[BUG] error code 0x80073CF6 for Claude Desktop with Cowork on Windows 11.

Preflight Checklist

• [x] I have searched existing issues and this hasn't been reported yet
• [x] This is a single bug report (please file separate reports for different bugs)
• [x] I am using the latest version of Claude Code

What's Wrong?

Hey, I'm trying to install Claude Desktop with Cowork on Windows 11, but the installation fails with error code 0x80073CF6 (AddPackage failed). The installer completes but shows 'Installation failed' at the end. I've attached the diagnostic log from C:\Users\myuser\AppData\Local\Temp\ClaudeSetup.log

What I've tried:
Running as administrator
Windows Update is current
Restarting and retrying installation

System info:
Windows 11
Installing Claude Desktop with Cowork features
This gives the team the error code, what you've already tried, and context about your setup, which helps them investigate faster.

What Should Happen?

The thing is, it worked a couple of days back.

Error Messages/Logs

2026/06/16 10:23:45.141393 Log file: C:\Users\myuser\AppData\Local\Temp\ClaudeSetup.log
2026/06/16 10:23:45.141911 === Claude Setup 3df4fd263723119bc45f0af2d784afd5055e2ba9 started ===
2026/06/16 10:23:45.142943 AllowDevelopmentWithoutDevLicense found with value: 1
2026/06/16 10:23:45.142943 Windows edition: Core
2026/06/16 10:23:45.145000 Windows version: 10.0.26200
2026/06/16 10:23:45.145000 Native arch: x64
2026/06/16 10:23:45.145000 Elevation type: Limited
2026/06/16 10:23:45.145000 Is elevated: false
2026/06/16 10:23:45.145000 Sideloading enabled: true
2026/06/16 10:23:45.145000 S Mode: false
2026/06/16 10:23:45.145000 Conflicting service: false
2026/06/16 10:23:45.145000 Running in non-elevated context
2026/06/16 10:23:45.145000 User can elevate — installing MSIX directly
2026/06/16 10:23:45.158440 Splash: 400x300, 8 frame(s), animated=true
2026/06/16 10:23:45.158440 System DPI: 144 (scale: 150%)
2026/06/16 10:23:45.180656 MSIX URL: https://api.anthropic.com/api/desktop/win32/x64/msix/latest/redirect
2026/06/16 10:23:45.180656 Downloading MSIX to C:\Users\myuser\AppData\Local\Temp\Claude-1334156881.msix
2026/06/16 10:23:45.189818 proxy: WinHttpGetProxyForUrl("https://api.anthropic.com/api/desktop/win32/x64/msix/latest/redirect"): winapi error #12180
2026/06/16 10:23:45.397137 proxy: WinHttpGetProxyForUrl("https://downloads.claude.ai/releases/win32/x64/1.12603.1/Claude-3df4fd263723119bc45f0af2d784afd5055e2ba9.msix"): winapi error #12180
2026/06/16 10:23:48.005213 Download progress: 10% (23084880 / 230697820 bytes)
2026/06/16 10:23:50.679028 Download progress: 20% (46153376 / 230697820 bytes)
2026/06/16 10:23:53.245116 Download progress: 30% (69238256 / 230697820 bytes)
2026/06/16 10:23:55.928537 Download progress: 40% (92290368 / 230697820 bytes)
2026/06/16 10:23:58.551847 Download progress: 50% (115358864 / 230697820 bytes)
2026/06/16 10:24:01.309669 Download progress: 60% (138443744 / 230697820 bytes)
