Schematic illustration of the two-jet scenario. Phase I: the primary jet J1 produces prompt gamma-ray emission. Phase II: the second jet J2 is launched after a time delay (Δt). For aligned jets (left), the relative speed determines whether J2 collides violently (Γ₂ > Γ₁) or merges gradually (Γ₂ < Γ₁). For misaligned jets (right), the line of sight determines the observed signal: a normal GRB with late-time radio lobes if aligned with J1, or a fast X-ray transient followed by off-axis rebrightening if aligned with J2.