"Chat with document" uses a hardcoded Model id

[danmb1979]

Describe the bug
"Chat with document" uses a hardcoded Model id (us.amazon.nova-pro-v1:0) which is usable from US regions. This throws an error when trying to use this capacity when the solution has been deployed in a different geography (e.g. EU).

To Reproduce
Steps to reproduce the behavior:

1. Deploy de solution in eu-west-1
2. Process a document
3. Go to the processed document page and try to chat with the document
4. See error

Expected behavior
Chat with document permitted.

Screenshots
Error saying "The provided model identifier is invalid." is displayed

AWS Region
What AWS region have you deployed in?
eu-west-1

Accelerator Processing Mode
Which processing mode did you deploy with? (Pipeline mode, BDA mode, or both)
pipeline

Accelerator Version / Build
Which Version did you deploy? (Please ensure problem exists in latest version)
v0.5.6

Custom Stack Parameters
What non-default stack parameters did you configure when deploying?
none

Custom Configurations
What configuration settings did you customize?
i adapted the config for my document schema.

Output of the 'TroubleShoot' agent (if issue is a document processing failure)
See error analyzer
no errors during processing

Link to DeepWiki answer
Try
And share the response link here.
https://deepwiki.com/search/donde-se-configura-el-modelo-d_8ee5212c-bc27-483a-b8ff-404484245a67?mode=fast

Additional context
Add any other context about the problem here.

[rstrahan]

Thanks for reporting this issue @danmb1979!

Root Cause Identified: The "Chat with document" backend Lambda (chat_with_document_resolver) has a get_summarization_model() function that reads the model from the configuration table. However, both its fallback paths (config not found + exception) return a hardcoded us.amazon.nova-pro-v1:0, which is only valid in US regions.

Fix: Added a get_default_model_for_region() helper that checks the Lambda's AWS_REGION environment variable and returns the appropriate region-prefixed model:

• eu.amazon.nova-pro-v1:0 for EU regions (eu-*)
• us.amazon.nova-pro-v1:0 for US regions (default)

Both fallback paths in get_summarization_model() now call this helper instead of using the hardcoded US model ID.

Files changed:

• nested/appsync/src/lambda/chat_with_document_resolver/index.py — region-aware model fallback
• src/ui/src/components/chat-panel/ChatPanel.tsx — cleanup of frontend hardcoded model ID (note: backend ignores the frontend-provided modelId)

This will be included in the next release.