diff --git a/pc/start_streamdeck.ps1 b/pc/start_streamdeck.ps1
index 1ef22ef..64d3750 100644
--- a/pc/start_streamdeck.ps1
+++ b/pc/start_streamdeck.ps1
@@ -8,6 +8,7 @@ $repoRoot = Split-Path -Parent $PSScriptRoot
 $overlayDir = Join-Path $repoRoot "overlay"
 $dataDir = Join-Path $repoRoot "data"
 $launcherLog = Join-Path $dataDir "startup-launcher.log"
+$backendUrl = "http://127.0.0.1:8000/api/state"
 
 if (-not (Test-Path $dataDir)) {
     New-Item -ItemType Directory -Path $dataDir | Out-Null
@@ -21,16 +22,11 @@ function Write-LauncherLog {
 
 function Resolve-PythonPath {
     $venvPython = Join-Path $repoRoot ".venv\Scripts\python.exe"
-    if (Test-Path $venvPython) {
-        return $venvPython
+    if (-not (Test-Path $venvPython)) {
+        throw "Project Python environment not found: $venvPython. Run: py -3.14 -m venv .venv"
     }
 
-    $pythonCmd = Get-Command python -ErrorAction SilentlyContinue
-    if ($null -ne $pythonCmd) {
-        return $pythonCmd.Source
-    }
-
-    throw "Could not find Python. Install Python or create .venv first."
+    return (Resolve-Path $venvPython).Path
 }
 
 function Resolve-NpmPath {
@@ -42,6 +38,18 @@ function Resolve-NpmPath {
     throw "Could not find npm.cmd. Install Node.js/npm first."
 }
 
+function Test-PythonRuntime {
+    param([string]$PythonPath)
+
+    $output = & $PythonPath -c "import uvicorn, backend.main; print('backend imports OK')" 2>&1
+    if ($LASTEXITCODE -ne 0) {
+        $details = ($output | Out-String).Trim()
+        throw "Backend Python runtime validation failed: $details"
+    }
+
+    Write-LauncherLog "Python runtime verified: $PythonPath"
+}
+
 function Start-HiddenProcess {
     param(
         [string]$Name,
@@ -54,18 +62,54 @@ function Start-HiddenProcess {
 
     if ($DryRun) {
         Write-LauncherLog "DRY RUN -> $Name | $FilePath $($Arguments -join ' ')"
-        return
+        return $null
     }
 
-    Start-Process `
+    $process = Start-Process `
         -FilePath $FilePath `
         -ArgumentList $Arguments `
         -WorkingDirectory $WorkingDirectory `
         -WindowStyle Hidden `
         -RedirectStandardOutput $StdOutPath `
-        -RedirectStandardError $StdErrPath | Out-Null
+        -RedirectStandardError $StdErrPath `
+        -PassThru
 
-    Write-LauncherLog "Started $Name."
+    Write-LauncherLog "Started $Name process (PID $($process.Id))."
+    return $process
+}
+
+function Test-BackendReady {
+    try {
+        $response = Invoke-WebRequest -UseBasicParsing -Uri $backendUrl -Method Get -TimeoutSec 2 -ErrorAction Stop
+        return $response.StatusCode -eq 200
+    } catch {
+        return $false
+    }
+}
+
+function Wait-ForBackendReady {
+    param(
+        [System.Diagnostics.Process]$Process,
+        [int]$TimeoutSeconds = 30
+    )
+
+    $deadline = (Get-Date).AddSeconds($TimeoutSeconds)
+    do {
+        if (Test-BackendReady) {
+            return $true
+        }
+
+        if ($null -ne $Process) {
+            $Process.Refresh()
+            if ($Process.HasExited) {
+                return $false
+            }
+        }
+
+        Start-Sleep -Milliseconds 500
+    } while ((Get-Date) -lt $deadline)
+
+    return $false
 }
 
 function Is-BackendRunning {
@@ -90,23 +134,51 @@ function Is-OverlayRunning {
 try {
     $pythonPath = Resolve-PythonPath
     $npmPath = Resolve-NpmPath
+    Write-LauncherLog "Launcher using Python: $pythonPath"
+
+    if (-not $DryRun) {
+        Test-PythonRuntime $pythonPath
+    }
 
     if (-not (Test-Path (Join-Path $repoRoot "frontend\dist\index.html"))) {
         Write-LauncherLog "Warning: frontend/dist is missing. Build frontend for production view."
     }
 
-    if (Is-BackendRunning) {
-        Write-LauncherLog "Backend already running. Skipping backend launch."
+    $backendReady = Test-BackendReady
+    if ($backendReady) {
+        Write-LauncherLog "Backend already ready at $backendUrl. Skipping backend launch."
+    } elseif (Is-BackendRunning) {
+        Write-LauncherLog "Backend process exists but is not ready. Waiting for $backendUrl."
+        if (-not $DryRun -and -not (Wait-ForBackendReady -TimeoutSeconds 30)) {
+            throw "Existing backend process did not become ready at $backendUrl. See data/backend.stderr.log."
+        }
+        $backendReady = $true
+        Write-LauncherLog "Backend ready at $backendUrl."
     } else {
         $backendOut = Join-Path $dataDir "backend.stdout.log"
         $backendErr = Join-Path $dataDir "backend.stderr.log"
-        Start-HiddenProcess `
+        $backendProcess = Start-HiddenProcess `
             -Name "backend" `
             -FilePath $pythonPath `
             -Arguments @("-m", "uvicorn", "backend.main:app", "--host", "127.0.0.1", "--port", "8000") `
             -WorkingDirectory $repoRoot `
             -StdOutPath $backendOut `
             -StdErrPath $backendErr
+
+        if (-not $DryRun -and -not (Wait-ForBackendReady -Process $backendProcess -TimeoutSeconds 30)) {
+            $stderrTail = if (Test-Path $backendErr) { (Get-Content $backendErr -Tail 10 | Out-String).Trim() } else { "No backend stderr log was created." }
+            Write-LauncherLog "Backend failed readiness check. stderr tail: $stderrTail"
+            throw "Backend did not become ready at $backendUrl."
+        }
+
+        $backendReady = $true
+        if (-not $DryRun) {
+            Write-LauncherLog "Backend ready at $backendUrl."
+        }
+    }
+
+    if (-not $backendReady -and -not $DryRun) {
+        throw "Overlay launch skipped because the backend is not ready."
     }
 
     if (Is-OverlayRunning) {