diff --git a/.gitignore b/.gitignore
index 08c27c0..9e04545 100644
--- a/.gitignore
+++ b/.gitignore
@@ -41,3 +41,7 @@ yarn-error.log*
 # typescript
 *.tsbuildinfo
 next-env.d.ts
+
+/edl/
+/qdl.js/
+/provisioning/
diff --git a/bun.lock b/bun.lock
index d76cbb6..55714d5 100644
--- a/bun.lock
+++ b/bun.lock
@@ -5,7 +5,7 @@
     "": {
       "name": "@commaai/flash",
       "dependencies": {
-        "@commaai/qdl": "git+https://github.com/commaai/qdl.js.git#21d7be79fa5178f253d32a0879bd8bdd4fa37e30",
+        "@commaai/qdl": "git+https://github.com/commaai/qdl.js.git#7177fde779bc6764727130969af1841d71a4c43c",
         "@fontsource-variable/inter": "^5.2.5",
         "@fontsource-variable/jetbrains-mono": "^5.2.5",
         "react": "^18.3.1",
@@ -81,7 +81,7 @@
 
     "@babel/types": ["@babel/types@7.28.5", "", { "dependencies": { "@babel/helper-string-parser": "^7.27.1", "@babel/helper-validator-identifier": "^7.28.5" } }, "sha512-qQ5m48eI/MFLQ5PxQj4PFaprjyCTLI37ElWMmNs0K8Lk3dVeOdNpB3ks8jc7yM5CDmVC73eMVk/trk3fgmrUpA=="],
 
-    "@commaai/qdl": ["@commaai/qdl@github:commaai/qdl.js#21d7be7", { "dependencies": { "@incognitojam/tiny-struct": "npm:@jsr/incognitojam__tiny-struct@^0.1.2", "arg": "^5.0.2", "crc-32": "^1.2.2", "fast-xml-parser": "^5.0.8", "usb": "^2.15.0" }, "peerDependencies": { "typescript": "^5.7.3" }, "bin": { "simg2img.js": "dist/bin/simg2img.js", "qdl.js": "dist/bin/qdl.js" } }, "commaai-qdl.js-21d7be7"],
+    "@commaai/qdl": ["@commaai/qdl@github:commaai/qdl.js#7177fde", { "dependencies": { "@incognitojam/tiny-struct": "npm:@jsr/incognitojam__tiny-struct@^0.1.2", "arg": "^5.0.2", "crc-32": "^1.2.2", "fast-xml-parser": "^5.0.8", "usb": "^2.15.0" }, "peerDependencies": { "typescript": "^5.7.3" }, "bin": { "simg2img.js": "dist/bin/simg2img.js", "qdl.js": "dist/bin/qdl.js" } }, "commaai-qdl.js-7177fde"],
 
     "@csstools/color-helpers": ["@csstools/color-helpers@5.1.0", "", {}, "sha512-S11EXWJyy0Mz5SYvRmY8nJYTFFd1LCNV+7cXyAgQtOOuzb4EsgfqDufL+9esx72/eLhsRdGZwaldu/h+E4t4BA=="],
 
diff --git a/deploy-preview.sh b/deploy-preview.sh
index fc035f6..9716b66 100755
--- a/deploy-preview.sh
+++ b/deploy-preview.sh
@@ -3,6 +3,7 @@ set -e
 
 BRANCH="${1:-$(git branch --show-current)}"
 
+bun install
 bun run build
 bunx wrangler pages deploy dist --project-name=connect --branch="$BRANCH"
 
diff --git a/package.json b/package.json
index 73aed3a..adaa696 100644
--- a/package.json
+++ b/package.json
@@ -13,7 +13,7 @@
     "node": ">=20.11.0"
   },
   "dependencies": {
-    "@commaai/qdl": "git+https://github.com/commaai/qdl.js.git#21d7be79fa5178f253d32a0879bd8bdd4fa37e30",
+    "@commaai/qdl": "git+https://github.com/commaai/qdl.js.git#7177fde779bc6764727130969af1841d71a4c43c",
     "@fontsource-variable/inter": "^5.2.5",
     "@fontsource-variable/jetbrains-mono": "^5.2.5",
     "react": "^18.3.1",
diff --git a/src/app/Flash.jsx b/src/app/Flash.jsx
index 0732474..fa836b1 100644
--- a/src/app/Flash.jsx
+++ b/src/app/Flash.jsx
@@ -1,6 +1,6 @@
 import { useEffect, useRef, useState } from 'react'
 
