feat: adding QueryExpander, MultiQueryEmbeddingRetriever and MultiQueryTextRetriever

[davidsbatista]

Related Issues

• fixes Migrate QueryExpander, MultiQueryTextRetriever and MultiQueryEmbeddingRetriever from haystack-experimental to haystack #10086

Proposed Changes:

• Adding 3 new components from experimental:
  • QueryExpander
  • MultiQueryEmbeddingRetriever
  • MultiQueryTextRetriever

How did you test it?

• unit tests, integration tests + CI

Checklist

• I have read the contributors guidelines and the code of conduct.
• I have updated the related issue with new insights and changes.
• I have added unit tests and updated the docstrings.
• I've used one of the conventional commit types for my PR title: fix:, feat:, build:, chore:, ci:, docs:, style:, refactor:, perf:, test: and added ! in case the PR includes breaking changes.
• I have documented my code.
• I have added a release note file, following the contributors guidelines.
• I have run pre-commit hooks and fixed any issue.

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1 Skipped Deployment

Project	Deployment	Preview	Comments	Updated (UTC)
haystack-docs	Ignored	Preview		Nov 24, 2025 3:52pm

[coveralls]

Pull Request Test Coverage Report for Build 19640435406

Warning: This coverage report may be inaccurate.

This pull request's base commit is no longer the HEAD commit of its target branch. This means it includes changes from outside the original pull request, including, potentially, unrelated coverage changes.

• For more information on this, see Tracking coverage changes with pull request builds.
• To avoid this issue with future PRs, see these Recommended CI Configurations.
• For a quick fix, rebase this PR at GitHub. Your next report should be accurate.

Details

• 0 of 0 changed or added relevant lines in 0 files are covered.
• 3 unchanged lines in 1 file lost coverage.
• Overall coverage increased (+0.1%) to 91.539%

---

Files with Coverage Reduction	New Missed Lines	%
core/pipeline/async_pipeline.py	3	65.88%

Totals
Change from base Build 19637726908:	0.1%
Covered Lines:	13913
Relevant Lines:	15199

---

💛 - Coveralls

[anakin87]

I left some minor comments.

Let's also try to increase the coverage of these new components with unit tests. The coveralls report can help.

[anakin87]

Looks good.

Please also create a new issue to track the creation of documentation pages for these new components.