Upgrade major dependencies (eventsource v4, date-fns v4, vitest v4)

CLAUDE.md

@@ -28,6 +28,15 @@ Comments explain what code does or why it exists:
 - Never mock behavior in end-to-end tests - use real data
 - Mock as little as possible in unit tests - try to use real data
 - Find root causes, not symptoms. Read error messages carefully before attempting fixes.
+- When mocking constructors (classes) with `vi.mocked(...).mockImplementation()`, use regular functions, not arrow functions. Arrow functions can't be called with `new`.
+  ```typescript
+  // ✗ Wrong
+  vi.mocked(SomeClass).mockImplementation(() => mock);
+  // ✓ Correct
+  vi.mocked(SomeClass).mockImplementation(function () {
+  	return mock;
+  });
+  ```
 
 ## Version Control
 

CONTRIBUTING.md

@@ -122,8 +122,6 @@ Some dependencies are not directly used in the source but are required anyway.
 
 - `bufferutil` and `utf-8-validate` are peer dependencies of `ws`.
 - `ua-parser-js` and `dayjs` are used by the Coder API client.
-- `glob`, `nyc`, `vscode-test`, and `@vscode/test-electron` are currently unused
-  but we need to switch back to them from `vitest`.
 
 The coder client is vendored from coder/coder. Every now and then, we should be running `yarn upgrade coder --latest`
 to make sure we're using up to date versions of the client.

package.json

@@ -404,33 +404,31 @@
 	"dependencies": {
 		"@peculiar/x509": "^1.14.2",
 		"axios": "1.13.2",
-		"date-fns": "^3.6.0",
-		"eventsource": "^3.0.6",
+		"date-fns": "^4.1.0",
+		"eventsource": "^4.1.0",
 		"find-process": "^2.0.0",
 		"jsonc-parser": "^3.3.1",
-		"openpgp": "^6.2.2",
+		"openpgp": "^6.3.0",
 		"pretty-bytes": "^7.1.0",
 		"proper-lockfile": "^4.1.2",
 		"proxy-agent": "^6.5.0",
 		"semver": "^7.7.3",
-		"ua-parser-js": "1.0.40",
+		"ua-parser-js": "^1.0.41",
 		"ws": "^8.18.3",
-		"zod": "^4.1.12"
+		"zod": "^4.3.2"
 	},
 	"devDependencies": {
 		"@types/eventsource": "^3.0.0",
-		"@types/glob": "^7.1.3",
 		"@types/node": "^22.14.1",
 		"@types/proper-lockfile": "^4.1.4",
 		"@types/semver": "^7.7.1",
-		"@types/ua-parser-js": "0.7.36",
+		"@types/ua-parser-js": "0.7.39",
 		"@types/vscode": "^1.73.0",
 		"@types/ws": "^8.18.1",
 		"@typescript-eslint/eslint-plugin": "^8.49.0",
 		"@typescript-eslint/parser": "^8.50.1",
-		"@vitest/coverage-v8": "^3.2.4",
+		"@vitest/coverage-v8": "^4.0.16",
 		"@vscode/test-cli": "^0.0.12",
-		"@vscode/test-electron": "^2.5.2",
 		"@vscode/vsce": "^3.7.1",
 		"bufferutil": "^4.0.9",
 		"coder": "https://github.com/coder/coder#main",
@@ -443,17 +441,14 @@
 		"eslint-plugin-md": "^1.0.19",
 		"eslint-plugin-package-json": "^0.85.0",
 		"eslint-plugin-prettier": "^5.5.4",
-		"glob": "^13.0.0",
 		"jsonc-eslint-parser": "^2.4.2",
 		"markdown-eslint-parser": "^1.2.1",
 		"memfs": "^4.51.1",
-		"nyc": "^17.1.0",
 		"prettier": "^3.7.4",
 		"ts-loader": "^9.5.4",
 		"typescript": "^5.9.3",
 		"utf-8-validate": "^6.0.6",
-		"vitest": "^3.2.4",
-		"vscode-test": "^1.5.0",
+		"vitest": "^4.0.16",
 		"webpack": "^5.104.1",
 		"webpack-cli": "^6.0.1"
 	},

src/api/coderApi.ts

@@ -354,7 +354,7 @@ export class CoderApi extends Api implements vscode.Disposable {
 		} catch (error) {
 			if (this.is404Error(error)) {
 				this.output.warn(
-					`WebSocket failed, using SSE fallback: ${socketConfigs.apiRoute}`,
+					`WebSocket failed (${socketConfigs.apiRoute}), using SSE fallback: ${fallbackApiRoute}`,
 				);
 				const sse = this.createSseConnection(
 					fallbackApiRoute,

src/api/streamingFetchAdapter.ts

@@ -1,5 +1,5 @@
 import { type AxiosInstance } from "axios";
-import { type FetchLikeInit, type FetchLikeResponse } from "eventsource";
+import { type EventSourceFetchInit, type FetchLikeResponse } from "eventsource";
 import { type IncomingMessage } from "node:http";
 
