Digital systems are becoming more integrated, autonomous, and cooperative. AI agents, future mobile networks, and machine-to-machine economies point to one trend: spontaneous, cross-organizational, unplanned interactions between non human entities (NHEs). Trust establishment for them remains an open problem. Federation is the natural candidate, but established approaches, from OpenID Federation 1.0 and SAML to Federated Identity Management, presuppose what this setting denies them: manual, ahead-of-time configuration and a common trust anchor, whether pre-established members or a shared provider. Trust domains must therefore federate without being prefigured to do so: plan for unplanned interactions. This paper examines whether prominent Identity and Access Management (IAM) approaches, namely SPIRE, Workload Identity Federation (WIF), and OpenID Federation 1.0, can support such federation. Drawing requirements from disparate fields (medical, mobile networks, agentic AI), it argues that SPIRE is the most promising starting point, but needs three extensions to meet them all: token exchange, letting a home domain mint scoped, audience-bound tokens from a foreign workload's SPIFFE Verifiable Identity Document (SVID); remote attestation, so a trust decision targets a specific workload rather than a whole domain; and a distributed-ledger layer that anchors trust roots, carries federation governance, and publishes the shared keys the other two depend on.

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