Enhanced paith input with cursor navigation and tab completion in settings import/export

docs/plans/2026-02-27-enhanced-setting-path-input.md

@@ -0,0 +1,150 @@
+# Plan: Enhanced Path Input with Cursor Navigation and Tab Completion
+
+## Context
+
+Settings page path fields (code download dir, passage download dir, export path, import path) currently only support appending characters and backspace — no cursor movement, no arrow keys, no tab completion. Users can't easily correct a typo in the middle of a path or navigate to an existing file for import.
+
+## Approach: Custom `LineInput` struct + filesystem tab completion
+
+Neither `tui-input` nor `tui-textarea` provide tab/path completion, and both have crossterm version mismatches with our deps (ratatui 0.30 + crossterm 0.28). A custom struct avoids dependency churn and gives us exactly the features we need.
+
+## New file: `src/ui/line_input.rs`
+
+### Struct
+
+```rust
+/// Which settings path field is being edited.
+pub enum PathField {
+    CodeDownloadDir,
+    PassageDownloadDir,
+    ExportPath,
+    ImportPath,
+}
+
+pub enum InputResult {
+    Continue,
+    Submit,
+    Cancel,
+}
+
+pub struct LineInput {
+    text: String,
+    cursor: usize,                // char index (NOT byte offset)
+    completions: Vec<String>,
+    completion_index: Option<usize>,
+    completion_seed: String,      // text snapshot when Tab first pressed
+    completion_error: bool,       // true if last read_dir failed
+}
+```
+
+Cursor is stored as a **char index** (0 = before first char, `text.chars().count()` = after last char). Conversion to byte offset happens only at mutation boundaries via `text.char_indices()`.
+
+### Keyboard handling
+
+| Key | Action | Resets completion? |
+|-----|--------|--------------------|
+| Left | Move cursor one char left | Yes |
+| Right | Move cursor one char right | Yes |
+| Home / Ctrl+A | Move cursor to start | Yes |
+| End / Ctrl+E | Move cursor to end | Yes |
+| Backspace | Delete char before cursor | Yes |
+| Delete | Delete char at cursor | Yes |
+| Ctrl+U | Clear entire line | Yes |
+| Ctrl+W | Delete word before cursor (see semantics below) | Yes |
+| Tab | Cycle completions forward (end-of-line only) | No |
+| BackTab | Cycle completions backward | No |
+| Printable char | Insert at cursor | Yes |
+| Esc | Return `InputResult::Cancel` | — |
+| Enter | Return `InputResult::Submit` | — |
+
+**Only Tab/BackTab preserve** the completion session. All other keys reset it.
+
+**Ctrl+W semantics**: From cursor position, first skip any consecutive whitespace to the left, then delete the contiguous non-whitespace run. This matches standard readline/bash `unix-word-rubout` behavior. Example: `"foo bar  |"` → Ctrl+W → `"foo |"`.
+
+### Tab completion
+
+Tab completion **only activates when cursor is at end-of-line**. If cursor is in the middle, Tab is a no-op.
+
+1. **First Tab** (`completion_index` is `None`): Snapshot `text` as `completion_seed`. Split into (directory, partial_filename) using the last path separator. Expand leading `~` to `dirs::home_dir()` for the `read_dir` call only — preserve `~` in output text. Call `std::fs::read_dir` with a **scan budget of 1000 entries** (iterate at most 1000 `DirEntry` results). From the scanned entries, filter those whose name starts with `partial_filename` (always case-sensitive — this is an intentional simplification; case-insensitive matching on macOS HFS+/Windows NTFS is not in scope). Hidden files (names starting with `.`) only included when `partial_filename` starts with `.`. Sort matching candidates: **directories first, then files, alphabetical within each group**. Cap the final candidate list at 100. On any `read_dir` or entry I/O error, produce zero completions and set `completion_error = true` (renders `"(cannot read directory)"` in footer).
+2. **Cycling**: Increment/decrement `completion_index`, wrapping. Replace `text` with selected completion. Directories get a trailing `std::path::MAIN_SEPARATOR`. Cursor moves to end.
+3. **Reset**: Any non-Tab/BackTab key clears completion state **and** clears `completion_error`. This means the error hint disappears on the next keystroke (text mutation, cursor move, submit, or cancel).
+4. **Mixed paths** like `~/../tmp` are not normalized — they're passed through as-is.
+5. **Hidden-file filtering** (`.-prefix only` rule) applies identically on all platforms.
+
+### Rendering
+
+```rust
+impl LineInput {
+    /// Returns (before_cursor, cursor_char, after_cursor) for styled rendering.
+    pub fn render_parts(&self) -> (&str, Option<char>, &str);
+    pub fn value(&self) -> &str;
+}
+```
+
+When cursor is at end of text, `cursor_char` is `None` and a **space with inverted background** is rendered as the cursor (avoids font/glyph compatibility issues with block characters across terminals). When cursor is in the middle, the character at cursor position is rendered with inverted colors (swapped fg/bg).
+
+## Changes to existing files
+
+### `src/ui/mod.rs`
+- Add `pub mod line_input;`
+
+### `src/app.rs`
+- Replace three booleans (`settings_editing_download_dir`, `settings_editing_export_path`, `settings_editing_import_path`) with:
+  ```rust
+  pub settings_editing_path: Option<(PathField, LineInput)>,
+  ```
+- `settings_export_path` and `settings_import_path` remain as `String`. On editing start, `LineInput` is initialized from current value. On `Submit`, value is written back to the field identified by `PathField`.
+- `clear_settings_modals()` sets `settings_editing_path` to `None`.
+- Add `is_editing_path(&self) -> bool` and `is_editing_field(&self, index: usize) -> bool` helpers.
+
+**Migration checklist** — all sites referencing the old booleans must be updated. Verify by grepping for the removed field names (`settings_editing_download_dir`, `settings_editing_export_path`, `settings_editing_import_path`) — zero hits after migration:
+- `src/main.rs` handle_settings_key priority 4 block (~line 550)
+- `src/main.rs` Enter handler for fields 5, 9, 12, 14 (~line 605)
+- `src/main.rs` render_settings `is_editing_this_path` check (~line 2693)
+- `src/main.rs` `any_path_editing` footer check (~line 2724)
+- `src/app.rs` field declarations (~line 218)
+- `src/app.rs` `clear_settings_modals` (~line 462)
+- `src/app.rs` `Default` / `new` initialization
+
+### `src/main.rs` — `handle_settings_key()`
+- **Priority 4 block**: Replace with `if let Some((field, ref mut input)) = app.settings_editing_path`. Call `input.handle(key)` and match on result. `Submit` writes value back via `field`, `Cancel` discards.
+- **Enter on path fields**: Construct `LineInput::new(current_value)` paired with appropriate `PathField` variant.
+
+### `src/main.rs` — `render_settings()`
+- When editing, render via `input.render_parts()` with cursor char in inverted style.
+- Footer hints in editing state: `"[←→] Move  [Tab] Complete (at end)  [Enter] Confirm  [Esc] Cancel"`
+- If `input.completion_error` is true, append `"(cannot read directory)"` to footer. Clears on next keystroke.
+
+## Key files
+
+- `src/ui/line_input.rs` — new
+- `src/ui/mod.rs` — add module
+- `src/app.rs` — state fields, `clear_settings_modals()`, helper methods
+- `src/main.rs` — key handling, rendering, footer
+
+## Verification
+
+1. `cargo build` — no warnings
+2. `cargo test` — all existing + new unit tests pass
+3. **Unit tests for `LineInput`** (in `line_input.rs`):
+   - Insert char at start, middle, end
+   - Delete/backspace at boundaries (start of line, end, empty string)
+   - Ctrl+W: `"foo bar  "` → `"foo "`, `"  foo"` → `"  "`, `""` → `""`
+   - Cursor: left at 0 stays 0, right at end stays at end
+   - Home/End position correctly
+   - Ctrl+U clears text and cursor to 0
+   - Tab at end-of-line with no match → no completions, no panic
+   - Tab at mid-line → no-op
+   - Tab cycling wraps around; BackTab cycles reverse
+   - Non-Tab key resets completion state
+   - `render_parts()` returns correct slices at start, middle, end positions
+4. **Grep verification**: `grep -rn 'settings_editing_download_dir\|settings_editing_export_path\|settings_editing_import_path' src/` returns zero hits
+5. Manual testing:
+   - Navigate to Export Path, press Enter → cursor appears at end
+   - Arrow left/right moves cursor, Home/End work
+   - Backspace/Delete at cursor position, Ctrl+U/Ctrl+W
+   - Type partial path, Tab → completions cycle; Shift+Tab reverses
+   - Tab on directory appends separator, allows continued completion
+   - Tab on nonexistent path → footer shows "(cannot read directory)"
+   - Enter confirms, Esc cancels (value reverts)
+   - All four path fields (code dir, passage dir, export, import) work identically

