The CMS Tracker Upgrade for Phase-2: Meeting the Challenges of the HL-LHC

The High-Luminosity Large Hadron Collider (HL-LHC) will significantly increase the instantaneous luminosity of proton-proton collisions, pushing the CMS experiment into a regime of extreme radiation levels, high particle multiplicities, and unprecedented data rates. To maintain and extend the physics performance of the CMS detector under these conditions, a complete replacement of the tracking system is underway as part of the Phase-2 Upgrade. This paper presents the design, goals, and status of the Phase-2 CMS Tracker Upgrade, which includes entirely new silicon pixel and strip detectors with enhanced radiation hardness, finer granularity, and extended pseudorapidity coverage. The upgraded tracker will also feature on-detector data reduction through the use of real-time trigger information, an essential capability for sustaining low trigger thresholds at the HL-LHC. Special emphasis is placed on innovations in sensor technology, powering and cooling strategies, and the mechanical integration of large-scale modular components. We discuss the R\&D, prototyping, and production progress, along with results from recent beam tests and system integration campaigns. The paper will also highlight key challenges in quality assurance, large-scale assembly, and pre-installation testing, as well as the timeline toward installation and commissioning.