diff --git a/AGENTS.md b/AGENTS.md
index aaebd0dfd..f9f04c5b1 100644
--- a/AGENTS.md
+++ b/AGENTS.md
@@ -75,6 +75,7 @@ If you don’t have the tool:
 ### Test assertions
 
 - Tests should use pretty_assertions::assert_eq for clearer diffs. Import this at the top of the test module if it isn't already.
+- Prefer deep equals comparisons whenever possible. Perform `assert_eq!()` on entire objects, rather than individual fields.
 
 ### Integration tests (core)
 
diff --git a/codex-rs/core/src/shell.rs b/codex-rs/core/src/shell.rs
index ac115facb..2338f41cd 100644
--- a/codex-rs/core/src/shell.rs
+++ b/codex-rs/core/src/shell.rs
@@ -408,6 +408,48 @@ mod tests {
         }
     }
 
+    #[test]
+    fn derive_exec_args() {
+        let test_bash_shell = Shell {
+            shell_type: ShellType::Bash,
+            shell_path: PathBuf::from("/bin/bash"),
+        };
+        assert_eq!(
+            test_bash_shell.derive_exec_args("echo hello", false),
+            vec!["/bin/bash", "-c", "echo hello"]
+        );
+        assert_eq!(
+            test_bash_shell.derive_exec_args("echo hello", true),
+            vec!["/bin/bash", "-lc", "echo hello"]
+        );
+
+        let test_zsh_shell = Shell {
+            shell_type: ShellType::Zsh,
+            shell_path: PathBuf::from("/bin/zsh"),
+        };
+        assert_eq!(
+            test_zsh_shell.derive_exec_args("echo hello", false),
+            vec!["/bin/zsh", "-c", "echo hello"]
+        );
+        assert_eq!(
+            test_zsh_shell.derive_exec_args("echo hello", true),
+            vec!["/bin/zsh", "-lc", "echo hello"]
+        );
+
+        let test_powershell_shell = Shell {
+            shell_type: ShellType::PowerShell,
+            shell_path: PathBuf::from("pwsh.exe"),
+        };
+        assert_eq!(
+            test_powershell_shell.derive_exec_args("echo hello", false),
+            vec!["pwsh.exe", "-NoProfile", "-Command", "echo hello"]
+        );
+        assert_eq!(
+            test_powershell_shell.derive_exec_args("echo hello", true),
+            vec!["pwsh.exe", "-Command", "echo hello"]
+        );
+    }
+
     #[tokio::test]
     async fn test_current_shell_detects_zsh() {
         let shell = Command::new("sh")
diff --git a/codex-rs/core/src/tools/handlers/shell.rs b/codex-rs/core/src/tools/handlers/shell.rs
index cd05d126b..c3ef590e1 100644
--- a/codex-rs/core/src/tools/handlers/shell.rs
+++ b/codex-rs/core/src/tools/handlers/shell.rs
@@ -49,8 +49,7 @@ impl ShellCommandHandler {
         turn_context: &TurnContext,
     ) -> ExecParams {
         let shell = session.user_shell();
-        let use_login_shell = true;
-        let command = shell.derive_exec_args(&params.command, use_login_shell);
+        let command = shell.derive_exec_args(&params.command, params.login.unwrap_or(true));
 
         ExecParams {
             command,
@@ -276,9 +275,15 @@ impl ShellHandler {
 mod tests {
     use std::path::PathBuf;
 
+    use codex_protocol::models::ShellCommandToolCallParams;
+    use pretty_assertions::assert_eq;
+
+    use crate::codex::make_session_and_context;
+    use crate::exec_env::create_env;
     use crate::is_safe_command::is_known_safe_command;
     use crate::shell::Shell;
     use crate::shell::ShellType;
+    use crate::tools::handlers::ShellCommandHandler;
 