src/app.rs

@@ -45,6 +45,7 @@ use crate::store::schema::{
     DrillHistoryData, EXPORT_VERSION, ExportData, KeyStatsData, ProfileData,
 };
 use crate::ui::components::menu::Menu;
+use crate::ui::line_input::{LineInput, PathField};
 use crate::ui::theme::Theme;
 
 #[derive(Clone, Copy, Debug, PartialEq, Eq)]
@@ -216,7 +217,7 @@ pub struct App {
     pub store: Option<JsonStore>,
     pub should_quit: bool,
     pub settings_selected: usize,
-    pub settings_editing_download_dir: bool,
+    pub settings_editing_path: Option<(PathField, LineInput)>,
     pub stats_tab: usize,
     pub depressed_keys: HashSet<char>,
     pub last_key_time: Option<Instant>,
@@ -266,8 +267,6 @@ pub struct App {
     pub settings_status_message: Option<StatusMessage>,
     pub settings_export_path: String,
     pub settings_import_path: String,
-    pub settings_editing_export_path: bool,
-    pub settings_editing_import_path: bool,
     pub keyboard_explorer_selected: Option<char>,
     pub explorer_accuracy_cache_overall: Option<(char, usize, usize)>,
     pub explorer_accuracy_cache_ranked: Option<(char, usize, usize)>,
@@ -369,7 +368,7 @@ impl App {
             store,
             should_quit: false,
             settings_selected: 0,
-            settings_editing_download_dir: false,
+            settings_editing_path: None,
             stats_tab: 0,
             depressed_keys: HashSet::new(),
             last_key_time: None,
@@ -419,8 +418,6 @@ impl App {
             settings_status_message: None,
             settings_export_path: default_export_path(),
             settings_import_path: default_export_path(),
-            settings_editing_export_path: false,
-            settings_editing_import_path: false,
             keyboard_explorer_selected: None,
             explorer_accuracy_cache_overall: None,
             explorer_accuracy_cache_ranked: None,
@@ -462,9 +459,23 @@ impl App {
     pub fn clear_settings_modals(&mut self) {
         self.settings_confirm_import = false;
         self.settings_export_conflict = false;
-        self.settings_editing_export_path = false;
+        self.settings_editing_path = None;
-        self.settings_editing_import_path = false;
+    }
-        self.settings_editing_download_dir = false;
+
+    pub fn is_editing_path(&self) -> bool {
+        self.settings_editing_path.is_some()
+    }
+
+    pub fn is_editing_field(&self, index: usize) -> bool {
+        self.settings_editing_path
+            .as_ref()
+            .map(|(field, _)| match field {
+                PathField::CodeDownloadDir => index == 5,
+                PathField::PassageDownloadDir => index == 9,
+                PathField::ExportPath => index == 12,
+                PathField::ImportPath => index == 14,
+            })
+            .unwrap_or(false)
     }
 
     pub fn arm_post_drill_input_lock(&mut self) {
@@ -1575,7 +1586,7 @@ impl App {
 
     pub fn go_to_settings(&mut self) {
         self.settings_selected = 0;
-        self.settings_editing_download_dir = false;
+        self.settings_editing_path = None;
         self.screen = AppScreen::Settings;
     }
 
@@ -2199,7 +2210,7 @@ impl App {
             store: None,
             should_quit: false,
             settings_selected: 0,
-            settings_editing_download_dir: false,
+            settings_editing_path: None,
             stats_tab: 0,
             depressed_keys: HashSet::new(),
             last_key_time: None,
@@ -2249,8 +2260,6 @@ impl App {
             settings_status_message: None,
             settings_export_path: default_export_path(),
             settings_import_path: default_export_path(),
-            settings_editing_export_path: false,
-            settings_editing_import_path: false,
             keyboard_explorer_selected: None,
             explorer_accuracy_cache_overall: None,
             explorer_accuracy_cache_ranked: None,

src/main.rs

@@ -29,6 +29,7 @@ use ratatui::text::{Line, Span};
 use ratatui::widgets::{Block, Paragraph, Widget, Wrap};
 
 use app::{App, AppScreen, DrillMode, MilestoneKind, StatusKind};
+use ui::line_input::{InputResult, LineInput, PathField};
 use engine::skill_tree::{DrillScope, find_key_branch};
 use event::{AppEvent, EventHandler};
 use generator::code_syntax::{code_language_options, is_language_cached, language_by_key};
@@ -548,41 +549,22 @@ fn handle_settings_key(app: &mut App, key: KeyEvent) {
     }
 
