fix: overhaul how we spawn commands under seccomp/landlock on Linux

codex-rs/Cargo.lock

@@ -491,6 +491,7 @@ dependencies = [
  "codex-common",
  "codex-core",
  "codex-exec",
+ "codex-linux-sandbox",
  "codex-mcp-server",
  "codex-tui",
  "serde_json",
@@ -562,6 +563,7 @@ dependencies = [
  "clap",
  "codex-common",
  "codex-core",
+ "codex-linux-sandbox",
  "mcp-types",
  "owo-colors 4.2.0",
  "serde_json",
@@ -591,6 +593,18 @@ dependencies = [
  "tempfile",
 ]
 
+[[package]]
+name = "codex-linux-sandbox"
+version = "0.0.0"
+dependencies = [
+ "clap",
+ "codex-common",
+ "codex-core",
+ "landlock",
+ "libc",
+ "seccompiler",
+]
+
 [[package]]
 name = "codex-mcp-client"
 version = "0.0.0"

codex-rs/Cargo.toml

@@ -8,6 +8,7 @@ members = [
     "core",
     "exec",
     "execpolicy",
+    "linux-sandbox",
     "mcp-client",
     "mcp-server",
     "mcp-types",
@@ -23,7 +24,7 @@ version = "0.0.0"
 edition = "2024"
 
 [workspace.lints]
-rust = { }
+rust = {}
 
 [workspace.lints.clippy]
 expect_used = "deny"

codex-rs/cli/Cargo.toml

@@ -7,10 +7,6 @@ edition = "2024"
 name = "codex"
 path = "src/main.rs"
 
-[[bin]]
-name = "codex-linux-sandbox"
-path = "src/linux-sandbox/main.rs"
-
 [lib]
 name = "codex_cli"
 path = "src/lib.rs"
@@ -24,6 +20,7 @@ clap = { version = "4", features = ["derive"] }
 codex-core = { path = "../core" }
 codex-common = { path = "../common", features = ["cli"] }
 codex-exec = { path = "../exec" }
+codex-linux-sandbox = { path = "../linux-sandbox" }
 codex-mcp-server = { path = "../mcp-server" }
 codex-tui = { path = "../tui" }
 serde_json = "1"

codex-rs/cli/src/landlock.rs

@@ -1,37 +0,0 @@
-//! `debug landlock` implementation for the Codex CLI.
-//!
-//! On Linux the command is executed inside a Landlock + seccomp sandbox by
-//! calling the low-level `exec_linux` helper from `codex_core::linux`.
-
-use codex_core::config::Config;
-use codex_core::exec::StdioPolicy;
-use codex_core::exec::spawn_child_sync;
-use codex_core::exec_linux::apply_sandbox_policy_to_current_thread;
-use std::process::ExitStatus;
-
-use crate::exit_status::handle_exit_status;
-
-/// Execute `command` in a Linux sandbox (Landlock + seccomp) the way Codex
-/// would.
-pub fn run_landlock(command: Vec<String>, config: &Config) -> anyhow::Result<()> {
-    if command.is_empty() {
-        anyhow::bail!("command args are empty");
-    }
-
-    // Spawn a new thread and apply the sandbox policies there.
-    let env = codex_core::exec_env::create_env(&config.shell_environment_policy);
-    let sandbox_policy = config.sandbox_policy.clone();
-    let handle = std::thread::spawn(move || -> anyhow::Result<ExitStatus> {
-        let cwd = std::env::current_dir()?;
-
-        apply_sandbox_policy_to_current_thread(&sandbox_policy, &cwd)?;
-        let mut child = spawn_child_sync(command, cwd, &sandbox_policy, StdioPolicy::Inherit, env)?;
-        let status = child.wait()?;
-        Ok(status)
-    });
-    let status = handle
-        .join()
-        .map_err(|e| anyhow::anyhow!("Failed to join thread: {e:?}"))??;
-
-    handle_exit_status(status);
-}

codex-rs/cli/src/lib.rs

@@ -1,6 +1,4 @@
 mod exit_status;
-#[cfg(unix)]
-pub mod landlock;
 pub mod proto;
 pub mod seatbelt;
 

