diff --git a/app/src/api/__tests__/engine.test.ts b/app/src/api/__tests__/engine.test.ts
index 9af4897..4d75f20 100644
--- a/app/src/api/__tests__/engine.test.ts
+++ b/app/src/api/__tests__/engine.test.ts
@@ -1,5 +1,5 @@
 import { describe, it, expect, vi, beforeEach, afterEach } from 'vitest';
-import { getPresets, traceImage, simplifyVector } from '../engine';
+import { getPresets, traceImage, simplifyVector, exportAsDxf } from '../engine';
 
 // ---------- helpers ----------
 
@@ -147,3 +147,72 @@ describe('simplifyVector', () => {
     await expect(simplifyVector(file, 1.0)).rejects.toThrow(/failed.*400/i);
   });
 });
+
+// ---------- exportAsDxf ----------
+
+function mockFetchBlob(blobContent: string) {
+  return vi.fn().mockResolvedValue({
+    ok: true,
+    status: 200,
+    blob: () => Promise.resolve(new Blob([blobContent], { type: 'application/octet-stream' })),
+    text: () => Promise.resolve(blobContent),
+  });
+}
+
+describe('exportAsDxf', () => {
+  it('sends FormData with SVG content, output_format=dxf, units, and scale_factor', async () => {
+    globalThis.fetch = mockFetchBlob('DXF_CONTENT_BINARY');
+
+    const svgContent = '<svg xmlns="http://www.w3.org/2000/svg"><rect width="100" height="100"/></svg>';
+    const result = await exportAsDxf(svgContent, 'inches', 0.010416667);
+
+    expect(globalThis.fetch).toHaveBeenCalledOnce();
+    const [url, opts] = (globalThis.fetch as ReturnType<typeof vi.fn>).mock.calls[0];
+    expect(url).toBe('/engine/simplify');
+    expect(opts.method).toBe('POST');
+
+    const body: FormData = opts.body;
+    expect(body).toBeInstanceOf(FormData);
+    expect(body.get('output_format')).toBe('dxf');
+    expect(body.get('units')).toBe('inches');
+    expect(body.get('scale_factor')).toBe('0.010416667');
+
+    // File should be present as a Blob
+    const file = body.get('file');
+    expect(file).toBeInstanceOf(Blob);
+
+    // Result should be a Blob
+    expect(result).toBeInstanceOf(Blob);
+    const text = await result.text();
+    expect(text).toBe('DXF_CONTENT_BINARY');
+  });
+
+  it('sends mm units correctly', async () => {
+    globalThis.fetch = mockFetchBlob('DXF_MM');
+
+    await exportAsDxf('<svg/>', 'mm', 0.264583333);
+
+    const [, opts] = (globalThis.fetch as ReturnType<typeof vi.fn>).mock.calls[0];
+    const body: FormData = opts.body;
+    expect(body.get('units')).toBe('mm');
+    expect(body.get('scale_factor')).toBe('0.264583333');
+  });
+
+  it('passes AbortSignal when provided', async () => {
+    globalThis.fetch = mockFetchBlob('DXF');
+    const controller = new AbortController();
+
+    await exportAsDxf('<svg/>', 'inches', 1.0, controller.signal);
+
+    const [, opts] = (globalThis.fetch as ReturnType<typeof vi.fn>).mock.calls[0];
+    expect(opts.signal).toBe(controller.signal);
+  });
+
+  it('throws on non-ok response', async () => {
+    globalThis.fetch = mockFetchFail(500, 'Internal Server Error');
+
+    await expect(
+      exportAsDxf('<svg/>', 'inches', 1.0),
+    ).rejects.toThrow(/DXF export.*failed.*500/i);
+  });
+});
diff --git a/app/src/api/engine.ts b/app/src/api/engine.ts
index e4609cc..c8f7f7d 100644
--- a/app/src/api/engine.ts
+++ b/app/src/api/engine.ts
@@ -67,3 +67,37 @@ export async function simplifyVector(
   }
   return res.json() as Promise<TraceResponse>;
 }
+
+/**
+ * Export an SVG as DXF via the engine's simplify endpoint.
+ *
+ * Posts the SVG content as a file with output_format=dxf, along with
+ * units and scale_factor parameters. Returns the raw DXF binary as a Blob.
