Combine the warm water at roughly 105°F with the rye flour, bread flour, whole wheat flour, cocoa powder, instant dry yeast, brown sugar, salt, and vegetable oil in a food processor bowl or large mixing vessel. Ensure the water feels barely warm to the touch so the yeast activates without being damaged.

Process the ingredients for approximately 5 minutes until a soft, sticky dough pulls slightly away from the container sides, or stir vigorously with a wooden spoon until a uniform paste forms. The finished mixture should look dark, glossy, and noticeably tackier than ordinary bread dough.

Cover the bowl tightly with plastic wrap and let the dough rest at room temperature for 1 hour and 30 minutes. Look for the dough to become visibly puffy, expanded, and aerated rather than fully doubled in volume.

Turn the soft dough onto a surface generously dusted with rye flour to shape into a log, or scrape it directly into an oiled loaf pan using damp hands to smooth the top surface. A lightly moistened spatula or wet fingertips will prevent the tacky dough from tearing as you shape it.

Cover the shaped dough loosely with a clean towel and let it proof undisturbed for 40 minutes. The dough should swell gently and fill out the pan or hold a rounded mound shape on the baking sheet.

Transfer the loaf to an oven preheated to 425°F (220°C) and bake for 35 to 40 minutes. The crust should feel firm and produce a distinct hollow sound when tapped gently on the top.

Place the baked bread onto a wire cooling rack and allow it to cool completely before cutting into slices. Cooling lets internal starches stabilize so each slice cuts cleanly without gumminess.