core: add stdin-backed sandboxed fs writes

core: route view_image through a sandbox-backed fs helper
core: add a sandbox-backed fs helper
2026-03-21 21:36:31 +03:00 · 2026-03-20 15:32:27 -07:00 · 2026-03-20 15:32:26 -07:00 · 2026-03-20 15:19:33 -07:00
32 changed files with 944 additions and 85 deletions
--- a/codex-rs/Cargo.lock
+++ b/codex-rs/Cargo.lock
@@ -1572,6 +1572,7 @@ version = "0.0.0"
 dependencies = [
 "anyhow",
 "codex-apply-patch",
+ "codex-fs-ops",
 "codex-linux-sandbox",
 "codex-shell-escalation",
 "codex-utils-home-dir",
@@ -1863,6 +1864,7 @@ dependencies = [
 "codex-execpolicy",
 "codex-features",
 "codex-file-search",
+ "codex-fs-ops",
 "codex-git",
 "codex-hooks",
 "codex-login",
@@ -2119,6 +2121,14 @@ dependencies = [
 "tokio",
 ]

+[[package]]
+name = "codex-fs-ops"
+version = "0.0.0"
+dependencies = [
+ "pretty_assertions",
+ "tempfile",
+]
+
 [[package]]
 name = "codex-git"
 version = "0.0.0"
--- a/codex-rs/Cargo.toml
+++ b/codex-rs/Cargo.toml
@@ -10,8 +10,6 @@ members = [
    "debug-client",
    "apply-patch",
    "arg0",
-    "feedback",
-    "features",
    "codex-backend-openapi-models",
    "cloud-requirements",
    "cloud-tasks",
@@ -29,6 +27,9 @@ members = [
    "exec-server",
    "execpolicy",
    "execpolicy-legacy",
+    "feedback",
+    "features",
+    "fs-ops",
    "keyring-store",
    "file-search",
    "linux-sandbox",
@@ -111,9 +112,10 @@ codex-exec = { path = "exec" }
 codex-exec-server = { path = "exec-server" }
 codex-execpolicy = { path = "execpolicy" }
 codex-experimental-api-macros = { path = "codex-experimental-api-macros" }
-codex-feedback = { path = "feedback" }
 codex-features = { path = "features" }
+codex-feedback = { path = "feedback" }
 codex-file-search = { path = "file-search" }
+codex-fs-ops = { path = "fs-ops" }
 codex-git = { path = "utils/git" }
 codex-hooks = { path = "hooks" }
 codex-keyring-store = { path = "keyring-store" }
--- a/codex-rs/arg0/Cargo.toml
+++ b/codex-rs/arg0/Cargo.toml
@@ -14,6 +14,7 @@ workspace = true
 [dependencies]
 anyhow = { workspace = true }
 codex-apply-patch = { workspace = true }
+codex-fs-ops = { workspace = true }
 codex-linux-sandbox = { workspace = true }
 codex-shell-escalation = { workspace = true }
 codex-utils-home-dir = { workspace = true }
--- a/codex-rs/arg0/src/lib.rs
+++ b/codex-rs/arg0/src/lib.rs
@@ -4,6 +4,7 @@ use std::path::Path;
 use std::path::PathBuf;

 use codex_apply_patch::CODEX_CORE_APPLY_PATCH_ARG1;
+use codex_fs_ops::CODEX_CORE_FS_OPS_ARG1;
 use codex_utils_home_dir::find_codex_home;
 #[cfg(unix)]
 use std::os::unix::fs::symlink;
@@ -105,6 +106,12 @@ pub fn arg0_dispatch() -> Option<Arg0PathEntryGuard> {
        };
        std::process::exit(exit_code);
    }
+    if argv1 == CODEX_CORE_FS_OPS_ARG1 {
+        let mut stdin = std::io::stdin();
+        let mut stdout = std::io::stdout();
+        let mut stderr = std::io::stderr();
+        codex_fs_ops::run_from_args_and_exit(args, &mut stdin, &mut stdout, &mut stderr);
+    }

    // This modifies the environment, which is not thread-safe, so do this
    // before creating any threads/the Tokio runtime.
--- a/codex-rs/cli/src/debug_sandbox.rs
+++ b/codex-rs/cli/src/debug_sandbox.rs
@@ -170,6 +170,7 @@ async fn run_command_under_sandbox(
                        command_vec,
                        &cwd_clone,
                        env_map,
+                        /*stdin_bytes*/ None,
                        /*timeout_ms*/ None,
                        config.permissions.windows_sandbox_private_desktop,
                    )
@@ -181,6 +182,7 @@ async fn run_command_under_sandbox(
                        command_vec,
                        &cwd_clone,
                        env_map,
+                        /*stdin_bytes*/ None,
                        /*timeout_ms*/ None,
                        config.permissions.windows_sandbox_private_desktop,
                    )
--- a/codex-rs/core/Cargo.toml
+++ b/codex-rs/core/Cargo.toml
@@ -39,6 +39,7 @@ codex-login = { workspace = true }
 codex-shell-command = { workspace = true }
 codex-skills = { workspace = true }
 codex-execpolicy = { workspace = true }
+codex-fs-ops = { workspace = true }
 codex-file-search = { workspace = true }
 codex-git = { workspace = true }
 codex-hooks = { workspace = true }
--- a/codex-rs/core/src/codex_tests.rs
+++ b/codex-rs/core/src/codex_tests.rs
@@ -4798,6 +4798,7 @@ async fn rejects_escalated_permissions_when_policy_not_on_request() {
        capture_policy: ExecCapturePolicy::ShellTool,
        env: HashMap::new(),
        network: None,
+        stdin: crate::exec::ExecStdin::Closed,
        sandbox_permissions,
        windows_sandbox_level: turn_context.windows_sandbox_level,
        windows_sandbox_private_desktop: turn_context
@@ -4816,6 +4817,7 @@ async fn rejects_escalated_permissions_when_policy_not_on_request() {
        capture_policy: ExecCapturePolicy::ShellTool,
        env: HashMap::new(),
        network: None,
+        stdin: crate::exec::ExecStdin::Closed,
        windows_sandbox_level: turn_context.windows_sandbox_level,
        windows_sandbox_private_desktop: turn_context
            .config
--- a/codex-rs/core/src/codex_tests_guardian.rs
+++ b/codex-rs/core/src/codex_tests_guardian.rs
@@ -128,6 +128,7 @@ async fn guardian_allows_shell_additional_permissions_requests_past_policy_valid
        capture_policy: ExecCapturePolicy::ShellTool,
        env: HashMap::new(),
        network: None,
+        stdin: crate::exec::ExecStdin::Closed,
        sandbox_permissions: SandboxPermissions::WithAdditionalPermissions,
        windows_sandbox_level: turn_context.windows_sandbox_level,
        windows_sandbox_private_desktop: turn_context
--- a/codex-rs/core/src/exec.rs
+++ b/codex-rs/core/src/exec.rs
@@ -12,6 +12,7 @@ use std::time::Instant;
 use async_channel::Sender;
 use tokio::io::AsyncRead;
 use tokio::io::AsyncReadExt;
+use tokio::io::AsyncWriteExt;
 use tokio::io::BufReader;
 use tokio::process::Child;
 use tokio_util::sync::CancellationToken;
@@ -81,6 +82,7 @@ pub struct ExecParams {
    pub capture_policy: ExecCapturePolicy,
    pub env: HashMap<String, String>,
    pub network: Option<NetworkProxy>,
+    pub stdin: ExecStdin,
    pub sandbox_permissions: SandboxPermissions,
    pub windows_sandbox_level: codex_protocol::config_types::WindowsSandboxLevel,
    pub windows_sandbox_private_desktop: bool,
@@ -97,7 +99,12 @@ pub enum ExecCapturePolicy {
    /// without the shell-oriented output cap or exec-expiration behavior.
    FullBuffer,
 }
-
+#[derive(Clone, Debug, Default)]
+pub enum ExecStdin {
+    #[default]
+    Closed,
+    Bytes(Vec<u8>),
+}
 fn select_process_exec_tool_sandbox_type(
    file_system_sandbox_policy: &FileSystemSandboxPolicy,
    network_sandbox_policy: NetworkSandboxPolicy,
@@ -263,6 +270,7 @@ pub fn build_exec_request(
        expiration,
        capture_policy,
        network,
+        stdin: _stdin,
        sandbox_permissions,
        windows_sandbox_level,
        windows_sandbox_private_desktop,
@@ -319,11 +327,68 @@ pub(crate) async fn execute_exec_request(
    stdout_stream: Option<StdoutStream>,
    after_spawn: Option<Box<dyn FnOnce() + Send>>,
 ) -> Result<ExecToolCallOutput> {
+    let PreparedExecRequest {
+        params,
+        sandbox,
+        file_system_sandbox_policy,
+        network_sandbox_policy,
+    } = prepare_exec_request(exec_request);
+    let start = Instant::now();
+    let raw_output_result = exec(
+        params,
+        sandbox,
+        sandbox_policy,
+        &file_system_sandbox_policy,
+        network_sandbox_policy,
+        stdout_stream,
+        after_spawn,
+    )
+    .await;
+    let duration = start.elapsed();
+    Ok(normalize_exec_result(raw_output_result, sandbox, duration)?.to_utf8_lossy_output())
+}
+
+pub(crate) async fn execute_exec_request_raw_output(
+    exec_request: ExecRequest,
+    sandbox_policy: &SandboxPolicy,
+    stdout_stream: Option<StdoutStream>,
+    after_spawn: Option<Box<dyn FnOnce() + Send>>,
+) -> Result<ExecToolCallRawOutput> {
+    let PreparedExecRequest {
+        params,
+        sandbox,
+        file_system_sandbox_policy,
+        network_sandbox_policy,
+    } = prepare_exec_request(exec_request);
+    let start = Instant::now();
+    let raw_output_result = exec(
+        params,
+        sandbox,
+        sandbox_policy,
+        &file_system_sandbox_policy,
+        network_sandbox_policy,
+        stdout_stream,
+        after_spawn,
+    )
+    .await;
+    let duration = start.elapsed();
+    normalize_exec_result(raw_output_result, sandbox, duration)
+}
+
+struct PreparedExecRequest {
+    params: ExecParams,
+    sandbox: SandboxType,
+    file_system_sandbox_policy: FileSystemSandboxPolicy,
+    network_sandbox_policy: NetworkSandboxPolicy,
+}
+
+fn prepare_exec_request(exec_request: ExecRequest) -> PreparedExecRequest {
    let ExecRequest {
        command,
        cwd,
        env,
        network,
+        stdin,
        expiration,
        capture_policy,
        sandbox,
@@ -338,33 +403,25 @@ pub(crate) async fn execute_exec_request(
    } = exec_request;
    let _ = _sandbox_policy_from_env;