 /**
@@ -9,10 +9,13 @@ import { type IncomingMessage } from "node:http";
 export function createStreamingFetchAdapter(
 	axiosInstance: AxiosInstance,
 	configHeaders?: Record<string, string>,
-): (url: string | URL, init?: FetchLikeInit) => Promise<FetchLikeResponse> {
+): (
+	url: string | URL,
+	init?: EventSourceFetchInit,
+) => Promise<FetchLikeResponse> {
 	return async (
 		url: string | URL,
-		init?: FetchLikeInit,
+		init?: EventSourceFetchInit,
 	): Promise<FetchLikeResponse> => {
 		const urlStr = url.toString();
 

test/unit/api/coderApi.test.ts

@@ -342,7 +342,7 @@ describe("CoderApi", () => {
 
 		it("falls back to SSE when WebSocket creation fails with 404", async () => {
 			// Only 404 errors trigger SSE fallback - other errors are thrown
-			vi.mocked(Ws).mockImplementation(() => {
+			vi.mocked(Ws).mockImplementation(function () {
 				throw new Error("Unexpected server response: 404");
 			});
 
@@ -380,7 +380,7 @@ describe("CoderApi", () => {
 		});
 
 		it("throws non-404 errors without SSE fallback", async () => {
-			vi.mocked(Ws).mockImplementation(() => {
+			vi.mocked(Ws).mockImplementation(function () {
 				throw new Error("Network error");
 			});
 
@@ -398,7 +398,7 @@ describe("CoderApi", () => {
 				let wsAttempts = 0;
 				const mockEventSources: MockEventSource[] = [];
 
-				vi.mocked(Ws).mockImplementation(() => {
+				vi.mocked(Ws).mockImplementation(function () {
 					wsAttempts++;
 					const mockWs = createMockWebSocket("wss://test", {
 						on: vi.fn((event: string, handler: (e: unknown) => void) => {
@@ -413,7 +413,7 @@ describe("CoderApi", () => {
 					return mockWs as Ws;
 				});
 
-				vi.mocked(EventSource).mockImplementation(() => {
+				vi.mocked(EventSource).mockImplementation(function () {
 					const es = createMockEventSource(`${CODER_URL}/api/v2/test`);
 					mockEventSources.push(es);
 					return es as unknown as EventSource;
@@ -436,7 +436,7 @@ describe("CoderApi", () => {
 
 	const setupAutoOpeningWebSocket = () => {
 		const sockets: Array<Partial<Ws>> = [];
-		vi.mocked(Ws).mockImplementation((url: string | URL) => {
+		vi.mocked(Ws).mockImplementation(function (url: string | URL) {
 			const mockWs = createMockWebSocket(String(url), {
 				on: vi.fn((event, handler) => {
 					if (event === "open") {
@@ -575,7 +575,7 @@ describe("CoderApi", () => {
 	describe("dispose", () => {
 		it("disposes all tracked reconnecting sockets", async () => {
 			const sockets: Array<Partial<Ws>> = [];
-			vi.mocked(Ws).mockImplementation((url: string | URL) => {
+			vi.mocked(Ws).mockImplementation(function (url: string | URL) {
 				const mockWs = createMockWebSocket(String(url), {
 					on: vi.fn((event, handler) => {
 						if (event === "open") {
@@ -701,9 +701,13 @@ function createMockEventSource(url: string): MockEventSource {
 }
 
 function setupWebSocketMock(ws: Partial<Ws>): void {
-	vi.mocked(Ws).mockImplementation(() => ws as Ws);
+	vi.mocked(Ws).mockImplementation(function () {
+		return ws as Ws;
+	});
 }
 
 function setupEventSourceMock(es: Partial<EventSource>): void {
-	vi.mocked(EventSource).mockImplementation(() => es as EventSource);
+	vi.mocked(EventSource).mockImplementation(function () {
+		return es as EventSource;
+	});
 }

test/unit/api/streamingFetchAdapter.test.ts

@@ -1,5 +1,5 @@
 import { type AxiosInstance, type AxiosResponse } from "axios";
-import { type ReaderLike } from "eventsource";
+import { type EventSourceFetchInit, type ReaderLike } from "eventsource";
 import { EventEmitter } from "node:events";
 import { type IncomingMessage } from "node:http";
 import { describe, it, expect, vi } from "vitest";
@@ -8,6 +8,23 @@ import { createStreamingFetchAdapter } from "@/api/streamingFetchAdapter";
 
 const TEST_URL = "https://example.com/api";
 
