diff --git a/packages/core/src/editor.js b/packages/core/src/editor.js
index 236e459..2997bc0 100644
--- a/packages/core/src/editor.js
+++ b/packages/core/src/editor.js
@@ -8,6 +8,7 @@ import { themeOf, SIZES, FONT_SIZES, FONTS, GEO_IDS, COLOR_IDS, GRID_IDS, GRID_S
 import {
   localBounds, pageBounds, toLocal, drawShape, hitShape, marqueeHits,
   scaleShape, textLayout, noteLayout, NOTE_W, sampleLinePts, resetTextLayouts,
+  sortShapesForRender,
 } from './shapes.js'
 import { boundsUnion, boundsExpand, boundsContain, clamp, rotWith } from './geometry.js'
 
@@ -463,14 +464,8 @@ export class Editor {
   }
 
   shapesSorted() {
-    // highlighter lives under the ink, like on paper — highlights render
-    // first (in their own z order), everything else above
-    return this.store.shapes().sort(
-      (a, b) =>
-        (a.type === 'highlight' ? 0 : 1) - (b.type === 'highlight' ? 0 : 1) ||
-        a.z - b.z ||
-        (a.id < b.id ? -1 : 1)
-    )
+    // order lives in shapes.js so out-of-tree exporters render identically
+    return sortShapesForRender(this.store.shapes())
   }
   hitTest(px, py) {
     const tol = 8 / this.camera.z
diff --git a/packages/core/src/index.js b/packages/core/src/index.js
index 79a44f7..2f41948 100644
--- a/packages/core/src/index.js
+++ b/packages/core/src/index.js
@@ -9,7 +9,9 @@ export {
   themeOf, THEMES, COLOR_IDS, SIZE_IDS, DASH_IDS, FILL_IDS, GEO_IDS, GRID_IDS,
   SIZES, FONT_SIZES, FONTS,
 } from './palette.js'
-export { pageBounds, localBounds, drawShape, hitShape } from './shapes.js'
+export { pageBounds, localBounds, drawShape, hitShape, textLayout, noteLayout } from './shapes.js'
+export { boundsUnion, boundsExpand } from './geometry.js'
+export { sortShapesForRender, setShapePlatform, resetShapePlatform } from './shapes.js'
 export { strokeOutline, inkOptions } from './freehand.js'
 
 import { Editor } from './editor.js'
diff --git a/packages/core/src/shapes.js b/packages/core/src/shapes.js
index 2fb5ed0..b4d9da8 100644
--- a/packages/core/src/shapes.js
+++ b/packages/core/src/shapes.js
@@ -15,6 +15,42 @@ import {
 } from './geometry.js'
 import { strokeOutline, inkOptions } from './freehand.js'
 
+// ---- rendering platform -----------------------------------------------------
+// The engine draws with the browser's canvas stack by default (global Path2D,
+// OffscreenCanvas/document canvases, Image, canvas text measurement).
+// Non-browser renderers (e.g. a server-side exporter) inject native
+// equivalents explicitly via setShapePlatform() — never by patching
+// window/document/Path2D/Image, which this module does not touch. The
+// browser never calls setShapePlatform, so its path is unchanged. Only
+// stateless backend pieces live here (a Path2D class, a shared measure
+// context, a tile-canvas factory); per-render state such as decoded images
+// and hatch patterns travels on drawShape's opts.
+const shapePlatform = { Path2D: null, measureCtx: null, tileCanvas: null }
+export function setShapePlatform(p = {}) {
+  if (p.Path2D !== undefined) shapePlatform.Path2D = p.Path2D
+  if (p.measureCtx !== undefined) shapePlatform.measureCtx = p.measureCtx
+  if (p.tileCanvas !== undefined) shapePlatform.tileCanvas = p.tileCanvas
+  return shapePlatform
+}
+export function resetShapePlatform() {
+  shapePlatform.Path2D = null
+  shapePlatform.measureCtx = null
+  shapePlatform.tileCanvas = null
+}
+// Per-call opts win, then the injected platform, then the browser global.
+const path2DFor = (opts) => opts?.Path2D ?? shapePlatform.Path2D ?? globalThis.Path2D
+
+// Render order, shared by the editor and out-of-tree exporters so they cannot
+// drift: highlighters soak into the paper beneath the ink, like on a real
+// page — highlights render first (in their own z order), everything else
+// above, ties broken by id.
+export const sortShapesForRender = (shapes) => [...shapes].sort(
+  (a, b) =>
+    (a.type === 'highlight' ? 0 : 1) - (b.type === 'highlight' ? 0 : 1) ||
+    a.z - b.z ||
+    (a.id < b.id ? -1 : 1),
+)
+
 export const NOTE_W = 200
 const NOTE_PAD = 20
 const LABEL_PAD = 12
@@ -99,6 +135,7 @@ let layoutCache = new WeakMap() // text/note/geo-label props -> layout
 