+ */
+export async function exportAsDxf(
+  svgContent: string,
+  units: 'inches' | 'mm',
+  scaleFactor: number,
+  signal?: AbortSignal,
+): Promise<Blob> {
+  const form = new FormData();
+  form.append(
+    'file',
+    new Blob([svgContent], { type: 'image/svg+xml' }),
+    'export.svg',
+  );
+  form.append('output_format', 'dxf');
+  form.append('units', units);
+  form.append('scale_factor', String(scaleFactor));
+
+  const res = await fetch(`${BASE}/simplify`, {
+    method: 'POST',
+    body: form,
+    signal,
+  });
+  if (!res.ok) {
+    const detail = await res.text().catch(() => res.statusText);
+    throw new Error(`POST /engine/simplify (DXF export) failed: ${res.status} — ${detail}`);
+  }
+  return res.blob();
+}
diff --git a/app/src/hooks/__tests__/useDebouncedTrace.test.ts b/app/src/hooks/__tests__/useDebouncedTrace.test.ts
index 9128ff4..f2a2657 100644
--- a/app/src/hooks/__tests__/useDebouncedTrace.test.ts
+++ b/app/src/hooks/__tests__/useDebouncedTrace.test.ts
@@ -88,7 +88,7 @@ describe('useDebouncedTrace', () => {
   });
 
   it('passes AbortSignal to fetch and aborts previous requests', async () => {
-    let firstSignal: AbortSignal | undefined;
+    let firstSignal: AbortSignal | null | undefined;
     let callCount = 0;
     globalThis.fetch = vi.fn().mockImplementation((_url: string, opts?: RequestInit) => {
       callCount++;
@@ -105,7 +105,7 @@ describe('useDebouncedTrace', () => {
 
     const file = new File(['pixels'], 'test.png', { type: 'image/png' });
 
-    const { result, rerender } = renderHook(
+    const { rerender } = renderHook(
       ({ params }) => useDebouncedTrace(file, 'sign', params, DEBOUNCE_MS),
       { initialProps: { params: { epsilon: 1 } as Record<string, unknown> } },
     );
diff --git a/app/src/types/opentype.d.ts b/app/src/types/opentype.d.ts
new file mode 100644
index 0000000..b676e0e
--- /dev/null
+++ b/app/src/types/opentype.d.ts
@@ -0,0 +1,33 @@
+declare module 'opentype.js' {
+  interface Glyph {
+    advanceWidth: number;
+    getPath(x: number, y: number, fontSize: number): Path;
+  }
+
+  interface PathCommand {
+    type: string;
+    x?: number;
+    y?: number;
+    x1?: number;
+    y1?: number;
+    x2?: number;
+    y2?: number;
+  }
+
+  interface Path {
+    commands: PathCommand[];
+    toPathData(decimalPlaces?: number): string;
+  }
+
+  interface Font {
+    unitsPerEm: number;
+    ascender: number;
+    descender: number;
+    charToGlyph(char: string): Glyph;
+    getPath(text: string, x: number, y: number, fontSize: number): Path;
+    stringToGlyphs(text: string): Glyph[];
+  }
+
+  export function parse(buffer: ArrayBuffer): Font;
+  export function load(url: string, callback: (err: Error | null, font?: Font) => void): void;
+}
diff --git a/app/src/utils/__tests__/exportService.test.ts b/app/src/utils/__tests__/exportService.test.ts
new file mode 100644
index 0000000..f4a7a3a
--- /dev/null
+++ b/app/src/utils/__tests__/exportService.test.ts
@@ -0,0 +1,401 @@
+import { describe, it, expect, vi, afterEach } from 'vitest';
+import {
+  composeCanvasSVG,
+  validateForExport,
+  triggerDownload,
+} from '../exportService';
+import type {
+  ArtboardConfig,
+  CanvasObject,
+  RectObject,
+  CircleObject,
+  EllipseObject,
+  LineObject,
+  ImageObject,
+  TextObject,
+} from '../../types/canvas';
+
+// -- Helpers ------------------------------------------------------------------
+
+function makeArtboard(overrides?: Partial<ArtboardConfig>): ArtboardConfig {
+  return {
+    shape: 'rect',
+    width: 4,
+    height: 6,
+    unit: 'inches',
+    ...overrides,
+  };
+}
+
+function makeRect(overrides?: Partial<RectObject>): RectObject {
+  return {
+    id: 'rect-1',
+    name: 'Rectangle 1',
+    type: 'rect',
+    x: 10,
+    y: 20,
+    width: 100,
+    height: 50,
+    rotation: 0,
+    visible: true,
+    locked: false,
+    opacity: 1,
+    fill: '#ff0000',
+    stroke: '#000000',
+    strokeWidth: 2,
+    ...overrides,
+  };
+}
+
