Merge pull request #262 from m1sk9/refactor/config-and-module-boundaries

refactor: put config, protocol and module boundaries where they belong

42 files changed, 584 insertions, 426 deletions

diff --git a/engine/build.gradle.kts b/engine/build.gradle.kts
index bcb7eb6..5782890 100644
--- a/engine/build.gradle.kts
+++ b/engine/build.gradle.kts
@@ -4,15 +4,7 @@ plugins {
 }
 
 dependencies {
-    // Core dependencies (exposed to platform modules via api())
+    // Exposed to platform modules via api(): the plugin messaging protocol is built on it, so
+    // both platforms need it on their compile and runtime classpath.
     api("org.jetbrains.kotlinx:kotlinx-serialization-json:1.11.0")
-    api("org.jetbrains.kotlinx:kotlinx-coroutines-core:1.11.0")
-    api("io.ktor:ktor-client-core:3.5.2")
-    api("io.ktor:ktor-client-cio:3.5.2")
-
-    // Adventure API (provided by platform implementations)
-    // Matches what every supported platform ships: Paper 26.2 and Velocity 4.x both bundle 5.2.0.
-    compileOnly("net.kyori:adventure-api:5.2.0")
-
-    testImplementation("net.kyori:adventure-api:5.2.0")
 }
diff --git a/engine/src/main/kotlin/dev/m1sk9/lunaticChat/engine/command/CommandResult.kt b/engine/src/main/kotlin/dev/m1sk9/lunaticChat/engine/command/CommandResult.kt
index 9c9d882..c9d7771 100644
--- a/engine/src/main/kotlin/dev/m1sk9/lunaticChat/engine/command/CommandResult.kt
+++ b/engine/src/main/kotlin/dev/m1sk9/lunaticChat/engine/command/CommandResult.kt
@@ -1,10 +1,11 @@
 package dev.m1sk9.lunaticChat.engine.command
 
-import net.kyori.adventure.text.Component
-
 /**
  * Represents the result of a command execution.
  * Uses Kotlin sealed classes for type-safe result handling.
+ *
+ * Messages travel as plain text; turning them into styled output is the platform's job, so this
+ * stays free of any Minecraft or Adventure type.
  */
 sealed class CommandResult {
     /** Command executed successfully */
@@ -12,12 +13,12 @@ sealed class CommandResult {
 
     /** Command executed successfully with a message to display */
     data class SuccessWithMessage(
-        val message: Component,
+        val message: String,
     ) : CommandResult()
 
     /** Command failed with an error message */
     data class Failure(
-        val message: Component,
+        val message: String,
     ) : CommandResult()
 
     /** Command failed due to invalid usage */
diff --git a/engine/src/main/kotlin/dev/m1sk9/lunaticChat/engine/protocol/PluginMessage.kt b/engine/src/main/kotlin/dev/m1sk9/lunaticChat/engine/protocol/PluginMessage.kt
index 1ba5c25..689a57c 100644
--- a/engine/src/main/kotlin/dev/m1sk9/lunaticChat/engine/protocol/PluginMessage.kt
+++ b/engine/src/main/kotlin/dev/m1sk9/lunaticChat/engine/protocol/PluginMessage.kt
@@ -113,7 +113,9 @@ sealed interface PluginMessage {
      * @property senderId Sender UUID as string (used to locate the sender to notify)
      * @property targetName Target player name that was requested
      * @property targetServerName Target server name that was requested
-     * @property reason Failure reason: [Reason.TARGET_OFFLINE] or [Reason.SERVER_NOT_FOUND]
+     * @property reason Why delivery failed. Defaults to [Reason.TARGET_OFFLINE] so that a reason
+     *   added by a newer peer degrades to the generic failure rather than failing to decode -
+     *   [PluginMessageCodec] enables coerceInputValues for exactly this.
      */
     @Serializable
     data class DirectMessageError(
@@ -121,11 +123,18 @@ sealed interface PluginMessage {
         val senderId: String,
         val targetName: String,
         val targetServerName: String,
-        val reason: String,
+        val reason: Reason = Reason.TARGET_OFFLINE,
     ) : PluginMessage {
-        object Reason {
-            const val TARGET_OFFLINE = "TARGET_OFFLINE"
-            const val SERVER_NOT_FOUND = "SERVER_NOT_FOUND"
+        /**
+         * Why a cross-server direct message could not be delivered.
+         *
+         * An enum rather than string constants so that adding a case forces every reader to
+         * decide what to show for it, instead of silently reporting the existing default.
+         */
+        @Serializable
+        enum class Reason {
+            TARGET_OFFLINE,
+            SERVER_NOT_FOUND,
         }
     }
 
diff --git a/engine/src/main/kotlin/dev/m1sk9/lunaticChat/engine/protocol/PluginMessageCodec.kt b/engine/src/main/kotlin/dev/m1sk9/lunaticChat/engine/protocol/PluginMessageCodec.kt
index 14d1f82..f3b52c6 100644
--- a/engine/src/main/kotlin/dev/m1sk9/lunaticChat/engine/protocol/PluginMessageCodec.kt
+++ b/engine/src/main/kotlin/dev/m1sk9/lunaticChat/engine/protocol/PluginMessageCodec.kt
@@ -13,7 +13,13 @@ import java.io.DataOutputStream
  * Format: [subChannel: UTF][messageJson: UTF]
  */
 object PluginMessageCodec {
-    private val json = Json { ignoreUnknownKeys = true }
+    private val json =
+        Json {
+            ignoreUnknownKeys = true
+            // An enum value this build does not know falls back to the property's default rather
+            // than failing the whole message, matching how unknown fields are treated.
+            coerceInputValues = true
+        }
 
