Feedback-free star formation in clusters within a galaxy simulated at high resolution in cosmic dawn

We perform a cosmological zoom-in simulation of a massive galaxy ((Formula presented) at (Formula presented)) using the GIZMO code. By employing (Formula presented) resolution and a (Formula presented) supernova feedback delay, we capture the feedback-free starbursts (FFBs) in clusters. The simulation reproduces FFB model predictions and super-bright galaxies observed by James Webb Space Telescope (JWST). At (Formula presented), cold streams feed a compact galaxy ((Formula presented)), with stellar and surface densities ((Formula presented), (Formula presented)) exceeding FFB thresholds. The global star-formation efficiency (SFE) is (Formula presented), associated with a fluctuating star-formation history. We identified over (Formula presented) star clusters ((Formula presented)) with a nearly scale-free mass distribution ((Formula presented)). Approximately 90 per cent of star formation occurs in clusters, which at a given time constitute (Formula presented) of the total stellar mass. The star formation in most of the clusters of masses (Formula presented), occurs in bursts of (Formula presented) and a local SFE (Formula presented). Cluster metallicities ((Formula presented)) indicate rapid baryon recycling. Feedback-driven outflows exhibit typical temperature of (Formula presented) and typical velocities of (Formula presented). In the highly dynamic central (Formula presented), clusters undergo rapid orbital decay and merge to assemble the oblate nuclear stellar cluster. Cluster shapes range from oblate to prolate, with a triaxial median. These clusters are consistent with JWST observations, and a fraction of them may survive to yield the globular clusters at low redshifts.