-import { FlashManager, StepCode, ErrorCode, DeviceType } from '../utils/manager'
+import { FlashManager, StepCode, ErrorCode, DeviceType, DUMP_GPT_MODE } from '../utils/manager'
 import { useImageManager } from '../utils/image'
 import { isLinux, isWindows } from '../utils/platform'
 import config from '../config'
@@ -517,6 +517,91 @@ function LinuxUnbind({ onNext }) {
   )
 }
 
+// GPT Dump diagnostic mode
+function GptDumpMode({ qdlManager, imageManager }) {
+  const [gptDump, setGptDump] = useState(null)
+  const [loading, setLoading] = useState(false)
+  const [copied, setCopied] = useState(false)
+  const [ready, setReady] = useState(false)
+
+  useEffect(() => {
+    if (!imageManager.current) return
+    fetch(config.loader.url)
+      .then((res) => res.arrayBuffer())
+      .then((programmer) => {
+        qdlManager.current = new FlashManager(programmer, {})
+        qdlManager.current.initialize(imageManager.current).then(() => setReady(true))
+      })
+  }, [imageManager.current])
+
+  const handleDump = async () => {
+    setLoading(true)
+    const result = await qdlManager.current.dumpGpt()
+    setGptDump(result)
+    setLoading(false)
+  }
+
+  const handleCopy = () => {
+    navigator.clipboard.writeText(gptDump)
+    setCopied(true)
+    setTimeout(() => setCopied(false), 2000)
+  }
+
+  return (
+    <div className="flex flex-col items-center justify-center h-full gap-6 p-8">
+      <div className="text-center">
+        <h1 className="text-3xl font-bold mb-2">GPT Diagnostic Mode</h1>
+        <p className="text-xl text-gray-600">
+          Connect your device to dump partition table info
+        </p>
+      </div>
+
+      {!gptDump ? (
+        <button
+          onClick={handleDump}
+          disabled={loading || !ready}
+          className={`px-8 py-3 text-xl font-semibold rounded-full transition-colors ${
+            loading || !ready
+              ? 'bg-gray-300 text-gray-500 cursor-not-allowed'
+              : 'bg-[#51ff00] hover:bg-[#45e000] active:bg-[#3acc00] text-black'
+          }`}
+        >
+          {loading ? 'Reading...' : !ready ? 'Initializing...' : 'Connect & Dump GPT'}
+        </button>
+      ) : (
+        <>
+          <textarea
+            readOnly
+            value={gptDump}
+            className="w-full max-w-3xl h-96 p-4 font-mono text-sm bg-gray-900 text-gray-100 rounded-lg"
+          />
+          <div className="flex gap-4">
+            <button
+              onClick={handleCopy}
+              className="px-6 py-2 text-lg font-semibold rounded-full bg-blue-600 hover:bg-blue-500 text-white transition-colors"
+            >
+              {copied ? 'Copied!' : 'Copy to Clipboard'}
+            </button>
+            <button
+              onClick={() => setGptDump(null)}
+              className="px-6 py-2 text-lg font-semibold rounded-full bg-gray-300 hover:bg-gray-400 text-black transition-colors"
+            >
+              Dump Again
+            </button>
+          </div>
+          <p className="text-gray-500">
+            Send this to{' '}
+            <a href="https://discord.comma.ai" target="_blank" rel="noopener noreferrer" className="text-blue-500 hover:underline">
+              Discord
+            </a>
+            {' '}for debugging
+          </p>
+        </>
+      )}
+    </div>
+  )
+}
+
 // WebUSB connection screen - shows while waiting for user to select device
 function WebUSBConnect({ onConnect }) {
   return (
@@ -722,6 +807,11 @@ export default function Flash() {
   // Handle retry on error
   const handleRetry = () => window.location.reload()
 
+  // Render GPT dump diagnostic mode
+  if (DUMP_GPT_MODE) {
+    return <GptDumpMode qdlManager={qdlManager} imageManager={imageManager} />
+  }
+
   // Render landing page
   if (wizardScreen === 'landing' && !error) {
     return (
diff --git a/src/utils/manager.js b/src/utils/manager.js
index 618ff8d..496c973 100644
--- a/src/utils/manager.js
+++ b/src/utils/manager.js
@@ -5,6 +5,9 @@ import { getManifest } from './manifest'
 import config from '../config'
 import { createSteps, withProgress } from './progress'
 
