diff --git a/apps/api/.env.example b/apps/api/.env.example
index 53a2b25..f62b165 100644
--- a/apps/api/.env.example
+++ b/apps/api/.env.example
@@ -2,3 +2,8 @@ DATABASE_URL=file:./data/app.db
 BETTER_AUTH_SECRET=change-me-to-a-long-random-string
 BETTER_AUTH_URL=http://localhost:3000
 PORT=3000
+
+# Comma-separated browser origins allowed for CORS + better-auth (the worker SPA).
+# Add your phone's LAN origin to test on a device — no code edit needed, e.g.:
+# CORS_ORIGINS=http://localhost:5173,http://192.168.1.50:5173
+CORS_ORIGINS=http://localhost:5173
diff --git a/apps/api/src/app.ts b/apps/api/src/app.ts
index 435a644..11cff19 100644
--- a/apps/api/src/app.ts
+++ b/apps/api/src/app.ts
@@ -5,13 +5,14 @@ import { me } from './routes/me';
 import { activitiesRoutes } from './routes/activities';
 import { sessionsRoutes } from './routes/sessions';
 import { auth } from './auth';
+import { env } from './env';
 
 export function createApp(): Hono {
   const app = new Hono();
   app.use(
     '/api/*',
     cors({
-      origin: ['http://localhost:5173'],
+      origin: env.WEB_ORIGINS,
       allowMethods: ['GET', 'POST', 'PUT', 'DELETE', 'OPTIONS'],
       allowHeaders: ['Content-Type', 'Authorization'],
       exposeHeaders: ['set-auth-token'], // so the SPA can read the bearer token on sign-in
diff --git a/apps/api/src/auth.ts b/apps/api/src/auth.ts
index 0483a9e..edfa0a4 100644
--- a/apps/api/src/auth.ts
+++ b/apps/api/src/auth.ts
@@ -8,7 +8,7 @@ import { env } from './env';
 export const auth = betterAuth({
   secret: env.BETTER_AUTH_SECRET,
   baseURL: env.BETTER_AUTH_URL,
-  trustedOrigins: [env.BETTER_AUTH_URL, 'http://localhost:3000', 'http://localhost:5173'],
+  trustedOrigins: [env.BETTER_AUTH_URL, 'http://localhost:3000', ...env.WEB_ORIGINS],
   database: drizzleAdapter(db, { provider: 'sqlite', schema }),
   emailAndPassword: {
     enabled: true,
diff --git a/apps/api/src/env.ts b/apps/api/src/env.ts
index e01a7a8..882c883 100644
--- a/apps/api/src/env.ts
+++ b/apps/api/src/env.ts
@@ -1,6 +1,14 @@
+const webOrigins = process.env.CORS_ORIGINS?.split(',')
+  .map((s) => s.trim())
+  .filter(Boolean);
+
 export const env = {
   DATABASE_URL: process.env.DATABASE_URL ?? 'file:./data/app.db',
   BETTER_AUTH_SECRET: process.env.BETTER_AUTH_SECRET ?? 'dev-insecure-secret-change-me',
   BETTER_AUTH_URL: process.env.BETTER_AUTH_URL ?? 'http://localhost:3000',
   PORT: Number(process.env.PORT ?? 3000),
+  // Browser origins allowed for CORS + better-auth trustedOrigins. Set CORS_ORIGINS to a
+  // comma-separated list (e.g. "http://localhost:5173,http://192.168.1.50:5173") to let a
+  // phone on the LAN reach the API — no code edit needed. Defaults to the local Vite origin.
+  WEB_ORIGINS: webOrigins && webOrigins.length ? webOrigins : ['http://localhost:5173'],
 };
diff --git a/apps/worker/README.md b/apps/worker/README.md
index cc4b113..530a3d3 100644
--- a/apps/worker/README.md
+++ b/apps/worker/README.md
@@ -26,7 +26,7 @@ Two processes: the API on `:3000` and the worker SPA on `:5173`.
 From the repo root:
 
 ```bash
-yarn workspace @solelog/api db:migrate   # apply migrations (creates ./.tmp DB on first run)
+yarn workspace @solelog/api db:migrate   # apply migrations (creates ./data/app.db on first run)
 yarn workspace @solelog/api db:seed      # idempotent: seeds the reference activities
 yarn workspace @solelog/api start        # Hono server on http://localhost:3000
 ```
@@ -58,10 +58,14 @@ connected to the same Wi-Fi:
    ```
 
    (On Windows PowerShell: `$env:VITE_API_URL='http://<PC-LAN-IP>:3000'; yarn workspace @solelog/worker dev`.)
-4. Add that origin (`http://<PC-LAN-IP>:5173`) to the API's CORS `origin` list
-   (`apps/api/src/app.ts`) **and** to better-auth `trustedOrigins` (`apps/api/src/auth.ts`), then
-   restart the API — otherwise the cross-origin sign-in is blocked and the SPA cannot read the
-   `set-auth-token` response header.
+4. Allow that origin on the API by setting `CORS_ORIGINS` when you start it — **no code edit**:
+
+   ```bash
+   CORS_ORIGINS=http://localhost:5173,http://<PC-LAN-IP>:5173 yarn workspace @solelog/api start
+   ```
+
+   (PowerShell: `$env:CORS_ORIGINS='http://localhost:5173,http://<PC-LAN-IP>:5173'; yarn workspace @solelog/api start`.)
+   Otherwise the cross-origin sign-in is blocked and the SPA cannot read the `set-auth-token` header.
 
 No firewall punch-through, VPN, or tunnel is involved — just the LAN.