From 4dd51f4a5f2037f8aa322fe7807315e6530a4ec8 Mon Sep 17 00:00:00 2001
From: Eric Traut <etraut@openai.com>
Date: Fri, 2 Oct 2026 06:41:33 +0000
Subject: [PATCH] Make transcript mouse scroll speed configurable (#50209)

## What changed

Add `tui.mouse_scroll_speed` as a finite positive multiplier for transcript mouse wheel scrolling, including transcript overlays and session previews. Change the default from three rows to one row per wheel event; set the multiplier to `3.0` to retain the previous speed.

Fractional values accumulate movement across events and discard the remainder when direction reverses. For example, `0.5` scrolls one row every two events. Following the latest output pauses only when a whole row moves.

## Testing

Add tests for configuration validation, integer and fractional scroll speeds, direction changes, decimal accumulation, and following behavior. Extend local settings coverage to include a command-line override for the new setting.

GitOrigin-RevId: d355e246fd943415f0ce5a6affe849f77f3615e6
---
 codex-rs/config/src/lib.rs                    |   1 +
 codex-rs/config/src/tui_mouse_scroll.rs       |  26 +++++
 codex-rs/config/src/types.rs                  |   6 +
 codex-rs/config/src/types_tests.rs            |  21 ++++
 codex-rs/core/config.schema.json              |   7 ++
 codex-rs/core/src/config/config_tests.rs      |   2 +
 codex-rs/core/src/config/mod.rs               |   4 +
 codex-rs/thread-manager-sample/src/main.rs    |   1 +
 codex-rs/tui/src/app/owned_transcript.rs      |   1 +
 ...pt__input_tests__plan_prompt_scrolled.snap |   4 +-
 codex-rs/tui/src/app/tests.rs                 |   1 +
 codex-rs/tui/src/app_backtrack.rs             |   1 +
 .../tui/src/clipboard_copy/worker_tests.rs    |   1 +
 codex-rs/tui/src/local_settings.rs            |   1 +
 codex-rs/tui/src/local_settings_tests.rs      |   4 +
 codex-rs/tui/src/pager_overlay.rs             |   2 +
 codex-rs/tui/src/resume_picker.rs             |   7 ++
 ...sts__wheel_stops_selection_autoscroll.snap |  16 +--
 codex-rs/tui/src/transcript_view.rs           |   4 +
 codex-rs/tui/src/transcript_view/input.rs     |  24 +++-
 .../tui/src/transcript_view/input_tests.rs    | 108 +++++++++++++++++-
 ...s_and_accumulates_fractional_movement.snap |  27 +++++
 22 files changed, 256 insertions(+), 13 deletions(-)
 create mode 100644 codex-rs/config/src/tui_mouse_scroll.rs
 create mode 100644 codex-rs/tui/src/transcript_view/snapshots/codex_tui__transcript_view__input__tests__mouse_scroll_speed_scales_rows_and_accumulates_fractional_movement.snap

diff --git a/codex-rs/config/src/lib.rs b/codex-rs/config/src/lib.rs
index d90d57ae87..681488a6b6 100644
--- a/codex-rs/config/src/lib.rs
+++ b/codex-rs/config/src/lib.rs
@@ -45,6 +45,7 @@ pub mod test_support;
 mod thread_config;
 mod tui_effects;
 mod tui_keymap;
+mod tui_mouse_scroll;
 mod tui_rendering;
 pub mod types;
 
