feat(audio-player): scrub interaction rework — free-flow drag, pixel magnetism, touch pull-away precision (plan §9)

Mouse: drag is free-flow 1:1 (rail only on Shift+drag, now with
window from/to edge labels); clicks land with pixel magnetism
(MAGNET_RADIUS_PX=10) — the old 5-second threshold was sub-pixel on
long books and never fired, which was the 'chapter scrub isn't
accurate' bug. Hover inside the radius locks the tooltip to the line
with a highlight. Shift+click jumps to the nearest line from anywhere.

Touch: drag is an incremental cursor (applyDrag) whose scale tightens
continuously as the finger pulls off the bar (dragScale, exponential
10^(-|dy|/80px)) — the rail is the feedback: window shrinks with the
zoom (touchRailSpan) and lifts toward the finger (railLiftPx).

Dialog retitled 'Shortcuts & interactions' with a Mouse & touch
section driven by POINTER_GUIDE (audio-keys.ts). Old seconds-threshold
snapToChapter deleted. 133 unit tests; 19 Playwright checks on the
KJV (1189ch) and Gardens (34ch) books.

web/src/audio-keys.ts

@@ -213,6 +213,26 @@ export function visibleKeymap(): KeyActionSpec[] {
   return KEYMAP.filter((spec) => !spec.hidden);
 }
 
+// Pointer/wheel/touch interactions (plan §9) are not key events — the
+// dispatcher never sees them — but they belong in the same dialog so
+// every scrub gesture is discoverable in one place. templ x-fors this
+// table through the component's `pointerGuide` property (same binding
+// pattern as speeds/skipChoices).
+export interface PointerGuideRow {
+  // Badge label, e.g. "Shift + drag".
+  label: string;
+  description: string;
+}
+
+export const POINTER_GUIDE: readonly PointerGuideRow[] = [
+  { label: "Click", description: "Seek — lands on a chapter line within a pixel's reach" },
+  { label: "Drag", description: "Free scrub across the whole bar" },
+  { label: "Shift + click", description: "Jump to the nearest chapter line" },
+  { label: "Shift + drag", description: "Precision rail (±5 min) around the nearest line" },
+  { label: "Wheel", description: "Nudge ±5s (Shift: ±60s)" },
+  { label: "Touch + pull away", description: "Scrub, then drag off the bar for fine control" },
+];
+
 // resolveShortcut maps a keydown's (key, altKey) to an action, or null
 // when nothing claims it. Single characters match case-insensitively;
 // Alt-qualified bindings take precedence order for free: a plain key

web/src/audio-scrubber.test.ts

@@ -1,16 +1,25 @@
 import { describe, expect, it } from "vitest";
 
 import {
+  applyDrag,
   bufferedAheadEnd,
   bufferedSpanPct,
   chapterIndexFor,
   denseTicks,
+  dragScale,
+  DRAG_REF_PX,
+  DRAG_SCALE_MIN,
+  nearestChapterLine,
+  railLiftPx,
   railSecondsAtPointer,
   railTicks,
   railWindow,
   RAIL_SPAN,
   secondsAtPointer,
-  snapToChapter,
+  snapToChapterPx,
+  TOUCH_RAIL_LIFT_MAX_PX,
+  TOUCH_RAIL_MIN_DY_PX,
+  touchRailSpan,
 } from "./audio-scrubber";
 
 // An 86-hour book (KJV-shaped: 1189 even chapters) and a 26-hour
@@ -66,28 +75,142 @@ describe("chapterIndexFor", () => {
   });
 });
 
