diff --git a/build.gradle.kts b/build.gradle.kts
index a629909d39..6992659e6e 100644
--- a/build.gradle.kts
+++ b/build.gradle.kts
@@ -49,6 +49,7 @@ allprojects {
     apply(plugin = "io.github.yairm210.purity-plugin")
     configure<yairm210.purity.PurityConfiguration>{
         wellKnownPureFunctions = setOf(
+            "kotlin.with",
         )
         wellKnownReadonlyFunctions = setOf(
             "com.badlogic.gdx.math.Vector2.len",
diff --git a/core/src/com/unciv/logic/automation/civilization/ReligionAutomation.kt b/core/src/com/unciv/logic/automation/civilization/ReligionAutomation.kt
index 38017f4014..7d11d1a55f 100644
--- a/core/src/com/unciv/logic/automation/civilization/ReligionAutomation.kt
+++ b/core/src/com/unciv/logic/automation/civilization/ReligionAutomation.kt
@@ -11,6 +11,7 @@ import com.unciv.models.ruleset.BeliefType
 import com.unciv.models.ruleset.unique.GameContext
 import com.unciv.models.ruleset.unique.UniqueType
 import com.unciv.models.stats.Stat
+import yairm210.purity.annotations.Readonly
 import kotlin.math.min
 import kotlin.math.pow
 import kotlin.random.Random
@@ -205,7 +206,7 @@ object ReligionAutomation {
     // endregion
 
     // region rate beliefs
-
+    @Readonly
     fun rateBelief(civInfo: Civilization, belief: Belief): Float {
         var score = 0f // Roughly equivalent to the sum of stats gained across all cities
 
@@ -234,6 +235,7 @@ object ReligionAutomation {
         return score
     }
 
+    @Readonly
     private fun beliefBonusForTile(belief: Belief, tile: Tile, city: City): Float {
         var bonusYield = 0f
         for (unique in belief.uniqueObjects) {
@@ -253,6 +255,7 @@ object ReligionAutomation {
         return bonusYield
     }
 
+    @Readonly
     private fun beliefBonusForCity(civInfo: Civilization, belief: Belief, city: City): Float {
         var score = 0f
         val ruleSet = civInfo.gameInfo.ruleset
@@ -305,6 +308,7 @@ object ReligionAutomation {
         return score
     }
 
+    @Readonly
     private fun beliefBonusForPlayer(civInfo: Civilization, belief: Belief): Float {
         var score = 0f
         val numberOfFoundedReligions = civInfo.gameInfo.civilizations.count {
@@ -411,7 +415,7 @@ object ReligionAutomation {
         // line 4426 through 4870.
         // This is way too much work for now, so I'll just choose a random pantheon instead.
         // Should probably be changed later, but it works for now.
-        val chosenPantheon = chooseBeliefOfType(civInfo, BeliefType.Pantheon)
+        val chosenPantheon = pickBeliefOfType(civInfo, BeliefType.Pantheon)
             ?: return // panic!
         civInfo.religionManager.chooseBeliefs(
             listOf(chosenPantheon),
@@ -461,14 +465,15 @@ object ReligionAutomation {
             if (belief == BeliefType.None) continue
             repeat(beliefsToChoose[belief]) {
                 chosenBeliefs.add(
-                    chooseBeliefOfType(civInfo, belief, chosenBeliefs) ?: return@repeat
+                    pickBeliefOfType(civInfo, belief, chosenBeliefs) ?: return@repeat
                 )
             }
         }
         return chosenBeliefs
     }
 
