Build remote exec env from exec-server policy (#17216)

## Summary
- add an exec-server `envPolicy` field; when present, the server starts
from its own process env and applies the shell environment policy there
- keep `env` as the exact environment for local/embedded starts, but
make it an overlay for remote unified-exec starts
- move the shell-environment-policy builder into `codex-config` so Core
and exec-server share the inherit/filter/set/include behavior
- overlay only runtime/sandbox/network deltas from Core onto the
exec-server-derived env

## Why
Remote unified exec was materializing the shell env inside Core and
forwarding the whole map to exec-server, so remote processes could
inherit the orchestrator machine's `HOME`, `PATH`, etc. This keeps the
base env on the executor while preserving Core-owned runtime additions
like `CODEX_THREAD_ID`, unified-exec defaults, network proxy env, and
sandbox marker env.

## Validation
- `just fmt`
- `git diff --check`
- `cargo test -p codex-exec-server --lib`
- `cargo test -p codex-core --lib unified_exec::process_manager::tests`
- `cargo test -p codex-core --lib exec_env::tests`
- `cargo test -p codex-core --lib exec_env_tests` (compile-only; filter
matched 0 tests)
- `cargo test -p codex-config --lib shell_environment` (compile-only;
filter matched 0 tests)
- `just bazel-lock-update`

## Known local validation issue
- `just bazel-lock-check` is not runnable in this checkout: it invokes
`./scripts/check-module-bazel-lock.sh`, which is missing.

---------

Co-authored-by: Codex <noreply@openai.com>
Co-authored-by: pakrym-oai <pakrym@openai.com>

codex-rs/exec-server/src/environment.rs

@@ -343,6 +343,7 @@ mod tests {
                 process_id: ProcessId::from("default-env-proc"),
                 argv: vec!["true".to_string()],
                 cwd: std::env::current_dir().expect("read current dir"),
+                env_policy: None,
                 env: Default::default(),
                 tty: false,
                 arg0: None,

codex-rs/exec-server/src/lib.rs

@@ -42,6 +42,7 @@ pub use process::ExecProcess;
 pub use process::StartedExecProcess;
 pub use process_id::ProcessId;
 pub use protocol::ExecClosedNotification;
+pub use protocol::ExecEnvPolicy;
 pub use protocol::ExecExitedNotification;
 pub use protocol::ExecOutputDeltaNotification;
 pub use protocol::ExecOutputStream;

codex-rs/exec-server/src/local_process.rs

@@ -5,6 +5,9 @@ use std::time::Duration;
 
 use async_trait::async_trait;
 use codex_app_server_protocol::JSONRPCErrorError;
+use codex_config::shell_environment;
+use codex_config::types::EnvironmentVariablePattern;
+use codex_config::types::ShellEnvironmentPolicy;
 use codex_utils_pty::ExecCommandSession;
 use codex_utils_pty::TerminalSize;
 use tokio::sync::Mutex;
@@ -19,6 +22,7 @@ use crate::ProcessId;
 use crate::StartedExecProcess;
 use crate::protocol::EXEC_CLOSED_METHOD;
 use crate::protocol::ExecClosedNotification;
+use crate::protocol::ExecEnvPolicy;
 use crate::protocol::ExecExitedNotification;
 use crate::protocol::ExecOutputDeltaNotification;
 use crate::protocol::ExecOutputStream;
@@ -150,12 +154,13 @@ impl LocalProcess {
             process_map.insert(process_id.clone(), ProcessEntry::Starting);
         }
 
+        let env = child_env(&params);
         let spawned_result = if params.tty {
             codex_utils_pty::spawn_pty_process(
                 program,
                 args,
                 params.cwd.as_path(),
-                &params.env,
+                &env,
                 &params.arg0,
                 TerminalSize::default(),
             )
@@ -165,7 +170,7 @@ impl LocalProcess {
                 program,
                 args,
                 params.cwd.as_path(),
-                &params.env,
+                &env,
                 &params.arg0,
             )
             .await
@@ -375,6 +380,36 @@ impl LocalProcess {
     }
 }
 