-describe("snapToChapter", () => {
-  it("snaps within the threshold and not beyond it", () => {
-    const start = chapters1189[10].start;
-    expect(snapToChapter(start + 3, chapters1189, 5)).toEqual({ seconds: start, snapped: true });
-    expect(snapToChapter(start + 4.9, chapters1189, 5)).toEqual({ seconds: start, snapped: true });
-    expect(snapToChapter(start + 5.1, chapters1189, 5).snapped).toBe(false);
-    expect(snapToChapter(start - 5, chapters1189, 5)).toEqual({ seconds: start, snapped: true });
+describe("nearestChapterLine / snapToChapterPx (§9 pixel magnetism)", () => {
+  // 34-chapter book on an 800px bar: ~23.5px between lines — the
+  // radius discriminates. (On the KJV-shaped bar the 1189 lines sit
+  // ~0.4px apart — magnetism lands on SOME line from anywhere, which
+  // is correct for a book that dense.)
+  const pxSec = 800 / duration26h; // bar px per second
+
+  it("reports the closest line and its distance in bar pixels", () => {
+    const start = chapters34[5].start;
+    const near = nearestChapterLine(start + 5 / pxSec, chapters34, duration26h, 800);
+    expect(near!.index).toBe(5);
+    expect(near!.seconds).toBe(start);
+    expect(near!.distancePx).toBeCloseTo(5, 5);
+    expect(nearestChapterLine(42, [], duration26h, 800)).toBeNull();
   });
 
-  it("picks the NEAREST line when two are in range", () => {
+  it("finds sub-pixel lines on a book as dense as the KJV", () => {
+    // 1px ≈ 633s — a seconds threshold could never fire here; a pixel
+    // radius always can. This is the §9 root-cause fix.
+    const dense = nearestChapterLine(duration86h / 2, chapters1189, duration86h, 489);
+    expect(dense).not.toBeNull();
+    expect(dense!.distancePx).toBeLessThan(0.25);
+  });
+
+  it("snaps within the pixel radius and not beyond it", () => {
+    const start = chapters34[5].start;
+    expect(snapToChapterPx(start + 9 / pxSec, chapters34, duration26h, 800)).toEqual({
+      seconds: start,
+      snapped: true,
+    });
+    expect(snapToChapterPx(start + 11 / pxSec, chapters34, duration26h, 800).snapped).toBe(false);
+    expect(snapToChapterPx(start - 10 / pxSec, chapters34, duration26h, 800)).toEqual({
+      seconds: start,
+      snapped: true,
+    });
+  });
+
+  it("force snaps to the nearest line regardless of radius (Shift+click)", () => {
     const a = chapters34[5].start;
     const b = chapters34[6].start;
     const mid = (a + b) / 2;
-    // Chapter gap (~2759s) means both lines sit ~1380s from the
-    // midpoint — the threshold must reach past it.
-    const result = snapToChapter(mid + 1, chapters34, 1500);
+    // Radius 0 + force must land where a wide radius lands: distance
+    // is ignored, nearest wins (mid+1 → the later line).
+    expect(snapToChapterPx(mid + 1, chapters34, duration26h, 800, 0, true)).toEqual({
+      seconds: b,
+      snapped: true,
+    });
+    // Past the book's last line, the nearest line is still reachable.
+    const last = chapters34[33].start;
+    expect(snapToChapterPx(last + 1000 / pxSec, chapters34, duration26h, 800, 0, true)).toEqual({
+      seconds: last,
+      snapped: true,
+    });
+  });
+
+  it("picks the NEAREST line when two are in radius", () => {
+    const a = chapters34[5].start;
+    const b = chapters34[6].start;
+    const mid = (a + b) / 2;
+    // Both lines sit ~11.8px from the midpoint; inside a 13px radius
+    // the closer (later) one must win.
+    const result = snapToChapterPx(mid + 1, chapters34, duration26h, 800, 13);
     expect(result.snapped).toBe(true);
     expect(result.seconds).toBe(b);
   });
 
