Amazon Connect Lex Integration – Need Control Over Lex Timeout for Spelling Inputs

Question

Hi,

We are building a conversational bot using Amazon Lex V2 integrated with Amazon Connect, and we’ve encountered an issue when capturing spelled inputs, such as flight numbers (e.g., “A-F-1-2-3”). The Lex bot does not wait long enough for users to finish spelling the flight number, which results in incomplete or unfulfilled slot values.

We’ve reviewed this section of the documentation related to configuring speech timeouts in Lex:
🔗 https://docs.aws.amazon.com/lexv2/latest/dg/session-attribs-speech.html

The document describes session attributes like:
	•	speech_input_timeout_seconds
	•	no_speech_timeout_milliseconds
	•	max_speech_timeout_milliseconds

However, these configurations seem to apply only to the Lex Streaming API, not to the Amazon Connect integration, where Lex is used in a Contact Flow block (Get Customer Input).

Our Question:

Is there a way to configure these speech timeouts (especially inter-speech silence or no-speech timeout) in the context of Amazon Connect’s Lex integration, so we can give callers more time between spelling letters?

Any guidance on how to extend or customize the Lex interaction timing behavior in this setup would be greatly appreciated.

Thank you!

re:Post Agent · Accepted Answer

You can configure timeouts for voice interactions with your Lex V2 bot in Amazon Connect by using session attributes in the "Get customer input" block that calls your Lex bot. For your specific use case of capturing spelled inputs like flight numbers, you should focus on these key timeout settings:

1. **End Silence Threshold**: Use the session attribute `x-amz-lex:audio:end-timeout-ms:[intentName]:[slotToElicit]` to increase how long the bot waits after the customer stops speaking before assuming the utterance has concluded. This is particularly useful for spelled inputs where users pause between letters. The default is 600 milliseconds (0.6 seconds), but you can increase this to allow for pauses between spelled characters.

2. **Start Silence Threshold**: Use `x-amz-lex:audio:start-timeout-ms:[intentName]:[slotToElicit]` to control how long to wait before assuming the customer isn't going to speak. The default is 3000 milliseconds (3 seconds).

3. **Max Speech Duration**: Use `x-amz-lex:audio:max-length-ms:[intentName]:[slotToElicit]` to set how long the customer can speak before input is truncated. The default is 12000 milliseconds (12 seconds), with a maximum allowed value of 15000 milliseconds.

You can set these attributes specifically for the intent and slot that captures flight numbers, or use wildcards to apply settings more broadly. For example, to set an end silence threshold of 2000 milliseconds for all slots in a specific intent, you could use: `x-amz-lex:audio:end-timeout-ms:FlightBookingIntent:*` with a value of `2000`.

These session attributes can be configured in the "Get customer input" block in your Amazon Connect contact flow, allowing you to customize the timeout behavior specifically for your flight number spelling use case.  
**Sources**  
[Flow block in Amazon Connect: Get customer input - Amazon Connect](https://docs.aws.amazon.com/connect/latest/adminguide/get-customer-input.html)  
[Configuring timeouts for capturing user input with a Lex V2 bot - Amazon Lex](https://docs.aws.amazon.com/lexv2/latest/dg/session-attribs-speech.html)  
[StartBotConversation - Amazon Chime SDK](https://docs.aws.amazon.com/chime-sdk/latest/dg/start-bot-conversation.html)

Amazon Connect Lex Integration – Need Control Over Lex Timeout for Spelling Inputs

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