chore: refactor exec.rs: create separate seatbelt.rs and spawn.rs files (#1762)

At 550 lines, `exec.rs` was a bit large. In particular, I found it hard
to locate the Seatbelt-related code quickly without a file with
`seatbelt` in the name, so this refactors things so:

- `spawn_command_under_seatbelt()` and dependent code moves to a new
`seatbelt.rs` file
- `spawn_child_async()` and dependent code moves to a new `spawn.rs`
file

codex-rs/cli/src/debug_sandbox.rs

@@ -4,10 +4,10 @@ use codex_common::CliConfigOverrides;
 use codex_core::config::Config;
 use codex_core::config::ConfigOverrides;
 use codex_core::config_types::SandboxMode;
-use codex_core::exec::StdioPolicy;
 use codex_core::exec::spawn_command_under_linux_sandbox;
-use codex_core::exec::spawn_command_under_seatbelt;
 use codex_core::exec_env::create_env;
+use codex_core::seatbelt::spawn_command_under_seatbelt;
+use codex_core::spawn::StdioPolicy;
 
 use crate::LandlockCommand;
 use crate::SeatbeltCommand;

codex-rs/core/src/exec.rs

@@ -6,7 +6,6 @@ use std::io;
 use std::path::Path;
 use std::path::PathBuf;
 use std::process::ExitStatus;
-use std::process::Stdio;
 use std::sync::Arc;
 use std::time::Duration;
 use std::time::Instant;
@@ -15,14 +14,15 @@ use tokio::io::AsyncRead;
 use tokio::io::AsyncReadExt;
 use tokio::io::BufReader;
 use tokio::process::Child;
-use tokio::process::Command;
 use tokio::sync::Notify;
-use tracing::trace;
 
 use crate::error::CodexErr;
 use crate::error::Result;
 use crate::error::SandboxErr;
 use crate::protocol::SandboxPolicy;
+use crate::seatbelt::spawn_command_under_seatbelt;
+use crate::spawn::StdioPolicy;
+use crate::spawn::spawn_child_async;
 
 // Maximum we send for each stream, which is either:
 // - 10KiB OR
@@ -37,24 +37,6 @@ const DEFAULT_TIMEOUT_MS: u64 = 10_000;
 const SIGKILL_CODE: i32 = 9;
 const TIMEOUT_CODE: i32 = 64;
 
-const MACOS_SEATBELT_BASE_POLICY: &str = include_str!("seatbelt_base_policy.sbpl");
-
-/// When working with `sandbox-exec`, only consider `sandbox-exec` in `/usr/bin`
-/// to defend against an attacker trying to inject a malicious version on the
-/// PATH. If /usr/bin/sandbox-exec has been tampered with, then the attacker
-/// already has root access.
-const MACOS_PATH_TO_SEATBELT_EXECUTABLE: &str = "/usr/bin/sandbox-exec";
-
-/// Experimental environment variable that will be set to some non-empty value
-/// if both of the following are true:
-///
-/// 1. The process was spawned by Codex as part of a shell tool call.
-/// 2. SandboxPolicy.has_full_network_access() was false for the tool call.
-///
-/// We may try to have just one environment variable for all sandboxing
-/// attributes, so this may change in the future.
-pub const CODEX_SANDBOX_NETWORK_DISABLED_ENV_VAR: &str = "CODEX_SANDBOX_NETWORK_DISABLED";
-
 #[derive(Debug, Clone)]
 pub struct ExecParams {
     pub command: Vec<String>,
@@ -168,27 +150,6 @@ pub async fn process_exec_tool_call(
     }
 }
 
-pub async fn spawn_command_under_seatbelt(
-    command: Vec<String>,
-    sandbox_policy: &SandboxPolicy,
-    cwd: PathBuf,
-    stdio_policy: StdioPolicy,
-    env: HashMap<String, String>,
-) -> std::io::Result<Child> {
-    let args = create_seatbelt_command_args(command, sandbox_policy, &cwd);
-    let arg0 = None;
-    spawn_child_async(
-        PathBuf::from(MACOS_PATH_TO_SEATBELT_EXECUTABLE),
-        args,
-        arg0,
-        cwd,
-        sandbox_policy,
-        stdio_policy,
-        env,
-    )
-    .await
-}
-
 /// Spawn a shell tool command under the Linux Landlock+seccomp sandbox helper
 /// (codex-linux-sandbox).
 ///
@@ -248,65 +209,6 @@ fn create_linux_sandbox_command_args(
     linux_cmd
 }
 
