What the problem is
Standard ΛCDM Big Bang Nucleosynthesis predicts roughly three times more primordial lithium-7 than astronomers actually see in old metal-poor stars. That mismatch has survived for about forty years. Proposed fixes have ranged from stellar depletion models to reaction-rate revisions to entirely new particle physics, but none has become the accepted lithium problem solution.
That is why the phrase cosmological lithium problem resolved matters: if a framework really matches lithium while still matching deuterium and helium, it is doing something structurally different from the standard one-slot BBN picture.
How the IO framework resolves it
Paper 24 closes the active lithium channel through quadrupole isolation, Gamow amplification, and TT rate dressing. On the active branch the published result is Li-7/H = 1.75 × 10⁻¹⁰, which sits at +0.55σ relative to the Spite-plateau reference. The same framework keeps the rest of the BBN triple in line, with D/H = 2.509 × 10⁻⁵, Y_p = 0.2477, and combined χ² = 1.13.
In other words: BBN lithium resolved, not by fitting lithium directly, but by carrying the same geometric constants through the whole light-element network.
Why it works
The Interior Observer Framework does not use one universal baryon density for every process. The geometric baryon fraction is fixed by f_b = 2γ/x, and the typed α-ladder maps different physical processes into different effective baryon slots. That means the BBN reaction network, the sound-speed sector, and the observer-side readout are not forced into the same one-number closure.
On the BBN side, the key rates see the geometric slot and the thermal dressing appropriate to the reaction channel. That is why the lithium suppression is tied to the same framework that keeps deuterium and helium under control, instead of being a standalone patch.
Why this matters
A convincing lithium problem solution has to do more than lower one abundance. It has to keep the rest of primordial nucleosynthesis intact and explain why the correction lands where it does. The IO result matters because it is part of a broader black hole cosmology with theorem-grade predictions and zero fitted parameters, not an isolated lithium-only adjustment.