+function makeCircle(overrides?: Partial<CircleObject>): CircleObject {
+  return {
+    id: 'circle-1',
+    name: 'Circle 1',
+    type: 'circle',
+    x: 50,
+    y: 50,
+    radius: 25,
+    rotation: 0,
+    visible: true,
+    locked: false,
+    opacity: 1,
+    fill: '#00ff00',
+    stroke: '#000000',
+    strokeWidth: 1,
+    ...overrides,
+  };
+}
+
+function makeEllipse(overrides?: Partial<EllipseObject>): EllipseObject {
+  return {
+    id: 'ellipse-1',
+    name: 'Ellipse 1',
+    type: 'ellipse',
+    x: 100,
+    y: 100,
+    radiusX: 40,
+    radiusY: 20,
+    rotation: 0,
+    visible: true,
+    locked: false,
+    opacity: 1,
+    fill: '#0000ff',
+    stroke: '#000000',
+    strokeWidth: 1,
+    ...overrides,
+  };
+}
+
+function makeLine(overrides?: Partial<LineObject>): LineObject {
+  return {
+    id: 'line-1',
+    name: 'Line 1',
+    type: 'line',
+    x: 0,
+    y: 0,
+    points: [10, 20, 30, 40, 50, 60],
+    rotation: 0,
+    visible: true,
+    locked: false,
+    opacity: 1,
+    stroke: '#333333',
+    strokeWidth: 3,
+    lineStyle: 'solid',
+    dash: [],
+    ...overrides,
+  };
+}
+
+function makeImage(overrides?: Partial<ImageObject>): ImageObject {
+  return {
+    id: 'img-1',
+    name: 'Image 1',
+    type: 'image',
+    x: 10,
+    y: 10,
+    width: 200,
+    height: 150,
+    rotation: 0,
+    visible: true,
+    locked: false,
+    opacity: 1,
+    src: 'blob:http://localhost:3000/abc-image/svg+xml',
+    ...overrides,
+  };
+}
+
+function makeText(overrides?: Partial<TextObject>): TextObject {
+  return {
+    id: 'text-1',
+    name: 'Text 1',
+    type: 'text',
+    x: 10,
+    y: 10,
+    text: 'Hello',
+    fontFamily: 'Roboto',
+    fontSize: 24,
+    letterSpacing: 0,
+    lineHeight: 1.2,
+    fill: '#000000',
+    stroke: '',
+    strokeWidth: 0,
+    width: 200,
+    rotation: 0,
+    visible: true,
+    locked: false,
+    opacity: 1,
+    ...overrides,
+  };
+}
+
+// -- validateForExport --------------------------------------------------------
+
+describe('validateForExport', () => {
+  it('returns valid=true with no issues for clean objects', () => {
+    const artboard = makeArtboard();
+    const objects: CanvasObject[] = [makeRect(), makeCircle()];
+    const result = validateForExport(objects, artboard);
+    expect(result.valid).toBe(true);
+    expect(result.issues).toHaveLength(0);
+  });
+
+  it('returns error when artboard is null', () => {
+    const result = validateForExport([makeRect()], null);
+    expect(result.valid).toBe(false);
+    expect(result.issues).toHaveLength(1);
+    expect(result.issues[0].severity).toBe('error');
+    expect(result.issues[0].message).toMatch(/artboard/i);
+  });
+
+  it('returns error for visible text objects', () => {
+    const artboard = makeArtboard();
+    const text = makeText();
+    const result = validateForExport([text], artboard);
+    expect(result.valid).toBe(false);
+    const textIssue = result.issues.find(
+      (i) => i.objectId === 'text-1',
+    );
+    expect(textIssue).toBeDefined();
+    expect(textIssue!.severity).toBe('error');
+    expect(textIssue!.message).toMatch(/converted to paths/i);
+  });
+
+  it('ignores hidden text objects', () => {
+    const artboard = makeArtboard();
+    const text = makeText({ visible: false });
+    const result = validateForExport([text], artboard);
+    expect(result.valid).toBe(true);
+    expect(result.issues).toHaveLength(0);
+  });
+
+  it('warns on raster images', () => {
+    const artboard = makeArtboard();
+    const img = makeImage({ src: 'blob:http://localhost:3000/raster-png' });
+    const result = validateForExport([img], artboard);
+    expect(result.valid).toBe(true);
+    const imgIssue = result.issues.find(
+      (i) => i.objectId === 'img-1',
+    );
+    expect(imgIssue).toBeDefined();
+    expect(imgIssue!.severity).toBe('warning');
+    expect(imgIssue!.message).toMatch(/raster/i);
+  });
+
+  it('does not warn on SVG image sources', () => {