-fn create_seatbelt_command_args(
-    command: Vec<String>,
-    sandbox_policy: &SandboxPolicy,
-    cwd: &Path,
-) -> Vec<String> {
-    let (file_write_policy, extra_cli_args) = {
-        if sandbox_policy.has_full_disk_write_access() {
-            // Allegedly, this is more permissive than `(allow file-write*)`.
-            (
-                r#"(allow file-write* (regex #"^/"))"#.to_string(),
-                Vec::<String>::new(),
-            )
-        } else {
-            let writable_roots = sandbox_policy.get_writable_roots_with_cwd(cwd);
-            let (writable_folder_policies, cli_args): (Vec<String>, Vec<String>) = writable_roots
-                .iter()
-                .enumerate()
-                .map(|(index, root)| {
-                    let param_name = format!("WRITABLE_ROOT_{index}");
-                    let policy: String = format!("(subpath (param \"{param_name}\"))");
-                    let cli_arg = format!("-D{param_name}={}", root.to_string_lossy());
-                    (policy, cli_arg)
-                })
-                .unzip();
-            if writable_folder_policies.is_empty() {
-                ("".to_string(), Vec::<String>::new())
-            } else {
-                let file_write_policy = format!(
-                    "(allow file-write*\n{}\n)",
-                    writable_folder_policies.join(" ")
-                );
-                (file_write_policy, cli_args)
-            }
-        }
-    };
-
-    let file_read_policy = if sandbox_policy.has_full_disk_read_access() {
-        "; allow read-only file operations\n(allow file-read*)"
-    } else {
-        ""
-    };
-
-    // TODO(mbolin): apply_patch calls must also honor the SandboxPolicy.
-    let network_policy = if sandbox_policy.has_full_network_access() {
-        "(allow network-outbound)\n(allow network-inbound)\n(allow system-socket)"
-    } else {
-        ""
-    };
-
-    let full_policy = format!(
-        "{MACOS_SEATBELT_BASE_POLICY}\n{file_read_policy}\n{file_write_policy}\n{network_policy}"
-    );
-    let mut seatbelt_args: Vec<String> = vec!["-p".to_string(), full_policy];
-    seatbelt_args.extend(extra_cli_args);
-    seatbelt_args.push("--".to_string());
-    seatbelt_args.extend(command);
-    seatbelt_args
-}
-
 #[derive(Debug)]
 pub struct RawExecToolCallOutput {
     pub exit_status: ExitStatus,
@@ -352,90 +254,6 @@ async fn exec(
     consume_truncated_output(child, ctrl_c, timeout_ms).await
 }
 
-#[derive(Debug, Clone, Copy)]
-pub enum StdioPolicy {
-    RedirectForShellTool,
-    Inherit,
-}
-
-/// Spawns the appropriate child process for the ExecParams and SandboxPolicy,
-/// ensuring the args and environment variables used to create the `Command`
-/// (and `Child`) honor the configuration.
-///
-/// For now, we take `SandboxPolicy` as a parameter to spawn_child() because
-/// we need to determine whether to set the
-/// `CODEX_SANDBOX_NETWORK_DISABLED_ENV_VAR` environment variable.
-async fn spawn_child_async(
-    program: PathBuf,
-    args: Vec<String>,
-    #[cfg_attr(not(unix), allow(unused_variables))] arg0: Option<&str>,
-    cwd: PathBuf,
-    sandbox_policy: &SandboxPolicy,
-    stdio_policy: StdioPolicy,
-    env: HashMap<String, String>,
-) -> std::io::Result<Child> {
-    trace!(
-        "spawn_child_async: {program:?} {args:?} {arg0:?} {cwd:?} {sandbox_policy:?} {stdio_policy:?} {env:?}"
-    );
-
-    let mut cmd = Command::new(&program);
-    #[cfg(unix)]
-    cmd.arg0(arg0.map_or_else(|| program.to_string_lossy().to_string(), String::from));
-    cmd.args(args);
-    cmd.current_dir(cwd);
-    cmd.env_clear();
-    cmd.envs(env);
-
-    if !sandbox_policy.has_full_network_access() {
-        cmd.env(CODEX_SANDBOX_NETWORK_DISABLED_ENV_VAR, "1");
-    }
-
-    // If this Codex process dies (including being killed via SIGKILL), we want
-    // any child processes that were spawned as part of a `"shell"` tool call
-    // to also be terminated.
-
-    // This relies on prctl(2), so it only works on Linux.
-    #[cfg(target_os = "linux")]
-    unsafe {
-        cmd.pre_exec(|| {
-            // This prctl call effectively requests, "deliver SIGTERM when my
-            // current parent dies."
-            if libc::prctl(libc::PR_SET_PDEATHSIG, libc::SIGTERM) == -1 {
-                return Err(io::Error::last_os_error());
-            }
-
-            // Though if there was a race condition and this pre_exec() block is
-            // run _after_ the parent (i.e., the Codex process) has already
-            // exited, then the parent is the _init_ process (which will never
-            // die), so we should just terminate the child process now.
-            if libc::getppid() == 1 {
-                libc::raise(libc::SIGTERM);
-            }
-            Ok(())
-        });
-    }
-
-    match stdio_policy {
-        StdioPolicy::RedirectForShellTool => {
-            // Do not create a file descriptor for stdin because otherwise some
-            // commands may hang forever waiting for input. For example, ripgrep has
-            // a heuristic where it may try to read from stdin as explained here:
-            // https://github.com/BurntSushi/ripgrep/blob/e2362d4d5185d02fa857bf381e7bd52e66fafc73/crates/core/flags/hiargs.rs#L1101-L1103
-            cmd.stdin(Stdio::null());
-
-            cmd.stdout(Stdio::piped()).stderr(Stdio::piped());
-        }
-        StdioPolicy::Inherit => {
-            // Inherit stdin, stdout, and stderr from the parent process.
-            cmd.stdin(Stdio::inherit())
-                .stdout(Stdio::inherit())
-                .stderr(Stdio::inherit());
-        }
-    }
-
-    cmd.kill_on_drop(true).spawn()
-}
-
 /// Consumes the output of a child process, truncating it so it is suitable for
 /// use as the output of a `shell` tool call. Also enforces specified timeout.
 pub(crate) async fn consume_truncated_output(

