Heat 1 tablespoon olive oil in a large pot over medium heat.
Add the chopped onion and minced garlic. Sauté until the onion is translucent and fragrant, about 3–4 minutes.
Increase heat slightly, add the diced chicken breast, and cook until the pieces are browned on the outside, about 4–6 minutes.
Pour in 4 cups of chicken broth and bring to a gentle boil, scraping any browned bits from the bottom of the pot.
Add the mixed vegetables, salt, black pepper, and thyme. Stir to combine.
Reduce heat to low, cover partially, and let simmer for 20 minutes until vegetables are tender and chicken is cooked through.
Taste and adjust seasoning; serve hot.
Notes
For more protein and texture, add a can of drained chickpeas or white beans towards the end. Use bone-in chicken for extra depth and collagen. Serve with crusty whole-grain bread or buttered toast for dipping.