+    const artboard = makeArtboard();
+    const img = makeImage({
+      src: 'blob:http://localhost:3000/abc-image/svg+xml',
+    });
+    const result = validateForExport([img], artboard);
+    expect(result.valid).toBe(true);
+    expect(result.issues).toHaveLength(0);
+  });
+
+  it('collects multiple issues', () => {
+    const text = makeText();
+    const rasterImg = makeImage({
+      id: 'img-raster',
+      name: 'Raster',
+      src: 'data:image/png;base64,abc',
+    });
+    const result = validateForExport([text, rasterImg], null);
+    expect(result.valid).toBe(false);
+    // artboard error + text error + raster warning = 3
+    expect(result.issues).toHaveLength(3);
+    const errors = result.issues.filter((i) => i.severity === 'error');
+    const warnings = result.issues.filter((i) => i.severity === 'warning');
+    expect(errors).toHaveLength(2);
+    expect(warnings).toHaveLength(1);
+  });
+});
+
+// -- composeCanvasSVG ---------------------------------------------------------
+
+describe('composeCanvasSVG', () => {
+  it('produces SVG with correct viewBox and real-world dimensions (inches)', () => {
+    const artboard = makeArtboard({ width: 4, height: 6, unit: 'inches' });
+    const svg = composeCanvasSVG([], artboard);
+    // 4in * 96 PPI = 384px, 6in * 96 PPI = 576px
+    expect(svg).toContain('viewBox="0 0 384 576"');
+    expect(svg).toContain('width="4in"');
+    expect(svg).toContain('height="6in"');
+  });
+
+  it('produces SVG with correct dimensions (mm)', () => {
+    const artboard = makeArtboard({ width: 100, height: 200, unit: 'mm' });
+    const svg = composeCanvasSVG([], artboard);
+    expect(svg).toContain('width="100mm"');
+    expect(svg).toContain('height="200mm"');
+    // 100mm * (96/25.4) ≈ 377.9528
+    expect(svg).toMatch(/viewBox="0 0 377\.95\d* 755\.90\d*"/);
+  });
+
+  it('renders rect objects correctly', () => {
+    const artboard = makeArtboard();
+    const rect = makeRect({ x: 10, y: 20, width: 100, height: 50 });
+    const svg = composeCanvasSVG([rect], artboard);
+    expect(svg).toContain('<rect');
+    expect(svg).toContain('x="10"');
+    expect(svg).toContain('y="20"');
+    expect(svg).toContain('width="100"');
+    expect(svg).toContain('height="50"');
+  });
+
+  it('renders circle objects correctly', () => {
+    const artboard = makeArtboard();
+    const circle = makeCircle({ x: 50, y: 50, radius: 25 });
+    const svg = composeCanvasSVG([circle], artboard);
+    expect(svg).toContain('<circle');
+    expect(svg).toContain('cx="50"');
+    expect(svg).toContain('cy="50"');
+    expect(svg).toContain('r="25"');
+  });
+
+  it('renders ellipse objects correctly', () => {
+    const artboard = makeArtboard();
+    const ellipse = makeEllipse({ x: 100, y: 100, radiusX: 40, radiusY: 20 });
+    const svg = composeCanvasSVG([ellipse], artboard);
+    expect(svg).toContain('<ellipse');
+    expect(svg).toContain('cx="100"');
+    expect(svg).toContain('cy="100"');
+    expect(svg).toContain('rx="40"');
+    expect(svg).toContain('ry="20"');
+  });
+
+  it('renders line objects as polyline', () => {
+    const artboard = makeArtboard();
+    const line = makeLine({ x: 5, y: 10, points: [0, 0, 20, 30] });
+    const svg = composeCanvasSVG([line], artboard);
+    expect(svg).toContain('<polyline');
+    // Points are offset by obj.x/obj.y: (5+0, 10+0) (5+20, 10+30) → "5,10 25,40"
+    expect(svg).toContain('points="5,10 25,40"');
+    expect(svg).toContain('fill="none"');
+  });
+
+  it('renders SVG images as <image> elements', () => {
+    const artboard = makeArtboard();
+    const img = makeImage({
+      src: 'blob:http://localhost:3000/abc-image/svg+xml',
+    });
+    const svg = composeCanvasSVG([img], artboard);
+    expect(svg).toContain('<image');
+    expect(svg).toContain('href=');
+  });
+
+  it('skips hidden objects', () => {
+    const artboard = makeArtboard();
+    const rect = makeRect({ visible: false });
+    const svg = composeCanvasSVG([rect], artboard);