     // Priority 4: editing a path field
-    if app.settings_editing_download_dir
+    if let Some((field, ref mut input)) = app.settings_editing_path {
-        || app.settings_editing_export_path
+        match input.handle(key) {
-        || app.settings_editing_import_path
+            InputResult::Submit => {
-    {
+                let value = input.value().to_string();
-        match key.code {
+                match field {
-            KeyCode::Esc => {
+                    PathField::CodeDownloadDir => app.config.code_download_dir = value,
-                app.clear_settings_modals();
+                    PathField::PassageDownloadDir => app.config.passage_download_dir = value,
-            }
+                    PathField::ExportPath => app.settings_export_path = value,
-            KeyCode::Backspace => {
+                    PathField::ImportPath => app.settings_import_path = value,
-                if app.settings_editing_download_dir {
-                    if app.settings_selected == 5 {
-                        app.config.code_download_dir.pop();
-                    } else if app.settings_selected == 9 {
-                        app.config.passage_download_dir.pop();
-                    }
-                } else if app.settings_editing_export_path {
-                    app.settings_export_path.pop();
-                } else if app.settings_editing_import_path {
-                    app.settings_import_path.pop();
                 }
+                app.settings_editing_path = None;
             }
-            KeyCode::Char(ch) if !key.modifiers.contains(KeyModifiers::CONTROL) => {
+            InputResult::Cancel => {
-                if app.settings_editing_download_dir {
+                app.settings_editing_path = None;
-                    if app.settings_selected == 5 {
-                        app.config.code_download_dir.push(ch);
-                    } else if app.settings_selected == 9 {
-                        app.config.passage_download_dir.push(ch);
-                    }
-                } else if app.settings_editing_export_path {
-                    app.settings_export_path.push(ch);
-                } else if app.settings_editing_import_path {
-                    app.settings_import_path.push(ch);
-                }
             }
-            _ => {}
+            InputResult::Continue => {}
         }
         return;
     }
@@ -603,20 +585,36 @@ fn handle_settings_key(app: &mut App, key: KeyEvent) {
             }
         }
         KeyCode::Enter => match app.settings_selected {
-            5 | 9 => {
+            5 => {
                 app.clear_settings_modals();
-                app.settings_editing_download_dir = true;
+                app.settings_editing_path = Some((
+                    PathField::CodeDownloadDir,
+                    LineInput::new(&app.config.code_download_dir),
+                ));
+            }
+            9 => {
+                app.clear_settings_modals();
+                app.settings_editing_path = Some((
+                    PathField::PassageDownloadDir,
+                    LineInput::new(&app.config.passage_download_dir),
+                ));
             }
             7 => app.start_code_downloads_from_settings(),
             11 => app.start_passage_downloads_from_settings(),
             12 => {
                 app.clear_settings_modals();
-                app.settings_editing_export_path = true;
+                app.settings_editing_path = Some((
+                    PathField::ExportPath,
+                    LineInput::new(&app.settings_export_path),
+                ));
             }
             13 => app.export_data(),
             14 => {
                 app.clear_settings_modals();
-                app.settings_editing_import_path = true;
+                app.settings_editing_path = Some((
+                    PathField::ImportPath,
+                    LineInput::new(&app.settings_import_path),
+                ));
             }
             15 => {
                 app.clear_settings_modals();
@@ -1788,16 +1786,17 @@ mod review_tests {
 
     /// Helper: count how many settings modal/edit flags are active
     fn modal_edit_count(app: &App) -> usize {
-        [
+        let mut count = 0;
-            app.settings_confirm_import,
+        if app.settings_confirm_import {
-            app.settings_export_conflict,
+            count += 1;
-            app.settings_editing_export_path,
+        }
-            app.settings_editing_import_path,
+        if app.settings_export_conflict {
-            app.settings_editing_download_dir,
+            count += 1;
-        ]
+        }
-        .iter()
+        if app.is_editing_path() {
-        .filter(|&&f| f)
+            count += 1;
-        .count()
+        }
+        count
     }
 
     #[test]
@@ -1818,12 +1817,12 @@ mod review_tests {
         // Enter export path editing
         app.settings_selected = 12; // Export Path
         handle_settings_key(&mut app, KeyEvent::new(KeyCode::Enter, KeyModifiers::NONE));
-        assert!(app.settings_editing_export_path);
+        assert!(app.is_editing_field(12));
         assert!(modal_edit_count(&app) <= 1);
 
         // Esc out
         handle_settings_key(&mut app, KeyEvent::new(KeyCode::Esc, KeyModifiers::NONE));
-        assert!(!app.settings_editing_export_path);
+        assert!(!app.is_editing_path());
     }
 
     #[test]
@@ -1834,14 +1833,14 @@ mod review_tests {
         // Activate export path editing first
         app.settings_selected = 12;
         handle_settings_key(&mut app, KeyEvent::new(KeyCode::Enter, KeyModifiers::NONE));
-        assert!(app.settings_editing_export_path);
+        assert!(app.is_editing_field(12));
 
         // Esc out, then enter import path editing
         handle_settings_key(&mut app, KeyEvent::new(KeyCode::Esc, KeyModifiers::NONE));
         app.settings_selected = 14; // Import Path
         handle_settings_key(&mut app, KeyEvent::new(KeyCode::Enter, KeyModifiers::NONE));
-        assert!(app.settings_editing_import_path);
+        assert!(app.is_editing_field(14));
-        assert!(!app.settings_editing_export_path);
+        assert!(!app.is_editing_field(12));
         assert!(modal_edit_count(&app) <= 1);
     }
 
