Limit background terminal input previews (#41937)

## Why Large input sent to a background terminal can require excessive wrapping work and fill the inline history view. ## What changed - Limit inline input previews to 12 rendered rows and bound preview processing to 64 KiB. - Show a transcript hint when input is omitted, while preserving the complete input in transcript and raw views. - Keep URLs intact when they fit and truncate only the final overflowing line when needed. ## Testing Add regression coverage for long wrapped input, narrow viewports, zero-width Unicode payloads, URLs, and inputs that fit within the preview budget. GitOrigin-RevId: c20edf156d5c8364083b1690e41cabd29786a279
copyberry · Aug 31, 2026 · Aug 31, 2026 · Aug 31, 2026 · 115ffaf8bf1eda460526605cf44d9a96d88f4371
commit 115ffaf8bf1eda460526605cf44d9a96d88f4371
diff --git a/codex-rs/tui/src/history_cell/exec.rs b/codex-rs/tui/src/history_cell/exec.rs
@@ -1,7 +1,12 @@
-//! Background terminal interaction and process-summary history cells.
+//! Background terminal history cells, with bounded inline input and full transcript views.
 
 use super::*;
+use crate::line_truncation::truncate_line_to_width;
 use crate::width::display_width;
+use crate::wrapping::word_wrap_lines;
+
+const INPUT_PREVIEW_ROWS: usize = 12;
+const INPUT_PREVIEW_BYTES: usize = 64 * 1024;
 
 #[derive(Debug)]
 pub(crate) struct UnifiedExecInteractionCell {
@@ -16,10 +21,8 @@ impl UnifiedExecInteractionCell {
             stdin,
         }
     }
-}
 
-impl HistoryCell for UnifiedExecInteractionCell {
-    fn display_lines(&self, width: u16) -> Vec<Line<'static>> {
+    fn render_lines(&self, width: u16, max_input_rows: usize) -> Vec<Line<'static>> {
         if width == 0 {
             return Vec::new();
         }
@@ -47,21 +50,62 @@ impl HistoryCell for UnifiedExecInteractionCell {
             return out;
         }
 
-        let input_lines: Vec<Line<'static>> = self
-            .stdin
-            .lines()
-            .map(|line| Line::from(line.to_string()))
-            .collect();
-
-        let input_wrapped = adaptive_wrap_lines(
-            input_lines,
-            RtOptions::new(wrap_width)
-                .initial_indent(Line::from("  └ ".dim()))
-                .subsequent_indent(Line::from("    ".dim())),
-        );
-        out.extend(input_wrapped);
+        // Limit work before wrapping, including payloads with no newlines or visible width.
+        let input = if max_input_rows == usize::MAX {
+            self.stdin.as_str()
+        } else {
+            &self.stdin[..self.stdin.floor_char_boundary(INPUT_PREVIEW_BYTES)]
+        };
+        let input_lines = input.lines().take(max_input_rows.saturating_add(1));
+        let options = RtOptions::new(wrap_width)
+            .initial_indent(Line::from("  └ ".dim()))
+            .subsequent_indent(Line::from("    ".dim()));
+
+        let mut remaining_rows = max_input_rows;
+        let mut omitted = input.len() < self.stdin.len();
+        for line in adaptive_wrap_lines(input_lines, options) {
+            if max_input_rows != usize::MAX {
+                let rows = Paragraph::new(line.clone())
+                    .wrap(Wrap { trim: false })
+                    .line_count(width);
+                if rows > remaining_rows {
+                    // Keep fitting URLs intact; shorten only the overflowing final line.
+                    out.extend(
+                        word_wrap_lines([line], wrap_width)
+                            .into_iter()
+                            .take(remaining_rows)
+                            // Control sequences differ in textwrap and ratatui width.
+                            .map(|line| truncate_line_to_width(line, wrap_width)),
+                    );
+                    omitted = true;
+                    break;
+                }
+                remaining_rows -= rows;
+            }
+            out.push(line);
+        }
+        if omitted {
+            out.push(
+                format!(
+                    "  … Input preview limited ({}).",
+                    crate::ui_consts::TRANSCRIPT_HINT
+                )
+                .dim()
+                .into(),
+            );
+        }
         out
     }
+}
+
+impl HistoryCell for UnifiedExecInteractionCell {
+    fn display_lines(&self, width: u16) -> Vec<Line<'static>> {
+        self.render_lines(width, INPUT_PREVIEW_ROWS)
+    }
+
+    fn transcript_lines(&self, width: u16) -> Vec<Line<'static>> {
+        self.render_lines(width, usize::MAX)
+    }
 
     fn raw_lines(&self) -> Vec<Line<'static>> {
         let mut out = Vec::new();
@@ -96,6 +140,10 @@ impl HistoryCell for UnifiedExecInteractionCell {
     }
 }
 
