diff --git a/packages/coding-agent/CHANGELOG.md b/packages/coding-agent/CHANGELOG.md
index dfcf52f63..d776b1056 100644
--- a/packages/coding-agent/CHANGELOG.md
+++ b/packages/coding-agent/CHANGELOG.md
@@ -4,6 +4,7 @@
 
 ### Added
 
+- Added the `fullscreenWheelScrollLines` setting and `/settings` entry for fullscreen mouse-wheel scrolling. The default `"auto"` accelerates fast wheel spins outside local macOS terminals ([#9758](https://github.com/earendil-works/pi/issues/9758)).
 - Added per-input disposition to successful RPC `prompt`, `steer`, and `follow_up` responses, `AgentSession.steer()`/`followUp()`, and `RpcClient.prompt()`/`steer()`/`followUp()`; `RpcClient.prompt()` also accepts `streamingBehavior` ([#9098](https://github.com/earendil-works/pi/issues/9098), [#9803](https://github.com/earendil-works/pi/issues/9803)).
 - Added image generation to `ModelRuntime`: `generateImages()` with runtime-resolved auth (stored credentials, OAuth, runtime API keys, `models.json` headers), plus `getModelsOfType()`, `getModelOfType()`, `getAvailableOfType()`, `getAllModels()`, and `getAllAvailable()`. OpenRouter image models are listed under the `openrouter` provider and share its credential; an upstream ID can have separate chat and image entries. `models.json` providers and extension registrations without a model list keep built-in image generation. Extension model lists can include discriminated chat, image, and classifier entries with operation implementations; when supplied, they replace the provider catalog across every operation. Chat-facing reads (`getModels()`, `getAvailableSnapshot()`, the model picker) are unchanged.
 - Added classifier support to `ModelRuntime`, including `classify()`, classifier model accessors, runtime-resolved authentication, and the built-in TypeSafe `jev-latest` model.
diff --git a/packages/coding-agent/docs/settings.md b/packages/coding-agent/docs/settings.md
index 481885f9b..d861ba306 100644
--- a/packages/coding-agent/docs/settings.md
+++ b/packages/coding-agent/docs/settings.md
@@ -81,6 +81,7 @@ See [Compaction Reference](compaction.md) for trigger, summarization, and valida
 | `fullscreenExitOutput` | `"transcript" \| "resume-hint"` | `"transcript"` | Output printed when fullscreen mode exits. |
 | `fullscreenScrollbar` | `"auto" \| "always" \| "hidden"` | `"auto"` | Fullscreen transcript scrollbar behavior. |
 | `fullscreenCopyOnSelect` | boolean | `true` | Copy selected text automatically in fullscreen mode. |
+| `fullscreenWheelScrollLines` | `"auto"` \| number | `"auto"` | Lines per mouse-wheel event in fullscreen mode, from 1 to 100. `"auto"` moves one line per event in local macOS terminals, which already accelerate wheel and trackpad input; elsewhere, and over SSH, it speeds up fast wheel spins to at most 6 lines per event. Alt+wheel moves five times as far. |
 | `editorPaddingX` | number | `0` | Horizontal editor padding from 0 to 3 cells. |
 | `outputPad` | `0 \| 1` | `1` | Horizontal transcript padding. |
 | `autocompleteMaxVisible` | number | `5` | Visible autocomplete entries, from 3 to 20. |
diff --git a/packages/coding-agent/src/core/settings-manager.ts b/packages/coding-agent/src/core/settings-manager.ts
index cbb6445f8..ad42061ff 100644
--- a/packages/coding-agent/src/core/settings-manager.ts
+++ b/packages/coding-agent/src/core/settings-manager.ts
@@ -1,6 +1,11 @@
 import type { ThinkingLevel } from "@earendil-works/pi-agent-core";
 import { DEFAULT_MAX_AGENT_RETRY_DELAY_MS, type Model, type Transport } from "@earendil-works/pi-ai";
-import type { TuiMode as RendererTuiMode, ScrollViewScrollbar, TerminalCapabilities } from "@earendil-works/pi-tui";
+import type {
+	TuiMode as RendererTuiMode,
+	ScrollViewScrollbar,
+	TerminalCapabilities,
+	WheelScrollLines,
+} from "@earendil-works/pi-tui";
 import { randomUUID } from "crypto";
 import { existsSync, mkdirSync, readFileSync, writeFileSync } from "fs";
 import { dirname, join } from "path";
@@ -177,6 +182,7 @@ export interface Settings {
 	fullscreenExitOutput?: FullscreenExitOutput; // default: "transcript"; no effect in regular TUI mode
 	fullscreenScrollbar?: ScrollViewScrollbar; // default: "auto"; no effect in regular TUI mode
 	fullscreenCopyOnSelect?: boolean; // default: true; no effect in regular TUI mode
+	fullscreenWheelScrollLines?: WheelScrollLines; // default: "auto"; lines per wheel event, 1-100
 }
 
