feat(canvas): move image pipeline rendering off main thread with worker fallback

components/canvas/nodes/render-node.tsx

@@ -16,7 +16,10 @@ import { resolveRenderPreviewInput } from "@/lib/canvas-render-preview";
 import { resolveMediaAspectRatio } from "@/lib/canvas-utils";
 import { parseAspectRatioString } from "@/lib/image-formats";
 import { getSourceImage, hashPipeline } from "@/lib/image-pipeline/contracts";
-import { bridge } from "@/lib/image-pipeline/bridge";
+import {
+  isPipelineAbortError,
+  renderFullWithWorkerFallback,
+} from "@/lib/image-pipeline/worker-client";
 import type { Id } from "@/convex/_generated/dataModel";
 import { Dialog, DialogContent, DialogTitle } from "@/components/ui/dialog";
 
@@ -441,10 +444,18 @@ export default function RenderNode({ id, data, selected, width, height }: NodePr
 
   const localDataRef = useRef(localData);
   const renderRunIdRef = useRef(0);
+  const renderAbortControllerRef = useRef<AbortController | null>(null);
   const menuButtonRef = useRef<HTMLButtonElement | null>(null);
   const menuPanelRef = useRef<HTMLDivElement | null>(null);
   const lastAppliedAspectRatioRef = useRef<number | null>(null);
 
+  useEffect(() => {
+    return () => {
+      renderAbortControllerRef.current?.abort();
+      renderAbortControllerRef.current = null;
+    };
+  }, []);
+
   useEffect(() => {
     localDataRef.current = localData;
   }, [localData]);
@@ -763,6 +774,9 @@ export default function RenderNode({ id, data, selected, width, height }: NodePr
 
     renderRunIdRef.current += 1;
     const runId = renderRunIdRef.current;
+    renderAbortControllerRef.current?.abort();
+    const abortController = new AbortController();
+    renderAbortControllerRef.current = abortController;
     setIsRendering(true);
 
     try {
@@ -778,7 +792,7 @@ export default function RenderNode({ id, data, selected, width, height }: NodePr
         jpegQuality: activeData.format === "jpeg" ? activeData.jpegQuality : null,
       });
 
-      const renderResult = await bridge.renderFull({
+      const renderResult = await renderFullWithWorkerFallback({
         sourceUrl,
         steps,
         render: {
@@ -796,6 +810,7 @@ export default function RenderNode({ id, data, selected, width, height }: NodePr
           jpegQuality:
             activeData.format === "jpeg" ? activeData.jpegQuality / 100 : undefined,
         },
+        signal: abortController.signal,
       });
 
       if (runId !== renderRunIdRef.current) return;
@@ -928,6 +943,9 @@ export default function RenderNode({ id, data, selected, width, height }: NodePr
       }
     } catch (error: unknown) {
       if (runId !== renderRunIdRef.current) return;
+      if (isPipelineAbortError(error)) {
+        return;
+      }
 
       const message = error instanceof Error ? error.message : "Render failed";
       logRenderDebug("render-error", {
@@ -944,6 +962,9 @@ export default function RenderNode({ id, data, selected, width, height }: NodePr
       await persistImmediately(next);
     } finally {
       if (runId === renderRunIdRef.current) {
+        if (renderAbortControllerRef.current === abortController) {
+          renderAbortControllerRef.current = null;
+        }
         setIsRendering(false);
       }
     }

hooks/use-pipeline-preview.ts

@@ -5,9 +5,10 @@ import { useEffect, useMemo, useRef, useState } from "react";
 import { hashPipeline, type PipelineStep } from "@/lib/image-pipeline/contracts";
 import { emptyHistogram, type HistogramData } from "@/lib/image-pipeline/histogram";
 import {
-  renderPreview,
+  isPipelineAbortError,
+  renderPreviewWithWorkerFallback,
   type PreviewRenderResult,
-} from "@/lib/image-pipeline/preview-renderer";
+} from "@/lib/image-pipeline/worker-client";
 
 type UsePipelinePreviewOptions = {
   sourceUrl: string | null;
@@ -78,14 +79,16 @@ export function usePipelinePreview(options: UsePipelinePreviewOptions): {
 
     const currentRun = runIdRef.current + 1;
     runIdRef.current = currentRun;
+    const abortController = new AbortController();
 
