Your post is quite intriguing and interesting, but I am not able to follow this last modus ponens. So if the reason why the Shivans are erratic and inneficient is because they cannot be rational or methodical (and thus predictable), why is it necessary a third force, now one of Chaos, to be detrimental to the destruction of sentience? Taking the premisse for granted, I'd say the Shivans are the perfect example of such a force of Chaos. And while I understand how the Shivans suddenly behaving rationally could be disastrous to the universe (some interesting plot point), I really don't understand your "Therefore GD is chaos that destroys sentience".
Some very cool ideas behind this incoherent bungle of words, Ryan. Why are you so sure of the Shivan's purpose? And if that is true, and if it is also true that the Shivans are a "mathematical consequence of the laws of the universe", then one should question why the universe is so "anthropically principled" (or more rigorously, sentient principled). I'd also question your "ensures the ongoing preservation of all sentient life". Clearly the Ancients and the almost total wiping out of humanity and the vasudans falsify this notion completely.
Lastly, I think your idea about humanity being a nagari backdoor for the GD is a very interesting and worthy idea. I'll keep it in mind.
That's cute. I would however not try to see the plot like that, it kinda diminishes the scope and ruins the vertigo by converting the whole thing into a simplistic organic metaphor or analogy. Given all that has been said and the jargon shared by Battuta I'd argue that they are trying to write something much, much deeper than that.
Intelligence exists independently of sentience. Or it can in theory, at least. I suspect the Shivans are an example of this. All of their behaviour in the canonical FS universe and now BP speaks of great intelligence, but without sentient rationality. They operate on what appear to be pre-programmed probabilities with built-in randomness, as indicated by Noemi and Ken's discussion about efficiency, and UT makes that abundantly clear when you scan the comm nodes. So the Shivans can be a hyper-intelligent manifestation (I hesitate to call them a species, as they are made up of biomechanical components which serve as quantum-state computers) that isn't actually self-aware or rational. They exist merely for a purpose, which they carry out based on heuristics. It's not rational, and therefore not predictable.
The comm nodes use a lot of biologically-analogous language that sounds like a discussion of immunity. And the Shivans function in a manner completely analogous to an immune system. They have sentries, that detect localized threats. They begin with a generic response. As the 'infection' fights the generic response, they in turn adapt to the mechanisms the 'infection' uses to evade detection or counterattack. They develop more and more selective mechanisms to deal with the infection, until it is dealt with in a manner that satisfies their heuristics. Then, they return to sentry state while preserving the memory and ability to counteract that specific type of threat and allow them to escalate and motivate their response that much quicker the next time.
With regard to the mathematical origins of the Shivans, I don't mean they simply manifested. I mean that at least one species, if not many, early in the history of the universe either became the Shivans through evolution and necessity - recognizing that the GD has always existed and the only way to counter that threat was to preserve themselves as a universe immune system - or they evolved as a hyper-intelligent but non-sentient species that was able to develop technology and use it to enhance themselves. In the second scenario, the Shivans are a probabilistic outcome in the universe.
With regard to Shivans being preservers of sentient life, again the biological analogues: easier to cut out an infection that threatens the whole organism (one sentient species among all of those in the whole universe) than allow the destruction of the whole organism.
The Shivans appear to have no fear and face no threat from the Great Darkness. I suspect this is because the Shivans are intelligent, but not sentient. Conversely, the Vishnans are both. Humanity is both, and the Vasudans are both. The Nagari progress of humanity appears to me as a way the Great Darkness can invade the Nagari process generally. Notice Ken also has no real fear of the GD either; his fear is for Noemi. And in the situations where you do allow Noemi to be intercepted by the GD or allow her mental state to degrade, you get the same sequence and the end-state is the destruction of her mind. Sentients who are rational and predictable are vulnerable to destruction by the GD. The Shivans are an intelligence construct that are not. Similarly, the Vishnans appear to either be unaware of or are unaffected by the GD also, perhaps because they are no longer organisms-as-such. It makes me suspect the GD is a threat to Nagari-capable sentient but biological organisms, but its infection of them (be it the dead Ancients, the Humans, or the Vasudans) could allow it unfettered access to the Nagari network which would destroy any other, even non-physical/biological, sentient race also capable of using that network.
I don't even know that the GD is an external force to biologicals. It seems to accompany Noemi, generally. I suspect it may be a feature of huamnity's own minds.
Also, I don't think the inclusion of the Sync/Transcend references (and visual stylings in the nebula in UT) are just an Easter egg or unimportant part of the story. The Sync drive interacted with subspace in a novel way. The Nagari network exists as a part of subspace. The Transcendant appears to have developed from an accidental consequence of the Sync drive. The Transcendant features in a couple parts of UT (and parts of UT play out very similarly to parts of Sync/Transcend).
It's difficult to piece together the entire picture with its various plot twists from what we have so far, but I suspect the following (to summarize):
-The Shivans are the universe's immune system. They are a biomechanical quantum-state computer that exists to predict possible outcomes and ensure the survival of sentient life in the universe, generally. They have existed since the beginnings of the Universe, and are the oldest species (they claim as much).
-The Vishnans are a hyper-intelligent sentient race, that inherited the caretaking of all sentient life after the destruction of the Brahmans in the First Apocalypse, which I suspect was the destruction of all Nagari-linked sentient life by the GD. I'm betting this is a cycle that repeats itself, a cycle that the Shivans exist to prevent.
-The Great Darkness is not a thing so much as a lack of thing, a force that leads to the destruction of sentient/rationalistics minds. The Shivans, not being sentient or rational, are immune to it. The Vishnans exist as creatures of subspace and are technically immune to it. All sentient life, however, can link to Nagari and Nagari is the means by which the GD can jump from individual to individual and species to species.
-The Transcendant touched or interacted with the GD courtesy of Nagari interactions produced by the Sync drive.
-The Ancients, Vasudans, and Humanity are all vulnerable to the GD, and were/are all Nagari-linked.
-War between biological sentients has a calculated probability of producing a weapon or technology which, if activated, will ultimately lead to the introduction by the GD to all Nagari-capable sentient life.
This is why the Vishnans and Shivans are now bent on the destruction of humanity. The deployment of the UEF superweapon could lead to the destruction of all sentient life, and this is why Ken says Noemi has to end the war as quickly as possible. The weapon was originally designed to be used against the Shivans, but has become much more than that. If the war ends with the deployment of the weapon against the GTVA, or ends by another means but the weapon is deployed against the Shivans, the consequences for all sentient life in the universe are unspeakable. The weapon is Vishnan-inspired technology, and this is why Ken says Noemi is to use the Fedayeen and dissociate from the Elders - they are compromised by the Vishnans, and in doing what the Vishnans ask could inadvertently trigger destruction on a universal scale.
...hey BP team, am I close? =P