 function isMergeableObject(value: unknown): value is Record<string, unknown> {
@@ -1325,6 +1331,20 @@ export class SettingsManager {
 		this.save();
 	}
 
+	getFullscreenWheelScrollLines(): WheelScrollLines {
+		const lines = this.settings.fullscreenWheelScrollLines;
+		return typeof lines === "number" && Number.isFinite(lines)
+			? Math.max(1, Math.min(100, Math.floor(lines)))
+			: "auto";
+	}
+
+	setFullscreenWheelScrollLines(lines: WheelScrollLines): void {
+		this.globalSettings.fullscreenWheelScrollLines =
+			lines === "auto" ? lines : Math.max(1, Math.min(100, Math.floor(lines)));
+		this.markModified("fullscreenWheelScrollLines");
+		this.save();
+	}
+
 	getImageAutoResize(): boolean {
 		return this.settings.images?.autoResize ?? true;
 	}
diff --git a/packages/coding-agent/src/experimental/client-tui.ts b/packages/coding-agent/src/experimental/client-tui.ts
index e8cf9fed0..6bc810d8d 100644
--- a/packages/coding-agent/src/experimental/client-tui.ts
+++ b/packages/coding-agent/src/experimental/client-tui.ts
@@ -744,6 +744,7 @@ export async function runClientTui(command: ClientCommand, options: RunClientTui
 		tuiMode: "fullscreen",
 		showHardwareCursor: settingsManager.getShowHardwareCursor(),
 		logDirectory: agentDir,
+		fullscreenWheelScrollLines: settingsManager.getFullscreenWheelScrollLines(),
 	});
 	tui.setClearOnShrink(settingsManager.getClearOnShrink());
 	let component: ExperimentalClientTui | undefined;
diff --git a/packages/coding-agent/src/modes/interactive/components/settings-selector.ts b/packages/coding-agent/src/modes/interactive/components/settings-selector.ts
index 618d24e80..dc735f94b 100644
--- a/packages/coding-agent/src/modes/interactive/components/settings-selector.ts
+++ b/packages/coding-agent/src/modes/interactive/components/settings-selector.ts
@@ -10,6 +10,7 @@ import {
 	SettingsList,
 	Spacer,
 	Text,
+	type WheelScrollLines,
 } from "@earendil-works/pi-tui";
 import { formatHttpIdleTimeoutMs, HTTP_IDLE_TIMEOUT_CHOICES } from "../../../core/http-dispatcher.ts";
 import {
@@ -94,6 +95,7 @@ export interface SettingsConfig {
 	fullscreenExitOutput: FullscreenExitOutput;
 	fullscreenScrollbar: ScrollViewScrollbar;
 	fullscreenCopyOnSelect: boolean;
+	fullscreenWheelScrollLines: WheelScrollLines;
 	warnings: WarningSettings;
 }
 
