diff --git a/README.md b/README.md
index 99537a9..cab3f6d 100644
--- a/README.md
+++ b/README.md
@@ -228,7 +228,7 @@ Generated from `dist/index.d.ts` after the package build.
 | Export | Kind | Source | JSDoc summary |
 |---|---|---|---|
 | `AcceleratedDataset` | interface | `./core/types` | Convenience contract for maximum-performance custom datasets. Implement this when a dataset can provide fast exact sample copies, stable viewport sampling, range min/max queries, and renderer-ready min/max buckets. |
-| `AppendableDataset` | interface | `./core/types` | Dataset that accepts appended explicit X/Y samples. |
+| `AppendableDataset` | interface | `./core/types` | Dataset that accepts appended X/Y samples; implementations may store X values explicitly or use them to seed implicit X spacing. |
 | `AttributeSpec` | interface | `./render/types` | Vertex attribute binding for a draw call. |
 | `AxisConfig` | interface | `./ui/Chart` | Axis visibility, placement, scale, tick formatting, and title options. |
 | `AxisController` | class | `./interaction/AxisController` | Computes axis tick values and labels for a camera. |
@@ -317,7 +317,7 @@ Generated from `dist/index.d.ts` after the package build.
 | `PrecomputedHistogramSeriesConfig` | interface | `./ui/Chart` | Series configuration for `Chart.addHistogram(...)` from precomputed bins. |
 | `RangeMinMaxDataset` | interface | `./core/types` | Dataset that can answer min/max Y queries for index ranges. |
 | `RangeSampleCopyDataset` | interface | `./core/types` | Optional high-performance extraction capability for datasets that can copy raw samples without going through repeated getX/getY calls. Implement this for very large datasets, implicit-X datasets, or remote/memory-mapped sources. |
-| `ReglBackend` | const | `./render/WebGL2Backend` | Deprecated alias for WebGL2Backend. This preserves the pre-native-backend public API. Deprecated: Effective next patch release. Use WebGL2Backend. |
+| `ReglBackend` | const | `./render/WebGL2Backend` | Deprecated alias for WebGL2Backend. This preserves the pre-native-backend public API. Deprecated: Use WebGL2Backend; removal target: 0.4.0. |
 | `ResolvedChartTheme` | interface | `./ui/theme` | Fully resolved chart theme with concrete RGBA values. |
 | `RgbaColor` | type | `./ui/theme` | RGBA color tuple with 0-1 channel values. |
 | `RingBuffer` | class | `./core/RingBuffer` | Fixed-capacity sorted XY buffer for explicit X values. |
diff --git a/docs/api-reference.md b/docs/api-reference.md
index ada5fea..5cce639 100644
--- a/docs/api-reference.md
+++ b/docs/api-reference.md
@@ -85,7 +85,7 @@ Generated from `dist/index.d.ts` after the package build.
 | Export | Kind | Source | JSDoc summary |
 |---|---|---|---|
 | `AcceleratedDataset` | interface | `./core/types` | Convenience contract for maximum-performance custom datasets. Implement this when a dataset can provide fast exact sample copies, stable viewport sampling, range min/max queries, and renderer-ready min/max buckets. |
-| `AppendableDataset` | interface | `./core/types` | Dataset that accepts appended explicit X/Y samples. |
+| `AppendableDataset` | interface | `./core/types` | Dataset that accepts appended X/Y samples; implementations may store X values explicitly or use them to seed implicit X spacing. |
 | `AttributeSpec` | interface | `./render/types` | Vertex attribute binding for a draw call. |
 | `AxisConfig` | interface | `./ui/Chart` | Axis visibility, placement, scale, tick formatting, and title options. |
 | `AxisController` | class | `./interaction/AxisController` | Computes axis tick values and labels for a camera. |
@@ -174,7 +174,7 @@ Generated from `dist/index.d.ts` after the package build.
 | `PrecomputedHistogramSeriesConfig` | interface | `./ui/Chart` | Series configuration for `Chart.addHistogram(...)` from precomputed bins. |
 | `RangeMinMaxDataset` | interface | `./core/types` | Dataset that can answer min/max Y queries for index ranges. |
 | `RangeSampleCopyDataset` | interface | `./core/types` | Optional high-performance extraction capability for datasets that can copy raw samples without going through repeated getX/getY calls. Implement this for very large datasets, implicit-X datasets, or remote/memory-mapped sources. |
-| `ReglBackend` | const | `./render/WebGL2Backend` | Deprecated alias for WebGL2Backend. This preserves the pre-native-backend public API. Deprecated: Effective next patch release. Use WebGL2Backend. |
+| `ReglBackend` | const | `./render/WebGL2Backend` | Deprecated alias for WebGL2Backend. This preserves the pre-native-backend public API. Deprecated: Use WebGL2Backend; removal target: 0.4.0. |
 | `ResolvedChartTheme` | interface | `./ui/theme` | Fully resolved chart theme with concrete RGBA values. |
 | `RgbaColor` | type | `./ui/theme` | RGBA color tuple with 0-1 channel values. |
 | `RingBuffer` | class | `./core/RingBuffer` | Fixed-capacity sorted XY buffer for explicit X values. |
diff --git a/src/core/SeriesStore.ts b/src/core/SeriesStore.ts
index a666409..a58d7f4 100644
--- a/src/core/SeriesStore.ts
+++ b/src/core/SeriesStore.ts
@@ -243,7 +243,7 @@ export class SeriesStore {
   /** Append XY, implicit-X, OHLC, or row-array data and request an on-demand render. */
   append(data: SeriesAppendData): void;
   /**
-   * @deprecated Effective next patch release. Use `append({ x, y })` instead.
+   * @deprecated Use `append({ x, y })` instead; removal target: 0.4.0.
    */
   append(x: ArrayLike<number>, y: ArrayLike<number>): void;
   /** Append data in the supported object, row, or legacy array forms. */
@@ -326,7 +326,7 @@ export class SeriesStore {
   }
 
