diff --git a/README.md b/README.md
index bca2e0b..a202dff 100644
--- a/README.md
+++ b/README.md
@@ -84,7 +84,7 @@ Run this on the Linux desktop client that should receive `mpv-handler://` links,
 https://github.com/akiirui/mpv-handler/releases/latest/download/mpv-handler-linux-amd64.zip
 ```
 
-The upstream project currently publishes an official Linux release for `amd64` only. On Raspberry Pi or other ARM Linux systems, build or obtain a compatible `mpv-handler` binary first, then point `--root` at that extracted folder instead.
+The upstream project currently publishes an official Linux release for `amd64` only. On Raspberry Pi or other ARM Linux systems, `npm run setup:mpv-handler` now tries to build a compatible binary automatically from upstream source if both `git` and Rust `cargo` are installed. If you prefer not to build locally, pass `--skip-source-build` and provide `--root` with a compatible extracted folder instead.
 
 3. Run the helper against the extracted folder:
 
@@ -92,7 +92,7 @@ The upstream project currently publishes an official Linux release for `amd64` o
 npm run setup:mpv-handler -- --root /path/to/extracted/mpv-handler-linux-amd64
 ```
 
-On Linux the helper copies the binary and desktop files into `~/.local`, writes `config.toml` to `~/.config/mpv-handler/config.toml` (or `$XDG_CONFIG_HOME/mpv-handler/config.toml`), and runs `xdg-mime` for both protocol handlers.
+On Linux the helper copies the binary and desktop files into `~/.local`, writes `config.toml` to `~/.config/mpv-handler/config.toml` (or `$XDG_CONFIG_HOME/mpv-handler/config.toml`), and runs `xdg-mime` for both protocol handlers. On non-`x64` Linux it also auto-builds a staged `mpv-handler` root under `~/.cache/api-mediaplayer/` before installing, unless you pass `--skip-source-build`.
 
 ### Android
 
diff --git a/scripts/README.md b/scripts/README.md
index 7596aa7..4d960b4 100644
--- a/scripts/README.md
+++ b/scripts/README.md
@@ -35,7 +35,7 @@ npm run uninstall:mpv-handler
 https://github.com/akiirui/mpv-handler/releases/latest/download/mpv-handler-linux-amd64.zip
 ```
 
-The official upstream Linux release is currently `amd64` only. On Raspberry Pi or other ARM Linux systems, build or obtain a compatible `mpv-handler` binary first and point `--root` at that extracted folder.
+The official upstream Linux release is currently `amd64` only. On Raspberry Pi or other ARM Linux systems, `npm run setup:mpv-handler` now tries to build a compatible `mpv-handler` binary automatically from upstream source if both `git` and Rust `cargo` are installed. If you do not want that behavior, pass `--skip-source-build` and provide `--root` yourself.
 
 2. Point the helper at that extracted folder:
 
@@ -45,7 +45,7 @@ npm run setup:mpv-handler -- --root /path/to/extracted/mpv-handler-linux-amd64
 
 Run this on the Linux desktop client that should handle `mpv-handler://`, not on the machine that is only serving the web app.
 
-The helper copies files into `~/.local/bin` and `~/.local/share/applications`, writes config to `~/.config/mpv-handler/config.toml` (or `$XDG_CONFIG_HOME/mpv-handler/config.toml`), and runs `xdg-mime` for both protocol handlers.
+The helper copies files into `~/.local/bin` and `~/.local/share/applications`, writes config to `~/.config/mpv-handler/config.toml` (or `$XDG_CONFIG_HOME/mpv-handler/config.toml`), and runs `xdg-mime` for both protocol handlers. On non-`x64` Linux it will first build and stage upstream source into `~/.cache/api-mediaplayer/` unless you pass `--skip-source-build`.
 
 ## Useful flags
 
@@ -54,6 +54,7 @@ npm run setup:mpv-handler -- --help
 npm run setup:mpv-handler -- --root /path/to/mpv-handler
 npm run setup:mpv-handler -- --mpv /path/to/mpv
 npm run setup:mpv-handler -- --ytdl /path/to/yt-dlp
+npm run setup:mpv-handler -- --skip-source-build
 npm run setup:mpv-handler -- --skip-config
 npm run setup:mpv-handler -- --dry-run
 ```
@@ -72,6 +73,7 @@ npm run setup:mpv-handler -- --dry-run
 ### Linux
 
 - validates the extracted upstream release layout
+- auto-builds upstream source on non-`x64` Linux when no compatible local root is available and `git` plus `cargo` are installed
 - creates or updates `config.toml`
 - copies the handler binary to `~/.local/bin/mpv-handler`
 - copies the desktop entries to `~/.local/share/applications`
diff --git a/scripts/setup-mpv-handler.mjs b/scripts/setup-mpv-handler.mjs
index b3b182f..297f918 100644
--- a/scripts/setup-mpv-handler.mjs
+++ b/scripts/setup-mpv-handler.mjs
@@ -9,6 +9,8 @@ import { fileURLToPath } from 'node:url'
 const scriptPath = fileURLToPath(import.meta.url)
 const scriptDir = path.dirname(scriptPath)
 const templateConfigPath = path.join(scriptDir, 'config.toml')
+const UPSTREAM_MPV_HANDLER_REPO = 'https://github.com/akiirui/mpv-handler.git'
+const UPSTREAM_MPV_HANDLER_REF = 'v0.4.2'
 
 const usage = `Usage:
   npm run setup:mpv-handler
@@ -19,6 +21,7 @@ Options:
   --root <path>       Path to the extracted mpv-handler folder.
   --mpv <path>        Override the mpv executable path written to config.toml.
   --ytdl <path>       Override the yt-dlp executable path written to config.toml.
+  --skip-source-build Linux only. Do not auto-build mpv-handler from source on non-x64 systems.
   --skip-config       Do not create or update config.toml.
   --keep-existing     Windows only. Keep existing protocol keys instead of replacing them.
   --dry-run           Print the actions without changing files or running installers.
@@ -35,6 +38,7 @@ function parseArgs(argv) {
     root: '',
     mpv: '',
     ytdl: '',
+    skipSourceBuild: false,
     skipConfig: false,
     keepExisting: false,
     dryRun: false,
@@ -54,6 +58,11 @@ function parseArgs(argv) {
       continue
     }
 