codex-rs/cli/src/linux-sandbox/main.rs

@@ -1,28 +0,0 @@
-#[cfg(not(target_os = "linux"))]
-fn main() -> anyhow::Result<()> {
-    eprintln!("codex-linux-sandbox is not supported on this platform.");
-    std::process::exit(1);
-}
-
-#[cfg(target_os = "linux")]
-fn main() -> anyhow::Result<()> {
-    use clap::Parser;
-    use codex_cli::LandlockCommand;
-    use codex_cli::create_sandbox_policy;
-    use codex_cli::landlock;
-    use codex_core::config::Config;
-    use codex_core::config::ConfigOverrides;
-
-    let LandlockCommand {
-        full_auto,
-        sandbox,
-        command,
-    } = LandlockCommand::parse();
-    let sandbox_policy = create_sandbox_policy(full_auto, sandbox);
-    let config = Config::load_with_overrides(ConfigOverrides {
-        sandbox_policy: Some(sandbox_policy),
-        ..Default::default()
-    })?;
-    landlock::run_landlock(command, &config)?;
-    Ok(())
-}

codex-rs/cli/src/main.rs

@@ -1,3 +1,5 @@
+use std::path::Path;
+
 use clap::Parser;
 use codex_cli::LandlockCommand;
 use codex_cli::SeatbeltCommand;
@@ -6,6 +8,7 @@ use codex_cli::proto;
 use codex_cli::seatbelt;
 use codex_core::config::Config;
 use codex_core::config::ConfigOverrides;
+use codex_core::exec_env::create_env;
 use codex_exec::Cli as ExecCli;
 use codex_tui::Cli as TuiCli;
 
@@ -64,8 +67,27 @@ enum DebugCommand {
 #[derive(Debug, Parser)]
 struct ReplProto {}
 
-#[tokio::main]
-async fn main() -> anyhow::Result<()> {
+fn main() -> anyhow::Result<()> {
+    // Determine if we were invoked via the special alias.
+    let argv0 = std::env::args().next().unwrap_or_default();
+    let exe_name = Path::new(&argv0)
+        .file_name()
+        .and_then(|s| s.to_str())
+        .unwrap_or("");
+
+    if exe_name == "codex-linux-sandbox" {
+        codex_linux_sandbox::run_main()
+    }
+
+    // Regular `codex` invocation – parse the normal CLI.
+    let runtime = tokio::runtime::Runtime::new()?;
+    runtime.block_on(async {
+        cli_main().await?;
+        Ok(())
+    })
+}
+
+async fn cli_main() -> anyhow::Result<()> {
     let cli = MultitoolCli::parse();
 
     match cli.subcommand {
@@ -94,22 +116,32 @@ async fn main() -> anyhow::Result<()> {
                 })?;
                 seatbelt::run_seatbelt(command, &config).await?;
             }
-            #[cfg(unix)]
             DebugCommand::Landlock(LandlockCommand {
                 command,
                 sandbox,
                 full_auto,
             }) => {
                 let sandbox_policy = create_sandbox_policy(full_auto, sandbox);
+                let cwd = std::env::current_dir()?;
                 let config = Config::load_with_overrides(ConfigOverrides {
                     sandbox_policy: Some(sandbox_policy),
                     ..Default::default()
                 })?;
-                codex_cli::landlock::run_landlock(command, &config)?;
-            }
-            #[cfg(not(unix))]
-            DebugCommand::Landlock(_) => {
-                anyhow::bail!("Landlock is only supported on Linux.");
+                let full_args = codex_core::exec::create_linux_sandbox_command_args(
+                    command,
+                    &config.sandbox_policy,
+                    &cwd,
+                );
+
+                let env = create_env(&config.shell_environment_policy);
+                codex_core::exec::spawn_command_under_linux_sandbox(
+                    full_args,
+                    &config.sandbox_policy,
+                    cwd,
+                    codex_core::exec::StdioPolicy::Inherit,
+                    env,
+                )
+                .await?;
             }
         },
     }

codex-rs/core/src/exec.rs

@@ -21,7 +21,6 @@ use tokio::sync::Notify;
 use crate::error::CodexErr;
 use crate::error::Result;
 use crate::error::SandboxErr;
-use crate::exec_linux::exec_linux;
 use crate::protocol::SandboxPolicy;
 