     /// The logic for is_known_safe_command() has heuristics for known shells,
     /// so we must ensure the commands generated by [ShellCommandHandler] can be
@@ -312,4 +317,43 @@ mod tests {
             &shell.derive_exec_args(command, /* use_login_shell */ false)
         ));
     }
+
+    #[test]
+    fn shell_command_handler_to_exec_params_uses_session_shell_and_turn_context() {
+        let (session, turn_context) = make_session_and_context();
+
+        let command = "echo hello".to_string();
+        let workdir = Some("subdir".to_string());
+        let login = None;
+        let timeout_ms = Some(1234);
+        let with_escalated_permissions = Some(true);
+        let justification = Some("because tests".to_string());
+
+        let expected_command = session.user_shell().derive_exec_args(&command, true);
+        let expected_cwd = turn_context.resolve_path(workdir.clone());
+        let expected_env = create_env(&turn_context.shell_environment_policy);
+
+        let params = ShellCommandToolCallParams {
+            command,
+            workdir,
+            login,
+            timeout_ms,
+            with_escalated_permissions,
+            justification: justification.clone(),
+        };
+
+        let exec_params = ShellCommandHandler::to_exec_params(params, &session, &turn_context);
+
+        // ExecParams cannot derive Eq due to the CancellationToken field, so we manually compare the fields.
+        assert_eq!(exec_params.command, expected_command);
+        assert_eq!(exec_params.cwd, expected_cwd);
+        assert_eq!(exec_params.env, expected_env);
+        assert_eq!(exec_params.expiration.timeout_ms(), timeout_ms);
+        assert_eq!(
+            exec_params.with_escalated_permissions,
+            with_escalated_permissions
+        );
+        assert_eq!(exec_params.justification, justification);
+        assert_eq!(exec_params.arg0, None);
+    }
 }
diff --git a/codex-rs/core/src/tools/spec.rs b/codex-rs/core/src/tools/spec.rs
index a36f54a6b..e72becd88 100644
--- a/codex-rs/core/src/tools/spec.rs
+++ b/codex-rs/core/src/tools/spec.rs
@@ -331,6 +331,15 @@ fn create_shell_command_tool() -> ToolSpec {
             description: Some("The working directory to execute the command in".to_string()),
         },
     );
+    properties.insert(
+        "login".to_string(),
+        JsonSchema::Boolean {
+            description: Some(
+                "Whether to run the shell with login shell semantics. Defaults to true."
+                    .to_string(),
+            ),
+        },
+    );
     properties.insert(
         "timeout_ms".to_string(),
         JsonSchema::Number {
diff --git a/codex-rs/core/tests/common/lib.rs b/codex-rs/core/tests/common/lib.rs
index e7b1e71ef..2c8c28d71 100644
--- a/codex-rs/core/tests/common/lib.rs
+++ b/codex-rs/core/tests/common/lib.rs
@@ -369,3 +369,15 @@ macro_rules! skip_if_no_network {
         }
     }};
 }
+
+#[macro_export]
+macro_rules! skip_if_windows {
+    ($return_value:expr $(,)?) => {{
+        if cfg!(target_os = "windows") {
+            println!(
+                "Skipping test because it cannot execute when network is disabled in a Codex sandbox."
+            );
+            return $return_value;
+        }
+    }};
+}
diff --git a/codex-rs/core/tests/suite/mod.rs b/codex-rs/core/tests/suite/mod.rs
index 86f417801..e2d78004a 100644
--- a/codex-rs/core/tests/suite/mod.rs
+++ b/codex-rs/core/tests/suite/mod.rs
@@ -46,6 +46,7 @@ mod review;
 mod rmcp_client;
 mod rollout_list_find;
 mod seatbelt;
+mod shell_command;
 mod shell_serialization;
 mod stream_error_allows_next_turn;
 mod stream_no_completed;
diff --git a/codex-rs/core/tests/suite/shell_command.rs b/codex-rs/core/tests/suite/shell_command.rs
new file mode 100644
index 000000000..10e972b3d
--- /dev/null
+++ b/codex-rs/core/tests/suite/shell_command.rs
@@ -0,0 +1,174 @@
+use anyhow::Result;
+use core_test_support::assert_regex_match;
+use core_test_support::responses::ev_assistant_message;
+use core_test_support::responses::ev_completed;
+use core_test_support::responses::ev_function_call;
+use core_test_support::responses::ev_response_created;
+use core_test_support::responses::mount_sse_sequence;
+use core_test_support::responses::sse;
+use core_test_support::skip_if_no_network;
+use core_test_support::skip_if_windows;
+use core_test_support::test_codex::TestCodexBuilder;
+use core_test_support::test_codex::TestCodexHarness;
+use core_test_support::test_codex::test_codex;
+use serde_json::json;
+
+fn shell_responses(call_id: &str, command: &str, login: Option<bool>) -> Vec<String> {
+    let args = json!({
+        "command": command,
+        "timeout_ms": 2_000,
+        "login": login,
+    });
+
+    #[allow(clippy::expect_used)]
+    let arguments = serde_json::to_string(&args).expect("serialize shell command arguments");
+
+    vec![
+        sse(vec![
+            ev_response_created("resp-1"),
+            ev_function_call(call_id, "shell_command", &arguments),
+            ev_completed("resp-1"),
+        ]),
+        sse(vec![
+            ev_assistant_message("msg-1", "done"),
+            ev_completed("resp-2"),
+        ]),
+    ]
+}
+
+async fn shell_command_harness_with(
+    configure: impl FnOnce(TestCodexBuilder) -> TestCodexBuilder,
