diff --git a/plugins/decky-vault/src/lib/api.ts b/plugins/decky-vault/src/lib/api.ts
new file mode 100644
index 0000000..c6db3e5
--- /dev/null
+++ b/plugins/decky-vault/src/lib/api.ts
@@ -0,0 +1,76 @@
+import { callable } from "@decky/api"
+
+// ── Settings ────────────────────────────────────────────────────
+export const getSettings = callable<[], Record<string, unknown>>("get_settings")
+export const setSetting = callable<[key: string, value: unknown], Record<string, unknown>>("set_setting")
+
+// ── MangoHud ────────────────────────────────────────────────────
+export const checkMangohud = callable<[], {
+  installed: boolean
+  path: string
+  version: string
+  error?: string
+}>("check_mangohud")
+
+export const writeMangohudConfig = callable<[], {
+  success: boolean
+  path: string
+  error?: string
+}>("write_mangohud_config")
+
+export const getMangohudConfig = callable<[], {
+  exists: boolean
+  content: string
+  path: string
+}>("get_mangohud_config")
+
+export const readAndParseMangohudLog = callable<[logPath?: string], {
+  fpsAvg?: number
+  fpsLow?: number
+  fpsHigh?: number
+  fpsOnePercentLow?: number | null
+  tdpWatts?: number | null
+  error?: string
+}>("read_and_parse_mangohud_log")
+
+export const clearMangohudLog = callable<[logPath?: string], {
+  success: boolean
+  error?: string
+}>("clear_mangohud_log")
+
+// ── System Info ─────────────────────────────────────────────────
+export const getHardwareInfo = callable<[], {
+  slug: string
+  name: string
+  raw: string
+}>("get_hardware_info")
+
+export const getOsVersion = callable<[], string>("get_os_version")
+
+export const getProtonVersion = callable<[appId: number], string>("get_proton_version")
+
+export const getLaunchOptions = callable<[appId: number], string>("get_launch_options")
+
+// ── Export ──────────────────────────────────────────────────────
+export const exportToFile = callable<[data: Record<string, unknown>, exportPath: string], {
+  success: boolean
+  path: string
+  error?: string
+}>("export_to_file")
+
+// ── Upload ──────────────────────────────────────────────────────
+export const uploadToDeckyvault = callable<[
+  data: Record<string, unknown>,
+  apiKey: string,
+  baseUrl?: string
+], {
+  success: boolean
+  data?: { id: string; gameId: string; versionId: string; createdAt: string; authMethod: string }
+  error?: string
+  status?: number
+}>("upload_to_deckyvault")
+
+export const testApiKey = callable<[apiKey: string, baseUrl?: string], {
+  valid: boolean
+  error?: string
+}>("test_api_key")
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