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RorySullivan1
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VSTO-maintenance

Diagnose and fix broken VSTO add-ins in Office environments.

Updated May 12, 2026
Search Tags:#troubleshooting#diagnostics#registry#office#addin#vsto#eventviewer
One-click install
npx skills add https://github.com/RorySullivan1/claudeBrain --skill vsto-maintenance
Or copy as Structured Prompt for Agent▼
Please help me install this Agent Skill.
Skill: VSTO-maintenance
Source: https://github.com/RorySullivan1/claudeBrain/tree/main/example-project/.claude/skills/VSTO-maintenance
Command: npx skills add https://github.com/RorySullivan1/claudeBrain --skill vsto-maintenance

SYSTEM DOCUMENTATION & REQUIREMENTS

What problem does it solve?

VSTO Maintenance addresses broken or failing VSTO add-ins by guiding triage, diagnosis, and remediation to restore stability after updates, migrations, or certificate changes.

Core Features & Use Cases

  • Systematic triage checklist covering Event Viewer analysis, LoadBehavior verification, and VSTO runtime validation.
  • Root cause workflows to identify and fix loading errors, crashes, or deprecation issues.
  • Use Case: When a user's Excel add-in stops loading after a 365 update, run the flow to determine whether the issue is signature trust, missing runtime, or corrupted registry data.

Quick Start

Run the VSTO maintenance flow on a target machine to begin diagnostics and remediation.

Frequently Asked Questions about VSTO-maintenance

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

FAQPage Schema
Why does my VSTO add-in fail to load after an Office update?▼

VSTO add-in loading errors after updates often stem from invalid LoadBehavior registry values, missing VSTO runtime, or untrusted certificates. Systematic triage checks Event Viewer logs and registry states to isolate the trigger.

How do I diagnose VSTO add-in crashes in Excel or Outlook?▼

Diagnose VSTO add-in crashes by applying root cause workflows to analyze Event Viewer errors, verify LoadBehavior in the registry, and validate the VSTO runtime presence. This identifies whether crashes originate from signature trust or corrupted registry data.

What does LoadBehavior in the registry mean for Office add-ins?▼

LoadBehavior is a registry value controlling whether an Office add-in loads automatically, on demand, or not at all. Verifying this value is a core diagnostic step when troubleshooting VSTO add-ins that fail to load or misbehave after migrations.

How do I fix a VSTO add-in that stopped working after a certificate change?▼

Fix VSTO add-ins after certificate changes by validating trusted certificates and checking Event Viewer for signature trust errors. The diagnostic workflow verifies if the runtime recognizes the new certificate to restore add-in stability.

Can I use this diagnostic flow for VSTO add-ins misbehaving after a migration?▼

Yes, the VSTO maintenance flow applies to add-ins misbehaving after migrations by applying root cause workflows. It verifies registry LoadBehavior, VSTO runtime presence, and trusted certificates to systematically triage and remediate loading failures.

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