 let measureCtx = null
 const measurer = () => {
+  if (shapePlatform.measureCtx) return shapePlatform.measureCtx
   if (!measureCtx) measureCtx = (typeof OffscreenCanvas !== 'undefined'
     ? new OffscreenCanvas(1, 1)
     : document.createElement('canvas')).getContext('2d')
@@ -243,12 +280,14 @@ export function geoOutline(shape) {
   return { smooth: false, pts: bowPolygon(geoPolygon(p.geo, w, h), shape.id) }
 }
 
-// polygon path (hand-drawn for 'draw' dash), cached per props object
-function geoPath(shape) {
+// polygon path (hand-drawn for 'draw' dash), cached per props object.
+// opts (drawShape's) may carry an injected Path2D for non-browser backends.
+function geoPath(shape, opts) {
   const p = shape.props
   let path = geoPathCache.get(p)
   if (path) return path
-  path = new Path2D()
+  const P2D = path2DFor(opts)
+  path = new P2D()
   if (p.dash === 'draw') {
     const { smooth, pts } = geoOutline(shape)
     if (smooth) traceSmooth(path, pts, true)
@@ -277,13 +316,17 @@ function geoPath(shape) {
   return path
 }
 
-const patternCache = new Map() // `${color}|${theme}` -> CanvasPattern
-function hatchPattern(ctx, colorHex, themeId) {
+const patternCache = new Map() // `${color}|${theme}` -> CanvasPattern (browser default)
+function hatchPattern(ctx, colorHex, themeId, opts) {
+  const cache = opts?.patternCache ?? patternCache
   const key = colorHex + '|' + themeId
-  let pat = patternCache.get(key)
+  let pat = cache.get(key)
   if (pat) return pat
-  const c = document.createElement('canvas')
-  c.width = c.height = 8
+  const c = shapePlatform.tileCanvas
+    ? shapePlatform.tileCanvas(8, 8)
+    : (typeof OffscreenCanvas !== 'undefined'
+      ? new OffscreenCanvas(8, 8)
+      : (() => { const el = document.createElement('canvas'); el.width = el.height = 8; return el })())
   const pctx = c.getContext('2d')
   pctx.strokeStyle = colorHex
   pctx.globalAlpha = 0.55
@@ -294,14 +337,14 @@ function hatchPattern(ctx, colorHex, themeId) {
   pctx.moveTo(2, 10); pctx.lineTo(10, 2)
   pctx.stroke()
   pat = ctx.createPattern(c, 'repeat')
-  patternCache.set(key, pat)
+  cache.set(key, pat)
   return pat
 }
 
-function fillPath(ctx, path, p, theme) {
+function fillPath(ctx, path, p, theme, opts) {
   if (!p.fill || p.fill === 'none') return
   if (p.fill === 'semi') ctx.fillStyle = SEMI[theme.id]
-  else if (p.fill === 'pattern') ctx.fillStyle = hatchPattern(ctx, theme.colors[p.color].stroke, theme.id)
+  else if (p.fill === 'pattern') ctx.fillStyle = hatchPattern(ctx, theme.colors[p.color].stroke, theme.id, opts)
   else ctx.fillStyle = theme.colors[p.color].fill
   ctx.fill(path)
 }
@@ -321,13 +364,13 @@ function drawLabel(ctx, layout, color, w, h) {
 
 // the freehand outline as a Path2D, cached; live strokes (done !== true)
 // rebuild every frame so the ink grows under the pen
-function drawPath(shape) {
+function drawPath(shape, opts) {
   const p = shape.props
   if (p.done) {
     const hit = outlineCache.get(p)
     if (hit) return hit
   }
-  const path = new Path2D()
+  const path = new (path2DFor(opts))()
   const outline = strokeOutline(p.pts, inkOptions(INK_SIZES[p.size], { isPen: !!p.isPen, done: !!p.done }))
   traceSmooth(path, outline, true)
   path.closePath()
@@ -343,7 +386,9 @@ function inkReach(size) {
 
