Put the soaked chickpeas, water, and garlic in a large pot. Bring to a boil, skim once, then simmer partly covered for 70 to 90 minutes until very tender.
Stir in the cumin and salt. Add hot water as needed to keep the broth loose and generous.
Prepare the Toppings:
Cook the eggs to your preferred soft center, then peel them carefully.
Divide the torn bread among six deep bowls. Arrange harissa, tuna, capers, olive oil, lemon, parsley, and extra cumin for serving.
Assemble:
Ladle hot chickpeas and plenty of broth over each bowl of bread. Let stand for 1 minute.
Top each bowl with an egg, harissa, tuna, capers, olive oil, parsley, cumin, and a squeeze of lemon. Serve immediately.
Notes
The chickpeas should be very tender but still hold their shape.
For a vegetarian bowl, omit the tuna and add extra capers and olive oil.