diff --git a/codex-rs/config/src/tui_mouse_scroll.rs b/codex-rs/config/src/tui_mouse_scroll.rs
new file mode 100644
index 0000000000..345f994183
--- /dev/null
+++ b/codex-rs/config/src/tui_mouse_scroll.rs
@@ -0,0 +1,26 @@
+//! Keep transcript mouse-scroll speed validation and its configuration schema in sync.
+
+use schemars::JsonSchema;
+use schemars::r#gen::SchemaGenerator;
+use schemars::schema::Schema;
+use serde::Deserialize;
+use serde::Deserializer;
+
+pub(crate) fn schema(generator: &mut SchemaGenerator) -> Schema {
+    let mut schema = Option::<f64>::json_schema(generator).into_object();
+    schema.number().exclusive_minimum = Some(0.0);
+    schema.into()
+}
+
+pub(crate) fn deserialize<'de, D>(deserializer: D) -> Result<Option<f64>, D::Error>
+where
+    D: Deserializer<'de>,
+{
+    let speed = Option::<f64>::deserialize(deserializer)?;
+    if speed.is_some_and(|speed| !speed.is_finite() || speed <= 0.0) {
+        return Err(serde::de::Error::custom(
+            "tui.mouse_scroll_speed must be a finite positive number",
+        ));
+    }
+    Ok(speed)
+}
diff --git a/codex-rs/config/src/types.rs b/codex-rs/config/src/types.rs
index e16333c4a1..86d9134a2b 100644
--- a/codex-rs/config/src/types.rs
+++ b/codex-rs/config/src/types.rs
@@ -861,6 +861,12 @@ pub struct Tui {
     #[serde(default = "default_true")]
     pub fullscreen_transcript: bool,
 
+    /// Mouse wheel speed multiplier for transcript scrolling, based on one row per event.
+    /// Defaults to `1.0`. Positive fractional values slow scrolling; values above `1.0` speed it up.
+    #[serde(default, deserialize_with = "crate::tui_mouse_scroll::deserialize")]
+    #[schemars(schema_with = "crate::tui_mouse_scroll::schema")]
+    pub mouse_scroll_speed: Option<f64>,
+
     /// Copy selected transcript text when the mouse button is released.
     /// Defaults to `auto`: enabled except in direct terminals known to forward their native
     /// copy shortcut (Ghostty 1.2+, Kitty on macOS, Windows Terminal, and VS Code on Windows).
diff --git a/codex-rs/config/src/types_tests.rs b/codex-rs/config/src/types_tests.rs
index ab383ca193..5a9b3d81d9 100644
--- a/codex-rs/config/src/types_tests.rs
+++ b/codex-rs/config/src/types_tests.rs
@@ -1,6 +1,27 @@
 use super::*;
 use pretty_assertions::assert_eq;
 
+#[test]
+fn mouse_scroll_speed_accepts_integer_and_fractional_multipliers() {
+    for (value, expected) in [("1", 1.0), ("0.5", 0.5), ("3.0", 3.0)] {
+        let tui: Tui = toml::from_str(&format!("mouse_scroll_speed = {value}")).unwrap();
+        assert_eq!(tui.mouse_scroll_speed, Some(expected));
+    }
+}
+
+#[test]
+fn mouse_scroll_speed_rejects_nonpositive_and_nonfinite_values() {
+    for value in ["0", "-0.5", "nan", "inf", "-inf"] {
+        let error = toml::from_str::<Tui>(&format!("mouse_scroll_speed = {value}")).unwrap_err();
+        assert!(
+            error
+                .to_string()
+                .contains("tui.mouse_scroll_speed must be a finite positive number"),
+            "{error}"
+        );
+    }
+}
+
 #[test]
 fn deserialize_skill_config_with_name_selector() {
     let cfg: SkillConfig = toml::from_str(
diff --git a/codex-rs/core/config.schema.json b/codex-rs/core/config.schema.json
index 1c736947d8..1ab7592e96 100644
--- a/codex-rs/core/config.schema.json
+++ b/codex-rs/core/config.schema.json
@@ -4686,6 +4686,13 @@
           "default": {},
           "description": "Startup tooltip availability NUX state persisted by the TUI."
         },
+        "mouse_scroll_speed": {
+          "default": null,
+          "description": "Mouse wheel speed multiplier for transcript scrolling, based on one row per event. Defaults to `1.0`. Positive fractional values slow scrolling; values above `1.0` speed it up.",
+          "exclusiveMinimum": 0.0,
+          "format": "double",
+          "type": "number"
+        },
         "notification_condition": {
           "allOf": [
             {
diff --git a/codex-rs/core/src/config/config_tests.rs b/codex-rs/core/src/config/config_tests.rs
index 79ab58e75c..d07c42ff97 100644
--- a/codex-rs/core/src/config/config_tests.rs
+++ b/codex-rs/core/src/config/config_tests.rs
@@ -1269,6 +1269,7 @@ fn config_toml_deserializes_model_availability_nux() {
             question_esc_back: true,
             raw_output_mode: false,
             fullscreen_transcript: true,
+            mouse_scroll_speed: None,
             copy_on_select: Default::default(),
             right_click_paste: Default::default(),
             alternate_screen: AltScreenMode::default(),
@@ -4410,6 +4411,7 @@ fn tui_config_missing_notifications_field_defaults_to_enabled() {
             question_esc_back: true,
             raw_output_mode: false,
             fullscreen_transcript: true,
+            mouse_scroll_speed: None,
             copy_on_select: Default::default(),
             right_click_paste: Default::default(),
             alternate_screen: AltScreenMode::Auto,
diff --git a/codex-rs/core/src/config/mod.rs b/codex-rs/core/src/config/mod.rs
index fe06279954..704c949831 100644
--- a/codex-rs/core/src/config/mod.rs
+++ b/codex-rs/core/src/config/mod.rs
@@ -803,6 +803,9 @@ pub struct Config {
     /// Own the fullscreen transcript when the alternate screen is enabled.
     pub tui_fullscreen_transcript: bool,
 