+    expect(svg).not.toContain('<rect');
+  });
+
+  it('skips text objects', () => {
+    const artboard = makeArtboard();
+    const text = makeText();
+    const svg = composeCanvasSVG([text], artboard);
+    expect(svg).not.toContain('<text');
+    expect(svg).not.toContain('Hello');
+  });
+
+  it('skips raster images', () => {
+    const artboard = makeArtboard();
+    const img = makeImage({
+      src: 'data:image/png;base64,abc',
+    });
+    const svg = composeCanvasSVG([img], artboard);
+    expect(svg).not.toContain('<image');
+  });
+
+  it('applies rotation transform when non-zero', () => {
+    const artboard = makeArtboard();
+    const rect = makeRect({ rotation: 45, x: 10, y: 20, width: 100, height: 50 });
+    const svg = composeCanvasSVG([rect], artboard);
+    // Center: (10+50, 20+25) = (60, 45)
+    expect(svg).toContain('transform="rotate(45 60 45)"');
+  });
+
+  it('renders multiple objects in order', () => {
+    const artboard = makeArtboard();
+    const objects: CanvasObject[] = [
+      makeRect({ id: 'r1', name: 'R1' }),
+      makeCircle({ id: 'c1', name: 'C1' }),
+    ];
+    const svg = composeCanvasSVG(objects, artboard);
+    const rectIdx = svg.indexOf('<rect');
+    const circleIdx = svg.indexOf('<circle');
+    expect(rectIdx).toBeLessThan(circleIdx);
+  });
+
+  it('includes stroke-dasharray for dashed lines', () => {
+    const artboard = makeArtboard();
+    const line = makeLine({ dash: [5, 3] });
+    const svg = composeCanvasSVG([line], artboard);
+    expect(svg).toContain('stroke-dasharray="5 3"');
+  });
+});
+
+// -- triggerDownload ----------------------------------------------------------
+
+describe('triggerDownload', () => {
+  afterEach(() => {
+    vi.restoreAllMocks();
+  });
+
+  it('creates a blob URL and triggers a download', () => {
+    // Activate fake timers before calling triggerDownload so setTimeout is captured
+    vi.useFakeTimers();
+
+    const blob = new Blob(['test content'], { type: 'text/plain' });
+    const mockUrl = 'blob:http://localhost:3000/mock-blob-url';
+
+    const createObjectURLSpy = vi
+      .spyOn(URL, 'createObjectURL')
+      .mockReturnValue(mockUrl);
+    const revokeObjectURLSpy = vi
+      .spyOn(URL, 'revokeObjectURL')
+      .mockImplementation(() => {});
+
+    const clickSpy = vi.fn();
+    const appendChildSpy = vi.spyOn(document.body, 'appendChild');
+    const removeChildSpy = vi.spyOn(document.body, 'removeChild');
+
+    // Mock createElement to return a spy-able anchor
+    const mockAnchor = document.createElement('a');
+    mockAnchor.click = clickSpy;
+    vi.spyOn(document, 'createElement').mockReturnValue(mockAnchor);
+
+    triggerDownload(blob, 'test-file.svg');
+
+    expect(createObjectURLSpy).toHaveBeenCalledWith(blob);
+    expect(mockAnchor.href).toBe(mockUrl);
+    expect(mockAnchor.download).toBe('test-file.svg');
+    expect(clickSpy).toHaveBeenCalledOnce();
+    expect(appendChildSpy).toHaveBeenCalledWith(mockAnchor);
+
+    // Cleanup happens after setTimeout — advance timers
+    vi.advanceTimersByTime(150);
+    expect(removeChildSpy).toHaveBeenCalled();
+    expect(revokeObjectURLSpy).toHaveBeenCalledWith(mockUrl);
+    vi.useRealTimers();
+  });
+});
diff --git a/app/src/utils/__tests__/fontService.test.ts b/app/src/utils/__tests__/fontService.test.ts
index f3d807c..611c645 100644
--- a/app/src/utils/__tests__/fontService.test.ts
+++ b/app/src/utils/__tests__/fontService.test.ts
@@ -1,6 +1,8 @@
+/// <reference types="node" />
 import { describe, it, expect, beforeEach, vi, afterEach } from 'vitest';
 import * as fs from 'node:fs';
 import * as path from 'node:path';
+import { fileURLToPath } from 'node:url';
 import {
   loadFont,
   loadFontByFamily,
@@ -10,13 +12,16 @@ import {
   isFontCached,
 } from '../fontService';
 
+const __filename_local = fileURLToPath(import.meta.url);
+const __dirname_local = path.dirname(__filename_local);
+
 /**
  * Load a real .ttf file from disk and return it as an ArrayBuffer.