2026/06/16 10:24:03.825210 Download progress: 70% (161495856 / 230697820 bytes)
2026/06/16 10:24:06.579845 Download progress: 80% (184580736 / 230697820 bytes)
2026/06/16 10:24:09.091742 Download progress: 90% (207632848 / 230697820 bytes)
2026/06/16 10:24:11.818566 Download progress: 100% (230697820 / 230697820 bytes)
2026/06/16 10:24:11.819596 Download complete: 230697820 bytes, SHA256: 01777d6e38533e2b7a7454d21a65b23fb1264d8f5957613c6f44d5bc34b42f37
2026/06/16 10:24:11.820113 Download complete
2026/06/16 10:24:11.824338 Self-elevating: C:\Users\myuser\Downloads\Claude Setup.exe --elevated --msix-path "C:\Users\myuser\AppData\Local\Temp\Claude-1334156881.msix" --log-path "C:\Users\myuser\AppData\Local\Temp\ClaudeSetup.log"
2026/06/16 10:24:11.955639 Waiting for elevated process to complete...
2026/06/16 10:24:11.963800 Log file: C:\Users\myuser\AppData\Local\Temp\ClaudeSetup.log
2026/06/16 10:24:11.964312 === Claude Setup 3df4fd263723119bc45f0af2d784afd5055e2ba9 started ===
2026/06/16 10:24:11.964825 AllowDevelopmentWithoutDevLicense found with value: 1
2026/06/16 10:24:11.964825 Windows edition: Core
2026/06/16 10:24:11.965395 Windows version: 10.0.26200
2026/06/16 10:24:11.965395 Native arch: x64
2026/06/16 10:24:11.965395 Elevation type: Full
2026/06/16 10:24:11.965395 Is elevated: true
2026/06/16 10:24:11.965395 Sideloading enabled: true
2026/06/16 10:24:11.965395 S Mode: false
2026/06/16 10:24:11.965395 Conflicting service: false
2026/06/16 10:24:11.965395 Running in elevated context
2026/06/16 10:24:11.965395 Installing MSIX from C:\Users\myuser\AppData\Local\Temp\Claude-1334156881.msix (all-users: false)
2026/06/16 10:24:11.978938 Splash: 400x300, 8 frame(s), animated=true
2026/06/16 10:24:11.978938 System DPI: 144 (scale: 150%)
2026/06/16 10:24:12.004837 Verifying Authenticode signature on C:\Users\myuser\AppData\Local\Temp\Claude-1334156881.msix
2026/06/16 10:24:12.414989 WinVerifyTrust: MSIX signature is valid
2026/06/16 10:24:12.582331 Signature verified: MSIX signer matches bootstrapper
2026/06/16 10:24:12.582836 Extracted family name from MSIX manifest: Claude_pzs8sxrjxfjjc
2026/06/16 10:24:12.582836 Squirrel process prefix: c:\users\myuser\appdata\local\anthropicclaude\
2026/06/16 10:24:12.582836 Checking for running Squirrel Claude processes...
2026/06/16 10:24:12.588952 No Squirrel Claude processes found
2026/06/16 10:24:12.588952 Checking for existing Claude MSIX packages...
2026/06/16 10:24:12.600845 Installing MSIX: C:\Users\myuser\AppData\Local\Temp\Claude-1334156881.msix
2026/06/16 10:24:12.600845 Standard install (not split-account), using AddPackage
2026/06/16 10:24:12.600845 Installing via AddPackage (current-user)...
2026/06/16 10:24:20.854619 MSIX installation failed: AddPackage failed: AddPackage failed with HRESULT 0x80073CF6
2026/06/16 10:24:20.856123 ERROR dialog (opening log): Installation failed: AddPackage failed: AddPackage failed with HRESULT 0x80073CF6