+    /// Mouse wheel speed multiplier for transcript scrolling; defaults to one row per event.
+    pub tui_mouse_scroll_speed: Option<f64>,
+
     /// Override the terminal-specific default for copying transcript mouse selections.
     pub tui_copy_on_select: codex_config::types::CopyOnSelect,
 
@@ -4533,6 +4536,7 @@ impl Config {
                 .tui
                 .as_ref()
                 .is_none_or(|tui| tui.fullscreen_transcript),
+            tui_mouse_scroll_speed: cfg.tui.as_ref().and_then(|tui| tui.mouse_scroll_speed),
             tui_copy_on_select: cfg
                 .tui
                 .as_ref()
diff --git a/codex-rs/thread-manager-sample/src/main.rs b/codex-rs/thread-manager-sample/src/main.rs
index 1259a62b49..d2bec6be25 100644
--- a/codex-rs/thread-manager-sample/src/main.rs
+++ b/codex-rs/thread-manager-sample/src/main.rs
@@ -290,6 +290,7 @@ async fn new_config(
         tui_auto_recap: true,
         model_availability_nux: ModelAvailabilityNuxConfig::default(),
         tui_fullscreen_transcript: false,
+        tui_mouse_scroll_speed: None,
         tui_copy_on_select: Default::default(),
         tui_right_click_paste: Default::default(),
         tui_alternate_screen: AltScreenMode::Auto,
diff --git a/codex-rs/tui/src/app/owned_transcript.rs b/codex-rs/tui/src/app/owned_transcript.rs
index aa442e77ba..0893ad1791 100644
--- a/codex-rs/tui/src/app/owned_transcript.rs
+++ b/codex-rs/tui/src/app/owned_transcript.rs
@@ -42,6 +42,7 @@ impl App {
         let chat_widget = &self.chat_widget;
         let transcript_width = chat_widget.history_wrap_width(width);
         let view = &mut self.transcript_view;
+        view.mouse_scroll_speed = self.local_settings.tui.mouse_scroll_speed.unwrap_or(1.0);
         view.primary_selection = self.right_click_paste_environment.primary;
         view.copy_on_select = self
             .local_settings
diff --git a/codex-rs/tui/src/app/snapshots/codex_tui__app__owned_transcript__input_tests__plan_prompt_scrolled.snap b/codex-rs/tui/src/app/snapshots/codex_tui__app__owned_transcript__input_tests__plan_prompt_scrolled.snap
index e6e3ae62af..e01c019c45 100644
--- a/codex-rs/tui/src/app/snapshots/codex_tui__app__owned_transcript__input_tests__plan_prompt_scrolled.snap
+++ b/codex-rs/tui/src/app/snapshots/codex_tui__app__owned_transcript__input_tests__plan_prompt_scrolled.snap
@@ -2,8 +2,6 @@
 source: tui/src/app/owned_transcript_input_tests.rs
 expression: scrolled
 ---
-  • Plan step 27
-  • Plan step 28
   • Plan step 29
   • Plan step 30
   • Plan step 31
@@ -18,6 +16,8 @@ expression: scrolled
   • Plan step 40
 