  * This lets us mock fetch() with real font data so opentype.js
  * produces genuine glyph paths, proving the integration end-to-end.
  */
 function readFontFile(filename: string): ArrayBuffer {
-  const fontPath = path.resolve(__dirname, '../../../public/fonts', filename);
+  const fontPath = path.resolve(__dirname_local, '../../../public/fonts', filename);
   const buffer = fs.readFileSync(fontPath);
   return buffer.buffer.slice(
     buffer.byteOffset,
diff --git a/app/src/utils/exportService.ts b/app/src/utils/exportService.ts
new file mode 100644
index 0000000..916d447
--- /dev/null
+++ b/app/src/utils/exportService.ts
@@ -0,0 +1,289 @@
+/**
+ * Export service: SVG composition, validation, and browser download trigger.
+ *
+ * Pure utility functions that operate on canvas state to produce export-ready
+ * SVG content. No React dependencies — consumed by ExportView (T04).
+ */
+
+import type {
+  CanvasObject,
+  ArtboardConfig,
+  RectObject,
+  CircleObject,
+  EllipseObject,
+  LineObject,
+  ImageObject,
+} from '../types/canvas';
+import { toPx } from './artboardShapes';
+
+// -- Validation ---------------------------------------------------------------
+
+export type ValidationSeverity = 'error' | 'warning';
+
+export interface ValidationIssue {
+  severity: ValidationSeverity;
+  message: string;
+  objectId?: string;
+  objectName?: string;
+}
+
+export interface ValidationResult {
+  valid: boolean;
+  issues: ValidationIssue[];
+}
+
+/**
+ * Validate canvas objects for export readiness.
+ *
+ * Blocking errors (valid=false):
+ * - TextObject present (must be converted to paths first)
+ * - Missing artboard (no artboard configured)
+ *
+ * Warnings (valid=true but with issues):
+ * - Raster-only images (non-SVG image sources)
+ */
+export function validateForExport(
+  objects: CanvasObject[],
+  artboard: ArtboardConfig | null,
+): ValidationResult {
+  const issues: ValidationIssue[] = [];
+
+  // Check for missing artboard
+  if (!artboard) {
+    issues.push({
+      severity: 'error',
+      message: 'No artboard configured. Set up an artboard before exporting.',
+    });
+  }
+
+  for (const obj of objects) {
+    if (!obj.visible) continue;
+
+    if (obj.type === 'text') {
+      issues.push({
+        severity: 'error',
+        message: `Text object "${obj.name}" must be converted to paths before export.`,
+        objectId: obj.id,
+        objectName: obj.name,
+      });
+    }
+
+    if (obj.type === 'image') {
+      // SVG blob URLs contain 'image/svg+xml' in their origin or are data:image/svg+xml
+      const isSvgSrc =
+        obj.src.includes('image/svg+xml') || obj.src.endsWith('.svg');
+      if (!isSvgSrc) {
+        issues.push({
+          severity: 'warning',
+          message: `Image "${obj.name}" is raster-only and will be skipped in vector export.`,
+          objectId: obj.id,
+          objectName: obj.name,
+        });
+      }
+    }
+  }
+
+  const hasErrors = issues.some((i) => i.severity === 'error');
+  return { valid: !hasErrors, issues };
+}
+
+// -- SVG Composition ----------------------------------------------------------
+
+/** Escape XML special characters in attribute values. */
+function escapeXml(str: string): string {
+  return str
+    .replace(/&/g, '&amp;')
+    .replace(/</g, '&lt;')
+    .replace(/>/g, '&gt;')
+    .replace(/"/g, '&quot;')