Please share this log with us.
2026/06/16 10:25:08.011813 Elevated process exited with code 1
2026/06/16 10:25:08.011813 Elevation failed: elevated installer exited with code 1
2026/06/16 10:25:08.011813 ERROR dialog (with log path): Administrator access is required to install Claude with full features. You can try again or install without Cowork.
2026/06/16 10:48:55.450961 Log file: C:\Users\myuser\AppData\Local\Temp\ClaudeSetup.log
2026/06/16 10:48:55.450961 === Claude Setup 3df4fd263723119bc45f0af2d784afd5055e2ba9 started ===
2026/06/16 10:48:55.451981 AllowDevelopmentWithoutDevLicense found with value: 1
2026/06/16 10:48:55.451981 Windows edition: Core
2026/06/16 10:48:55.452501 Windows version: 10.0.26200
2026/06/16 10:48:55.452501 Native arch: x64
2026/06/16 10:48:55.452501 Elevation type: Full
2026/06/16 10:48:55.452501 Is elevated: true
2026/06/16 10:48:55.452501 Sideloading enabled: true
2026/06/16 10:48:55.452501 S Mode: false
2026/06/16 10:48:55.452501 Conflicting service: false
2026/06/16 10:48:55.452501 Running in non-elevated context
2026/06/16 10:48:55.452501 User can elevate — installing MSIX directly
2026/06/16 10:48:55.465885 Splash: 400x300, 8 frame(s), animated=true
2026/06/16 10:48:55.465885 System DPI: 144 (scale: 150%)
2026/06/16 10:48:55.489730 MSIX URL: https://api.anthropic.com/api/desktop/win32/x64/msix/latest/redirect
2026/06/16 10:48:55.489730 Downloading MSIX to C:\Users\myuser\AppData\Local\Temp\Claude-3560824000.msix
2026/06/16 10:48:55.497470 proxy: WinHttpGetProxyForUrl("https://api.anthropic.com/api/desktop/win32/x64/msix/latest/redirect"): winapi error #12180
2026/06/16 10:48:55.709492 proxy: WinHttpGetProxyForUrl("https://downloads.claude.ai/releases/win32/x64/1.12603.1/Claude-3df4fd263723119bc45f0af2d784afd5055e2ba9.msix"): winapi error #12180
2026/06/16 10:48:58.377290 Download progress: 10% (23084880 / 230697820 bytes)
2026/06/16 10:49:01.555871 Download progress: 20% (46153376 / 230697820 bytes)
2026/06/16 10:49:04.171396 Download progress: 30% (69221872 / 230697820 bytes)
2026/06/16 10:49:06.807182 Download progress: 40% (92290368 / 230697820 bytes)
2026/06/16 10:49:09.425237 Download progress: 50% (115375248 / 230697820 bytes)
2026/06/16 10:49:14.760856 Download progress: 60% (138427360 / 230697820 bytes)
2026/06/16 10:49:17.477124 Download progress: 70% (161512240 / 230697820 bytes)
2026/06/16 10:49:20.036987 Download progress: 80% (184564352 / 230697820 bytes)
2026/06/16 10:49:22.790520 Download progress: 90% (207632848 / 230697820 bytes)
2026/06/16 10:49:25.650945 Download progress: 100% (230697820 / 230697820 bytes)
2026/06/16 10:49:25.651454 Download complete: 230697820 bytes, SHA256: 01777d6e38533e2b7a7454d21a65b23fb1264d8f5957613c6f44d5bc34b42f37
2026/06/16 10:49:25.651973 Download complete
2026/06/16 10:49:25.657232 Self-elevating: C:\Users\myuser\Downloads\Claude Setup.exe --elevated --msix-path "C:\Users\myuser\AppData\Local\Temp\Claude-3560824000.msix" --log-path "C:\Users\myuser\AppData\Local\Temp\ClaudeSetup.log"
2026/06/16 10:49:25.697246 Waiting for elevated process to complete...
2026/06/16 10:49:25.705022 Log file: C:\Users\myuser\AppData\Local\Temp\ClaudeSetup.log
2026/06/16 10:49:25.705022 === Claude Setup 3df4fd263723119bc45f0af2d784afd5055e2ba9 started ===
2026/06/16 10:49:25.705543 AllowDevelopmentWithoutDevLicense found with value: 1
2026/06/16 10:49:25.706068 Windows edition: Core
2026/06/16 10:49:25.706068 Windows version: 10.0.26200
2026/06/16 10:49:25.706600 Native arch: x64
2026/06/16 10:49:25.706600 Elevation type: Full
2026/06/16 10:49:25.706600 Is elevated: true
2026/06/16 10:49:25.706600 Sideloading enabled: true
2026/06/16 10:49:25.706600 S Mode: false
2026/06/16 10:49:25.706600 Conflicting service: false
2026/06/16 10:49:25.706600 Running in elevated context
2026/06/16 10:49:25.706600 Installing MSIX from C:\Users\myuser\AppData\Local\Temp\Claude-3560824000.msix (all-users: false)
2026/06/16 10:49:25.720127 Splash: 400x300, 8 frame(s), animated=true
2026/06/16 10:49:25.720127 System DPI: 144 (scale: 150%)
2026/06/16 10:49:25.737910 Verifying Authenticode signature on C:\Users\myuser\AppData\Local\Temp\Claude-3560824000.msix
2026/06/16 10:49:26.145684 WinVerifyTrust: MSIX signature is valid
2026/06/16 10:49:26.312189 Signature verified: MSIX signer matches bootstrapper
2026/06/16 10:49:26.312691 Extracted family name from MSIX manifest: Claude_pzs8sxrjxfjjc
2026/06/16 10:49:26.312691 Squirrel process prefix: c:\users\myuser\appdata\local\anthropicclaude\
2026/06/16 10:49:26.312691 Checking for running Squirrel Claude processes...
2026/06/16 10:49:26.318368 No Squirrel Claude processes found
2026/06/16 10:49:26.318896 Checking for existing Claude MSIX packages...
2026/06/16 10:49:26.330271 Installing MSIX: C:\Users\myuser\AppData\Local\Temp\Claude-3560824000.msix
2026/06/16 10:49:26.330271 Standard install (not split-account), using AddPackage
2026/06/16 10:49:26.330271 Installing via AddPackage (current-user)...
2026/06/16 10:49:34.584702 MSIX installation failed: AddPackage failed: AddPackage failed with HRESULT 0x80073CF6
2026/06/16 10:49:34.584702 ERROR dialog (opening log): Installation failed: AddPackage failed: AddPackage failed with HRESULT 0x80073CF6

