Shred the rotisserie chicken into bite‑size pieces and set aside.
Warm the olive oil in a large pot over medium heat.
Add onion, carrots, and celery; cook until softened, 6–8 minutes, stirring occasionally.
Stir in garlic and thyme; cook until fragrant, about 30 seconds.
Pour in the chicken broth and bring to a boil. Reduce to a lively simmer for 10 minutes.
Add egg noodles and cook until just shy of tender, 5–6 minutes.
Stir in shredded chicken and bouillon, if using; simmer 2–3 minutes to heat through.
Finish with lemon juice and parsley. Season with salt and pepper to taste, then serve.