     /**
      * Sub-channel names
diff --git a/engine/src/test/kotlin/dev/m1sk9/lunaticChat/engine/command/CommandResultTest.kt b/engine/src/test/kotlin/dev/m1sk9/lunaticChat/engine/command/CommandResultTest.kt
index b80f116..a9033d0 100644
--- a/engine/src/test/kotlin/dev/m1sk9/lunaticChat/engine/command/CommandResultTest.kt
+++ b/engine/src/test/kotlin/dev/m1sk9/lunaticChat/engine/command/CommandResultTest.kt
@@ -1,6 +1,5 @@
 package dev.m1sk9.lunaticChat.engine.command
 
-import net.kyori.adventure.text.Component
 import kotlin.test.Test
 import kotlin.test.assertEquals
 import kotlin.test.assertIs
@@ -13,13 +12,13 @@ class CommandResultTest {
 
     @Test
     fun `SuccessWithMessage toBrigadierResult should return 1`() {
-        val result = CommandResult.SuccessWithMessage(Component.text("ok"))
+        val result = CommandResult.SuccessWithMessage("ok")
         assertEquals(1, result.toBrigadierResult())
     }
 
     @Test
     fun `Failure toBrigadierResult should return 0`() {
-        val result = CommandResult.Failure(Component.text("error"))
+        val result = CommandResult.Failure("error")
         assertEquals(0, result.toBrigadierResult())
     }
 
@@ -31,7 +30,7 @@ class CommandResultTest {
 
     @Test
     fun `SuccessWithMessage should preserve message`() {
-        val message = Component.text("Test message")
+        val message = "Test message"
         val result = CommandResult.SuccessWithMessage(message)
         assertIs<CommandResult.SuccessWithMessage>(result)
         assertEquals(message, result.message)
@@ -39,7 +38,7 @@ class CommandResultTest {
 
     @Test
     fun `Failure should preserve message`() {
-        val message = Component.text("Error message")
+        val message = "Error message"
         val result = CommandResult.Failure(message)
         assertIs<CommandResult.Failure>(result)
         assertEquals(message, result.message)
diff --git a/engine/src/test/kotlin/dev/m1sk9/lunaticChat/engine/protocol/PluginMessageCodecTest.kt b/engine/src/test/kotlin/dev/m1sk9/lunaticChat/engine/protocol/PluginMessageCodecTest.kt
index 0eb56c1..e1c65ba 100644
--- a/engine/src/test/kotlin/dev/m1sk9/lunaticChat/engine/protocol/PluginMessageCodecTest.kt
+++ b/engine/src/test/kotlin/dev/m1sk9/lunaticChat/engine/protocol/PluginMessageCodecTest.kt
@@ -291,7 +291,7 @@ class PluginMessageCodecTest {
                 PluginMessage.StatusResponse("1.0.0", "1.0.0", true),
                 PluginMessage.GlobalChatMessage("id", "srv", "pid", "name", "msg", 0L),
                 PluginMessage.DirectMessageRelay("id", "src", "sid", "sname", "tsrv", "tname", "msg", 0L),
-                PluginMessage.DirectMessageError("id", "sid", "tname", "tsrv", "TARGET_OFFLINE"),
+                PluginMessage.DirectMessageError("id", "sid", "tname", "tsrv", PluginMessage.DirectMessageError.Reason.TARGET_OFFLINE),
                 PluginMessage.PresenceSnapshot(listOf(PresenceEntry("p", "s")), 0L),
                 PluginMessage.PresenceRequest,
             )
diff --git a/engine/src/test/kotlin/dev/m1sk9/lunaticChat/engine/protocol/ProtocolBackwardCompatibilityTest.kt b/engine/src/test/kotlin/dev/m1sk9/lunaticChat/engine/protocol/ProtocolBackwardCompatibilityTest.kt
index c9bc6c0..e70edda 100644
--- a/engine/src/test/kotlin/dev/m1sk9/lunaticChat/engine/protocol/ProtocolBackwardCompatibilityTest.kt
+++ b/engine/src/test/kotlin/dev/m1sk9/lunaticChat/engine/protocol/ProtocolBackwardCompatibilityTest.kt
@@ -174,7 +174,7 @@ class ProtocolBackwardCompatibilityTest {
         assertEquals("00000005-0000-0000-0000-000000000000", decoded.senderId)
         assertEquals("Ghost", decoded.targetName)
         assertEquals("lobby", decoded.targetServerName)
-        assertEquals("TARGET_OFFLINE", decoded.reason)
+        assertEquals(PluginMessage.DirectMessageError.Reason.TARGET_OFFLINE, decoded.reason)
     }
 
