CLI cannot execute hooks shipped with plugins

[brandonh-msft]

Describe the bug

As of 1.0.57, I am unable to issue any prompts to GHCP CLI w/o them failing on preToolUse hook exceptions.

Logs show myriad failures like:

2026-06-03T18:51:15.906Z [DEBUG] [hook stderr] The argument '.github/hooks/governance-audit/audit-session-start.ps1' is not recognized as the name of a script file. Check the spelling of the name, or if a path was included, verify that the path is correct and try again.
2026-06-03T18:51:15.907Z [DEBUG] [hook stdout] 
Usage: pwsh[.exe] [-Login] [[-File] <filePath> [args]]
                  [-Command { - | <script-block> [-args <arg-array>]
                                | <string> [<CommandParameters>] } ]
                  [-CommandWithArgs <string> [<CommandParameters>]
                  [-ConfigurationName <string>] [-ConfigurationFile <filePath>]
                  [-CustomPipeName <string>] [-EncodedCommand <Base64EncodedCommand>]
                  [-ExecutionPolicy <ExecutionPolicy>] [-InputFormat {Text | XML}]
                  [-Interactive] [-MTA] [-NoExit] [-NoLogo] [-NonInteractive] [-NoProfile]
                  [-NoProfileLoadTime] [-OutputFormat {Text | XML}]
                  [-SettingsFile <filePath>] [-SSHServerMode] [-STA]
                  [-Version] [-WindowStyle <style>]
                  [-WorkingDirectory <directoryPath>]

       pwsh[.exe] -h | -Help | -? | /?

PowerShell Online Help https://aka.ms/powershell-docs

All parameters are case-insensitive.
2026-06-03T18:51:16.068Z [ERROR] Hook execution failed: HookExitCodeError: Hook command failed with code 1

across numerous hook files.

Affected version

1.0.57+

Steps to reproduce the behavior

Install one or more plugins (which ship hooks as part of their functionality) into the CLI.
Send a prompt to the CLI with the plugin active & loaded

Expected behavior

Prompt is processed

Additional context

I have my Copilot Home and cache dirs set to my dev drive (d:\.copilot and d:\.copilot\cache, respectively)

[brandonh-msft]

The root of this issue appears to be in the way plugins ship hooks and hooks get invoked by the CLI.

E.g. consider a plugin marketplace repo like:

.github
  plugin
    marketplace.json
plugins
  example-plugin
    .github
      hooks
        example-hook
          my-script.ps1
      plugin
        hooks.json

where the hooks.json would have a definition to point to something in the example-hook like:

{
  "version": 1,
  "hooks": {
    "sessionStart": [
      {
        "type": "command",
        "powershell": "pwsh -NoProfile -ExecutionPolicy Bypass -File .github/hooks/example-hook/my-script.ps1",
        "cwd": ".",
        "env": {
          "ENV_VAR": "sample_value"
        },
        "timeoutSec": 10
      }
    ]
  }
}

on session start, with this plugin active, the CLI:

• reads the hooks.json
• attempts to invoke the hook based on the path in the plugin which, of course, fails because the plugin - once installed into GHCP CLI - lives at $COPILOT_HOME/cache/marketplaces/<repo-slug>/plugins/example-plugin so it won't find the hook at simply .github/hooks/... resulting in the cited "not found" exception.

[brandonh-msft]

I tried removing the cwd property to no avail.

[brandonh-msft]

Setting cwd to ${PLUGIN_ROOT} (an as-yet-undocumented env var injected at runtime) appears to solve the problem.

Suggested fix(es):

• Document PLUGIN_ROOT
• Make it the default if cwd is not specified in the JSON (I tried removing it altogether and execution still failed)