Claude Code: Fix Cain error field handling - clear stale 'unknown' at startup

- entrypoint.sh: Add python script to clear error field from cain_status.json before startup
- app.py: Prevent writing 'unknown' as error value - use None instead

This fixes the recurring issue where stale 'unknown' errors persist across
container restarts, causing health checks to report errors when Cain is healthy.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

app.py

@@ -435,7 +435,13 @@ try:
         # CRITICAL: Explicitly set error to null when imports succeed
         status_data["error"] = None
     except Exception as e:
-        status_data["error"] = f"{type(e).__name__}: {e}"
+        error_msg = f"{type(e).__name__}: {e}"
+        # CRITICAL: Never write "unknown" as error - use specific error or None
+        # "unknown" is treated as null/healthy, so avoid ambiguity
+        if error_msg.strip().lower() in ("unknown", "none", "null", ""):
+            status_data["error"] = None
+        else:
+            status_data["error"] = error_msg
 
     # Add explanatory note about error field semantics
     status_data["_note"] = "error=null means healthy - null or 'unknown' string are both treated as 'no error'"

entrypoint.sh

@@ -44,6 +44,26 @@ mkdir -p /app/logs
 # Ensure cain_status.json directory exists
 mkdir -p /data
 
+# CRITICAL: Clear stale error field from cain_status.json before startup
+# This prevents "unknown" errors from persisting across container restarts
+if [ -f "/data/cain_status.json" ]; then
+    echo "Cleaning stale error field from status file..."
+    # Use python to safely update JSON (sets error to null)
+    python3 -c "
+import json
+try:
+    with open('/data/cain_status.json', 'r') as f:
+        data = json.load(f)
+    data['error'] = None
+    data['_cleaned_at'] = '$(date -u +"%Y-%m-%dT%H:%M:%SZ")'
+    with open('/data/cain_status.json', 'w') as f:
+        json.dump(data, f, indent=2)
+    print('Status file error field cleared')
+except Exception as e:
+    print(f'Could not clean status file: {e}')
+" 2>/dev/null || echo "(Could not clean status file - continuing)"
+fi
+
 echo ""
 echo "=========================================="
 echo "Starting uvicorn..."