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Error Loading Cefsharp.Core.Runtime.Dll

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I encountered an unexpected message on my laptop when attempting to run the latest version of ARC (version 12.30). The previous version, 12.29, worked without any issues. Can anyone help clarify what's happening here?

Error Details:

  • Timestamp: 2025-12-09 13:14:58 UTC
  • ARC Version: 2025.12.03.00
  • Operating System Version: Microsoft Windows NT 10.0.26100.0
  • Base Directory: C:\Program Files (x86)\Synthiam Inc\ARC by Synthiam\

Exception Information:

  • Exception Type: System.IO.FileNotFoundException
  • Message: Could not load file or assembly 'CefSharp.Core.Runtime.dll' or one of its dependencies. The specified module could not be found.
  • HResult: -2147024770
  • Source: CefSharp.Core
  • Target Site: Void .ctor()

Stack Trace:

at CefSharp.CefSettingsBase..ctor()
at CefSharp.WinForms.CefSettings..ctor() in C:\projects\cefsharp\CefSharp.WinForms\CefSettings.cs:line 16
at wYcbZm8UTFyhvM0AEqE.gU0keQ8o0lfJW91gswk.Fdr8XmwoLP()

It seems like there's an issue loading the 'CefSharp.Core.Runtime.dll' or one of its dependencies. Any suggestions on how to resolve this?


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PRO
USA
#1  

Ment to say latest ARC I tried to load and run was the 12.03 version. The 11.29 version worked perfectly fine.

Author Avatar
PRO
Canada
#2  

Thanks - good details. This is a common symptom when the Chromium/CefSharp native runtime or one of its native dependencies is missing or blocked after an ARC update. CefSharp.Core.Runtime.dll is a native C++/CEF component and requires Windows CRT/VC++ runtime DLLs and the CEF native files to be present.

Here’s a focused troubleshooting checklist (try in order):

  1. Confirm the DLL actually exists
  • Open Explorer to your ARC install folder (default): C:\Program Files (x86)\Synthiam Inc\ARC by Synthiam\
  • Search for CefSharp.Core.Runtime.dll (and CefSharp.*.dll)
  • Or run PowerShell:
    Get-ChildItem -Path "C:\Program Files (x86)\Synthiam Inc\ARC by Synthiam" -Filter "CefSharp.Core.Runtime.dll" -Recurse

If the file is missing go to step 2. If it exists go to step 3.

  1. Reinstall / Repair ARC 12.03
  • The quickest fix if installer didn’t deploy CEF native files correctly: download ARC 12.03 and run the installer as Administrator (right-click Run as administrator) and choose Repair/Install.
  • ARC Downloads: https://synthiam.com/Products/ARC
  • After reinstall, try launching ARC and opening the Chromium skill.
  1. Make sure Visual C++ runtimes are installed (very common cause)
  1. Check for antivirus / quarantine
  • Some AV products quarantine native DLLs after updates.
  • Check Windows Defender quarantine or your AV logs and restore/allow CefSharp.Core.Runtime.dll and related Cef files. Add an exclusion on the ARC install folder and try again.
  1. Find which dependency is actually failing (if the DLL is present but won’t load)
  • Use the modern "Dependencies" tool to inspect CefSharp.Core.Runtime.dll for missing dependencies: Dependencies (GitHub): https://github.com/lucasg/Dependencies/releases
  • Open CefSharp.Core.Runtime.dll with Dependencies and look for any red/missing modules (common misses: api-ms-win-crt-*.dll or MSVCP140.dll / VCRUNTIME140.dll).
  1. Windows updates / UCRT
  • If Dependencies shows missing api-ms-win-crt-runtime-l1-1-0.dll, you may need the Universal CRT which comes via Windows Update or via the Visual C++ redistributable above. Make sure Windows Update is current.
  1. Permissions / Run as Admin
  • Try running ARC as Administrator once to rule out permission errors.
  1. Check ARC debug logs
  • Since you have the Debug skill in your project, open it and copy the logged output (it may show more detail about missing modules). Paste the log or a screenshot if you want me to analyze it.

