diff --git a/packages/lib/api.ts b/packages/lib/api.ts
index 7cf8755f..9375347a 100644
--- a/packages/lib/api.ts
+++ b/packages/lib/api.ts
@@ -443,8 +443,18 @@ export const apiSchema = createSchema({
 	},
 })
 
+function normalizeBackendV3BaseURL(rawBaseURL: string): string {
+	// Allow passing either "https://api.supermemory.ai" or "https://api.supermemory.ai/v3"
+	// (and tolerate trailing slashes) without accidentally producing "/v3/v3".
+	const trimmed = rawBaseURL.replace(/\/+$/, "")
+	return trimmed.endsWith("/v3") ? trimmed : `${trimmed}/v3`
+}
+
+const backendBaseURL =
+	process.env.NEXT_PUBLIC_BACKEND_URL ?? "https://api.supermemory.ai"
+
 export const $fetch = createFetch({
-	baseURL: `${process.env.NEXT_PUBLIC_BACKEND_URL ?? "https://api.supermemory.ai"}/v3`,
+	baseURL: normalizeBackendV3BaseURL(backendBaseURL),
 	credentials: "include",
 	headers: { "X-App-Source": "nova" },
 	onRequest: (context: { headers: Headers }) => {
diff --git a/packages/lib/auth.ts b/packages/lib/auth.ts
index af0e989b..560f15e3 100644
--- a/packages/lib/auth.ts
+++ b/packages/lib/auth.ts
@@ -10,8 +10,18 @@ import {
 } from "better-auth/client/plugins"
 import { createAuthClient } from "better-auth/react"
 
+function normalizeBackendBaseURL(rawBaseURL: string): string {
+	// Accept either "https://api.supermemory.ai" or "https://api.supermemory.ai/v3".
+	// Auth endpoints are mounted at the root base (not under /v3).
+	const trimmed = rawBaseURL.replace(/\/+$/, "")
+	return trimmed.endsWith("/v3") ? trimmed.slice(0, -3) : trimmed
+}
+
+const backendBaseURL =
+	process.env.NEXT_PUBLIC_BACKEND_URL ?? "https://api.supermemory.ai"
+
 export const authClient = createAuthClient({
-	baseURL: process.env.NEXT_PUBLIC_BACKEND_URL ?? "https://api.supermemory.ai",
+	baseURL: normalizeBackendBaseURL(backendBaseURL),
 	fetchOptions: {
 		credentials: "include",
 		headers: { "X-App-Source": "nova" },