diff --git a/apps/web/src/hooks/timelineLivePreview.test.ts b/apps/web/src/hooks/timelineLivePreview.test.ts
new file mode 100644
index 0000000..35b32b1
--- /dev/null
+++ b/apps/web/src/hooks/timelineLivePreview.test.ts
@@ -0,0 +1,147 @@
+import { beforeEach, describe, expect, it, vi } from "vitest";
+import {
+  captureLivePreviewTargets,
+  clearLivePreview,
+  datesMatch,
+  joinTransforms,
+  preserveLivePreview,
+  scheduleLivePreview,
+  toPxValue,
+  type LivePreviewSession,
+} from "./timelineLivePreview.js";
+
+function createElement(style?: Partial<CSSStyleDeclaration>): HTMLElement {
+  return {
+    style: {
+      left: "",
+      width: "",
+      transform: "",
+      ...style,
+    },
+  } as HTMLElement;
+}
+
+function createSession(element: HTMLElement): LivePreviewSession {
+  return {
+    mode: "move",
+    cellWidth: 32,
+    targets: [
+      {
+        element,
+        baseLeft: 12,
+        baseWidth: 48,
+        baseTransform: "scale(1)",
+      },
+    ],
+    pointerDeltaX: 0,
+    daysDelta: 0,
+    frame: null,
+  };
+}
+
+describe("timelineLivePreview", () => {
+  beforeEach(() => {
+    vi.unstubAllGlobals();
+    vi.restoreAllMocks();
+  });
+
+  it("parses invalid pixel values as zero", () => {
+    expect(toPxValue("")).toBe(0);
+    expect(toPxValue("auto")).toBe(0);
+    expect(toPxValue("12.5px")).toBe(12.5);
+  });
+
+  it("joins transforms while ignoring empty and none entries", () => {
+    expect(joinTransforms(" translateX(2px) ", "", "none", undefined, "scale(1)")).toBe(
+      "translateX(2px) scale(1)",
+    );
+  });
+
+  it("deduplicates live preview targets while preserving base styles", () => {
+    const element = createElement({
+      left: "20px",
+      width: "64px",
+      transform: "translateX(4px)",
+    });
+
+    const targets = captureLivePreviewTargets([element, element]);
+
+    expect(targets).toHaveLength(1);
+    expect(targets[0]).toMatchObject({
+      baseLeft: 20,
+      baseWidth: 64,
+      baseTransform: "translateX(4px)",
+    });
+  });
+
+  it("cancels a pending frame and restores base preview styles when clearing", () => {
+    const element = createElement({
+      left: "40px",
+      width: "80px",
+      transform: "translateX(10px)",
+    });
+
+    const session = createSession(element);
+    const cancelAnimationFrameSpy = vi.fn();
+    vi.stubGlobal("cancelAnimationFrame", cancelAnimationFrameSpy);
+
+    session.frame = 23;
+    session.targets[0]!.element.style.left = "99px";
+    session.targets[0]!.element.style.width = "120px";
+    session.targets[0]!.element.style.transform = "translateX(99px)";
+
+    clearLivePreview(session);
+
+    expect(cancelAnimationFrameSpy).toHaveBeenCalledWith(23);
+    expect(session.frame).toBeNull();
+    expect(element.style.left).toBe("12px");
+    expect(element.style.width).toBe("48px");
+    expect(element.style.transform).toBe("scale(1)");
+  });
+
+  it("snapshots current styles and clears pending frames when preserving", () => {
+    const element = createElement({
+      left: "75px",
+      width: "112px",
+      transform: "translateX(6px)",
+    });
+
+    const session = createSession(element);
+    const cancelAnimationFrameSpy = vi.fn();
+    vi.stubGlobal("cancelAnimationFrame", cancelAnimationFrameSpy);
+
+    session.frame = 11;
+
+    preserveLivePreview(session);
+
+    expect(cancelAnimationFrameSpy).toHaveBeenCalledWith(11);
+    expect(session.frame).toBeNull();
+    expect(session.targets[0]).toMatchObject({
+      baseLeft: 75,
+      baseWidth: 112,
+      baseTransform: "translateX(6px)",
+    });
+  });
+
+  it("matches dates only when both timestamps are present and equal", () => {
+    const date = new Date("2025-05-10T00:00:00.000Z");
+
+    expect(datesMatch(date, new Date(date))).toBe(true);
+    expect(datesMatch(date, new Date("2025-05-11T00:00:00.000Z"))).toBe(false);
+    expect(datesMatch(date, null)).toBe(false);
+    expect(datesMatch(null, null)).toBe(false);
+  });
+
+  it("schedules at most one animation frame for a preview session", () => {
+    const element = createElement();
+    const session = createSession(element);
+    const requestAnimationFrameSpy = vi.fn(() => 7);
+    vi.stubGlobal("requestAnimationFrame", requestAnimationFrameSpy);
+
+    scheduleLivePreview(session);
+    scheduleLivePreview(session);
+
+    expect(requestAnimationFrameSpy).toHaveBeenCalledTimes(1);
+    expect(session.frame).toBe(7);
+  });
+});
