diff --git a/README.md b/README.md
index 5a94304..8ec77a1 100644
--- a/README.md
+++ b/README.md
@@ -51,6 +51,8 @@ docker run -d --name trmnl-ha \
 ```
 
 > **Note:** Replace `YOUR_HOST_IP` with your machine's IP (e.g., `192.168.1.100`). Container names like `homeassistant` won't work since HA uses host networking.
+>
+> **Volume mount:** `-v ./trmnl-data:/data` is recommended. `-v ./trmnl-data:/app/data` also works.
 
 Then open `http://localhost:10000` - that's it!
 
diff --git a/trmnl-ha/DOCS.md b/trmnl-ha/DOCS.md
index 8ceab11..ef05840 100644
--- a/trmnl-ha/DOCS.md
+++ b/trmnl-ha/DOCS.md
@@ -91,6 +91,17 @@ docker run -d --name trmnl-ha \
   ghcr.io/usetrmnl/trmnl-ha-amd64:latest
 ```
 
+**Data Persistence:**
+
+Schedules and output screenshots are stored in a persistent data directory. Two volume mount options are supported:
+
+| Mount | Example | Notes |
+|-------|---------|-------|
+| `/data` (recommended) | `-v ./trmnl-data:/data` | Matches docs, used by HA add-on |
+| `/app/data` (also works) | `-v ./trmnl-data:/app/data` | Legacy alternative |
+
+Both options work — the app auto-detects which path is available. If you're already using `/app/data`, there's no need to change.
+
 **Environment Variables:**
 
 | Variable | Required | Description |
@@ -304,7 +315,7 @@ curl "http://192.168.1.x:10000/lovelace/0?viewport=800x480&dithering&palette=bw&
 
 Create cron-based schedules via the Web UI for automatic captures.
 
-**Storage:** `/data/schedules.json` (persists across restarts)
+**Storage:** `schedules.json` in the data directory (persists across restarts when a volume is mounted — see [Data Persistence](#home-assistant-container-docker))
 
 **Manual Trigger:** Click **Send Now** to execute immediately.
 
diff --git a/trmnl-ha/ha-trmnl/const.ts b/trmnl-ha/ha-trmnl/const.ts
index df914ed..8458eb7 100644
--- a/trmnl-ha/ha-trmnl/const.ts
+++ b/trmnl-ha/ha-trmnl/const.ts
@@ -43,6 +43,7 @@ import {
   isValidTimezone,
   hasEnvConfig as checkEnvConfig,
   detectIsAddOn,
+  detectDataDir,
   findBrowser,
   isNetworkError,
   parseOptionsFile,
@@ -196,6 +197,15 @@ if (isAddOn) {
   console.log('[Config] Running in standalone mode')
 }
 
+/**
+ * Persistent data directory for schedules, output screenshots, etc.
+ * - HA add-on: /data (mounted by HA Supervisor)
+ * - Standalone Docker: /data (user-mounted volume)
+ * - Local dev: ./data (relative to cwd)
+ */
+export const DATA_DIR: string = detectDataDir(isAddOn, process.cwd())
+console.log(`[Config] Data directory: ${DATA_DIR}`)
+
 /**
  * Whether to use mock Home Assistant for testing and local development
  * Set MOCK_HA=true environment variable to enable mock mode
diff --git a/trmnl-ha/ha-trmnl/lib/config-helpers.ts b/trmnl-ha/ha-trmnl/lib/config-helpers.ts
index e86b9cd..9bcc713 100644
--- a/trmnl-ha/ha-trmnl/lib/config-helpers.ts
+++ b/trmnl-ha/ha-trmnl/lib/config-helpers.ts
@@ -119,6 +119,26 @@ export function detectIsAddOn(
   )
 }
 
+/**
+ * Determine the data directory for persistence (schedules, output, etc.)
+ *
+ * Priority:
+ * 1. HA add-on mode → /data (mounted by HA Supervisor)
+ * 2. Standalone Docker with /data mount → /data (user-mounted volume)
+ * 3. Local dev → ./data relative to cwd (no /data exists)
+ *
+ * @param isAddOn - Whether running as HA add-on
+ * @param cwd - Current working directory (for local dev fallback)
+ * @returns Absolute path to data directory
+ */
+export function detectDataDir(isAddOn: boolean, cwd: string): string {
+  if (isAddOn) return '/data'
+  // NOTE: In standalone Docker, users mount -v ./trmnl-data:/data
+  // existsSync('/data') is true when a volume is mounted there
+  if (existsSync('/data')) return '/data'
+  return `${cwd}/data`
+}
+
 /**
  * Parse boolean from environment variable string
  * @param value - String value from env var
diff --git a/trmnl-ha/ha-trmnl/lib/scheduleStore.ts b/trmnl-ha/ha-trmnl/lib/scheduleStore.ts
index 5b5efc1..a5b1583 100644
--- a/trmnl-ha/ha-trmnl/lib/scheduleStore.ts
+++ b/trmnl-ha/ha-trmnl/lib/scheduleStore.ts
@@ -8,20 +8,17 @@
  */
 
 import fs from 'node:fs/promises'
-import { existsSync } from 'node:fs'
 import path from 'node:path'
-import { fileURLToPath } from 'node:url'
 import type {
   Schedule,
   ScheduleInput,
   ScheduleUpdate,
 } from '../types/domain.js'
+import { DATA_DIR } from '../const.js'
 import { schedulerLogger } from './logger.js'
 
 const log = schedulerLogger()
 