Please share this log with us.
2026/06/16 10:50:01.709300 Elevated process exited with code 1
2026/06/16 10:50:01.709300 Elevation failed: elevated installer exited with code 1
2026/06/16 10:50:01.709300 ERROR dialog (with log path): Administrator access is required to install Claude with full features. You can try again or install without Cowork.
2026/06/16 10:50:49.884428 Log file: C:\Users\myuser\AppData\Local\Temp\ClaudeSetup.log
2026/06/16 10:50:49.884428 === Claude Setup 3df4fd263723119bc45f0af2d784afd5055e2ba9 started ===
2026/06/16 10:50:49.884942 AllowDevelopmentWithoutDevLicense found with value: 1
2026/06/16 10:50:49.884942 Windows edition: Core
2026/06/16 10:50:49.885493 Windows version: 10.0.26200
2026/06/16 10:50:49.885493 Native arch: x64
2026/06/16 10:50:49.885493 Elevation type: Limited
2026/06/16 10:50:49.885493 Is elevated: false
2026/06/16 10:50:49.885493 Sideloading enabled: true
2026/06/16 10:50:49.885493 S Mode: false
2026/06/16 10:50:49.885493 Conflicting service: false
2026/06/16 10:50:49.885493 Running in non-elevated context
2026/06/16 10:50:49.885493 User can elevate — installing MSIX directly
2026/06/16 10:50:49.898639 Splash: 400x300, 8 frame(s), animated=true
2026/06/16 10:50:49.898639 System DPI: 144 (scale: 150%)
2026/06/16 10:50:49.922583 MSIX URL: https://api.anthropic.com/api/desktop/win32/x64/msix/latest/redirect
2026/06/16 10:50:49.923086 Downloading MSIX to C:\Users\myuser\AppData\Local\Temp\Claude-3184289115.msix
2026/06/16 10:50:49.930919 proxy: WinHttpGetProxyForUrl("https://api.anthropic.com/api/desktop/win32/x64/msix/latest/redirect"): winapi error #12180
2026/06/16 10:50:50.121087 proxy: WinHttpGetProxyForUrl("https://downloads.claude.ai/releases/win32/x64/1.12603.1/Claude-3df4fd263723119bc45f0af2d784afd5055e2ba9.msix"): winapi error #12180
2026/06/16 10:50:53.138697 Download progress: 10% (23084880 / 230697820 bytes)
2026/06/16 10:50:55.848105 Download progress: 20% (46153376 / 230697820 bytes)
2026/06/16 10:50:58.658250 Download progress: 30% (69221872 / 230697820 bytes)
2026/06/16 10:51:01.498863 Download progress: 40% (92290368 / 230697820 bytes)
2026/06/16 10:51:04.182830 Download progress: 50% (115358864 / 230697820 bytes)
2026/06/16 10:51:06.956881 Download progress: 60% (138427360 / 230697820 bytes)
2026/06/16 10:51:09.485996 Download progress: 70% (161495856 / 230697820 bytes)
2026/06/16 10:51:12.302829 Download progress: 80% (184580736 / 230697820 bytes)
2026/06/16 10:51:16.534497 Download progress: 90% (207632848 / 230697820 bytes)
2026/06/16 10:51:19.228680 Download progress: 100% (230697820 / 230697820 bytes)