@@ -132,6 +134,7 @@ export interface SettingsCallbacks {
 	onFullscreenExitOutputChange: (output: FullscreenExitOutput) => void;
 	onFullscreenScrollbarChange: (mode: ScrollViewScrollbar) => void;
 	onFullscreenCopyOnSelectChange: (enabled: boolean) => void;
+	onFullscreenWheelScrollLinesChange: (lines: WheelScrollLines) => void;
 	onWarningsChange: (warnings: WarningSettings) => void;
 	onCancel: () => void;
 }
@@ -726,6 +729,20 @@ export class SettingsSelectorComponent extends Container {
 				currentValue: config.fullscreenCopyOnSelect ? "true" : "false",
 				values: ["true", "false"],
 			},
+			{
+				id: "fullscreen-wheel-scroll-lines",
+				label: "Fullscreen wheel scrolling",
+				description:
+					"Lines per mouse-wheel event in fullscreen mode; 'auto' speeds up fast wheel spins where the terminal does not",
+				currentValue: String(config.fullscreenWheelScrollLines),
+				values: [
+					"auto",
+					...[...new Set([1, 2, 3, 5, 10, config.fullscreenWheelScrollLines])]
+						.filter((lines) => lines !== "auto")
+						.sort((a, b) => a - b)
+						.map(String),
+				],
+			},
 			{
 				id: "theme",
 				label: "Theme",
@@ -953,6 +970,9 @@ export class SettingsSelectorComponent extends Container {
 					case "fullscreen-copy-on-select":
 						callbacks.onFullscreenCopyOnSelectChange(newValue === "true");
 						break;
+					case "fullscreen-wheel-scroll-lines":
+						callbacks.onFullscreenWheelScrollLinesChange(newValue === "auto" ? "auto" : parseInt(newValue, 10));
+						break;
 					case "theme":
 						callbacks.onThemeChange(newValue);
 						break;
diff --git a/packages/coding-agent/src/modes/interactive/interactive-mode.ts b/packages/coding-agent/src/modes/interactive/interactive-mode.ts
index 3056b910d..25c5be24a 100644
--- a/packages/coding-agent/src/modes/interactive/interactive-mode.ts
+++ b/packages/coding-agent/src/modes/interactive/interactive-mode.ts
@@ -590,6 +590,7 @@ export class InteractiveMode {
 			terminal: options.terminal,
 			onRightClickPaste: this.onRightClickPaste,
 			fullscreenCopyOnSelect: this.settingsManager.getFullscreenCopyOnSelect(),
+			fullscreenWheelScrollLines: this.settingsManager.getFullscreenWheelScrollLines(),
 		});
 		this.ui = createInteractiveTuiReference(() => this.renderer);
 		this.ui.setClearOnShrink(this.settingsManager.getClearOnShrink());
@@ -876,6 +877,7 @@ export class InteractiveMode {
 			terminal,
 			onRightClickPaste: this.onRightClickPaste,
 			fullscreenCopyOnSelect: this.settingsManager.getFullscreenCopyOnSelect(),
+			fullscreenWheelScrollLines: this.settingsManager.getFullscreenWheelScrollLines(),
 		});
 		nextUi.setClearOnShrink(clearOnShrink);
 		nextUi.onDebug = onDebug;
@@ -1995,6 +1997,7 @@ export class InteractiveMode {
 		this.applyFullscreenScrollbarSetting();
 		if (this.renderer instanceof TuiAltScreen) {
 			this.renderer.setCopyOnSelect(this.settingsManager.getFullscreenCopyOnSelect());
+			this.renderer.setWheelScrollLines(this.settingsManager.getFullscreenWheelScrollLines());
 		}
 		this.footer.setSession(this.session);
 		this.footer.setAutoCompactEnabled(this.session.autoCompactionEnabled);
@@ -4818,6 +4821,7 @@ export class InteractiveMode {
 					fullscreenExitOutput: this.settingsManager.getFullscreenExitOutput(),
 					fullscreenScrollbar: this.settingsManager.getFullscreenScrollbar(),
 					fullscreenCopyOnSelect: this.settingsManager.getFullscreenCopyOnSelect(),
+					fullscreenWheelScrollLines: this.settingsManager.getFullscreenWheelScrollLines(),
 					warnings: this.settingsManager.getWarnings(),
 				},
 				{
@@ -4998,6 +5002,10 @@ export class InteractiveMode {
 						this.settingsManager.setFullscreenCopyOnSelect(enabled);
 						if (this.renderer instanceof TuiAltScreen) this.renderer.setCopyOnSelect(enabled);
 					},
+					onFullscreenWheelScrollLinesChange: (lines) => {
+						this.settingsManager.setFullscreenWheelScrollLines(lines);
+						if (this.renderer instanceof TuiAltScreen) this.renderer.setWheelScrollLines(lines);
+					},
 					onWarningsChange: (warnings) => {
 						this.settingsManager.setWarnings(warnings);
 					},
diff --git a/packages/coding-agent/src/modes/interactive/tui-renderer.ts b/packages/coding-agent/src/modes/interactive/tui-renderer.ts
index 86c634c2b..6487c1c6f 100644
--- a/packages/coding-agent/src/modes/interactive/tui-renderer.ts
+++ b/packages/coding-agent/src/modes/interactive/tui-renderer.ts
@@ -1,4 +1,4 @@
-import type { Terminal } from "@earendil-works/pi-tui";
+import type { Terminal, WheelScrollLines } from "@earendil-works/pi-tui";
 import { ProcessTerminal, type TUI, TuiAltScreen, TuiMainScreen } from "@earendil-works/pi-tui";
 import { copyToClipboard } from "../../utils/clipboard.ts";
 import { openBrowser } from "../../utils/open-browser.ts";
@@ -12,6 +12,7 @@ export interface InteractiveTuiOptions {
 	readonly terminal?: Terminal;
 	readonly onRightClickPaste?: () => void;
 	readonly fullscreenCopyOnSelect?: boolean;
+	readonly fullscreenWheelScrollLines?: WheelScrollLines;
 }
 