 // Draw one shape. ctx is already in PAGE space (camera applied by caller);
 // this applies the shape's own translate/rotate.
-// opts: { theme, store, zoom, onAssetLoad, ghost }
+// opts: { theme, store, zoom, onAssetLoad, ghost, hideText,
+//         Path2D (injected path class), images (Map assetId -> decoded image,
+//         when present the browser loader is bypassed), patternCache (Map) }
 export function drawShape(ctx, shape, opts) {
   const { theme } = opts
   const p = shape.props
@@ -377,7 +422,7 @@ export function drawShape(ctx, shape, opts) {
         ctx.setLineDash([])
       } else {
         ctx.fillStyle = col.stroke
-        ctx.fill(drawPath(shape))
+        ctx.fill(drawPath(shape, opts))
       }
       break
     }
@@ -398,8 +443,8 @@ export function drawShape(ctx, shape, opts) {
       break
     }
     case 'geo': {
-      const path = geoPath(shape)
-      fillPath(ctx, path, p, theme)
+      const path = geoPath(shape, opts)
+      fillPath(ctx, path, p, theme, opts)
       ctx.strokeStyle = col.stroke
       strokeStyled(ctx, p.dash, SIZES[p.size])
       ctx.stroke(path)
@@ -484,7 +529,11 @@ export function drawShape(ctx, shape, opts) {
       break
     }
     case 'image': {
-      const img = assetImage(opts.store, p.assetId, opts.onAssetLoad)
+      // Non-browser renderers pass opts.images (pre-decoded per render) and
+      // never touch the browser loader; the browser passes no images map.
+      const img = opts.images
+        ? (opts.images.get(p.assetId) ?? null)
+        : assetImage(opts.store, p.assetId, opts.onAssetLoad)
       if (img) {
         ctx.beginPath()
         ctx.roundRect(0, 0, p.w, p.h, 4)
diff --git a/packages/core/test/platform.test.js b/packages/core/test/platform.test.js
new file mode 100644
index 0000000..f36a280
--- /dev/null
+++ b/packages/core/test/platform.test.js
@@ -0,0 +1,109 @@
+// @vitest-environment jsdom
+// The rendering seam: explicit backend injection for non-browser renderers.
+// These tests pass fakes through opts / setShapePlatform and assert the
+// fakes (not browser globals) are what the engine uses.
+import { describe, it, expect, afterEach } from 'vitest'
+import {
+  drawShape, textLayout, resetTextLayouts,
+  setShapePlatform, resetShapePlatform, sortShapesForRender,
+} from '../src/shapes.js'
+import { themeOf } from '../src/palette.js'
+import { Store } from '../src/store.js'
+
+const theme = themeOf('light')
+const store = new Store()
+
+afterEach(() => {
+  resetShapePlatform()
+  resetTextLayouts()
+})
+
+// minimal 2d context: records calls, returns canned values
+const stubCtx = () => {
+  const calls = []
+  const ctx = new Proxy({
+    canvas: {},
+    measureText: () => ({ width: 10, fontBoundingBoxAscent: 8, fontBoundingBoxDescent: 2 }),
+    createPattern: () => ({ token: 'pattern' }),
+    get fillStyle() { return this._fillStyle },
+    set fillStyle(v) { this._fillStyle = v },
+  }, {
+    get(t, k) {
+      if (k in t) return t[k]
+      return (...a) => { calls.push([k, a]); return undefined }
+    },
+    set(t, k, v) { t[k] = v; return true },
+  })
+  return { ctx, calls }
+}
+
+class FakePath {
+  constructor() { FakePath.constructed++ }
+  moveTo() {}
+  lineTo() {}
+  quadraticCurveTo() {}
+  bezierCurveTo() {}
+  ellipse() {}
+  closePath() {}
+}
+FakePath.constructed = 0
+
+describe('platform injection', () => {
+  it('drawShape builds geo paths with the injected Path2D class', () => {
+    FakePath.constructed = 0
+    const { ctx } = stubCtx()
+    drawShape(ctx, {
+      id: 'g', typeName: 'shape', type: 'geo', x: 0, y: 0, rot: 0, z: 1,
+      props: { geo: 'rectangle', w: 10, h: 10, color: 'black', size: 'm', dash: 'solid', fill: 'none' },