-    let params = ExecParams {
-        command,
-        cwd,
-        expiration,
-        capture_policy,
-        env,
-        network: network.clone(),
-        sandbox_permissions,
-        windows_sandbox_level,
-        windows_sandbox_private_desktop,
-        justification,
-        arg0,
-    };
-
-    let start = Instant::now();
-    let raw_output_result = exec(
-        params,
+    PreparedExecRequest {
+        params: ExecParams {
+            command,
+            cwd,
+            expiration,
+            capture_policy,
+            env,
+            network,
+            stdin,
+            sandbox_permissions,
+            windows_sandbox_level,
+            windows_sandbox_private_desktop,
+            justification,
+            arg0,
+        },
        sandbox,
-        sandbox_policy,
-        &file_system_sandbox_policy,
        network_sandbox_policy,
-        stdout_stream,
-        after_spawn,
-    )
-    .await;
-    let duration = start.elapsed();
-    finalize_exec_result(raw_output_result, sandbox, duration)
+        file_system_sandbox_policy,
+    }
 }

 #[cfg(target_os = "windows")]
@@ -448,6 +505,7 @@ async fn exec_windows_sandbox(
        cwd,
        mut env,
        network,
+        stdin,
        expiration,
        capture_policy,
        windows_sandbox_level,
@@ -489,6 +547,10 @@ async fn exec_windows_sandbox(
                command,
                &cwd,
                env,
+                match stdin {
+                    ExecStdin::Closed => None,
+                    ExecStdin::Bytes(bytes) => Some(bytes),
+                },
                timeout_ms,
                windows_sandbox_private_desktop,
            )
@@ -500,6 +562,10 @@ async fn exec_windows_sandbox(
                command,
                &cwd,
                env,
+                match stdin {
+                    ExecStdin::Closed => None,
+                    ExecStdin::Bytes(bytes) => Some(bytes),
+                },
                timeout_ms,
                windows_sandbox_private_desktop,
            )
@@ -558,19 +624,25 @@ async fn exec_windows_sandbox(
    })
 }

-fn finalize_exec_result(
+fn normalize_exec_result(
    raw_output_result: std::result::Result<RawExecToolCallOutput, CodexErr>,
    sandbox_type: SandboxType,
    duration: Duration,
-) -> Result<ExecToolCallOutput> {
+) -> Result<ExecToolCallRawOutput> {
    match raw_output_result {
        Ok(raw_output) => {
-            #[allow(unused_mut)]
-            let mut timed_out = raw_output.timed_out;
+            let RawExecToolCallOutput {
+                exit_status,
+                stdout,
+                stderr,
+                aggregated_output,
+                #[cfg_attr(target_os = "windows", allow(unused_mut))]
+                mut timed_out,
+            } = raw_output;

            #[cfg(target_family = "unix")]
            {
-                if let Some(signal) = raw_output.exit_status.signal() {
+                if let Some(signal) = exit_status.signal() {
                    if signal == TIMEOUT_CODE {
                        timed_out = true;
                    } else {
@@ -579,15 +651,12 @@ fn finalize_exec_result(
                }
            }

-            let mut exit_code = raw_output.exit_status.code().unwrap_or(-1);
+            let mut exit_code = exit_status.code().unwrap_or(-1);
            if timed_out {
                exit_code = EXEC_TIMEOUT_EXIT_CODE;
            }

-            let stdout = raw_output.stdout.from_utf8_lossy();
-            let stderr = raw_output.stderr.from_utf8_lossy();
-            let aggregated_output = raw_output.aggregated_output.from_utf8_lossy();
-            let exec_output = ExecToolCallOutput {
+            let exec_output = ExecToolCallRawOutput {
                exit_code,
                stdout,
                stderr,
@@ -598,13 +667,14 @@ fn finalize_exec_result(

            if timed_out {
                return Err(CodexErr::Sandbox(SandboxErr::Timeout {
-                    output: Box::new(exec_output),
+                    output: Box::new(exec_output.to_utf8_lossy_output()),
                }));
            }

-            if is_likely_sandbox_denied(sandbox_type, &exec_output) {
+            let string_output = exec_output.to_utf8_lossy_output();
+            if is_likely_sandbox_denied(sandbox_type, &string_output) {
                return Err(CodexErr::Sandbox(SandboxErr::Denied {
-                    output: Box::new(exec_output),
+                    output: Box::new(string_output),
                    network_policy_decision: None,
                }));
            }
@@ -796,6 +866,16 @@ pub struct ExecToolCallOutput {
    pub timed_out: bool,
 }