 /** Composition root shared by coding-agent presentations. */
@@ -34,6 +35,7 @@ export function createInteractiveTui(options: InteractiveTuiOptions): TuiMainScr
 			openUrl: openBrowser,
 			onRightClickPaste: options.onRightClickPaste,
 			copyOnSelect: options.fullscreenCopyOnSelect,
+			wheelScrollLines: options.fullscreenWheelScrollLines ?? "auto",
 			copySelection: async (text) => {
 				try {
 					await copyToClipboard(text);
diff --git a/packages/coding-agent/test/interactive-tui.test.ts b/packages/coding-agent/test/interactive-tui.test.ts
index b9b18f8b2..559edfe36 100644
--- a/packages/coding-agent/test/interactive-tui.test.ts
+++ b/packages/coding-agent/test/interactive-tui.test.ts
@@ -1,4 +1,4 @@
-import type { Component, Terminal, TUI } from "@earendil-works/pi-tui";
+import type { Component, Terminal, TUI, WheelScrollLines } from "@earendil-works/pi-tui";
 import { Container, getKeybindings, isViewportTUI, ScrollView, setKeybindings, Text } from "@earendil-works/pi-tui";
 import { beforeEach, describe, expect, it, vi } from "vitest";
 import { VirtualTerminal } from "../../tui/test/virtual-terminal.ts";
@@ -127,7 +127,14 @@ describe("createInteractiveTui", () => {
 		renderer.setFocus(component);
 
 		type SwitchContext = {
-			runtimeHost: { session: { settingsManager: { getFullscreenCopyOnSelect: () => boolean } } };
+			runtimeHost: {
+				session: {
+					settingsManager: {
+						getFullscreenCopyOnSelect: () => boolean;
+						getFullscreenWheelScrollLines: () => WheelScrollLines;
+					};
+				};
+			};
 			renderer: ReturnType<typeof createInteractiveTui>;
 			ui: TUI;
 			fullscreenLayoutRoot: Component;
@@ -136,7 +143,11 @@ describe("createInteractiveTui", () => {
 			extensionTerminalInputSubscriptions: Set<never>;
 		};
 		const context = Object.assign(Object.create(InteractiveMode.prototype), {
-			runtimeHost: { session: { settingsManager: { getFullscreenCopyOnSelect: () => true } } },
+			runtimeHost: {
+				session: {
+					settingsManager: { getFullscreenCopyOnSelect: () => true, getFullscreenWheelScrollLines: () => "auto" },
+				},
+			},
 			renderer,
 			ui: undefined as unknown as TUI,
 			fullscreenLayoutRoot: component,
diff --git a/packages/coding-agent/test/settings-manager.test.ts b/packages/coding-agent/test/settings-manager.test.ts
index 8e1bb83ad..457fba396 100644
--- a/packages/coding-agent/test/settings-manager.test.ts
+++ b/packages/coding-agent/test/settings-manager.test.ts
@@ -516,6 +516,27 @@ describe("SettingsManager", () => {
 		expect(reloadedManager.getFullscreenCopyOnSelect()).toBe(true);
 	});
 