-  it("leaves the position alone with no chapters", () => {
-    expect(snapToChapter(42, [], 5)).toEqual({ seconds: 42, snapped: false });
+  it("leaves the position alone with no chapters or a dead bar", () => {
+    expect(snapToChapterPx(42, [], duration26h, 800)).toEqual({ seconds: 42, snapped: false });
+    expect(snapToChapterPx(42, chapters34, duration26h, 0).snapped).toBe(false);
+  });
+});
+
+describe("dragScale / applyDrag (§9 touch progressive precision)", () => {
+  it("is 1:1 at the bar and decays an order per reference distance", () => {
+    expect(dragScale(0)).toBe(1);
+    expect(dragScale(DRAG_REF_PX)).toBeCloseTo(0.1, 5);
+    expect(dragScale(2 * DRAG_REF_PX)).toBeCloseTo(0.01, 5);
+  });
+
+  it("is symmetric in pull direction and monotonic in |dy|", () => {
+    expect(dragScale(-60)).toBe(dragScale(60));
+    expect(dragScale(30)).toBeGreaterThan(dragScale(60));
+    expect(dragScale(60)).toBeGreaterThan(dragScale(120));
+    expect(dragScale(10_000)).toBe(DRAG_SCALE_MIN);
+  });
+
+  it("degenerates to plain travel with a dead reference", () => {
+    expect(dragScale(500, 0)).toBe(1);
+  });
+
+  it("advances the cursor 1:1 at dy=0 (px → seconds at bar scale)", () => {
+    // 800px bar over 26h: 100px ≈ 11726s.
+    expect(applyDrag(0, 100, 0, 800 / duration26h, duration26h)).toBeCloseTo(
+      (100 / 800) * duration26h,
+      5,
+    );
+  });
+
+  it("shrinks travel by the current zoom (incremental, not absolute)", () => {
+    const pxPerSecond = 800 / duration26h;
+    const onePxSeconds = 1 / pxPerSecond;
+    // One reference-distance of pull = one order of magnitude finer.
+    expect(applyDrag(0, 100, DRAG_REF_PX, pxPerSecond, duration26h)).toBeCloseTo(
+      100 * onePxSeconds * 0.1,
+      5,
+    );
+    // Scale changes only affect SUBSEQUENT travel: the cursor never
+    // teleports when the finger pulls away mid-drag.
+    expect(applyDrag(5000, 0, 3 * DRAG_REF_PX, pxPerSecond, duration26h)).toBe(5000);
+  });
+
+  it("clamps to the book in both directions", () => {
+    const pxPerSecond = 800 / duration26h;
+    expect(applyDrag(duration26h, 100, 0, pxPerSecond, duration26h)).toBe(duration26h);
+    expect(applyDrag(1, -100, 0, pxPerSecond, duration26h)).toBe(0);
+    expect(applyDrag(50, 100, 0, 0, duration26h)).toBe(50);
+  });
+});
+
+describe("touch rail feedback (span shrink + lift)", () => {
+  it("starts at the full ±5-min span and shrinks with the zoom", () => {
+    expect(touchRailSpan(0)).toBe(RAIL_SPAN);
+    expect(touchRailSpan(DRAG_REF_PX)).toBeCloseTo(RAIL_SPAN * 0.1, 5);
+    expect(touchRailSpan(5 * DRAG_REF_PX)).toBe(2); // zoomed past the floor
+    expect(touchRailSpan(60)).toBeLessThan(RAIL_SPAN);
+  });
+
+  it("shows the rail only past the pull threshold", () => {
+    expect(TOUCH_RAIL_MIN_DY_PX).toBeGreaterThan(0);
+  });
+
+  it("lifts toward the finger, capped", () => {
+    expect(railLiftPx(20)).toBe(-20); // finger above the bar → rail rises
+    expect(railLiftPx(-30)).toBe(30); // finger below → rail follows down
+    expect(railLiftPx(500)).toBe(-TOUCH_RAIL_LIFT_MAX_PX);
+    expect(railLiftPx(-500)).toBe(TOUCH_RAIL_LIFT_MAX_PX);
   });
 });
 