     @Test
@@ -196,4 +196,18 @@ class ProtocolBackwardCompatibilityTest {
 
         assertIs<PluginMessage.PresenceRequest>(decoded)
     }
+
+    @Test
+    fun `a failure reason this build does not know decodes to the generic failure`() {
+        val fromNewerPeer =
+            """{"messageId":"dm-789","senderId":"00000006-0000-0000-0000-000000000000",""" +
+                """"targetName":"Ghost","targetServerName":"lobby","reason":"RATE_LIMITED"}"""
+
+        val decoded = PluginMessageCodec.decode(buildRawMessage("direct_message_error", fromNewerPeer))
+
+        // A proxy that learns a new reason must not make this build drop the whole message.
+        assertIs<PluginMessage.DirectMessageError>(decoded)
+        assertEquals("dm-789", decoded.messageId)
+        assertEquals(PluginMessage.DirectMessageError.Reason.TARGET_OFFLINE, decoded.reason)
+    }
 }
diff --git a/engine/src/test/kotlin/dev/m1sk9/lunaticChat/engine/settings/SettingsDataClassesTest.kt b/engine/src/test/kotlin/dev/m1sk9/lunaticChat/engine/settings/SettingsDataClassesTest.kt
index a7cc2ee..bd337ff 100644
--- a/engine/src/test/kotlin/dev/m1sk9/lunaticChat/engine/settings/SettingsDataClassesTest.kt
+++ b/engine/src/test/kotlin/dev/m1sk9/lunaticChat/engine/settings/SettingsDataClassesTest.kt
@@ -1,6 +1,5 @@
 package dev.m1sk9.lunaticChat.engine.settings
 
-import dev.m1sk9.lunaticChat.engine.converter.CacheData
 import kotlinx.serialization.json.Json
 import java.util.UUID
 import kotlin.test.Test
@@ -104,28 +103,4 @@ class SettingsDataClassesTest {
         val serialized = json.encodeToString(PlayerSettingsData.serializer(), data)
         assertTrue(serialized.contains(testUUID.toString()))
     }
-
-    // --- CacheData ---
-
-    @Test
-    fun `CacheData should store version and entries`() {
-        val data = CacheData(version = "1.0", entries = mapOf("hello" to "こんにちは"))
-        assertEquals("1.0", data.version)
-        assertEquals("こんにちは", data.entries["hello"])
-    }
-
-    @Test
-    fun `CacheData serialization round-trip should preserve all fields`() {
-        val original =
-            CacheData(
-                version = "2.0",
-                entries = mapOf("hello" to "こんにちは", "world" to "世界"),
-            )
-
-        val serialized = json.encodeToString(CacheData.serializer(), original)
-        val deserialized = json.decodeFromString(CacheData.serializer(), serialized)
-
-        assertEquals(original.version, deserialized.version)
-        assertEquals(original.entries, deserialized.entries)
-    }
 }
diff --git a/platform-paper/build.gradle.kts b/platform-paper/build.gradle.kts
index a846ed9..5c2db6f 100644
--- a/platform-paper/build.gradle.kts
+++ b/platform-paper/build.gradle.kts
@@ -15,11 +15,14 @@ repositories {
 }
 
 dependencies {
-    // Engine module (provides serialization, coroutines, ktor)
+    // Engine module (provides serialization)
     api(project(":engine"))
 
     // Paper-specific dependencies
     compileOnly("io.papermc.paper:paper-api:26.2.build.92-stable")
+    implementation("org.jetbrains.kotlinx:kotlinx-coroutines-core:1.11.0")
+    implementation("io.ktor:ktor-client-core:3.5.2") // Google IME client, update check
+    implementation("io.ktor:ktor-client-cio:3.5.2")
     implementation("com.charleskorn.kaml:kaml:0.104.0") // YAML configuration
     implementation("org.jetbrains.kotlin:kotlin-reflect:2.4.10") // Annotation processing
 
diff --git a/platform-paper/src/main/kotlin/dev/m1sk9/lunaticChat/paper/LunaticChat.kt b/platform-paper/src/main/kotlin/dev/m1sk9/lunaticChat/paper/LunaticChat.kt
index f39e5d4..3f9cb76 100644
--- a/platform-paper/src/main/kotlin/dev/m1sk9/lunaticChat/paper/LunaticChat.kt
+++ b/platform-paper/src/main/kotlin/dev/m1sk9/lunaticChat/paper/LunaticChat.kt
@@ -58,8 +58,7 @@ class LunaticChat :
 
     override fun onEnable() {
         saveDefaultConfig()
-        val configManager = ConfigManager()
-        configuration = configManager.loadConfiguration(config)
+        configuration = ConfigManager(logger).loadConfiguration(readConfigFile())
 
         if (configuration.debug) {
             logger.warning("LunaticChat is running in debug mode.")
@@ -103,6 +102,21 @@ class LunaticChat :
     }
 