+    .replace(/'/g, '&apos;');
+}
+
+/** Format a number to a reasonable precision for SVG attributes. */
+function n(value: number): string {
+  return Number(value.toFixed(4)).toString();
+}
+
+function renderRect(obj: RectObject): string {
+  const attrs = [
+    `x="${n(obj.x)}"`,
+    `y="${n(obj.y)}"`,
+    `width="${n(obj.width)}"`,
+    `height="${n(obj.height)}"`,
+    `fill="${escapeXml(obj.fill)}"`,
+    `stroke="${escapeXml(obj.stroke)}"`,
+    `stroke-width="${n(obj.strokeWidth)}"`,
+    `opacity="${n(obj.opacity)}"`,
+  ];
+  if (obj.rotation !== 0) {
+    const cx = obj.x + obj.width / 2;
+    const cy = obj.y + obj.height / 2;
+    attrs.push(`transform="rotate(${n(obj.rotation)} ${n(cx)} ${n(cy)})"`);
+  }
+  return `  <rect ${attrs.join(' ')} />`;
+}
+
+function renderCircle(obj: CircleObject): string {
+  const attrs = [
+    `cx="${n(obj.x)}"`,
+    `cy="${n(obj.y)}"`,
+    `r="${n(obj.radius)}"`,
+    `fill="${escapeXml(obj.fill)}"`,
+    `stroke="${escapeXml(obj.stroke)}"`,
+    `stroke-width="${n(obj.strokeWidth)}"`,
+    `opacity="${n(obj.opacity)}"`,
+  ];
+  if (obj.rotation !== 0) {
+    attrs.push(`transform="rotate(${n(obj.rotation)} ${n(obj.x)} ${n(obj.y)})"`);
+  }
+  return `  <circle ${attrs.join(' ')} />`;
+}
+
+function renderEllipse(obj: EllipseObject): string {
+  const attrs = [
+    `cx="${n(obj.x)}"`,
+    `cy="${n(obj.y)}"`,
+    `rx="${n(obj.radiusX)}"`,
+    `ry="${n(obj.radiusY)}"`,
+    `fill="${escapeXml(obj.fill)}"`,
+    `stroke="${escapeXml(obj.stroke)}"`,
+    `stroke-width="${n(obj.strokeWidth)}"`,
+    `opacity="${n(obj.opacity)}"`,
+  ];
+  if (obj.rotation !== 0) {
+    attrs.push(`transform="rotate(${n(obj.rotation)} ${n(obj.x)} ${n(obj.y)})"`);
+  }
+  return `  <ellipse ${attrs.join(' ')} />`;
+}
+
+function renderLine(obj: LineObject): string {
+  // LineObject.points are [x1, y1, x2, y2, ...] relative to obj.x, obj.y
+  const pointPairs: string[] = [];
+  for (let i = 0; i < obj.points.length; i += 2) {
+    const px = obj.x + (obj.points[i] ?? 0);
+    const py = obj.y + (obj.points[i + 1] ?? 0);
+    pointPairs.push(`${n(px)},${n(py)}`);
+  }
+  const attrs = [
+    `points="${pointPairs.join(' ')}"`,
+    `fill="none"`,
+    `stroke="${escapeXml(obj.stroke)}"`,
+    `stroke-width="${n(obj.strokeWidth)}"`,
+    `opacity="${n(obj.opacity)}"`,
+  ];
+  if (obj.dash.length > 0) {
+    attrs.push(`stroke-dasharray="${obj.dash.map(n).join(' ')}"`);
+  }
+  if (obj.rotation !== 0) {
+    attrs.push(`transform="rotate(${n(obj.rotation)} ${n(obj.x)} ${n(obj.y)})"`);
+  }
+  return `  <polyline ${attrs.join(' ')} />`;
+}
+
+function renderImage(obj: ImageObject): string {
+  // For SVG blob URLs, we can reference them. In a full implementation,
+  // we'd inline the SVG content by fetching the blob URL.
+  // For now, embed as <image> with href.
+  const attrs = [
+    `x="${n(obj.x)}"`,
+    `y="${n(obj.y)}"`,
+    `width="${n(obj.width)}"`,
+    `height="${n(obj.height)}"`,
+    `href="${escapeXml(obj.src)}"`,
+    `opacity="${n(obj.opacity)}"`,
+  ];
+  if (obj.rotation !== 0) {
+    const cx = obj.x + obj.width / 2;
+    const cy = obj.y + obj.height / 2;
+    attrs.push(`transform="rotate(${n(obj.rotation)} ${n(cx)} ${n(cy)})"`);
+  }
+  return `  <image ${attrs.join(' ')} />`;
+}
+
+/**
+ * Render a single canvas object to an SVG element string.
