Shipped agent.md frontmatter hooks block is dead code: relative script paths, never scaffolded, not executed by any current host

plugins/modernize-java/com.github.copilot/agents/modernize-java.agent.md から始め、issue で説明されている plugin payload と合わせて hooks frontmatter を調査します。出荷される hook carrier または script のいずれかがこれらのコマンドを提供しているか確認します。定義が機能しない hooks を宣伝しなくなっているか、参照されている scripts がパッケージ化され、有効な install-root パスを使用していれば完了です。

The hooks: frontmatter block in plugins/modernize-java/com.github.copilot/agents/modernize-java.agent.md is inherited from the VS Code extension era of this tooling. In the current plugin distribution it is dead code on every host, and the scripts it references are not provisioned anywhere.

What ships today (verbatim frontmatter block)

hooks:
  UserPromptSubmit:
    - type: command
      command: APPMOD_AGENT=modernize-java-upgrade bash "$APPMOD_HOOK_SCRIPTS_DIR/sendTelemetry.sh"
      windows: "powershell -ExecutionPolicy Bypass -NonInteractive -Command \"& (Join-Path $env:APPMOD_HOOK_SCRIPTS_DIR 'sendTelemetry.ps1') -AgentName modernize-java-upgrade\""
  SubagentStart:
    - type: command
      command: APPMOD_AGENT=modernize-java-upgrade bash "$APPMOD_HOOK_SCRIPTS_DIR/sendTelemetry.sh"
      windows: "powershell -ExecutionPolicy Bypass -NonInteractive -Command \"& (Join-Path $env:APPMOD_HOOK_SCRIPTS_DIR 'sendTelemetry.ps1') -AgentName modernize-java-upgrade\""
  SubagentStop:
    - type: command
      command: APPMOD_AGENT=modernize-java-upgrade bash "$APPMOD_HOOK_SCRIPTS_DIR/sendTelemetry.sh"
      windows: "powershell -ExecutionPolicy Bypass -NonInteractive -Command \"& (Join-Path $env:APPMOD_HOOK_SCRIPTS_DIR 'sendTelemetry.ps1') -AgentName modernize-java-upgrade\""
  ErrorOccurred:
    - type: command
      command: APPMOD_AGENT=modernize-java-upgrade bash "$APPMOD_HOOK_SCRIPTS_DIR/sendTelemetry.sh"
      windows: "powershell -ExecutionPolicy Bypass -NonInteractive -Command \"& (Join-Path $env:APPMOD_HOOK_SCRIPTS_DIR 'sendTelemetry.ps1') -AgentName modernize-java-upgrade\""
  PostToolUse:
    - type: command
      command: "bash .github/modernize/java-upgrade/hooks/scripts/recordToolUse.sh"
      windows: "powershell -NonInteractive -File .github/modernize/java-upgrade/hooks/scripts/recordToolUse.ps1"

Why the block is dead

1. The Copilot CLI does not read it. The CLI's documented hook carriers are settings hooks.*, repo-level .github/hooks/*.json, user-level ~/.copilot/hooks/*.json, and plugin-level hooks/hooks.json — and this plugin ships no hooks/hooks.json. The frontmatter schema the CLI's runtime (checked against the shipped bytes of 1.0.83 and 1.0.86) parses for these definition files has no hooks field; unknown frontmatter fields are ignored.
2. The referenced scripts do not exist. The plugin payload is three files — plugin.json, mcp.json, and the .md itself. Nothing in the repo, the plugin install, or the MCP package ever creates .github/modernize/java-upgrade/hooks/scripts/ in the workspace: in @microsoft/github-copilot-app-modernization-mcp-server@1.24.0, recordToolUse and the hook path occur only inside the package's own .agent.md templates, with no writer.
3. The telemetry legs' variable is never set here. $APPMOD_HOOK_SCRIPTS_DIR is provided by the VS Code extension's hook environment, which is not part of this distribution, so the four sendTelemetry commands cannot resolve their scripts either.

Observed behavior

• Plugin modernize-java@modernize-java v1.24.0, installed from this repo's marketplace (copilot plugin marketplace add microsoft/modernize-java, then copilot plugin install modernize-java@modernize-java): running a read+edit with a marker script planted at the exact hook path (both the .sh and the .ps1 leg) produced zero executions across 3 runs, while user-level hooks (~/.copilot/hooks/*.json) fired in the very same runs — session debug logs confirm the plugin's instructions were loaded and at least 3 tool uses completed per run (invoked with --agent modernize-java:modernize-java). A repo-level .github/hooks/postToolUse.json also executed once its documented opt-in was set. The hooks engine is fully live on the documented carriers; the frontmatter block is simply not one of them.
• The shipped PostToolUse command run verbatim in a clean workspace exits 127 with no visible diagnostic anywhere: bash: .github/modernize/java-upgrade/hooks/scripts/recordToolUse.sh: No such file or directory.

Why this is worth cleaning up

• Five hook events silently ignore-or-fail on every session; the block reads as if tool-usage telemetry were configured, but it has never recorded anything in this distribution.
• If any host adds frontmatter hooks support, the shipped commands become live immediately — and they resolve their scripts relative to the session's working directory (the opened workspace), not the plugin's install root. A file committed to a repository at .github/modernize/java-upgrade/hooks/scripts/recordToolUse.sh would then be executed by the hook machinery on every tool use (the shipped command demonstrably executes a file planted at that relative path when run as-is; a copy placed only on PATH does not resolve). VS Code's experimental hooks support for custom chat participants already reads this exact frontmatter shape today, gated behind preview flags and workspace trust — so the gap between "ignored" and "live workspace-relative execution" is one host-side change.

Related: github/copilot-cli#3659 ("CLI cannot execute hooks shipped with plugins") covers the relative-path resolution problem on the documented JSON carrier; this issue is about the dead block shipped in this repo.

Suggested fix

Either of:

• strip the hooks: block from the definition file (nothing in this distribution provisions the scripts it names), or
• ship the hook scripts inside the plugin and reference them from the install root (${PLUGIN_ROOT}-style) instead of a workspace-relative path.

Environment: Windows 11, Copilot CLI 1.0.83 (runtime source checked at 1.0.83 and 1.0.86), plugin v1.24.0, repo at b02350da (2026-09-20).