@@ -2387,6 +2386,85 @@ mod review_tests {
 
         assert!(app.should_quit, "Ctrl+C should set should_quit even during input lock");
     }
+
+    /// Helper: render settings to a test buffer and return its text content.
+    fn render_settings_to_string(app: &App) -> String {
+        let backend = ratatui::backend::TestBackend::new(80, 40);
+        let mut terminal = Terminal::new(backend).unwrap();
+        terminal
+            .draw(|frame| render_settings(frame, app))
+            .unwrap();
+        let buf = terminal.backend().buffer().clone();
+        let mut text = String::new();
+        for y in 0..buf.area.height {
+            for x in 0..buf.area.width {
+                text.push(buf[(x, y)].symbol().chars().next().unwrap_or(' '));
+            }
+            text.push('\n');
+        }
+        text
+    }
+
+    #[test]
+    fn footer_shows_completion_error_and_clears_on_keystroke() {
+        let mut app = test_app();
+        app.screen = AppScreen::Settings;
+        app.settings_selected = 12; // Export Path
+
+        // Enter editing mode
+        handle_settings_key(&mut app, KeyEvent::new(KeyCode::Enter, KeyModifiers::NONE));
+        assert!(app.is_editing_field(12));
+
+        // Set path to nonexistent dir and trigger tab completion error
+        if let Some((_, ref mut input)) = app.settings_editing_path {
+            input.handle(KeyEvent::new(KeyCode::Char('u'), KeyModifiers::CONTROL)); // clear
+            for ch in "/nonexistent_zzz_dir/".chars() {
+                input.handle(KeyEvent::new(KeyCode::Char(ch), KeyModifiers::NONE));
+            }
+            input.handle(KeyEvent::new(KeyCode::Tab, KeyModifiers::NONE));
+            assert!(input.completion_error);
+        }
+
+        // Render and check footer contains the error hint
+        let output = render_settings_to_string(&app);
+        assert!(
+            output.contains("(cannot read directory)"),
+            "Footer should show completion error hint"
+        );
+
+        // Press a non-tab key to clear the error
+        handle_settings_key(
+            &mut app,
+            KeyEvent::new(KeyCode::Left, KeyModifiers::NONE),
+        );
+
+        // Render again — error hint should be gone
+        let output_after = render_settings_to_string(&app);
+        assert!(
+            !output_after.contains("(cannot read directory)"),
+            "Footer error hint should clear after non-Tab keystroke"
+        );
+    }
+
+    #[test]
+    fn footer_shows_editing_hints_when_path_editing() {
+        let mut app = test_app();
+        app.screen = AppScreen::Settings;
+        app.settings_selected = 12;
+
+        // Before editing: shows default hints
+        let output_before = render_settings_to_string(&app);
+        assert!(output_before.contains("[ESC] Save & back"));
+
+        // Enter editing mode
+        handle_settings_key(&mut app, KeyEvent::new(KeyCode::Enter, KeyModifiers::NONE));
+
+        // After editing: shows editing hints
+        let output_during = render_settings_to_string(&app);
+        assert!(output_during.contains("[Enter] Confirm"));
+        assert!(output_during.contains("[Esc] Cancel"));
+        assert!(output_during.contains("[Tab] Complete"));
+    }
 }
 
 fn render_result(frame: &mut ratatui::Frame, app: &App) {
@@ -2621,7 +2699,38 @@ fn render_settings(frame: &mut ratatui::Frame, app: &App) {
     ];
 
     let header_height = if inner.height > 0 { 1 } else { 0 };
-    let footer_height = if inner.height > header_height { 1 } else { 0 };
+
+    // Compute footer hints early so we know how many lines they need.
+    let completion_error = app
+        .settings_editing_path
+        .as_ref()
+        .map(|(_, input)| input.completion_error)
+        .unwrap_or(false);
+    let footer_hints: Vec<&str> = if app.is_editing_path() {
+        let mut hints = vec![
+            "[←→] Move",
+            "[Tab] Complete (at end)",
+            "[Enter] Confirm",
+            "[Esc] Cancel",
+        ];
+        if completion_error {
+            hints.push("(cannot read directory)");
+        }
+        hints
+    } else {
+        vec![
+            "[ESC] Save & back",
+            "[Enter/arrows] Change value",
+            "[Enter on path] Edit",
+        ]
+    };
+    let footer_packed = pack_hint_lines(&footer_hints, inner.width as usize);
+    let footer_height = if inner.height > header_height {
+        (footer_packed.len() as u16).max(1)
+    } else {
+        0
+    };
+
     let field_height = inner.height.saturating_sub(header_height + footer_height);
 
     let layout = Layout::default()
@@ -2690,28 +2799,44 @@ fn render_settings(frame: &mut ratatui::Frame, app: &App) {
             colors.text_pending()
         });
 
-        let is_editing_this_path = is_selected
+        let is_editing_this_path = is_selected && *is_path && app.is_editing_field(i);
-            && *is_path
-            && (app.settings_editing_download_dir
-                || app.settings_editing_export_path
-                || app.settings_editing_import_path);
         let lines = if *is_path {
-            let path_line = if is_editing_this_path {
+            if is_editing_this_path {
-                format!("  {value}_")
+                if let Some((_, ref input)) = app.settings_editing_path {
+                    let (before, cursor_ch, after) = input.render_parts();
+                    let cursor_style = Style::default()
+                        .fg(colors.bg())
+                        .bg(colors.focused_key());
+                    let path_spans = match cursor_ch {
+                        Some(ch) => vec![
+                            Span::styled(format!("  {before}"), value_style),
+                            Span::styled(ch.to_string(), cursor_style),
+                            Span::styled(after.to_string(), value_style),
+                        ],
+                        None => vec![
+                            Span::styled(format!("  {before}"), value_style),
+                            Span::styled(" ", cursor_style),
+                        ],
+                    };
+                    vec![
+                        Line::from(Span::styled(
+                            format!("{indicator}{label}: (editing)"),
+                            label_style,
+                        )),
+                        Line::from(path_spans),
+                    ]
+                } else {
+                    vec![
+                        Line::from(Span::styled(label_text, label_style)),
+                        Line::from(Span::styled(format!("  {value}"), value_style)),
+                    ]
+                }
             } else {
-                format!("  {value}")
+                vec![
-            };
+                    Line::from(Span::styled(label_text, label_style)),
-            vec![
+                    Line::from(Span::styled(format!("  {value}"), value_style)),
-                Line::from(Span::styled(
+                ]
-                    if is_editing_this_path {
+            }
-                        format!("{indicator}{label}: (editing)")
-                    } else {
-                        label_text
-                    },
-                    label_style,
-                )),
-                Line::from(Span::styled(path_line, value_style)),
-            ]
         } else {
             vec![
                 Line::from(Span::styled(label_text, label_style)),
@@ -2721,23 +2846,7 @@ fn render_settings(frame: &mut ratatui::Frame, app: &App) {
         Paragraph::new(lines).render(field_layout[row], frame.buffer_mut());
     }
 