web/src/audio-scrubber.ts

@@ -1,9 +1,9 @@
-// Scrubber math (player plan §1 — progress bar overhaul). Pure and
-// DOM-free except for passing rects in; the Alpine component owns the
-// element, the pointer events and the state. Everything here is
-// unit-tested — the snap threshold, the buffer→global mapping and the
-// precision-rail mapping are exactly the parts that must hold for an
-// 86-hour, 1189-track book AND a 2-hour single-file m4b.
+// Scrubber math (player plans §1 + §9). Pure and DOM-free except for
+// passing rects in; the Alpine component owns the element, the pointer
+// events and the state. Everything here is unit-tested — the pixel
+// magnetism, the pull-away drag scaling and the precision-rail mapping
+// are exactly the parts that must hold for an 86-hour, 1189-track book
+// AND a 26-hour single-file m4b.
 
 export interface ScrubChapter {
   start: number;
@@ -29,26 +29,102 @@ export function chapterIndexFor(chapters: ScrubChapter[], seconds: number): numb
   return found;
 }
 
-// snapToChapter returns the chapter start when the position falls
-// within thresholdSeconds of one (click-to-snap), otherwise the
-// position unchanged.
-export function snapToChapter(
+// ---- §9 magnetism: pixel radius, not a seconds threshold ----
+// A seconds threshold goes sub-pixel on long books (1px ≈ 633s on the
+// KJV bar — 5s could never fire); magnetism must be measured in PIXELS.
+
+// MAGNET_RADIUS_PX is how close a click/hover must be to a chapter line,
+// in bar pixels, for it to take over the landing position.
+export const MAGNET_RADIUS_PX = 10;
+
+// nearestChapterLine finds the chapter start closest to a position and
+// reports its distance in bar pixels. Empty chapters → null.
+export function nearestChapterLine(
   seconds: number,
   chapters: ScrubChapter[],
-  thresholdSeconds = 5,
-): { seconds: number; snapped: boolean } {
-  let best: { seconds: number; snapped: boolean } = { seconds, snapped: false };
-  let bestDistance = thresholdSeconds;
-  for (const ch of chapters) {
-    const distance = Math.abs(ch.start - seconds);
-    if (distance <= bestDistance) {
-      bestDistance = distance;
-      best = { seconds: ch.start, snapped: true };
-    }
+  duration: number,
+  widthPx: number,
+): { index: number; seconds: number; distancePx: number } | null {
+  if (chapters.length === 0 || duration <= 0 || widthPx <= 0) return null;
+  const pxPerSecond = widthPx / duration;
+  let best: { index: number; seconds: number; distancePx: number } | null = null;
+  for (let i = 0; i < chapters.length; i += 1) {
+    const distancePx = Math.abs(chapters[i].start - seconds) * pxPerSecond;
+    if (best === null || distancePx < best.distancePx)
+      best = { index: i, seconds: chapters[i].start, distancePx };
   }
   return best;
 }
 