-const __dirname = path.dirname(fileURLToPath(import.meta.url))
-
 // =============================================================================
 // FILE LOCKING (prevents race conditions on concurrent writes)
 // =============================================================================
@@ -62,11 +59,7 @@ async function withLock<T>(
   }
 }
 
-// NOTE: existsSync is used at startup only (sync is fine for config detection)
-const isAddOn = existsSync('/data/options.json')
-const DEFAULT_SCHEDULES_FILE = isAddOn
-  ? '/data/schedules.json'
-  : path.join(__dirname, '..', 'data', 'schedules.json')
+const DEFAULT_SCHEDULES_FILE = path.join(DATA_DIR, 'schedules.json')
 
 /**
  * Check if file exists (async)
diff --git a/trmnl-ha/ha-trmnl/scheduler.ts b/trmnl-ha/ha-trmnl/scheduler.ts
index d7013df..b72732f 100644
--- a/trmnl-ha/ha-trmnl/scheduler.ts
+++ b/trmnl-ha/ha-trmnl/scheduler.ts
@@ -19,18 +19,15 @@
 
 import fs from 'node:fs'
 import path from 'node:path'
-import { fileURLToPath } from 'node:url'
 import { loadSchedules } from './lib/scheduleStore.js'
 import { ScheduleExecutor, type ScreenshotFunction, type ExecutionResult } from './lib/scheduler/schedule-executor.js'
 import { CronJobManager } from './lib/scheduler/cron-job-manager.js'
-import { SCHEDULER_RELOAD_INTERVAL_MS, SCHEDULER_OUTPUT_DIR_NAME } from './const.js'
+import { SCHEDULER_RELOAD_INTERVAL_MS, SCHEDULER_OUTPUT_DIR_NAME, DATA_DIR } from './const.js'
 import type { Schedule } from './types/domain.js'
 import { schedulerLogger } from './lib/logger.js'
 
 const log = schedulerLogger()
 
-const __dirname = path.dirname(fileURLToPath(import.meta.url))
-
 /**
  * High-level scheduler orchestrating cron jobs and screenshot execution.
  */
@@ -46,7 +43,7 @@ export class Scheduler {
    * @param screenshotFn - Screenshot capture function (async)
    */
   constructor(screenshotFn: ScreenshotFunction) {
-    this.#outputDir = path.join(__dirname, SCHEDULER_OUTPUT_DIR_NAME)
+    this.#outputDir = path.join(DATA_DIR, SCHEDULER_OUTPUT_DIR_NAME)
     this.#cronManager = new CronJobManager()
     this.#executor = new ScheduleExecutor(screenshotFn, this.#outputDir)
 
diff --git a/trmnl-ha/ha-trmnl/scripts/docker-entrypoint.sh b/trmnl-ha/ha-trmnl/scripts/docker-entrypoint.sh
index 92c9521..f096a27 100755
--- a/trmnl-ha/ha-trmnl/scripts/docker-entrypoint.sh
+++ b/trmnl-ha/ha-trmnl/scripts/docker-entrypoint.sh
@@ -2,5 +2,19 @@
 set -e
 
 echo "Starting TRMNL HA..."
-mkdir -p logs output data
+
+# Ensure data subdirectories exist for persistence.
+# Supports two mount points:
+#   -v ./trmnl-data:/data      (recommended, matches docs)
+#   -v ./trmnl-data:/app/data  (also works, legacy workaround)
+# In HA add-on mode, /data is managed by HA Supervisor.
+if [ -d "/data" ]; then
+  mkdir -p /data/output
+else
+  mkdir -p data/output
+fi
+
+# Local app directories (logs stay app-local, not persisted)
+mkdir -p logs
+
 exec "$@"
diff --git a/trmnl-ha/ha-trmnl/tests/unit/config-helpers.test.ts b/trmnl-ha/ha-trmnl/tests/unit/config-helpers.test.ts
index 487f6b9..de9ed17 100644
--- a/trmnl-ha/ha-trmnl/tests/unit/config-helpers.test.ts
+++ b/trmnl-ha/ha-trmnl/tests/unit/config-helpers.test.ts
@@ -17,6 +17,7 @@ import {
   isValidTimezone,
   hasEnvConfig,
   detectIsAddOn,
+  detectDataDir,
   parseEnvBoolean,
   isNetworkError,
   parseOptionsFile,
@@ -204,6 +205,32 @@ describe('detectIsAddOn', () => {
   })
 })
 
+// =============================================================================
+// Data Directory Detection
+// =============================================================================
+
+describe('detectDataDir', () => {
+  it('returns /data for HA add-on mode', () => {
+    expect(detectDataDir(true, '/app')).toBe('/data')
+  })
+
+  it('returns cwd/data when /data does not exist', () => {
+    // Covers local dev AND the -v ./trmnl-data:/app/data workaround mount.
+    // In Docker with WORKDIR /app, cwd/data resolves to /app/data.
+    const result = detectDataDir(false, '/Users/dev/project')
+    expect(result).toBe('/Users/dev/project/data')
+  })
+
+  it('supports /app/data path in Docker (WORKDIR /app fallback)', () => {
+    // Simulates Docker with WORKDIR /app and -v ./trmnl-data:/app/data.
+    // Since /data doesn't exist on the host, falls through to cwd/data.
+    // NOTE: In Docker with -v ./x:/data, existsSync('/data') is true → '/data'.
+    // Both mount points are supported; this test covers the fallback branch.
+    const result = detectDataDir(false, '/app')
+    expect(['/data', '/app/data']).toContain(result)
+  })
+})
+
 // =============================================================================
 // Boolean Environment Variable Parsing
 // =============================================================================