diff --git a/__tests__/darwin-version.test.ts b/__tests__/darwin-version.test.ts
new file mode 100644
index 00000000..38aa2710
--- /dev/null
+++ b/__tests__/darwin-version.test.ts
@@ -0,0 +1,62 @@
+import {execFileSync} from 'node:child_process';
+import * as fs from 'node:fs';
+
+describe('macOS installed PHP version comparison', () => {
+  const functions = fs
+    .readFileSync('src/scripts/darwin.sh', 'utf8')
+    .split('# Variables')[0];
+
+  it.each([
+    ['8.7.0-dev', '8.7.0', 'Found'],
+    ['8.6.0-dev', '8.6.0', 'Found'],
+    ['8.7.0-dev', '8.7.0-dev', 'Found'],
+    ['8.5.9', '8.5.9', 'Found'],
+    ['8.5.9', '8.5.11', 'Upgraded'],
+    ['8.6.0RC1', '8.6.0', 'Upgraded'],
+    ['8.7.0-dev', '8.7.1', 'Upgraded']
+  ])('handles runtime %s with formula %s', (runtime, formula, expected) => {
+    // Exercise setup_php's real selection path while isolating system writes
+    // and the configuration stage from this version-comparison regression.
+    const output = execFileSync(
+      'bash',
+      [
+        '-c',
+        `${functions}
+version="$REQUESTED"
+debug=release ts=nts old_versions='^5\\.[3-5]$'
+src=/unused RUNNER_TOOL_CACHE=/unused tool_path_dir=/unused tick=ok cross=error
+step_log() { :; }
+check_pre_installed() { :; }
+get_brewed_php() { echo "$RUNTIME"; }
+php_semver() { echo "$RUNTIME"; }
+brew() { test "$1" = info || exit 2; echo "$FORMULA"; }
+jq() { cat; }
+add_php() { printf '%s\n' "$1" >&3; }
+php-config() { :; }
+sed() { echo /unused; }
+sudo() { :; }
+php_ini_path() { echo /unused; }
+get_scan_dir() { echo /unused; }
+php_extra_version() { :; }
+configure_php() { :; }
+link_opcache() { :; }
+set_output() { :; }
+add_log() { printf '%s\n' "$*"; }
+setup_php 3>&1
+`
+      ],
+      {
+        encoding: 'utf8',
+        env: {
+          ...process.env,
+          REQUESTED: runtime.split('.').slice(0, 2).join('.'),
+          RUNTIME: runtime,
+          FORMULA: formula
+        }
+      }
+    );
+    expect(output).toContain(`${expected} PHP ${runtime}`);
+    if (expected === 'Upgraded') expect(output).toContain('upgrade\n');
+    else expect(output).not.toContain('upgrade\n');
+  });
+});
diff --git a/src/scripts/darwin.sh b/src/scripts/darwin.sh
index f10fda4a..f8145a12 100644
--- a/src/scripts/darwin.sh
+++ b/src/scripts/darwin.sh
@@ -286,7 +286,8 @@ setup_php() {
     status="Installed"
   elif [[ "${existing_version:0:3}" = "$version" && "${update:?}" = "true" ]]; then
     brew_php_version="$(brew info --json "php@$version" 2>/dev/null | jq -r '.[].versions.stable')"
-    if [ "$brew_php_version" != "$existing_version" ]; then
+    # Homebrew records development snapshots without PHP's runtime -dev suffix.
+    if [ "$brew_php_version" != "$existing_version" ] && [ "$brew_php_version" != "${existing_version%-dev}" ]; then
       add_php "upgrade" "$existing_version" >/dev/null 2>&1 || {
         add_log "${cross:?}" "PHP" "Could not upgrade PHP $version"
         exit 1