+#[cfg(test)]
+#[path = "exec_tests.rs"]
+mod tests;
+
 pub(crate) fn new_unified_exec_interaction(
     command_display: Option<String>,
     stdin: String,

diff --git a/codex-rs/tui/src/history_cell/exec_tests.rs b/codex-rs/tui/src/history_cell/exec_tests.rs
@@ -0,0 +1,139 @@
+//! Regression coverage for bounded background-terminal input previews.
+
+use super::*;
+use pretty_assertions::assert_eq;
+
+#[test]
+fn unified_exec_input_preview_limits_wrapped_payload() {
+    let input = "abcdefghijklmnopqrstuvwxyz0123456789".repeat(/*n*/ 2_000);
+    let cell = new_unified_exec_interaction(Some("cat".to_string()), input.clone());
+    let preview = cell.display_lines(/*width*/ 40);
+    insta::assert_snapshot!(
+        preview.iter().map(ToString::to_string).collect::<Vec<_>>().join("\n"),
+        @"
+    ↳ Interacted with background terminal ·
+    cat
+      └ abcdefghijklmnopqrstuvwxyz0123456789
+        abcdefghijklmnopqrstuvwxyz0123456789
+        abcdefghijklmnopqrstuvwxyz0123456789
+        abcdefghijklmnopqrstuvwxyz0123456789
+        abcdefghijklmnopqrstuvwxyz0123456789
+        abcdefghijklmnopqrstuvwxyz0123456789
+        abcdefghijklmnopqrstuvwxyz0123456789
+        abcdefghijklmnopqrstuvwxyz0123456789
+        abcdefghijklmnopqrstuvwxyz0123456789
+        abcdefghijklmnopqrstuvwxyz0123456789
+        abcdefghijklmnopqrstuvwxyz0123456789
+        abcdefghijklmnopqrstuvwxyz0123456789
+      … Input preview limited (ctrl + t to view transcript).
+    ",
+    );
+    assert_eq!(
+        cell.raw_lines(),
+        vec![
+            Line::from("Interacted with background terminal: cat"),
+            Line::from(input.clone()),
+        ],
+    );
+    let transcript = cell.transcript_lines(/*width*/ 40);
+    assert_eq!(
+        transcript[2..],
+        adaptive_wrap_lines(
+            input.lines(),
+            RtOptions::new(/*width*/ 40)
+                .initial_indent(Line::from("  └ ".dim()))
+                .subsequent_indent(Line::from("    ".dim())),
+        ),
+    );
+}
+
+#[test]
+fn unified_exec_input_preview_preserves_fitting_lines() {
+    for input in [
+        "line\n".repeat(/*n*/ 20),
+        format!(
+            "prefixprefixprefix https://example.test/a-b\n{}",
+            "line\n".repeat(/*n*/ 20)
+        ),
+    ] {
+        let cell = new_unified_exec_interaction(/*command_display*/ None, input);
+        let mut expected = cell.transcript_lines(/*width*/ 40);
+        expected.truncate(/*len*/ 13);
+        expected.push(
+            "  … Input preview limited (ctrl + t to view transcript)."
+                .dim()
+                .into(),
+        );
+        assert_eq!(cell.display_lines(/*width*/ 40), expected);
+    }
+}
+
+#[test]
+fn unified_exec_input_preview_respects_viewport_rows() {
+    for width in [1, 2, 4, 5, 8, 40, 80] {
+        for input in [
+            "a".repeat(/*n*/ 4_000),
+            format!("https://example.com/{}", "a".repeat(/*n*/ 4_000)),
+            "界👩‍💻e\u{301}\t ".repeat(/*n*/ 1_000),
+            "\x1b[A".repeat(/*n*/ 1_000),
+        ] {
+            let cell = new_unified_exec_interaction(/*command_display*/ None, input);
+            let preview = cell.display_lines(width);
+            let header =
+                new_unified_exec_interaction(/*command_display*/ None, "x".to_string())
+                    .display_lines(width);
+            let content = &preview[header.len() - 1..preview.len() - 1];
+            assert!(
+                Paragraph::new(content.to_vec())
+                    .wrap(Wrap { trim: false })
+                    .line_count(width)
+                    <= INPUT_PREVIEW_ROWS,
+                "input preview exceeds row budget at width {width}",
+            );
+        }
+    }
+}
+
+#[test]
+fn unified_exec_input_preview_bounds_zero_width_payload() {
+    let input = "\u{301}".repeat(/*n*/ 100_000);
+    let cell = new_unified_exec_interaction(/*command_display*/ None, input.clone());
+    let preview = cell.display_lines(/*width*/ 80);
+    assert!(
+        preview
+            .last()
+            .unwrap()
+            .to_string()
+            .contains("Input preview limited")
+    );
+    assert!(
+        preview
+            .iter()
+            .map(|line| line.to_string().len())
+            .sum::<usize>()
+            < 66_000
+    );
+    assert_eq!(
+        cell.raw_lines(),
+        vec![
+            Line::from("Interacted with background terminal"),
+            Line::from(input)
+        ],
+    );
+}
+
+#[test]
+fn unified_exec_input_preview_keeps_short_and_exact_budget_input() {
+    for input in [
+        "".to_string(),
+        "ls\npwd".to_string(),
+        "x\n".repeat(/*n*/ 12),
+    ] {
+        let cell = new_unified_exec_interaction(Some("cat".to_string()), input);
+        assert_eq!(
+            cell.display_lines(/*width*/ 80),
+            cell.transcript_lines(/*width*/ 80)
+        );
+        assert_eq!(cell.display_lines(/*width*/ 0), Vec::<Line<'static>>::new());
+    }
+}