castbar, nameplates: update the shield on mid-cast interruptible changes

modules/castbar.lua

@@ -345,6 +345,12 @@ pfUI:RegisterModule("castbar", function ()
     elseif unitstr == "focus" then
       cb:RegisterEvent("PLAYER_FOCUS_CHANGED")
     end
+    -- The shield can flip mid-cast (the caster gains or loses an aura that
+    -- blocks interrupts). These only fire for target and focus.
+    if unitstr == "target" or unitstr == "focus" then
+      cb:RegisterUnitEvent("UNIT_SPELLCAST_INTERRUPTIBLE", unitstr)
+      cb:RegisterUnitEvent("UNIT_SPELLCAST_NOT_INTERRUPTIBLE", unitstr)
+    end
 
     cb:SetScript("OnEvent", function()
       local unit = this.unitstr
@@ -400,6 +406,10 @@ pfUI:RegisterModule("castbar", function ()
         if not this.tradeskillTotal then ClearBar(this) end
       elseif event == "UNIT_SPELLCAST_FAILED" or event == "UNIT_SPELLCAST_INTERRUPTED" then
         ClearBar(this, true)
+      elseif event == "UNIT_SPELLCAST_INTERRUPTIBLE" or event == "UNIT_SPELLCAST_NOT_INTERRUPTIBLE" then
+        if this.endTime then
+          SetCastbarShield(this.bar, this.icon, event == "UNIT_SPELLCAST_NOT_INTERRUPTIBLE", this.isChannel)
+        end
       elseif event == "UNIT_SPELLCAST_DELAYED" or event == "UNIT_SPELLCAST_CHANNEL_UPDATE" then
         -- Pushback: a cast delayed later or a channel shortened. Following
         -- Quartz, re-poll just the times and accumulate the shift into a running

modules/nameplates.lua

@@ -519,6 +519,10 @@ nameplates:RegisterEvent("UPDATE_MOUSEOVER_UNIT")
 -- plate's own frame, against its own token -- see OnCreate and
 -- NAME_PLATE_UNIT_ADDED.
 nameplates:RegisterEvent("PLAYER_GUILD_UPDATE")
+-- The interruptible flips only fire for target and focus, not nameplate
+-- tokens. castState is keyed by GUID, so they still reach those units' plates.
+nameplates:RegisterUnitEvent("UNIT_SPELLCAST_INTERRUPTIBLE", "target", "focus")
+nameplates:RegisterUnitEvent("UNIT_SPELLCAST_NOT_INTERRUPTIBLE", "target", "focus")
   
   nameplates:SetScript("OnEvent", function()
     -- Stop event handling during logout to prevent crash 132
@@ -680,6 +684,17 @@ nameplates:RegisterEvent("PLAYER_GUILD_UPDATE")
       -- Also propagate to all plates for alpha/strata updates
       this.eventcache = true
 
+    elseif event == "UNIT_SPELLCAST_INTERRUPTIBLE" or event == "UNIT_SPELLCAST_NOT_INTERRUPTIBLE" then
+      local guid = UnitGUID(arg1)
+      local info = guid and castState[guid]
+      local plate = info and plateByGuid[guid]
+      if plate and plate.castbar then
+        info.noInterrupt = event == "UNIT_SPELLCAST_NOT_INTERRUPTIBLE"
+        -- UpdateCastbar only restyles on a new cast; force it
+        plate.castbar.lastEndTime = nil
+        plate.castUpdate = true
+      end
+
     elseif event == "PLAYER_COMBO_POINTS" or event == "UNIT_COMBO_POINTS" then
       -- Only flag the target's plate for combo point update
       local plate = C_NamePlate.GetNamePlateForUnit("target")