     const timer = window.setTimeout(() => {
       setIsRendering(true);
       setError(null);
-      void renderPreview({
+      void renderPreviewWithWorkerFallback({
         sourceUrl,
         steps: options.steps,
         previewWidth,
+        signal: abortController.signal,
       })
         .then((result: PreviewRenderResult) => {
           if (runIdRef.current !== currentRun) return;
@@ -105,6 +108,8 @@ export function usePipelinePreview(options: UsePipelinePreviewOptions): {
         })
         .catch((renderError: unknown) => {
           if (runIdRef.current !== currentRun) return;
+          if (isPipelineAbortError(renderError)) return;
+
           const message =
             renderError instanceof Error
               ? renderError.message
@@ -119,6 +124,7 @@ export function usePipelinePreview(options: UsePipelinePreviewOptions): {
 
     return () => {
       window.clearTimeout(timer);
+      abortController.abort();
     };
   }, [options.sourceUrl, options.steps, pipelineHash, previewWidth]);
 

lib/image-pipeline/bridge.ts

@@ -93,7 +93,9 @@ function resolveMimeType(format: RenderFormat): string {
 }
 
 export async function renderFull(options: RenderFullOptions): Promise<RenderFullResult> {
-  const bitmap = await loadSourceBitmap(options.sourceUrl);
+  const { signal } = options;
+
+  const bitmap = await loadSourceBitmap(options.sourceUrl, { signal });
   const resolvedSize = resolveRenderSize({
     sourceWidth: bitmap.width,
     sourceHeight: bitmap.height,
@@ -111,7 +113,15 @@ export async function renderFull(options: RenderFullOptions): Promise<RenderFull
     options.steps,
     resolvedSize.width,
     resolvedSize.height,
+    {
+      shouldAbort: () => Boolean(signal?.aborted),
+    },
   );
+
+  if (signal?.aborted) {
+    throw new DOMException("The operation was aborted.", "AbortError");
+  }
+
   context.putImageData(imageData, 0, 0);
 
   const mimeType = resolveMimeType(options.render.format);