codex-rs/core/src/lib.rs

@@ -39,7 +39,9 @@ mod project_doc;
 pub mod protocol;
 mod rollout;
 mod safety;
+pub mod seatbelt;
 pub mod shell;
+pub mod spawn;
 mod user_notification;
 pub mod util;
 

codex-rs/core/src/seatbelt.rs

@@ -0,0 +1,96 @@
+use std::collections::HashMap;
+use std::path::Path;
+use std::path::PathBuf;
+use tokio::process::Child;
+
+use crate::protocol::SandboxPolicy;
+use crate::spawn::StdioPolicy;
+use crate::spawn::spawn_child_async;
+
+const MACOS_SEATBELT_BASE_POLICY: &str = include_str!("seatbelt_base_policy.sbpl");
+
+/// When working with `sandbox-exec`, only consider `sandbox-exec` in `/usr/bin`
+/// to defend against an attacker trying to inject a malicious version on the
+/// PATH. If /usr/bin/sandbox-exec has been tampered with, then the attacker
+/// already has root access.
+const MACOS_PATH_TO_SEATBELT_EXECUTABLE: &str = "/usr/bin/sandbox-exec";
+
+pub async fn spawn_command_under_seatbelt(
+    command: Vec<String>,
+    sandbox_policy: &SandboxPolicy,
+    cwd: PathBuf,
+    stdio_policy: StdioPolicy,
+    env: HashMap<String, String>,
+) -> std::io::Result<Child> {
+    let args = create_seatbelt_command_args(command, sandbox_policy, &cwd);
+    let arg0 = None;
+    spawn_child_async(
+        PathBuf::from(MACOS_PATH_TO_SEATBELT_EXECUTABLE),
+        args,
+        arg0,
+        cwd,
+        sandbox_policy,
+        stdio_policy,
+        env,
+    )
+    .await
+}
+
+fn create_seatbelt_command_args(
+    command: Vec<String>,
+    sandbox_policy: &SandboxPolicy,
+    cwd: &Path,
+) -> Vec<String> {
+    let (file_write_policy, extra_cli_args) = {
+        if sandbox_policy.has_full_disk_write_access() {
+            // Allegedly, this is more permissive than `(allow file-write*)`.
+            (
+                r#"(allow file-write* (regex #"^/"))"#.to_string(),
+                Vec::<String>::new(),
+            )
+        } else {
+            let writable_roots = sandbox_policy.get_writable_roots_with_cwd(cwd);
+            let (writable_folder_policies, cli_args): (Vec<String>, Vec<String>) = writable_roots
+                .iter()
+                .enumerate()
+                .map(|(index, root)| {
+                    let param_name = format!("WRITABLE_ROOT_{index}");
+                    let policy: String = format!("(subpath (param \"{param_name}\"))");
+                    let cli_arg = format!("-D{param_name}={}", root.to_string_lossy());
+                    (policy, cli_arg)
+                })
+                .unzip();
+            if writable_folder_policies.is_empty() {
+                ("".to_string(), Vec::<String>::new())
+            } else {
+                let file_write_policy = format!(
+                    "(allow file-write*\n{}\n)",
+                    writable_folder_policies.join(" ")
+                );
+                (file_write_policy, cli_args)
+            }
+        }
+    };
+
+    let file_read_policy = if sandbox_policy.has_full_disk_read_access() {
+        "; allow read-only file operations\n(allow file-read*)"
+    } else {
+        ""
+    };
+
+    // TODO(mbolin): apply_patch calls must also honor the SandboxPolicy.
+    let network_policy = if sandbox_policy.has_full_network_access() {
+        "(allow network-outbound)\n(allow network-inbound)\n(allow system-socket)"
+    } else {
+        ""
+    };
+
+    let full_policy = format!(
+        "{MACOS_SEATBELT_BASE_POLICY}\n{file_read_policy}\n{file_write_policy}\n{network_policy}"
+    );
+    let mut seatbelt_args: Vec<String> = vec!["-p".to_string(), full_policy];
+    seatbelt_args.extend(extra_cli_args);
+    seatbelt_args.push("--".to_string());
+    seatbelt_args.extend(command);
+    seatbelt_args
+}

