Identity Collapse Taxonomy

This paper introduces the first formal taxonomy of identity collapse grounded in the four-layer identity decomposition (substrate, execution, behavioral structure, attestation). Identity collapse is defined as the structural failure of execution-realized identity, expressed as the negation of Φ-coherence across organization, generative model, and provenance. The taxonomy classifies collapse into layer-specific failure modes (s-collapse, e-collapse, b-collapse, a-collapse), drift propagation patterns, and temporal collapse forms including lineage break, identity bifurcation, identity fork, and drift accumulation. The framework is empirically validated across software supply chains, SBOM provenance systems, reproducible build ecosystems, microservice architectures, WASM component identity, OCI artifact distribution, and digital thread implementations. The taxonomy integrates evidence from behavioral equivalence studies, dependency drift analyses, runtime drift in cloud systems, and digital twin divergence, demonstrating that identity collapse is a structured, diagnosable phenomenon rather than an anomaly. This work completes the doctrinal arc of substrate-rooted identity by providing the negative ontology: a unified, falsifiable account of how identity fails in modern distributed and cyber-physical systems. It establishes a conceptual foundation for identity-conditioned governance, provenance integrity, behavioral equivalence testing, and long-term lifecycle assurance.