+#[derive(Clone, Debug)]
+pub(crate) struct ExecToolCallRawOutput {
+    pub exit_code: i32,
+    pub stdout: StreamOutput<Vec<u8>>,
+    pub stderr: StreamOutput<Vec<u8>>,
+    pub aggregated_output: StreamOutput<Vec<u8>>,
+    pub duration: Duration,
+    pub timed_out: bool,
+}
+
 impl Default for ExecToolCallOutput {
    fn default() -> Self {
        Self {
@@ -809,6 +889,19 @@ impl Default for ExecToolCallOutput {
    }
 }

+impl ExecToolCallRawOutput {
+    fn to_utf8_lossy_output(&self) -> ExecToolCallOutput {
+        ExecToolCallOutput {
+            exit_code: self.exit_code,
+            stdout: self.stdout.from_utf8_lossy(),
+            stderr: self.stderr.from_utf8_lossy(),
+            aggregated_output: self.aggregated_output.from_utf8_lossy(),
+            duration: self.duration,
+            timed_out: self.timed_out,
+        }
+    }
+}
+
 #[cfg_attr(not(target_os = "windows"), allow(unused_variables))]
 async fn exec(
    params: ExecParams,
@@ -839,6 +932,7 @@ async fn exec(
        mut env,
        network,
        arg0,
+        stdin,
        expiration,
        capture_policy,
        windows_sandbox_level: _,
@@ -867,12 +961,13 @@ async fn exec(
        network: None,
        stdio_policy: StdioPolicy::RedirectForShellTool,
        env,
+        stdin_open: matches!(stdin, ExecStdin::Bytes(_)),
    })
    .await?;
    if let Some(after_spawn) = after_spawn {
        after_spawn();
    }
-    consume_output(child, expiration, capture_policy, stdout_stream).await
+    consume_output(child, stdin, expiration, capture_policy, stdout_stream).await
 }

 #[cfg_attr(not(target_os = "windows"), allow(dead_code))]
@@ -930,10 +1025,19 @@ fn windows_restricted_token_sandbox_support(
 /// policy.
 async fn consume_output(
    mut child: Child,
+    stdin: ExecStdin,
    expiration: ExecExpiration,
    capture_policy: ExecCapturePolicy,
    stdout_stream: Option<StdoutStream>,
 ) -> Result<RawExecToolCallOutput> {
+    let stdin_task = match (child.stdin.take(), stdin) {
+        (Some(mut child_stdin), ExecStdin::Bytes(bytes)) => Some(tokio::spawn(async move {
+            child_stdin.write_all(&bytes).await?;
+            child_stdin.shutdown().await
+        })),
+        _ => None,
+    };
+
    // Both stdout and stderr were configured with `Stdio::piped()`
    // above, therefore `take()` should normally return `Some`.  If it doesn't
    // we treat it as an exceptional I/O error
@@ -1016,6 +1120,13 @@ async fn consume_output(

    let stdout = await_output(&mut stdout_handle, capture_policy.io_drain_timeout()).await?;
    let stderr = await_output(&mut stderr_handle, capture_policy.io_drain_timeout()).await?;
+    if let Some(stdin_task) = stdin_task {
+        match stdin_task.await {
+            Ok(Ok(())) => {}
+            Ok(Err(err)) => return Err(CodexErr::Io(err)),
+            Err(join_err) => return Err(CodexErr::Io(io::Error::other(join_err))),
+        }
+    }
    let aggregated_output = aggregate_output(&stdout, &stderr, retained_bytes_cap);

    Ok(RawExecToolCallOutput {
--- a/codex-rs/core/src/exec_tests.rs
+++ b/codex-rs/core/src/exec_tests.rs
@@ -105,6 +105,56 @@ async fn read_output_limits_retained_bytes_for_shell_capture() {
    assert_eq!(out.text.len(), EXEC_OUTPUT_MAX_BYTES);
 }

