diff --git a/gradle/libs.versions.toml b/gradle/libs.versions.toml
index a6dc0681..82483277 100644
--- a/gradle/libs.versions.toml
+++ b/gradle/libs.versions.toml
@@ -15,6 +15,7 @@ ax_lifecycle = "2.5.1"
 ax_testing = "2.1.0"
 ax_runner = "1.5.0"
 robolectric = "4.9"
+immutable_collections = "0.3.5"
 
 [plugins]
 multiplatform = { id = "org.jetbrains.kotlin.multiplatform", version.ref = "kotlin" }
@@ -26,6 +27,7 @@ ksp = { id = "com.google.devtools.ksp", version.ref = "ksp" }
 [libraries]
 coroutines-core = { module = "org.jetbrains.kotlinx:kotlinx-coroutines-core", version.ref = "coroutines" }
 coroutines-test = { module = "org.jetbrains.kotlinx:kotlinx-coroutines-test", version.ref = "coroutines" }
+immutableCollections = { module = "org.jetbrains.kotlinx:kotlinx-collections-immutable", version.ref = "immutable_collections" }
 atomicfu = { module = "org.jetbrains.kotlinx:atomicfu", version.ref = "atomicfu" }
 atomicfu-plugin = { module = "org.jetbrains.kotlinx:atomicfu-gradle-plugin", version.ref = "atomicfu" }
 agp = { module = "com.android.tools.build:gradle", version.ref = "agp" }
diff --git a/mobiuskt-core/build.gradle.kts b/mobiuskt-core/build.gradle.kts
index 45070e8b..55d2c801 100644
--- a/mobiuskt-core/build.gradle.kts
+++ b/mobiuskt-core/build.gradle.kts
@@ -91,6 +91,7 @@ kotlin {
         val commonMain by getting {
             dependencies {
                 implementation(libs.atomicfu)
+                implementation(libs.immutableCollections)
             }
         }
 
diff --git a/mobiuskt-core/src/commonMain/kotlin/Effects.kt b/mobiuskt-core/src/commonMain/kotlin/Effects.kt
index 533ba3c0..f4406d09 100644
--- a/mobiuskt-core/src/commonMain/kotlin/Effects.kt
+++ b/mobiuskt-core/src/commonMain/kotlin/Effects.kt
@@ -1,5 +1,6 @@
 package kt.mobius
 
+import kotlinx.collections.immutable.persistentHashSetOf
 import kotlin.js.JsExport
 import kotlin.js.JsName
 import kotlin.jvm.JvmStatic
@@ -21,6 +22,6 @@ public object Effects {
     @JvmStatic
     @JsName("effects")
     public fun <F, G : F> effects(vararg effects: G): Set<F> {
-        return hashSetOf<F>(*effects.copyOf())
+        return persistentHashSetOf<F>(*effects)
     }
 }
diff --git a/mobiuskt-core/src/commonMain/kotlin/First.kt b/mobiuskt-core/src/commonMain/kotlin/First.kt
index 75db8367..45219d5f 100644
--- a/mobiuskt-core/src/commonMain/kotlin/First.kt
+++ b/mobiuskt-core/src/commonMain/kotlin/First.kt
@@ -1,5 +1,6 @@
 package kt.mobius
 
+import kotlinx.collections.immutable.persistentSetOf
 import kotlin.js.JsExport
 import kotlin.js.JsName
 import kotlin.jvm.JvmOverloads
@@ -58,7 +59,7 @@ public data class First<M, F> internal constructor(
          */
         @JvmStatic
         public fun <M, F> first(model: M, vararg effects: F): First<M, F> {
-            return First(model, effects.toSet())
+            return First(model, persistentSetOf(*effects))
         }
     }
 }
diff --git a/mobiuskt-core/src/commonMain/kotlin/Next.kt b/mobiuskt-core/src/commonMain/kotlin/Next.kt
index 48214036..48dcbd5b 100644
--- a/mobiuskt-core/src/commonMain/kotlin/Next.kt
+++ b/mobiuskt-core/src/commonMain/kotlin/Next.kt
@@ -1,5 +1,7 @@
 package kt.mobius
 
