diff --git a/packages/utils/CHANGELOG.md b/packages/utils/CHANGELOG.md
index 4f9c0e3fa..0c2c322bd 100644
--- a/packages/utils/CHANGELOG.md
+++ b/packages/utils/CHANGELOG.md
@@ -21,6 +21,9 @@
 ### Fixed
 
 - Reduced partial JSON parsing work for long streaming tool-call arguments by scaling the parse throttle geometrically with buffer size.
+### Fixed
+
+- Fixed Mermaid ASCII multi-word edge labels allowing routed lines to show through spaces ([#8098](https://github.com/can1357/oh-my-pi/issues/8098)).
 
 ## [17.2.11] - 2026-08-07
 
diff --git a/packages/utils/src/vendor/mermaid-ascii/ascii/canvas.ts b/packages/utils/src/vendor/mermaid-ascii/ascii/canvas.ts
index 49cf5e168..229934953 100644
--- a/packages/utils/src/vendor/mermaid-ascii/ascii/canvas.ts
+++ b/packages/utils/src/vendor/mermaid-ascii/ascii/canvas.ts
@@ -8,7 +8,7 @@
 
 import type { Canvas, DrawingCoord, RoleCanvas, CharRole, AsciiTheme, ColorMode } from './types'
 import { colorizeLine, DEFAULT_ASCII_THEME } from './ansi'
-import { displayWidth, toCells, WIDE_PAD } from '../text-metrics'
+import { displayWidth, LABEL_SPACE, toCells, WIDE_PAD } from '../text-metrics'
 
 /**
  * Create a blank canvas filled with spaces.
@@ -189,7 +189,7 @@ export function isJunctionChar(c: string): boolean {
  * letter/digit test misses.
  */
 function isLabelChar(c: string): boolean {
-  return c === WIDE_PAD || displayWidth(c) === 2 || /[\p{L}\p{N}]/u.test(c)
+  return c === LABEL_SPACE || c === WIDE_PAD || displayWidth(c) === 2 || /[\p{L}\p{N}]/u.test(c)
 }
 
 /**
@@ -268,7 +268,7 @@ export function mergeCanvases(
     for (let x = 0; x < overlay.length; x++) {
       for (let y = 0; y < overlay[0]!.length; y++) {
         const c = overlay[x]![y]!
-        // WIDE_PAD cells are written atomically with their lead below
+        // Spaces are transparent; WIDE_PAD cells are written atomically with their lead below
         if (c === ' ' || c === WIDE_PAD) continue
         const mx = x + offset.x
         const my = y + offset.y
@@ -327,8 +327,8 @@ export function canvasToString(canvas: Canvas, options?: CanvasToStringOptions):
       let line = ''
       for (let x = 0; x <= maxX; x++) {
         const c = canvas[x]![y]!
-        // Skip wide-glyph continuation cells: the glyph itself spans 2 columns
-        if (c !== WIDE_PAD) line += c
+        // Skip wide-glyph continuation cells and restore opaque label spaces.
+        if (c !== WIDE_PAD) line += c === LABEL_SPACE ? ' ' : c
       }
       lines.push(line)
     } else {
@@ -338,7 +338,7 @@ export function canvasToString(canvas: Canvas, options?: CanvasToStringOptions):
       for (let x = 0; x <= maxX; x++) {
         const c = canvas[x]![y]!
         if (c === WIDE_PAD) continue
-        chars.push(c)
+        chars.push(c === LABEL_SPACE ? ' ' : c)
         roles.push(roleCanvas[x]?.[y] ?? null)
       }
       lines.push(colorizeLine(chars, roles, theme, colorMode))
diff --git a/packages/utils/src/vendor/mermaid-ascii/ascii/draw.ts b/packages/utils/src/vendor/mermaid-ascii/ascii/draw.ts
index 1cefc6c49..2e1e86189 100644
--- a/packages/utils/src/vendor/mermaid-ascii/ascii/draw.ts
+++ b/packages/utils/src/vendor/mermaid-ascii/ascii/draw.ts
@@ -21,7 +21,7 @@ import { gridToDrawingCoord, lineToDrawing } from './grid'
 import { splitLines } from './multiline-utils'
 import { getCorners } from './shapes/corners'
 import { getShapeAttachmentPoint } from './shapes/index'
-import { displayWidth, toCells, WIDE_PAD } from '../text-metrics'
+import { displayWidth, LABEL_SPACE, toCells, WIDE_PAD } from '../text-metrics'
 
 // ============================================================================
 // Node drawing — renders a node using shape-aware rendering
@@ -679,7 +679,7 @@ function drawTextOnLine(canvas: Canvas, line: DrawingCoord[], label: string, isU
   for (let i = 0; i < lines.length; i++) {
     const lineText = lines[i]!
     const startX = middleX - Math.floor(displayWidth(lineText) / 2)
-    drawText(canvas, { x: startX, y: startY + i }, lineText)
+    drawText(canvas, { x: startX, y: startY + i }, lineText.replaceAll(' ', LABEL_SPACE))
   }
 }
 
diff --git a/packages/utils/src/vendor/mermaid-ascii/text-metrics.ts b/packages/utils/src/vendor/mermaid-ascii/text-metrics.ts
index 77c89e7b0..ebe805f3d 100644
--- a/packages/utils/src/vendor/mermaid-ascii/text-metrics.ts
+++ b/packages/utils/src/vendor/mermaid-ascii/text-metrics.ts
@@ -29,6 +29,9 @@
  */
 export const WIDE_PAD = '\u0000'
 
+/** Opaque label-space placeholder that serializes back to a regular space. */
+export const LABEL_SPACE = '\u0001'
+
 const graphemeSegmenter = new Intl.Segmenter()
 
 /**
diff --git a/packages/utils/test/mermaid-ascii.test.ts b/packages/utils/test/mermaid-ascii.test.ts
index 1486b3e17..5f0100862 100644
--- a/packages/utils/test/mermaid-ascii.test.ts
+++ b/packages/utils/test/mermaid-ascii.test.ts
@@ -37,6 +37,24 @@ describe("renderMermaidAscii", () => {
 		expect(rows[markerRow + 1]).toMatch(/╰─+╯/);
 	});
 
+	it("masks routed lines behind spaces in edge labels", () => {
+		const horizontal = renderMermaidAscii(
+			["graph LR", "  A[Agent] -->|on Mac| B[Server]", "  A -->|on Linux| C[Cluster]"].join("\n"),
+			{ colorMode: "none", useAscii: false },
+		);
+		const vertical = renderMermaidAscii("graph TD\n  A[Agent] -->|to c| C[Cluster]", {
+			colorMode: "none",
+			useAscii: false,
+		});
+
+		expect(horizontal).toContain("on Mac");
+		expect(horizontal).toContain("on Linux");
+		expect(horizontal).not.toContain("on─Mac");
+		expect(horizontal).not.toContain("on─Linux");
+		expect(vertical).toContain("to c");
+		expect(vertical).not.toContain("to│c");
+	});
+
 	it("returns a bounded fallback for declaration orders that make a clean route unreachable", () => {
 		const rendered = renderMermaidAsciiSafe(
 			[