diff --git a/apps/web/src/hooks/timelineLivePreview.ts b/apps/web/src/hooks/timelineLivePreview.ts
new file mode 100644
index 0000000..110fb37
--- /dev/null
+++ b/apps/web/src/hooks/timelineLivePreview.ts
@@ -0,0 +1,128 @@
+export type LivePreviewMode = "move" | "resize-start" | "resize-end";
+
+export type LivePreviewTarget = {
+  element: HTMLElement;
+  baseLeft: number;
+  baseWidth: number;
+  baseTransform: string;
+};
+
+export type LivePreviewSession = {
+  mode: LivePreviewMode;
+  cellWidth: number;
+  targets: LivePreviewTarget[];
+  pointerDeltaX: number;
+  daysDelta: number;
+  frame: number | null;
+};
+
+export function toPxValue(value: string): number {
+  const parsed = Number.parseFloat(value);
+  return Number.isFinite(parsed) ? parsed : 0;
+}
+
+export function joinTransforms(...parts: Array<string | undefined>): string {
+  return parts
+    .map((part) => part?.trim())
+    .filter((part): part is string => Boolean(part) && part !== "none")
+    .join(" ");
+}
+
+export function captureLivePreviewTargets(elements: Iterable<HTMLElement>): LivePreviewTarget[] {
+  const seen = new Set<HTMLElement>();
+  const targets: LivePreviewTarget[] = [];
+
+  for (const element of elements) {
+    if (seen.has(element)) continue;
+    seen.add(element);
+    targets.push({
+      element,
+      baseLeft: toPxValue(element.style.left),
+      baseWidth: toPxValue(element.style.width),
+      baseTransform: element.style.transform,
+    });
+  }
+
+  return targets;
+}
+
+function renderLivePreview(session: LivePreviewSession) {
+  const pointerOffsetX = session.pointerDeltaX - session.daysDelta * session.cellWidth;
+
+  for (const target of session.targets) {
+    let left = target.baseLeft;
+    let width = target.baseWidth;
+
+    if (session.mode === "move") {
+      left += session.daysDelta * session.cellWidth;
+    } else if (session.mode === "resize-start") {
+      left += session.daysDelta * session.cellWidth;
+      width = Math.max(session.cellWidth, width - session.daysDelta * session.cellWidth);
+    } else {
+      width = Math.max(session.cellWidth, width + session.daysDelta * session.cellWidth);
+    }
+
+    if (session.mode === "resize-start") {
+      const nextWidth = width - pointerOffsetX;
+      if (nextWidth < session.cellWidth) {
+        left += width - session.cellWidth;
+        width = session.cellWidth;
+      } else {
+        left += pointerOffsetX;
+        width = nextWidth;
+      }
+    } else if (session.mode === "resize-end") {
+      width = Math.max(session.cellWidth, width + pointerOffsetX);
+    }
+
+    target.element.style.left = `${left}px`;
+    target.element.style.width = `${Math.max(session.cellWidth, width)}px`;
+    target.element.style.transform = joinTransforms(
+      target.baseTransform,
+      session.mode === "move" && pointerOffsetX !== 0
+        ? `translateX(${pointerOffsetX}px)`
+        : undefined,
+    );
+  }
+}
+
+export function scheduleLivePreview(session: LivePreviewSession) {
+  if (session.frame !== null) return;
+  session.frame = requestAnimationFrame(() => {
+    session.frame = null;
+    renderLivePreview(session);
+  });
+}
+
+export function clearLivePreview(session: LivePreviewSession | null) {
+  if (!session) return;
+  if (session.frame !== null) {
+    cancelAnimationFrame(session.frame);
+    session.frame = null;
+  }
+
+  for (const target of session.targets) {
+    target.element.style.left = `${target.baseLeft}px`;
+    target.element.style.width = `${target.baseWidth}px`;
+    target.element.style.transform = target.baseTransform;
+  }
+}
+
+export function datesMatch(a: Date | null, b: Date | null) {
+  if (!a || !b) return false;
+  return a.getTime() === b.getTime();
+}
+
+export function preserveLivePreview(session: LivePreviewSession | null) {
+  if (!session) return;
+  if (session.frame !== null) {
+    cancelAnimationFrame(session.frame);
+    session.frame = null;
+  }
+
+  for (const target of session.targets) {
+    target.baseLeft = toPxValue(target.element.style.left);
+    target.baseWidth = toPxValue(target.element.style.width);
+    target.baseTransform = target.element.style.transform;
+  }
+}
diff --git a/apps/web/src/hooks/useTimelineDrag.ts b/apps/web/src/hooks/useTimelineDrag.ts
index 4c4cb00..73f239e 100644
--- a/apps/web/src/hooks/useTimelineDrag.ts
+++ b/apps/web/src/hooks/useTimelineDrag.ts
@@ -4,6 +4,14 @@ import { useCallback, useEffect, useRef, useState, type MutableRefObject } from