 // Maximum we send for each stream, which is either:
@@ -101,7 +100,25 @@ pub async fn process_exec_tool_call(
             .await?;
             consume_truncated_output(child, ctrl_c, timeout_ms).await
         }
-        SandboxType::LinuxSeccomp => exec_linux(params, ctrl_c, sandbox_policy),
+        SandboxType::LinuxSeccomp => {
+            let ExecParams {
+                command,
+                cwd,
+                timeout_ms,
+                env,
+            } = params;
+
+            let child = spawn_command_under_linux_sandbox(
+                command,
+                sandbox_policy,
+                cwd,
+                StdioPolicy::RedirectForShellTool,
+                env,
+            )
+            .await?;
+
+            consume_truncated_output(child, ctrl_c, timeout_ms).await
+        }
     };
     let duration = start.elapsed();
     match raw_output_result {
@@ -152,7 +169,104 @@ pub async fn spawn_command_under_seatbelt(
     env: HashMap<String, String>,
 ) -> std::io::Result<Child> {
     let seatbelt_command = create_seatbelt_command(command, sandbox_policy, &cwd);
-    spawn_child_async(seatbelt_command, cwd, sandbox_policy, stdio_policy, env).await
+    let arg0 = None;
+    spawn_child_async(
+        seatbelt_command,
+        arg0,
+        cwd,
+        sandbox_policy,
+        stdio_policy,
+        env,
+    )
+    .await
+}
+
+/// Spawn a shell tool command under the Linux Landlock+seccomp sandbox helper
+/// (codex-linux-sandbox).
+///
+/// Unlike macOS Seatbelt where we directly embed the policy text, the Linux
+/// helper accepts a list of `--sandbox-permission`/`-s` flags mirroring the
+/// public CLI.  We convert the internal [`SandboxPolicy`] representation into
+/// the equivalent CLI options so that front-ends and the business-logic layer
+/// remain decoupled from the platform-specific implementation.
+pub async fn spawn_command_under_linux_sandbox(
+    command: Vec<String>,
+    sandbox_policy: &SandboxPolicy,
+    cwd: PathBuf,
+    stdio_policy: StdioPolicy,
+    env: HashMap<String, String>,
+) -> std::io::Result<Child> {
+    let linux_cmd = create_linux_sandbox_command_args(command, sandbox_policy, &cwd);
+    let arg0 = Some("codex-linux-sandbox");
+    spawn_child_async(linux_cmd, arg0, cwd, sandbox_policy, stdio_policy, env).await
+}
+
+/// Converts the sandbox policy into the CLI invocation for `codex-linux-sandbox`.
+pub fn create_linux_sandbox_command_args(
+    command: Vec<String>,
+    sandbox_policy: &SandboxPolicy,
+    cwd: &Path,
+) -> Vec<String> {
+    // TODO(mbolin): Require the client to pass codex_linux_sandbox_exe as a
+    // parameter to this function because code in `codex_core` should assume it
+    // is bundled in a binary that special-cases arg0 when it is
+    // "codex-linux-sandbox".
+    #[expect(clippy::expect_used)]
+    let codex_linux_sandbox_exe =
+        std::env::current_exe().expect("failed to get current executable");
+
+    #[expect(clippy::expect_used)]
+    let mut linux_cmd: Vec<String> = vec![
+        codex_linux_sandbox_exe
+            .to_str()
+            .expect("failed to convert path to str")
+            .to_string(),
+    ];
+
+    // If the policy matches the built-in “full-auto” setting, use the concise flag.
+    if *sandbox_policy == SandboxPolicy::new_full_auto_policy() {
+        linux_cmd.push("--full-auto".to_string());
+    } else {
+        // Otherwise, translate individual permissions.
+        // Use high-level helper methods to infer flags when we cannot see the
+        // exact permission list (private field).
+
+        if sandbox_policy.has_full_disk_read_access() {
+            linux_cmd.extend(["-s", "disk-full-read-access"].map(String::from));
+        }
+
+        if sandbox_policy.has_full_disk_write_access() {
+            linux_cmd.extend(["-s", "disk-full-write-access"].map(String::from));
+        } else {
+            // Derive granular writable paths (includes cwd if `DiskWriteCwd` is
+            // present).
+            for root in sandbox_policy.get_writable_roots_with_cwd(cwd) {
+                // Check if this path corresponds exactly to cwd to map to
+                // `disk-write-cwd`, otherwise use the generic folder rule.
+                if root == cwd {
+                    linux_cmd.extend(["-s", "disk-write-cwd"].map(String::from));
+                } else {
+                    linux_cmd.extend([
+                        "-s".to_string(),
+                        format!("disk-write-folder={}", root.to_string_lossy()),
+                    ]);
+                }
+            }
+        }
+
+        if sandbox_policy.has_full_network_access() {
+            linux_cmd.extend(["-s", "network-full-access"].map(String::from));
+        }
+    }
+
+    // Separator so that command arguments starting with `-` are not parsed as
+    // options of the helper itself.
+    linux_cmd.push("--".to_string());
+
+    // Append the original tool command.
+    linux_cmd.extend(command);
+
+    linux_cmd
 }
 