-    let any_path_editing = app.settings_editing_download_dir
+    let footer_lines: Vec<Line> = footer_packed
-        || app.settings_editing_export_path
-        || app.settings_editing_import_path;
-    let footer_hints: Vec<&str> = if any_path_editing {
-        vec![
-            "Editing path:",
-            "[Type/Backspace] Modify",
-            "[ESC] Done editing",
-        ]
-    } else {
-        vec![
-            "[ESC] Save & back",
-            "[Enter/arrows] Change value",
-            "[Enter on path] Edit",
-        ]
-    };
-    let footer_lines: Vec<Line> = pack_hint_lines(&footer_hints, layout[2].width as usize)
         .into_iter()
         .map(|line| Line::from(Span::styled(line, Style::default().fg(colors.accent()))))
         .collect();

src/ui/line_input.rs

@@ -0,0 +1,705 @@
+use crossterm::event::{KeyCode, KeyEvent, KeyModifiers};
+
+/// Which settings path field is being edited.
+#[derive(Clone, Copy, Debug, PartialEq, Eq)]
+pub enum PathField {
+    CodeDownloadDir,
+    PassageDownloadDir,
+    ExportPath,
+    ImportPath,
+}
+
+#[derive(Clone, Copy, Debug, PartialEq, Eq)]
+pub enum InputResult {
+    Continue,
+    Submit,
+    Cancel,
+}
+
+pub struct LineInput {
+    text: String,
+    /// Cursor position as a char index (0 = before first char).
+    cursor: usize,
+    completions: Vec<String>,
+    completion_index: Option<usize>,
+    /// Text snapshot when Tab was first pressed.
+    completion_seed: String,
+    /// True if last read_dir call failed.
+    pub completion_error: bool,
+}
+
+impl LineInput {
+    pub fn new(text: &str) -> Self {
+        let cursor = text.chars().count();
+        Self {
+            text: text.to_string(),
+            cursor,
+            completions: Vec::new(),
+            completion_index: None,
+            completion_seed: String::new(),
+            completion_error: false,
+        }
+    }
+
+    pub fn value(&self) -> &str {
+        &self.text
+    }
+
+    /// Returns (before_cursor, cursor_char, after_cursor) for styled rendering.
+    /// When cursor is at end of text, cursor_char is None.
+    pub fn render_parts(&self) -> (&str, Option<char>, &str) {
+        let byte_offset = self.char_to_byte(self.cursor);
+        if self.cursor >= self.text.chars().count() {
+            (&self.text, None, "")
+        } else {
+            let ch = self.text[byte_offset..].chars().next().unwrap();
+            let next_byte = byte_offset + ch.len_utf8();
+            (&self.text[..byte_offset], Some(ch), &self.text[next_byte..])
+        }
+    }
+
+    pub fn handle(&mut self, key: KeyEvent) -> InputResult {
+        match key.code {
+            KeyCode::Esc => return InputResult::Cancel,
+            KeyCode::Enter => return InputResult::Submit,
+
+            KeyCode::Left => {
+                self.reset_completion();
+                if self.cursor > 0 {
+                    self.cursor -= 1;
+                }
+            }
+            KeyCode::Right => {
+                self.reset_completion();
+                let len = self.text.chars().count();
+                if self.cursor < len {
+                    self.cursor += 1;
+                }
+            }
+            KeyCode::Home => {
+                self.reset_completion();
+                self.cursor = 0;
+            }
+            KeyCode::End => {
+                self.reset_completion();
+                self.cursor = self.text.chars().count();
+            }
+            KeyCode::Backspace => {
+                self.reset_completion();
+                if self.cursor > 0 {
+                    let byte_offset = self.char_to_byte(self.cursor - 1);
+                    let ch = self.text[byte_offset..].chars().next().unwrap();
+                    self.text.replace_range(byte_offset..byte_offset + ch.len_utf8(), "");
+                    self.cursor -= 1;
+                }
+            }
+            KeyCode::Delete => {
+                self.reset_completion();
+                let len = self.text.chars().count();
+                if self.cursor < len {
+                    let byte_offset = self.char_to_byte(self.cursor);
+                    let ch = self.text[byte_offset..].chars().next().unwrap();
+                    self.text.replace_range(byte_offset..byte_offset + ch.len_utf8(), "");
+                }
+            }
+            KeyCode::Tab => {
+                self.tab_complete(true);
+            }
+            KeyCode::BackTab => {
+                self.tab_complete(false);
+            }
+            KeyCode::Char('a') if key.modifiers.contains(KeyModifiers::CONTROL) => {
+                self.reset_completion();
+                self.cursor = 0;
+            }
+            KeyCode::Char('e') if key.modifiers.contains(KeyModifiers::CONTROL) => {
+                self.reset_completion();
+                self.cursor = self.text.chars().count();
+            }
+            KeyCode::Char('u') if key.modifiers.contains(KeyModifiers::CONTROL) => {
+                self.reset_completion();
+                self.text.clear();
+                self.cursor = 0;
+            }
+            KeyCode::Char('w') if key.modifiers.contains(KeyModifiers::CONTROL) => {
+                self.reset_completion();
+                self.delete_word_back();
+            }
+            KeyCode::Char(ch) if !key.modifiers.contains(KeyModifiers::CONTROL) => {
+                self.reset_completion();
+                let byte_offset = self.char_to_byte(self.cursor);
+                self.text.insert(byte_offset, ch);
+                self.cursor += 1;
+            }
+            _ => {}
+        }
+        InputResult::Continue
+    }
+
+    /// Convert char index to byte offset.
+    fn char_to_byte(&self, char_idx: usize) -> usize {
+        self.text
+            .char_indices()
+            .nth(char_idx)
+            .map(|(b, _)| b)
+            .unwrap_or(self.text.len())
+    }
+
+    /// Delete word before cursor (unix-word-rubout: skip whitespace, then non-whitespace).
+    fn delete_word_back(&mut self) {
+        if self.cursor == 0 {
+            return;
+        }
+        let chars: Vec<char> = self.text.chars().collect();
+        let mut pos = self.cursor;
+
+        // Skip trailing whitespace
+        while pos > 0 && chars[pos - 1].is_whitespace() {
+            pos -= 1;