 
+
+
   Implement this plan?
 
 
diff --git a/codex-rs/tui/src/app/tests.rs b/codex-rs/tui/src/app/tests.rs
index 68504517d0..26b3cc9c80 100644
--- a/codex-rs/tui/src/app/tests.rs
+++ b/codex-rs/tui/src/app/tests.rs
@@ -9757,6 +9757,7 @@ async fn clear_only_ui_reset_preserves_chat_session_state() {
         app.transcript_cells.clone(),
         crate::keymap::RuntimeKeymap::defaults().pager,
         /*copy_on_select*/ false,
+        /*mouse_scroll_speed*/ 1.0,
     ));
     app.deferred_history_lines = vec![Line::from("stale buffered line").into()];
     app.has_emitted_history_lines = true;
diff --git a/codex-rs/tui/src/app_backtrack.rs b/codex-rs/tui/src/app_backtrack.rs
index 3a555a808d..762cdb0fa6 100644
--- a/codex-rs/tui/src/app_backtrack.rs
+++ b/codex-rs/tui/src/app_backtrack.rs
@@ -171,6 +171,7 @@ impl App {
             self.keymap.pager.clone(),
             self.local_settings
                 .copy_on_select(&codex_terminal_detection::terminal_info()),
+            self.local_settings.tui.mouse_scroll_speed.unwrap_or(1.0),
         ));
         if self.scrollback_has_older_history
             && let Some(Overlay::Transcript(overlay)) = self.overlay.as_mut()
diff --git a/codex-rs/tui/src/clipboard_copy/worker_tests.rs b/codex-rs/tui/src/clipboard_copy/worker_tests.rs
index d030594fd1..1805813f53 100644
--- a/codex-rs/tui/src/clipboard_copy/worker_tests.rs
+++ b/codex-rs/tui/src/clipboard_copy/worker_tests.rs
@@ -82,6 +82,7 @@ async fn blocked_copy_allows_overlay_exit_rejects_backlog_and_wakes_completion()
         vec![Arc::new(PlainHistoryCell::new(vec!["selected".into()]))],
         RuntimeKeymap::defaults().pager,
         /*copy_on_select*/ false,
+        /*mouse_scroll_speed*/ 1.0,
     );
     overlay
         .handle_event(
diff --git a/codex-rs/tui/src/local_settings.rs b/codex-rs/tui/src/local_settings.rs
index 949e6f9e7f..b8c1dba6c5 100644
--- a/codex-rs/tui/src/local_settings.rs
+++ b/codex-rs/tui/src/local_settings.rs
@@ -68,6 +68,7 @@ impl LocalSettings {
                 question_esc_back: config.tui_question_esc_back,
                 raw_output_mode: config.tui_raw_output_mode,
                 fullscreen_transcript: config.tui_fullscreen_transcript,
+                mouse_scroll_speed: config.tui_mouse_scroll_speed,
                 copy_on_select: config.tui_copy_on_select,
                 right_click_paste: config.tui_right_click_paste,
                 alternate_screen: config.tui_alternate_screen,
diff --git a/codex-rs/tui/src/local_settings_tests.rs b/codex-rs/tui/src/local_settings_tests.rs
index 8b95d8898f..17c6a5310c 100644
--- a/codex-rs/tui/src/local_settings_tests.rs
+++ b/codex-rs/tui/src/local_settings_tests.rs
@@ -105,6 +105,7 @@ show_tooltips = false
 show_server_version_notice = false
 auto_recap = false
 fullscreen_transcript = true
+mouse_scroll_speed = 0.5
 copy_on_select = "never"
 right_click_paste = "off"
 vim_mode_default = true
@@ -136,6 +137,7 @@ fast_default_opt_out = true
             .cli_overrides(vec![
                 ("tui.disable_paste_burst".into(), true.into()),
                 ("tui.right_click_paste".into(), "on".into()),
+                ("tui.mouse_scroll_speed".into(), 1.5.into()),
                 // The deprecated flag must not override or migrate into the TUI preference.
                 (
                     "features.transcript_v2".into(),
@@ -145,12 +147,14 @@ fast_default_opt_out = true
             .build()
             .await?;
         assert_eq!(config.startup_warnings, Vec::<String>::new());
+        assert_eq!(config.tui_mouse_scroll_speed, Some(1.5));
         let bootstrap = crate::legacy_core::config::load_config_toml_with_layer_stack(
             home.path(),
             /*cwd*/ None,
             vec![
                 ("tui.disable_paste_burst".into(), true.into()),
                 ("tui.right_click_paste".into(), "on".into()),
+                ("tui.mouse_scroll_speed".into(), 1.5.into()),
                 (
                     "features.transcript_v2".into(),
                     config_text.is_empty().into(),
