Validate image dimensions before sending to Anthropic Messages API

src/platform/endpoint/node/messagesApi.ts

@@ -6,6 +6,7 @@
 import { ContentBlockParam, DocumentBlockParam, ImageBlockParam, MessageParam, RedactedThinkingBlockParam, TextBlockParam, ThinkingBlockParam, ToolReferenceBlockParam, ToolResultBlockParam } from '@anthropic-ai/sdk/resources';
 import { Raw } from '@vscode/prompt-tsx';
 import { Response } from '../../../platform/networking/common/fetcherService';
+import { getImageDimensions } from '../../../util/common/imageUtils';
 import { AsyncIterableObject } from '../../../util/vs/base/common/async';
 import { SSEParser } from '../../../util/vs/base/common/sseParser';
 import { generateUuid } from '../../../util/vs/base/common/uuid';
@@ -372,6 +373,29 @@ function tryParseToolReferences(content: ContentBlockParam[], validToolNames?: S
 .map((name): ToolReferenceBlockParam => ({ type: 'tool_reference', tool_name: name }));
 }
 
+/**
+ * Maximum allowed image dimension (width or height) for the Anthropic Messages API.
+ * Images exceeding this limit in either dimension will be rejected.
+ * See: https://docs.anthropic.com/en/docs/build-with-claude/vision#image-requirements
+ */
+const ANTHROPIC_MAX_IMAGE_DIMENSION = 8000;
+
+function validateImageDimensions(dataUrl: string): void {
+try {
+const { width, height } = getImageDimensions(dataUrl);
+if (width > ANTHROPIC_MAX_IMAGE_DIMENSION || height > ANTHROPIC_MAX_IMAGE_DIMENSION) {
+throw new Error(
+`Image dimensions ${width}x${height} exceed the maximum allowed size of ${ANTHROPIC_MAX_IMAGE_DIMENSION}x${ANTHROPIC_MAX_IMAGE_DIMENSION} pixels. Please resize the image and try again.`
+);
+}
+} catch (e) {
+if (e instanceof Error && e.message.includes('exceed the maximum allowed size')) {
+throw e;
+}
+// If we can't read dimensions (corrupted header, etc.), let the API handle it
+}
+}
+
 function rawContentToAnthropicContent(content: readonly Raw.ChatCompletionContentPart[], cacheTtl?: '5m' | '1h'): ContentBlockParam[] {
 const convertedContent: ContentBlockParam[] = [];
 
@@ -387,6 +411,7 @@ function rawContentToAnthropicContent(content: readonly Raw.ChatCompletionConten
 // Parse data URL: data:image/png;base64,<data>
 const match = url.match(/^data:(image\/(?:jpeg|png|gif|webp));base64,(.+)$/);
 if (match) {
+validateImageDimensions(url);
 convertedContent.push({
 type: 'image',
 source: {

src/platform/endpoint/test/node/messagesApi.spec.ts

@@ -157,6 +157,100 @@ suite('rawMessagesToMessagesAPI', function () {
 expect(findBlock(content, 'text')).toBeDefined();
 });
 
+suite('image dimension validation', function () {
+
+/**
+ * Creates a minimal PNG data URL with the specified dimensions encoded in the IHDR header.
+ * PNG format: 8-byte signature + IHDR chunk (4-byte length + 4-byte type + 4-byte width + 4-byte height + 5 more bytes).
+ */
+function makePngDataUrl(width: number, height: number): string {
+const bytes = new Uint8Array(25);
+// PNG signature
+bytes.set([0x89, 0x50, 0x4E, 0x47, 0x0D, 0x0A, 0x1A, 0x0A], 0);
+// IHDR chunk length (13 bytes)
+bytes.set([0x00, 0x00, 0x00, 0x0D], 8);
+// "IHDR"
+bytes.set([0x49, 0x48, 0x44, 0x52], 12);
+// Width (big-endian uint32)
+const view = new DataView(bytes.buffer);
+view.setUint32(16, width, false);
+// Height (big-endian uint32)
+view.setUint32(20, height, false);
+// Bit depth (8) — needed for valid header parsing
+bytes[24] = 0x08;
+
+let binary = '';
+for (const byte of bytes) {
+binary += String.fromCharCode(byte);
+}
+return `data:image/png;base64,${btoa(binary)}`;
+}
+
+test('throws for image exceeding max dimension in width', function () {
+const oversizedUrl = makePngDataUrl(8001, 100);
+const messages: Raw.ChatMessage[] = [
+{
+role: Raw.ChatRole.User,
+content: [{
+type: Raw.ChatCompletionContentPartKind.Image,
+imageUrl: { url: oversizedUrl },
+}],
+},
+];
+
+expect(() => rawMessagesToMessagesAPI(messages)).toThrowError(/8001x100.*exceed the maximum allowed size.*8000x8000/);
+});
+
+test('throws for image exceeding max dimension in height', function () {
+const oversizedUrl = makePngDataUrl(100, 9000);
+const messages: Raw.ChatMessage[] = [
+{
+role: Raw.ChatRole.User,
+content: [{
+type: Raw.ChatCompletionContentPartKind.Image,
+imageUrl: { url: oversizedUrl },
+}],
+},
+];
+
+expect(() => rawMessagesToMessagesAPI(messages)).toThrowError(/100x9000.*exceed the maximum allowed size.*8000x8000/);
+});
+
+test('allows image within max dimensions', function () {
+const validUrl = makePngDataUrl(8000, 8000);
+const messages: Raw.ChatMessage[] = [
+{
+role: Raw.ChatRole.User,
+content: [{
+type: Raw.ChatCompletionContentPartKind.Image,
+imageUrl: { url: validUrl },
+}],
+},
+];
+
+const result = rawMessagesToMessagesAPI(messages);
+const content = assertContentArray(result.messages[0].content);
+expect(findBlock<ImageBlockParam>(content, 'image')).toBeDefined();
+});
+
+test('allows small image', function () {
+const validUrl = makePngDataUrl(100, 200);
+const messages: Raw.ChatMessage[] = [
+{
+role: Raw.ChatRole.User,
+content: [{
+type: Raw.ChatCompletionContentPartKind.Image,
+imageUrl: { url: validUrl },
+}],
+},
+];
+
+const result = rawMessagesToMessagesAPI(messages);
+const content = assertContentArray(result.messages[0].content);
+expect(findBlock<ImageBlockParam>(content, 'image')).toBeDefined();
+});
+});
+
 suite('custom tool search tool_reference conversion', function () {
 
 function makeToolSearchMessages(toolNames: string[]): Raw.ChatMessage[] {