+	// #9758: wheel scrolling defaults to auto, persists line counts, and ignores invalid values.
+	it("persists fullscreen wheel scroll lines", async () => {
+		const manager = SettingsManager.create(projectDir, agentDir);
+		expect(manager.getFullscreenWheelScrollLines()).toBe("auto");
+
+		manager.setFullscreenWheelScrollLines(3);
+		await manager.flush();
+		expect(JSON.parse(readFileSync(join(agentDir, "settings.json"), "utf-8")).fullscreenWheelScrollLines).toBe(3);
+
+		for (const [value, expected] of [
+			[7.9, 7],
+			[0, 1],
+			[1000, 100],
+			["fast", "auto"],
+			[null, "auto"],
+		] as const) {
+			writeFileSync(join(agentDir, "settings.json"), JSON.stringify({ fullscreenWheelScrollLines: value }));
+			expect(SettingsManager.create(projectDir, agentDir).getFullscreenWheelScrollLines()).toBe(expected);
+		}
+	});
+
 	describe("outputPad", () => {
 		it("should default to 1 and persist binary values", async () => {
 			const manager = SettingsManager.create(projectDir, agentDir);
diff --git a/packages/coding-agent/test/settings-selector.test.ts b/packages/coding-agent/test/settings-selector.test.ts
index 71619d100..669bb6e5d 100644
--- a/packages/coding-agent/test/settings-selector.test.ts
+++ b/packages/coding-agent/test/settings-selector.test.ts
@@ -26,10 +26,12 @@ describe("SettingsSelectorComponent", () => {
 		const onExitOutputChange = vi.fn();
 		const onScrollbarChange = vi.fn();
 		const onCopyOnSelectChange = vi.fn();
+		const onWheelScrollLinesChange = vi.fn();
 		const config = {
 			fullscreenExitOutput: "transcript",
 			fullscreenScrollbar: "auto",
 			fullscreenCopyOnSelect: true,
+			fullscreenWheelScrollLines: 7,
 			warnings: {},
 			defaultModel: "not set",
 			availableDefaultModels: [],
@@ -41,6 +43,7 @@ describe("SettingsSelectorComponent", () => {
 			onFullscreenExitOutputChange: onExitOutputChange,
 			onFullscreenScrollbarChange: onScrollbarChange,
 			onFullscreenCopyOnSelectChange: onCopyOnSelectChange,
+			onFullscreenWheelScrollLinesChange: onWheelScrollLinesChange,
 		} as unknown as SettingsCallbacks;
 
 		const cycle = (label: string, count: number) => {
@@ -55,6 +58,9 @@ describe("SettingsSelectorComponent", () => {
 		expect(onScrollbarChange.mock.calls.flat()).toEqual(["always", "hidden", "auto"]);
 		cycle("Fullscreen copy on select", 2);
 		expect(onCopyOnSelectChange.mock.calls.flat()).toEqual([false, true]);
+		// #9758: custom values from settings.json stay in the cycle.
+		cycle("Fullscreen wheel scrolling", 3);
+		expect(onWheelScrollLinesChange.mock.calls.flat()).toEqual([10, "auto", 1]);
 	});
 
 	it("keeps the configured fixed theme marked while browsing", () => {
diff --git a/packages/tui/CHANGELOG.md b/packages/tui/CHANGELOG.md
index 80b0b70b1..86b7eb823 100644
--- a/packages/tui/CHANGELOG.md
+++ b/packages/tui/CHANGELOG.md
@@ -2,6 +2,10 @@
 
 ## [Unreleased]
 
+### Added
+
+- Added `"auto"` to `TuiAltScreenOptions.wheelScrollLines`, which accelerates fast wheel spins on terminals that send one event per notch, and `TuiAltScreen.setWheelScrollLines()` for runtime updates ([#9758](https://github.com/earendil-works/pi/issues/9758)).
+
 ### Fixed
 
 - Fixed `/skill` autocomplete appearing empty when loaded skill names did not contain the letters in `skill` ([#9944](https://github.com/earendil-works/pi/issues/9944)).
diff --git a/packages/tui/src/index.ts b/packages/tui/src/index.ts
index 06a8ee086..93fb8b727 100644
--- a/packages/tui/src/index.ts
+++ b/packages/tui/src/index.ts
@@ -183,3 +183,4 @@ export {
 	visibleWidth,
 	wrapTextWithAnsi,
 } from "./utils.ts";
+export type { WheelScrollLines } from "./wheel-scroll.ts";
diff --git a/packages/tui/src/tui-alt-screen.ts b/packages/tui/src/tui-alt-screen.ts
index cc9a04f43..bf8affb13 100644
--- a/packages/tui/src/tui-alt-screen.ts
+++ b/packages/tui/src/tui-alt-screen.ts
@@ -57,6 +57,7 @@ import {
 	truncateToWidth,
 	visibleWidth,
 } from "./utils.ts";
+import { WheelScrollAccelerator, type WheelScrollLines } from "./wheel-scroll.ts";
 
 const ENTER_ALT_SCREEN = "\x1b[?1049h";
 const EXIT_ALT_SCREEN = "\x1b[?1049l";
@@ -164,8 +165,11 @@ interface SearchHighlightRange {
 }
 