+#[tokio::test]
+async fn exec_passes_stdin_bytes_to_child() -> Result<()> {
+    let command = if cfg!(windows) {
+        vec![
+            "cmd.exe".to_string(),
+            "/Q".to_string(),
+            "/D".to_string(),
+            "/C".to_string(),
+            "more".to_string(),
+        ]
+    } else {
+        vec!["/bin/cat".to_string()]
+    };
+    let params = ExecParams {
+        command,
+        cwd: std::env::current_dir()?,
+        expiration: 1_000.into(),
+        env: std::env::vars().collect(),
+        network: None,
+        stdin: ExecStdin::Bytes(b"hello from stdin\n".to_vec()),
+        sandbox_permissions: SandboxPermissions::UseDefault,
+        windows_sandbox_level: WindowsSandboxLevel::Disabled,
+        windows_sandbox_private_desktop: false,
+        justification: None,
+        arg0: None,
+    };
+
+    let output = exec(
+        params,
+        SandboxType::None,
+        &SandboxPolicy::DangerFullAccess,
+        &FileSystemSandboxPolicy::from(&SandboxPolicy::DangerFullAccess),
+        NetworkSandboxPolicy::Enabled,
+        None,
+        None,
+    )
+    .await?;
+
+    let expected_stdout = if cfg!(windows) {
+        "hello from stdin\r\n"
+    } else {
+        "hello from stdin\n"
+    };
+    assert_eq!(output.exit_status.code(), Some(0));
+    assert_eq!(output.stdout.from_utf8_lossy().text, expected_stdout);
+    assert_eq!(output.stderr.from_utf8_lossy().text, "");
+
+    Ok(())
+}
+
 #[test]
 fn aggregate_output_prefers_stderr_on_contention() {
    let stdout = StreamOutput {
@@ -588,6 +638,7 @@ async fn kill_child_process_group_kills_grandchildren_on_timeout() -> Result<()>
        capture_policy: ExecCapturePolicy::ShellTool,
        env,
        network: None,
+        stdin: ExecStdin::Closed,
        sandbox_permissions: SandboxPermissions::UseDefault,
        windows_sandbox_level: WindowsSandboxLevel::Disabled,
        windows_sandbox_private_desktop: false,
@@ -646,6 +697,7 @@ async fn process_exec_tool_call_respects_cancellation_token() -> Result<()> {
        capture_policy: ExecCapturePolicy::ShellTool,
        env,
        network: None,
+        stdin: ExecStdin::Closed,
        sandbox_permissions: SandboxPermissions::UseDefault,
        windows_sandbox_level: WindowsSandboxLevel::Disabled,
        windows_sandbox_private_desktop: false,
--- a/codex-rs/core/src/landlock.rs
+++ b/codex-rs/core/src/landlock.rs
@@ -56,6 +56,7 @@ where
        network,
        stdio_policy,
        env,
+        stdin_open: false,
    })
    .await
 }
--- a/codex-rs/core/src/lib.rs
+++ b/codex-rs/core/src/lib.rs
@@ -121,6 +121,7 @@ pub mod default_client {
 pub mod project_doc;
 mod rollout;
 pub(crate) mod safety;
+mod sandboxed_fs;
 pub mod seatbelt;
 pub mod shell;
 pub mod shell_snapshot;
--- a/codex-rs/core/src/sandboxed_fs.rs
+++ b/codex-rs/core/src/sandboxed_fs.rs
@@ -0,0 +1,162 @@
+use crate::codex::Session;
+use crate::codex::TurnContext;
+use crate::exec::ExecCapturePolicy;
+use crate::exec::ExecExpiration;
+use crate::exec::ExecStdin;
+use crate::exec::ExecToolCallRawOutput;
+use crate::exec::execute_exec_request_raw_output;
+use crate::sandboxing::CommandSpec;
+use crate::sandboxing::SandboxPermissions;
+use crate::sandboxing::merge_permission_profiles;
+use crate::tools::sandboxing::SandboxAttempt;
+use crate::tools::sandboxing::SandboxablePreference;
+use codex_fs_ops::CODEX_CORE_FS_OPS_ARG1;
+use codex_fs_ops::READ_FILE_OPERATION_ARG2;
+use codex_protocol::models::PermissionProfile;
+use codex_utils_absolute_path::AbsolutePathBuf;
+use std::collections::HashMap;
+use std::sync::Arc;
+use std::time::Duration;
+
+/// Reads the contents of the specified file subject to the sandbox constraints
+/// imposed by the provided session and turn context.
+///
+/// Note that this function is comparable to `cat FILE`, though unlike `cat
+/// FILE`, this function verifies that FILE is a regular file before reading,
+/// which means that if you pass `/dev/zero` as the path, it will error (rather
+/// than hang forever).
+pub(crate) async fn read_file(
+    path: &AbsolutePathBuf,
+    session: &Arc<Session>,
+    turn: &Arc<TurnContext>,
+) -> Result<Vec<u8>, SandboxedFsError> {
+    let output = perform_operation(
+        SandboxedFsOperation::Read { path: path.clone() },
+        session,
+        turn,
+    )
+    .await?;
+    Ok(output.stdout.text)
+}
+
+/// Operations supported by the [CODEX_CORE_FS_OPS_ARG1] sandbox helper.
+enum SandboxedFsOperation {
+    Read { path: AbsolutePathBuf },
+}
+
+async fn perform_operation(
+    operation: SandboxedFsOperation,
+    session: &Arc<Session>,
+    turn: &Arc<TurnContext>,
+) -> Result<ExecToolCallRawOutput, SandboxedFsError> {
+    let exe = std::env::current_exe().map_err(|error| SandboxedFsError::ResolveExe {
+        message: error.to_string(),
+    })?;
+    let additional_permissions = effective_granted_permissions(session).await;
+    let sandbox_manager = crate::sandboxing::SandboxManager::new();
+    let attempt = SandboxAttempt {
+        sandbox: sandbox_manager.select_initial(
+            &turn.file_system_sandbox_policy,
+            turn.network_sandbox_policy,
+            SandboxablePreference::Auto,
+            turn.windows_sandbox_level,
+            /*has_managed_network_requirements*/ false,
+        ),
+        policy: &turn.sandbox_policy,
+        file_system_policy: &turn.file_system_sandbox_policy,
+        network_policy: turn.network_sandbox_policy,
+        enforce_managed_network: false,
+        manager: &sandbox_manager,
+        sandbox_cwd: &turn.cwd,
+        codex_linux_sandbox_exe: turn.codex_linux_sandbox_exe.as_ref(),
+        use_legacy_landlock: turn.features.use_legacy_landlock(),
+        windows_sandbox_level: turn.windows_sandbox_level,
+        windows_sandbox_private_desktop: turn.config.permissions.windows_sandbox_private_desktop,
+    };
+
+    let args = match operation {
+        SandboxedFsOperation::Read { ref path } => vec![
+            CODEX_CORE_FS_OPS_ARG1.to_string(),
+            READ_FILE_OPERATION_ARG2.to_string(),
+            path.to_string_lossy().to_string(),
+        ],
+    };
+
+    // `FullBuffer` reads ignore exec expiration, but `ExecRequest` still requires
+    // an `expiration` field, so keep a placeholder timeout here until that API
+    // changes.
+    let ignored_expiration = Duration::from_secs(30);
+    let exec_request = attempt
+        .env_for(
+            CommandSpec {
+                program: exe.to_string_lossy().to_string(),
+                args,
+                cwd: turn.cwd.clone(),
+                env: HashMap::new(),
+                expiration: ExecExpiration::Timeout(ignored_expiration),
+                capture_policy: ExecCapturePolicy::FullBuffer,
+                sandbox_permissions: SandboxPermissions::UseDefault,
+                additional_permissions,
+                justification: None,
+            },
+            /*network*/ None,
+        )
+        .map_err(|error| SandboxedFsError::ProcessFailed {
+            exit_code: -1,
+            message: error.to_string(),
+        })?;
+    exec_request.stdin = stdin;
+
+    let effective_policy = exec_request.sandbox_policy.clone();
+    let output = execute_exec_request_raw_output(
+        exec_request,
+        &effective_policy,
+        /*stdout_stream*/ None,
+        /*after_spawn*/ None,
+    )
+    .await
+    .map_err(|error| SandboxedFsError::ProcessFailed {
+        exit_code: 1,
+        message: error.to_string(),
+    })?;
+    if output.exit_code == 0 {
+        Ok(output)
+    } else {
+        Err(parse_helper_failure(
+            output.exit_code,
+            &output.stderr.text,
+            &output.stdout.text,
+        ))
+    }
+}
+
+async fn effective_granted_permissions(session: &Session) -> Option<PermissionProfile> {
+    let granted_session_permissions = session.granted_session_permissions().await;
+    let granted_turn_permissions = session.granted_turn_permissions().await;
+    merge_permission_profiles(
+        granted_session_permissions.as_ref(),
+        granted_turn_permissions.as_ref(),
+    )
+}
+
+fn parse_helper_failure(exit_code: i32, stderr: &[u8], stdout: &[u8]) -> SandboxedFsError {
+    let stderr = String::from_utf8_lossy(stderr);
+    let stdout = String::from_utf8_lossy(stdout);
+    let message = if !stderr.trim().is_empty() {
+        stderr.trim().to_string()
+    } else if !stdout.trim().is_empty() {
+        stdout.trim().to_string()
+    } else {
+        "no error details emitted".to_string()
+    };
+
+    SandboxedFsError::ProcessFailed { exit_code, message }
+}
+
+#[derive(Debug, thiserror::Error)]
+pub(crate) enum SandboxedFsError {
+    #[error("failed to determine codex executable: {message}")]
+    ResolveExe { message: String },
+    #[error("sandboxed fs helper exited with code {exit_code}: {message}")]
+    ProcessFailed { exit_code: i32, message: String },
+}
--- a/codex-rs/core/src/sandboxing/mod.rs
+++ b/codex-rs/core/src/sandboxing/mod.rs
@@ -10,6 +10,7 @@ pub(crate) mod macos_permissions;

 use crate::exec::ExecCapturePolicy;
 use crate::exec::ExecExpiration;
+use crate::exec::ExecStdin;
 use crate::exec::ExecToolCallOutput;
 use crate::exec::SandboxType;
 use crate::exec::StdoutStream;
@@ -68,6 +69,7 @@ pub struct ExecRequest {
    pub cwd: PathBuf,
    pub env: HashMap<String, String>,
    pub network: Option<NetworkProxy>,
+    pub stdin: ExecStdin,
    pub expiration: ExecExpiration,
    pub capture_policy: ExecCapturePolicy,
    pub sandbox: SandboxType,
@@ -709,6 +711,7 @@ impl SandboxManager {
            cwd: spec.cwd,
            env,
            network: network.cloned(),
+            stdin: ExecStdin::Closed,
            expiration: spec.expiration,
            capture_policy: spec.capture_policy,
            sandbox,
--- a/codex-rs/core/src/seatbelt.rs
+++ b/codex-rs/core/src/seatbelt.rs
@@ -63,6 +63,7 @@ pub async fn spawn_command_under_seatbelt(
        network,
        stdio_policy,
        env,
+        stdin_open: false,
    })
    .await
 }
--- a/codex-rs/core/src/spawn.rs
+++ b/codex-rs/core/src/spawn.rs
@@ -45,6 +45,7 @@ pub(crate) struct SpawnChildRequest<'a> {
    pub network: Option<&'a NetworkProxy>,
    pub stdio_policy: StdioPolicy,
    pub env: HashMap<String, String>,
+    pub stdin_open: bool,
 }

 pub(crate) async fn spawn_child_async(request: SpawnChildRequest<'_>) -> std::io::Result<Child> {
@@ -57,6 +58,7 @@ pub(crate) async fn spawn_child_async(request: SpawnChildRequest<'_>) -> std::io
        network,
        stdio_policy,
        mut env,
+        stdin_open,
    } = request;

    trace!(
@@ -105,11 +107,15 @@ pub(crate) async fn spawn_child_async(request: SpawnChildRequest<'_>) -> std::io

