Preheat oven to 400°F (200°C); halve spaghetti squash, remove seeds, oil and salt, then roast cut-side down for 35–45 minutes
Shred cooked squash into strands with a fork; set aside
Heat oil or butter in a large pot over medium heat
Sauté onion and celery for 4–5 minutes until softened
Add garlic and cook 30 seconds until fragrant
Add chicken, salt, pepper, thyme, oregano, turmeric, and bay leaf
Pour in chicken broth; bring to a gentle boil
Reduce heat, cover, and simmer 25–30 minutes until chicken is cooked
Remove chicken, shred, and return to the pot
Stir in spaghetti squash and simmer uncovered 5–7 minutes
Remove bay leaf, add lemon juice if using, adjust seasoning
Garnish with fresh parsley and serve hot