Composability Creates Its Own Integrity Problem: Integrity and Answerability Conditions for Tokenised Wholesale Markets

This paper is technology-neutral and is not an argument against composability; it accepts the composable design and specifies the conditions under which such an ecosystem can be relied upon. It is intended to serve two purposes: as the governance companion to the composability proposal of Hunt and Whyman, and as the basis of a response to the joint Call for Input on the future of tokenisation issued by the Financial Conduct Authority and the Bank of England on 18 May 2026. Composability is not only a technical design choice; it is a relocation of market reliance. Reconstructing financial instruments from a common, reusable grammar of title and entitlement tokens moves the basis of reliance out of asset-specific silos and into shared, self-executing components. That relocation does not remove risk; it relocates it. Once instruments are assembled from shared components, the reliability of the whole ecosystem depends on the integrity of those components, the authority under which they self-execute, and the contestability of the mappings between token-state and legal or economic entitlement. This paper specifies the governance layer that the leading UK composability proposal expressly defers. It sets out four integrity conditions — data, system, epistemic and mandate integrity — for composable infrastructure; it argues that such infrastructure can ‘fail without crashing’, remaining available and immutable while the meaning relied upon has degraded; it proposes a ‘mandate envelope’ that extends, rather than replaces, the entitlement-token grammar, so that self-execution remains bounded by authority; and it sets out a minimum integrity-and-answerability framework, anchored in existing UK regulatory instruments, specifying the conditions under which participants, regulators, central counterparties, custodians, courts and investors may rely on a tokenised representation. The argument is offered as the governance companion to the composability proposal and as a contribution to the Call for Input issued by the Financial Conduct Authority and the Bank of England on 18 May 2026.