diff --git a/hooks/scripts/session-orient.sh b/hooks/scripts/session-orient.sh
index 05cd652..46caa21 100755
--- a/hooks/scripts/session-orient.sh
+++ b/hooks/scripts/session-orient.sh
@@ -139,13 +139,25 @@ fi
 
 # Methodology staleness check (Rule Zero)
 if [ -d ops/methodology ] && [ -f ops/config.yaml ]; then
-  CONFIG_MTIME=$(stat -f %m ops/config.yaml 2>/dev/null || stat -c %Y ops/config.yaml 2>/dev/null || echo 0)
+  # Detect platform for stat syntax: Linux uses -c %Y, macOS uses -f %m.
+  # Must try Linux first — on Linux, stat -f means "filesystem stats" and
+  # succeeds with wrong output instead of failing, breaking the || fallback.
+  if stat -c %Y ops/config.yaml &>/dev/null 2>&1; then
+    _STAT_FMT() { stat -c %Y "$1" 2>/dev/null || echo 0; }
+  elif stat -f %m ops/config.yaml &>/dev/null 2>&1; then
+    _STAT_FMT() { stat -f %m "$1" 2>/dev/null || echo 0; }
+  else
+    _STAT_FMT() { echo 0; }
+  fi
+
+  CONFIG_MTIME=$(_STAT_FMT ops/config.yaml)
   NEWEST_METH=$(ls -t ops/methodology/*.md 2>/dev/null | head -1)
   if [ -n "$NEWEST_METH" ]; then
-    METH_MTIME=$(stat -f %m "$NEWEST_METH" 2>/dev/null || stat -c %Y "$NEWEST_METH" 2>/dev/null || echo 0)
+    METH_MTIME=$(_STAT_FMT "$NEWEST_METH")
     DAYS_STALE=$(( (CONFIG_MTIME - METH_MTIME) / 86400 ))
     if [ "$DAYS_STALE" -ge 30 ]; then
       echo "CONDITION: Methodology notes are ${DAYS_STALE}+ days behind config changes. Consider /rethink drift."
     fi
   fi
+  unset -f _STAT_FMT
 fi
diff --git a/skill-sources/rethink/SKILL.md b/skill-sources/rethink/SKILL.md
index 76c4257..93fee41 100644
--- a/skill-sources/rethink/SKILL.md
+++ b/skill-sources/rethink/SKILL.md
@@ -86,9 +86,10 @@ Read:
 
 ```bash
 # Compare config.yaml modification time vs newest methodology note
-CONFIG_MTIME=$(stat -f %m ops/config.yaml 2>/dev/null || stat -c %Y ops/config.yaml 2>/dev/null || echo 0)
+# Linux stat -f means filesystem stats (not file), so try -c first
+CONFIG_MTIME=$(stat -c %Y ops/config.yaml 2>/dev/null || stat -f %m ops/config.yaml 2>/dev/null || echo 0)
 NEWEST_METH=$(ls -t ops/methodology/*.md 2>/dev/null | head -1)
-METH_MTIME=$(stat -f %m "$NEWEST_METH" 2>/dev/null || stat -c %Y "$NEWEST_METH" 2>/dev/null || echo 0)
+METH_MTIME=$(stat -c %Y "$NEWEST_METH" 2>/dev/null || stat -f %m "$NEWEST_METH" 2>/dev/null || echo 0)
 ```
 
 If `CONFIG_MTIME > METH_MTIME`: config has changed since methodology was last updated. Flag as staleness drift.
diff --git a/skills/health/SKILL.md b/skills/health/SKILL.md
index 7c72862..7c37e4e 100644
--- a/skills/health/SKILL.md
+++ b/skills/health/SKILL.md
@@ -407,7 +407,8 @@ for f in {vocabulary.notes}/*.md; do
   basename=$(basename "$f" .md)
 
   # Last modified (days ago)
-  mod_days=$(( ($(date +%s) - $(stat -f %m "$f" 2>/dev/null || stat -c %Y "$f" 2>/dev/null)) / 86400 ))
+  # Linux stat -f means filesystem stats (not file), so try -c first
+  mod_days=$(( ($(date +%s) - $(stat -c %Y "$f" 2>/dev/null || stat -f %m "$f" 2>/dev/null || echo 0)) / 86400 ))
 
   # Incoming link count
   incoming=$(rg -l "\[\[$basename\]\]" --glob '*.md' | grep -v "$f" | wc -l | tr -d ' ')