Al dente spaghetti still resists the tooth. What boundary has it crossed from raw pasta?

Answer: Starch is hydrated

Starch is hydrated ✓ — Right. The useful boundary is hydration: heat and water have cooked the pasta enough that it is no longer chalky, while the dense center still resists. La Cucina Italiana describes al dente starch as hydrated but not released into the water. The trick is stopping after cooking begins to work, not before.

Starch is leached out — No. If starch has fully leaked, you are past the al dente window and moving toward a softer, stickier noodle. The surprising part is that the same starch can be useful in pasta water for sauce, but losing too much from the noodle means the noodle's own architecture has weakened.

Starch is still dry — No. A firm center is not the same as a dry raw core. In al dente pasta, enough water has moved in to cook away the chalky rawness, but not so much that starch floods out. Bite is controlled hydration, not dryness.