lib/image-pipeline/image-pipeline.worker.ts

@@ -0,0 +1,166 @@
+import { renderFull } from "@/lib/image-pipeline/bridge";
+import { renderPreview } from "@/lib/image-pipeline/preview-renderer";
+import type { PipelineStep } from "@/lib/image-pipeline/contracts";
+import type { HistogramData } from "@/lib/image-pipeline/histogram";
+import type { RenderFullOptions, RenderFullResult } from "@/lib/image-pipeline/render-types";
+
+type PreviewWorkerPayload = {
+  sourceUrl: string;
+  steps: readonly PipelineStep[];
+  previewWidth: number;
+};
+
+type WorkerRequestMessage =
+  | {
+      kind: "preview";
+      requestId: number;
+      payload: PreviewWorkerPayload;
+    }
+  | {
+      kind: "full";
+      requestId: number;
+      payload: RenderFullOptions;
+    }
+  | {
+      kind: "cancel";
+      requestId: number;
+    };
+
+type WorkerResultPreviewPayload = {
+  width: number;
+  height: number;
+  histogram: HistogramData;
+  pixels: ArrayBuffer;
+};
+
+type WorkerResponseMessage =
+  | {
+      kind: "preview-result";
+      requestId: number;
+      payload: WorkerResultPreviewPayload;
+    }
+  | {
+      kind: "full-result";
+      requestId: number;
+      payload: RenderFullResult;
+    }
+  | {
+      kind: "error";
+      requestId: number;
+      payload: {
+        name: string;
+        message: string;
+      };
+    };
+
+type WorkerScope = {
+  postMessage: (message: WorkerResponseMessage, transfer?: Transferable[]) => void;
+  onmessage: ((event: MessageEvent<WorkerRequestMessage>) => void) | null;
+};
+
+const workerScope = self as unknown as WorkerScope;
+const runningControllers = new Map<number, AbortController>();
+
+function postMessageSafe(message: WorkerResponseMessage, transfer?: Transferable[]): void {
+  if (transfer) {
+    workerScope.postMessage(message, transfer);
+    return;
+  }
+
+  workerScope.postMessage(message);
+}
+
+function normalizeErrorPayload(error: unknown): { name: string; message: string } {
+  if (error instanceof Error) {
+    return {
+      name: error.name,
+      message: error.message,
+    };
+  }
+
+  return {
+    name: "Error",
+    message: "Image pipeline worker failed",
+  };
+}
+
+async function handlePreviewRequest(requestId: number, payload: PreviewWorkerPayload): Promise<void> {
+  const controller = new AbortController();
+  runningControllers.set(requestId, controller);
+
+  try {
+    const result = await renderPreview({
+      sourceUrl: payload.sourceUrl,
+      steps: payload.steps,
+      previewWidth: payload.previewWidth,
+      signal: controller.signal,
+    });
+
+    const pixels = result.imageData.data.buffer;
+    postMessageSafe(
+      {
+        kind: "preview-result",
+        requestId,
+        payload: {
+          width: result.width,
+          height: result.height,
+          histogram: result.histogram,
+          pixels,
+        },
+      },
+      [pixels],
+    );
+  } catch (error: unknown) {
+    postMessageSafe({
+      kind: "error",
+      requestId,
+      payload: normalizeErrorPayload(error),
+    });
+  } finally {
+    runningControllers.delete(requestId);
+  }
+}
+
+async function handleFullRequest(requestId: number, payload: RenderFullOptions): Promise<void> {
+  const controller = new AbortController();
+  runningControllers.set(requestId, controller);
+
+  try {
+    const result = await renderFull({
+      ...payload,
+      signal: controller.signal,
+    });
+
+    postMessageSafe({
+      kind: "full-result",
+      requestId,
+      payload: result,
+    });
+  } catch (error: unknown) {
+    postMessageSafe({
+      kind: "error",
+      requestId,
+      payload: normalizeErrorPayload(error),
+    });
+  } finally {
+    runningControllers.delete(requestId);
+  }
+}
+
+workerScope.onmessage = (event: MessageEvent<WorkerRequestMessage>) => {
+  const message = event.data;
+
+  if (message.kind === "cancel") {
+    runningControllers.get(message.requestId)?.abort();
+    return;
+  }
+
+  if (message.kind === "preview") {
+    void handlePreviewRequest(message.requestId, message.payload);
+    return;
+  }
+
+  void handleFullRequest(message.requestId, message.payload);
+};
+
+export {};

lib/image-pipeline/preview-renderer.ts

@@ -10,31 +10,76 @@ export type PreviewRenderResult = {
   histogram: HistogramData;
 };
 
+type PreviewCanvas = HTMLCanvasElement | OffscreenCanvas;
+type PreviewContext = CanvasRenderingContext2D | OffscreenCanvasRenderingContext2D;
+
+function createPreviewContext(width: number, height: number): PreviewContext {
+  if (typeof document !== "undefined") {
+    const canvas = document.createElement("canvas");
+    canvas.width = width;
+    canvas.height = height;
+    const context = canvas.getContext("2d", { willReadFrequently: true });
+    if (!context) {
+      throw new Error("Preview renderer could not create 2D context.");
+    }
+
+    return context;
+  }
+
+  if (typeof OffscreenCanvas !== "undefined") {
+    const canvas: PreviewCanvas = new OffscreenCanvas(width, height);
+    const context = canvas.getContext("2d", { willReadFrequently: true });
+    if (!context) {
+      throw new Error("Preview renderer could not create offscreen 2D context.");
+    }
+
+    return context;
+  }
+
+  throw new Error("Preview rendering is not available in this environment.");
+}
+
+async function yieldToMainOrWorkerLoop(): Promise<void> {
+  await new Promise<void>((resolve) => {
+    if (typeof requestAnimationFrame === "function") {
+      requestAnimationFrame(() => resolve());
+      return;
+    }
+
+    setTimeout(() => resolve(), 0);
+  });
+}
+
 export async function renderPreview(options: {
   sourceUrl: string;
   steps: readonly PipelineStep[];
   previewWidth: number;
+  signal?: AbortSignal;
 }): Promise<PreviewRenderResult> {
-  const bitmap = await loadSourceBitmap(options.sourceUrl);
+  const bitmap = await loadSourceBitmap(options.sourceUrl, {
+    signal: options.signal,
+  });
   const width = Math.max(1, Math.round(options.previewWidth));
   const height = Math.max(1, Math.round((bitmap.height / bitmap.width) * width));
 
