diff --git a/openspec/changes/span-annotation/tasks.md b/openspec/changes/span-annotation/tasks.md
index 4292d7d..ef6eca4 100644
--- a/openspec/changes/span-annotation/tasks.md
+++ b/openspec/changes/span-annotation/tasks.md
@@ -21,12 +21,12 @@
 
 ## 4. SpanRectanglePrimitive (Chart Rendering)
 
-- [ ] 4.1 Create `SpanRectanglePrimitive.ts` implementing `ISeriesPrimitive` with data-space rectangle coordinates (start_time, end_time, max_high, min_low)
-- [ ] 4.2 Implement `updateAllViews()` with a pane renderer that converts time/price to pixel coordinates and draws a filled semi-transparent rectangle using `useBitmapCoordinateSpace`
-- [ ] 4.3 Implement label tag text rendering above the rectangle (pattern name)
-- [ ] 4.4 Implement `hitTest()` to detect clicks within the rectangle bounds
-- [ ] 4.5 Add highlight state (thicker border / increased opacity) for selected spans
-- [ ] 4.6 Set `zOrder: 'bottom'` so rectangles render behind candlesticks
+- [x] 4.1 Create `SpanRectanglePrimitive.ts` implementing `ISeriesPrimitive` with data-space rectangle coordinates (start_time, end_time, max_high, min_low)
+- [x] 4.2 Implement `updateAllViews()` with a pane renderer that converts time/price to pixel coordinates and draws a filled semi-transparent rectangle using `useBitmapCoordinateSpace`
+- [x] 4.3 Implement label tag text rendering above the rectangle (pattern name)
+- [x] 4.4 Implement `hitTest()` to detect clicks within the rectangle bounds
+- [x] 4.5 Add highlight state (thicker border / increased opacity) for selected spans
+- [x] 4.6 Set `zOrder: 'bottom'` so rectangles render behind candlesticks
 