+fn child_env(params: &ExecParams) -> HashMap<String, String> {
+    let Some(env_policy) = &params.env_policy else {
+        return params.env.clone();
+    };
+
+    let policy = shell_environment_policy(env_policy);
+    let mut env = shell_environment::create_env(&policy, /*thread_id*/ None);
+    env.extend(params.env.clone());
+    env
+}
+
+fn shell_environment_policy(env_policy: &ExecEnvPolicy) -> ShellEnvironmentPolicy {
+    ShellEnvironmentPolicy {
+        inherit: env_policy.inherit.clone(),
+        ignore_default_excludes: env_policy.ignore_default_excludes,
+        exclude: env_policy
+            .exclude
+            .iter()
+            .map(|pattern| EnvironmentVariablePattern::new_case_insensitive(pattern))
+            .collect(),
+        r#set: env_policy.r#set.clone(),
+        include_only: env_policy
+            .include_only
+            .iter()
+            .map(|pattern| EnvironmentVariablePattern::new_case_insensitive(pattern))
+            .collect(),
+        use_profile: false,
+    }
+}
+
 #[async_trait]
 impl ExecBackend for LocalProcess {
     async fn start(&self, params: ExecParams) -> Result<StartedExecProcess, ExecServerError> {
@@ -618,3 +653,56 @@ fn notification_sender(inner: &Inner) -> Option<RpcNotificationSender> {
         .unwrap_or_else(std::sync::PoisonError::into_inner)
         .clone()
 }
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use codex_config::types::ShellEnvironmentPolicyInherit;
+
+    fn test_exec_params(env: HashMap<String, String>) -> ExecParams {
+        ExecParams {
+            process_id: ProcessId::from("env-test"),
+            argv: vec!["true".to_string()],
+            cwd: std::path::PathBuf::from("/tmp"),
+            env_policy: None,
+            env,
+            tty: false,
+            arg0: None,
+        }
+    }
+
+    #[test]
+    fn child_env_defaults_to_exact_env() {
+        let params = test_exec_params(HashMap::from([("ONLY_THIS".to_string(), "1".to_string())]));
+
+        assert_eq!(
+            child_env(&params),
+            HashMap::from([("ONLY_THIS".to_string(), "1".to_string())])
+        );
+    }
+
+    #[test]
+    fn child_env_applies_policy_then_overlay() {
+        let mut params = test_exec_params(HashMap::from([
+            ("OVERLAY".to_string(), "overlay".to_string()),
+            ("POLICY_SET".to_string(), "overlay-wins".to_string()),
+        ]));
+        params.env_policy = Some(ExecEnvPolicy {
+            inherit: ShellEnvironmentPolicyInherit::None,
+            ignore_default_excludes: true,
+            exclude: Vec::new(),
+            r#set: HashMap::from([("POLICY_SET".to_string(), "policy".to_string())]),
+            include_only: Vec::new(),
+        });
+
+        let mut expected = HashMap::from([
+            ("OVERLAY".to_string(), "overlay".to_string()),
+            ("POLICY_SET".to_string(), "overlay-wins".to_string()),
+        ]);
+        if cfg!(target_os = "windows") {
+            expected.insert("PATHEXT".to_string(), ".COM;.EXE;.BAT;.CMD".to_string());
+        }
+
+        assert_eq!(child_env(&params), expected);
+    }
+}

codex-rs/exec-server/src/protocol.rs

@@ -3,6 +3,7 @@ use std::path::PathBuf;
 
 use crate::FileSystemSandboxContext;
 use base64::engine::general_purpose::STANDARD as BASE64_STANDARD;
+use codex_config::types::ShellEnvironmentPolicyInherit;
 use codex_utils_absolute_path::AbsolutePathBuf;
 use serde::Deserialize;
 use serde::Serialize;
@@ -64,11 +65,23 @@ pub struct ExecParams {
     pub process_id: ProcessId,
     pub argv: Vec<String>,
     pub cwd: PathBuf,
+    #[serde(default)]
+    pub env_policy: Option<ExecEnvPolicy>,
     pub env: HashMap<String, String>,
     pub tty: bool,
     pub arg0: Option<String>,
 }
 
+#[derive(Debug, Clone, PartialEq, Eq, Serialize, Deserialize)]
+#[serde(rename_all = "camelCase")]
+pub struct ExecEnvPolicy {
+    pub inherit: ShellEnvironmentPolicyInherit,
+    pub ignore_default_excludes: bool,
+    pub exclude: Vec<String>,
+    pub r#set: HashMap<String, String>,
+    pub include_only: Vec<String>,
+}
+
 #[derive(Debug, Clone, PartialEq, Eq, Serialize, Deserialize)]
 #[serde(rename_all = "camelCase")]
 pub struct ExecResponse {

codex-rs/exec-server/src/server/handler/tests.rs

@@ -27,6 +27,7 @@ fn exec_params_with_argv(process_id: &str, argv: Vec<String>) -> ExecParams {
         process_id: ProcessId::from(process_id),
         argv,
         cwd: std::env::current_dir().expect("cwd"),
+        env_policy: None,
         env: inherited_path_env(),
         tty: false,
         arg0: None,

codex-rs/exec-server/src/server/processor.rs

@@ -390,6 +390,7 @@ mod tests {
             process_id,
             argv: sleep_then_print_argv(),
             cwd: std::env::current_dir().expect("cwd"),
+            env_policy: None,
             env,
             tty: false,
             arg0: None,