update to match copilot extension mimetype and data schema

Author: seeM

extensions/positron-assistant/src/anthropic.ts

@@ -498,10 +498,7 @@ function withCacheControl<T extends CacheControllableBlockParam>(
 		log.debug(`[anthropic] Adding cache breakpoint to ${part.type} part. Source: ${source}`);
 		return {
 			...part,
-			// Pass the data through without validation, let the Anthropic API handle errors.
-			cache_control: {
-				type: cachBreakpoint.type,
-			},
+			cache_control: cachBreakpoint,
 		};
 	} catch (error) {
 		log.error(`[anthropic] Failed to parse cache breakpoint: ${error}`);

extensions/positron-assistant/src/types.ts

@@ -23,8 +23,12 @@ export enum PositronAssistantToolName {
 export enum LanguageModelDataPartMimeType {
 	/**
 	 * Defines a cache breakpoint (e.g. for Anthropic's manual prompt caching).
+	 *
+	 * By matching the Copilot extension, other extensions that use models from either Copilot
+	 * or Positron Assistant can set cache breakpoints with the same mime type.
+	 * See: https://github.com/microsoft/vscode-copilot-chat/blob/6aeac371813be9037e74395186ec5b5b94089245/src/platform/endpoint/common/endpointTypes.ts#L7
 	 */
-	CacheBreakpoint = 'application/cache-control+json',
+	CacheControl = 'cache_control',
 }
 
 /**

extensions/positron-assistant/src/utils.ts

@@ -403,9 +403,9 @@ export function isWorkspaceOpen(): boolean {
 /**
  * Checks if a given language model part defines a cache breakpoint.
  */
-export function isCacheBreakpointPart(part: unknown): part is vscode.LanguageModelDataPart & { mimeType: LanguageModelDataPartMimeType.CacheBreakpoint } {
-	return (part instanceof vscode.LanguageModelDataPart) &&
-		part.mimeType === LanguageModelDataPartMimeType.CacheBreakpoint;
+export function isCacheBreakpointPart(part: unknown): part is vscode.LanguageModelDataPart & { mimeType: LanguageModelDataPartMimeType.CacheControl } {
+	return part instanceof vscode.LanguageModelDataPart &&
+		part.mimeType === LanguageModelDataPartMimeType.CacheControl;
 }
 
 /**
@@ -417,40 +417,28 @@ export function isCacheBreakpointPart(part: unknown): part is vscode.LanguageMod
  *   or if the parsed data does not match the expected schema.
  */
 export function parseCacheBreakpoint(part: vscode.LanguageModelDataPart): LanguageModelCacheBreakpoint {
-	if (part.mimeType !== LanguageModelDataPartMimeType.CacheBreakpoint) {
-		throw new Error(`Expected LanguageModelDataPart with mimeType ${LanguageModelDataPartMimeType.CacheBreakpoint}, but got ${part.mimeType}`);
+	if (part.mimeType !== LanguageModelDataPartMimeType.CacheControl) {
+		throw new Error(`Expected LanguageModelDataPart with mimeType ${LanguageModelDataPartMimeType.CacheControl}, but got ${part.mimeType}`);
 	}
 
-	let data: unknown;
-	try {
-		data = JSON.parse(part.data.toString());
-	} catch (error) {
-		throw new Error(`Failed to parse LanguageModelDataPart JSON: ${error}`);
+	// By matching the Copilot extension, other extensions that use models from either Copilot
+	// or Positron Assistant can set cache breakpoints with the same schema.
+	// See: https://github.com/microsoft/vscode-copilot-chat/blob/6aeac371813be9037e74395186ec5b5b94089245/src/extension/byok/vscode-node/anthropicMessageConverter.ts#L22
+	const type = part.data.toString();
+	if (!(type === LanguageModelCacheBreakpointType.Ephemeral)) {
+		throw new Error(`Expected LanguageModelDataPart to contain a LanguageModelCacheBreakpoint, but got: ${type}`);
 	}
 
-	if (!isCacheBreakpoint(data)) {
-		throw new Error(`Expected LanguageModelDataPart to contain a LanguageModelCacheBreakpoint, but got: ${JSON.stringify(data)}`);
-	}
-
-	return data;
-}
-
-function isCacheBreakpoint(obj: unknown): obj is LanguageModelCacheBreakpoint {
-	return typeof obj === 'object' &&
-		obj !== null &&
-		'type' in obj &&
-		obj.type === LanguageModelCacheBreakpointType.Ephemeral;
+	return { type };
 }
 
 /**
  * Create a language model part that represents a cache control point.
  * @returns A language model part representing the cache control point.
  */
 export function languageModelCacheBreakpointPart(): vscode.LanguageModelDataPart {
-	return vscode.LanguageModelDataPart.json(
-		{
-			type: LanguageModelCacheBreakpointType.Ephemeral,
-		} satisfies LanguageModelCacheBreakpoint,
-		LanguageModelDataPartMimeType.CacheBreakpoint,
-	);
+	// By matching the Copilot extension, other extensions that use models from either Copilot
+	// or Positron Assistant can set cache breakpoints with the same schema.
+	// See: https://github.com/microsoft/vscode-copilot-chat/blob/6aeac371813be9037e74395186ec5b5b94089245/src/extension/byok/vscode-node/anthropicMessageConverter.ts#L22
+	return vscode.LanguageModelDataPart.text(LanguageModelCacheBreakpointType.Ephemeral, LanguageModelDataPartMimeType.CacheControl);
 }