     /**
+     * Reads config.yml, or an empty document when it cannot be read.
+     *
+     * [saveDefaultConfig] only logs when it fails to write the file, so the read can still find
+     * nothing there. Handing the parser an empty document starts the plugin on its defaults
+     * instead of throwing out of [onEnable] and disabling it outright.
+     */
+    private fun readConfigFile(): String {
+        val file = dataFolder.resolve("config.yml")
+        return runCatching { file.readText() }.getOrElse { e ->
+            logger.severe("Could not read ${file.path}, falling back to defaults: ${e.message}")
+            ""
+        }
+    }
+
+    /**
      * Registers all commands based on enabled features.
      */
     private fun registerCommands() {
diff --git a/platform-paper/src/main/kotlin/dev/m1sk9/lunaticChat/paper/ServiceInitializer.kt b/platform-paper/src/main/kotlin/dev/m1sk9/lunaticChat/paper/ServiceInitializer.kt
index 5ec2e0a..bbfaab2 100644
--- a/platform-paper/src/main/kotlin/dev/m1sk9/lunaticChat/paper/ServiceInitializer.kt
+++ b/platform-paper/src/main/kotlin/dev/m1sk9/lunaticChat/paper/ServiceInitializer.kt
@@ -1,6 +1,5 @@
 package dev.m1sk9.lunaticChat.paper
 
-import dev.m1sk9.lunaticChat.engine.converter.GoogleIMEClient
 import dev.m1sk9.lunaticChat.paper.chat.channel.ChannelManager
 import dev.m1sk9.lunaticChat.paper.chat.channel.ChannelMembershipManager
 import dev.m1sk9.lunaticChat.paper.chat.channel.ChannelMessageLogger
@@ -10,6 +9,7 @@ import dev.m1sk9.lunaticChat.paper.chat.handler.ChannelNotificationHandler
 import dev.m1sk9.lunaticChat.paper.chat.handler.DirectMessageHandler
 import dev.m1sk9.lunaticChat.paper.config.LunaticChatConfiguration
 import dev.m1sk9.lunaticChat.paper.converter.ConversionCache
+import dev.m1sk9.lunaticChat.paper.converter.GoogleIMEClient
 import dev.m1sk9.lunaticChat.paper.converter.RomanjiConverter
 import dev.m1sk9.lunaticChat.paper.i18n.LanguageManager
 import dev.m1sk9.lunaticChat.paper.settings.PlayerSettingsManager
@@ -190,8 +190,8 @@ class ServiceInitializer(
         // Initialize conversion cache
         val cache =
             ConversionCache(
-                cacheFile = plugin.dataFolder.resolve(configuration.features.japaneseConversion.cacheFilePath).toPath(),
-                maxEntries = configuration.features.japaneseConversion.cacheMaxEntries,
+                cacheFile = plugin.dataFolder.resolve(configuration.features.japaneseConversion.cache.filePath).toPath(),
+                maxEntries = configuration.features.japaneseConversion.cache.maxEntries,
                 logger = logger,
             )
         cache.loadFromDisk()
@@ -199,7 +199,7 @@ class ServiceInitializer(
         // Initialize Google IME API client
         val apiClient =
             GoogleIMEClient(
-                timeout = configuration.features.japaneseConversion.apiTimeout.milliseconds,
+                timeout = configuration.features.japaneseConversion.api.timeout.milliseconds,
                 httpClient = httpClient.value,
             )
 
@@ -428,7 +428,7 @@ class ServiceInitializer(
             // would both be rejected by runAtFixedRate and leave the cache unsaved until the
             // server stopped. Fall back to the documented default rather than to one second,
             // which would rewrite the whole cache file every tick anyone chatted.
-            val configuredInterval = configuration.features.japaneseConversion.cacheSaveIntervalSeconds
+            val configuredInterval = configuration.features.japaneseConversion.cache.saveIntervalSeconds
             val intervalSeconds =
                 if (configuredInterval > 0) {
                     configuredInterval.toLong()
diff --git a/platform-paper/src/main/kotlin/dev/m1sk9/lunaticChat/paper/command/core/LunaticCommandBase.kt b/platform-paper/src/main/kotlin/dev/m1sk9/lunaticChat/paper/command/core/LunaticCommandBase.kt
index 89b9acc..8cfedc7 100644
--- a/platform-paper/src/main/kotlin/dev/m1sk9/lunaticChat/paper/command/core/LunaticCommandBase.kt
+++ b/platform-paper/src/main/kotlin/dev/m1sk9/lunaticChat/paper/command/core/LunaticCommandBase.kt
@@ -33,7 +33,7 @@ abstract class LunaticCommandBase(
     protected fun fail(
         key: String,
         args: Map<String, String> = emptyMap(),
-    ): CommandResult = CommandResult.Failure(MessageFormatter.formatError(languageManager.getMessage(key, args)))
+    ): CommandResult = CommandResult.Failure(languageManager.getMessage(key, args))
 
     /**
      * A successful result carrying the localized message at [key].
@@ -41,7 +41,7 @@ abstract class LunaticCommandBase(
     protected fun ok(
         key: String,
         args: Map<String, String> = emptyMap(),
-    ): CommandResult = CommandResult.SuccessWithMessage(MessageFormatter.format(languageManager.getMessage(key, args)))
+    ): CommandResult = CommandResult.SuccessWithMessage(languageManager.getMessage(key, args))
 
