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clr-activation-debugging

Diagnose .NET Framework CLR activation issues from mscoree.dll CLRLoad logs.

1|Updated May 21, 2026
Search Tags:#debugging#dotnet framework#mscoree#clrload logs#runtime activation#feature-on-demand#COM activation
One-click install
npx skills add https://github.com/1k-off/umbraco-observability-playground --skill clr-activation-debugging-1k-off
Or copy as Structured Prompt for Agent▼
Please help me install this Agent Skill.
Skill: clr-activation-debugging
Source: https://github.com/1k-off/umbraco-observability-playground/tree/main/.agents/skills/clr-activation-debugging
Command: npx skills add https://github.com/1k-off/umbraco-observability-playground --skill clr-activation-debugging-1k-off

SYSTEM DOCUMENTATION & REQUIREMENTS

💡 This Skill includes references (resource) components.

What problem does it solve?

This Skill helps you diagnose why a Windows process can’t activate the .NET Framework CLR correctly by analyzing CLR activation logs generated by mscoree.dll (CLRLoad logs).

Core Features & Use Cases

  • Decodes shim runtime selection decisions: identifies which CLR version the shim decided to load (or why it couldn’t), including capping/roll-forward behavior and config effects.
  • Explains Feature-on-Demand (FOD) behavior: determines whether NetFx3 installation was launched or suppressed and ties it to process error-mode (SEM_FAILCRITICALERRORS).
  • Handles multi-activation log complexity: guides you to distinguish nested activation sequences and focus on the specific activation that caused the symptom.
  • Common Use Cases: wrong CLR version chosen, FOD dialogs appearing (or not appearing) unexpectedly, COM activation failures, and scenarios where both v2 and v4 appear to be involved.

Quick Start

Use the clr-activation-debugging skill to analyze your CLRLoad logs for the failing process and determine which runtime the shim selected, why, and whether FOD was triggered.

Frequently Asked Questions about clr-activation-debugging

High-intent search queries and answers about installing and using this skill.

FAQPage Schema
Why does my .NET Framework application trigger a Feature-on-Demand installation prompt for .NET 3.5?▼

Feature-on-Demand prompts for .NET 3.5 are triggered when CLR activation fails to find a compatible runtime and the process error mode lacks SEM_FAILCRITICALERRORS, which otherwise suppresses the NetFx3 installation dialog.

How do I debug wrong CLR version selection during .NET Framework runtime activation?▼

Debug wrong CLR version selection by analyzing mscoree.dll CLRLoad logs to trace shim capping and roll-forward behavior, and verify config flags like supportedRuntime to see why a specific runtime was chosen.

What is the best way to diagnose COM activation failures involving legacy .NET Framework hosting paths?▼

Diagnose legacy COM activation failures by examining CLRLoad logs to distinguish nested activation sequences and validate useLegacyV2RuntimeActivationPolicy flags and activation entry points for the failing process.

Can I determine why the .NET Framework shim rejected a CLR version from mscoree logs?▼

Yes, you can determine shim rejection reasons by interpreting mscoree CLRLoad logs, which detail how capping, config flags, and supportedRuntime settings influenced the runtime selection or rejection.

How do I analyze multiple nested CLR activation sequences in CLRLoad logs?▼

Analyze nested CLR activation sequences by reviewing CLRLoad logs to distinguish each activation path, focusing on the specific shim decisions and entry points that caused the actual symptom.

What do I need to diagnose .NET Framework CLR activation issues using this approach?▼

You need CLRLoad log files generated by mscoree.dll for the failing process to validate supportedRuntime and useLegacyV2RuntimeActivationPolicy config flags, SEM_FAILCRITICALERRORS behavior, and activation entry points.

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