diff --git a/codex-rs/tui/src/pager_overlay.rs b/codex-rs/tui/src/pager_overlay.rs
index dde4e52f4e..685fff820e 100644
--- a/codex-rs/tui/src/pager_overlay.rs
+++ b/codex-rs/tui/src/pager_overlay.rs
@@ -52,9 +52,11 @@ impl Overlay {
         cells: Vec<Arc<dyn HistoryCell>>,
         keymap: PagerKeymap,
         copy_on_select: bool,
+        mouse_scroll_speed: f64,
     ) -> Self {
         let mut overlay = TranscriptOverlay::new(cells, keymap);
         overlay.view.copy_on_select = copy_on_select;
+        overlay.view.mouse_scroll_speed = mouse_scroll_speed;
         overlay.view.primary_selection = crate::clipboard_copy::primary::available();
         Self::Transcript(overlay)
     }
diff --git a/codex-rs/tui/src/resume_picker.rs b/codex-rs/tui/src/resume_picker.rs
index 5d904ee4d3..cef2cb9472 100644
--- a/codex-rs/tui/src/resume_picker.rs
+++ b/codex-rs/tui/src/resume_picker.rs
@@ -336,6 +336,7 @@ struct SessionPickerViewPersistence {
 struct SessionPickerRunOptions {
     use_theme_colors: bool,
     copy_on_select: bool,
+    mouse_scroll_speed: f64,
     show_all: bool,
     filter_cwd: Option<PathBuf>,
     local_filter_cwd: Option<PathBuf>,
@@ -447,6 +448,7 @@ async fn run_resume_picker_with_launch_context(
     let options = SessionPickerRunOptions {
         use_theme_colors: local_settings.tui.status_line_use_colors,
         copy_on_select: local_settings.copy_on_select(&codex_terminal_detection::terminal_info()),
+        mouse_scroll_speed: local_settings.tui.mouse_scroll_speed.unwrap_or(1.0),
         show_all,
         filter_cwd: cwd_filter,
         local_filter_cwd,
@@ -507,6 +509,7 @@ pub async fn run_fork_picker_with_app_server(
     let options = SessionPickerRunOptions {
         use_theme_colors: local_settings.tui.status_line_use_colors,
         copy_on_select: local_settings.copy_on_select(&codex_terminal_detection::terminal_info()),
+        mouse_scroll_speed: local_settings.tui.mouse_scroll_speed.unwrap_or(1.0),
         show_all,
         filter_cwd: cwd_filter,
         local_filter_cwd,
@@ -562,6 +565,7 @@ async fn run_session_picker_with_loader(
     state.local_filter_cwd = options.local_filter_cwd;
     state.use_theme_colors = options.use_theme_colors;
     state.copy_on_select = options.copy_on_select;
+    state.mouse_scroll_speed = options.mouse_scroll_speed;
     state.worktrees_enabled = options.worktrees_enabled;
     state.density = options.initial_density;
     state.view_persistence = options.view_persistence;
@@ -835,6 +839,7 @@ struct PickerState {
     clock_format: ClockFormat,
     use_theme_colors: bool,
     copy_on_select: bool,
+    mouse_scroll_speed: f64,
     // Resolve local filesystem membership once per cwd for each page-loading cycle.
     local_cwd_matches: HashMap<PathBuf, bool>,
     requester: FrameRequester,
@@ -1036,6 +1041,7 @@ impl PickerState {
             clock_format: ClockFormat::system(),
             use_theme_colors: true,
             copy_on_select: false,
+            mouse_scroll_speed: 1.0,
             requester,
             relative_time_reference: None,
             pagination: PaginationState::new(),
@@ -1141,6 +1147,7 @@ impl PickerState {
             cells.clone(),
             self.keymap.pager.clone(),
             self.copy_on_select,
+            self.mouse_scroll_speed,
         );
         if let Overlay::Transcript(view) = &mut overlay {
             view.set_keymap_bindings(&self.keymap);
diff --git a/codex-rs/tui/src/snapshots/codex_tui__transcript_view__tests__wheel_stops_selection_autoscroll.snap b/codex-rs/tui/src/snapshots/codex_tui__transcript_view__tests__wheel_stops_selection_autoscroll.snap
index e9d162d774..0b35d77570 100644
--- a/codex-rs/tui/src/snapshots/codex_tui__transcript_view__tests__wheel_stops_selection_autoscroll.snap
+++ b/codex-rs/tui/src/snapshots/codex_tui__transcript_view__tests__wheel_stops_selection_autoscroll.snap
@@ -2,16 +2,16 @@
 source: tui/src/transcript_view_tests.rs
 expression: "frames.join(\"\\n\\n\")"
 ---
-row 15
-row 16
-row 17
-row 18
 row 19
 row 20
+row 21
+row 22
+row 23
+row 24
 