+// snapToChapterPx applies the magnet: within radiusPx of a line the
+// position lands ON the line; force (Shift+click) extends the pull to
+// the nearest line regardless of distance. Otherwise unchanged.
+export function snapToChapterPx(
+  seconds: number,
+  chapters: ScrubChapter[],
+  duration: number,
+  widthPx: number,
+  radiusPx = MAGNET_RADIUS_PX,
+  force = false,
+): { seconds: number; snapped: boolean } {
+  const near = nearestChapterLine(seconds, chapters, duration, widthPx);
+  if (near === null) return { seconds, snapped: false };
+  if (force || near.distancePx <= radiusPx) return { seconds: near.seconds, snapped: true };
+  return { seconds, snapped: false };
+}
+
+// ---- §9 touch precision: vertical pull-away = progressive zoom ----
+
+// The scale factor decays an order of magnitude for every DRAG_REF_PX of
+// vertical distance from the bar: 1:1 at the bar, ~0.1× one screen-gap
+// away, ~0.01× further. Exponential keeps the zoom continuous — any
+// precision level is one gesture (plan §9 option C).
+export const DRAG_REF_PX = 80;
+export const DRAG_SCALE_MIN = 0.001;
+
+export function dragScale(dyPx: number, refPx: number = DRAG_REF_PX): number {
+  if (refPx <= 0) return 1;
+  return Math.max(DRAG_SCALE_MIN, Math.pow(10, -Math.abs(dyPx) / refPx));
+}
+
+// applyDrag advances an INCREMENTAL drag cursor by one pointermove:
+// horizontal travel (px) converts at the bar's scale, then shrinks by
+// the current vertical offset. Incremental, not absolute — changing the
+// scale mid-drag only affects subsequent travel, so pulling away never
+// teleports the position. Clamped to the book.
+export function applyDrag(
+  position: number,
+  dxPx: number,
+  dyPx: number,
+  pxPerSecond: number,
+  duration: number,
+  refPx: number = DRAG_REF_PX,
+): number {
+  const clamped = Math.min(duration, Math.max(0, position));
+  if (pxPerSecond <= 0 || duration <= 0) return clamped;
+  return Math.min(duration, Math.max(0, clamped + (dxPx / pxPerSecond) * dragScale(dyPx, refPx)));
+}
+
+// Touch feedback thresholds: the rail appears once the finger is at
+// least TOUCH_RAIL_MIN_DY_PX off the bar, and lifts toward the finger up
+// to TOUCH_RAIL_LIFT_MAX_PX while the window shrinks with the zoom.
+export const TOUCH_RAIL_MIN_DY_PX = 12;
+export const TOUCH_RAIL_LIFT_MAX_PX = 40;
+
+// touchRailSpan shrinks the rail window with the zoom (full ±5-min rail
+// at 1:1, an order tighter per DRAG_REF_PX of pull) with a floor that
+// keeps the edge labels readable.
+export function touchRailSpan(dyPx: number, refPx: number = DRAG_REF_PX): number {
+  return Math.max(2, Math.min(RAIL_SPAN, RAIL_SPAN * dragScale(dyPx, refPx)));
+}
+
+// railLiftPx converts the vertical offset into the rail's translateY:
+// toward the finger (negative = up), capped so the rail never chases
+// the finger off the player.
+export function railLiftPx(dyPx: number): number {
+  return -Math.max(-TOUCH_RAIL_LIFT_MAX_PX, Math.min(TOUCH_RAIL_LIFT_MAX_PX, dyPx));
+}
+
 // denseTicks decides which chapter starts get a rendered tick: a
 // chapter earns a mark only when it is at least minGapPx from the last
 // kept one — an 1189-chapter book would otherwise paint the bar solid.

web/src/audio.ts

@@ -15,7 +15,7 @@
 import { Alpine } from "./alpine";
 import { renderNoteHtml } from "./markdown";
 import { showToast } from "./toast";
-import { resolveShortcut, visibleKeymap, type KeyAction } from "./audio-keys";
+import { POINTER_GUIDE, resolveShortcut, visibleKeymap, type KeyAction } from "./audio-keys";
 import {
   SLEEP_CHOICES,
   SLEEP_OFF,
@@ -29,15 +29,21 @@ import {
   type SleepState,
 } from "./audio-sleep";
 import {
+  applyDrag,
   bufferedAheadEnd,
   bufferedSpanPct,
   chapterIndexFor,
   denseTicks,
+  MAGNET_RADIUS_PX,
+  nearestChapterLine,
+  railLiftPx,
   railSecondsAtPointer,
   railTicks,
   railWindow,
   secondsAtPointer,
-  snapToChapter,
+  snapToChapterPx,
+  TOUCH_RAIL_MIN_DY_PX,
+  touchRailSpan,
 } from "./audio-scrubber";
 