   /**
-   * @deprecated Effective next patch release. Use `append({ y })` instead.
+   * @deprecated Use `append({ y })` instead; removal target: 0.4.0.
    */
   appendY(y: ArrayLike<number>): void {
     this.appendYArray(y);
@@ -342,7 +342,7 @@ export class SeriesStore {
   }
 
   /**
-   * @deprecated Effective next patch release. Use `append({ x, open, high, low, close })` instead.
+   * @deprecated Use `append({ x, open, high, low, close })` instead; removal target: 0.4.0.
    */
   appendOhlc(
     x: ArrayLike<number>,
@@ -421,7 +421,7 @@ export class SeriesStore {
   }
 
   /**
-   * @deprecated Effective next patch release. Use `updateLast({ open, high, low, close })` instead.
+   * @deprecated Use `updateLast({ open, high, low, close })` instead; removal target: 0.4.0.
    */
   updateLastOhlc(open: number, high: number, low: number, close: number): boolean {
     return this.updateOhlcAt(this.dataset.length - 1, open, high, low, close);
diff --git a/src/core/types.ts b/src/core/types.ts
index f9384b3..b25f8c2 100644
--- a/src/core/types.ts
+++ b/src/core/types.ts
@@ -170,7 +170,7 @@ export interface OhlcDataset extends Dataset {
   getClose(index: number): number;
 }
 
-/** Dataset that accepts appended explicit X/Y samples. */
+/** Dataset that accepts appended X/Y samples; implementations may store X values explicitly or use them to seed implicit X spacing. */
 export interface AppendableDataset extends Dataset {
   push(x: number, y: number): void;
   append(x: ArrayLike<number>, y: ArrayLike<number>): void;
diff --git a/src/data.ts b/src/data.ts
index fdbae57..9a7fb8b 100644
--- a/src/data.ts
+++ b/src/data.ts
@@ -152,7 +152,7 @@ export function exportSelectedChartData(
   }, options);
 }
 
-/** Collect all raw samples from chart series, optionally constrained by options.series and visibleOnly. */
+/** Collect raw samples from visible chart series by default; pass visibleOnly: false to include hidden series. */
 export function exportAllChartData(chart: Chart, options: ChartDataExportOptions = {}): ChartDataExport {
   return collectChartData(chart, { source: "all", bounds: null }, options);
 }
diff --git a/src/react.ts b/src/react.ts
index 73a220b..8e1dedd 100644
--- a/src/react.ts
+++ b/src/react.ts
@@ -4,6 +4,7 @@ import type { ChartOptions } from "./ui/Chart.js";
 
 /** Props for the React chart host component. */
 export interface BlazeChartProps {
+  /** Chart options used at construction time. Changing object identity disposes and recreates the chart; keep stable with useMemo. */
   readonly options?: ChartOptions;
   readonly className?: string;
   readonly style?: React.CSSProperties;
diff --git a/src/render/WebGL2Backend.ts b/src/render/WebGL2Backend.ts
index e2a1d27..000bfd3 100644
--- a/src/render/WebGL2Backend.ts
+++ b/src/render/WebGL2Backend.ts
@@ -445,6 +445,6 @@ export class WebGL2Backend implements GpuBackend {
 