-  const canvas = document.createElement("canvas");
-  canvas.width = width;
-  canvas.height = height;
-  const context = canvas.getContext("2d", { willReadFrequently: true });
-  if (!context) {
-    throw new Error("Preview renderer could not create 2D context.");
+  if (options.signal?.aborted) {
+    throw new DOMException("The operation was aborted.", "AbortError");
   }
 
+  const context = createPreviewContext(width, height);
+
   context.drawImage(bitmap, 0, 0, width, height);
   const imageData = context.getImageData(0, 0, width, height);
 
   for (let index = 0; index < options.steps.length; index += 1) {
-    applyPipelineStep(imageData.data, options.steps[index]!, width, height);
-    await new Promise<void>((resolve) => {
-      requestAnimationFrame(() => resolve());
+    applyPipelineStep(imageData.data, options.steps[index]!, width, height, {
+      shouldAbort: () => Boolean(options.signal?.aborted),
     });
+    await yieldToMainOrWorkerLoop();
+
+    if (options.signal?.aborted) {
+      throw new DOMException("The operation was aborted.", "AbortError");
+    }
   }
 
   const histogram = computeHistogram(imageData.data);

lib/image-pipeline/render-core.ts

@@ -7,6 +7,20 @@ import {
   type CurvePoint,
 } from "@/lib/image-pipeline/adjustment-types";
 
+type PipelineExecutionOptions = {
+  shouldAbort?: () => boolean;
+};
+
+function throwIfAborted(options: PipelineExecutionOptions | undefined): void {
+  if (options?.shouldAbort?.()) {
+    throw new DOMException("The operation was aborted.", "AbortError");
+  }
+}
+
+function shouldCheckAbort(index: number): boolean {
+  return index % 4096 === 0;
+}
+
 function clamp(value: number, min: number, max: number): number {
   return Math.max(min, Math.min(max, value));
 }
@@ -100,7 +114,11 @@ function hslToRgb(h: number, s: number, l: number): { r: number; g: number; b: n
   };
 }
 
-function applyCurves(pixels: Uint8ClampedArray, params: unknown): void {
+function applyCurves(
+  pixels: Uint8ClampedArray,
+  params: unknown,
+  options?: PipelineExecutionOptions,
+): void {
   const curves = normalizeCurvesData(params);
   const rgbLut = buildLut(curves.points.rgb);
   const redLut = buildLut(curves.points.red);
@@ -112,6 +130,10 @@ function applyCurves(pixels: Uint8ClampedArray, params: unknown): void {
   const invGamma = 1 / curves.levels.gamma;
 
   for (let index = 0; index < pixels.length; index += 4) {
+    if (shouldCheckAbort(index)) {
+      throwIfAborted(options);
+    }
+
     const applyLevels = (value: number) => {
       const normalized = clamp((value - curves.levels.blackPoint) / levelRange, 0, 1);
       return toByte(Math.pow(normalized, invGamma) * 255);
@@ -143,13 +165,21 @@ function applyCurves(pixels: Uint8ClampedArray, params: unknown): void {
   }
 }
 
-function applyColorAdjust(pixels: Uint8ClampedArray, params: unknown): void {
+function applyColorAdjust(
+  pixels: Uint8ClampedArray,
+  params: unknown,
+  options?: PipelineExecutionOptions,
+): void {
   const color = normalizeColorAdjustData(params);
   const saturationFactor = 1 + color.hsl.saturation / 100;
   const luminanceShift = color.hsl.luminance / 100;
   const hueShift = color.hsl.hue;
 
   for (let index = 0; index < pixels.length; index += 4) {
+    if (shouldCheckAbort(index)) {
+      throwIfAborted(options);
+    }
+
     const currentRed = pixels[index] ?? 0;
     const currentGreen = pixels[index + 1] ?? 0;
     const currentBlue = pixels[index + 2] ?? 0;
@@ -180,6 +210,7 @@ function applyLightAdjust(
   params: unknown,
   width: number,
   height: number,
+  options?: PipelineExecutionOptions,
 ): void {
   const light = normalizeLightAdjustData(params);
   const exposureFactor = Math.pow(2, light.exposure / 2);
@@ -190,6 +221,10 @@ function applyLightAdjust(
   const centerY = height / 2;
 
   for (let y = 0; y < height; y += 1) {
+    if (y % 64 === 0) {
+      throwIfAborted(options);
+    }
+
     for (let x = 0; x < width; x += 1) {
       const index = (y * width + x) * 4;
       let red = pixels[index] ?? 0;
@@ -238,7 +273,11 @@ function pseudoNoise(seed: number): number {
   return x - Math.floor(x);
 }
 