     /**
      * Helper method for checking player-only restriction.
@@ -70,8 +70,8 @@ abstract class LunaticCommandBase(
     ): Int {
         when (result) {
             is CommandResult.Success -> {}
-            is CommandResult.SuccessWithMessage -> ctx.reply(result.message)
-            is CommandResult.Failure -> ctx.reply(result.message)
+            is CommandResult.SuccessWithMessage -> ctx.reply(MessageFormatter.format(result.message))
+            is CommandResult.Failure -> ctx.reply(MessageFormatter.formatError(result.message))
             is CommandResult.InvalidUsage ->
                 ctx.reply(
                     Component
diff --git a/platform-paper/src/main/kotlin/dev/m1sk9/lunaticChat/paper/command/impl/lc/channel/ChannelCreateCommand.kt b/platform-paper/src/main/kotlin/dev/m1sk9/lunaticChat/paper/command/impl/lc/channel/ChannelCreateCommand.kt
index d1db42d..ac4c78a 100644
--- a/platform-paper/src/main/kotlin/dev/m1sk9/lunaticChat/paper/command/impl/lc/channel/ChannelCreateCommand.kt
+++ b/platform-paper/src/main/kotlin/dev/m1sk9/lunaticChat/paper/command/impl/lc/channel/ChannelCreateCommand.kt
@@ -13,7 +13,6 @@ import dev.m1sk9.lunaticChat.paper.command.annotation.PlayerOnly
 import dev.m1sk9.lunaticChat.paper.command.core.CommandContext
 import dev.m1sk9.lunaticChat.paper.command.core.LunaticSubCommand
 import dev.m1sk9.lunaticChat.paper.i18n.LanguageManager
-import dev.m1sk9.lunaticChat.paper.i18n.MessageFormatter
 import io.papermc.paper.command.brigadier.CommandSourceStack
 import io.papermc.paper.command.brigadier.Commands
 
@@ -121,9 +120,7 @@ class ChannelCreateCommand(
                         successMessage
                     }
 
-                CommandResult.SuccessWithMessage(
-                    MessageFormatter.format(message),
-                )
+                CommandResult.SuccessWithMessage(message)
             },
             onFailure = { error ->
                 when (error) {
diff --git a/platform-paper/src/main/kotlin/dev/m1sk9/lunaticChat/paper/config/ConfigManager.kt b/platform-paper/src/main/kotlin/dev/m1sk9/lunaticChat/paper/config/ConfigManager.kt
index 37764bf..2ce24b6 100644
--- a/platform-paper/src/main/kotlin/dev/m1sk9/lunaticChat/paper/config/ConfigManager.kt
+++ b/platform-paper/src/main/kotlin/dev/m1sk9/lunaticChat/paper/config/ConfigManager.kt
@@ -1,113 +1,104 @@
 package dev.m1sk9.lunaticChat.paper.config
 
-import dev.m1sk9.lunaticChat.paper.config.key.ChannelChatFeatureConfig
-import dev.m1sk9.lunaticChat.paper.config.key.FeaturesConfig
-import dev.m1sk9.lunaticChat.paper.config.key.JapaneseConversionFeatureConfig
-import dev.m1sk9.lunaticChat.paper.config.key.MessageFormatConfig
-import dev.m1sk9.lunaticChat.paper.config.key.QuickRepliesFeatureConfig
-import dev.m1sk9.lunaticChat.paper.config.key.VelocityIntegrationConfig
-import dev.m1sk9.lunaticChat.paper.i18n.Language
-import org.bukkit.configuration.file.FileConfiguration
+import com.charleskorn.kaml.EmptyYamlDocumentException
+import com.charleskorn.kaml.Yaml
+import com.charleskorn.kaml.YamlConfiguration
+import com.charleskorn.kaml.YamlException
+import com.charleskorn.kaml.YamlMap
+import com.charleskorn.kaml.YamlNode
+import com.charleskorn.kaml.YamlPath
+import com.charleskorn.kaml.YamlPathSegment
+import java.util.logging.Level
+import java.util.logging.Logger
 