 ## 5. Span Tool State & Integration
 
diff --git a/src/components/SpanRectanglePrimitive.ts b/src/components/SpanRectanglePrimitive.ts
new file mode 100644
index 0000000..3714eb5
--- /dev/null
+++ b/src/components/SpanRectanglePrimitive.ts
@@ -0,0 +1,240 @@
+import {
+  ISeriesPrimitive,
+  ISeriesPrimitivePaneView,
+  SeriesAttachedParameter,
+  Time,
+  Logical,
+} from 'lightweight-charts';
+
+export interface SpanData {
+  id: number;
+  start_time: number;
+  end_time: number;
+  label: string;
+  color: string;
+  max_high: number;
+  min_low: number;
+}
+
+export interface SpanRectanglePrimitiveOptions {
+  data: SpanData;
+  isSelected?: boolean;
+}
+
+class SpanRectanglePaneView implements ISeriesPrimitivePaneView {
+  private _data: SpanData;
+  private _isSelected: boolean;
+  private _series: SeriesAttachedParameter<Time> | null = null;
+
+  constructor(data: SpanData, isSelected: boolean = false) {
+    this._data = data;
+    this._isSelected = isSelected;
+  }
+
+  update(data: SpanData, isSelected: boolean, series: SeriesAttachedParameter<Time> | null): void {
+    this._data = data;
+    this._isSelected = isSelected;
+    this._series = series;
+  }
+
+  renderer() {
+    return new SpanRectangleRenderer(this._data, this._isSelected, this._series);
+  }
+
+  zOrder(): 'bottom' | 'normal' | 'top' {
+    return 'bottom'; // Render behind candlesticks
+  }
+}
+
+class SpanRectangleRenderer {
+  private _data: SpanData;
+  private _isSelected: boolean;
+  private _series: SeriesAttachedParameter<Time> | null;
+
+  constructor(data: SpanData, isSelected: boolean, series: SeriesAttachedParameter<Time> | null) {
+    this._data = data;
+    this._isSelected = isSelected;
+    this._series = series;
+  }
+
+  draw(target: CanvasRenderingContext2D): void {
+    if (!this._series) return;
+
+    target.save();
+
+    const timeScale = this._series.chart.timeScale();
+    const series = this._series.series;
+
+    // Convert time coordinates to pixel x coordinates
+    const x1 = timeScale.timeToCoordinate(this._data.start_time as Time);
+    const x2 = timeScale.timeToCoordinate(this._data.end_time as Time);
+
+    // Convert price coordinates to pixel y coordinates
+    const y1 = series.priceToCoordinate(this._data.max_high);
+    const y2 = series.priceToCoordinate(this._data.min_low);
+
+    // Check if coordinates are valid
+    if (x1 === null || x2 === null || y1 === null || y2 === null) {
+      target.restore();
+      return;
+    }
+
+    // Parse color and apply transparency
+    const baseOpacity = this._isSelected ? 0.3 : 0.2;
+    const fillColor = this._hexToRgba(this._data.color, baseOpacity);
+    const borderOpacity = this._isSelected ? 0.8 : 0.5;
+    const borderColor = this._hexToRgba(this._data.color, borderOpacity);
+    const borderWidth = this._isSelected ? 2 : 1;
+
+    // Calculate rectangle dimensions
+    const rectX = Math.min(x1, x2);
+    const rectY = Math.min(y1, y2);
+    const rectWidth = Math.abs(x2 - x1);
+    const rectHeight = Math.abs(y2 - y1);
+
+    // Draw filled rectangle
+    target.fillStyle = fillColor;
+    target.fillRect(rectX, rectY, rectWidth, rectHeight);
+
+    // Draw border
+    target.strokeStyle = borderColor;
+    target.lineWidth = borderWidth;
+    target.strokeRect(rectX, rectY, rectWidth, rectHeight);
+
+    // Draw label tag above rectangle
+    this._drawLabel(target, rectX, rectY, rectWidth);
+
+    target.restore();
+  }
+
+  private _drawLabel(ctx: CanvasRenderingContext2D, rectX: number, rectY: number, rectWidth: number): void {
+    const label = this._data.label.replace(/_/g, ' ').toUpperCase();
+    const fontSize = 11;
+    const padding = 4;
+
+    ctx.font = `${fontSize}px -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, sans-serif`;
+    const textMetrics = ctx.measureText(label);
+    const textWidth = textMetrics.width;
+    const textHeight = fontSize;
+
+    // Position label at top-left of rectangle, slightly offset
+    const labelX = rectX + 4;
+    const labelY = rectY - 2;
+
+    // Draw background
+    ctx.fillStyle = this._data.color;
+    ctx.fillRect(
+      labelX - padding,
+      labelY - textHeight - padding,
+      textWidth + padding * 2,
+      textHeight + padding * 2
+    );
+
+    // Draw text
+    ctx.fillStyle = '#ffffff';
+    ctx.textBaseline = 'top';
+    ctx.fillText(label, labelX, labelY - textHeight);
+  }
+
+  private _hexToRgba(hex: string, alpha: number): string {
+    // Remove # if present
+    hex = hex.replace('#', '');
+
+    // Parse hex to RGB
+    const r = parseInt(hex.substring(0, 2), 16);
+    const g = parseInt(hex.substring(2, 4), 16);
+    const b = parseInt(hex.substring(4, 6), 16);
+
+    return `rgba(${r}, ${g}, ${b}, ${alpha})`;
+  }
+}
+
+export class SpanRectanglePrimitive implements ISeriesPrimitive<Time> {
+  private _options: SpanRectanglePrimitiveOptions;
+  private _paneView: SpanRectanglePaneView;
+  private _series: SeriesAttachedParameter<Time> | null = null;
+
+  constructor(options: SpanRectanglePrimitiveOptions) {
+    this._options = options;
+    this._paneView = new SpanRectanglePaneView(options.data, options.isSelected ?? false);
+  }
+
+  attached(param: SeriesAttachedParameter<Time>): void {
+    this._series = param;
+    this.updateAllViews();
+  }
+
+  detached(): void {
+    this._series = null;
+  }
+
+  updateAllViews(): void {
+    this._paneView.update(this._options.data, this._options.isSelected ?? false, this._series);
+  }
+
+  paneViews() {
+    return [this._paneView];
+  }
+
+  updateData(data: SpanData): void {
+    this._options.data = data;
+    this.updateAllViews();
+  }
+
+  setSelected(isSelected: boolean): void {
+    this._options.isSelected = isSelected;
+    this.updateAllViews();
+  }
+
+  hitTest(x: number, y: number): boolean {
+    if (!this._series) return false;
+
+    const chart = this._series.chart;
+    const timeScale = chart.timeScale();
+
+    // Convert pixel x to time coordinate
+    const time = timeScale.coordinateToTime(x);
+    if (!time) return false;
+
+    const timeValue = typeof time === 'string' ? Date.parse(time) / 1000 : (time as number);
+
+    // Convert pixel y to price coordinate
+    const price = this._series.series.coordinateToPrice(y);
+    if (!price) return false;
+
+    // Check if click is within span bounds
+    const withinTimeRange = timeValue >= this._options.data.start_time && timeValue <= this._options.data.end_time;
+    const withinPriceRange = price >= this._options.data.min_low && price <= this._options.data.max_high;
+
+    return withinTimeRange && withinPriceRange;
+  }
+
+  autoscaleInfo(startTimePoint: Logical, endTimePoint: Logical) {
+    if (!this._series) return null;
+
+    const timeScale = this._series.chart.timeScale();
+    const startTime = timeScale.coordinateToTime(startTimePoint as any);
+    const endTime = timeScale.coordinateToTime(endTimePoint as any);
+
+    if (!startTime || !endTime) return null;
+
+    const startValue = typeof startTime === 'string' ? Date.parse(startTime) / 1000 : (startTime as number);
+    const endValue = typeof endTime === 'string' ? Date.parse(endTime) / 1000 : (endTime as number);
+
+    // Check if span overlaps with visible time range
+    const overlaps =
+      (this._options.data.start_time >= startValue && this._options.data.start_time <= endValue) ||
+      (this._options.data.end_time >= startValue && this._options.data.end_time <= endValue) ||
+      (this._options.data.start_time <= startValue && this._options.data.end_time >= endValue);
+
+    if (!overlaps) return null;
+
+    // Return price range of the span
+    return {
+      priceRange: {
+        minValue: this._options.data.min_low,
+        maxValue: this._options.data.max_high,
+      },
+    };
+  }
+}