+row 25
+row 26
+row 27
+row 28
 row 29
 row 30
-row 31
-row 32
-row 33
-row 34
diff --git a/codex-rs/tui/src/transcript_view.rs b/codex-rs/tui/src/transcript_view.rs
index 5a7a7e749e..9f04f3114a 100644
--- a/codex-rs/tui/src/transcript_view.rs
+++ b/codex-rs/tui/src/transcript_view.rs
@@ -85,6 +85,8 @@ struct VisibleRow {
 
 /// Shared scrolling and interaction state for compact and detailed transcript presentations.
 pub(crate) struct TranscriptView {
+    pub(crate) mouse_scroll_speed: f64,
+    pending_mouse_scroll: f64,
     pub(crate) copy_on_select: bool,
     pub(crate) primary_selection: bool,
     position: Position,
@@ -118,6 +120,8 @@ pub(crate) struct TranscriptView {
 impl Default for TranscriptView {
     fn default() -> Self {
         Self {
+            mouse_scroll_speed: 1.0,
+            pending_mouse_scroll: 0.0,
             copy_on_select: false,
             primary_selection: false,
             position: Position::Latest,
diff --git a/codex-rs/tui/src/transcript_view/input.rs b/codex-rs/tui/src/transcript_view/input.rs
index 6479eb2b11..d3d5be9f9c 100644
--- a/codex-rs/tui/src/transcript_view/input.rs
+++ b/codex-rs/tui/src/transcript_view/input.rs
@@ -3,6 +3,7 @@
 //! Shift-click extends the existing selection from its original text unit.
 //! Optional automatic copying happens only when a nonempty mouse selection is released.
 //! Automatic copies retain the selection; explicit copies clear it after confirmed delivery.
+//! Wheel input accumulates fractional rows and discards the remainder when direction reverses.
 