 fn create_seatbelt_command(
@@ -243,8 +357,10 @@ async fn exec(
     sandbox_policy: &SandboxPolicy,
     ctrl_c: Arc<Notify>,
 ) -> Result<RawExecToolCallOutput> {
+    let arg0 = None;
     let child = spawn_child_async(
         command,
+        arg0,
         cwd,
         sandbox_policy,
         StdioPolicy::RedirectForShellTool,
@@ -260,124 +376,62 @@ pub enum StdioPolicy {
     Inherit,
 }
 
-macro_rules! configure_command {
-    (
-        $cmd_type: path,
-        $command: expr,
-        $cwd: expr,
-        $sandbox_policy: expr,
-        $stdio_policy: expr,
-        $env_map: expr
-    ) => {{
-        // 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.
-        // Ultimately, we should be stricter about the environment variables that
-        // are set for the command (as we are when spawning an MCP server), so
-        // instead of SandboxPolicy, we should take the exact env to use for the
-        // Command (i.e., `env_clear().envs(env)`).
-        if $command.is_empty() {
-            return Err(io::Error::new(
-                io::ErrorKind::InvalidInput,
-                "command args are empty",
-            ));
-        }
-
-        let mut cmd = <$cmd_type>::new(&$command[0]);
-        cmd.args(&$command[1..]);
-        cmd.current_dir($cwd);
-
-        // Previously, to update the env for `cmd`, we did the straightforward
-        // thing of calling `env_clear()` followed by `envs(&env_map)` so
-        // that the spawned process inherited *only* the variables explicitly
-        // provided by the caller. On Linux, the combination of `env_clear()`
-        // and Landlock/seccomp caused a permission error whereas this more
-        // "surgical" approach of setting variables individually appears to
-        // work fine. More time with `strace` and friends is merited to fully
-        // debug thus, though we will soon use a helper binary like we do for
-        // Seatbelt, which will simplify this logic.
-
-        // Iterate through the current process environment first so we can
-        // decide, for every variable that already exists, whether we need to
-        // override its value.
-        let mut remaining_overrides = $env_map.clone();
-        for (key, current_val) in std::env::vars() {
-            if let Some(desired_val) = remaining_overrides.remove(&key) {
-                // The caller provided a value for this variable. Override it
-                // only if the value differs from what is currently set.
-                if desired_val != current_val {
-                    cmd.env(&key, desired_val);
-                }
-            }
-            // If the variable was not in `env_map`, we leave it unchanged.
-        }
-
-        // Any entries still left in `remaining_overrides` were not present in
-        // the parent environment. Add them now so that the child process sees
-        // the complete set requested by the caller.
-        for (key, val) in remaining_overrides {
-            cmd.env(key, val);
-        }
-
-        if !$sandbox_policy.has_full_network_access() {
-            cmd.env(CODEX_SANDBOX_NETWORK_DISABLED_ENV_VAR, "1");
-        }
-
-        match $stdio_policy {
-            StdioPolicy::RedirectForShellTool => {
-                // Do not create a file descriptor for stdin because otherwise some
-                // commands may hang forever waiting for input. For example, ripgrep has
-                // a heuristic where it may try to read from stdin as explained here:
-                // https://github.com/BurntSushi/ripgrep/blob/e2362d4d5185d02fa857bf381e7bd52e66fafc73/crates/core/flags/hiargs.rs#L1101-L1103
-                cmd.stdin(Stdio::null());
-
-                cmd.stdout(Stdio::piped()).stderr(Stdio::piped());
-            }
-            StdioPolicy::Inherit => {
-                // Inherit stdin, stdout, and stderr from the parent process.
-                cmd.stdin(Stdio::inherit())
-                    .stdout(Stdio::inherit())
-                    .stderr(Stdio::inherit());
-            }
-        }
-
-        std::io::Result::<$cmd_type>::Ok(cmd)
-    }};
-}
-
 /// 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.
-pub(crate) async fn spawn_child_async(
+async fn spawn_child_async(
     command: 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> {
-    let mut cmd = configure_command!(Command, command, cwd, sandbox_policy, stdio_policy, env)?;
-    cmd.kill_on_drop(true).spawn()
-}
+    // 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.
+    // Ultimately, we should be stricter about the environment variables that
+    // are set for the command (as we are when spawning an MCP server), so
+    // instead of SandboxPolicy, we should take the exact env to use for the
+    // Command (i.e., `env_clear().envs(env)`).
+    if command.is_empty() {
+        return Err(io::Error::new(
+            io::ErrorKind::InvalidInput,
+            "command args are empty",
+        ));
+    }
 