codex-rs/core/src/spawn.rs

@@ -0,0 +1,102 @@
+use std::collections::HashMap;
+use std::path::PathBuf;
+use std::process::Stdio;
+use tokio::process::Child;
+use tokio::process::Command;
+use tracing::trace;
+
+use crate::protocol::SandboxPolicy;
+
+/// Experimental environment variable that will be set to some non-empty value
+/// if both of the following are true:
+///
+/// 1. The process was spawned by Codex as part of a shell tool call.
+/// 2. SandboxPolicy.has_full_network_access() was false for the tool call.
+///
+/// We may try to have just one environment variable for all sandboxing
+/// attributes, so this may change in the future.
+pub const CODEX_SANDBOX_NETWORK_DISABLED_ENV_VAR: &str = "CODEX_SANDBOX_NETWORK_DISABLED";
+
+#[derive(Debug, Clone, Copy)]
+pub enum StdioPolicy {
+    RedirectForShellTool,
+    Inherit,
+}
+
+/// Spawns the appropriate child process for the ExecParams and SandboxPolicy,
+/// ensuring the args and environment variables used to create the `Command`
+/// (and `Child`) honor the configuration.
+///
+/// For now, we take `SandboxPolicy` as a parameter to spawn_child() because
+/// we need to determine whether to set the
+/// `CODEX_SANDBOX_NETWORK_DISABLED_ENV_VAR` environment variable.
+pub(crate) async fn spawn_child_async(
+    program: PathBuf,
+    args: Vec<String>,
+    #[cfg_attr(not(unix), allow(unused_variables))] arg0: Option<&str>,
+    cwd: PathBuf,
+    sandbox_policy: &SandboxPolicy,
+    stdio_policy: StdioPolicy,
+    env: HashMap<String, String>,
+) -> std::io::Result<Child> {
+    trace!(
+        "spawn_child_async: {program:?} {args:?} {arg0:?} {cwd:?} {sandbox_policy:?} {stdio_policy:?} {env:?}"
+    );
+
+    let mut cmd = Command::new(&program);
+    #[cfg(unix)]
+    cmd.arg0(arg0.map_or_else(|| program.to_string_lossy().to_string(), String::from));
+    cmd.args(args);
+    cmd.current_dir(cwd);
+    cmd.env_clear();
+    cmd.envs(env);
+
+    if !sandbox_policy.has_full_network_access() {
+        cmd.env(CODEX_SANDBOX_NETWORK_DISABLED_ENV_VAR, "1");
+    }
+
+    // If this Codex process dies (including being killed via SIGKILL), we want
+    // any child processes that were spawned as part of a `"shell"` tool call
+    // to also be terminated.
+
+    // This relies on prctl(2), so it only works on Linux.
+    #[cfg(target_os = "linux")]
+    unsafe {
+        cmd.pre_exec(|| {
+            // This prctl call effectively requests, "deliver SIGTERM when my
+            // current parent dies."
+            if libc::prctl(libc::PR_SET_PDEATHSIG, libc::SIGTERM) == -1 {
+                return Err(std::io::Error::last_os_error());
+            }
+
+            // Though if there was a race condition and this pre_exec() block is
+            // run _after_ the parent (i.e., the Codex process) has already
+            // exited, then the parent is the _init_ process (which will never
+            // die), so we should just terminate the child process now.
+            if libc::getppid() == 1 {
+                libc::raise(libc::SIGTERM);
+            }
+            Ok(())
+        });
+    }
+
+    match stdio_policy {
+        StdioPolicy::RedirectForShellTool => {
+            // Do not create a file descriptor for stdin because otherwise some
+            // commands may hang forever waiting for input. For example, ripgrep has
+            // a heuristic where it may try to read from stdin as explained here:
+            // https://github.com/BurntSushi/ripgrep/blob/e2362d4d5185d02fa857bf381e7bd52e66fafc73/crates/core/flags/hiargs.rs#L1101-L1103
+            cmd.stdin(Stdio::null());
+
+            cmd.stdout(Stdio::piped()).stderr(Stdio::piped());
+        }
+        StdioPolicy::Inherit => {
+            // Inherit stdin, stdout, and stderr from the parent process.
+            cmd.stdin(Stdio::inherit())
+                .stdout(Stdio::inherit())
+                .stderr(Stdio::inherit());
+        }
+    }
+
+    cmd.kill_on_drop(true).spawn()
+}

