PreMessageSend hook event silently removed in v2.1.96 — breaks existing configs without warning

Description

Claude Code v2.1.96 (auto-updated via VSCode extension on 2026-04-08) silently removed PreMessageSend as a valid hook event. Existing configurations using this event now produce:

Settings file failed to parse: /path/to/.claude/settings.json — Invalid key in record. Permission rules and other settings from this file are not in effect.

This means ALL permissions and hooks in that settings file stop working — not just the invalid hook.

Steps to Reproduce

1. Have a working settings.json with a PreMessageSend hook (this worked in v2.1.92 and earlier):

{
  "hooks": {
    "PreMessageSend": [
      {
        "matcher": "*",
        "hooks": [
          {
            "type": "command",
            "command": "/path/to/script.sh"
          }
        ]
      }
    ]
  }
}

1. Claude Code auto-updates to v2.1.96
2. Restart VSCode
3. Error banner appears — entire settings file is rejected

Expected Behavior

• Minimum: A deprecation warning in a prior version before removing the event
• Better: A clear migration message naming the replacement event (UserPromptSubmit)
• Best: Automatic migration of PreMessageSend → UserPromptSubmit during the update, similar to how other settings migrations are handled

Workaround

Replace PreMessageSend with UserPromptSubmit in your settings files. UserPromptSubmit fires before Claude processes the prompt, which is the closest equivalent.

Additional Context

• The auto-update also created a new settings.json as part of a settings migration (file didn't exist before, was created at 08:37 after the extension updated at 08:24). The migration-generated file contained a permissions block that also triggered schema validation errors.
• PreMessageSend is not mentioned anywhere in the current hooks reference documentation — no deprecation notice, no mention in changelog.
• The valid hook events as of v2.1.96 are: SessionStart, InstructionsLoaded, UserPromptSubmit, PreToolUse, PermissionRequest, PostToolUse, PostToolUseFailure, Notification, SubagentStart, SubagentStop, Stop, PreCompact, SessionEnd.

Environment

• Claude Code: v2.1.96 (VSCode extension, auto-updated from v2.1.92)
• VSCode: Latest
• OS: macOS Tahoe 26.2 (Darwin 25.4.0, arm64)
• Previous working version: v2.1.92