ci(homebrew): run tap PR workflow on macos

Author: smorin

.github/workflows/homebrew-tap-pr.yml

@@ -18,7 +18,9 @@ concurrency:
 jobs:
   update-tap:
     name: Update homebrew tap formula
-    runs-on: ubuntu-latest
+    # Formula verification calls `brew style/audit/install/test`, so run on macOS
+    # where Homebrew is available by default on GitHub-hosted runners.
+    runs-on: macos-latest
     permissions:
       contents: read
     env:

docs/adr/0014-run-homebrew-tap-pr-workflow-on-macos.md

@@ -0,0 +1,46 @@
+# 0014: Run Homebrew tap PR workflow on macOS
+Date: 2026-02-16
+Status: Accepted
+
+## Context
+
+The Homebrew tap workflow (`.github/workflows/homebrew-tap-pr.yml`) runs the
+`homebrew-verify-formula` step before opening or updating a tap PR.
+
+That verification path executes `brew style`, `brew audit`, `brew install`, and
+`brew test` via `scripts/homebrew/tap_release.py`.
+
+The job previously ran on `ubuntu-latest`, where `brew` is not available by
+default. This caused the workflow to fail before PR creation with:
+
+- `ERROR: \`brew\` is required for formula verification`
+
+As a result, release-to-tap automation could not complete even when tags and
+token permissions were valid.
+
+## Decision
+
+Run the `update-tap` job in `.github/workflows/homebrew-tap-pr.yml` on
+`macos-latest` instead of `ubuntu-latest`.
+
+## Consequences
+
+- Formula verification now executes in an environment where Homebrew is
+  available by default, allowing the workflow to proceed through verification
+  and PR creation.
+- The workflow keeps full verification coverage (`style`, `audit`, `install`,
+  `test`) instead of weakening checks.
+- Runtime/cost may increase relative to Ubuntu-hosted execution.
+
+## Alternatives considered
+
+1. Install Linuxbrew in the Ubuntu job.
+   - Rejected: adds setup complexity and more moving parts in a release
+     automation path.
+2. Skip formula verification when `brew` is missing.
+   - Rejected: reduces safety by allowing unverified formula changes.
+
+## References/links
+
+- `/Users/stevemorin/c/envgen/.github/workflows/homebrew-tap-pr.yml`
+- `https://github.com/smorinlabs/envgen/actions/runs/22078918496`