-/// Alternative version of `spawn_child_async()` that returns
-/// `std::process::Child` instead of `tokio::process::Child`. This is useful for
-/// spawning a child process in a thread that is not running a Tokio runtime.
-pub fn spawn_child_sync(
-    command: Vec<String>,
-    cwd: PathBuf,
-    sandbox_policy: &SandboxPolicy,
-    stdio_policy: StdioPolicy,
-    env: HashMap<String, String>,
-) -> std::io::Result<std::process::Child> {
-    let mut cmd = configure_command!(
-        std::process::Command,
-        command,
-        cwd,
-        sandbox_policy,
-        stdio_policy,
-        env
-    )?;
-    cmd.spawn()
+    let mut cmd = Command::new(&command[0]);
+    #[cfg(unix)]
+    cmd.arg0(arg0.unwrap_or_else(|| &command[0]));
+    cmd.args(&command[1..]);
+    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");
+    }
+
+    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

codex-rs/core/src/exec_linux.rs

@@ -1,79 +0,0 @@
-use std::io;
-use std::path::Path;
-use std::sync::Arc;
-
-use crate::error::CodexErr;
-use crate::error::Result;
-use crate::exec::ExecParams;
-use crate::exec::RawExecToolCallOutput;
-use crate::exec::StdioPolicy;
-use crate::exec::consume_truncated_output;
-use crate::exec::spawn_child_async;
-use crate::protocol::SandboxPolicy;
-
-use tokio::sync::Notify;
-
-pub fn exec_linux(
-    params: ExecParams,
-    ctrl_c: Arc<Notify>,
-    sandbox_policy: &SandboxPolicy,
-) -> Result<RawExecToolCallOutput> {
-    // Allow READ on /
-    // Allow WRITE on /dev/null
-    let ctrl_c_copy = ctrl_c.clone();
-    let sandbox_policy = sandbox_policy.clone();
-
-    // Isolate thread to run the sandbox from
-    let tool_call_output = std::thread::spawn(move || {
-        let rt = tokio::runtime::Builder::new_current_thread()
-            .enable_all()
-            .build()?;
-
-        rt.block_on(async {
-            let ExecParams {
-                command,
-                cwd,
-                timeout_ms,
-                env,
-            } = params;
-            apply_sandbox_policy_to_current_thread(&sandbox_policy, &cwd)?;
-            let child = spawn_child_async(
-                command,
-                cwd,
-                &sandbox_policy,
-                StdioPolicy::RedirectForShellTool,
-                env,
-            )
-            .await?;
-            consume_truncated_output(child, ctrl_c_copy, timeout_ms).await
-        })
-    })
-    .join();
-
-    match tool_call_output {
-        Ok(Ok(output)) => Ok(output),
-        Ok(Err(e)) => Err(e),
-        Err(e) => Err(CodexErr::Io(io::Error::other(format!(
-            "thread join failed: {e:?}"
-        )))),
-    }
-}
-
-#[cfg(target_os = "linux")]
-pub fn apply_sandbox_policy_to_current_thread(
-    sandbox_policy: &SandboxPolicy,
-    cwd: &Path,
-) -> Result<()> {
-    crate::landlock::apply_sandbox_policy_to_current_thread(sandbox_policy, cwd)
-}
-
-#[cfg(not(target_os = "linux"))]
-pub fn apply_sandbox_policy_to_current_thread(
-    _sandbox_policy: &SandboxPolicy,
-    _cwd: &Path,
-) -> Result<()> {
-    Err(CodexErr::Io(io::Error::new(
-        io::ErrorKind::InvalidInput,
-        "linux sandbox is not supported on this platform",
-    )))
-}

