PreToolUse hook updatedInput has no effect on AskUserQuestion tool

[jeremy-newhouse]

Description

When a PreToolUse Python hook callback returns updatedInput for AskUserQuestion, the updated input is not reflected in the tool result that Claude sees. Claude continues as if no answer was provided.

Steps to Reproduce

async def ask_hook(hook_input, tool_use_id, hook_context):
    return {
        "hookSpecificOutput": {
            "hookEventName": "PreToolUse",
            "permissionDecision": "allow",
            "updatedInput": {"answer": "Jeremy"},  # This is ignored
        }
    }

options = ClaudeAgentOptions(
    permission_mode="bypassPermissions",
    cli_path="/home/tester/.local/bin/claude",
    hooks={
        "PreToolUse": [HookMatcher(matcher="AskUserQuestion", hooks=[ask_hook])],
    },
)

async for msg in query(prompt="Ask my name with AskUserQuestion, then greet me", options=options):
    if isinstance(msg, ResultMessage):
        print(msg.result)
        # Output: "It seems your answer didn't come through clearly!"
        # Expected: "Hello, Jeremy!"

Expected Behavior

updatedInput: {"answer": "Jeremy"} should replace the AskUserQuestion tool input, and Claude should see the answer in the tool result.

Workaround

Use permissionDecision: "deny" with the answer in permissionDecisionReason:

return {
    "hookSpecificOutput": {
        "hookEventName": "PreToolUse",
        "permissionDecision": "deny",
        "permissionDecisionReason": "The user has already provided their answer: Jeremy",
    }
}

Claude reads the denial reason and uses the answer correctly.

Environment

• claude-agent-sdk: 0.1.51
• Claude CLI: 2.1.86
• Python: 3.12
• OS: Linux (Docker)