diff --git a/.github/workflows/tests.yml b/.github/workflows/tests.yml
index 556a39c..c228d3b 100755
--- a/.github/workflows/tests.yml
+++ b/.github/workflows/tests.yml
@@ -55,6 +55,30 @@ jobs:
       if: startsWith(runner.os, 'macOS')
       run: |
         echo "TMPDIR=$RUNNER_TEMP" >> $GITHUB_ENV
+    - name: Diagnostic on macOS
+      if: startsWith(runner.os, 'macOS')
+      run: |
+        set -euxo pipefail
+
+        echo "whoami=$(whoami)"
+        id
+        umask
+        echo "RUNNER_TEMP=$RUNNER_TEMP"
+        echo "TMPDIR=${TMPDIR:-"(unset)"}"
+
+        # Show perms + ACLs on the temp area (macOS: -e shows ACLs)
+        ls -ldOe@ /Users/runner/work/_temp || true
+        ls -ldOe@ "$RUNNER_TEMP" || true
+
+        # If the failing directory exists, dump its perms too
+        ls -ldOe@ /Users/runner/work/_temp/rio* || true
+
+        # Repro: create + write in a fresh subdir
+        d="$(mktemp -d "$RUNNER_TEMP/rio-probe.XXXXXX")"
+        ls -ldOe@ "$d"
+        touch "$d/can_write"
+        ls -lOe@ "$d/can_write"
+
     - name: Build and run tests
       shell: bash
       run: |
diff --git a/rio/test/RIO/FileSpec.hs b/rio/test/RIO/FileSpec.hs
index ce10305..f7978dc 100644
--- a/rio/test/RIO/FileSpec.hs
+++ b/rio/test/RIO/FileSpec.hs
@@ -58,9 +58,11 @@ sameAsWithFiletest = do
   -- appear to be in that environment.
   mGitHubActions <- lookupEnv "GITHUB_ACTIONS"
   case mGitHubActions of
+  {-
     Just "true" -> pendingWith $
       "On GitHub macOS runners, the file system appears to reject " <>
       "durability-related open flags."
+  -}
     _ -> test
 #endif
  where