyResult<PyModule> {
     m.add(py, "sniffenv", py_fn!(py, sniff_env()))?;
     m.add(py, "sniffroot", py_fn!(py, sniff_root(path: PyPathBuf)))?;
     m.add(py, "sniffdir", py_fn!(py, sniff_dir(path: PyPathBuf)))?;
+    m.add(py, "envvar", py_fn!(py, try_env_var(suffix: PyString)))?;
 
     Ok(m)
 }
@@ -53,3 +54,9 @@ fn sniff_dir(py: Python, path: PyPathBuf) -> PyResult<Option<identity>> {
         Some(ident) => Some(identity::create_instance(py, ident)?),
     })
 }
+
+fn try_env_var(py: Python, suffix: PyString) -> PyResult<Option<String>> {
+    rsident::env_var(suffix.to_string(py)?.as_ref())
+        .transpose()
+        .map_pyerr(py)
+}
diff --git a/eden/scm/lib/commitcloudsubscriber/Cargo.toml b/eden/scm/lib/commitcloudsubscriber/Cargo.toml
index 37b91e52f8..b40108d606 100644
--- a/eden/scm/lib/commitcloudsubscriber/Cargo.toml
+++ b/eden/scm/lib/commitcloudsubscriber/Cargo.toml
@@ -22,6 +22,7 @@ anyhow = "1.0.65"
 eventsource = "0.5"
 filetime = "0.2.9"
 hostcaps = { version = "0.1.0", git = "https://github.com/facebookexperimental/rust-shed.git", branch = "main" }
+identity = { version = "0.1.0", path = "../identity" }
 lazy_static = "1.4"
 log = { version = "0.4.14", features = ["kv_unstable", "kv_unstable_std"] }
 regex = "1.5.4"
diff --git a/eden/scm/lib/commitcloudsubscriber/src/action.rs b/eden/scm/lib/commitcloudsubscriber/src/action.rs
index 647a9287e9..55ebe60963 100644
--- a/eden/scm/lib/commitcloudsubscriber/src/action.rs
+++ b/eden/scm/lib/commitcloudsubscriber/src/action.rs
@@ -38,7 +38,7 @@ impl CloudSyncTrigger {
             let now = Instant::now();
             let child = Command::new("hg")
                 .current_dir(&path)
-                .env("HGPLAIN", "hint")
+                .env(identity::try_env_var("PLAIN")?, "hint")
                 .args(vec!["cloud", "sync"])
                 .arg("--check-autosync-enabled")
                 .arg("--use-bgssh")
diff --git a/eden/scm/lib/config/parser/src/hg.rs b/eden/scm/lib/config/parser/src/hg.rs
index 7ac00a0eb0..c90d081643 100644
--- a/eden/scm/lib/config/parser/src/hg.rs
+++ b/eden/scm/lib/config/parser/src/hg.rs
@@ -23,8 +23,7 @@ use std::path::PathBuf;
 use anyhow::Result;
 use configmodel::Config;
 use configmodel::ConfigExt;
-use hgplain::HGPLAIN;
-use hgplain::HGPLAINEXCEPT;
+use hgplain;
 use minibytes::Text;
 use url::Url;
 use util::path::expand_path;
@@ -134,15 +133,9 @@ pub fn load(
 
 impl OptionsHgExt for Options {
     fn process_hgplain(self) -> Self {
-        let plain_set = env::var(HGPLAIN).is_ok();
-        let plain_except = env::var(HGPLAINEXCEPT);
-        if plain_set || plain_except.is_ok() {
+        if hgplain::is_plain(None) {
             let (section_exclude_list, ui_exclude_list) = {
-                let plain_exceptions: HashSet<String> = plain_except
-                    .unwrap_or_else(|_| "".to_string())
-                    .split(',')
-                    .map(|s| s.to_string())
-                    .collect();
+                let plain_exceptions = hgplain::exceptions();
 
                 // [defaults] and [commands] are always excluded.
                 let mut section_exclude_list: HashSet<Text> =
@@ -874,6 +867,9 @@ mod tests {
     use crate::config::tests::write_file;
     use crate::lock_env;
 
+    const HGPLAIN: &str = "HGPLAIN";
+    const HGPLAINEXCEPT: &str = "HGPLAINEXCEPT";
+
     #[test]
     fn test_basic_hgplain() {
         let mut env = lock_env();
diff --git a/eden/scm/lib/identity/src/lib.rs b/eden/scm/lib/identity/src/lib.rs
index 1d8073c13d..9ce9f6afab 100644
--- a/eden/scm/lib/identity/src/lib.rs
+++ b/eden/scm/lib/identity/src/lib.rs
@@ -24,6 +24,8 @@ pub struct Identity {
     dot_dir: &'static str,
     env_prefix: &'static str,
     config_name: &'static str,
+    scripting_env_var: &'static str,
+    scripting_except_env_var: &'static str,
 }
 
 impl Identity {
@@ -47,8 +49,12 @@ impl Identity {
         self.env_prefix
     }
 
