Contrib.social

Enable optional RAG prefix for asymmetric models

Open on Drupal.org →
Created on 17 May 2025, about 1 month ago

Problem/Motivation

The AI Search Block currently sends the raw user query to the retriever, which works for symmetric embedding models. However, many instruct‑tuned or asymmetric models (e.g., multilingual-e5‑large-instruct, GTE‑QWEN) require a prompt prefix (like “query: ”) to generate embeddings correctly.

Proposed resolution

  • Add an optional checkbox “Enable retrieval prefix” to the block’s settings form.
  • When checked, reveal a textarea for users to enter their custom prefix template via Drupal’s Form API state system.
  • Modify the retrieval service to prepend the configured prefix before the query string.
  • Include usage examples (e.g., prefix = “Instruct: blablabla\nQuery: {query}”) in the field description.

User interface changes

  • New checkbox: enable_prefix under “Retrieval settings”.
  • Conditional textarea: prefix_template appears when enable_prefix is checked.
  • Help text explaining which models need a prefix and example syntax.

Remaining tasks

  1. Implement form elements and #states logic in AI_search_block\Form\SettingsForm.
  2. Update retrieval plugin to inject prefix when enabled.
  3. Create unit tests to verify prefix behavior.
  4. Adjust documentation to cover prefix configuration and best practices.
✨ Feature request
Status

Active

Version

1.0

Component

Code

Created by

🇪🇸Spain Nikro Benalmadena, Malaga

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