-function applyDetailAdjust(pixels: Uint8ClampedArray, params: unknown): void {
+function applyDetailAdjust(
+  pixels: Uint8ClampedArray,
+  params: unknown,
+  options?: PipelineExecutionOptions,
+): void {
   const detail = normalizeDetailAdjustData(params);
   const sharpenBoost = detail.sharpen.amount / 500;
   const clarityBoost = detail.clarity / 100;
@@ -248,6 +287,10 @@ function applyDetailAdjust(pixels: Uint8ClampedArray, params: unknown): void {
   const grainScale = Math.max(0.5, detail.grain.size);
 
   for (let index = 0; index < pixels.length; index += 4) {
+    if (shouldCheckAbort(index)) {
+      throwIfAborted(options);
+    }
+
     let red = pixels[index] ?? 0;
     let green = pixels[index + 1] ?? 0;
     let blue = pixels[index + 2] ?? 0;
@@ -293,21 +336,24 @@ export function applyPipelineStep(
   step: PipelineStep<string, unknown>,
   width: number,
   height: number,
+  options?: PipelineExecutionOptions,
 ): void {
+  throwIfAborted(options);
+
   if (step.type === "curves") {
-    applyCurves(pixels, step.params);
+    applyCurves(pixels, step.params, options);
     return;
   }
   if (step.type === "color-adjust") {
-    applyColorAdjust(pixels, step.params);
+    applyColorAdjust(pixels, step.params, options);
     return;
   }
   if (step.type === "light-adjust") {
-    applyLightAdjust(pixels, step.params, width, height);
+    applyLightAdjust(pixels, step.params, width, height, options);
     return;
   }
   if (step.type === "detail-adjust") {
-    applyDetailAdjust(pixels, step.params);
+    applyDetailAdjust(pixels, step.params, options);
   }
 }
 
@@ -316,8 +362,9 @@ export function applyPipelineSteps(
   steps: readonly PipelineStep[],
   width: number,
   height: number,
+  options?: PipelineExecutionOptions,
 ): void {
   for (let index = 0; index < steps.length; index += 1) {
-    applyPipelineStep(pixels, steps[index]!, width, height);
+    applyPipelineStep(pixels, steps[index]!, width, height, options);
   }
 }

lib/image-pipeline/render-types.ts

@@ -36,6 +36,7 @@ export type RenderFullOptions = {
   steps: readonly PipelineStep[];
   render: RenderOptions;
   limits?: RenderSizeLimits;
+  signal?: AbortSignal;
 };
 
 export type RenderFullResult = {

lib/image-pipeline/source-loader.ts

@@ -1,6 +1,19 @@
 const imageBitmapCache = new Map<string, Promise<ImageBitmap>>();
 
-export async function loadSourceBitmap(sourceUrl: string): Promise<ImageBitmap> {
+type LoadSourceBitmapOptions = {
+  signal?: AbortSignal;
+};
+
+function throwIfAborted(signal: AbortSignal | undefined): void {
+  if (signal?.aborted) {
+    throw new DOMException("The operation was aborted.", "AbortError");
+  }
+}
+
+export async function loadSourceBitmap(
+  sourceUrl: string,
+  options: LoadSourceBitmapOptions = {},
+): Promise<ImageBitmap> {
   if (!sourceUrl || sourceUrl.trim().length === 0) {
     throw new Error("Render sourceUrl is required.");
   }
@@ -9,6 +22,19 @@ export async function loadSourceBitmap(sourceUrl: string): Promise<ImageBitmap>
     throw new Error("ImageBitmap is not available in this environment.");
   }
 