+/**
+ * Creates a valid EventSourceFetchInit object for testing.
+ * In production, EventSource always provides all required fields.
+ */
+function createFetchInit(
+	overrides: Partial<EventSourceFetchInit> = {},
+): EventSourceFetchInit {
+	return {
+		signal: new AbortController().signal,
+		headers: { Accept: "text/event-stream" },
+		mode: "cors",
+		cache: "no-store",
+		redirect: "follow",
+		...overrides,
+	};
+}
+
 describe("createStreamingFetchAdapter", () => {
 	describe("Request Handling", () => {
 		it("passes URL, signal, and responseType to axios", async () => {
@@ -18,12 +35,12 @@ describe("createStreamingFetchAdapter", () => {
 			const adapter = createStreamingFetchAdapter(mockAxios);
 			const signal = new AbortController().signal;
 
-			await adapter(TEST_URL, { signal });
+			await adapter(TEST_URL, createFetchInit({ signal }));
 
 			expect(mockAxios.request).toHaveBeenCalledWith({
 				url: TEST_URL,
 				signal, // correctly passes signal
-				headers: {},
+				headers: { Accept: "text/event-stream" },
 				responseType: "stream",
 				validateStatus: expect.any(Function),
 			});
@@ -36,27 +53,34 @@ describe("createStreamingFetchAdapter", () => {
 
 			// Test 1: No config headers, only init headers
 			const adapter1 = createStreamingFetchAdapter(mockAxios);
-			await adapter1(TEST_URL, {
-				headers: { "X-Init": "init-value" },
-			});
+			await adapter1(
+				TEST_URL,
+				createFetchInit({
+					headers: { Accept: "text/event-stream", "X-Init": "init-value" },
+				}),
+			);
 
 			expect(mockAxios.request).toHaveBeenCalledWith(
 				expect.objectContaining({
-					headers: { "X-Init": "init-value" },
+					headers: { Accept: "text/event-stream", "X-Init": "init-value" },
 				}),
 			);
 
 			// Test 2: Config headers merge with init headers
 			const adapter2 = createStreamingFetchAdapter(mockAxios, {
 				"X-Config": "config-value",
 			});
-			await adapter2(TEST_URL, {
-				headers: { "X-Init": "init-value" },
-			});
+			await adapter2(
+				TEST_URL,
+				createFetchInit({
+					headers: { Accept: "text/event-stream", "X-Init": "init-value" },
+				}),
+			);
 
 			expect(mockAxios.request).toHaveBeenCalledWith(
 				expect.objectContaining({
 					headers: {
+						Accept: "text/event-stream",
 						"X-Init": "init-value",
 						"X-Config": "config-value",
 					},
@@ -67,13 +91,16 @@ describe("createStreamingFetchAdapter", () => {
 			const adapter3 = createStreamingFetchAdapter(mockAxios, {
 				"X-Header": "config-value",
 			});
-			await adapter3(TEST_URL, {
-				headers: { "X-Header": "init-value" },
-			});
+			await adapter3(
+				TEST_URL,
+				createFetchInit({
+					headers: { Accept: "text/event-stream", "X-Header": "init-value" },
+				}),
+			);
 
 			expect(mockAxios.request).toHaveBeenCalledWith(
 				expect.objectContaining({
-					headers: { "X-Header": "config-value" },
+					headers: { Accept: "text/event-stream", "X-Header": "config-value" },
 				}),
 			);
 		});

test/unit/websocket/sseConnection.test.ts

@@ -356,7 +356,9 @@ function createMockEventSource(
 }
 
 function setupEventSourceMock(es: Partial<EventSource>): void {
-	vi.mocked(EventSource).mockImplementation(() => es as EventSource);
+	vi.mocked(EventSource).mockImplementation(function () {
+		return es as EventSource;
+	});
 }
 
 function waitForNextTick(): Promise<void> {