+    }, { theme, store, Path2D: FakePath, patternCache: new Map() })
+    expect(FakePath.constructed).toBeGreaterThan(0)
+  })
+
+  it('pattern fills use the per-render cache, not the shared one', () => {
+    const { ctx } = stubCtx()
+    const mine = new Map()
+    const shape = {
+      id: 'g', typeName: 'shape', type: 'geo', x: 0, y: 0, rot: 0, z: 1,
+      props: { geo: 'rectangle', w: 10, h: 10, color: 'black', size: 'm', dash: 'solid', fill: 'pattern' },
+    }
+    drawShape(ctx, shape, { theme, store, Path2D: FakePath, patternCache: mine })
+    expect(mine.size).toBe(1)
+    expect(ctx.fillStyle).toEqual({ token: 'pattern' })
+  })
+
+  it('image shapes draw from opts.images without touching the browser loader', () => {
+    const seen = []
+    const ctx = stubCtx().ctx
+    ctx.drawImage = (...a) => seen.push(a)
+    ctx.clip = () => {}
+    ctx.roundRect = () => {}
+    const decoded = { fake: 'bitmap' }
+    drawShape(ctx, {
+      id: 'i', typeName: 'shape', type: 'image', x: 0, y: 0, rot: 0, z: 1,
+      props: { w: 40, h: 30, assetId: 'asset:missing-from-store' },
+    }, { theme, store, images: new Map([['asset:missing-from-store', decoded]]) })
+    // asset is absent from the store, yet the pre-decoded bitmap draws:
+    // the loader (and its placeholder) is fully bypassed
+    expect(seen).toEqual([[decoded, 0, 0, 40, 30]])
+  })
+
+  it('text layout measures with the injected context', () => {
+    const measured = []
+    setShapePlatform({
+      measureCtx: { font: '', measureText: (t) => { measured.push(t); return { width: t.length * 7 } } },
+    })
+    const l = textLayout({
+      id: 't', typeName: 'shape', type: 'text', x: 0, y: 0, rot: 0, z: 1,
+      props: { text: 'hello', size: 'm', color: 'black', font: 'draw' },
+    })
+    expect(measured.length).toBeGreaterThan(0)
+    expect(l.w).toBeGreaterThan(0)
+  })
+
+  it('sortShapesForRender keeps highlighters beneath, z-ordered within groups', () => {
+    const s = (id, type, z) => ({ id, typeName: 'shape', type, x: 0, y: 0, rot: 0, z, props: {} })
+    expect(sortShapesForRender([
+      s('geo-hi', 'geo', 99), s('hl-lo', 'highlight', 1), s('img', 'image', 50),
+    ]).map((x) => x.id)).toEqual(['hl-lo', 'img', 'geo-hi'])
+  })
+})
diff --git a/packages/core/types/index.d.ts b/packages/core/types/index.d.ts
index f283c44..2e7d336 100644
--- a/packages/core/types/index.d.ts
+++ b/packages/core/types/index.d.ts
@@ -145,8 +145,23 @@ export function pageBounds(shape: ShapeRecord): Bounds
 export function drawShape(
   ctx: CanvasRenderingContext2D,
   shape: ShapeRecord,
-  opts: { theme: Theme; store: Store; zoom?: number; ghost?: boolean; onAssetLoad?: () => void }
+  opts: {
+    theme: Theme; store: Store; zoom?: number; ghost?: boolean; onAssetLoad?: () => void;
+    hideText?: string | null;
+    Path2D?: new () => Path2D;
+    images?: Map<string, CanvasImageSource | null>;
+    patternCache?: Map<string, CanvasPattern | null>;
+  }
 ): void
+/** Render order: highlighters first (each group by z, ties by id). */
+export function sortShapesForRender(shapes: ShapeRecord[]): ShapeRecord[]
+/**
+ * Inject a non-browser rendering backend (Node/Skia). Never patches
+ * window/document globals; the browser never calls this.
+ */
+export function setShapePlatform(p: { Path2D?: any; measureCtx?: any; tileCanvas?: ((w: number, h: number) => any) | null }): unknown
+/** Clear a backend previously installed with setShapePlatform. */
+export function resetShapePlatform(): void
 /** Point hit-test in page space. */
 export function hitShape(shape: ShapeRecord, px: number, py: number, tol: number, store: Store): boolean