    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());
+            if stdin_open {
+                cmd.stdin(Stdio::piped());
+            } else {
+                // 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());
        }
--- a/codex-rs/core/src/tasks/user_shell.rs
+++ b/codex-rs/core/src/tasks/user_shell.rs
@@ -11,6 +11,7 @@ use uuid::Uuid;

 use crate::codex::TurnContext;
 use crate::exec::ExecCapturePolicy;
+use crate::exec::ExecStdin;
 use crate::exec::ExecToolCallOutput;
 use crate::exec::SandboxType;
 use crate::exec::StdoutStream;
@@ -163,6 +164,7 @@ pub(crate) async fn execute_user_shell_command(
            Some(session.conversation_id),
        ),
        network: turn_context.network.clone(),
+        stdin: ExecStdin::Closed,
        // TODO(zhao-oai): Now that we have ExecExpiration::Cancellation, we
        // should use that instead of an "arbitrarily large" timeout here.
        expiration: USER_SHELL_TIMEOUT_MS.into(),
--- a/codex-rs/core/src/tools/handlers/shell.rs
+++ b/codex-rs/core/src/tools/handlers/shell.rs
@@ -7,6 +7,7 @@ use std::sync::Arc;
 use crate::codex::TurnContext;
 use crate::exec::ExecCapturePolicy;
 use crate::exec::ExecParams;
+use crate::exec::ExecStdin;
 use crate::exec_env::create_env;
 use crate::exec_policy::ExecApprovalRequest;
 use crate::function_tool::FunctionCallError;
@@ -74,6 +75,7 @@ impl ShellHandler {
            capture_policy: ExecCapturePolicy::ShellTool,
            env: create_env(&turn_context.shell_environment_policy, Some(thread_id)),
            network: turn_context.network.clone(),
+            stdin: ExecStdin::Closed,
            sandbox_permissions: params.sandbox_permissions.unwrap_or_default(),
            windows_sandbox_level: turn_context.windows_sandbox_level,
            windows_sandbox_private_desktop: turn_context
@@ -129,6 +131,7 @@ impl ShellCommandHandler {
            capture_policy: ExecCapturePolicy::ShellTool,
            env: create_env(&turn_context.shell_environment_policy, Some(thread_id)),
            network: turn_context.network.clone(),
+            stdin: ExecStdin::Closed,
            sandbox_permissions: params.sandbox_permissions.unwrap_or_default(),
            windows_sandbox_level: turn_context.windows_sandbox_level,
            windows_sandbox_private_desktop: turn_context
--- a/codex-rs/core/src/tools/handlers/view_image.rs
+++ b/codex-rs/core/src/tools/handlers/view_image.rs
@@ -14,6 +14,7 @@ use crate::function_tool::FunctionCallError;
 use crate::original_image_detail::can_request_original_image_detail;
 use crate::protocol::EventMsg;
 use crate::protocol::ViewImageToolCallEvent;
+use crate::sandboxed_fs;
 use crate::tools::context::ToolInvocation;
 use crate::tools::context::ToolOutput;
 use crate::tools::context::ToolPayload;
@@ -93,36 +94,6 @@ impl ToolHandler for ViewImageHandler {
            AbsolutePathBuf::try_from(turn.resolve_path(Some(args.path))).map_err(|error| {
                FunctionCallError::RespondToModel(format!("unable to resolve image path: {error}"))
            })?;
-
-        let metadata = turn
-            .environment
-            .get_filesystem()
-            .get_metadata(&abs_path)
-            .await
-            .map_err(|error| {
-                FunctionCallError::RespondToModel(format!(
-                    "unable to locate image at `{}`: {error}",
-                    abs_path.display()
-                ))
-            })?;
-
-        if !metadata.is_file {
-            return Err(FunctionCallError::RespondToModel(format!(
-                "image path `{}` is not a file",
-                abs_path.display()
-            )));
-        }
-        let file_bytes = turn
-            .environment
-            .get_filesystem()
-            .read_file(&abs_path)
-            .await
-            .map_err(|error| {
-                FunctionCallError::RespondToModel(format!(
-                    "unable to read image at `{}`: {error}",
-                    abs_path.display()
-                ))
-            })?;
        let event_path = abs_path.to_path_buf();

        let can_request_original_detail =
@@ -135,14 +106,24 @@ impl ToolHandler for ViewImageHandler {
            PromptImageMode::ResizeToFit
        };
        let image_detail = use_original_detail.then_some(ImageDetail::Original);
+        let image_bytes = sandboxed_fs::read_file(&abs_path, &session, &turn)
+            .await
+            .map_err(|error| {
+                let full_error = format!(
+                    "unable to read image file `{path}`: {error:?}",
+                    path = abs_path.display()
+                );
+                FunctionCallError::RespondToModel(full_error)
+            })?;

-        let image =
-            load_for_prompt_bytes(abs_path.as_path(), file_bytes, image_mode).map_err(|error| {
+        let image = load_for_prompt_bytes(abs_path.as_path(), image_bytes, image_mode).map_err(
+            |error| {
                FunctionCallError::RespondToModel(format!(
                    "unable to process image at `{}`: {error}",
                    abs_path.display()
                ))
-            })?;
+            },
+        )?;
        let image_url = image.into_data_url();

        session
--- a/codex-rs/core/src/tools/runtimes/shell/unix_escalation.rs
+++ b/codex-rs/core/src/tools/runtimes/shell/unix_escalation.rs
@@ -124,6 +124,7 @@ pub(super) async fn try_run_zsh_fork(
        cwd: sandbox_cwd,
        env: sandbox_env,
        network: sandbox_network,
+        stdin: _stdin,
        expiration: _sandbox_expiration,
        capture_policy: _capture_policy,
        sandbox,
@@ -904,6 +905,7 @@ impl ShellCommandExecutor for CoreShellCommandExecutor {
                cwd: self.cwd.clone(),
                env: exec_env,
                network: self.network.clone(),
+                stdin: crate::exec::ExecStdin::Closed,
                expiration: ExecExpiration::Cancellation(cancel_rx),
                capture_policy: ExecCapturePolicy::ShellTool,
                sandbox: self.sandbox,
--- a/codex-rs/core/tests/suite/exec.rs
+++ b/codex-rs/core/tests/suite/exec.rs
@@ -41,6 +41,7 @@ async fn run_test_cmd(tmp: TempDir, cmd: Vec<&str>) -> Result<ExecToolCallOutput
        capture_policy: ExecCapturePolicy::ShellTool,
        env: HashMap::new(),
        network: None,
+        stdin: codex_core::exec::ExecStdin::Closed,
        sandbox_permissions: SandboxPermissions::UseDefault,
        windows_sandbox_level: WindowsSandboxLevel::Disabled,
        windows_sandbox_private_desktop: false,
--- a/codex-rs/core/tests/suite/view_image.rs
+++ b/codex-rs/core/tests/suite/view_image.rs
@@ -3,6 +3,7 @@
 use base64::Engine;
 use base64::engine::general_purpose::STANDARD as BASE64_STANDARD;
 use codex_core::CodexAuth;
+use codex_core::config::Constrained;
 use codex_exec_server::CreateDirectoryOptions;
 use codex_features::Feature;
 use codex_protocol::config_types::ReasoningSummary;
@@ -14,9 +15,15 @@ use codex_protocol::openai_models::ModelsResponse;
 use codex_protocol::openai_models::ReasoningEffort;
 use codex_protocol::openai_models::ReasoningEffortPreset;
 use codex_protocol::openai_models::TruncationPolicyConfig;
+use codex_protocol::permissions::FileSystemAccessMode;
+use codex_protocol::permissions::FileSystemPath;
+use codex_protocol::permissions::FileSystemSandboxEntry;
+use codex_protocol::permissions::FileSystemSandboxPolicy;
+use codex_protocol::permissions::FileSystemSpecialPath;
 use codex_protocol::protocol::AskForApproval;
 use codex_protocol::protocol::EventMsg;
 use codex_protocol::protocol::Op;
+use codex_protocol::protocol::ReadOnlyAccess;
 use codex_protocol::protocol::SandboxPolicy;
 use codex_protocol::user_input::UserInput;
 use core_test_support::responses;
@@ -1146,7 +1153,10 @@ async fn view_image_tool_errors_when_path_is_directory() -> anyhow::Result<()> {
        .function_call_output_content_and_success(call_id)
        .and_then(|(content, _)| content)
        .expect("output text present");
-    let expected_message = format!("image path `{}` is not a file", abs_path.display());
+    let expected_message = format!(
+        r#"unable to read image file `{path}`: ProcessFailed {{ exit_code: 1, message: "error: `{path}` is not a regular file" }}"#,
+        path = abs_path.display()
+    );
    assert_eq!(output_text, expected_message);

