diff --git a/codex-rs/tui/tests/message_layout.rs b/codex-rs/tui/tests/message_layout.rs
new file mode 100644
index 0000000000..7919b76e3a
--- /dev/null
+++ b/codex-rs/tui/tests/message_layout.rs
@@ -0,0 +1,128 @@
+use tempfile::TempDir;
+use codex_core::config::{Config, ConfigToml, ConfigOverrides};
+use codex_tui::history_cell::HistoryCell;
+
+/// Extract plain string content of each line for comparison.
+fn lines_from_userprompt(view: &codex_tui::text_block::TextBlock) -> Vec<String> {
+    view.lines
+        .iter()
+        .map(|line| line.spans.iter().map(|s| s.content.clone()).collect())
+        .collect()
+}
+
+#[test]
+fn test_user_message_layout_combinations() {
+    let tmp = TempDir::new().unwrap();
+    let mut config = Config::load_from_base_config_with_overrides(
+        ConfigToml::default(),
+        ConfigOverrides::default(),
+        tmp.path().to_path_buf(),
+    )
+    .unwrap();
+    let message = "first line\nsecond line".to_string();
+    for &sender_break in &[false, true] {
+        for &message_spacing in &[false, true] {
+            config.tui.sender_break_line = sender_break;
+            config.tui.message_spacing = message_spacing;
+            let cell = HistoryCell::new_user_prompt(&config, message.clone());
+            let view = match cell {
+                HistoryCell::UserPrompt { view } => view,
+                _ => panic!("expected UserPrompt variant"),
+            };
+            let got = lines_from_userprompt(&view);
+            let mut expected = Vec::new();
+            if sender_break {
+                expected.push("user".to_string());
+                expected.push("first line".to_string());
+                expected.push("second line".to_string());
+            } else {
+                expected.push("user first line".to_string());
+                expected.push(" second line".to_string());
+            }
+            if message_spacing {
+                expected.push(String::new());
+            }
+            assert_eq!(got, expected,
+                "Layout mismatch for sender_break_line={}, message_spacing={}",
+                sender_break, message_spacing);
+        }
+    }
+}
+
+#[test]
+fn test_agent_message_layout_combinations() {
+    let tmp = TempDir::new().unwrap();
+    let mut config = Config::load_from_base_config_with_overrides(
+        ConfigToml::default(),
+        ConfigOverrides::default(),
+        tmp.path().to_path_buf(),
+    )
+    .unwrap();
+    let message = "first line\nsecond line".to_string();
+    for &sender_break in &[false, true] {
+        for &message_spacing in &[false, true] {
+            config.tui.sender_break_line = sender_break;
+            config.tui.message_spacing = message_spacing;
+            let cell = HistoryCell::new_agent_message(&config, message.clone());
+            let view = match cell {
+                HistoryCell::AgentMessage { view } => view,
+                _ => panic!("expected AgentMessage variant"),
+            };
+            let got = lines_from_userprompt(&view);
+            let mut expected = Vec::new();
+            if sender_break {
+                expected.push("codex".to_string());
+                expected.push("first line".to_string());
+                expected.push("second line".to_string());
+            } else {
+                expected.push("codex first line".to_string());
+                expected.push(" second line".to_string());
+            }
+            if message_spacing {
+                expected.push(String::new());
+            }
+            assert_eq!(got, expected,
+                "Agent layout mismatch for sender_break_line={}, message_spacing={}",
+                sender_break, message_spacing);
+        }
+    }
+}
+
+#[test]
+fn test_agent_reasoning_layout_combinations() {
+    let tmp = TempDir::new().unwrap();
+    let mut config = Config::load_from_base_config_with_overrides(
+        ConfigToml::default(),
+        ConfigOverrides::default(),
+        tmp.path().to_path_buf(),
+    )
+    .unwrap();
+    let message = "first line\nsecond line".to_string();
+    for &sender_break in &[false, true] {
+        for &message_spacing in &[false, true] {
+            config.tui.sender_break_line = sender_break;
+            config.tui.message_spacing = message_spacing;
+            let cell = HistoryCell::new_agent_reasoning(&config, message.clone());
+            let view = match cell {
+                HistoryCell::AgentReasoning { view } => view,
+                _ => panic!("expected AgentReasoning variant"),
+            };
+            let got = lines_from_userprompt(&view);
+            let mut expected = Vec::new();
+            if sender_break {
+                expected.push("thinking".to_string());
+                expected.push("first line".to_string());
+                expected.push("second line".to_string());
+            } else {
+                expected.push("thinking first line".to_string());
+                expected.push(" second line".to_string());
+            }
+            if message_spacing {
+                expected.push(String::new());
+            }
+            assert_eq!(got, expected,
+                "Reasoning layout mismatch for sender_break_line={}, message_spacing={}",
+                sender_break, message_spacing);
+        }
+    }
+}