+        }
+        // Skip non-whitespace
+        while pos > 0 && !chars[pos - 1].is_whitespace() {
+            pos -= 1;
+        }
+
+        let start_byte = self.char_to_byte(pos);
+        let end_byte = self.char_to_byte(self.cursor);
+        self.text.replace_range(start_byte..end_byte, "");
+        self.cursor = pos;
+    }
+
+    fn reset_completion(&mut self) {
+        self.completions.clear();
+        self.completion_index = None;
+        self.completion_seed.clear();
+        self.completion_error = false;
+    }
+
+    fn tab_complete(&mut self, forward: bool) {
+        // Only activate when cursor is at end of line
+        let len = self.text.chars().count();
+        if self.cursor < len {
+            return;
+        }
+
+        if self.completion_index.is_none() {
+            // First tab press: build completions
+            self.completion_seed = self.text.clone();
+            self.completion_error = false;
+            self.completions = self.build_completions();
+            if self.completions.is_empty() {
+                return;
+            }
+            self.completion_index = Some(0);
+            self.apply_completion(0);
+        } else if !self.completions.is_empty() {
+            // Cycle
+            let idx = self.completion_index.unwrap();
+            let count = self.completions.len();
+            let next = if forward {
+                (idx + 1) % count
+            } else {
+                (idx + count - 1) % count
+            };
+            self.completion_index = Some(next);
+            self.apply_completion(next);
+        }
+    }
+
+    fn apply_completion(&mut self, idx: usize) {
+        self.text = self.completions[idx].clone();
+        self.cursor = self.text.chars().count();
+    }
+
+    fn build_completions(&mut self) -> Vec<String> {
+        let seed = self.completion_seed.clone();
+
+        // Split seed into (dir_part, partial_filename) by last path separator.
+        // Accept both '/' and '\\' so user-typed alternate separators work on any platform.
+        let last_sep_pos = seed
+            .rfind('/')
+            .into_iter()
+            .chain(seed.rfind('\\'))
+            .max();
+        let (dir_str, partial) = if let Some(pos) = last_sep_pos {
+            (&seed[..=pos], &seed[pos + 1..])
+        } else {
+            ("", seed.as_str())
+        };
+
+        // Expand ~ for read_dir, but keep ~ in output
+        let expanded_dir = if dir_str.starts_with('~') {
+            if let Some(home) = dirs::home_dir() {
+                let home_str = home.to_string_lossy().to_string();
+                format!("{}{}", home_str, &dir_str[1..])
+            } else {
+                dir_str.to_string()
+            }
+        } else if dir_str.is_empty() {
+            ".".to_string()
+        } else {
+            dir_str.to_string()
+        };
+
+        let read_result = std::fs::read_dir(&expanded_dir);
+        let entries = match read_result {
+            Ok(rd) => rd,
+            Err(_) => {
+                self.completion_error = true;
+                return Vec::new();
+            }
+        };
+
+        let entry_iter = entries.map(|result| {
+            result.map(|entry| {
+                let name = entry.file_name().to_string_lossy().to_string();
+                let is_dir = entry.file_type().map(|ft| ft.is_dir()).unwrap_or(false);
+                (name, is_dir)
+            })
+        });
+
+        self.collect_completions(entry_iter, dir_str, partial)
+    }
+
+    /// Scan an iterator of (name, is_dir) results, filter/sort, and return completions.
+    /// Extracted so tests can inject synthetic iterators with errors.
+    fn collect_completions(
+        &mut self,
+        entries: impl Iterator<Item = std::io::Result<(String, bool)>>,
+        dir_str: &str,
+        partial: &str,
+    ) -> Vec<String> {
+        let sep = std::path::MAIN_SEPARATOR;
+        let include_hidden = partial.starts_with('.');
+
+        let mut candidates: Vec<(bool, String)> = Vec::new(); // (is_dir, full_text)
+        let mut scanned = 0usize;
+        for entry_result in entries {
+            if scanned >= 1000 {
+                break;
+            }
+            scanned += 1;
+
+            let (name_str, is_dir) = match entry_result {
+                Ok(pair) => pair,
+                Err(_) => {
+                    self.completion_error = true;
+                    return Vec::new();
+                }
+            };
+
+            // Skip hidden files unless partial starts with '.'
+            if !include_hidden && name_str.starts_with('.') {
+                continue;
+            }
+
+            // Filter by prefix
+            if !name_str.starts_with(partial) {
+                continue;
+            }
+
+            let full = if is_dir {
+                format!("{}{}{}", dir_str, name_str, sep)
+            } else {
+                format!("{}{}", dir_str, name_str)
+            };
+
+            candidates.push((is_dir, full));
+        }
+
+        // Sort: directories first, then files, alphabetical within each group
+        candidates.sort_by(|a, b| {
+            b.0.cmp(&a.0) // true (dir) before false (file)
+                .then_with(|| a.1.cmp(&b.1))
+        });
+
+        // Cap at 100
+        candidates.truncate(100);
+
+        candidates.into_iter().map(|(_, path)| path).collect()
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    fn key(code: KeyCode) -> KeyEvent {
+        KeyEvent::new(code, KeyModifiers::NONE)
+    }
+
+    fn ctrl(ch: char) -> KeyEvent {
+        KeyEvent::new(KeyCode::Char(ch), KeyModifiers::CONTROL)
+    }
+
+    #[test]
+    fn insert_at_start_middle_end() {
+        let mut input = LineInput::new("ac");
+        // Cursor at end (2), insert 'd' -> "acd"
+        input.handle(key(KeyCode::Char('d')));
+        assert_eq!(input.value(), "acd");
+
+        // Move to start, insert 'z' -> "zacd"
+        input.handle(key(KeyCode::Home));
+        input.handle(key(KeyCode::Char('z')));
+        assert_eq!(input.value(), "zacd");
+        assert_eq!(input.cursor, 1);
+
+        // Move right once (past 'a'), insert 'b' -> "zabcd"
+        input.handle(key(KeyCode::Right));
+        input.handle(key(KeyCode::Char('b')));
+        assert_eq!(input.value(), "zabcd");