-    private fun chooseBeliefOfType(civInfo: Civilization, beliefType: BeliefType, additionalBeliefsToExclude: HashSet<Belief> = hashSetOf()): Belief? {
+    @Readonly
+    private fun pickBeliefOfType(civInfo: Civilization, beliefType: BeliefType, additionalBeliefsToExclude: HashSet<Belief> = hashSetOf()): Belief? {
         return civInfo.gameInfo.ruleset.beliefs.values
             .filter {
                 (it.type == beliefType || beliefType == BeliefType.Any)
diff --git a/core/src/com/unciv/logic/map/mapunit/UnitUpgradeManager.kt b/core/src/com/unciv/logic/map/mapunit/UnitUpgradeManager.kt
index 9eec8249a6..a7f4e51fd9 100644
--- a/core/src/com/unciv/logic/map/mapunit/UnitUpgradeManager.kt
+++ b/core/src/com/unciv/logic/map/mapunit/UnitUpgradeManager.kt
@@ -45,6 +45,7 @@ class UnitUpgradeManager(val unit: MapUnit) {
      */
     // Only one use from getUpgradeAction at the moment, so AI-specific rules omitted
     //todo Does the AI never buy upgrades???
+    @Readonly
     fun getCostOfUpgrade(unitToUpgradeTo: BaseUnit): Int {
         // Source rounds to int every step, we don't
         //TODO From the source, this should apply _Production_ modifiers (Temple of Artemis? GameSpeed! StartEra!), at the moment it doesn't
diff --git a/core/src/com/unciv/models/ruleset/unique/IHasUniques.kt b/core/src/com/unciv/models/ruleset/unique/IHasUniques.kt
index 8167020c7e..c0abc4fe01 100644
--- a/core/src/com/unciv/models/ruleset/unique/IHasUniques.kt
+++ b/core/src/com/unciv/models/ruleset/unique/IHasUniques.kt
@@ -82,17 +82,21 @@ interface IHasUniques : INamed {
     @Readonly
     fun requiredTechs(): Sequence<String> = legacyRequiredTechs() + techsRequiredByUniques()
 
+    @Readonly
     fun requiredTechnologies(ruleset: Ruleset): Sequence<Technology?> =
         requiredTechs().map { ruleset.technologies[it] }
 
+    @Readonly
     fun era(ruleset: Ruleset): Era? =
             requiredTechnologies(ruleset).map { it?.era() }.map { ruleset.eras[it] }.maxByOrNull { it?.eraNumber ?: 0 }
             // This will return null only if requiredTechnologies() is empty or all required techs have no eraNumber
 
+    @Readonly
     fun techColumn(ruleset: Ruleset): TechColumn? =
             requiredTechnologies(ruleset).map { it?.column }.filterNotNull().maxByOrNull { it.columnNumber }
             // This will return null only if *all* required techs have null TechColumn.
 
+    @Readonly
     fun availableInEra(ruleset: Ruleset, requestedEra: String): Boolean {
         val eraAvailable: Era = era(ruleset)
             ?: return true // No technologies are required, so available in the starting era.
@@ -103,6 +107,7 @@ interface IHasUniques : INamed {
         return eraAvailable.eraNumber <= ruleset.eras[requestedEra]!!.eraNumber
     }
 
+    @Readonly
     fun getWeightForAiDecision(gameContext: GameContext): Float {
         var weight = 1f
         for (unique in getMatchingUniques(UniqueType.AiChoiceWeight, gameContext))
@@ -160,6 +165,7 @@ interface IHasUniques : INamed {
      *                  In that case only this parameter can be `null`. So if you know it - provide!
      *  @param ruleset  Required if [gameInfo] is null, otherwise optional (but with both null this will simply return `false`).
      */
+    @Readonly
     fun isHiddenFromCivilopedia(
         gameInfo: GameInfo?,
         ruleset: Ruleset? = null
@@ -187,13 +193,14 @@ interface IHasUniques : INamed {
         return false
     }
     /** Overload of [isHiddenFromCivilopedia] for use in actually game-agnostic parts of Civilopedia */
-    fun isHiddenFromCivilopedia(ruleset: Ruleset) = isHiddenFromCivilopedia(UncivGame.getGameInfoOrNull(), ruleset)
+    @Readonly fun isHiddenFromCivilopedia(ruleset: Ruleset) = isHiddenFromCivilopedia(UncivGame.getGameInfoOrNull(), ruleset)
 
     /** Common for Religion/Espionage: Hidden check when no game is loaded
      *  @param hasFeature Best guess from the Ruleset whether the feature is available
      *  @param enabler The modifier testing feature is on: `ConditionalReligionEnabled` or `ConditionalEspionageEnabled`
      *  @param disabler The modifier testing feature is off: `ConditionalReligionDisabled` or `ConditionalEspionageDisabled`
      */
+    @Readonly
     private fun shouldBeHiddenIfNoGameLoaded(hasFeature: Boolean, enabler: UniqueType, disabler: UniqueType): Boolean {
         for (unique in getMatchingUniques(UniqueType.OnlyAvailable, GameContext.IgnoreConditionals)) {
             if (unique.hasModifier(enabler)) return !hasFeature