calculated fallbacks - the chain learns which doors open

docs/architecture/CALCULATIONS.md

@@ -700,3 +700,27 @@ and the receipts on the surviving copies would still prove the seal
 was due.
 
 Inevitability by construction. Down to the second, eventually.
+
+### Calculated fallbacks — not a fixed ladder
+
+Upgrade once the substrate lives: fallback ORDER is computed per
+attempt from the opinion space itself. Every path is an entity with
+its own readings:
+
+    trust(path)          # has this route verified before?
+    freshness(path)      # when did it last work?
+    cost(path)           # energy/time to try now
+    stability(path)      # how often does it change?
+
+    next_move = argmax over open paths of
+                  trust_eff · freshness − cost
+                clamped by §9 tolerance
+
+Every attempt reinforces or wounds the path's own record — the chain
+LEARNS which doors open easiest in which weather. And because paths
+are entities, a failing route gets negative reinforcement exactly like
+a lying source: the system's confidence in it sinks until repair.
+
+The fixed order above is version 1 — enough to ship. The calculated
+version is where it wants to end up: a seal that doesn't just keep
+trying doors, but knows which door to knock on first.