+        assert_eq!(input.cursor, 3);
+    }
+
+    #[test]
+    fn backspace_at_boundaries() {
+        let mut input = LineInput::new("ab");
+        // Backspace at end -> "a"
+        input.handle(key(KeyCode::Backspace));
+        assert_eq!(input.value(), "a");
+
+        // Backspace again -> ""
+        input.handle(key(KeyCode::Backspace));
+        assert_eq!(input.value(), "");
+
+        // Backspace on empty -> no panic
+        input.handle(key(KeyCode::Backspace));
+        assert_eq!(input.value(), "");
+        assert_eq!(input.cursor, 0);
+    }
+
+    #[test]
+    fn delete_at_boundaries() {
+        let mut input = LineInput::new("ab");
+        // Move to start, delete -> "b"
+        input.handle(key(KeyCode::Home));
+        input.handle(key(KeyCode::Delete));
+        assert_eq!(input.value(), "b");
+        assert_eq!(input.cursor, 0);
+
+        // Delete at end -> no change
+        input.handle(key(KeyCode::End));
+        input.handle(key(KeyCode::Delete));
+        assert_eq!(input.value(), "b");
+
+        // Empty string delete -> no panic
+        let mut empty = LineInput::new("");
+        empty.handle(key(KeyCode::Delete));
+        assert_eq!(empty.value(), "");
+    }
+
+    #[test]
+    fn ctrl_w_word_delete() {
+        // "foo bar  " -> "foo "
+        let mut input = LineInput::new("foo bar  ");
+        input.handle(ctrl('w'));
+        assert_eq!(input.value(), "foo ");
+
+        // "  foo" cursor at end -> "  "
+        let mut input2 = LineInput::new("  foo");
+        input2.handle(ctrl('w'));
+        assert_eq!(input2.value(), "  ");
+
+        // empty -> empty
+        let mut input3 = LineInput::new("");
+        input3.handle(ctrl('w'));
+        assert_eq!(input3.value(), "");
+    }
+
+    #[test]
+    fn cursor_left_at_zero_stays() {
+        let mut input = LineInput::new("a");
+        input.handle(key(KeyCode::Home));
+        assert_eq!(input.cursor, 0);
+        input.handle(key(KeyCode::Left));
+        assert_eq!(input.cursor, 0);
+    }
+
+    #[test]
+    fn cursor_right_at_end_stays() {
+        let mut input = LineInput::new("a");
+        assert_eq!(input.cursor, 1);
+        input.handle(key(KeyCode::Right));
+        assert_eq!(input.cursor, 1);
+    }
+
+    #[test]
+    fn home_end_position() {
+        let mut input = LineInput::new("hello");
+        input.handle(key(KeyCode::Home));
+        assert_eq!(input.cursor, 0);
+        input.handle(key(KeyCode::End));
+        assert_eq!(input.cursor, 5);
+    }
+
+    #[test]
+    fn ctrl_a_and_ctrl_e() {
+        let mut input = LineInput::new("test");
+        input.handle(ctrl('a'));
+        assert_eq!(input.cursor, 0);
+        input.handle(ctrl('e'));
+        assert_eq!(input.cursor, 4);
+    }
+
+    #[test]
+    fn ctrl_u_clears() {
+        let mut input = LineInput::new("hello world");
+        input.handle(ctrl('u'));
+        assert_eq!(input.value(), "");
+        assert_eq!(input.cursor, 0);
+    }
+
+    #[test]
+    fn tab_at_midline_is_noop() {
+        let mut input = LineInput::new("hello");
+        input.handle(key(KeyCode::Home));
+        input.handle(key(KeyCode::Right)); // cursor at 1
+        let result = input.handle(key(KeyCode::Tab));
+        assert_eq!(result, InputResult::Continue);
+        assert_eq!(input.value(), "hello");
+        assert_eq!(input.cursor, 1);
+    }
+
+    #[test]
+    fn tab_no_match_sets_error_state() {
+        let mut input = LineInput::new("/nonexistent_path_zzzzz/");
+        let result = input.handle(key(KeyCode::Tab));
+        assert_eq!(result, InputResult::Continue);
+        assert!(input.completions.is_empty());
+        assert!(input.completion_index.is_none());
+        assert!(input.completion_error);
+    }
+
+    #[test]
+    fn non_tab_key_resets_completion() {
+        let dir = tempfile::tempdir().unwrap();
+        std::fs::write(dir.path().join("aaa.txt"), "").unwrap();
+        let path = format!("{}/", dir.path().display());
+        let mut input = LineInput::new(&path);
+
+        // Tab to start completion
+        input.handle(key(KeyCode::Tab));
+        assert!(!input.completions.is_empty());
+        assert!(input.completion_index.is_some());
+
+        // Any non-tab key resets
+        input.handle(key(KeyCode::Char('x')));
+        assert!(input.completions.is_empty());
+        assert!(input.completion_index.is_none());
+        assert!(input.value().ends_with('x'));
+    }
+
+    #[test]
+    fn render_parts_at_start() {
+        let input = LineInput::new("abc");
+        let mut input = input;
+        input.cursor = 0;
+        let (before, ch, after) = input.render_parts();
+        assert_eq!(before, "");
+        assert_eq!(ch, Some('a'));
+        assert_eq!(after, "bc");
+    }
+
+    #[test]
+    fn render_parts_at_middle() {
+        let mut input = LineInput::new("abc");
+        input.cursor = 1;
+        let (before, ch, after) = input.render_parts();
+        assert_eq!(before, "a");
+        assert_eq!(ch, Some('b'));
+        assert_eq!(after, "c");
+    }
+
+    #[test]
+    fn render_parts_at_end() {
+        let input = LineInput::new("abc");
+        let (before, ch, after) = input.render_parts();
+        assert_eq!(before, "abc");
+        assert_eq!(ch, None);
+        assert_eq!(after, "");
+    }
+
+    #[test]
+    fn submit_and_cancel() {
+        let mut input = LineInput::new("test");
+        assert_eq!(input.handle(key(KeyCode::Enter)), InputResult::Submit);
+
+        let mut input2 = LineInput::new("test");
+        assert_eq!(input2.handle(key(KeyCode::Esc)), InputResult::Cancel);
+    }
+
+    #[test]
+    fn tab_completion_cycles_and_backtab_reverses() {
+        let dir = tempfile::tempdir().unwrap();
+        std::fs::write(dir.path().join("alpha.txt"), "").unwrap();
+        std::fs::write(dir.path().join("beta.txt"), "").unwrap();
+        std::fs::create_dir(dir.path().join("gamma_dir")).unwrap();
+        let path = format!("{}/", dir.path().display());
+
+        let mut input = LineInput::new(&path);
+        input.handle(key(KeyCode::Tab));
+
+        // Should have 3 completions: gamma_dir/ first (dirs first), then alpha.txt, beta.txt
+        assert_eq!(input.completions.len(), 3);
+        assert!(input.completions[0].ends_with("gamma_dir/"));