 /**
  * Deprecated alias for WebGL2Backend. This preserves the pre-native-backend public API.
- * @deprecated Effective next patch release. Use WebGL2Backend.
+ * @deprecated Use WebGL2Backend; removal target: 0.4.0.
  */
 export const ReglBackend: typeof WebGL2Backend = WebGL2Backend;
diff --git a/src/ui/Annotations.ts b/src/ui/Annotations.ts
index 956d5dc..9070767 100644
--- a/src/ui/Annotations.ts
+++ b/src/ui/Annotations.ts
@@ -156,7 +156,7 @@ export interface AnnotationsPlugin extends ChartPlugin {
 
 const SVG_NS = "http://www.w3.org/2000/svg";
 
-function svg<K extends keyof SVGElementTagNameMap>(tag: K): SVGElementTagNameMap[K] {
+function createSvgElement<K extends keyof SVGElementTagNameMap>(tag: K): SVGElementTagNameMap[K] {
   return document.createElementNS(SVG_NS, tag);
 }
 
@@ -316,7 +316,7 @@ export function annotationsPlugin(options: AnnotationsPluginOptions = {}): Annot
   return {
     install(chart: ChartPluginContext) {
       chartRef = chart;
-      overlay = svg("svg");
+      overlay = createSvgElement("svg");
       overlay.classList.add(options.className ?? "blazeplot-annotations");
       overlay.style.position = "absolute";
       overlay.style.inset = "0";
@@ -420,14 +420,14 @@ function drawAnnotation(
   const viewport = chart.getViewport(annotation.yAxis ?? "left");
   const xToPx = (x: number): number => ((x - viewport.xMin) / (viewport.xMax - viewport.xMin)) * width;
   const yToPx = (y: number): number => ((viewport.yMax - y) / (viewport.yMax - viewport.yMin)) * height;
-  const group = svg("g");
+  const group = createSvgElement("g");
   if (annotation.className) group.classList.add(annotation.className);
 
   switch (annotation.type) {
     case "x-line": {
       const x = xToPx(annotation.x);
       if (x < 0 || x > width) return;
-      const line = svg("line");
+      const line = createSvgElement("line");
       line.setAttribute("x1", String(x));
       line.setAttribute("x2", String(x));
       line.setAttribute("y1", "0");
@@ -440,7 +440,7 @@ function drawAnnotation(
     case "y-line": {
       const y = yToPx(annotation.y);
       if (y < 0 || y > height) return;
-      const line = svg("line");
+      const line = createSvgElement("line");
       line.setAttribute("x1", "0");
       line.setAttribute("x2", String(width));
       line.setAttribute("y1", String(y));
@@ -500,7 +500,7 @@ function styleStroke(el: SVGElement, color: string, width: number = 1, dash?: st
 }
 
 function appendRect(group: SVGGElement, rect: { x: number; y: number; w: number; h: number }, fill: string, stroke?: string, strokeWidth: number = 0): void {
-  const el = svg("rect");
+  const el = createSvgElement("rect");
   el.setAttribute("x", String(rect.x));
   el.setAttribute("y", String(rect.y));
   el.setAttribute("width", String(rect.w));
@@ -518,7 +518,7 @@ function appendMarker(group: SVGGElement, x: number, y: number, radius: number,
   const stroke = annotation.strokeColor ?? "rgba(0,0,0,0.35)";
   const strokeWidth = annotation.strokeWidth ?? 1;
   if (annotation.shape === "diamond") {
-    const polygon = svg("polygon");
+    const polygon = createSvgElement("polygon");
     polygon.setAttribute("points", `${x},${y - radius} ${x + radius},${y} ${x},${y + radius} ${x - radius},${y}`);
     polygon.setAttribute("fill", fill);
     polygon.setAttribute("stroke", stroke);
@@ -529,7 +529,7 @@ function appendMarker(group: SVGGElement, x: number, y: number, radius: number,
 
   if (annotation.shape === "cross") {
     for (const [x1, y1, x2, y2] of [[x - radius, y, x + radius, y], [x, y - radius, x, y + radius]] as const) {
-      const line = svg("line");
+      const line = createSvgElement("line");
       line.setAttribute("x1", String(x1));
       line.setAttribute("y1", String(y1));
       line.setAttribute("x2", String(x2));
@@ -540,7 +540,7 @@ function appendMarker(group: SVGGElement, x: number, y: number, radius: number,
     return;
   }
 