    assert!(
@@ -1301,7 +1311,10 @@ async fn view_image_tool_errors_when_file_missing() -> anyhow::Result<()> {
        .function_call_output_content_and_success(call_id)
        .and_then(|(content, _)| content)
        .expect("output text present");
-    let expected_prefix = format!("unable to locate image at `{}`:", abs_path.display());
+    let expected_prefix = format!(
+        "unable to read image file `{path}`:",
+        path = abs_path.display()
+    );
    assert!(
        output_text.starts_with(&expected_prefix),
        "expected error to start with `{expected_prefix}` but got `{output_text}`"
@@ -1315,6 +1328,109 @@ async fn view_image_tool_errors_when_file_missing() -> anyhow::Result<()> {
    Ok(())
 }

+#[tokio::test(flavor = "multi_thread", worker_threads = 2)]
+async fn view_image_tool_respects_filesystem_sandbox() -> anyhow::Result<()> {
+    skip_if_no_network!(Ok(()));
+
+    let server = start_mock_server().await;
+    let sandbox_policy_for_config = SandboxPolicy::ReadOnly {
+        access: ReadOnlyAccess::Restricted {
+            include_platform_defaults: true,
+            readable_roots: Vec::new(),
+        },
+        network_access: false,
+    };
+    let mut builder = test_codex().with_config({
+        let sandbox_policy_for_config = sandbox_policy_for_config.clone();
+        move |config| {
+            config.permissions.sandbox_policy = Constrained::allow_any(sandbox_policy_for_config);
+            config.permissions.file_system_sandbox_policy =
+                FileSystemSandboxPolicy::restricted(vec![
+                    FileSystemSandboxEntry {
+                        path: FileSystemPath::Special {
+                            value: FileSystemSpecialPath::Minimal,
+                        },
+                        access: FileSystemAccessMode::Read,
+                    },
+                    FileSystemSandboxEntry {
+                        path: FileSystemPath::Special {
+                            value: FileSystemSpecialPath::CurrentWorkingDirectory,
+                        },
+                        access: FileSystemAccessMode::Read,
+                    },
+                ]);
+        }
+    });
+    let TestCodex {
+        codex,
+        config,
+        cwd,
+        session_configured,
+        ..
+    } = builder.build(&server).await?;
+
+    let outside_dir = tempfile::tempdir()?;
+    let abs_path = outside_dir.path().join("blocked.png");
+    let image = ImageBuffer::from_pixel(256, 128, Rgba([10u8, 20, 30, 255]));
+    image.save(&abs_path)?;
+
+    let call_id = "view-image-sandbox-denied";
+    let arguments = serde_json::json!({ "path": abs_path }).to_string();
+
+    let first_response = sse(vec![
+        ev_response_created("resp-1"),
+        ev_function_call(call_id, "view_image", &arguments),
+        ev_completed("resp-1"),
+    ]);
+    responses::mount_sse_once(&server, first_response).await;
+
+    let second_response = sse(vec![
+        ev_assistant_message("msg-1", "done"),
+        ev_completed("resp-2"),
+    ]);
+    let mock = responses::mount_sse_once(&server, second_response).await;
+
+    let session_model = session_configured.model.clone();
+
+    codex
+        .submit(Op::UserTurn {
+            items: vec![UserInput::Text {
+                text: "please attach the outside image".into(),
+                text_elements: Vec::new(),
+            }],
+            final_output_json_schema: None,
+            cwd: cwd.path().to_path_buf(),
+            approval_policy: AskForApproval::Never,
+            sandbox_policy: config.permissions.sandbox_policy.get().clone(),
+            model: session_model,
+            effort: None,
+            summary: None,
+            service_tier: None,
+            collaboration_mode: None,
+            personality: None,
+        })
+        .await?;
+
+    wait_for_event(&codex, |event| matches!(event, EventMsg::TurnComplete(_))).await;
+
+    let request = mock.single_request();
+    assert!(
+        request.inputs_of_type("input_image").is_empty(),
+        "sandbox-denied image should not produce an input_image message"
+    );
+    let output_text = request
+        .function_call_output_content_and_success(call_id)
+        .and_then(|(content, _)| content)
+        .expect("output text present");
+    let expected_prefix = format!("unable to read image file `{}`:", abs_path.display());
+    assert!(
+        output_text.starts_with(&expected_prefix),
+        "expected sandbox denial prefix `{expected_prefix}` but got `{output_text}`"
+    );
+
+    Ok(())
+}
+
 #[tokio::test(flavor = "multi_thread", worker_threads = 2)]
 async fn view_image_tool_returns_unsupported_message_for_text_only_model() -> anyhow::Result<()> {
    skip_if_no_network!(Ok(()));
--- a/codex-rs/fs-ops/BUILD.bazel
+++ b/codex-rs/fs-ops/BUILD.bazel
@@ -0,0 +1,6 @@
+load("//:defs.bzl", "codex_rust_crate")
+
+codex_rust_crate(
+    name = "fs-ops",
+    crate_name = "codex_fs_ops",
+)
--- a/codex-rs/fs-ops/Cargo.toml
+++ b/codex-rs/fs-ops/Cargo.toml
@@ -0,0 +1,16 @@
+[package]
+name = "codex-fs-ops"
+edition.workspace = true
+license.workspace = true
+version.workspace = true
+
+[lib]
+name = "codex_fs_ops"
+path = "src/lib.rs"
+
+[lints]
+workspace = true
+
+[dev-dependencies]
+pretty_assertions = { workspace = true }
+tempfile = { workspace = true }
--- a/codex-rs/fs-ops/src/command.rs
+++ b/codex-rs/fs-ops/src/command.rs
@@ -0,0 +1,41 @@
+use crate::constants::READ_FILE_OPERATION_ARG2;
+use std::ffi::OsString;
+use std::path::PathBuf;
+
+#[derive(Debug, Clone, PartialEq, Eq)]
+pub enum FsCommand {
+    ReadFile { path: PathBuf },
+    WriteFile { path: PathBuf },
+}
+
+pub fn parse_command_from_args(
+    mut args: impl Iterator<Item = OsString>,
+) -> Result<FsCommand, String> {
+    let Some(operation) = args.next() else {
+        return Err("missing operation".to_string());
+    };
+    let Some(operation) = operation.to_str() else {
+        return Err("operation must be valid UTF-8".to_string());
+    };
+    let Some(path) = args.next() else {
+        return Err(format!("missing path for operation `{operation}`"));
+    };
+    if args.next().is_some() {
+        return Err(format!(
+            "unexpected extra arguments for operation `{operation}`"
+        ));
+    }
+
+    let path = PathBuf::from(path);
+    match operation {
+        READ_FILE_OPERATION_ARG2 => Ok(FsCommand::ReadFile { path }),
+        "write" => Ok(FsCommand::WriteFile { path }),
+        _ => Err(format!(
+            "unsupported filesystem operation `{operation}`; expected `read` or `write`"
+        )),
+    }
+}
+
+#[cfg(test)]
+#[path = "command_tests.rs"]
+mod tests;
--- a/codex-rs/fs-ops/src/command_tests.rs
+++ b/codex-rs/fs-ops/src/command_tests.rs
@@ -0,0 +1,35 @@
+use super::FsCommand;
+use super::READ_FILE_OPERATION_ARG2;
+use super::parse_command_from_args;
+use pretty_assertions::assert_eq;
+
+#[test]
+fn parse_read_command() {
+    let command = parse_command_from_args(
+        [READ_FILE_OPERATION_ARG2, "/tmp/example.png"]
+            .into_iter()
+            .map(Into::into),
+    )
+    .expect("command should parse");
+
+    assert_eq!(
+        command,
+        FsCommand::ReadFile {
+            path: "/tmp/example.png".into(),
+        }
+    );
+}
+
+#[test]
+fn parse_write_command() {
+    let command =
+        parse_command_from_args(["write", "/tmp/example.png"].into_iter().map(Into::into))
+            .expect("command should parse");
+
+    assert_eq!(
+        command,
+        FsCommand::WriteFile {
+            path: "/tmp/example.png".into(),
+        }
+    );
+}
--- a/codex-rs/fs-ops/src/constants.rs
+++ b/codex-rs/fs-ops/src/constants.rs
@@ -0,0 +1,8 @@
+/// Special argv[1] flag used when the Codex executable self-invokes to run the
+/// internal sandbox-backed filesystem helper path.
+pub const CODEX_CORE_FS_OPS_ARG1: &str = "--codex-run-as-fs-ops";
+
+/// When passed as argv[2] to the Codex filesystem helper, it should be followed
+/// by a single path argument, and the helper will read the contents of the file
+/// at that path and write it to stdout.
+pub const READ_FILE_OPERATION_ARG2: &str = "read";
--- a/codex-rs/fs-ops/src/lib.rs
+++ b/codex-rs/fs-ops/src/lib.rs
@@ -0,0 +1,13 @@
+//! The codex-fs-ops crate provides a helper binary for performing various
+//! filesystem operations when `codex` is invoked with `--codex-run-as-fs-ops`
+//! as the first argument. By exposing this functionality via a CLI, this makes
+//! it possible to execute the CLI within a sandboxed context in order to ensure