 use crate::key_hint::KeyBindingListExt;
 use crossterm::event::KeyCode;
@@ -232,8 +233,27 @@ impl TranscriptView {
             selection.pointer = None;
         }
         match event.kind {
-            MouseEventKind::ScrollUp => self.scroll(cells, /*rows*/ -3),
-            MouseEventKind::ScrollDown => self.scroll(cells, /*rows*/ 3),
+            MouseEventKind::ScrollUp | MouseEventKind::ScrollDown => {
+                let direction = if event.kind == MouseEventKind::ScrollUp {
+                    -1.0
+                } else {
+                    1.0
+                };
+                if self.pending_mouse_scroll.signum() != direction {
+                    self.pending_mouse_scroll = 0.0;
+                }
+                self.pending_mouse_scroll += direction * self.mouse_scroll_speed;
+                // Decimal speeds can land just short of a whole row after repeated addition.
+                let rounded = self.pending_mouse_scroll.round();
+                if rounded != 0.0 && (self.pending_mouse_scroll - rounded).abs() < 1e-9 {
+                    self.pending_mouse_scroll = rounded;
+                }
+                let rows = self.pending_mouse_scroll as isize;
+                self.pending_mouse_scroll = self.pending_mouse_scroll.fract();
+                if rows != 0 {
+                    self.scroll(cells, rows);
+                }
+            }
             MouseEventKind::Down(MouseButton::Right) if inside => {
                 return self
                     .selected_text(cells)
diff --git a/codex-rs/tui/src/transcript_view/input_tests.rs b/codex-rs/tui/src/transcript_view/input_tests.rs
index 45f408cce4..e996f0006c 100644
--- a/codex-rs/tui/src/transcript_view/input_tests.rs
+++ b/codex-rs/tui/src/transcript_view/input_tests.rs
@@ -1,9 +1,115 @@
-//! Link activation and selection extension share pointer gestures without losing selection anchors.
+//! Mouse gestures preserve selection anchors and accumulate fractional transcript scrolling.
 
 use super::*;
 use crate::history_cell::AgentMarkdownCell;
 use pretty_assertions::assert_eq;
 