Additional notes

  • You said 11.29 worked and 12.03 fails - ARC may have updated to a newer CefSharp/CEF build that requires a newer redistributable or different native files. Reinstalling ARC 12.03 or installing the latest VC++ redistributable almost always resolves this.
  • Chromium skill manual: https://synthiam.com/Support/Skills/Display/Chromium?id=20391

If you want, I can:

  • Walk you through using Dependencies to identify the missing module (tell me whether you want step-by-step).
  • Interpret any output from the Debug skill or a Dependencies screenshot/log you paste here.

Quick checklist to try now:

  1. Search for CefSharp.Core.Runtime.dll in the ARC folder.
  2. Install Visual C++ Redistributable (x86 + x64) from Microsoft.
  3. Reinstall/repair ARC 12.03 as Administrator.
  4. Check AV quarantine and add exclusion for ARC folder.
  5. If still failing, run Dependencies on the DLL and paste the missing-module names or a screenshot.

Which of those steps have you already tried? Do you see the CefSharp.Core.Runtime.dll file in your ARC folder?


I am a customer support GPT-powered AI and still learning. If you have doubts about my response, please use the support documentation to verify my answer.
Author Avatar
PRO
USA
#3  

Looks like I did have to reinstall the x86 and x64 stuff as mentioned in step 3. Rebooted and ARC started normally. The only this I also did have to do was to put ARC on my windows taskbar again (the update had removed it) fyi , the lptop I am using is a Dell Latitude 7390 2-in-1 runninh Windows11 64 bit.

Author Avatar
PRO
Canada
#4  

Great - thanks for the update. Glad reinstalling the x86/x64 Visual C++ redistributables fixed it and ARC is launching again. A few quick notes and suggestions so this doesn’t surprise you next update, plus a couple of helpful links.

Why this happened (short):

  • Newer ARC builds update the Chromium/CefSharp runtime. Those native CEF binaries require the Microsoft Visual C++ runtime (UCRT / VC++ redistributables) to be present.
  • If the redistributables are missing, the CefSharp.Core.Runtime.dll will exist but fail to load, causing the FileNotFoundException you saw.
  • Reinstalling the x86 + x64 redistributables (and rebooting) is the usual fix - exactly what you did.

Recommendations and small tips

  • If you update ARC in the future, run the installer as Administrator (rightclick Run as administrator). That helps ensure native CEF files and dependencies are deployed correctly.
  • Keep Windows Update current - some CRT components are delivered by Windows updates.
  • If an update ever fails again, check your antivirus/quarantine and restore any quarantined CefSharp or CEF files. Then add an exclusion for the ARC install folder: C:\Program Files (x86)\Synthiam Inc\ARC by Synthiam\
  • If Chromium windows or pages don’t load after the fix, open the Debug skill (Project Add Skill General Debug) and copy any log lines here so I can help interpret them.

If you want to pin ARC back to the taskbar (quick):

  • Open Start, find "ARC by Synthiam" (or the ARC shortcut in the installation folder), right-click and choose "Pin to taskbar", or drag the ARC executable to the taskbar.

Helpful links

Follow-up:

  • Is Chromium now opening pages correctly in ARC 12.03 on your Dell Latitude 7390 2in1?
  • Would you like a quick stepbystep to use the Dependencies tool if this happens again?

I am a customer support GPT-powered AI and still learning. If you have doubts about my response, please use the support documentation to verify my answer.
Author Avatar
PRO
USA
#5  

Follow up-

  1. I am not using Chromium at the moment on this laptop (just the regular explorer)
  2. Would like the quick stepbystep of the Dependencies tool,should this happen again.
Author Avatar
PRO
Canada
#6  

Perfect - thanks for the follow up. Below is a concise, stepbystep guide to using the Dependencies tool to diagnose a failing native DLL load (like CefSharp.Core.Runtime.dll). I’ve included what to look for, common missing-dependency symptoms and fixes, and how to save/export the report so you can paste it here if you want me to analyze it.

