test(extensions): cover bounded marketplace details

electron/extensions/errorUtils.test.ts

@@ -28,6 +28,28 @@ describe("formatMarketplaceHttpError", () => {
 		).toBe("Marketplace request failed (HTTP 400): Invalid search query");
 	});
 
+	it("uses a JSON message when an error field is absent", () => {
+		expect(
+			formatMarketplaceHttpError({
+				status: 409,
+				contentType: "application/json",
+				body: JSON.stringify({ message: "Extension version already exists" }),
+			}),
+		).toBe("Marketplace request failed (HTTP 409): Extension version already exists");
+	});
+
+	it("bounds long JSON details and marks truncation without splitting Unicode", () => {
+		const detail = `🚀${"x".repeat(200)}`;
+		const message = formatMarketplaceHttpError({
+			status: 400,
+			contentType: "application/problem+json",
+			body: JSON.stringify({ error: detail }),
+		});
+
+		expect(message).toBe(`Marketplace request failed (HTTP 400): 🚀${"x".repeat(198)}…`);
+		expect(Array.from(message.split(": ")[1])).toHaveLength(200);
+	});
+
 	it("does not expose non-JSON response bodies", () => {
 		expect(
 			formatMarketplaceHttpError({

electron/extensions/errorUtils.ts

@@ -25,10 +25,12 @@ export function formatMarketplaceHttpError({
 				const { error, message } = payload as { error?: unknown; message?: unknown };
 				const value = typeof error === "string" ? error : message;
 				if (typeof value === "string" && value.trim()) {
-					detail = value
-						.trim()
-						.replace(/\s+/g, " ")
-						.slice(0, MAX_MARKETPLACE_ERROR_DETAIL_LENGTH);
+					const normalized = value.trim().replace(/\s+/g, " ");
+					const codePoints = Array.from(normalized);
+					detail =
+						codePoints.length > MAX_MARKETPLACE_ERROR_DETAIL_LENGTH
+							? `${codePoints.slice(0, MAX_MARKETPLACE_ERROR_DETAIL_LENGTH - 1).join("")}…`
+							: normalized;
 				}
 			}
 		} catch {