 type AudioChapter = { index: number; title: string; start: number; end: number };
@@ -155,6 +161,8 @@ Alpine.data("audioReader", () => ({
   // Exposed for the templ dropdown's x-for — templ cannot import the
   // const directly; this property is the binding.
   speeds: SPEEDS,
+  // Same binding pattern, for the dialog's Mouse & touch section.
+  pointerGuide: POINTER_GUIDE,
   skipSeconds: Number(localStorage.getItem("audio_skip") || 10),
   // Scrub guard: while dragging, timeupdate must not fight the handle
   scrubbing: false,
@@ -167,9 +175,19 @@ Alpine.data("audioReader", () => ({
   bufferedGlobal: null as number | null,
   hoverSeconds: null as number | null,
   hoverPct: 0,
+  // §9: hover locks to a chapter line inside the magnet radius (the
+  // highlight line + tooltip land where the click will).
+  hoverSnapped: false,
   railFrom: 0,
   railTo: 0,
   railTickList: [] as Array<{ start: number; title: string }>,
+  // §9 interaction model: "free" = 1:1 mouse drag (no rail), "rail" =
+  // Shift+drag precision window, "touch" = incremental cursor with
+  // pull-away precision. The rail is only visible for the last two.
+  dragMode: null as null | "free" | "rail" | "touch",
+  railVisible: false,
+  railLiftY: 0,
+  touchLastX: 0,
 
   // Track manifest: one AudioTrack per playable file. Single-file books
   // (m4b/mp3) carry exactly one track whose URL is the whole file, so
@@ -702,13 +720,16 @@ Alpine.data("audioReader", () => ({
     return Math.min(100, Math.max(0, ((this.scrubValue - this.railFrom) / span) * 100));
   },
 
-  // Click/drag on the bar: the FIRST press maps hours-per-pixel and
-  // snaps to a chapter line within ~5s; while held, the precision rail
-  // takes over at minutes-per-pixel (re-grab to travel far). The
-  // native range stays underneath for keyboard/aria — its drag default
-  // is prevented so the two mappings never fight.
+  // Pointer interactions (plan §9): mouse drag is FREE FLOW (1:1, no
+  // rail, never sticks at chapter lines); clicks land with pixel
+  // magnetism on nearby chapter lines; Shift+click/drag opens the
+  // precision rail (±5 min, free mapping inside); touch drags are an
+  // incremental cursor whose scale tightens as the finger pulls off the
+  // bar (progressive precision — the rail is its feedback). The native
+  // range stays underneath for keyboard/aria — its drag default is
+  // prevented so the mappings never fight.
   scrubPointerDown(e: PointerEvent) {
-    if (e.button !== 0) return;
+    if (e.button !== 0 || this.scrubbing) return;
     e.preventDefault();
     const area = e.currentTarget as HTMLElement;
     const rect = area.getBoundingClientRect();
@@ -720,13 +741,32 @@ Alpine.data("audioReader", () => ({
     }
     document.getElementById("audio-scrub")?.focus({ preventScroll: true });
     const duration = this.chaptersDuration() || 1;
-    const at = snapToChapter(secondsAtPointer(e.clientX, rect, duration), this.chapters, 5).seconds;
+    const at = secondsAtPointer(e.clientX, rect, duration);
+    if (e.pointerType === "touch") {
+      // Tap lands magnetically; the drag starts 1:1 and tightens as
+      // the finger pulls away (scrubPointerMove's incremental cursor).
+      this.dragMode = "touch";
+      this.touchLastX = e.clientX;
+      this.scrubValue = snapToChapterPx(at, this.chapters, duration, rect.width).seconds;
+    } else if (e.shiftKey) {
+      // Shift+click/drag: the precision rail, anchored to the NEAREST
+      // chapter line (Shift+click = snap regardless of radius).
+      this.dragMode = "rail";
+      const near = nearestChapterLine(at, this.chapters, duration, rect.width);
+      this.scrubValue = near ? near.seconds : at;
+      const window = railWindow(this.scrubValue, duration);
+      this.railFrom = window.from;
+      this.railTo = window.to;
+      this.railTickList = railTicks(window, this.chapters);
+      this.railVisible = true;
+      this.railLiftY = 0;
+    } else {
+      // Mouse click/drag: the CLICK's landing is magnetic; drags stay
+      // free-flow (scrubPointerMove overwrites with the raw position).
+      this.dragMode = "free";
+      this.scrubValue = snapToChapterPx(at, this.chapters, duration, rect.width).seconds;
+    }
     this.scrubbing = true;
-    this.scrubValue = at;
-    const window = railWindow(at, duration);
-    this.railFrom = window.from;
-    this.railTo = window.to;
-    this.railTickList = railTicks(window, this.chapters);
   },
 