+//! the filesystem restrictions of the sandbox are honored.
+
+mod command;
+mod constants;
+mod runner;
+
+pub use constants::CODEX_CORE_FS_OPS_ARG1;
+pub use constants::READ_FILE_OPERATION_ARG2;
+pub use runner::run_from_args_and_exit;
--- a/codex-rs/fs-ops/src/runner.rs
+++ b/codex-rs/fs-ops/src/runner.rs
@@ -0,0 +1,72 @@
+use crate::command::FsCommand;
+use crate::command::parse_command_from_args;
+use std::ffi::OsString;
+use std::io::Read;
+use std::io::Write;
+
+/// Runs the fs-ops helper with the given arguments and I/O streams.
+pub fn run_from_args_and_exit(
+    args: impl Iterator<Item = OsString>,
+    stdin: &mut impl Read,
+    stdout: &mut impl Write,
+    stderr: &mut impl Write,
+) -> ! {
+    let exit_code = match run_from_args(args, stdin, stdout, stderr) {
+        Ok(()) => 0,
+        Err(_) => {
+            // Discard the specific error, since we already wrote it to stderr.
+            1
+        }
+    };
+    std::process::exit(exit_code);
+}
+
+/// Testable version of `run_from_args_and_exit` that returns a Result instead
+/// of exiting the process.
+fn run_from_args(
+    args: impl Iterator<Item = OsString>,
+    stdin: &mut impl Read,
+    stdout: &mut impl Write,
+    stderr: &mut impl Write,
+) -> std::io::Result<()> {
+    try_run_from_args(args, stdin, stdout).inspect_err(|error| {
+        writeln!(stderr, "error: {error}").ok();
+    })
+}
+
+fn try_run_from_args(
+    args: impl Iterator<Item = OsString>,
+    stdin: &mut impl Read,
+    stdout: &mut impl Write,
+) -> std::io::Result<()> {
+    let command = parse_command_from_args(args)
+        .map_err(|error| std::io::Error::new(std::io::ErrorKind::InvalidInput, error))?;
+
+    match command {
+        FsCommand::ReadFile { path } => {
+            let mut file = std::fs::File::open(&path)?;
+            if !file.metadata()?.is_file() {
+                let error_message = format!(
+                    "`{path}` is not a regular file",
+                    path = path.to_string_lossy()
+                );
+                return Err(std::io::Error::new(
+                    std::io::ErrorKind::InvalidInput,
+                    error_message,
+                ));
+            }
+
+            std::io::copy(&mut file, stdout).map(|_| ())
+        }
+        FsCommand::WriteFile { path } => {
+            let mut file = std::fs::File::create(path).map_err(FsError::from)?;
+            std::io::copy(stdin, &mut file)
+                .map(|_| ())
+                .map_err(FsError::from)
+        }
+    }
+}
+
+#[cfg(test)]
+#[path = "runner_tests.rs"]
+mod tests;
--- a/codex-rs/fs-ops/src/runner_tests.rs
+++ b/codex-rs/fs-ops/src/runner_tests.rs
@@ -0,0 +1,160 @@
+use super::run_from_args;
+use crate::READ_FILE_OPERATION_ARG2;
+use pretty_assertions::assert_eq;
+use std::io::Cursor;
+use tempfile::tempdir;
+
+#[test]
+fn run_from_args_streams_file_bytes_to_stdout() {
+    let tempdir = tempdir().expect("tempdir");
+    let path = tempdir.path().join("image.bin");
+    let expected = b"hello\x00world".to_vec();
+    std::fs::write(&path, &expected).expect("write test file");
+
+    let mut stdin = std::io::empty();
+    let mut stdout = Vec::new();
+    let mut stderr = Vec::new();
+    run_from_args(
+        [
+            READ_FILE_OPERATION_ARG2,
+            path.to_str().expect("utf-8 test path"),
+        ]
+        .into_iter()
+        .map(Into::into),
+        &mut stdin,
+        &mut stdout,
+        &mut stderr,
+    )
+    .expect("read should succeed");
+
+    assert_eq!(stdout, expected);
+    assert_eq!(stderr, Vec::<u8>::new());
+}
+
+#[test]
+#[cfg(unix)]
+fn rejects_path_that_is_not_a_regular_file() {
+    let path = std::path::PathBuf::from("/dev/zero");
+
+    let mut stdin = std::io::empty();
+    let mut stdout = Vec::new();
+    let mut stderr = Vec::new();
+    let error = run_from_args(
+        [
+            READ_FILE_OPERATION_ARG2,
+            path.to_str().expect("utf-8 test path"),
+        ]
+        .into_iter()
+        .map(Into::into),
+        &mut stdin,
+        &mut stdout,
+        &mut stderr,
+    )
+    .expect_err(
+        r#"reading a non-regular file should fail or else
+the user risks hanging the process by trying
+to read from something like /dev/zero"#,
+    );
+
+    assert_eq!(error.kind(), std::io::ErrorKind::InvalidInput);
+    assert_eq!(stdout, Vec::<u8>::new());
+    assert_eq!(
+        "error: `/dev/zero` is not a regular file\n",
+        String::from_utf8_lossy(&stderr),
+    );
+}
+
+#[test]
+fn read_reports_directory_error() {
+    let tempdir = tempdir().expect("tempdir");
+    let mut stdin = std::io::empty();
+    let mut stdout = Vec::new();
+    let mut stderr = Vec::new();
+
+    let error = run_from_args(
+        [
+            READ_FILE_OPERATION_ARG2,
+            tempdir.path().to_str().expect("utf-8 test path"),
+        ]
+        .into_iter()
+        .map(Into::into),
+        &mut stdin,
+        &mut stdout,
+        &mut stderr,
+    )
+    .expect_err("reading a directory should fail");
+
+    #[cfg(not(windows))]
+    assert_eq!(error.kind(), std::io::ErrorKind::InvalidInput);
+    #[cfg(windows)]
+    assert_eq!(error.kind(), std::io::ErrorKind::PermissionDenied);
+}
+
+#[test]
+fn run_from_args_serializes_errors_to_stderr() {
+    let tempdir = tempdir().expect("tempdir");
+    let missing = tempdir.path().join("missing.txt");
+    let mut stdin = std::io::empty();
+    let mut stdout = Vec::new();
+    let mut stderr = Vec::new();
+
+    let result = run_from_args(
+        [
+            READ_FILE_OPERATION_ARG2,
+            missing.to_str().expect("utf-8 test path"),
+        ]
+        .into_iter()
+        .map(Into::into),
+        &mut stdin,
+        &mut stdout,
+        &mut stderr,
+    );
+
+    assert!(result.is_err(), "missing file should fail");
+    assert_eq!(stdout, Vec::<u8>::new());
+}
+
+#[test]
+fn run_from_args_streams_stdin_bytes_to_file() {
+    let tempdir = tempdir().expect("tempdir");
+    let path = tempdir.path().join("image.bin");
+    let expected = b"hello\x00world".to_vec();
+
+    let mut stdin = Cursor::new(expected.clone());
+    let mut stdout = Vec::new();
+    let mut stderr = Vec::new();
+    run_from_args(
+        ["write", path.to_str().expect("utf-8 test path")]
+            .into_iter()
+            .map(Into::into),
+        &mut stdin,
+        &mut stdout,
+        &mut stderr,
+    )
+    .expect("write should succeed");
+
+    assert_eq!(std::fs::read(&path).expect("read test file"), expected);
+    assert_eq!(stdout, Vec::<u8>::new());
+    assert_eq!(stderr, Vec::<u8>::new());
+}
+
+#[test]
+fn write_reports_directory_error() {
+    let tempdir = tempdir().expect("tempdir");
+    let mut stdin = Cursor::new(b"hello world".to_vec());
+    let mut stdout = Vec::new();
+
+    let error = execute(
+        FsCommand::WriteFile {
+            path: tempdir.path().to_path_buf(),
+        },
+        &mut stdin,
+        &mut stdout,
+    )
+    .expect_err("writing to a directory should fail");
+
+    #[cfg(target_os = "windows")]
+    assert_eq!(error.kind, FsErrorKind::PermissionDenied);
+    #[cfg(not(target_os = "windows"))]
+    assert_eq!(error.kind, FsErrorKind::IsADirectory);
+}
--- a/codex-rs/windows-sandbox-rs/src/elevated_impl.rs
+++ b/codex-rs/windows-sandbox-rs/src/elevated_impl.rs
@@ -209,6 +209,7 @@ mod windows_impl {
        command: Vec<String>,
        cwd: &Path,
        mut env_map: HashMap<String, String>,
+        stdin_bytes: Option<Vec<u8>>,
        timeout_ms: Option<u64>,
        use_private_desktop: bool,
    ) -> Result<CaptureResult> {
@@ -383,13 +384,26 @@ mod windows_impl {
                        cap_sids,
                        timeout_ms,
                        tty: false,
-                        stdin_open: false,
+                        stdin_open: stdin_bytes.is_some(),
                        use_private_desktop,
                    }),
                },
            };
            write_frame(&mut pipe_write, &spawn_request)?;
            read_spawn_ready(&mut pipe_read)?;
+            if let Some(stdin_bytes) = stdin_bytes {
+                write_frame(
+                    &mut pipe_write,
+                    &FramedMessage {
+                        version: 1,
+                        message: Message::Stdin {
+                            payload: crate::ipc_framed::StdinPayload {
+                                data_b64: crate::ipc_framed::encode_bytes(&stdin_bytes),
+                            },
+                        },
+                    },
+                )?;
+            }
            drop(pipe_write);