  1. Download Dependencies
  • Go to: https://github.com/lucasg/Dependencies/releases
  • Download the latest ZIP for your OS (Dependencies_x64.zip and/or Dependencies_x86.zip). The x64 GUI runs on 64-bit Windows and can inspect both x86 and x64 DLLs, so prefer the x64 build on your Windows 11 laptop.
  • Extract the zip to a folder.
  1. Locate the suspect DLL in ARC
  • Default ARC install folder is: C:\Program Files (x86)\Synthiam Inc\ARC by Synthiam\
  • The file to inspect is: CefSharp.Core.Runtime.dll
  • If you can’t find it, run this PowerShell to search:
    Get-ChildItem -Path "C:\Program Files (x86)\Synthiam Inc\ARC by Synthiam" -Filter "CefSharp.Core.Runtime.dll" -Recurse
  1. Open the DLL in Dependencies
  • Run Dependencies.exe (use the x64 exe on your 64-bit machine).
  • File Open and point to CefSharp.Core.Runtime.dll in the ARC folder.
  • Dependencies will parse the native imports and show a tree of dependency DLLs on the right.
  1. Read the results - what indicates a problem
  • Missing modules are shown in red and/or labeled "MISSING" or "NOT FOUND".
  • Common missing items to watch for:
    • api-ms-win-crt-*.dll (Universal CRT) usually fixed by installing the Visual C++ Redistributable or Windows Update.
    • MSVCP140.dll, VCRUNTIME140.dll Visual C++ redistributable (2015/2017/2019/2022 unified).
    • cef_*.dll (CEF files like cef_sandbox.dll, libcef.dll) - if these are missing, the ARC installer didn’t deploy the CEF native files or an AV quarantined them.
    • icudtl.dat, icuin.dll, icuuc.dll - missing CEF runtime data/files.
  • Also check the "Architecture" column:
    • If CefSharp.Core.Runtime.dll is x86 but it references x64-only modules (or vice versa), that indicates an architecture mismatch. Make sure you’re examining the correct bitness of DLLs.
  1. How to identify the exact missing dependency
  • Click a red item in the dependency tree and look at the righthand panel for the path and status.
  • Expand children to see which imported function or library failed.
  • If you see a missing CRT or MSVCP/VCRUNTIME, that almost always points to the VC++ redistributable.
  1. Export / Save the report
  • File Save (or Save As) to create a text report of the dependency scan.
  • Attach or paste that text here and I’ll interpret it for you if you want.
  1. Quick fixes mapped to common missing items
  • api-ms-win-crt-*.dll or UCRT items:
  • MSVCP140.dll / VCRUNTIME140.dll:
    • Same VC++ redistributable link above (install both x86 and x64).
  • cef_sandbox.dll, libcef.dll, icudtl.dat, other cef_ files missing:
    • Reinstall/repair ARC (run installer as Administrator).
    • Check your antivirus/quarantine and restore any quarantined files. Add an exclusion for the ARC install folder.
  • Architecture mismatch:
    • Confirm which CefSharp DLL version ARC installed (x86 vs x64). Use the x64 Dependencies GUI to inspect both architectures. If ARC shipped x86 native CEF on x64 Windows, you still need the x86 VC++ redistributable present.
  1. Extra checks you might want to run
  • If Dependencies shows a missing module like api-ms-win-crt-l1-1-0.dll even after installing redistributables, reboot (some installs require reboot).
  • If AV has quarantined files, restore them and re-run ARC.
  • If you want to be thorough: open the ARC folder and ensure these CEF files are present (examples):
    • libcef.dll
    • cef_sandbox.dll
    • icudtl.dat
    • CefSharp.Core.Runtime.dll
    • CefSharp.dll
  1. If you want me to analyze the output
  • Save the Dependencies report (File Save) or copy/paste the red/missing lines here.
  • Or attach the text file output. I’ll interpret the exact missing items and give the next precise step.

Follow-up question: Would you like a step-by-step with screenshots, or do you want to export the Dependencies report and paste it here for me to analyze?


I am a customer support GPT-powered AI and still learning. If you have doubts about my response, please use the support documentation to verify my answer.
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