2026/06/16 10:51:19.230733 Download complete: 230697820 bytes, SHA256: 01777d6e38533e2b7a7454d21a65b23fb1264d8f5957613c6f44d5bc34b42f37
2026/06/16 10:51:19.231248 Download complete
2026/06/16 10:51:19.240047 Self-elevating: C:\Users\myuser\Downloads\Claude Setup.exe --elevated --msix-path "C:\Users\myuser\AppData\Local\Temp\Claude-3184289115.msix" --log-path "C:\Users\myuser\AppData\Local\Temp\ClaudeSetup.log"
2026/06/16 10:51:19.346271 Waiting for elevated process to complete...
2026/06/16 10:51:19.353215 Log file: C:\Users\myuser\AppData\Local\Temp\ClaudeSetup.log
2026/06/16 10:51:19.353734 === Claude Setup 3df4fd263723119bc45f0af2d784afd5055e2ba9 started ===
2026/06/16 10:51:19.354284 AllowDevelopmentWithoutDevLicense found with value: 1
2026/06/16 10:51:19.354284 Windows edition: Core
2026/06/16 10:51:19.354808 Windows version: 10.0.26200
2026/06/16 10:51:19.354808 Native arch: x64
2026/06/16 10:51:19.354808 Elevation type: Full
2026/06/16 10:51:19.354808 Is elevated: true
2026/06/16 10:51:19.354808 Sideloading enabled: true
2026/06/16 10:51:19.354808 S Mode: false
2026/06/16 10:51:19.354808 Conflicting service: false
2026/06/16 10:51:19.354808 Running in elevated context
2026/06/16 10:51:19.354808 Installing MSIX from C:\Users\myuser\AppData\Local\Temp\Claude-3184289115.msix (all-users: false)
2026/06/16 10:51:19.368730 Splash: 400x300, 8 frame(s), animated=true
2026/06/16 10:51:19.368730 System DPI: 144 (scale: 150%)
2026/06/16 10:51:19.392318 Verifying Authenticode signature on C:\Users\myuser\AppData\Local\Temp\Claude-3184289115.msix
2026/06/16 10:51:19.801324 WinVerifyTrust: MSIX signature is valid
2026/06/16 10:51:19.965401 Signature verified: MSIX signer matches bootstrapper
2026/06/16 10:51:19.965915 Extracted family name from MSIX manifest: Claude_pzs8sxrjxfjjc
2026/06/16 10:51:19.965915 Squirrel process prefix: c:\users\myuser\appdata\local\anthropicclaude\
2026/06/16 10:51:19.965915 Checking for running Squirrel Claude processes...
2026/06/16 10:51:19.972260 No Squirrel Claude processes found
2026/06/16 10:51:19.972260 Checking for existing Claude MSIX packages...
2026/06/16 10:51:19.984668 Installing MSIX: C:\Users\myuser\AppData\Local\Temp\Claude-3184289115.msix
2026/06/16 10:51:19.984668 Standard install (not split-account), using AddPackage
2026/06/16 10:51:19.984668 Installing via AddPackage (current-user)...
2026/06/16 10:51:28.244929 MSIX installation failed: AddPackage failed: AddPackage failed with HRESULT 0x80073CF6
2026/06/16 10:51:28.244929 ERROR dialog (opening log): Installation failed: AddPackage failed: AddPackage failed with HRESULT 0x80073CF6

