Document full project routing support for cross-project search (CPS)

[charlotte-hoblik]

Part of elastic/docs-content-internal#1279.
Cross-project search now supports full project routing. The project_routing parameter accepts any predefined tag (_alias, _csp, _region, and others) or custom Cloud tag, with boolean logic, groupings, and wildcards, using Lucene query syntax.
Changes:

• Remove the "project routing only supports the _alias tag" note on the project routing page.
• Expand the project routing examples on the routing page and the CPS overview page to cover multiple tags, boolean logic, groupings, and wildcards.
• Add named project routing expression examples (create with the _project_routing API, reference with @).
• Add "what fails" examples for the known error cases.
• Fix the origin-only example to use the reserved _alias:_origin value.

Behind a serverless feature flag, so kept as draft until the flag is confirmed enabled.
Kibana docs follow in July/August.
Companion ES|QL change: elastic/elasticsearch#152673

[github-actions]

Elastic Docs AI PR menu

Check the box to run an AI review for this pull request.

• Review docs changes (docs-review). Status: queued.

Powered by GitHub Agentic Workflows and docs-actions. For more information, reach out to the docs team.

[github-actions]

🔍 Preview links for changed docs

• explore-analyze/cross-project-search.md
• explore-analyze/cross-project-search/cross-project-search-project-routing.md

[github-actions]

✅ Elastic Docs Style Checker (Vale)

No issues found on modified lines!

---

The Vale linter checks documentation changes against the Elastic Docs style guide. To use Vale locally or report issues, refer to Elastic style guide for Vale.

[github-actions]

Docs review summary

Focus areas

• Style and clarity: One voice inconsistency in the new intro paragraph (inline comment). Pre-existing Vale findings (execute, all of, my) all fall in untouched sections and were skipped.
• Jargon: No unexplained jargon introduced. CPS is established in context; ES|QL, _search, and tag names are code/API terms used correctly.
• Frontmatter and applies_to: No issues. Frontmatter is unchanged in both files and looks correct for a serverless-preview feature.
• Content type fit: Both files are how-to/reference pages; the new sections fit the established structure.
• Parent issue satisfaction: Satisfied. All five stated goals are implemented: the _alias-only restriction note is removed, examples for multiple tags/boolean logic/groupings/wildcards are added to both pages, named expression examples are expanded with aws-us-only, "what fails" notes are added for both error cases, and the _alias:_origin fix is applied in both files.

Nits

• cross-project-search-project-routing.md uses API request as the tab label for the new example tab-set (line 39), while cross-project-search.md uses _search for equivalent tabs. Both are consistent within each file, but aligning the label across both pages would reduce friction for readers navigating between them.

Notes

• Vale findings were skipped because all five fall in pre-existing, untouched sections.

Generated by Docs review agent for issue #7168 · 55.1 AIC · ⌖ 6.69 AIC · ⊞ 10.7K

[quux00]

Looks good. A few suggestions provided.

[quux00]

This might be a good spot to add in the example:

project_routing:"_csp:* AND NOT _csp:azure"

rather than

project_routing:"NOT _csp:azure"

(as I mentioned on the other PR)

[charlotte-hoblik]

Added this with the other "what fails" cases in the note just below, so the gotchas stay together. Shout if you'd rather it be its own example! 🙏

[quux00]

LGTM. Nice work.