   scrubPointerMove(e: PointerEvent) {
@@ -734,21 +774,54 @@ Alpine.data("audioReader", () => ({
     const rect = area.getBoundingClientRect();
     const duration = this.chaptersDuration() || 1;
     if (!this.scrubbing) {
-      this.hoverSeconds = secondsAtPointer(e.clientX, rect, duration);
-      this.hoverPct =
-        rect.width > 0
-          ? Math.min(100, Math.max(0, ((e.clientX - rect.left) / rect.width) * 100))
-          : 0;
+      // Hover: time + chapter, locking to a chapter line inside the
+      // magnet radius so the tooltip shows the click's true landing.
+      const at = secondsAtPointer(e.clientX, rect, duration);
+      const near = nearestChapterLine(at, this.chapters, duration, rect.width);
+      const locked = near !== null && near.distancePx <= MAGNET_RADIUS_PX;
+      const hoverAt = locked && near ? near.seconds : at;
+      this.hoverSeconds = hoverAt;
+      this.hoverPct = rect.width > 0 ? Math.min(100, Math.max(0, (hoverAt / duration) * 100)) : 0;
+      this.hoverSnapped = locked;
       return;
     }
-    this.scrubValue = railSecondsAtPointer(e.clientX, rect, {
-      from: this.railFrom,
-      to: this.railTo,
-    });
+    if (this.dragMode === "rail") {
+      this.scrubValue = railSecondsAtPointer(e.clientX, rect, {
+        from: this.railFrom,
+        to: this.railTo,
+      });
+      return;
+    }
+    if (this.dragMode === "touch") {
+      const dx = e.clientX - this.touchLastX;
+      this.touchLastX = e.clientX;
+      const dy = rect.top + rect.height / 2 - e.clientY;
+      this.scrubValue = applyDrag(this.scrubValue, dx, dy, rect.width / duration, duration);
+      if (Math.abs(dy) >= TOUCH_RAIL_MIN_DY_PX) {
+        // Feedback: the rail follows the cursor, its window shrinking
+        // with the zoom, lifting toward the finger.
+        const window = railWindow(this.scrubValue, duration, touchRailSpan(dy));
+        this.railFrom = window.from;
+        this.railTo = window.to;
+        this.railTickList = railTicks(window, this.chapters);
+        this.railVisible = true;
+        this.railLiftY = railLiftPx(dy);
+      } else {
+        this.railVisible = false;
+        this.railLiftY = 0;
+      }
+      return;
+    }
+    // Free flow: direct 1:1 mapping — dragging across chapter lines
+    // never sticks.
+    this.scrubValue = secondsAtPointer(e.clientX, rect, duration);
   },
 
   scrubPointerLeave() {
-    if (!this.scrubbing) this.hoverSeconds = null;
+    if (!this.scrubbing) {
+      this.hoverSeconds = null;
+      this.hoverSnapped = false;
+    }
   },
 
   scrubPointerUp(e: PointerEvent) {
@@ -758,7 +831,11 @@ Alpine.data("audioReader", () => ({
       area.releasePointerCapture(e.pointerId);
     this.seekTo(this.scrubValue);
     this.scrubbing = false;
+    this.dragMode = null;
+    this.railVisible = false;
+    this.railLiftY = 0;
     this.hoverSeconds = null;
+    this.hoverSnapped = false;
   },
 
   // Wheel over the bar: ±5s nudge, Shift = ±60s. Scroll up = forward.