Time as Actualization: A foundational ontology reconciling the quantum future and the relativistic past

Version v4 (July 2026). (1) The covariance section is refined: strong coupling by itself preserves the rest-mass (Casimir) scalarity of the tempo ν, the open residue being the absence of a shared rest frame (fields / non-comoving constituents). (2) Canon-robustness audit: the derivation of the structural arrow (D1) now credits H8 (single-world, non-branching) explicitly; the thermodynamic value in D6 is stated as an argued posit, not derived; minor status/synchronisation corrections throughout. We present Time–Actualization (TA), a foundational ontology for physics built on a single move: quantum mechanics describes the potential future, general relativity describes the actualized past, and the present is the process of actualization that converts the former into the latter. The ontology is a minimal triplet (ρ, ν, ⟨P,≺⟩): a positive normalized state ρ on a local net of algebras (the conditional future potential), a primitive tempo ν (the rate of becoming), and a growing causal set ⟨P,≺⟩ (the past). TA assumes the quantum formalism and the relativistic causal structure as imported building blocks; it does not attempt to derive the Born rule, Einstein's equations, or the constants. From eight core hypotheses we obtain a sequence of consequences: a structural arrow of time prior to thermodynamics (D1); the dissolution of the measurement problem (D2), of the EPR paradox (D3) and of the worry about superluminal signalling (D4); a causally determined preferred basis (D5) — the actualization basis is einselected by the event's causal past, rather than posited; a thermodynamic arrow via Landauer–Jaynes–Spohn (D6); and a conditional coherence lemma: the actualization dynamics is generally covariant and Bell-causal (no-signalling) once the substrate carries the standard locality of physics (D7). We then develop the physics of TA's own primitive, the tempo ν: a no-new-constant saturation law that pins it to the energy uncertainty, an emergent invariant proper time Σν⁻¹, and a closed signature gate — all empirically silent. We argue that measurement, becoming, and causal-set growth are one process. We are explicit that TA is empirically equivalent to (quantum mechanics + a causal-set substrate): it makes no distinctive prediction, its sole observational signature being the generic causal-set "swerve" inherited from discreteness. Its contribution is ontological clarity and a unifying reading, not a new number. We position TA among the interpretations of quantum mechanics and the philosophies of time, and we state honestly the three problems it leaves open — and why each is, by construction, not TA's to close.