agent-debug-panel

type	skill
lifecycle	stable
inheritance	inheritable
name	agent-debug-panel
description	Debug skill/hook/agent loading issues using VS Code's Agent Debug Panel
tier	standard
applyTo	**/*debug*,**/*agent*,**/*skill*,**/*hook*,**/*instruction*
currency	"2026-04-20T00:00:00.000Z"

Agent Debug Panel

When a skill doesn't load or a hook doesn't fire, stop guessing — open the panel.

Quick Start

1. Open Command Palette (Ctrl+Shift+P)
2. Run: Developer: Open Agent Debug Panel
3. Start a chat with @alex or any agent
4. Watch real-time events flow through the panel

What the Panel Shows

Tab / Section	What You See	Debug Use
System Prompt Assembly	Full prompt sent to LLM including instructions, skills, context	Verify your instruction/skill was included
Tool Calls	Every tool invocation with arguments and results	Trace why a tool wasn't called or failed
Participant Resolution	Which chat participant handled the request	Confirm @alex routed correctly
Skill Loading	Which SKILL.md files were loaded and why	Debug "why didn't my skill activate?"
Instruction Matching	Which .instructions.md files matched via applyTo	Verify glob patterns work for your files
Hook Execution	Pre/post tool-use hook firing order and results	Debug hook failures or ordering issues
Agent Selection	Which .agent.md was selected and why	Verify agent routing logic

Common Debugging Scenarios

"My skill isn't being used"

1. Open Debug Panel → check Skill Loading section
2. Look for your skill name in the loaded list
3. If missing: check applyTo glob in SKILL.md frontmatter
4. If present but unused: the LLM chose not to use it — check skill description relevance

Common causes:

• applyTo glob doesn't match the active file
• Skill description doesn't match user's intent
• Another skill with higher relevance took priority
• Missing chat.agentSkillsLocations setting

"My instruction isn't applying"

1. Open Debug Panel → check Instruction Matching
2. Verify the .instructions.md file appears in matched list
3. If missing: check applyTo pattern in YAML frontmatter

Common causes:

• applyTo glob doesn't match current file type
• File is in wrong directory (must be in .github/instructions/)
• YAML frontmatter syntax error (missing --- delimiters)
• chat.instructionsFilesLocations not set to {".github/instructions": true}

"My hook didn't fire"

1. Open Debug Panel → check Hook Execution
2. Look for your hook event (preToolUse, postToolUse)
3. Check if hook script returned an error

Common causes:

• chat.hooks.enabled not set to true
• Hook script has syntax error (test with node --check script.js)
• Hook JSON references wrong file path
• Hook events array doesn't include the trigger event

"My agent isn't appearing"

1. Open Debug Panel → check Agent Selection
2. Verify .agent.md file is in .github/agents/
3. Check that chat.useAgentsMdFile is true

Common causes:

• File not named *.agent.md
• Not in .github/agents/ directory
• chat.useAgentsMdFile or chat.useNestedAgentsMdFiles not enabled
• YAML frontmatter has syntax errors

"System prompt is missing context"

1. Open Debug Panel → check System Prompt Assembly
2. Search for expected text from your instruction/skill
3. If missing: check the loading sections above

Useful: Copy the full system prompt to verify exactly what the LLM sees. Compare against what you expected.

Settings Checklist

Run these checks before opening the debug panel:

Setting	Required Value	Purpose
chat.agentSkillsLocations	[".github/skills"]	Skills discovery
chat.instructionsFilesLocations	{".github/instructions": true}	Instructions loading
chat.useAgentsMdFile	true	Agent file detection
chat.hooks.enabled	true	Hook execution
chat.plugins.enabled	true	Plugin loading
chat.useSkillAdherencePrompt	true	Forces LLM to read SKILL.md

Settings JSON

Add these to .vscode/settings.json:

{
  "chat.agentSkillsLocations": [".github/skills"],
  "chat.instructionsFilesLocations": {
    ".github/instructions": true
  },
  "chat.useAgentsMdFile": true,
  "chat.useNestedAgentsMdFiles": true,
  "chat.hooks.enabled": true,
  "chat.useSkillAdherencePrompt": true
}

Workflow: Systematic Debug

1. Reproduce the issue in chat
2. Open Debug Panel (Developer: Open Agent Debug Panel)
3. Check loading → matching → execution → output
4. Identify the break point
5. Fix the root cause (glob, setting, syntax)
6. Reproduce again to verify

Tips

• Leave the panel open during development — it updates in real-time
• Filter by event type when debugging specific issues
• Compare working vs. non-working — open two chats side-by-side
• Check settings first — 80% of "not loading" issues are missing settings
• The panel shows the exact same data VS Code uses internally — no guessing