+  throwIfAborted(options.signal);
+
+  if (options.signal) {
+    const response = await fetch(sourceUrl, { signal: options.signal });
+    if (!response.ok) {
+      throw new Error(`Render source failed: ${response.status}`);
+    }
+
+    const blob = await response.blob();
+    throwIfAborted(options.signal);
+    return await createImageBitmap(blob);
+  }
+
   const cached = imageBitmapCache.get(sourceUrl);
   if (cached) {
     return await cached;

lib/image-pipeline/worker-client.ts

@@ -0,0 +1,305 @@
+import { renderFull } from "@/lib/image-pipeline/bridge";
+import {
+  renderPreview,
+  type PreviewRenderResult,
+} from "@/lib/image-pipeline/preview-renderer";
+import type { PipelineStep } from "@/lib/image-pipeline/contracts";
+import type { HistogramData } from "@/lib/image-pipeline/histogram";
+import type { RenderFullOptions, RenderFullResult } from "@/lib/image-pipeline/render-types";
+
+export type { PreviewRenderResult };
+
+type PreviewWorkerPayload = {
+  sourceUrl: string;
+  steps: readonly PipelineStep[];
+  previewWidth: number;
+};
+
+type WorkerRequestMessage =
+  | {
+      kind: "preview";
+      requestId: number;
+      payload: PreviewWorkerPayload;
+    }
+  | {
+      kind: "full";
+      requestId: number;
+      payload: RenderFullOptions;
+    }
+  | {
+      kind: "cancel";
+      requestId: number;
+    };
+
+type WorkerResultPreviewPayload = {
+  width: number;
+  height: number;
+  histogram: HistogramData;
+  pixels: ArrayBuffer;
+};
+
+type WorkerResponseMessage =
+  | {
+      kind: "preview-result";
+      requestId: number;
+      payload: WorkerResultPreviewPayload;
+    }
+  | {
+      kind: "full-result";
+      requestId: number;
+      payload: RenderFullResult;
+    }
+  | {
+      kind: "error";
+      requestId: number;
+      payload: {
+        name: string;
+        message: string;
+      };
+    };
+
+class WorkerUnavailableError extends Error {
+  constructor(causeMessage?: string) {
+    super(causeMessage ?? "Image pipeline worker is unavailable.");
+    this.name = "WorkerUnavailableError";
+  }
+}
+
+type PendingRequest = {
+  kind: "preview" | "full";
+  resolve: (value: PreviewRenderResult | RenderFullResult) => void;
+  reject: (reason?: unknown) => void;
+};
+
+let workerInstance: Worker | null = null;
+let workerInitError: Error | null = null;
+let requestIdCounter = 0;
+const pendingRequests = new Map<number, PendingRequest>();
+
+function nextRequestId(): number {
+  requestIdCounter += 1;
+  return requestIdCounter;
+}
+
+function makeAbortError(): DOMException {
+  return new DOMException("The operation was aborted.", "AbortError");
+}
+
+function isAbortError(error: unknown): boolean {
+  if (error instanceof DOMException && error.name === "AbortError") {
+    return true;
+  }
+
+  if (error instanceof Error && error.name === "AbortError") {
+    return true;
+  }
+
+  return false;
+}
+
+function handleWorkerFailure(error: Error): void {
+  workerInitError = error;
+
+  if (workerInstance) {
+    workerInstance.terminate();
+    workerInstance = null;
+  }
+
+  for (const [requestId, pending] of pendingRequests.entries()) {
+    pending.reject(error);
+    pendingRequests.delete(requestId);
+  }
+}
+
+function getWorker(): Worker {
+  if (typeof window === "undefined" || typeof Worker === "undefined") {
+    throw new WorkerUnavailableError("Worker API is not available.");
+  }
+
+  if (workerInitError) {
+    throw new WorkerUnavailableError(workerInitError.message);
+  }
+
+  if (workerInstance) {
+    return workerInstance;
+  }
+
+  try {
+    const created = new Worker(new URL("./image-pipeline.worker.ts", import.meta.url), {
+      type: "module",
+    });
+
+    created.onmessage = (event: MessageEvent<WorkerResponseMessage>) => {
+      const message = event.data;
+      const pending = pendingRequests.get(message.requestId);
+      if (!pending) {
+        return;
+      }
+
+      pendingRequests.delete(message.requestId);
+
+      if (message.kind === "error") {
+        const workerError = new Error(message.payload.message);
+        workerError.name = message.payload.name;
+        pending.reject(workerError);
+        return;
+      }
+
+      if (pending.kind === "preview" && message.kind === "preview-result") {
