Hook Valid Event Types

Hook event keys in .github/hooks/*.json or VS Code hook config MUST use recognized Copilot event type names. The VS Code Copilot doc lists eight events in PascalCase: SessionStart, UserPromptSubmit, PreToolUse, PostToolUse, PreCompact, SubagentStart, SubagentStop, Stop. Unrecognized event names — including camelCase variants like preToolUse — are silently ignored, so the hook never fires.

Antipatterns

• camelCase variants. Writing preToolUse, sessionStart, or userPromptSubmitted — Copilot's event names are uniformly PascalCase, and the camelCase aliases are not recognized.
• Cross-agent event names. Using event names from another agent (e.g., SessionEnd is a Claude/Cursor event, not a Copilot one).
• Deprecated event names. Using event names from older versions that have been renamed or removed.

Pass / Fail

Pass

{
  "hooks": {
    "SessionStart": [{ "type": "command", "command": "echo hook" }]
  }
}

Fail

{
  "hooks": {
    "onToolUse": [{ "type": "command", "command": "echo hook" }]
  }
}

Limitations

Checks that at least one recognized Copilot event type is present. Does not detect misspelled event names if a valid one also exists.