@yuhaowin Hello there! I'm here to help you with any bugs, questions, or contributions. Let me know how I can assist you while you wait for a human maintainer.

The issue you're experiencing, where you cannot change the rerank model in the external knowledge base retrieval, might be related to a few known limitations or configuration requirements in Dify.

1. Model Provider Configuration: Ensure that the API key for the rerank model is correctly set up on the "Model Provider" page. Without this, the rerank model options might not be available for selection ^[1].

2. Inconsistency in Embedding Models: If there are inconsistencies in the embedding models used across multiple referenced knowledge bases, it can lead to issues with rerank model selection. Make sure that the retrieval settings are consistent across all knowledge bases ^[1].

3. Index Mode: If your knowledge base is using the "Economical" index mode, you might not see the option to change the rerank model. Switching to the "High Quality" index mode could resolve this issue ^[1].

4. UI Components: The UI components involved in changing the rerank model include the ModelSelector and Switch. Ensure that these components are functioning correctly and that the rerank model list is populated ^[2][3].

If these steps do not resolve the issue, it might be a bug specific to the version you are using (0.13.2). In such cases, checking for updates or patches that address this issue might be helpful.

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