diff --git a/.github/workflows/deploy-tap.yml b/.github/workflows/deploy-tap.yml
index 769cce98a..5e4a56d87 100644
--- a/.github/workflows/deploy-tap.yml
+++ b/.github/workflows/deploy-tap.yml
@@ -7,15 +7,14 @@ on:
     paths:
       - 'packaging/homebrew/mfc.rb'
       - 'packaging/homebrew/README.md'
-  # Deploy to tap on push to master
+  # Deploy to tap on push to master (only when formula files changed)
   push:
-    branches: [ master, homebrew-new ]
+    branches: [ master ]
     paths:
       - 'packaging/homebrew/mfc.rb'
       - 'packaging/homebrew/README.md'
-    tags:
-      - 'v*.*.*'
-  # Allow manual trigger for testing
+  # Deploy to tap when a tag is created (no paths filter on tag creation)
+  create:
   workflow_dispatch:
 
 permissions:
@@ -25,6 +24,7 @@ jobs:
   deploy-tap:
     name: Audit and deploy formula
     runs-on: macos-14
+    if: github.event_name != 'create' || github.event.ref_type == 'tag'
     permissions:
       contents: write
       pull-requests: write
@@ -37,28 +37,38 @@ jobs:
       - name: Determine event metadata
         id: meta
         run: |
-          if [[ "${GITHUB_REF_TYPE}" == "tag" ]]; then
-            VERSION="${GITHUB_REF_NAME#v}"
+          set -euo pipefail
+          EVENT_NAME="${{ github.event_name }}"
+          REF_NAME="${{ github.ref_name }}"
+          
+          if [[ "${EVENT_NAME}" == "create" ]]; then
+            # Tag creation event
+            VERSION="${REF_NAME#v}"
+            URL="https://github.com/${{ github.repository }}/archive/refs/tags/v${VERSION}.tar.gz"
+          elif [[ "${GITHUB_REF_TYPE:-}" == "tag" ]]; then
+            # Tag push event
+            VERSION="${REF_NAME#v}"
             URL="https://github.com/${{ github.repository }}/archive/refs/tags/v${VERSION}.tar.gz"
           else
             # Extract URL from current formula to re-audit and sync
-            URL="$(grep -Eo 'https://github.com/.*/archive/refs/tags/v[0-9]+\.[0-9]+\.[0-9]+\.tar\.gz' packaging/homebrew/mfc.rb | head -n1)"
+            URL="$(grep -Eo 'https://github.com/[^"]+/archive/refs/tags/v[0-9]+\.[0-9]+\.[0-9]+\.tar\.gz' packaging/homebrew/mfc.rb | tail -n 1)"
             VERSION="$(echo "${URL}" | sed -E 's/.*v([0-9]+\.[0-9]+\.[0-9]+)\.tar\.gz/\1/')"
           fi
+          
           SHASUM="$(curl -sL "${URL}" | shasum -a 256 | awk '{print $1}')"
           echo "version=${VERSION}" >> $GITHUB_OUTPUT
           echo "url=${URL}" >> $GITHUB_OUTPUT
           echo "sha256=${SHASUM}" >> $GITHUB_OUTPUT
-          echo "Event: ${{ github.event_name }}" >> $GITHUB_STEP_SUMMARY
+          echo "Event: ${EVENT_NAME}" >> $GITHUB_STEP_SUMMARY
           echo "Version: ${VERSION}" >> $GITHUB_STEP_SUMMARY
-          if [[ "${{ github.event_name }}" == "pull_request" ]]; then
+          if [[ "${EVENT_NAME}" == "pull_request" ]]; then
             echo "Mode: Audit only (PR)" >> $GITHUB_STEP_SUMMARY
           else
             echo "Mode: Audit and deploy" >> $GITHUB_STEP_SUMMARY
           fi
 
