diff --git a/core/src/com/unciv/models/ruleset/validation/UniqueValidator.kt b/core/src/com/unciv/models/ruleset/validation/UniqueValidator.kt
index b934bb9860..f6b0240e6b 100644
--- a/core/src/com/unciv/models/ruleset/validation/UniqueValidator.kt
+++ b/core/src/com/unciv/models/ruleset/validation/UniqueValidator.kt
@@ -15,6 +15,8 @@ import com.unciv.models.ruleset.unique.UniqueParameterType
 import com.unciv.models.ruleset.unique.UniqueTarget
 import com.unciv.models.ruleset.unique.UniqueType
 import com.unciv.models.ruleset.unique.expressions.Expressions
+import yairm210.purity.annotations.Cache
+import yairm210.purity.annotations.LocalState
 import yairm210.purity.annotations.Readonly
 
 class UniqueValidator(val ruleset: Ruleset) {
@@ -74,7 +76,7 @@ class UniqueValidator(val ruleset: Ruleset) {
         val prefix by lazy { getUniqueContainerPrefix(uniqueContainer) + "\"${unique.text}\"" }
         if (unique.type == null) return checkUntypedUnique(unique, tryFixUnknownUniques, uniqueContainer, prefix, reportRulesetSpecificErrors)
 
-        val rulesetErrors = RulesetErrorList(ruleset)
+        @LocalState val rulesetErrors = RulesetErrorList(ruleset)
 
         if (uniqueContainer != null &&
             !(unique.type.canAcceptUniqueTarget(uniqueContainer.getUniqueTarget()) ||
@@ -107,11 +109,11 @@ class UniqueValidator(val ruleset: Ruleset) {
                 complianceError.errorSeverity.getRulesetErrorSeverity(), uniqueContainer, unique
             )
 
-            addExpressionParseErrors(complianceError, rulesetErrors, uniqueContainer, unique)
+            rulesetErrors += getExpressionParseErrors(complianceError, uniqueContainer, unique)
         }
 
         for (conditional in unique.modifiers) {
-            addConditionalErrors(conditional, rulesetErrors, prefix, unique, uniqueContainer, reportRulesetSpecificErrors)
+            rulesetErrors += getConditionalErrors(conditional, prefix, unique, uniqueContainer, reportRulesetSpecificErrors)
         }
 
         addUniqueTypeSpecificErrors(rulesetErrors, prefix, unique, uniqueContainer, reportRulesetSpecificErrors)
@@ -128,7 +130,6 @@ class UniqueValidator(val ruleset: Ruleset) {
             }
         }
 
-
         if (unique.type in MapUnitCache.UnitMovementUniques
                 && unique.modifiers.any { it.type != UniqueType.ConditionalOurUnit || it.params[0] !in Constants.all }
             )
@@ -149,13 +150,14 @@ class UniqueValidator(val ruleset: Ruleset) {
         return rulesetErrors
     }
 
-    private fun addExpressionParseErrors(
+    @Readonly
+    private fun getExpressionParseErrors(
         complianceError: UniqueComplianceError,
-        rulesetErrors: RulesetErrorList,
         uniqueContainer: IHasUniques?,
         unique: Unique
-    ) {
-        if (!complianceError.acceptableParameterTypes.contains(UniqueParameterType.Countable)) return
+    ): RulesetErrorList {
+        @LocalState val rulesetErrors = RulesetErrorList()
+        if (!complianceError.acceptableParameterTypes.contains(UniqueParameterType.Countable)) return rulesetErrors
 
         val parseError = Expressions.getParsingError(complianceError.parameterName)
         if (parseError != null) {
@@ -167,7 +169,7 @@ class UniqueValidator(val ruleset: Ruleset) {
             val text = "\"${complianceError.parameterName}\" could not be parsed as an expression due to:" +
                     " ${parseError.message}. \n$parameterWithErrorLocationMarked"
             rulesetErrors.add(text, RulesetErrorSeverity.WarningOptionsOnly, uniqueContainer, unique)
-            return
+            return rulesetErrors
         }
 
         val countableErrors = Expressions.getCountableErrors(complianceError.parameterName, ruleset)
@@ -176,6 +178,7 @@ class UniqueValidator(val ruleset: Ruleset) {
                     " ${countableErrors.joinToString(", ")}"
             rulesetErrors.add(text, RulesetErrorSeverity.WarningOptionsOnly, uniqueContainer, unique)
         }
+        return rulesetErrors
     }
 
     private val resourceUniques = setOf(UniqueType.ProvidesResources, UniqueType.ConsumesResources,
@@ -188,21 +191,21 @@ class UniqueValidator(val ruleset: Ruleset) {
         UniqueType.ConditionalWhenBelowAmountStatResource,
     )
 