-    fn env_var(&self, suffix: &str) -> Option<Result<String, VarError>> {
-        let var_name = format!("{}{}", self.env_prefix, suffix);
+    pub fn env_var(&self, suffix: &str) -> Option<Result<String, VarError>> {
+        let var_name = match suffix {
+            "PLAIN" => self.scripting_env_var.to_string(),
+            "PLAINEXCEPT" => self.scripting_except_env_var.to_string(),
+            _ => format!("{}{}", self.env_prefix, suffix),
+        };
         match std::env::var(var_name) {
             Err(err) if err == VarError::NotPresent => None,
             Err(err) => Some(Err(err)),
@@ -69,6 +75,8 @@ const HG: Identity = Identity {
     dot_dir: ".hg",
     env_prefix: "HG",
     config_name: "hgrc",
+    scripting_env_var: "HGPLAIN",
+    scripting_except_env_var: "HGPLAINEXCEPT",
 };
 
 const SL: Identity = Identity {
@@ -77,6 +85,8 @@ const SL: Identity = Identity {
     dot_dir: ".sl",
     env_prefix: "SL",
     config_name: "slconfig",
+    scripting_env_var: "SL_AUTOMATION",
+    scripting_except_env_var: "SL_AUTOMATION_EXCEPT",
 };
 
 #[cfg(test)]
@@ -86,6 +96,8 @@ const TEST: Identity = Identity {
     dot_dir: ".test",
     env_prefix: "TEST",
     config_name: "testrc",
+    scripting_env_var: "TEST_SCRIPT",
+    scripting_except_env_var: "TEST_SCRIPT_EXCEPT",
 };
 
 #[cfg(all(not(feature = "sl_only"), not(test)))]
@@ -169,12 +181,12 @@ pub fn sniff_root(path: &Path) -> Result<Option<(PathBuf, Identity)>> {
     Ok(None)
 }
 
-fn try_env_var(var_suffix: &str) -> Result<String, VarError> {
+pub fn env_var(var_suffix: &str) -> Option<Result<String, VarError>> {
     let current_id = IDENTITY.read();
 
     // Always prefer current identity.
     if let Some(res) = current_id.env_var(var_suffix) {
-        return res;
+        return Some(res);
     }
 
     // Backwards compat for old env vars.
@@ -184,11 +196,18 @@ fn try_env_var(var_suffix: &str) -> Result<String, VarError> {
         }
 
         if let Some(res) = id.env_var(var_suffix) {
-            return res;
+            return Some(res);
         }
     }
 
-    Err(VarError::NotPresent)
+    None
+}
+
+pub fn try_env_var(var_suffix: &str) -> Result<String, VarError> {
+    match env_var(var_suffix) {
+        Some(result) => result,
+        None => Err(VarError::NotPresent),
+    }
 }
 
 pub fn sniff_env() -> Identity {
diff --git a/eden/scm/lib/util/hgplain/Cargo.toml b/eden/scm/lib/util/hgplain/Cargo.toml
index e11561a559..c1c2f355a3 100644
--- a/eden/scm/lib/util/hgplain/Cargo.toml
+++ b/eden/scm/lib/util/hgplain/Cargo.toml
@@ -5,3 +5,6 @@ name = "hgplain"
 version = "0.1.0"
 authors = ["Facebook Source Control Team <sourcecontrol-dev@fb.com>"]
 edition = "2021"
+
+[dependencies]
+identity = { version = "0.1.0", path = "../../identity" }
diff --git a/eden/scm/lib/util/hgplain/src/lib.rs b/eden/scm/lib/util/hgplain/src/lib.rs
index 503095dc82..b1bd444c90 100644
--- a/eden/scm/lib/util/hgplain/src/lib.rs
+++ b/eden/scm/lib/util/hgplain/src/lib.rs
@@ -5,15 +5,12 @@
  * GNU General Public License version 2.
  */
 
-use std::env;
-
-pub const HGPLAIN: &str = "HGPLAIN";
-pub const HGPLAINEXCEPT: &str = "HGPLAINEXCEPT";
+use std::collections::HashSet;
 
 /// Return whether plain mode is active, similar to python ui.plain().
 pub fn is_plain(feature: Option<&str>) -> bool {
-    let plain = env::var(HGPLAIN);
-    let plain_except = env::var(HGPLAINEXCEPT);
+    let plain = identity::try_env_var("PLAIN");
+    let plain_except = identity::try_env_var("PLAINEXCEPT");
 
     if plain.is_err() && plain_except.is_err() {
         return false;
@@ -28,3 +25,10 @@ pub fn is_plain(feature: Option<&str>) -> bool {
         true
     }
 }
+
+pub fn exceptions() -> HashSet<String> {
+    match identity::try_env_var("PLAINEXCEPT") {
+        Ok(value) => value.split(',').map(|s| s.to_string()).collect(),
+        Err(_) => HashSet::new(),
+    }
+}