+        assert!(input.completions[1].ends_with("alpha.txt"));
+        assert!(input.completions[2].ends_with("beta.txt"));
+
+        // First tab selects gamma_dir/
+        assert!(input.value().ends_with("gamma_dir/"));
+
+        // Second tab cycles to alpha.txt
+        input.handle(key(KeyCode::Tab));
+        assert!(input.value().ends_with("alpha.txt"));
+
+        // Third tab cycles to beta.txt
+        input.handle(key(KeyCode::Tab));
+        assert!(input.value().ends_with("beta.txt"));
+
+        // Fourth tab wraps to gamma_dir/
+        input.handle(key(KeyCode::Tab));
+        assert!(input.value().ends_with("gamma_dir/"));
+
+        // BackTab reverses to beta.txt
+        input.handle(key(KeyCode::BackTab));
+        assert!(input.value().ends_with("beta.txt"));
+    }
+
+    #[test]
+    fn completion_error_on_bad_dir() {
+        let mut input = LineInput::new("/nonexistent_zzz_dir/");
+        input.handle(key(KeyCode::Tab));
+        assert!(input.completion_error);
+        assert!(input.completions.is_empty());
+        assert!(input.completion_index.is_none());
+
+        // Any key clears the error
+        input.handle(key(KeyCode::Char('x')));
+        assert!(!input.completion_error);
+    }
+
+    #[test]
+    fn completion_hidden_file_filtering() {
+        let dir = tempfile::tempdir().unwrap();
+        std::fs::write(dir.path().join(".hidden"), "").unwrap();
+        std::fs::write(dir.path().join("visible"), "").unwrap();
+
+        // Without dot prefix: hidden files excluded
+        let path = format!("{}/", dir.path().display());
+        let mut input = LineInput::new(&path);
+        input.handle(key(KeyCode::Tab));
+        assert_eq!(input.completions.len(), 1);
+        assert!(input.completions[0].ends_with("visible"));
+
+        // With dot prefix: hidden files included
+        let path_dot = format!("{}/.h", dir.path().display());
+        let mut input2 = LineInput::new(&path_dot);
+        input2.handle(key(KeyCode::Tab));
+        assert_eq!(input2.completions.len(), 1);
+        assert!(input2.completions[0].ends_with(".hidden"));
+    }
+
+    #[test]
+    fn completion_prefix_filtering() {
+        let dir = tempfile::tempdir().unwrap();
+        std::fs::write(dir.path().join("foo_bar"), "").unwrap();
+        std::fs::write(dir.path().join("foo_baz"), "").unwrap();
+        std::fs::write(dir.path().join("other"), "").unwrap();
+
+        let path = format!("{}/foo_", dir.path().display());
+        let mut input = LineInput::new(&path);
+        input.handle(key(KeyCode::Tab));
+        assert_eq!(input.completions.len(), 2);
+        assert!(input.completions[0].ends_with("foo_bar"));
+        assert!(input.completions[1].ends_with("foo_baz"));
+    }
+
+    #[test]
+    fn completion_directories_get_trailing_separator() {
+        let dir = tempfile::tempdir().unwrap();
+        std::fs::create_dir(dir.path().join("subdir")).unwrap();
+        std::fs::write(dir.path().join("file.txt"), "").unwrap();
+
+        let path = format!("{}/", dir.path().display());
+        let mut input = LineInput::new(&path);
+        input.handle(key(KeyCode::Tab));
+
+        // First completion is the directory (sorted first)
+        let sep = std::path::MAIN_SEPARATOR;
+        assert!(input.completions[0].ends_with(&format!("subdir{sep}")));
+        // File does not have trailing separator
+        assert!(input.completions[1].ends_with("file.txt"));
+        assert!(!input.completions[1].ends_with(&sep.to_string()));
+    }
+
+    #[test]
+    fn collect_completions_entry_error_sets_error_and_returns_empty() {
+        let mut input = LineInput::new("");
+        let entries: Vec<std::io::Result<(String, bool)>> = vec![
+            Ok(("alpha.txt".to_string(), false)),
+            Err(std::io::Error::new(std::io::ErrorKind::PermissionDenied, "mock")),
+            Ok(("beta.txt".to_string(), false)),
+        ];
+
+        let result = input.collect_completions(entries.into_iter(), "/some/dir/", "");
+        assert!(result.is_empty());
+        assert!(input.completion_error);
+    }
+
+    #[test]
+    fn collect_completions_ok_entries_no_error() {
+        let mut input = LineInput::new("");
+        let entries: Vec<std::io::Result<(String, bool)>> = vec![
+            Ok(("zeta".to_string(), false)),
+            Ok(("alpha_dir".to_string(), true)),
+            Ok(("beta".to_string(), false)),
+        ];
+
+        let result = input.collect_completions(entries.into_iter(), "pfx/", "");
+        assert!(!input.completion_error);
+        // dirs first, then files, alphabetical within each group
+        assert_eq!(result.len(), 3);
+        let sep = std::path::MAIN_SEPARATOR;
+        assert_eq!(result[0], format!("pfx/alpha_dir{sep}"));
+        assert_eq!(result[1], "pfx/beta");
+        assert_eq!(result[2], "pfx/zeta");
+    }
+
+    #[test]
+    fn collect_completions_scan_budget_caps_at_1000() {
+        let mut input = LineInput::new("");
+        // Create 1200 entries; only first 1000 should be scanned
+        let entries: Vec<std::io::Result<(String, bool)>> = (0..1200)
+            .map(|i| Ok((format!("file_{i:04}"), false)))
+            .collect();
+
+        let result = input.collect_completions(entries.into_iter(), "", "");
+        // Should have at most 100 (candidate cap) from the first 1000 scanned
+        assert!(result.len() <= 100);
+    }
+
+    #[test]
+    fn collect_completions_candidate_cap_at_100() {
+        let mut input = LineInput::new("");
+        // Create 200 matching entries
+        let entries: Vec<std::io::Result<(String, bool)>> = (0..200)
+            .map(|i| Ok((format!("item_{i:03}"), false)))
+            .collect();
+
+        let result = input.collect_completions(entries.into_iter(), "", "");
+        assert_eq!(result.len(), 100);
+    }
+
+    #[test]
+    fn completion_error_clears_on_non_tab_key() {
+        // Trigger a completion error
+        let mut input = LineInput::new("/nonexistent_zzz_dir/");
+        input.handle(key(KeyCode::Tab));
+        assert!(input.completion_error);
+
+        // Non-tab key clears it
+        input.handle(key(KeyCode::Left));
+        assert!(!input.completion_error);
+    }
+}

src/ui/mod.rs

@@ -1,3 +1,4 @@
 pub mod components;
 pub mod layout;
+pub mod line_input;
 pub mod theme;