preToolUse: silent command rewrite via updatedInput — confirmation dialog appears even with permissionDecision: allow

[jeziellopes]

Summary

When a preToolUse hook rewrites a command using updatedInput with permissionDecision: allow, Copilot CLI v1.0.24 still shows an interactive confirmation dialog to the user on every rewritten command. There is currently no way for a hook to silently rewrite a command.

Environment

• Copilot CLI version: 1.0.24
• OS: Linux

Context

Consider a tool that automatically prepends a proxy prefix to dev commands (e.g. git status → proxy git status) to reduce LLM token consumption. Users install a preToolUse hook so the agent's commands are transparently rewritten without friction.

Before v1.0.24, updatedInput was not supported in Copilot CLI (#2013), so the hook used deny-with-suggestion as a workaround. When v1.0.24 shipped updatedInput support, the hook was upgraded to use updatedInput + permissionDecision: allow.

What I expected

A hook returning:

{
  "hookSpecificOutput": {
    "hookEventName": "PreToolUse",
    "permissionDecision": "allow",
    "permissionDecisionReason": "proxy auto-rewrite",
    "updatedInput": {
      "command": "proxy git status",
      "description": "check repo status"
    }
  }
}

should silently rewrite the command and run it — no confirmation needed, since:

1. The user explicitly installed the hook (opt-in)
2. permissionDecision is allow
3. The rewrite is mechanical (just prepending a proxy prefix)

What happened instead

Copilot CLI shows a confirmation dialog on every rewritten command:

╭─────────────────────────────────────────────────────╮
│ Hook permission request                             │
│ ⚠ proxy auto-rewrite                               │
│                                                     │
│  Tool: bash                                         │
│  Args: {"command": "proxy git status", ...}         │
│                                                     │
│ Do you want to allow this tool call?                │
╰─────────────────────────────────────────────────────╯

This dialog appears for every single command the agent runs that gets rewritten — making the hook more disruptive than the old deny-with-suggestion workaround.

Proposed solution

Add a way for hooks to indicate a rewrite should be applied silently. Options:

Option A — permissionDecision: allow should suppress the dialog (most intuitive):

If the hook already decided allow, no confirmation should be needed.

Option B — New field showConfirmation: false:

{
  "hookSpecificOutput": {
    "permissionDecision": "allow",
    "updatedInput": { ... },
    "showConfirmation": false
  }
}

Option C — New permissionDecision value "silent-allow" or "allow-silent"

Option A seems most consistent with the existing semantics — allow already means the hook approved it.

Impact

Without silent rewrite, updatedInput is not practical for high-frequency mechanical rewrites (like token optimization proxies). The old deny-with-suggestion workaround was less disruptive because denials are handled gracefully by the agent without surfacing a modal to the user.

cc @MRayermannMSFT (from #2013)