+ * Returns null for objects that cannot be rendered (text, hidden, raster images).
+ */
+function renderObject(obj: CanvasObject): string | null {
+  if (!obj.visible) return null;
+
+  switch (obj.type) {
+    case 'rect':
+      return renderRect(obj);
+    case 'circle':
+      return renderCircle(obj);
+    case 'ellipse':
+      return renderEllipse(obj);
+    case 'line':
+      return renderLine(obj);
+    case 'image': {
+      // Skip raster images — only SVG images are meaningful for vector export
+      const isSvgSrc =
+        obj.src.includes('image/svg+xml') || obj.src.endsWith('.svg');
+      if (!isSvgSrc) return null;
+      return renderImage(obj);
+    }
+    case 'text':
+      // Text objects should have been converted to paths. Skip in SVG composition.
+      return null;
+    default:
+      return null;
+  }
+}
+
+/**
+ * Compose visible canvas objects into an SVG string with correct coordinate
+ * space and real-world unit dimensions.
+ *
+ * - viewBox matches artboard dimensions in pixels
+ * - width/height attributes use real-world units (e.g. `width="4in"`)
+ * - Objects with `visible: false` are skipped
+ * - TextObject and raster ImageObject are skipped
+ */
+export function composeCanvasSVG(
+  objects: CanvasObject[],
+  artboard: ArtboardConfig,
+): string {
+  const pxW = toPx(artboard.width, artboard.unit);
+  const pxH = toPx(artboard.height, artboard.unit);
+
+  // Real-world unit suffix for width/height attributes
+  const unitSuffix = artboard.unit === 'inches' ? 'in' : 'mm';
+  const realW = `${n(artboard.width)}${unitSuffix}`;
+  const realH = `${n(artboard.height)}${unitSuffix}`;
+
+  const elements = objects
+    .map(renderObject)
+    .filter((el): el is string => el !== null);
+
+  const lines = [
+    `<svg xmlns="http://www.w3.org/2000/svg" viewBox="0 0 ${n(pxW)} ${n(pxH)}" width="${realW}" height="${realH}">`,
+    ...elements,
+    '</svg>',
+  ];
+
+  return lines.join('\n');
+}
+
+// -- Download Trigger ---------------------------------------------------------
+
+/**
+ * Trigger a browser file download from a Blob.
+ *
+ * Creates a hidden anchor element with a blob URL, clicks it to start the
+ * download, then cleans up the DOM element and revokes the blob URL.
+ */
+export function triggerDownload(blob: Blob, filename: string): void {
+  const url = URL.createObjectURL(blob);
+  const a = document.createElement('a');
+  a.href = url;
+  a.download = filename;
+  a.style.display = 'none';
+  document.body.appendChild(a);
+  a.click();
+  // Clean up after a short delay to ensure the download starts
+  setTimeout(() => {
+    document.body.removeChild(a);
+    URL.revokeObjectURL(url);
+  }, 100);
+}
diff --git a/app/src/views/ImportConvert.tsx b/app/src/views/ImportConvert.tsx
index 5d3c0d1..121a7bf 100644
--- a/app/src/views/ImportConvert.tsx
+++ b/app/src/views/ImportConvert.tsx
@@ -34,7 +34,7 @@ function defaultParamsFromPreset(config: PresetConfig): Record<string, unknown>
 
 export default function ImportConvert({ onUseThis }: ImportConvertProps) {
   const [selectedFile, setSelectedFile] = useState<File | null>(null);
-  const [isSvgMode, setIsSvgMode] = useState(false);
+  const [_isSvgMode, setIsSvgMode] = useState(false);
   const [selectedPreset, setSelectedPreset] = useState('sign');
   const [presetConfig, setPresetConfig] = useState<PresetConfig | null>(null);
   const [currentParams, setCurrentParams] = useState<Record<string, unknown>>({
diff --git a/app/vite.config.ts b/app/vite.config.ts
index d39af25..dcaca3c 100644
--- a/app/vite.config.ts
+++ b/app/vite.config.ts
@@ -1,4 +1,4 @@
-/// <reference types="vitest" />
+/// <reference types="vitest/config" />
 import { defineConfig } from 'vite'
 import react from '@vitejs/plugin-react'