fix: surface silent update-check parse failures

The update checker silently swallowed invalid package metadata and cached
JSON parse failures. Keep the same fallback behavior, but log those cases
at debug level so malformed local state is observable during diagnosis.

Author: ndycode

lib/auto-update-checker.ts

@@ -42,7 +42,10 @@ function getCurrentVersion(): string {
     const packageJsonPath = join(import.meta.dirname ?? __dirname, "..", "package.json");
     const packageJson = JSON.parse(readFileSync(packageJsonPath, "utf8")) as { version: string };
     return packageJson.version;
-  } catch {
+  } catch (error) {
+    log.debug("Failed to read current package version", {
+      error: error instanceof Error ? error.message : String(error),
+    });
     return "0.0.0";
   }
 }
@@ -52,7 +55,10 @@ function loadCache(): UpdateCheckCache | null {
     if (!existsSync(CACHE_FILE)) return null;
     const content = readFileSync(CACHE_FILE, "utf8");
     return JSON.parse(content) as UpdateCheckCache;
-  } catch {
+  } catch (error) {
+    log.debug("Failed to load update cache", {
+      error: error instanceof Error ? error.message : String(error),
+    });
     return null;
   }
 }

test/auto-update-checker.test.ts

@@ -14,6 +14,11 @@ describe("auto-update-checker", () => {
 	let checkForUpdates: typeof import("../lib/auto-update-checker.js").checkForUpdates;
 	let checkAndNotify: typeof import("../lib/auto-update-checker.js").checkAndNotify;
 	let clearUpdateCache: typeof import("../lib/auto-update-checker.js").clearUpdateCache;
+	let logger: {
+		debug: ReturnType<typeof vi.fn>;
+		info: ReturnType<typeof vi.fn>;
+		warn: ReturnType<typeof vi.fn>;
+	};
 
 	const mockPackageJson = { version: "4.12.0" };
 
@@ -22,6 +27,14 @@ describe("auto-update-checker", () => {
 		vi.useFakeTimers();
 		vi.setSystemTime(new Date("2026-01-30T12:00:00Z"));
 		mockPackageJson.version = "4.12.0";
+		logger = {
+			debug: vi.fn(),
+			info: vi.fn(),
+			warn: vi.fn(),
+		};
+		vi.doMock("../lib/logger.js", () => ({
+			createLogger: () => logger,
+		}));
 
 		fs = await import("node:fs");
 		vi.mocked(fs.readFileSync).mockImplementation((path: unknown) => {
@@ -228,6 +241,27 @@ describe("auto-update-checker", () => {
 	});
 
 	describe("checkForUpdates", () => {
+		it("logs debug details when package metadata cannot be parsed", async () => {
+			vi.mocked(fs.readFileSync).mockImplementation((path: unknown) => {
+				if (String(path).includes("package.json")) {
+					return "{";
+				}
+				throw new Error("File not found");
+			});
+			vi.mocked(globalThis.fetch).mockResolvedValue({
+				ok: true,
+				json: async () => ({ version: "5.0.0" }),
+			} as Response);
+
+			const result = await checkForUpdates(true);
+
+			expect(result.currentVersion).toBe("0.0.0");
+			expect(logger.debug).toHaveBeenCalledWith(
+				"Failed to read current package version",
+				expect.objectContaining({ error: expect.any(String) }),
+			);
+		});
+
 		it("uses cache when check is recent", async () => {
 			const cacheData = {
 				lastCheck: Date.now() - 1000 * 60 * 60,
@@ -252,6 +286,31 @@ describe("auto-update-checker", () => {
 			expect(result.latestVersion).toBe("5.0.0");
 		});
 
+		it("logs debug details when cached update JSON is unreadable", async () => {
+			vi.mocked(fs.existsSync).mockReturnValue(true);
+			vi.mocked(fs.readFileSync).mockImplementation((path: unknown) => {
+				if (String(path).includes("package.json")) {
+					return JSON.stringify(mockPackageJson);
+				}
+				if (String(path).includes("update-check-cache.json")) {
+					return "{";
+				}
+				throw new Error("File not found");
+			});
+			vi.mocked(globalThis.fetch).mockResolvedValue({
+				ok: true,
+				json: async () => ({ version: "5.0.0" }),
+			} as Response);
+
+			await checkForUpdates();
+
+			expect(logger.debug).toHaveBeenCalledWith(
+				"Failed to load update cache",
+				expect.objectContaining({ error: expect.any(String) }),
+			);
+			expect(globalThis.fetch).toHaveBeenCalled();
+		});
+
 		it("handles cached null latestVersion without update", async () => {
 			const cacheData = {
 				lastCheck: Date.now() - 1000 * 60 * 60,