Cathepsin leakage from aging lysosomes does more than damage cytosolic proteins; it remodels the nuclear landscape to lock cells into a senescence‑associated state that disables the very autophagy arm needed for stress rationing. When cystatin B (CSTB) falls, cathepsin L escapes lysosomes, cleaves histone H3 tails in the nucleus, and drives a chromatin signature that silences stress‑responsive genes, including those encoding LAMP2A and HSPA8【https://www.frontiersin.org/journals/molecular-neuroscience/articles/10.3389/fnmol.2022.1069122/full】. This epigenetic block prevents the upregulation of chaperone‑mediated autophagy (CMA) precisely when the cell needs to selectively degrade damaged proteins under oxidative siege【https://pmc.ncbi.nlm.nih.gov/articles/PMC7388076/】. Simultaneously, cytosolic cathepsin L degrades LAMP2A at the lysosomal membrane, creating a double hit: transcriptional repression plus post‑translational loss of the CMA receptor【https://pmc.ncbi.nlm.nih.gov/articles/PMC9221958/】. The result is a shift from selective, adaptive autophagy to non‑selective bulk degradation or outright autophagy failure, converting a rationing system into a futile cycle of self‑cannibalism that accelerates cellular decline. We hypothesize that restoring nuclear histone H3 integrity—either by genetic knock‑in of cleavage‑resistant H3 mutants or by pharmacological inhibition of cathepsin L nuclear import—will reactivate CMA flux, reduce senescence markers, and improve lysosomal membrane integrity in aged cells. This hypothesis is testable: (1) treat primary fibroblasts from old mice with a cathepsin L‑specific inhibitor that does not cross the lysosomal membrane but blocks nuclear cathepsin L (e.g., a cell‑permeable, lysosomotropic‑blocked probe); (2) measure CMA activity using a KFERQ‑GFP reporter, LAMP2A levels by western blot, and histone H3 cleavage by immunoprecipitation with an anti‑cleaved H3 antibody; (3) assess senescence via SA‑β‑gal and SASP cytokine secretion; (4) evaluate lysosomal membrane permeabilization with galectin‑3 puncta formation. Prediction: nuclear cathepsin L inhibition will increase LAMP2A transcription and protein stability, boost CMA flux, lower SA‑β‑gal positivity, and reduce galectin‑3 puncta compared with vehicle【https://www.archivesofmedicalscience.com/Cystatins-unravelling-the-biological-implications-for-neuroprotection,171706,0,2.html】. Conversely, forcing expression of a cleavage‑resistant H3.3 mutant should phenocopy the inhibitor effect, confirming that histone H3 cleavage is a critical node linking lysosomal leakage to autophagy failure【https://scholars.direct/Articles/neurodegenerative-disorders/jnd-4-017.php?jid=neurodegenerative-disorders】. If these predictions hold, the siege metaphor gains mechanistic precision: autophagy inhibition is not merely a consequence of resource scarcity but is actively enforced by cathepsin‑driven chromatin remodeling that shuts down the cell’s rationing circuitry.