 /**
- * Manages loading and parsing of plugin configuration.
- * Converted from singleton to dependency injection pattern for better testability.
+ * Reads config.yml into [LunaticChatConfiguration].
+ *
+ * The file is deserialized directly rather than copied key by key, so a default lives only on the
+ * data class. The hand-written mapper it replaced repeated every default in a second place, and
+ * they had already drifted - checkForUpdates disagreed with both config.yml and the data class,
+ * and the whole messageLogging block was documented but never read.
  */
-class ConfigManager {
-    fun loadConfiguration(configFile: FileConfiguration): LunaticChatConfiguration {
-        val loadedConfig =
-            LunaticChatConfiguration(
-                features =
-                    FeaturesConfig(
-                        quickReplies =
-                            QuickRepliesFeatureConfig(
-                                enabled =
-                                    configFile.getBoolean("features.quickReplies.enabled", true),
-                            ),
-                        japaneseConversion =
-                            JapaneseConversionFeatureConfig(
-                                enabled = configFile.getBoolean("features.japaneseConversion.enabled", false),
-                                cacheMaxEntries = configFile.getInt("features.japaneseConversion.cache.maxEntries", 500),
-                                cacheSaveIntervalSeconds =
-                                    configFile.getInt(
-                                        "features.japaneseConversion.cache.saveIntervalSeconds",
-                                        300,
-                                    ),
-                                cacheFilePath =
-                                    configFile.getString(
-                                        "features.japaneseConversion.cache.filePath",
-                                        "conversion_cache.json",
-                                    )!!,
-                                apiTimeout =
-                                    configFile.getLong(
-                                        "features.japaneseConversion.api.timeout",
-                                        3000,
-                                    ),
-                                apiRetryAttempts = configFile.getInt("features.japaneseConversion.api.retryAttempts", 2),
-                            ),
-                        channelChat =
-                            ChannelChatFeatureConfig(
-                                enabled = configFile.getBoolean("features.channelChat.enabled", false),
-                                maxChannelsPerServer = configFile.getInt("features.channelChat.maxChannelsPerServer", 0),
-                                maxMembersPerChannel = configFile.getInt("features.channelChat.maxMembersPerChannel", 0),
-                                maxMembershipPerPlayer = configFile.getInt("features.channelChat.maxMembershipPerPlayer", 0),
-                            ),
-                        velocityIntegration =
-                            VelocityIntegrationConfig(
-                                enabled = configFile.getBoolean("features.velocityIntegration.enabled", false),
-                                crossServerGlobalChat =
-                                    configFile.getBoolean(
-                                        "features.velocityIntegration.crossServerGlobalChat",
-                                        false,
-                                    ),
-                                crossServerDirectMessage =
-                                    configFile.getBoolean(
-                                        "features.velocityIntegration.crossServerDirectMessage",
-                                        false,
-                                    ),
-                                serverName =
-                                    configFile.getString(
-                                        "features.velocityIntegration.serverName",
-                                        "Unknown",
-                                    ) ?: "Unknown",
-                                messageDeduplicationCacheSize =
-                                    configFile.getInt(
-                                        "features.velocityIntegration.messageDeduplicationCacheSize",
-                                        100,
-                                    ),
-                            ),
-                    ),
-                messageFormat =
-                    MessageFormatConfig(
-                        directMessageFormat =
-                            configFile.getString(
-                                "messageFormat.directMessageFormat",
-                                "§7[§e{sender} §7>> §e{recipient}§7] §f{message}",
-                            )!!,
-                        channelMessageFormat =
-                            configFile.getString(
-                                "messageFormat.channelMessageFormat",
-                                "§7[§b#{channel}§7] §e{sender}: §f{message}",
-                            )!!,
-                        crossServerGlobalChatFormat =
-                            configFile.getString(
-                                "messageFormat.crossServerGlobalChatFormat",
-                                "§7[§6{server}§7] §e{sender}: §f{message}",
-                            )!!,
-                    ),
-                debug = configFile.getBoolean("debug", false),
-                checkForUpdates = configFile.getBoolean("checkForUpdates", false),
-                userSettingsFilePath =
-                    configFile.getString(
-                        "userSettingsFilePath",
-                        "player-settings.yaml",
-                    )!!,
-                language =
-                    Language.fromCode(
-                        configFile.getString("language", "en")!!,
-                    ),
-            )
+class ConfigManager(
+    private val logger: Logger,
+) {
+    private val yaml =
+        Yaml(
+            configuration =
+                YamlConfiguration(
+                    // A config.yml from a newer build, or one carrying a key we have retired,
+                    // should not stop the plugin from starting.
+                    strictMode = false,
+                ),
+        )
 
