[HaraldNordgren]

brew cleanup prints Warning: Skipping <formula>: most recent version <version> not installed for every outdated formula and cleans up nothing for them. Most of these formulae have a single keg, so there is nothing to clean anyway. The comment above the warning still says "If the rack only has one version installed, don't complain" and the original check was rack.children.length > 1, but cc8859f ("cleanup: use installed_prefixes/installed_kegs") turned it into installed_prefixes.any? in 2015.

When several kegs are installed but not the latest, brew cleanup keeps all of them and warns that it can't tell which one to keep. It can. With the latest installed, cleanup already picks the keg to keep by version alone, linked or not, and only spares older kegs that are linked, pinned or still needed by another keg. On my install this left kegs like pcre 8.40, 8.41 and 8.42 next to 8.44.

When the latest version isn't installed, Formula#eligible_kegs_for_cleanup now keeps the highest installed stable keg, by version_scheme and then version, and removes the older ones with the same linked, pinned and keepme protections. HEAD kegs are left alone, as the latest-installed path does when a stable spec is active. So are incomplete kegs without an install receipt, so a keg left behind by a killed install is never kept in place of a complete one. The warning now reads Skipping <keg>: most recent version <version> not installed and only prints when older kegs are being removed. A formula with a single keg stays quiet, pinned formulae stay quiet as before and the message stops once the older kegs are gone.

The version_scheme ordering matters for downgrades like openssl@3 3.6.5 to 3.5.9 (LTS), which bumped version_scheme to 1. With 3.6.2, 3.6.3 and 3.6.5 installed, cleanup keeps 3.6.5. Applying the latest-installed rule instead would treat all three as older than 3.5.9 and remove every keg, which one of the new specs checks.

To reproduce, with outdated formulae that have one or several old kegs installed:

$ ls "$(brew --cellar)/pcre"
8.40	8.41	8.42	8.44
$ ls "$(brew --cellar)/brotli"
1.0.9
$ brew cleanup -n pcre openssl@3 brotli
Warning: Skipping pcre: most recent version 8.45 not installed
Warning: Skipping openssl@3: most recent version 3.5.9 not installed
Warning: Skipping brotli: most recent version 1.2.1 not installed

---

• Have you followed our Contributing guidelines?
• Have you checked for other open Pull Requests for the same change?
• Have you explained what your changes do? Performance claims (e.g. "this is faster") must include brew benchmark results.
• Have you explained why you'd like these changes included, not just what they do?
• For bug fixes, have you given step-by-step brew commands to reproduce the bug?
• Have you written new tests (excluding integration tests)? Here's an example.
• Have you successfully run brew lgtm (style, typechecking and tests) locally?

---

• I did not use AI/LLM to create this PR, or I disclosed the tool/model below and reviewed its output; I did not attribute commits to AI and will answer maintainer questions and review comments myself without AI/LLM.

Claude Code (Claude Opus 5.5) traced the warning back to cc8859f, wrote the change and its specs and verified them. Each new spec fails against main or a deliberately broken copy of the change and passes with it. It ran brew lgtm, which passes. The reproduction output above is from my install on main.

---

[coderabbitai]

Summary

Summary by CodeRabbit

• Bug Fixes
  • Cleanup can select eligible installations when multiple prefixes are installed, even if the latest version is absent.
  • When the latest version is absent, cleanup excludes HEAD installations and keeps the newest eligible installation. Older installations may trigger a warning unless the formula is quiet or pinned.
  • Existing cleanup behavior is preserved when the latest version is installed, including selection between HEAD and stable installations when a latest HEAD version is available.

eligible_kegs_for_cleanup now selects older installed kegs when the latest formula version is absent. It retains existing exclusions and removes the former warning. Tests cover linked kegs, version schemes, downgrade histories, HEAD kegs, and incomplete kegs.

Changes: Formula keg cleanup

Layer / File(s)	Summary
Cleanup eligibility and regression coverage Library/Homebrew/formula.rb, Library/Homebrew/test/formula_spec.rb	Cleanup eligibility now requires multiple installed prefixes. If the latest version is absent, the method selects all but the newest eligible non-HEAD keg, ordered by scheme and version. Existing linked-keg exclusions remain. The former warning is removed. Tests cover version ordering, downgrade histories, HEAD kegs, and incomplete kegs.

Merge Risk: Low · up to fbd98

Cleanup can warn that it is keeping a keg even when it removes nothing. This is a bounded messaging issue that can be corrected with a localized change.

Pre-merge checks: 4

Check name	Status	Explanation
Title check		The title clearly and concisely describes the main change: removing old kegs for outdated formulae during cleanup.
Description check		The description directly explains the cleanup behaviour, warning changes, retention rules, protections, tests, and reproduction steps.
Linked Issues check		Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check		Check skipped because no linked issues were found for this pull request.

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[MikeMcQuaid]

Code looks good, one question.

[coderabbitai]

Caution

Some comments are outside the diff and can’t be posted inline due to GitHub limitations.

⚠️ Outside diff range comments (1)

Minor · Emit the warning only when a cleanup candidate remains. · formula.rb:3838

Library/Homebrew/formula.rb:3838
Minor · Functional Correctness · Quick win

Emit the warning only when a cleanup candidate remains.

When every older keg is linked or protected by keepme, line 3838 emits the missing-latest warning before protection filtering. eligible_kegs_for_cleanup then returns no keg, so cleanup_formula performs no removal. Move the warning below the protection loop and check the post-protection list. Keep the newest_keg guard so other cleanup branches do not use this warning.

Suggested fix

         newest_keg = kegs.pop
-        if !kegs.empty? && !quiet && !pinned?
-          opoo "Skipping #{newest_keg}: most recent version #{pkg_version} not installed"
-        end
         kegs
@@
       unless eligible_kegs.empty?
         eligible_kegs.each do |keg|
           if keg.linked?
             opoo "Skipping (old) #{keg} due to it being linked" unless quiet
           elsif pinned? && keg == Keg.new(resolved_path(@pin.path))
             opoo "Skipping (old) #{keg} due to it being pinned" unless quiet
           elsif (keepme_refs = keg.keepme_refs.presence)
             opoo "Skipping #{keg} as it is needed by #{keepme_refs.join(", ")}" unless quiet
           else
             eligible_for_cleanup << keg
           end
         end
       end
+      if newest_keg && !eligible_for_cleanup.empty? && !quiet && !pinned?
+        opoo "Skipping #{newest_keg}: most recent version #{pkg_version} not installed"
+      end

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Files selected for processing: 2

• Library/Homebrew/formula.rb
• Library/Homebrew/test/formula_spec.rb

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• Library/Homebrew/formula.rb
• Library/Homebrew/test/formula_spec.rb

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[MikeMcQuaid]

Thanks!