-    private fun addConditionalErrors(
+    private fun getConditionalErrors(
         conditional: Unique,
-        rulesetErrors: RulesetErrorList,
         prefix: String,
         unique: Unique,
         uniqueContainer: IHasUniques?,
         reportRulesetSpecificErrors: Boolean
-    ) {
+    ): RulesetErrorList {
+        @LocalState val rulesetErrors = RulesetErrorList()
         if (unique.hasFlag(UniqueFlag.NoConditionals)) {
             rulesetErrors.add(
                 "$prefix contains the conditional \"${conditional.text}\"," +
                     " but the unique does not accept conditionals!",
                 RulesetErrorSeverity.Error, uniqueContainer, unique
             )
-            return
+            return rulesetErrors
         }
 
         if (conditional.type == null) {
@@ -221,7 +224,7 @@ class UniqueValidator(val ruleset: Ruleset) {
                 text,
                 RulesetErrorSeverity.Warning, uniqueContainer, unique
             )
-            return
+            return rulesetErrors
         }
 
         if (conditional.type.targetTypes.none { it.modifierType != UniqueTarget.ModifierType.None })
@@ -276,10 +279,11 @@ class UniqueValidator(val ruleset: Ruleset) {
                 complianceError.errorSeverity.getRulesetErrorSeverity(), uniqueContainer, unique
             )
 
-            addExpressionParseErrors(complianceError, rulesetErrors, uniqueContainer, unique)
+            getExpressionParseErrors(complianceError, uniqueContainer, unique)
         }
 
         addDeprecationAnnotationErrors(conditional, "$prefix contains modifier \"${conditional.text}\" which", rulesetErrors, uniqueContainer)
+        return rulesetErrors
     }
 
     private fun addUniqueTypeSpecificErrors(
@@ -334,11 +338,12 @@ class UniqueValidator(val ruleset: Ruleset) {
     }
 
     /** Maps uncompliant parameters to their required types */
+    @Readonly
     private fun getComplianceErrors(
         unique: Unique,
     ): List<UniqueComplianceError> {
         if (unique.type == null) return emptyList()
-        val errorList = ArrayList<UniqueComplianceError>()
+        @LocalState val errorList = ArrayList<UniqueComplianceError>()
         for ((index, param) in unique.params.withIndex()) {
             // Trying to catch the error at #11404
             if (unique.type.parameterTypeMap.size != unique.params.size) {
@@ -363,11 +368,12 @@ class UniqueValidator(val ruleset: Ruleset) {
         return errorList
     }
 
-    private val paramTypeErrorSeverityCache = HashMap<UniqueParameterType, HashMap<String, UniqueType.UniqueParameterErrorSeverity?>>()
+    @Cache private val paramTypeErrorSeverityCache = HashMap<UniqueParameterType, HashMap<String, UniqueType.UniqueParameterErrorSeverity?>>()
+    @Readonly
     private fun getParamTypeErrorSeverityCached(uniqueParameterType: UniqueParameterType, param: String): UniqueType.UniqueParameterErrorSeverity? {
         if (!paramTypeErrorSeverityCache.containsKey(uniqueParameterType))
             paramTypeErrorSeverityCache[uniqueParameterType] = hashMapOf()
-        val uniqueParamCache = paramTypeErrorSeverityCache[uniqueParameterType]!!
+        @LocalState val uniqueParamCache = paramTypeErrorSeverityCache[uniqueParameterType]!!
 
         if (uniqueParamCache.containsKey(param)) return uniqueParamCache[param]
 
@@ -376,6 +382,7 @@ class UniqueValidator(val ruleset: Ruleset) {
         return severity
     }
 
+    @Readonly
     private fun checkUntypedUnique(
         unique: Unique,
         tryFixUnknownUniques: Boolean,
@@ -405,6 +412,7 @@ class UniqueValidator(val ruleset: Ruleset) {
         )
     }
 
+    @Readonly
     private fun isFilteringUniqueAllowed(unique: Unique, reportRulesetSpecificErrors: Boolean): Boolean {
         // Isolate this decision, to allow easy change of approach
         // This says: Must have no conditionals or parameters, and is used in any "filtering" parameter of another Unique
@@ -413,6 +421,7 @@ class UniqueValidator(val ruleset: Ruleset) {
         return unique.text in allUniqueParameters // referenced at least once from elsewhere
     }
 
+    @Readonly
     private fun tryFixUnknownUnique(unique: Unique, uniqueContainer: IHasUniques?, prefix: String): RulesetErrorList {
         val similarUniques = UniqueType.entries.filter {
             getRelativeTextDistance(
@@ -450,6 +459,7 @@ class UniqueValidator(val ruleset: Ruleset) {
     companion object {
         const val whichDoesNotFitParameterType = "which does not fit parameter type"
 
+        @Readonly
         internal fun getUniqueContainerPrefix(uniqueContainer: IHasUniques?) =
             (if (uniqueContainer is IRulesetObject) "${uniqueContainer.originRuleset}: " else "") +
                 (if (uniqueContainer == null) "The" else "(${uniqueContainer.getUniqueTarget().name}) ${uniqueContainer.name}'s") +