codex-rs/core/tests/cli_stream.rs

@@ -1,7 +1,7 @@
 #![expect(clippy::unwrap_used)]
 
 use assert_cmd::Command as AssertCommand;
-use codex_core::exec::CODEX_SANDBOX_NETWORK_DISABLED_ENV_VAR;
+use codex_core::spawn::CODEX_SANDBOX_NETWORK_DISABLED_ENV_VAR;
 use std::time::Duration;
 use std::time::Instant;
 use tempfile::TempDir;

codex-rs/core/tests/client.rs

@@ -5,11 +5,11 @@ use codex_core::Codex;
 use codex_core::CodexSpawnOk;
 use codex_core::ModelProviderInfo;
 use codex_core::built_in_model_providers;
-use codex_core::exec::CODEX_SANDBOX_NETWORK_DISABLED_ENV_VAR;
 use codex_core::protocol::EventMsg;
 use codex_core::protocol::InputItem;
 use codex_core::protocol::Op;
 use codex_core::protocol::SessionConfiguredEvent;
+use codex_core::spawn::CODEX_SANDBOX_NETWORK_DISABLED_ENV_VAR;
 use codex_login::AuthDotJson;
 use codex_login::AuthMode;
 use codex_login::CodexAuth;

codex-rs/core/tests/stream_no_completed.rs

@@ -6,10 +6,10 @@ use std::time::Duration;
 use codex_core::Codex;
 use codex_core::CodexSpawnOk;
 use codex_core::ModelProviderInfo;
-use codex_core::exec::CODEX_SANDBOX_NETWORK_DISABLED_ENV_VAR;
 use codex_core::protocol::EventMsg;
 use codex_core::protocol::InputItem;
 use codex_core::protocol::Op;
+use codex_core::spawn::CODEX_SANDBOX_NETWORK_DISABLED_ENV_VAR;
 use codex_login::CodexAuth;
 use core_test_support::load_default_config_for_test;
 use core_test_support::load_sse_fixture;

codex-rs/mcp-server/tests/codex_tool.rs

@@ -3,9 +3,9 @@ use std::env;
 use std::path::Path;
 use std::path::PathBuf;
 
-use codex_core::exec::CODEX_SANDBOX_NETWORK_DISABLED_ENV_VAR;
 use codex_core::protocol::FileChange;
 use codex_core::protocol::ReviewDecision;
+use codex_core::spawn::CODEX_SANDBOX_NETWORK_DISABLED_ENV_VAR;
 use codex_mcp_server::CodexToolCallParam;
 use codex_mcp_server::ExecApprovalElicitRequestParams;
 use codex_mcp_server::ExecApprovalResponse;

codex-rs/mcp-server/tests/interrupt.rs

@@ -3,7 +3,7 @@
 
 use std::path::Path;
 
-use codex_core::exec::CODEX_SANDBOX_NETWORK_DISABLED_ENV_VAR;
+use codex_core::spawn::CODEX_SANDBOX_NETWORK_DISABLED_ENV_VAR;
 use codex_mcp_server::CodexToolCallParam;
 use mcp_types::JSONRPCResponse;
 use mcp_types::RequestId;