+) -> Result<TestCodexHarness> {
+    let builder = configure(test_codex()).with_config(|config| {
+        config.include_apply_patch_tool = true;
+    });
+    TestCodexHarness::with_builder(builder).await
+}
+
+async fn mount_shell_responses(
+    harness: &TestCodexHarness,
+    call_id: &str,
+    command: &str,
+    login: Option<bool>,
+) {
+    mount_sse_sequence(harness.server(), shell_responses(call_id, command, login)).await;
+}
+
+fn assert_shell_command_output(output: &str, expected: &str) -> Result<()> {
+    let normalized_output = output
+        .replace("\r\n", "\n")
+        .replace('\r', "\n")
+        .trim_end_matches('\n')
+        .to_string();
+
+    let expected_pattern = format!(
+        r"(?s)^Exit code: 0\nWall time: [0-9]+(?:\.[0-9]+)? seconds\nOutput:\n{expected}\n?$"
+    );
+
+    assert_regex_match(&expected_pattern, &normalized_output);
+    Ok(())
+}
+
+#[tokio::test(flavor = "multi_thread", worker_threads = 2)]
+async fn shell_command_works() -> anyhow::Result<()> {
+    skip_if_no_network!(Ok(()));
+
+    let harness = shell_command_harness_with(|builder| builder.with_model("gpt-5.1")).await?;
+
+    let call_id = "shell-command-call";
+    mount_shell_responses(&harness, call_id, "echo 'hello, world'", None).await;
+    harness.submit("run the echo command").await?;
+
+    let output = harness.function_call_stdout(call_id).await;
+    assert_shell_command_output(&output, "hello, world")?;
+
+    Ok(())
+}
+
+#[tokio::test(flavor = "multi_thread", worker_threads = 2)]
+async fn output_with_login() -> anyhow::Result<()> {
+    skip_if_no_network!(Ok(()));
+
+    let harness = shell_command_harness_with(|builder| builder.with_model("gpt-5.1")).await?;
+
+    let call_id = "shell-command-call-login-true";
+    mount_shell_responses(&harness, call_id, "echo 'hello, world'", Some(true)).await;
+    harness.submit("run the echo command with login").await?;
+
+    let output = harness.function_call_stdout(call_id).await;
+    assert_shell_command_output(&output, "hello, world")?;
+
+    Ok(())
+}
+
+#[tokio::test(flavor = "multi_thread", worker_threads = 2)]
+async fn output_without_login() -> anyhow::Result<()> {
+    skip_if_no_network!(Ok(()));
+
+    let harness = shell_command_harness_with(|builder| builder.with_model("gpt-5.1")).await?;
+
+    let call_id = "shell-command-call-login-false";
+    mount_shell_responses(&harness, call_id, "echo 'hello, world'", Some(false)).await;
+    harness.submit("run the echo command without login").await?;
+
+    let output = harness.function_call_stdout(call_id).await;
+    assert_shell_command_output(&output, "hello, world")?;
+
+    Ok(())
+}
+
+#[tokio::test(flavor = "multi_thread", worker_threads = 2)]
+async fn multi_line_output_with_login() -> anyhow::Result<()> {
+    skip_if_no_network!(Ok(()));
+
+    let harness = shell_command_harness_with(|builder| builder.with_model("gpt-5.1")).await?;
+
+    let call_id = "shell-command-call-first-extra-login";
+    mount_shell_responses(
+        &harness,
+        call_id,
+        "echo 'first line\nsecond line'",
+        Some(true),
+    )
+    .await;
+    harness.submit("run the command with login").await?;
+
+    let output = harness.function_call_stdout(call_id).await;
+    assert_shell_command_output(&output, "first line\nsecond line")?;
+
+    Ok(())
+}
+
+#[tokio::test(flavor = "multi_thread", worker_threads = 2)]
+async fn pipe_output_with_login() -> anyhow::Result<()> {
+    skip_if_no_network!(Ok(()));
+    skip_if_windows!(Ok(()));
+
+    let harness = shell_command_harness_with(|builder| builder.with_model("gpt-5.1")).await?;
+
+    let call_id = "shell-command-call-second-extra-no-login";
+    mount_shell_responses(&harness, call_id, "echo 'hello, world' | cat", None).await;
+    harness.submit("run the command without login").await?;
+
+    let output = harness.function_call_stdout(call_id).await;
+    assert_shell_command_output(&output, "hello, world")?;
+
+    Ok(())
+}
+
+#[tokio::test(flavor = "multi_thread", worker_threads = 2)]
+async fn pipe_output_without_login() -> anyhow::Result<()> {
+    skip_if_no_network!(Ok(()));
+    skip_if_windows!(Ok(()));
+
+    let harness = shell_command_harness_with(|builder| builder.with_model("gpt-5.1")).await?;
+
+    let call_id = "shell-command-call-third-extra-login-false";
+    mount_shell_responses(&harness, call_id, "echo 'hello, world' | cat", Some(false)).await;
+    harness.submit("run the command without login").await?;
+
+    let output = harness.function_call_stdout(call_id).await;
+    assert_shell_command_output(&output, "hello, world")?;
+
+    Ok(())
+}
diff --git a/codex-rs/protocol/src/models.rs b/codex-rs/protocol/src/models.rs
index daf98152d..f93c157b7 100644
--- a/codex-rs/protocol/src/models.rs
+++ b/codex-rs/protocol/src/models.rs
@@ -348,6 +348,9 @@ pub struct ShellCommandToolCallParams {
     pub command: String,
     pub workdir: Option<String>,
 
+    /// Whether to run the shell with login shell semantics
+    #[serde(skip_serializing_if = "Option::is_none")]
+    pub login: Option<bool>,
     /// This is the maximum time in milliseconds that the command is allowed to run.
     #[serde(alias = "timeout")]
     pub timeout_ms: Option<u64>,