-        return loadedConfig
+    /**
+     * Parses [contents] as config.yml.
+     *
+     * A setting that cannot be read falls back to its default on its own; the rest of the file is
+     * still honoured. Only a document that is not YAML at all costs the operator every setting.
+     */
+    fun loadConfiguration(contents: String): LunaticChatConfiguration {
+        var document =
+            try {
+                // Editors that write a UTF-8 BOM would otherwise leave it on the first key, which
+                // strictMode = false then drops as an unknown setting without a word.
+                yaml.parseToYamlNode(contents.removePrefix("\uFEFF"))
+            } catch (e: EmptyYamlDocumentException) {
+                // A file that only holds comments is a valid way of saying "use the defaults", so it
+                // is not reported as a failure the operator has to act on.
+                return LunaticChatConfiguration()
+            } catch (e: Exception) {
+                // Not YamlException: a file the reader rejects before it is YAML at all - one saved
+                // as UTF-16, or truncated with NUL padding - fails inside the scanner, and letting
+                // that out of onEnable would disable the plugin over a config file.
+                return allDefaults("config.yml is not valid YAML", e)
+            }
+
+        // Each pass drops exactly one setting, so this terminates: the document strictly shrinks
+        // until it decodes or there is nothing left to drop.
+        while (true) {
+            try {
+                return yaml.decodeFromYamlNode(LunaticChatConfiguration.serializer(), document)
+            } catch (e: YamlException) {
+                // kaml rejects the document as a whole, so without this one unreadable value would
+                // lose every other setting in the file - a regression against the hand-written
+                // mapper, which defaulted per key.
+                val setting = e.path.settingKeys()
+                val remaining =
+                    document.without(setting)
+                        ?: return allDefaults("config.yml could not be read", e)
+                logger.warning("${setting.joinToString(".")} in config.yml fell back to its default: ${e.message}")
+                document = remaining
+            } catch (e: Exception) {
+                // A serializer can fail without kaml turning it into a YamlException, and there is
+                // no path to prune a single setting by without one.
+                return allDefaults("config.yml could not be read", e)
+            }
+        }
+    }
+
+    private fun allDefaults(
+        what: String,
+        cause: Exception,
+    ): LunaticChatConfiguration {
+        logger.log(
+            Level.SEVERE,
+            "$what, so EVERY setting fell back to its default (fix the reported value and restart): ${cause.message}",
+            cause,
+        )
+        return LunaticChatConfiguration()
+    }
+
+    /** The config.yml keys leading to the node this path points at, outermost first. */
+    private fun YamlPath.settingKeys(): List<String> = segments.filterIsInstance<YamlPathSegment.MapElementKey>().map { it.key }
+
+    /** A copy of this document without [keys], or null when that entry is not there to remove. */
+    private fun YamlNode.without(keys: List<String>): YamlNode? {
+        if (this !is YamlMap || keys.isEmpty()) return null
+        val key = entries.keys.firstOrNull { it.content == keys.first() } ?: return null
+        if (keys.size == 1) return YamlMap(entries - key, path)
+        val remaining = entries.getValue(key).without(keys.drop(1)) ?: return null
+        return YamlMap(entries + (key to remaining), path)
     }
 }
diff --git a/platform-paper/src/main/kotlin/dev/m1sk9/lunaticChat/paper/config/LenientBoolean.kt b/platform-paper/src/main/kotlin/dev/m1sk9/lunaticChat/paper/config/LenientBoolean.kt
new file mode 100644
index 0000000..3c93fb8
--- /dev/null
+++ b/platform-paper/src/main/kotlin/dev/m1sk9/lunaticChat/paper/config/LenientBoolean.kt
@@ -0,0 +1,53 @@
+package dev.m1sk9.lunaticChat.paper.config
+
+import com.charleskorn.kaml.YamlException
+import com.charleskorn.kaml.YamlInput
+import kotlinx.serialization.KSerializer
+import kotlinx.serialization.Serializable
+import kotlinx.serialization.SerializationException
+import kotlinx.serialization.descriptors.PrimitiveKind
+import kotlinx.serialization.descriptors.PrimitiveSerialDescriptor
+import kotlinx.serialization.encoding.Decoder
+import kotlinx.serialization.encoding.Encoder
+
+/**
+ * A Boolean that also accepts the spellings YAML 1.1 counted as boolean.
+ *
+ * Bukkit read config.yml as YAML 1.1, where `yes`, `no`, `on` and `off` are booleans; kaml reads
+ * YAML 1.2, where they are plain strings. Rejecting them would take a file that has worked for
+ * releases and quietly reset the setting - and for `checkForUpdates: no` the default is the
+ * opposite of what the file says, so the operator would get behaviour they had turned off.
+ */
+typealias LenientBoolean =
+    @Serializable(with = LenientBooleanSerializer::class)
+    Boolean
+
+object LenientBooleanSerializer : KSerializer<Boolean> {
+    private val trueWords = setOf("true", "yes", "on", "y")
+    private val falseWords = setOf("false", "no", "off", "n")
+
+    // STRING rather than BOOLEAN: the point is to read the scalar before YAML 1.2 decides it is not
+    // a boolean at all.
+    override val descriptor = PrimitiveSerialDescriptor("LenientBoolean", PrimitiveKind.STRING)
+
+    override fun deserialize(decoder: Decoder): Boolean {
+        // Captured before decoding: ConfigManager prunes the offending setting by path, and only a
+        // YamlException carries one. A plain SerializationException would escape it and cost the
+        // operator the whole file.
+        val path = (decoder as? YamlInput)?.node?.path
+        val raw = decoder.decodeString()
+        return when (raw.lowercase()) {
+            in trueWords -> true
+            in falseWords -> false
+            else -> {
+                val reason = "expected true/false, yes/no or on/off but found '$raw'"
+                throw path?.let { YamlException(reason, it) } ?: SerializationException(reason)
+            }
+        }
+    }
+
+    override fun serialize(
+        encoder: Encoder,
+        value: Boolean,
+    ) = encoder.encodeString(value.toString())
+}
diff --git a/platform-paper/src/main/kotlin/dev/m1sk9/lunaticChat/paper/config/LunaticChatConfiguration.kt b/platform-paper/src/main/kotlin/dev/m1sk9/lunaticChat/paper/config/LunaticChatConfiguration.kt
index 92bc157..facd6ac 100644
--- a/platform-paper/src/main/kotlin/dev/m1sk9/lunaticChat/paper/config/LunaticChatConfiguration.kt
+++ b/platform-paper/src/main/kotlin/dev/m1sk9/lunaticChat/paper/config/LunaticChatConfiguration.kt
@@ -3,12 +3,23 @@ package dev.m1sk9.lunaticChat.paper.config
 import dev.m1sk9.lunaticChat.paper.config.key.FeaturesConfig
 import dev.m1sk9.lunaticChat.paper.config.key.MessageFormatConfig
 import dev.m1sk9.lunaticChat.paper.i18n.Language
+import dev.m1sk9.lunaticChat.paper.i18n.LanguageSerializer
+import kotlinx.serialization.Serializable
 