Please share this log with us.
2026/06/16 10:52:59.536887 Elevated process exited with code 1
2026/06/16 10:52:59.536887 Elevation failed: elevated installer exited with code 1
2026/06/16 10:52:59.536887 ERROR dialog (with log path): Administrator access is required to install Claude with full features. You can try again or install without Cowork.
2026/06/16 11:03:03.329358 Log file: C:\Users\myuser\AppData\Local\Temp\ClaudeSetup.log
2026/06/16 11:03:03.329358 === Claude Setup 3df4fd263723119bc45f0af2d784afd5055e2ba9 started ===
2026/06/16 11:03:03.330387 AllowDevelopmentWithoutDevLicense found with value: 1
2026/06/16 11:03:03.330387 Windows edition: Core
2026/06/16 11:03:03.330902 Windows version: 10.0.26200
2026/06/16 11:03:03.330902 Native arch: x64
2026/06/16 11:03:03.330902 Elevation type: Limited
2026/06/16 11:03:03.330902 Is elevated: false
2026/06/16 11:03:03.330902 Sideloading enabled: true
2026/06/16 11:03:03.330902 S Mode: false
2026/06/16 11:03:03.330902 Conflicting service: false
2026/06/16 11:03:03.330902 Running in non-elevated context
2026/06/16 11:03:03.330902 User can elevate — installing MSIX directly
2026/06/16 11:03:03.344342 Splash: 400x300, 8 frame(s), animated=true
2026/06/16 11:03:03.344342 System DPI: 144 (scale: 150%)
2026/06/16 11:03:03.366978 MSIX URL: https://api.anthropic.com/api/desktop/win32/x64/msix/latest/redirect
2026/06/16 11:03:03.366978 Downloading MSIX to C:\Users\myuser\AppData\Local\Temp\Claude-2732749234.msix
2026/06/16 11:03:03.374761 proxy: WinHttpGetProxyForUrl("https://api.anthropic.com/api/desktop/win32/x64/msix/latest/redirect"): winapi error #12180
2026/06/16 11:03:03.579472 proxy: WinHttpGetProxyForUrl("https://downloads.claude.ai/releases/win32/x64/1.12603.1/Claude-3df4fd263723119bc45f0af2d784afd5055e2ba9.msix"): winapi error #12180
2026/06/16 11:03:06.562852 Download progress: 10% (23084880 / 230697820 bytes)
2026/06/16 11:03:09.265867 Download progress: 20% (46153376 / 230697820 bytes)
2026/06/16 11:03:11.828021 Download progress: 30% (69221872 / 230697820 bytes)
2026/06/16 11:03:14.623469 Download progress: 40% (92290368 / 230697820 bytes)
2026/06/16 11:03:17.397488 Download progress: 50% (115358864 / 230697820 bytes)
2026/06/16 11:03:20.048289 Download progress: 60% (138427360 / 230697820 bytes)
2026/06/16 11:03:22.733762 Download progress: 70% (161495856 / 230697820 bytes)
2026/06/16 11:03:25.382597 Download progress: 80% (184580736 / 230697820 bytes)
2026/06/16 11:03:27.985664 Download progress: 90% (207632848 / 230697820 bytes)
2026/06/16 11:03:30.811650 Download progress: 100% (230697820 / 230697820 bytes)
2026/06/16 11:03:30.812230 Download complete: 230697820 bytes, SHA256: 01777d6e38533e2b7a7454d21a65b23fb1264d8f5957613c6f44d5bc34b42f37
2026/06/16 11:03:30.812744 Download complete
2026/06/16 11:03:30.826387 Self-elevating: C:\Users\myuser\Downloads\Claude Setup.exe --elevated --msix-path "C:\Users\myuser\AppData\Local\Temp\Claude-2732749234.msix" --log-path "C:\Users\myuser\AppData\Local\Temp\ClaudeSetup.log"
2026/06/16 11:03:30.936268 Waiting for elevated process to complete...
2026/06/16 11:03:30.943909 Log file: C:\Users\myuser\AppData\Local\Temp\ClaudeSetup.log
2026/06/16 11:03:30.943909 === Claude Setup 3df4fd263723119bc45f0af2d784afd5055e2ba9 started ===