            let mut stdout = Vec::new();
@@ -503,6 +517,7 @@ mod stub {
        _command: Vec<String>,
        _cwd: &Path,
        _env_map: HashMap<String, String>,
+        _stdin_bytes: Option<Vec<u8>>,
        _timeout_ms: Option<u64>,
        _use_private_desktop: bool,
    ) -> Result<CaptureResult> {
--- a/codex-rs/windows-sandbox-rs/src/lib.rs
+++ b/codex-rs/windows-sandbox-rs/src/lib.rs
@@ -265,6 +265,7 @@ mod windows_impl {
        command: Vec<String>,
        cwd: &Path,
        mut env_map: HashMap<String, String>,
+        stdin_bytes: Option<Vec<u8>>,
        timeout_ms: Option<u64>,
        use_private_desktop: bool,
    ) -> Result<CaptureResult> {
@@ -406,7 +407,30 @@ mod windows_impl {

        unsafe {
            CloseHandle(in_r);
-            // Close the parent's stdin write end so the child sees EOF immediately.
+            if let Some(stdin_bytes) = stdin_bytes {
+                let mut offset = 0;
+                while offset < stdin_bytes.len() {
+                    let remaining = stdin_bytes.len() - offset;
+                    let chunk_len = remaining.min(u32::MAX as usize);
+                    let mut written: u32 = 0;
+                    let ok = windows_sys::Win32::Storage::FileSystem::WriteFile(
+                        in_w,
+                        stdin_bytes[offset..offset + chunk_len].as_ptr(),
+                        chunk_len as u32,
+                        &mut written,
+                        std::ptr::null_mut(),
+                    );
+                    if ok == 0 {
+                        CloseHandle(in_w);
+                        CloseHandle(out_w);
+                        CloseHandle(err_w);
+                        CloseHandle(pi.hThread);
+                        CloseHandle(pi.hProcess);
+                        return Err(std::io::Error::from_raw_os_error(GetLastError() as i32).into());
+                    }
+                    offset += written as usize;
+                }
+            }
            CloseHandle(in_w);
            CloseHandle(out_w);
            CloseHandle(err_w);
@@ -615,6 +639,7 @@ mod stub {
        _command: Vec<String>,
        _cwd: &Path,
        _env_map: HashMap<String, String>,
+        _stdin_bytes: Option<Vec<u8>>,
        _timeout_ms: Option<u64>,
        _use_private_desktop: bool,
    ) -> Result<CaptureResult> {
Author	SHA1	Message	Date
Michael Bolin	3aaee0f061	core: add stdin-backed sandboxed fs writes	2026-03-20 15:32:27 -07:00
Michael Bolin	86d00c0236	core: route view_image through a sandbox-backed fs helper	2026-03-20 15:32:26 -07:00
Michael Bolin	f31d388ac0	core: add a sandbox-backed fs helper	2026-03-20 15:19:33 -07:00