 import { trpc } from "~/lib/trpc/client.js";
 import { useInvalidateTimeline } from "./useInvalidatePlanningViews.js";
 import { pixelsToDays, computeDragDates } from "~/components/timeline/dragMath.js";
+import {
+  captureLivePreviewTargets,
+  clearLivePreview,
+  datesMatch,
+  preserveLivePreview,
+  scheduleLivePreview,
+  type LivePreviewSession,
+} from "./timelineLivePreview.js";
 
 const DRAG_CLICK_THRESHOLD_PX = 5;
 
@@ -104,133 +112,6 @@ const INITIAL_ALLOC_DRAG: AllocDragState = {
   daysDelta: 0,
 };
 
-type LivePreviewMode = AllocDragMode;
-
-type LivePreviewTarget = {
-  element: HTMLElement;
-  baseLeft: number;
-  baseWidth: number;
-  baseTransform: string;
-};
-
-type LivePreviewSession = {
-  mode: LivePreviewMode;
-  cellWidth: number;
-  targets: LivePreviewTarget[];
-  pointerDeltaX: number;
-  daysDelta: number;
-  frame: number | null;
-};
-
-function toPxValue(value: string): number {
-  const parsed = Number.parseFloat(value);
-  return Number.isFinite(parsed) ? parsed : 0;
-}
-
-function joinTransforms(...parts: Array<string | undefined>): string {
-  return parts
-    .map((part) => part?.trim())
-    .filter((part): part is string => Boolean(part) && part !== "none")
-    .join(" ");
-}
-
-function captureLivePreviewTargets(elements: Iterable<HTMLElement>): LivePreviewTarget[] {
-  const seen = new Set<HTMLElement>();
-  const targets: LivePreviewTarget[] = [];
-
-  for (const element of elements) {
-    if (seen.has(element)) continue;
-    seen.add(element);
-    targets.push({
-      element,
-      baseLeft: toPxValue(element.style.left),
-      baseWidth: toPxValue(element.style.width),
-      baseTransform: element.style.transform,
-    });
-  }
-
-  return targets;
-}
-
-function renderLivePreview(session: LivePreviewSession) {
-  const pointerOffsetX = session.pointerDeltaX - session.daysDelta * session.cellWidth;
-
-  for (const target of session.targets) {
-    let left = target.baseLeft;
-    let width = target.baseWidth;
-
-    if (session.mode === "move") {
-      left += session.daysDelta * session.cellWidth;
-    } else if (session.mode === "resize-start") {
-      left += session.daysDelta * session.cellWidth;
-      width = Math.max(session.cellWidth, width - session.daysDelta * session.cellWidth);
-    } else {
-      width = Math.max(session.cellWidth, width + session.daysDelta * session.cellWidth);
-    }
-
-    if (session.mode === "resize-start") {
-      const nextWidth = width - pointerOffsetX;
-      if (nextWidth < session.cellWidth) {
-        left += width - session.cellWidth;
-        width = session.cellWidth;
-      } else {
-        left += pointerOffsetX;
-        width = nextWidth;
-      }
-    } else if (session.mode === "resize-end") {
-      width = Math.max(session.cellWidth, width + pointerOffsetX);
-    }
-
-    target.element.style.left = `${left}px`;
-    target.element.style.width = `${Math.max(session.cellWidth, width)}px`;
-    target.element.style.transform = joinTransforms(
-      target.baseTransform,
-      session.mode === "move" && pointerOffsetX !== 0
-        ? `translateX(${pointerOffsetX}px)`
-        : undefined,
-    );
-  }
-}
-
-function scheduleLivePreview(session: LivePreviewSession) {
-  if (session.frame !== null) return;
-  session.frame = requestAnimationFrame(() => {
-    session.frame = null;
-    renderLivePreview(session);
-  });
-}
-
-function clearLivePreview(session: LivePreviewSession | null) {
-  if (!session) return;
-  if (session.frame !== null) {
-    cancelAnimationFrame(session.frame);
-  }
-
-  for (const target of session.targets) {
-    target.element.style.left = `${target.baseLeft}px`;
-    target.element.style.width = `${target.baseWidth}px`;
-    target.element.style.transform = target.baseTransform;
-  }
-}
-
-function datesMatch(a: Date | null, b: Date | null) {
-  return Boolean(a && b) && a!.getTime() === b!.getTime();
-}
-
-function preserveLivePreview(session: LivePreviewSession | null) {
-  if (!session) return;
-  if (session.frame !== null) {
-    cancelAnimationFrame(session.frame);
-    session.frame = null;
-  }
-
-  for (const target of session.targets) {
-    target.baseLeft = toPxValue(target.element.style.left);
-    target.baseWidth = toPxValue(target.element.style.width);
-    target.baseTransform = target.element.style.transform;
-  }
-}
-
 // ─── Range-select state ─────────────────────────────────────────────────────
 
 export interface RangeState {