Heat a splash of oil in a large pot over medium heat until it shimmers and begins to smell aromatic.
Add chopped onions and minced garlic to the pot. Cook, stirring occasionally, until they turn translucent and fragrant, about 5 minutes.
Toss in shredded cooked chicken, stirring for about 2 minutes to warm and combine with the aromatics.
Pour in chicken broth and bring the mixture to a gentle simmer, watching for small bubbles and a fragrant aroma filling the air.
Add sliced carrots and celery to the broth, stirring to distribute evenly. Cook until vegetables are tender but still vibrant, about 8 minutes.
Season the soup with salt and pepper gradually, tasting as you go. Squeeze in fresh lemon juice to brighten the flavor.
Let the soup simmer for another 10 minutes, allowing flavors to meld and the aroma to deepen, with gentle bubbling indicating readiness.
Stir in chopped fresh herbs just before serving to add a burst of freshness and color.
Taste the soup once more and adjust salt, pepper, or lemon if needed for perfect balance.
Remove from heat and ladle the hot, fragrant soup into bowls, ready to enjoy with crusty bread or on its own.
