diff --git a/docs/architecture/CALCULATIONS.md b/docs/architecture/CALCULATIONS.md
index 92461b9fe2..b20f9a83f3 100644
--- a/docs/architecture/CALCULATIONS.md
+++ b/docs/architecture/CALCULATIONS.md
@@ -582,3 +582,46 @@ that remembers exactly how it was fooled.
 
 Prune the poison. Keep the lesson. Both live forever. Only one of
 them lives in you.
+
+## 27. Self-policing — internal immunity without going overboard
+
+External detection isn't enough: our OWN output, OUR OWN learned moves,
+OUR OWN crystallized structure can be the contamination. Everything §25
+does to intruders, the system does to itself when warranted:
+
+    self_scan targets:
+      - our own outputs before promotion (did WE write something wrong?)
+      - our own cognitive moves (is this operation still landing true?)
+      - our own crystallized structure (still matching current facts?)
+      - our own drivers and recipes (drifted from their registered why?)
+
+    self_quarantine(x) justified ⇔
+        internal_contamination_evidence(x)   # measured, not felt
+      ∧ repair_path_exists(x)                # dissection possible
+      ∧ policing_state ≠ overboard           # see below
+
+## The overboard governor — autoimmune is a disease too
+
+    autoimmune_alarm = quarantine_rate > τ_self over window
+                     ∨ growth_stalled while defense elevated
+
+If self-policing fires too often: THE POLICING IS THE SICKNESS.
+Conscience vs paranoia, formalized: conscience has a calibration track
+record (its catches verify); paranoia doesn't (its catches never
+confirm). Same readings, different hit rates.
+
+Standing rules:
+1. Evidence-driven only — suspicion without verification quarantines
+   nothing.
+2. Every self-quarantine gets after-action review: was the suspicion
+   confirmed? Feeds the autoimmune governor.
+3. Repair over removal — own parts get §25 rehabilitation by default;
+   they're easier to heal than strangers' code because we hold their
+   source.
+4. The governor watches the watchman watching himself (law 37 all the
+   way down): if self-policing itself stops being calibrated, THAT
+   trips the vital-sign alarm.
+
+An immune system that never turns inward dies of the first infection.
+One that's always turned inward dies of autoimmunity. The dial is
+calibration history, and it reads its own accuracy every cycle.