Assessing Cosmological Evidence for String Theory: A Comparative Provenance Analysis of Cosmic Superstrings, Inflation, and Axion Sectors

String theory provides a well-developed framework for quantum gravity, but direct tests at microscopic string or Planck scales are beyond present experimental reach. Cosmology offers an indirect route because the early universe can preserve observable consequences of ultraviolet physics. Cosmic superstrings, string-inspired inflation, axion sectors, primordial black holes, and gravitational-wave backgrounds are therefore frequently discussed as possible observational windows on string theory. This paper compares three prominent classes of proposed signatures, cosmic superstrings, string-inspired inflation, and axion-like relics, with the narrower question of how strongly an observation could identify a string-theoretic origin. The comparison uses three qualitative criteria: pre-observation restriction, resistance to non-string mimicry, and correlated-observable potential. The term provenance is used for the extent to which an observable or linked set of observables retains information about the ultraviolet construction that generated it. Under these criteria, cosmic superstrings currently provide the clearest near-term route to high-provenance evidence if network microphysics can be measured, while generic inflationary observables remain strongly degenerate with non-string models. A single axion-like particle has low provenance value, but a structured spectrum or an experimentally measured relation to compactification data can be substantially more informative. The ranking is qualitative and conditional, but the central ordering is stable under reasonable changes in emphasis among the three criteria. A high-provenance candidate is required to satisfy a minimum decision rule: at least moderate pre-observation restriction, at least moderate resistance to non-string mimicry once the relevant microphysics is resolved, and high correlated-observable potential. Under this rule, cosmic superstrings can qualify if network microphysics is measured, structured axion sectors can qualify in sufficiently constrained cases, and generic inflationary observables do not. Recent comparisons with data also show that restricted string-cosmology models can already be constrained or disfavored even when the broader framework is not directly tested. The analysis therefore separates two empirical questions that are often conflated: whether string theory can produce observable cosmology, and whether an observed cosmological signal can identify string theory as its microscopic origin.