codex-rs/core/src/lib.rs

@@ -18,11 +18,8 @@ mod conversation_history;
 pub mod error;
 pub mod exec;
 pub mod exec_env;
-pub mod exec_linux;
 mod flags;
 mod is_safe_command;
-#[cfg(target_os = "linux")]
-pub mod landlock;
 mod mcp_connection_manager;
 mod mcp_tool_call;
 mod message_history;

codex-rs/exec/Cargo.toml

@@ -20,6 +20,7 @@ chrono = "0.4.40"
 clap = { version = "4", features = ["derive"] }
 codex-core = { path = "../core" }
 codex-common = { path = "../common", features = ["cli", "elapsed"] }
+codex-linux-sandbox = { path = "../linux-sandbox" }
 mcp-types = { path = "../mcp-types" }
 owo-colors = "4.2.0"
 serde_json = "1"

codex-rs/exec/src/main.rs

@@ -1,11 +1,38 @@
+//! Entry-point for the `codex-exec` binary.
+//!
+//! When this CLI is invoked normally, it parses the standard `codex-exec` CLI
+//! options and launches the non-interactive Codex agent. However, if it is
+//! invoked with arg0 as `codex-linux-sandbox`, we instead treat the invocation
+//! as a request to run the logic for the standalone `codex-linux-sandbox`
+//! executable (i.e., parse any -s args and then run a *sandboxed* command under
+//! Landlock + seccomp.
+//!
+//! This allows us to ship a completely separate set of functionality as part
+//! of the `codex-exec` binary.
 use clap::Parser;
 use codex_exec::Cli;
 use codex_exec::run_main;
+use std::path::Path;
 
-#[tokio::main]
-async fn main() -> anyhow::Result<()> {
-    let cli = Cli::parse();
-    run_main(cli).await?;
+// No #[tokio::main]! If arg0 is `codex-linux-sandbox`, we delegate to
+// `codex_linux_sandbox::run_main()` and do not want to start the Tokio runtime.
+fn main() -> anyhow::Result<()> {
+    // Determine if we were invoked via the special alias.
+    let argv0 = std::env::args().next().unwrap_or_default();
+    let exe_name = Path::new(&argv0)
+        .file_name()
+        .and_then(|s| s.to_str())
+        .unwrap_or("");
 
-    Ok(())
+    if exe_name == "codex-linux-sandbox" {
+        codex_linux_sandbox::run_main()
+    }
+
+    // Regular `codex-exec` invocation – parse the normal CLI.
+    let runtime = tokio::runtime::Runtime::new()?;
+    runtime.block_on(async {
+        let cli = Cli::parse();
+        run_main(cli).await?;
+        Ok(())
+    })
 }

codex-rs/linux-sandbox/Cargo.toml

@@ -0,0 +1,25 @@
+[package]
+name = "codex-linux-sandbox"
+version = { workspace = true }
+edition = "2024"
+
+[[bin]]
+name = "codex-linux-sandbox"
+path = "src/main.rs"
+
+[lib]
+name = "codex_linux_sandbox"
+path = "src/lib.rs"
+
+[lints]
+workspace = true
+
+[dependencies]
+clap = { version = "4", features = ["derive"] }
+codex-core = { path = "../core" }
+codex-common = { path = "../common", features = ["cli"] }
+
+[target.'cfg(target_os = "linux")'.dependencies]
+libc = "0.2.172"
+landlock = "0.4.1"
+seccompiler = "0.5.0"