+// Diagnostic mode - dump GPT partition info
+export const DUMP_GPT_MODE = new URLSearchParams(window.location.search).has('dump_gpt')
+
 // Fast mode for development - skips flashing system partition (the slowest)
 // Enable with ?fast=1 in URL
 const FAST_MODE = new URLSearchParams(window.location.search).has('fast')
@@ -392,17 +395,17 @@ export class FlashManager {
 
     try {
       for await (const image of systemImages) {
-        const [onDownload, onFlash] = createSteps([1, image.hasAB ? 2 : 1], this.#setProgress.bind(this))
+        // Flash system to slot A only (large, slow), other A/B partitions to both slots
+        const flashBothSlots = image.hasAB && image.name !== 'system'
+        const [onDownload, onFlash] = createSteps([1, flashBothSlots ? 2 : 1], this.#setProgress.bind(this))
 
         this.#setMessage(`Downloading ${image.name}`)
         await this.imageManager.downloadImage(image, onDownload)
         const blob = await this.imageManager.getImage(image)
         onDownload(1.0)
 
-        // Flash image to each slot
-        const slots = image.hasAB ? ['_a', '_b'] : ['']
+        const slots = flashBothSlots ? ['_a', '_b'] : (image.hasAB ? ['_a'] : [''])
         for (const [slot, onSlotProgress] of withProgress(slots, onFlash)) {
-          // NOTE: userdata image name does not match partition name
           const partitionName = `${image.name.startsWith('userdata_') ? 'userdata' : image.name}${slot}`
 
           this.#setMessage(`Flashing ${partitionName}`)
@@ -424,10 +427,14 @@ export class FlashManager {
     this.#setProgress(-1)
     this.#setMessage('Finalizing...')
 
-    // Set bootable LUN and update active partitions
-    if (!await this.device.setActiveSlot('a')) {
-      console.error('[Flash] Failed to update slot')
+    // Set bootable LUN to slot A (LUN 1)
+    // GPT images already have correct A/B flags, no need to manipulate them
+    try {
+      await this.device.setBootableLun(1)
+    } catch (err) {
+      console.error('[Flash] Failed to set bootable LUN', err)
       this.#setError(ErrorCode.FINALIZING_FAILED)
+      return
     }
 
     // Reboot the device
@@ -459,4 +466,85 @@ export class FlashManager {
     await this.#finalize()
     console.info(`Finalized in ${((performance.now() - start) / 1000).toFixed(2)}s`)
   }
+
+  /**
+   * Diagnostic mode: connect and dump GPT from all LUNs
+   * @returns {Promise<string|null>} Formatted GPT dump or null on error
+   */
+  async dumpGpt() {
+    this.#setStep(StepCode.CONNECTING)
+    this.#setProgress(-1)
+
+    let usb
+    try {
+      usb = new usbClass()
+    } catch (err) {
+      console.error('[Flash] Connection error', err)
+      this.#setError(ErrorCode.LOST_CONNECTION)
+      return null
+    }
+
+    try {
+      await this.device.connect(usb)
+    } catch (err) {
+      if (err.name === 'NotFoundError') {
+        console.info('[Flash] No device selected')
+        this.#setStep(StepCode.READY)
+        return null
+      }
+      console.error('[Flash] Connection error', err)
+      this.#setError(ErrorCode.LOST_CONNECTION)
+      return null
+    }
+
+    this.#setConnected(true)
+    this.#setMessage('Reading GPT...')
+
+    try {
+      const lines = []
+      lines.push('=== GPT Dump ===')
+      lines.push(`Time: ${new Date().toISOString()}`)
+      lines.push('')
+
+      // Get storage info
+      const storageInfo = await this.device.getStorageInfo()
+      lines.push('Storage Info:')
+      lines.push(JSON.stringify(storageInfo, null, 2))
+      lines.push('')
+
+      // Dump GPT from each LUN
+      for (let lun = 0; lun < 6; lun++) {
+        lines.push(`=== LUN ${lun} ===`)
+        try {
+          const gpt = await this.device.getGpt(lun)
+          const partitions = gpt.getPartitions()
+
+          for (const part of partitions) {
+            const isAB = part.name.endsWith('_a') || part.name.endsWith('_b')
+            let line = `${part.name}: ${part.attributes}`
+
+            if (isAB) {
+              // Parse A/B flags from attributes
+              const attrs = BigInt(part.attributes)
+              // Flags are at bits 48-55 (correct) or 54-61 (buggy)
+              const flags48 = (attrs >> 48n) & 0xFFFFn
+              const flags54 = (attrs >> 54n) & 0xFFFFn
+              line += ` [bit48: 0x${flags48.toString(16)}, bit54: 0x${flags54.toString(16)}]`
+            }
+            lines.push(line)
+          }
+        } catch (err) {
+          lines.push(`Error reading LUN ${lun}: ${err.message}`)
+        }
+        lines.push('')
+      }
+
+      this.#setStep(StepCode.DONE)
+      return lines.join('\n')
+    } catch (err) {
+      console.error('[Flash] Error dumping GPT', err)
+      this.#setError(ErrorCode.UNKNOWN)
+      return null
+    }
+  }
 }