       - name: Update formula (for tag events)
-        if: github.ref_type == 'tag'
+        if: github.event_name == 'create' || github.ref_type == 'tag'
         run: |
           /usr/bin/sed -i '' "s@^  url \".*\"@  url \"${{ steps.meta.outputs.url }}\"@" packaging/homebrew/mfc.rb
           /usr/bin/sed -i '' "s@^  sha256 \".*\"@  sha256 \"${{ steps.meta.outputs.sha256 }}\"@" packaging/homebrew/mfc.rb
diff --git a/packaging/homebrew/mfc.rb b/packaging/homebrew/mfc.rb
index 2e7d0a02f..e4e50da94 100644
--- a/packaging/homebrew/mfc.rb
+++ b/packaging/homebrew/mfc.rb
@@ -6,8 +6,8 @@
 class Mfc < Formula
   desc "Exascale multiphase/multiphysics compressible flow solver"
   homepage "https://mflowcode.github.io/"
-  url "https://github.com/MFlowCode/MFC/archive/refs/tags/v5.1.0.tar.gz"
-  sha256 "4684bee6a529287f243f8929fb7edb0dfebbb04df7c1806459761c9a6c9261cf"
+  url "https://github.com/MFlowCode/MFC/archive/refs/tags/v5.1.5.tar.gz"
+  sha256 "229ba4532d9b31e54e7db67cc6c6a4c069034bb143be7c57cba31c5a56fe6a0b"
   license "MIT"
   head "https://github.com/MFlowCode/MFC.git", branch: "master"
 
@@ -29,7 +29,11 @@ def install
     # Create Python virtual environment inside libexec (inside Cellar for proper bottling)
     venv = libexec/"venv"
     system Formula["python@3.12"].opt_bin/"python3.12", "-m", "venv", venv
-    system venv/"bin/pip", "install", "--upgrade", "pip", "setuptools", "wheel", "setuptools-scm"
+    system venv/"bin/pip", "install", "--upgrade",
+           "pip", "setuptools", "wheel",
+           "setuptools-scm",
+           "hatchling", "hatch-vcs",
+           "editables"
 
     # Install Cantera from PyPI using pre-built wheel (complex package, doesn't need custom flags)
     # Cantera has CMake compatibility issues when building from source with newer CMake versions
@@ -42,8 +46,9 @@ def install
     # Keep toolchain in buildpath for now - mfc.sh needs it there
     #
     # MFC's toolchain uses VCS-derived versioning (via Hatch/hatch-vcs) and Homebrew builds from
-    # GitHub release tarballs without a .git directory. Scope pretend-version env vars tightly
-    # to avoid polluting subsequent pip installs.
+    # GitHub release tarballs without a .git directory. Use --no-build-isolation so the build
+    # backend can see our environment variables, and set SETUPTOOLS_SCM_PRETEND_VERSION which
+    # hatch-vcs respects when VCS metadata is unavailable.
     pretend_env = {
       "SETUPTOOLS_SCM_PRETEND_VERSION_FOR_MFC" => version.to_s,
       "SETUPTOOLS_SCM_PRETEND_VERSION_FOR_mfc" => version.to_s,
@@ -56,7 +61,7 @@ def install
     end
 
     begin
-      system venv/"bin/pip", "install", "-e", buildpath/"toolchain"
+      system venv/"bin/pip", "install", "--no-build-isolation", "-e", buildpath/"toolchain"
     ensure
       pretend_env.each_key do |k|
         if saved_env[k].nil?
@@ -75,6 +80,11 @@ def install
     # Set VIRTUAL_ENV so mfc.sh uses existing venv instead of creating new one
     ENV["VIRTUAL_ENV"] = venv
 
+    # Also set pretend-version env vars for mfc.sh in case it tries to reinstall toolchain
+    ENV["SETUPTOOLS_SCM_PRETEND_VERSION_FOR_MFC"] = version.to_s
+    ENV["SETUPTOOLS_SCM_PRETEND_VERSION_FOR_mfc"] = version.to_s
+    ENV["SETUPTOOLS_SCM_PRETEND_VERSION"] = version.to_s
+
     # Build MFC using pre-configured venv
     # Must run from buildpath (MFC root directory) where toolchain/ exists
     Dir.chdir(buildpath) do