codex-rs/linux-sandbox/README.md

@@ -0,0 +1,8 @@
+# codex-linux-sandbox
+
+This crate is responsible for producing:
+
+- a `codex-linux-sandbox` standalone executable for Linux that is bundled with the Node.js version of the Codex CLI
+- a lib crate that exposes the business logic of the executable as `run_main()` so that
+  - the `codex-exec` CLI can check if its arg0 is `codex-linux-sandbox` and, if so, execute as if it were `codex-linux-sandbox`
+  - this should also be true of the `codex` multitool CLI

codex-rs/linux-sandbox/src/landlock.rs

@@ -2,10 +2,10 @@ use std::collections::BTreeMap;
 use std::path::Path;
 use std::path::PathBuf;
 
-use crate::error::CodexErr;
-use crate::error::Result;
-use crate::error::SandboxErr;
-use crate::protocol::SandboxPolicy;
+use codex_core::error::CodexErr;
+use codex_core::error::Result;
+use codex_core::error::SandboxErr;
+use codex_core::protocol::SandboxPolicy;
 
 use landlock::ABI;
 use landlock::Access;

codex-rs/linux-sandbox/src/lib.rs

@@ -0,0 +1,12 @@
+#[cfg(target_os = "linux")]
+mod landlock;
+#[cfg(target_os = "linux")]
+mod linux_run_main;
+
+#[cfg(target_os = "linux")]
+pub use linux_run_main::run_main;
+
+#[cfg(not(target_os = "linux"))]
+pub fn run_main() -> ! {
+    panic!("codex-linux-sandbox is only supported on Linux");
+}

codex-rs/linux-sandbox/src/linux_run_main.rs

@@ -0,0 +1,57 @@
+use clap::Parser;
+use codex_common::SandboxPermissionOption;
+use std::ffi::CString;
+
+use crate::landlock::apply_sandbox_policy_to_current_thread;
+
+#[derive(Debug, Parser)]
+pub struct LandlockCommand {
+    #[clap(flatten)]
+    pub sandbox: SandboxPermissionOption,
+
+    /// Full command args to run under landlock.
+    #[arg(trailing_var_arg = true)]
+    pub command: Vec<String>,
+}
+
+pub fn run_main() -> ! {
+    let LandlockCommand { sandbox, command } = LandlockCommand::parse();
+
+    let sandbox_policy = match sandbox.permissions.map(Into::into) {
+        Some(sandbox_policy) => sandbox_policy,
+        None => codex_core::protocol::SandboxPolicy::new_read_only_policy(),
+    };
+
+    let cwd = match std::env::current_dir() {
+        Ok(cwd) => cwd,
+        Err(e) => {
+            panic!("failed to getcwd(): {e:?}");
+        }
+    };
+
+    if let Err(e) = apply_sandbox_policy_to_current_thread(&sandbox_policy, &cwd) {
+        panic!("error running landlock: {e:?}");
+    }
+
+    if command.is_empty() {
+        panic!("No command specified to execute.");
+    }
+
+    let c_command =
+        CString::new(command[0].as_str()).expect("Failed to convert command to CString");
+    let c_args: Vec<CString> = command
+        .iter()
+        .map(|arg| CString::new(arg.as_str()).expect("Failed to convert arg to CString"))
+        .collect();
+
+    let mut c_args_ptrs: Vec<*const libc::c_char> = c_args.iter().map(|arg| arg.as_ptr()).collect();
+    c_args_ptrs.push(std::ptr::null());
+
+    unsafe {
+        libc::execv(c_command.as_ptr(), c_args_ptrs.as_ptr());
+    }
+
+    // If execv returns, there was an error.
+    let err = std::io::Error::last_os_error();
+    panic!("Failed to execv: {err}");
+}

codex-rs/linux-sandbox/src/main.rs

@@ -0,0 +1,6 @@
+/// Note that the cwd, env, and command args are preserved in the ultimate call
+/// to `execv`, so the caller is responsible for ensuring those values are
+/// correct.
+fn main() -> ! {
+    codex_linux_sandbox::run_main()
+}