+#[test]
+fn mouse_scroll_speed_scales_rows_and_accumulates_fractional_movement() {
+    use crate::history_cell::PlainHistoryCell;
+    use crate::transcript_view::tests::text;
+
+    let cells: Vec<Arc<dyn HistoryCell>> = vec![Arc::new(PlainHistoryCell::new(
+        (1..=24).map(|row| format!("row {row:02}").into()).collect(),
+    ))];
+    let area = Rect::new(
+        /*x*/ 0, /*y*/ 0, /*width*/ 12, /*height*/ 4,
+    );
+    let mut frames = Vec::new();
+    for (speed, deltas) in [
+        (None, vec![-1, 1]),
+        (Some(0.5), vec![0, -1, 0, 0, 1]),
+        (Some(1.5), vec![-1, -2, 1, 2]),
+        (Some(3.0), vec![-3, 3]),
+    ] {
+        let mut view = TranscriptView::default();
+        if let Some(speed) = speed {
+            view.mouse_scroll_speed = speed;
+        }
+        let mut buffer = Buffer::empty(area);
+        view.render(area, &mut buffer, &cells);
+        view.scroll(&cells, /*rows*/ -8);
+        view.render(area, &mut buffer, &cells);
+        let (index, mut row) = view.start(&cells);
+        let up_events = deltas.len().div_ceil(2);
+        for (event_index, delta) in deltas.into_iter().enumerate() {
+            let kind = if event_index < up_events {
+                MouseEventKind::ScrollUp
+            } else {
+                MouseEventKind::ScrollDown
+            };
+            view.handle_mouse(mouse(kind, /*column*/ 1, /*row*/ 1), &cells);
+            row = row.saturating_add_signed(delta);
+            assert_eq!(view.start(&cells), (index, row));
+            view.render(area, &mut buffer, &cells);
+            if event_index + 1 == up_events {
+                frames.push(format!(
+                    "speed {speed:?}, {up_events} up events:\n{}",
+                    text(&buffer)
+                ));
+            }
+        }
+    }
+    insta::assert_snapshot!(frames.join("\n\n"));
+}
+
+#[test]
+fn decimal_mouse_scroll_speeds_preserve_whole_rows() {
+    use crate::history_cell::PlainHistoryCell;
+
+    let cells: Vec<Arc<dyn HistoryCell>> = vec![Arc::new(PlainHistoryCell::new(
+        (1..=120)
+            .map(|row| format!("row {row:03}").into())
+            .collect(),
+    ))];
+    let area = Rect::new(
+        /*x*/ 0, /*y*/ 0, /*width*/ 12, /*height*/ 4,
+    );
+    for speed in [0.1, 0.3] {
+        let mut view = TranscriptView {
+            mouse_scroll_speed: speed,
+            ..TranscriptView::default()
+        };
+        view.render(area, &mut Buffer::empty(area), &cells);
+        view.scroll(&cells, /*rows*/ -40);
+        let (index, row) = view.start(&cells);
+        for (kind, direction) in [
+            (MouseEventKind::ScrollUp, -1),
+            (MouseEventKind::ScrollDown, 1),
+        ] {
+            let (_, start_row) = view.start(&cells);
+            for event in 1..=100 {
+                view.handle_mouse(mouse(kind, /*column*/ 1, /*row*/ 1), &cells);
+                let rows = (f64::from(event) * speed).floor() as isize * direction;
+                assert_eq!(
+                    view.start(&cells),
+                    (index, start_row.saturating_add_signed(rows))
+                );
+            }
+        }
+        assert_eq!(view.start(&cells), (index, row));
+    }
+}
+
+#[test]
+fn fractional_mouse_scroll_does_not_pause_following_until_a_row_moves() {
+    let (mut view, cells) = transcript(
+        "one\n\ntwo\n\nthree\n\nfour\n\nfive\n\nsix",
+        /*width*/ 12,
+    );
+    view.mouse_scroll_speed = 0.5;
+    view.handle_mouse(
+        mouse(MouseEventKind::ScrollUp, /*column*/ 4, /*row*/ 1),
+        &cells,
+    );
+    assert!(view.is_following());
+    view.handle_mouse(
+        mouse(MouseEventKind::ScrollUp, /*column*/ 4, /*row*/ 1),
+        &cells,
+    );
+    assert!(!view.is_following());
+}
+
 fn transcript(markdown: &str, width: u16) -> (TranscriptView, Vec<Arc<dyn HistoryCell>>) {
     let cells: Vec<Arc<dyn HistoryCell>> = vec![Arc::new(AgentMarkdownCell::new(
         markdown.into(),
diff --git a/codex-rs/tui/src/transcript_view/snapshots/codex_tui__transcript_view__input__tests__mouse_scroll_speed_scales_rows_and_accumulates_fractional_movement.snap b/codex-rs/tui/src/transcript_view/snapshots/codex_tui__transcript_view__input__tests__mouse_scroll_speed_scales_rows_and_accumulates_fractional_movement.snap
new file mode 100644
index 0000000000..11d34d24a2
--- /dev/null
+++ b/codex-rs/tui/src/transcript_view/snapshots/codex_tui__transcript_view__input__tests__mouse_scroll_speed_scales_rows_and_accumulates_fractional_movement.snap
@@ -0,0 +1,27 @@
+---
+source: tui/src/transcript_view/input_tests.rs
+expression: "frames.join(\"\\n\\n\")"
+---
+speed None, 1 up events:
+row 12
+row 13
+row 14
+row 15
+
+speed Some(0.5), 3 up events:
+row 12
+row 13
+row 14
+row 15
+
+speed Some(1.5), 2 up events:
+row 10
+row 11
+row 12
+row 13
+
+speed Some(3.0), 1 up events:
+row 10
+row 11
+row 12
+row 13