 export interface TuiAltScreenOptions {
-	/** Number of logical lines moved for each mouse-wheel event. */
-	wheelScrollLines?: number;
+	/**
+	 * Logical lines moved for each mouse-wheel event (default: 1). `"auto"` accelerates fast wheel
+	 * spins on terminals that send one event per notch. Alt+wheel moves five times as far.
+	 */
+	wheelScrollLines?: WheelScrollLines;
 	/** Capture mouse events for viewport scrolling and application-owned text selection. */
 	mouse?: boolean;
 	/** Style a non-current transcript search match. */
@@ -236,7 +240,7 @@ export class TuiAltScreen extends TuiBase implements ViewportTUI {
 		x: number;
 		y: number;
 	};
-	private readonly wheelScrollLines: number;
+	private readonly wheelScroll: WheelScrollAccelerator;
 	private readonly mouseEnabled: boolean;
 	private readonly searchMatchStyle: (text: string) => string;
 	private readonly searchCurrentMatchStyle: (text: string) => string;
@@ -263,7 +267,7 @@ export class TuiAltScreen extends TuiBase implements ViewportTUI {
 		};
 		this.implicitScrollView = new ScrollView(this.implicitDocument, { follow: "end", primary: true });
 		this.flashes = new AltScreenFlashContainer(() => this.requestRender());
-		this.wheelScrollLines = Math.max(1, Math.floor(options.wheelScrollLines ?? 1));
+		this.wheelScroll = new WheelScrollAccelerator(options.wheelScrollLines ?? 1);
 		this.mouseEnabled = options.mouse ?? true;
 		this.searchMatchStyle = options.searchMatchStyle ?? ((text) => `\x1b[4m${text}\x1b[24m`);
 		this.searchCurrentMatchStyle = options.searchCurrentMatchStyle ?? ((text) => `\x1b[1;7m${text}\x1b[22;27m`);
@@ -284,6 +288,10 @@ export class TuiAltScreen extends TuiBase implements ViewportTUI {
 		return this.getPrimaryScrollView().isFollowingEnd;
 	}
 
+	setWheelScrollLines(lines: WheelScrollLines): void {
+		this.wheelScroll.setLines(lines);
+	}
+
 	getCopyOnSelect(): boolean {
 		return this.copyOnSelect;
 	}
@@ -682,9 +690,11 @@ export class TuiAltScreen extends TuiBase implements ViewportTUI {
 
 		const wheelEvent = this.parseWheelEvent(data);
 		if (wheelEvent) {
-			const event = this.createMouseEvent("wheel", wheelEvent.button, wheelEvent.x, wheelEvent.y, {
-				wheelDelta: wheelEvent.direction * this.getWheelScrollLines(wheelEvent.button),
-			});
+			const lines = this.wheelScroll.next(wheelEvent.direction, performance.now());
+			// SGR mouse button codes use bit 3 (value 8) for the Alt modifier.
+			const wheelDelta =
+				wheelEvent.direction * ((wheelEvent.button & 8) !== 0 ? lines * ALT_WHEEL_SCROLL_MULTIPLIER : lines);
+			const event = this.createMouseEvent("wheel", wheelEvent.button, wheelEvent.x, wheelEvent.y, { wheelDelta });
 			const overlay = this.dispatchMouseToOverlay(event);
 			const result = overlay.result ?? (overlay.hit ? undefined : this.dispatchMouseToLayout(event));
 			if (result) {
@@ -692,7 +702,7 @@ export class TuiAltScreen extends TuiBase implements ViewportTUI {
 				return { consume: true };
 			}
 			if (this.shouldDeferViewportInputToOverlay()) return undefined;
-			this.routeWheel(wheelEvent);
+			this.routeWheel(wheelEvent, wheelDelta);
 			return { consume: true };
 		}
 		const mouseEvent = this.parseSgrMouseEvent(data);
@@ -967,13 +977,8 @@ export class TuiAltScreen extends TuiBase implements ViewportTUI {
 		return undefined;
 	}
 