-  const circle = svg("circle");
+  const circle = createSvgElement("circle");
   circle.setAttribute("cx", String(x));
   circle.setAttribute("cy", String(y));
   circle.setAttribute("r", String(radius));
@@ -553,7 +553,7 @@ function appendMarker(group: SVGGElement, x: number, y: number, radius: number,
 function appendStandaloneLabel(group: SVGGElement, annotation: LabelAnnotation, x: number, y: number, defaultColor: string, defaultFont: string): void {
   const text = appendText(group, annotation.text, x, y, "start", annotation.color ?? defaultColor, annotation.font ?? defaultFont);
   if (annotation.backgroundColor) {
-    const rect = svg("rect");
+    const rect = createSvgElement("rect");
     rect.setAttribute("x", String(x - 4));
     rect.setAttribute("y", String(y - 14));
     rect.setAttribute("width", String(Math.max(16, annotation.text.length * 7 + 8)));
@@ -572,7 +572,7 @@ function appendLabel(group: SVGGElement, label: string | AnnotationLabelOptions
 }
 
 function appendText(group: SVGGElement, textValue: string, x: number, y: number, anchor: "start" | "middle" | "end", color: string, font: string): SVGTextElement {
-  const text = svg("text");
+  const text = createSvgElement("text");
   text.textContent = textValue;
   text.setAttribute("x", String(x));
   text.setAttribute("y", String(y));
diff --git a/src/ui/Crosshair.ts b/src/ui/Crosshair.ts
index ec322ee..269f8df 100644
--- a/src/ui/Crosshair.ts
+++ b/src/ui/Crosshair.ts
@@ -14,7 +14,7 @@ export type CrosshairLabelPlacement = "bottom-right" | "top-right" | "bottom-lef
 /** Custom renderer for crosshair pick highlights. */
 export type CrosshairHighlightRenderer = (position: CrosshairPosition, container: HTMLElement, chart: Chart) => void;
 
-/** Crosshair position in client and data coordinates. */
+/** Crosshair position in data coordinates and plot-relative CSS pixels. */
 export interface CrosshairPosition {
   readonly dataX: number;
   readonly dataY: number;
@@ -88,6 +88,12 @@ export interface CrosshairPlugin extends ChartPlugin {
   subscribe(event: "measurechange" | "measureend", callback: (measurement: RulerMeasurement) => void): () => void;
 }
 
+const SVG_NS = "http://www.w3.org/2000/svg";
+
+function createSvgElement<K extends keyof SVGElementTagNameMap>(tag: K): SVGElementTagNameMap[K] {
+  return document.createElementNS(SVG_NS, tag);
+}
+
 function countSamplesInRange(chart: ChartPluginContext, xMin: number, xMax: number): number {
   const viewport = { xMin, xMax, yMin: -Infinity, yMax: Infinity };
   let total = 0;
@@ -394,7 +400,7 @@ export function crosshairPlugin(options: CrosshairPluginOptions = {}): Crosshair
       label.style.font = options.labelFont ?? chart.theme.tooltipFont;
       label.style.whiteSpace = "nowrap";
 
-      rulerSvg = document.createElementNS("http://www.w3.org/2000/svg", "svg");
+      rulerSvg = createSvgElement("svg");
       rulerSvg.style.position = "absolute";
       rulerSvg.style.inset = "0";
       rulerSvg.style.width = "100%";
@@ -402,7 +408,7 @@ export function crosshairPlugin(options: CrosshairPluginOptions = {}): Crosshair
       rulerSvg.style.display = "none";
       rulerSvg.style.overflow = "hidden";
       rulerSvg.style.zIndex = "1";
-      rulerLine = document.createElementNS("http://www.w3.org/2000/svg", "line");
+      rulerLine = createSvgElement("line");
       rulerLine.setAttribute("stroke", color);
       rulerLine.setAttribute("stroke-width", String(options.width ?? 1));
       if (dash) rulerLine.setAttribute("stroke-dasharray", dash);
diff --git a/src/ui/Navigator.ts b/src/ui/Navigator.ts
index ab9fae7..d76b8fc 100644
--- a/src/ui/Navigator.ts
+++ b/src/ui/Navigator.ts
@@ -48,7 +48,7 @@ interface DragState {
 
 const SVG_NS = "http://www.w3.org/2000/svg";
 
-function svg<K extends keyof SVGElementTagNameMap>(tag: K): SVGElementTagNameMap[K] {
+function createSvgElement<K extends keyof SVGElementTagNameMap>(tag: K): SVGElementTagNameMap[K] {
   return document.createElementNS(SVG_NS, tag);
 }
 