+    if (value === '--skip-source-build') {
+      options.skipSourceBuild = true
+      continue
+    }
+
     if (value === '--keep-existing') {
       options.keepExisting = true
       continue
@@ -136,7 +145,7 @@ function looksLikeRoot(rootPath) {
   return requiredFiles.every((fileName) => isFile(path.join(rootPath, fileName)))
 }
 
-function resolveRoot(options) {
+function findRoot(options) {
   const candidates = []
   if (options.root) candidates.push(path.resolve(options.root))
   candidates.push(scriptDir)
@@ -151,14 +160,78 @@ function resolveRoot(options) {
     }
   }
 
+  return ''
+}
+
+function getLinuxCacheDir() {
+  const xdgCacheHome = process.env.XDG_CACHE_HOME?.trim()
+  return xdgCacheHome
+    ? path.join(xdgCacheHome, 'api-mediaplayer')
+    : path.join(os.homedir(), '.cache', 'api-mediaplayer')
+}
+
+function runCommandOrFail(command, args, options) {
+  const result = spawnSync(command, args, options)
+  if (result.status === 0) return result
+
+  const reason = result.error?.message || `exit code ${result.status ?? 'unknown'}`
+  fail(`${command} failed (${reason}).`)
+}
+
+function prepareLinuxSourceBuildRoot(options) {
+  const gitPath = resolveOnPath(['git'])
+  const cargoPath = resolveOnPath(['cargo'])
+
+  if (!gitPath || !cargoPath) {
+    fail(`Could not find a Linux mpv-handler release for ${process.arch}, and automatic source build requires both git and cargo on PATH. Install them or rerun with --root pointing at a compatible extracted mpv-handler folder.`)
+  }
+
+  const cacheDir = getLinuxCacheDir()
+  const sourceDir = path.join(cacheDir, `mpv-handler-src-${UPSTREAM_MPV_HANDLER_REF}`)
+  const stageDir = path.join(cacheDir, `mpv-handler-linux-${process.arch}`)
+
+  if (options.dryRun) {
+    console.log(`Dry run: would clone ${UPSTREAM_MPV_HANDLER_REPO} at ${UPSTREAM_MPV_HANDLER_REF} into ${sourceDir}`)
+    console.log(`Dry run: would build mpv-handler with cargo in ${sourceDir}`)
+    console.log(`Dry run: would stage Linux assets into ${stageDir}`)
+    return stageDir
+  }
+
+  mkdirSync(cacheDir, { recursive: true })
+
+  if (!existsSync(sourceDir)) {
+    runCommandOrFail(gitPath, ['clone', '--depth', '1', '--branch', UPSTREAM_MPV_HANDLER_REF, UPSTREAM_MPV_HANDLER_REPO, sourceDir], { stdio: 'inherit' })
+  }
+
+  runCommandOrFail(cargoPath, ['build', '--release'], { cwd: sourceDir, stdio: 'inherit' })
+
+  mkdirSync(stageDir, { recursive: true })
+
+  copyFileSync(path.join(sourceDir, 'target', 'release', 'mpv-handler'), path.join(stageDir, 'mpv-handler'))
+  copyFileSync(path.join(sourceDir, 'share', 'linux', 'mpv-handler.desktop'), path.join(stageDir, 'mpv-handler.desktop'))
+  copyFileSync(path.join(sourceDir, 'share', 'linux', 'mpv-handler-debug.desktop'), path.join(stageDir, 'mpv-handler-debug.desktop'))
+  copyFileSync(path.join(sourceDir, 'share', 'linux', 'config.toml'), path.join(stageDir, 'config.toml'))
+  chmodSync(path.join(stageDir, 'mpv-handler'), 0o755)
+
+  return stageDir
+}
+
+function resolveRoot(options) {
+  const resolvedRoot = findRoot(options)
+  if (resolvedRoot) return resolvedRoot
+
   if (process.platform === 'win32') {
     fail('Could not find mpv-handler files. Re-run with --root pointing at the extracted mpv-handler folder.')
   }
 
   if (process.platform === 'linux') {
+    if (process.arch !== 'x64' && !options.skipSourceBuild) {
+      return prepareLinuxSourceBuildRoot(options)
+    }
+
     const archHint = process.arch === 'x64'
       ? 'Download and extract the upstream archive, then pass --root /path/to/extracted/mpv-handler-linux-amd64.'
-      : `The upstream project only publishes an official linux-amd64 archive. On ${process.arch}, build or obtain a compatible mpv-handler binary and pass --root /path/to/extracted/mpv-handler.`
+      : `The upstream project only publishes an official linux-amd64 archive. Install git and cargo to allow automatic source builds, or build/obtain a compatible mpv-handler binary and pass --root /path/to/extracted/mpv-handler.`
     fail(`Could not find a Linux mpv-handler release. ${archHint}`)
   }