-	private getWheelScrollLines(button: number): number {
-		// SGR mouse button codes use bit 3 (value 8) for the Alt modifier.
-		return (button & 8) !== 0 ? this.wheelScrollLines * ALT_WHEEL_SCROLL_MULTIPLIER : this.wheelScrollLines;
-	}
-
-	private routeWheel(event: WheelEvent): void {
-		let remaining = event.direction * this.getWheelScrollLines(event.button);
+	private routeWheel(event: WheelEvent, delta: number): void {
+		let remaining = delta;
 		const seen = new Set<ScrollView>();
 		for (const scrollView of this.currentLayout ? getScrollViewsAt(this.currentLayout, event.x, event.y) : []) {
 			seen.add(scrollView);
diff --git a/packages/tui/src/wheel-scroll.ts b/packages/tui/src/wheel-scroll.ts
new file mode 100644
index 000000000..a6c0018bd
--- /dev/null
+++ b/packages/tui/src/wheel-scroll.ts
@@ -0,0 +1,82 @@
+/** Lines moved per mouse-wheel event, or `"auto"` to accelerate fast wheel spins. */
+export type WheelScrollLines = number | "auto";
+
+// Several events closer than this belong to one physical notch (Ghostty emits them ~4 ms apart)
+// or come from a high-resolution source. They move one line each and do not accelerate.
+const BURST_GAP_MS = 5;
+// A pause longer than this ends a scroll gesture.
+const GESTURE_GAP_MS = 200;
+// Average event gap that maps to one line per event. Faster events scale up proportionally.
+const REFERENCE_GAP_MS = 100;
+const MAX_AUTO_LINES = 6;
+
+/**
+ * Local macOS terminals receive wheel and trackpad deltas that the OS has already accelerated,
+ * and they emit one event per line. Other platforms, and SSH sessions where the client platform
+ * is unknown, usually send one event per wheel notch.
+ */
+function terminalAcceleratesWheel(): boolean {
+	const env = process.env;
+	return (
+		process.platform === "darwin" &&
+		env.SSH_CONNECTION === undefined &&
+		env.SSH_CLIENT === undefined &&
+		env.SSH_TTY === undefined
+	);
+}
+
+/**
+ * Converts wheel events into line counts.
+ *
+ * In `"auto"` mode on terminals that do not accelerate wheel input, the count follows event
+ * velocity: an isolated notch moves one line, while a fast spin moves up to six lines per event.
+ * For example, notches 100 ms apart move 1 line each, 50 ms apart move 2, and 20 ms apart move 5.
+ */
+export class WheelScrollAccelerator {
+	private lines: WheelScrollLines;
+	private readonly accelerate: boolean;
+	private lastTime = Number.NEGATIVE_INFINITY;
+	private lastDirection = 0;
+	private averageGap: number | undefined;
+	private carry = 0;
+
+	constructor(lines: WheelScrollLines = "auto", accelerate = !terminalAcceleratesWheel()) {
+		this.lines = lines;
+		this.accelerate = accelerate;
+	}
+
+	setLines(lines: WheelScrollLines): void {
+		this.lines = lines;
+		this.reset();
+	}
+
+	/** Return the positive line count for a wheel event in `direction` at time `now` (milliseconds). */
+	next(direction: -1 | 1, now: number): number {
+		if (this.lines !== "auto") return Number.isFinite(this.lines) ? Math.max(1, Math.floor(this.lines)) : 1;
+		if (!this.accelerate) return 1;
+
+		const gap = now - this.lastTime;
+		const sameGesture = direction === this.lastDirection && gap <= GESTURE_GAP_MS;
+		this.lastTime = now;
+		this.lastDirection = direction;
+		if (!sameGesture) {
+			this.averageGap = undefined;
+			this.carry = 0;
+			return 1;
+		}
+		if (gap < BURST_GAP_MS) return 1;
+
+		this.averageGap = this.averageGap === undefined ? gap : (this.averageGap + gap) / 2;
+		const lines = Math.min(MAX_AUTO_LINES, Math.max(1, REFERENCE_GAP_MS / this.averageGap)) + this.carry;
+		const whole = Math.floor(lines);
+		this.carry = lines - whole;
+		return whole;
+	}
+
+	private reset(): void {
+		this.lastTime = Number.NEGATIVE_INFINITY;
+		this.lastDirection = 0;
+		this.averageGap = undefined;
+		this.carry = 0;
+	}
+}
diff --git a/packages/tui/test/tui-alt-screen.test.ts b/packages/tui/test/tui-alt-screen.test.ts
index e79169127..5c927535c 100644
--- a/packages/tui/test/tui-alt-screen.test.ts
+++ b/packages/tui/test/tui-alt-screen.test.ts
@@ -504,6 +504,31 @@ describe("TuiAltScreen", () => {
 		tui.stop();
 	});
 