@@ -169,7 +169,7 @@ export function navigatorPlugin(options: NavigatorPluginOptions = {}): Navigator
     overlay.setAttribute("preserveAspectRatio", "none");
 
     while (paths.length < selectedSeries.length) {
-      const path = svg("path");
+      const path = createSvgElement("path");
       path.setAttribute("fill", "none");
       path.setAttribute("vector-effect", "non-scaling-stroke");
       overlay.insertBefore(path, windowRect);
@@ -265,16 +265,16 @@ export function navigatorPlugin(options: NavigatorPluginOptions = {}): Navigator
         chart.setLayoutReservation(reservationId, placement === "top" ? { top: height + margin * 2 } : { bottom: height + margin * 2 });
       }
 
-      overlay = svg("svg");
+      overlay = createSvgElement("svg");
       overlay.style.width = "100%";
       overlay.style.height = "100%";
       overlay.setAttribute("aria-hidden", "true");
       overlay.style.display = "block";
-      windowRect = svg("rect");
-      leftHandle = svg("rect");
-      rightHandle = svg("rect");
-      leftHandleHit = svg("rect");
-      rightHandleHit = svg("rect");
+      windowRect = createSvgElement("rect");
+      leftHandle = createSvgElement("rect");
+      rightHandle = createSvgElement("rect");
+      leftHandleHit = createSvgElement("rect");
+      rightHandleHit = createSvgElement("rect");
       for (const handle of [leftHandle, rightHandle]) {
         handle.style.cursor = "ew-resize";
         handle.style.pointerEvents = "none";
diff --git a/src/ui/OverlayUtils.ts b/src/ui/OverlayUtils.ts
index af9d1e9..407a276 100644
--- a/src/ui/OverlayUtils.ts
+++ b/src/ui/OverlayUtils.ts
@@ -49,9 +49,9 @@ export function placeFixedWithinViewport(
   element: HTMLElement,
   clientX: number,
   clientY: number,
-  options: { readonly offsetX: number; readonly offsetY: number; readonly margin?: number },
+  options: { readonly offsetX: number; readonly offsetY: number; readonly margin?: number; readonly size?: { readonly width: number; readonly height: number } },
 ): void {
-  const rect = element.getBoundingClientRect();
+  const rect = options.size ?? element.getBoundingClientRect();
   const margin = options.margin ?? 4;
   const doc = element.ownerDocument;
   const viewportWidth = Math.max(1, globalThis.innerWidth || doc.documentElement.clientWidth);
diff --git a/src/ui/Tooltip.ts b/src/ui/Tooltip.ts
index c1f20cb..35e7503 100644
--- a/src/ui/Tooltip.ts
+++ b/src/ui/Tooltip.ts
@@ -1,5 +1,5 @@
 import type { Chart, ChartHoverState, ChartPickGroup, ChartPickItem, ChartPickMode, ChartPlugin, ChartPluginContext } from "./Chart.js";
-import { clamp, createLongPressTouchTracker, createOverlayLayer, createPickMarker, formatCompactNumber, pickAtDataX, rgba, renderPickItems } from "./OverlayUtils.js";
+import { createLongPressTouchTracker, createOverlayLayer, createPickMarker, formatCompactNumber, pickAtDataX, placeFixedWithinViewport, renderPickItems, rgba } from "./OverlayUtils.js";
 
 /** Options for the built-in hover tooltip plugin. */
 export interface TooltipPluginOptions {
@@ -50,14 +50,14 @@ interface TooltipPeer {
 const tooltipGroups = new Map<string, Set<TooltipPeer>>();
 
 function placeTooltip(container: HTMLElement, state: ChartHoverState, options: TooltipPluginOptions, size: { readonly width: number; readonly height: number }): void {
-  const margin = 4;
-  const width = Math.max(1, size.width || 240);
-  const height = Math.max(1, size.height || 80);
-  const viewportWidth = Math.max(1, globalThis.innerWidth || container.ownerDocument.documentElement.clientWidth);
-  const viewportHeight = Math.max(1, globalThis.innerHeight || container.ownerDocument.documentElement.clientHeight);
-  const x = clamp(state.clientX + (options.offsetX ?? 12), margin, Math.max(margin, viewportWidth - width - margin));
-  const y = clamp(state.clientY + (options.offsetY ?? 12), margin, Math.max(margin, viewportHeight - height - margin));
-  container.style.transform = `translate(${x}px, ${y}px)`;
+  placeFixedWithinViewport(container, state.clientX, state.clientY, {
+    offsetX: options.offsetX ?? 12,
+    offsetY: options.offsetY ?? 12,
+    size: {
+      width: Math.max(1, size.width || 240),
+      height: Math.max(1, size.height || 80),
+    },
+  });
 }
 
 /** Create a plugin that displays picked data values in a tooltip. */