How to hook the FallbackIntent

Question

A simple question ... I've built a bot and successfully hooked to a lambda during building the bot alias:
```
...
    botAliasLocaleSettings {
        en_GB {
            codeHookSpecification: {
                lambdaCodeHook: {
                    codeHookInterfaceVersion: "1.0",
                    lambdaARN: lambdaArn
                },
                enabled: true
            };
...
```
This turns the code hook on for all my custom intents, and the "Use a Lambda function for initialization and validation" is checked for these in the Lex console.
How can I also turn the same hook on for the FallbackIntent? The console checkbox is not being checked, so this also indicates that the bot is not going to invoke the lambda for the FallbackIntent.

dmb0058 · Answer

This doesn't make sense to me because it's not possible to use CreateIntent for the FallbackIntent - it's a builtin.
Maybe I have to try UpdateIntent using the FallbackIntent intent ID?

re:Post Agent · Answer

To hook the FallbackIntent to your Lambda function in Amazon Lex V2, you need to configure it specifically for the fallback intent. The process is slightly different from hooking custom intents.

For the FallbackIntent, you need to set the `fulfillmentCodeHook` parameter when creating or updating the intent. This is typically done through the CreateIntent or UpdateIntent API operations, or through the AWS Management Console.

In the console:

1. Navigate to your bot and select the FallbackIntent.
2. In the "Fulfillment" section, choose "AWS Lambda function" as the fulfillment method.
3. Select the Lambda function you want to use.
4. Save and build your bot.

If you're using the AWS SDK or CLI, you would need to include the `fulfillmentCodeHook` parameter in your CreateIntent or UpdateIntent call for the FallbackIntent.

It's important to note that the FallbackIntent behaves differently from custom intents. It doesn't have utterances, slots, or a confirmation prompt. When invoked, it will either return intent information to the client application or call the specified Lambda function, depending on how you've configured the `fulfillmentCodeHook`.

Your Lambda function can use this opportunity to handle unrecognized inputs, perhaps by prompting the user for clarification, redirecting to a different intent, or providing a helpful message. You can also use session variables in your Lambda function to keep track of how many times the FallbackIntent has been invoked in a session, allowing you to implement more complex fallback strategies.

Remember to rebuild and redeploy your bot after making these changes for them to take effect.  
**Sources**  
[AMAZON.FallbackIntent - Amazon Lex](https://docs.aws.amazon.com/lexv2/latest/dg/built-in-intent-fallback.html)  
[AMAZON.FallbackIntent - Amazon Lex V1](https://docs.aws.amazon.com/lex/latest/dg/built-in-intent-fallback.html)

How to hook the FallbackIntent

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