+	// #9758: wheel line counts can change at runtime; Alt keeps its multiplier.
+	it("applies runtime wheel line count updates", async () => {
+		const terminal = new VirtualTerminal(20, 4);
+		const tui = new TuiAltScreen(terminal, undefined, undefined, { wheelScrollLines: 3 });
+		const deltas: Array<number | undefined> = [];
+		tui.addChild(
+			new MouseRegion(new Text("wheel target", 0, 0), (event) => {
+				if (event.type !== "wheel") return undefined;
+				deltas.push(event.wheelDelta);
+				return { handled: true };
+			}),
+		);
+		tui.start();
+		try {
+			await terminal.waitForRender();
+			terminal.sendInput("\x1b[<64;1;1M");
+			tui.setWheelScrollLines(2);
+			terminal.sendInput("\x1b[<65;1;1M");
+			terminal.sendInput("\x1b[<72;1;1M");
+			assert.deepStrictEqual(deltas, [-3, 2, -10]);
+		} finally {
+			tui.stop();
+		}
+	});
+
 	it("chains unused wheel delta to an outer scroll view", async () => {
 		const terminal = new VirtualTerminal(20, 4);
 		const tui = new TuiAltScreen(terminal, undefined, undefined, { wheelScrollLines: 3 });
diff --git a/packages/tui/test/wheel-scroll.test.ts b/packages/tui/test/wheel-scroll.test.ts
new file mode 100644
index 000000000..281893245
--- /dev/null
+++ b/packages/tui/test/wheel-scroll.test.ts
@@ -0,0 +1,47 @@
+import assert from "node:assert";
+import { describe, it } from "node:test";
+import { WheelScrollAccelerator } from "../src/wheel-scroll.ts";
+
+function scroll(accelerator: WheelScrollAccelerator, times: number[], direction: -1 | 1 = 1): number[] {
+	return times.map((time) => accelerator.next(direction, time));
+}
+
+// #9758: fullscreen wheel scrolling was one line per notch on terminals that do not accelerate wheels.
+describe("WheelScrollAccelerator", () => {
+	it("uses fixed line counts regardless of timing", () => {
+		const accelerator = new WheelScrollAccelerator(3, true);
+		assert.deepStrictEqual(scroll(accelerator, [0, 10, 20, 1000]), [3, 3, 3, 3]);
+		accelerator.setLines(0.5);
+		assert.strictEqual(accelerator.next(1, 2000), 1);
+	});
+
+	it("keeps one line per event in auto mode when the terminal already accelerates", () => {
+		const accelerator = new WheelScrollAccelerator("auto", false);
+		assert.deepStrictEqual(scroll(accelerator, [0, 10, 20, 30]), [1, 1, 1, 1]);
+	});
+
+	it("scales auto mode with wheel velocity", () => {
+		const accelerator = new WheelScrollAccelerator("auto", true);
+		assert.deepStrictEqual(scroll(accelerator, [0, 150, 300, 450]), [1, 1, 1, 1]);
+		assert.deepStrictEqual(scroll(accelerator, [1000, 1050, 1100, 1150]), [1, 2, 2, 2]);
+		assert.deepStrictEqual(scroll(accelerator, [2000, 2020, 2040, 2060]), [1, 5, 5, 5]);
+		assert.deepStrictEqual(scroll(accelerator, [3000, 3010, 3020, 3030]), [1, 6, 6, 6]);
+	});
+
+	it("does not accelerate bursts of events for a single notch", () => {
+		const accelerator = new WheelScrollAccelerator("auto", true);
+		assert.deepStrictEqual(scroll(accelerator, [0, 3, 6, 9]), [1, 1, 1, 1]);
+	});
+
+	it("resets acceleration on direction changes and pauses", () => {
+		const accelerator = new WheelScrollAccelerator("auto", true);
+		assert.deepStrictEqual(scroll(accelerator, [0, 20, 40]), [1, 5, 5]);
+		assert.strictEqual(accelerator.next(-1, 60), 1);
+		assert.deepStrictEqual(scroll(accelerator, [500, 520]), [1, 5]);
+	});
+
+	it("carries fractional lines between events", () => {
+		const accelerator = new WheelScrollAccelerator("auto", true);
+		assert.deepStrictEqual(scroll(accelerator, [0, 40, 80, 120, 160]), [1, 2, 3, 2, 3]);
+	});
+});