Diagnostic script for slow npm run rayfin:dev on Windows

rayfin-slow-diagnostic.md

Diagnose Slow npm run rayfin:dev on Windows

You are diagnosing why npm run rayfin:dev (which runs rayfin dev) is extremely slow on this Windows machine. On another machine, the following two fixes brought startup from ~150s down to ~4s:

1. Windows Defender path exclusions — Defender real-time scanning of thousands of .js files in node_modules causes 100+ second delays on cold starts
2. Rayfin telemetry opt-out — RAYFIN_TELEMETRY_OPTOUT=1 as a persistent user env var, which prevents loading ~12,000 OpenTelemetry dependency files

Step 1: Run this diagnostic script

Run the following in PowerShell and share the full output:

Write-Host "=== DIAGNOSTIC REPORT ==="
Write-Host ""

# 1. Check telemetry opt-out
Write-Host "--- Telemetry Opt-Out ---"
Write-Host "Current session: RAYFIN_TELEMETRY_OPTOUT = $env:RAYFIN_TELEMETRY_OPTOUT"
Write-Host "Persisted (User): $([System.Environment]::GetEnvironmentVariable('RAYFIN_TELEMETRY_OPTOUT', 'User'))"
Write-Host ""

# 2. Check Defender status
Write-Host "--- Windows Defender ---"
Get-MpComputerStatus | Select-Object RealTimeProtectionEnabled, OnAccessProtectionEnabled | Format-List
Write-Host ""

# 3. Check Defender exclusions (requires admin — will show N/A if not admin)
Write-Host "--- Defender Exclusions ---"
try {
    $excl = (Get-MpPreference).ExclusionPath
    if ($excl) { $excl | ForEach-Object { Write-Host "  $_" } }
    else { Write-Host "  (none set)" }
} catch { Write-Host "  (requires admin to view)" }
Write-Host ""

# 4. Find Node/npm/rayfin locations
Write-Host "--- Tool Locations ---"
Write-Host "node: $((Get-Command node -ErrorAction SilentlyContinue).Source)"
Write-Host "npm:  $((Get-Command npm -ErrorAction SilentlyContinue).Source)"
Write-Host "rayfin: $((Get-Command rayfin -ErrorAction SilentlyContinue).Source)"
Write-Host "node version: $(node --version 2>&1)"
Write-Host "npm version: $(npm --version 2>&1)"
Write-Host ""

# 5. Count JS files rayfin must load (shows Defender scan scope)
Write-Host "--- Rayfin Dependency Size ---"
$rayfinParent = Split-Path (Get-Command rayfin -ErrorAction SilentlyContinue).Source
$rayfinModules = Join-Path $rayfinParent "node_modules\@microsoft\rayfin-cli\node_modules"
if (Test-Path $rayfinModules) {
    $count = (Get-ChildItem $rayfinModules -Recurse -Filter "*.js" -File).Count
    Write-Host "  JS files in rayfin deps: $count"
} else {
    Write-Host "  Could not find rayfin node_modules at: $rayfinModules"
}
Write-Host ""

# 6. Check project node_modules
Write-Host "--- Project node_modules ---"
Write-Host "  Exists: $(Test-Path node_modules)"
if (Test-Path node_modules) {
    $projCount = (Get-ChildItem node_modules -Recurse -Filter "*.js" -File).Count
    Write-Host "  JS files: $projCount"
}
Write-Host ""

# 7. Timing tests
Write-Host "--- Timing Tests ---"

Write-Host "node -e (baseline):"
$t0 = Measure-Command { node -e "console.log('ok')" 2>&1 }
Write-Host "  $($t0.TotalSeconds)s"

Write-Host "rayfin --version (run 1 - cold):"
$t1 = Measure-Command { rayfin --version 2>&1 }
Write-Host "  $($t1.TotalSeconds)s"

Write-Host "rayfin --version (run 2 - warm):"
$t2 = Measure-Command { rayfin --version 2>&1 }
Write-Host "  $($t2.TotalSeconds)s"

$variance = [math]::Round([math]::Abs($t1.TotalSeconds - $t2.TotalSeconds), 1)
Write-Host ""
Write-Host "Cold/warm variance: ${variance}s"
if ($variance -gt 10) {
    Write-Host "  WARNING: High variance suggests Defender is still scanning these files."
    Write-Host "  Defender exclusions are likely missing or not covering the right paths."
}
Write-Host ""

# 8. Check if both runs are still slow (>10s)
if ($t2.TotalSeconds -gt 10) {
    Write-Host "  WARNING: Even warm run is slow ($($t2.TotalSeconds)s)."
    Write-Host "  Possible causes: telemetry still on, corporate EDR, or slow network for telemetry flush."
}

Write-Host ""
Write-Host "=== END DIAGNOSTIC ==="

Step 2: Interpret the results

If RAYFIN_TELEMETRY_OPTOUT is not 1:

[System.Environment]::SetEnvironmentVariable("RAYFIN_TELEMETRY_OPTOUT", "1", "User")
$env:RAYFIN_TELEMETRY_OPTOUT = "1"

Then restart the terminal and re-run diagnostics.

If Defender exclusions are missing or don't cover the right paths:

Run in an admin PowerShell, using the actual paths from the "Tool Locations" section:

# Replace these paths with the actual ones from the diagnostic output
Add-MpPreference -ExclusionPath "C:\path\to\nodejs\node_modules"
Add-MpPreference -ExclusionPath "$env:LOCALAPPDATA\npm-cache"
Add-MpPreference -ExclusionPath "C:\path\to\your\project\repos"

Important: The exclusion paths must match where node, rayfin, and node_modules actually live on THIS machine. Use the paths from the diagnostic output — they may differ from the other machine.

If cold/warm variance is high (>10s) AFTER adding exclusions:

• The exclusion paths may not cover all directories being scanned
• There may be a corporate EDR (endpoint detection) tool running alongside Defender
• Check: Get-Process | Where-Object { $_.CPU -gt 10 } | Sort-Object CPU -Descending | Select-Object -First 10 Name, CPU, Id
• Look for EDR processes: CrowdStrike (csfalconservice), Carbon Black (cb), SentinelOne (SentinelAgent), etc.

If BOTH runs are slow (>10s) even with telemetry off:

• Rayfin CLI itself takes 3-5s baseline (normal)
• Check for network delays: Measure-Command { [System.Net.Dns]::GetHostAddresses("registry.npmjs.org") } | Select-Object TotalSeconds
• Check for corporate proxy: $env:HTTP_PROXY; $env:HTTPS_PROXY
• Check Docker status: docker info 2>&1 | Select-String "proxy|Server Version"

If project node_modules doesn't exist:

npm install

This is required for npm run scripts to resolve local binaries.