+import kotlinx.collections.immutable.persistentSetOf
+import kotlinx.collections.immutable.toImmutableSet
 import kt.mobius.functions.Consumer
 import kotlin.js.JsExport
 import kotlin.js.JsName
@@ -92,33 +94,33 @@ public class Next<M, F> internal constructor(
         @JvmOverloads
         @JsName("nextWithSet")
         public fun <M, F> next(model: M, effects: Set<F> = emptySet()): Next<M, F> {
-            return Next(model, effects.toSet())
+            return Next(model, effects.toImmutableSet())
         }
 
         /** Create a Next that updates the model and dispatches the optional effects. */
         @JvmStatic
         @JsName("next")
         public fun <M, F> next(model: M, vararg effects: F): Next<M, F> {
-            return Next(model, effects.toSet())
+            return Next(model, persistentSetOf(*effects))
         }
 
         /** Create a Next that doesn't update the model but dispatches the supplied effects. */
         @JvmStatic
         @JsName("dispatchWithSet")
         public fun <M, F> dispatch(effects: Set<F>): Next<M, F> {
-            return Next(null, effects)
+            return Next(null, effects.toImmutableSet())
         }
 
         /** Create a Next that doesn't update the model but dispatches the supplied effects. */
         @JvmStatic
         public fun <M, F> dispatch(vararg effects: F): Next<M, F> {
-            return Next(null, effects.toSet())
+            return Next(null, persistentSetOf(*effects))
         }
 
         /** Create an empty Next that doesn't update the model or dispatch effects. */
         @JvmStatic
         public fun <M, F> noChange(): Next<M, F> {
-            return Next(null, emptySet())
+            return Next(null, persistentSetOf())
         }
     }
 }
diff --git a/mobiuskt-coroutines/build.gradle.kts b/mobiuskt-coroutines/build.gradle.kts
index 3f54f079..99ccf6b7 100644
--- a/mobiuskt-coroutines/build.gradle.kts
+++ b/mobiuskt-coroutines/build.gradle.kts
@@ -62,6 +62,7 @@ kotlin {
                 implementation(projects.mobiusktCore)
                 implementation(libs.coroutines.core)
                 implementation(libs.atomicfu)
+                implementation(libs.immutableCollections)
             }
         }
 
diff --git a/mobiuskt-coroutines/src/commonMain/kotlin/SubtypeEffectHandler.kt b/mobiuskt-coroutines/src/commonMain/kotlin/SubtypeEffectHandler.kt
index e045a240..38de96ed 100644
--- a/mobiuskt-coroutines/src/commonMain/kotlin/SubtypeEffectHandler.kt
+++ b/mobiuskt-coroutines/src/commonMain/kotlin/SubtypeEffectHandler.kt
@@ -1,5 +1,7 @@
 package kt.mobius.flow
 
+import kotlinx.collections.immutable.toImmutableList
+import kotlinx.collections.immutable.toImmutableSet
 import kotlinx.coroutines.ExperimentalCoroutinesApi
 import kotlinx.coroutines.flow.*
 import kotlinx.coroutines.flow.transform
@@ -103,7 +105,7 @@ public class SubtypeEffectHandlerBuilder<F : Any, E> {
 
     public fun build(): FlowTransformer<F, E> =
         MobiusEffectRouter(
-            effectClasses = effectPerformerMap.keys.toSet(),
-            effectPerformers = effectPerformerMap.values.toList()
+            effectClasses = effectPerformerMap.keys.toImmutableSet(),
+            effectPerformers = effectPerformerMap.values.toImmutableList()
         )
 }
diff --git a/mobiuskt-extras/build.gradle.kts b/mobiuskt-extras/build.gradle.kts
index 36e881a7..75c9ecd6 100644
--- a/mobiuskt-extras/build.gradle.kts
+++ b/mobiuskt-extras/build.gradle.kts
@@ -42,6 +42,7 @@ kotlin {
             dependencies {
                 implementation(projects.mobiusktCore)
                 implementation(libs.atomicfu)
+                implementation(libs.immutableCollections)
             }
         }
 