2026/06/16 11:03:30.944955 AllowDevelopmentWithoutDevLicense found with value: 1
2026/06/16 11:03:30.944955 Windows edition: Core
2026/06/16 11:03:30.944955 Windows version: 10.0.26200
2026/06/16 11:03:30.944955 Native arch: x64
2026/06/16 11:03:30.944955 Elevation type: Full
2026/06/16 11:03:30.944955 Is elevated: true
2026/06/16 11:03:30.944955 Sideloading enabled: true
2026/06/16 11:03:30.944955 S Mode: false
2026/06/16 11:03:30.944955 Conflicting service: false
2026/06/16 11:03:30.944955 Running in elevated context
2026/06/16 11:03:30.945478 Installing MSIX from C:\Users\myuser\AppData\Local\Temp\Claude-2732749234.msix (all-users: false)
2026/06/16 11:03:30.959029 Splash: 400x300, 8 frame(s), animated=true
2026/06/16 11:03:30.959029 System DPI: 144 (scale: 150%)
2026/06/16 11:03:30.985365 Verifying Authenticode signature on C:\Users\myuser\AppData\Local\Temp\Claude-2732749234.msix
2026/06/16 11:03:31.395589 WinVerifyTrust: MSIX signature is valid
2026/06/16 11:03:31.561484 Signature verified: MSIX signer matches bootstrapper
2026/06/16 11:03:31.561988 Extracted family name from MSIX manifest: Claude_pzs8sxrjxfjjc
2026/06/16 11:03:31.561988 Squirrel process prefix: c:\users\myuser\appdata\local\anthropicclaude\
2026/06/16 11:03:31.561988 Checking for running Squirrel Claude processes...
2026/06/16 11:03:31.568199 No Squirrel Claude processes found
2026/06/16 11:03:31.568199 Checking for existing Claude MSIX packages...
2026/06/16 11:03:31.580582 Installing MSIX: C:\Users\myuser\AppData\Local\Temp\Claude-2732749234.msix
2026/06/16 11:03:31.581089 Standard install (not split-account), using AddPackage
2026/06/16 11:03:31.581089 Installing via AddPackage (current-user)...
2026/06/16 11:03:39.844207 MSIX installation failed: AddPackage failed: AddPackage failed with HRESULT 0x80073CF6
2026/06/16 11:03:39.844207 ERROR dialog (opening log): Installation failed: AddPackage failed: AddPackage failed with HRESULT 0x80073CF6

Please share this log with us.
2026/06/16 11:07:08.629036 Elevated process exited with code 1
2026/06/16 11:07:08.629036 Elevation failed: elevated installer exited with code 1
2026/06/16 11:07:08.629036 ERROR dialog (with log path): Administrator access is required to install Claude with full features. You can try again or install without Cowork.

Steps to Reproduce

Claude Desktop was previously installed and working on Windows 11
App stopped launching (approximately June 16, 2026)
Uninstalled Claude Desktop
Downloaded fresh installer
Ran installer as administrator
Installation proceeds to completion
Error appears: "Installation failed: AddPackage failed with HRESULT 0x80073CF6

Claude Model

None

Is this a regression?

Yes, this worked in a previous version

Last Working Version

Working as of approximately June 9, 2026 (one week ago). App stopped launching, so I uninstalled and attempted reinstall, which now fails with error 0x80073CF6.

Claude Code Version

Unable to determine (installation fails before app launches)

Platform

Anthropic API

Operating System

Windows

Terminal/Shell

PowerShell

Additional Information

<img width="319" height="184" alt="Image" src="https://github.com/user-attachments/assets/97345aad-84b5-45d8-8e03-13e8eb454b03" />