+        const pixels = new Uint8ClampedArray(message.payload.pixels);
+        pending.resolve({
+          width: message.payload.width,
+          height: message.payload.height,
+          imageData: new ImageData(pixels, message.payload.width, message.payload.height),
+          histogram: message.payload.histogram,
+        });
+        return;
+      }
+
+      if (pending.kind === "full" && message.kind === "full-result") {
+        pending.resolve(message.payload);
+        return;
+      }
+
+      pending.reject(new Error("Image pipeline worker response type mismatch."));
+    };
+
+    created.onerror = () => {
+      handleWorkerFailure(new Error("Image pipeline worker crashed."));
+    };
+
+    created.onmessageerror = () => {
+      handleWorkerFailure(new Error("Image pipeline worker message deserialization failed."));
+    };
+
+    workerInstance = created;
+    return created;
+  } catch (error: unknown) {
+    const normalized = error instanceof Error ? error : new Error("Worker initialization failed.");
+    workerInitError = normalized;
+    throw new WorkerUnavailableError(normalized.message);
+  }
+}
+
+function runWorkerRequest<TResponse extends PreviewRenderResult | RenderFullResult>(args: {
+  kind: "preview" | "full";
+  payload: PreviewWorkerPayload | RenderFullOptions;
+  signal?: AbortSignal;
+}): Promise<TResponse> {
+  if (args.signal?.aborted) {
+    return Promise.reject(makeAbortError());
+  }
+
+  const worker = getWorker();
+  const requestId = nextRequestId();
+
+  return new Promise<TResponse>((resolve, reject) => {
+    let isSettled = false;
+    const settleOnce = (callback: () => void): void => {
+      if (isSettled) {
+        return;
+      }
+
+      isSettled = true;
+      callback();
+    };
+
+    const abortHandler = () => {
+      settleOnce(() => {
+        pendingRequests.delete(requestId);
+        worker.postMessage({ kind: "cancel", requestId } satisfies WorkerRequestMessage);
+        reject(makeAbortError());
+      });
+    };
+
+    if (args.signal) {
+      args.signal.addEventListener("abort", abortHandler, { once: true });
+    }
+
+    const wrappedResolve = (value: TResponse) => {
+      settleOnce(() => {
+        if (args.signal) {
+          args.signal.removeEventListener("abort", abortHandler);
+        }
+        resolve(value);
+      });
+    };
+
+    const wrappedReject = (error: unknown) => {
+      settleOnce(() => {
+        if (args.signal) {
+          args.signal.removeEventListener("abort", abortHandler);
+        }
+        reject(error);
+      });
+    };
+
+    pendingRequests.set(requestId, {
+      kind: args.kind,
+      resolve: wrappedResolve as PendingRequest["resolve"],
+      reject: wrappedReject,
+    });
+
+    if (args.kind === "preview") {
+      worker.postMessage({
+        kind: "preview",
+        requestId,
+        payload: args.payload as PreviewWorkerPayload,
+      } satisfies WorkerRequestMessage);
+      return;
+    }
+
+    worker.postMessage({
+      kind: "full",
+      requestId,
+      payload: args.payload as RenderFullOptions,
+    } satisfies WorkerRequestMessage);
+  });
+}
+
+export async function renderPreviewWithWorkerFallback(options: {
+  sourceUrl: string;
+  steps: readonly PipelineStep[];
+  previewWidth: number;
+  signal?: AbortSignal;
+}): Promise<PreviewRenderResult> {
+  try {
+    return await runWorkerRequest<PreviewRenderResult>({
+      kind: "preview",
+      payload: {
+        sourceUrl: options.sourceUrl,
+        steps: options.steps,
+        previewWidth: options.previewWidth,
+      },
+      signal: options.signal,
+    });
+  } catch (error: unknown) {
+    if (isAbortError(error)) {
+      throw error;
+    }
+
+    return await renderPreview(options);
+  }
+}
+
+export async function renderFullWithWorkerFallback(
+  options: RenderFullOptions,
+): Promise<RenderFullResult> {
+  try {
+    return await runWorkerRequest<RenderFullResult>({
+      kind: "full",
+      payload: options,
+      signal: options.signal,
+    });
+  } catch (error: unknown) {
+    if (isAbortError(error)) {
+      throw error;
+    }
+
+    return await renderFull(options);
+  }
+}
+
+export function isPipelineAbortError(error: unknown): boolean {
+  return isAbortError(error);
+}