VS Code agent `preToolUse` agent hook denial does not work

[springcomp]

Describe the bug

Running chat session from VS Code, I have installed a hook that denies specific commands.

Affected version

• VS Code 1.125.1
• GitHub Copilot Chat Extension v0.53.1

Steps to reproduce the behavior

.github/hooks/hooks.json

{
	"hooks": {
		"PreToolUse": [
			{
				"type": "command",
				"cwd": "src",
				"windows": "bin/Debug/net10.0/hook --tee requests.txt",
				"timeout": 15
			}
		]
	}
}

My hook.exe program parses the event hook and denies commands containing Get-Date from run_in_terminal tool. The --tee request.txt allows to pipe the STDIN request and dump the exit code and STDOUT response from the hook handler.

You can quickly re-create `hook.exe` as thus:

Program.cs

using System.Text.Json;
using System.Text.Json.Serialization;

var json = JsonSerializer.Serialize(new Response
{
  Continue = false,
  stopReason = "Tool call denied",
  hookSpecificOutput = new
  {
    permissionDecision = "deny",
    permissionDecisionReason = "Get-Date is a dangerous command",
  }
});
Console.WriteLine(json);
Environment.Exit(2);

class Response
{
  [JsonPropertyName("continue")]
  public bool Continue { get; set; } = default!;
  public string? stopReason { get; set; }
  public object hookSpecificOutput { get; set; } = default!;
}

Here is a simple session prompt:

Give me the latest powershell Get-Date

requests.txt

{"timestamp":"2026-06-20T09:02:23.792Z","hook_event_name":"PreToolUse","session_id":"189c9189-f1ea-4656-9b85-b5b31729ce41","transcript_path":"redacted.jsonl","tool_name":"run_in_terminal","tool_input":{"command":"Get-Date","explanation":"Print current date/time","goal":"Show current PowerShell date/time","mode":"sync"},"tool_use_id":"call_SCugVzemRWFMPYhoX6DKCdEE__vscode-1781945312345","cwd":"c:\\Projects\\springcomp\\hooks\\t\\src"}

requests_response.txt

2{"continue":false,"stopReason":"Tool call denied","systemMessage":null,"hookSpecificOutput":{"permissionDecision":"deny","permissionDecisionReason":"Get-Date is a dangerous command","updatedInput":null,"additionalContext":null,"hookEventName":"PreToolUse"}}

I tried everything:

• Exit code 2
• Response’s continue: false property
• Response’s hookSpecificOutput.permissionDecision: deny property

Still, the tool is called and never denied.

Expected behavior

The tool call SHOULD be denied.

Additional context

No response