$TOOL_INPUT_FILE_PATH for chat hooks doesn't work

[worthy7]

Describe the bug

https://code.visualstudio.com/docs/copilot/customization/hooks#_quick-start-your-first-hook

I tested the exact script provided there (prettier) and it complains
2026-05-10 19:33:34.811 [info] [#38] [PostToolUse] Output: [error] No parser and no file path given, couldn't infer a parser.

So I did a print of that variable, it doesn't seem to parse/pass correctly.

{
  "hooks": {
    "PostToolUse": [
      {
        "type": "command",
        "command": "echo \"file path is $TOOL_INPUT_FILE_PATH\"",
      }
    ]
  }
}

2026-05-10 20:24:19.441 [info] [#42] [PostToolUse] Output: file path is

Affected version

VS 1.119.0

Steps to reproduce the behavior

Literally https://code.visualstudio.com/docs/copilot/customization/hooks#_quick-start-your-first-hook
And then tell copilot to make an edit and watch the github copilot chat hooks output

Expected behavior

$TOOL_INPUT_FILE_PATH to be populated with the path of the file edited by copilot.

Additional context

No response