diff --git a/mobiuskt-extras/src/commonMain/kotlin/CompositeLogger.kt b/mobiuskt-extras/src/commonMain/kotlin/CompositeLogger.kt
index 6b74339c..3439320a 100644
--- a/mobiuskt-extras/src/commonMain/kotlin/CompositeLogger.kt
+++ b/mobiuskt-extras/src/commonMain/kotlin/CompositeLogger.kt
@@ -1,5 +1,6 @@
 package kt.mobius.extras
 
+import kotlinx.collections.immutable.persistentListOf
 import kt.mobius.First
 import kt.mobius.MobiusLoop.Logger
 import kt.mobius.Next
@@ -51,7 +52,7 @@ public class CompositeLogger<M, E, F> private constructor(
         @JvmStatic
         @JsName("from")
         public fun <M, E, F> from(vararg loggers: Logger<M, E, F>): Logger<M, E, F> {
-            return CompositeLogger(loggers.toList())
+            return CompositeLogger(persistentListOf(*loggers))
         }
     }
 }
diff --git a/mobiuskt-extras/src/commonMain/kotlin/patterns/InnerUpdate.kt b/mobiuskt-extras/src/commonMain/kotlin/patterns/InnerUpdate.kt
index e9964bdf..8875d2cf 100644
--- a/mobiuskt-extras/src/commonMain/kotlin/patterns/InnerUpdate.kt
+++ b/mobiuskt-extras/src/commonMain/kotlin/patterns/InnerUpdate.kt
@@ -1,5 +1,6 @@
 package kt.mobius.extras.patterns
 
+import kotlinx.collections.immutable.toImmutableSet
 import kt.mobius.Next
 import kt.mobius.Next.Companion.dispatch
 import kt.mobius.Next.Companion.next
@@ -168,7 +169,7 @@ public object InnerEffectHandlers {
                 if (modelUpdated) next(model)
                 else noChange()
             } else {
-                val effects = innerEffects.map(f::apply).toSet()
+                val effects = innerEffects.map(f::apply).toImmutableSet()
                 if (modelUpdated) next(model, effects)
                 else dispatch(effects)
             }
diff --git a/mobiuskt-test/build.gradle.kts b/mobiuskt-test/build.gradle.kts
index f50b2b0a..032e3518 100644
--- a/mobiuskt-test/build.gradle.kts
+++ b/mobiuskt-test/build.gradle.kts
@@ -40,6 +40,7 @@ kotlin {
             dependencies {
                 implementation(projects.mobiusktCore)
                 implementation(libs.atomicfu)
+                implementation(libs.immutableCollections)
                 implementation(kotlin("test-common"))
                 implementation(kotlin("test-annotations-common"))
             }
diff --git a/mobiuskt-test/src/commonMain/kotlin/UpdateSpec.kt b/mobiuskt-test/src/commonMain/kotlin/UpdateSpec.kt
index 1a22c5d4..317f4a25 100644
--- a/mobiuskt-test/src/commonMain/kotlin/UpdateSpec.kt
+++ b/mobiuskt-test/src/commonMain/kotlin/UpdateSpec.kt
@@ -1,5 +1,6 @@
 package kt.mobius.test
 
+import kotlinx.collections.immutable.persistentListOf
 import kt.mobius.Next
 import kt.mobius.Update
 import kt.mobius.test.matcher.Matcher
@@ -107,7 +108,7 @@ public class UpdateSpec<M, E, F>(
         init {
             this.events = ArrayList(events.size + 1)
             this.events.add(event)
-            this.events.addAll(events.toList())
+            this.events.addAll(persistentListOf(*events))
         }
 
         override fun then(assertion: Assert<M, F>) {