+/**
+ * The shape of config.yml.
+ *
+ * Every property carries the default that config.yml documents, and it is the only place that
+ * default is written: the file is deserialized straight into this tree, so a key the user has not
+ * set simply falls back here.
+ */
+@Serializable
 data class LunaticChatConfiguration(
-    val features: FeaturesConfig,
-    val messageFormat: MessageFormatConfig,
-    val debug: Boolean = false,
+    val features: FeaturesConfig = FeaturesConfig(),
+    val messageFormat: MessageFormatConfig = MessageFormatConfig(),
+    val debug: LenientBoolean = false,
     val userSettingsFilePath: String = "player-settings.yaml",
-    val checkForUpdates: Boolean = true,
+    val checkForUpdates: LenientBoolean = true,
+    @Serializable(with = LanguageSerializer::class)
     val language: Language = Language.EN,
 )
diff --git a/platform-paper/src/main/kotlin/dev/m1sk9/lunaticChat/paper/config/key/ChannelChatFeatureConfig.kt b/platform-paper/src/main/kotlin/dev/m1sk9/lunaticChat/paper/config/key/ChannelChatFeatureConfig.kt
index 9a64428..b46147d 100644
--- a/platform-paper/src/main/kotlin/dev/m1sk9/lunaticChat/paper/config/key/ChannelChatFeatureConfig.kt
+++ b/platform-paper/src/main/kotlin/dev/m1sk9/lunaticChat/paper/config/key/ChannelChatFeatureConfig.kt
@@ -1,10 +1,11 @@
 package dev.m1sk9.lunaticChat.paper.config.key
 
+import dev.m1sk9.lunaticChat.paper.config.LenientBoolean
 import kotlinx.serialization.Serializable
 
 @Serializable
 data class ChannelChatFeatureConfig(
-    val enabled: Boolean,
+    val enabled: LenientBoolean = false,
     val maxChannelsPerServer: Int = 0,
     val maxMembersPerChannel: Int = 0,
     val maxMembershipPerPlayer: Int = 0,
diff --git a/platform-paper/src/main/kotlin/dev/m1sk9/lunaticChat/paper/config/key/ChannelMessageLoggingConfig.kt b/platform-paper/src/main/kotlin/dev/m1sk9/lunaticChat/paper/config/key/ChannelMessageLoggingConfig.kt
index f036620..1a1d23b 100644
--- a/platform-paper/src/main/kotlin/dev/m1sk9/lunaticChat/paper/config/key/ChannelMessageLoggingConfig.kt
+++ b/platform-paper/src/main/kotlin/dev/m1sk9/lunaticChat/paper/config/key/ChannelMessageLoggingConfig.kt
@@ -1,5 +1,6 @@
 package dev.m1sk9.lunaticChat.paper.config.key
 
+import dev.m1sk9.lunaticChat.paper.config.LenientBoolean
 import kotlinx.serialization.Serializable
 
 /**
@@ -14,7 +15,7 @@ import kotlinx.serialization.Serializable
  */
 @Serializable
 data class ChannelMessageLoggingConfig(
-    val enabled: Boolean = true,
+    val enabled: LenientBoolean = true,
     val retentionDays: Int = 30,
     val maxFileSizeMB: Int = 100,
 )
diff --git a/platform-paper/src/main/kotlin/dev/m1sk9/lunaticChat/paper/config/key/FeaturesConfig.kt b/platform-paper/src/main/kotlin/dev/m1sk9/lunaticChat/paper/config/key/FeaturesConfig.kt
index 044838d..69e1e1b 100644
--- a/platform-paper/src/main/kotlin/dev/m1sk9/lunaticChat/paper/config/key/FeaturesConfig.kt
+++ b/platform-paper/src/main/kotlin/dev/m1sk9/lunaticChat/paper/config/key/FeaturesConfig.kt
@@ -1,8 +1,11 @@
 package dev.m1sk9.lunaticChat.paper.config.key
 
+import kotlinx.serialization.Serializable
+
+@Serializable
 data class FeaturesConfig(
-    val quickReplies: QuickRepliesFeatureConfig,
-    val japaneseConversion: JapaneseConversionFeatureConfig,
-    val channelChat: ChannelChatFeatureConfig,
-    val velocityIntegration: VelocityIntegrationConfig,
+    val quickReplies: QuickRepliesFeatureConfig = QuickRepliesFeatureConfig(),
+    val japaneseConversion: JapaneseConversionFeatureConfig = JapaneseConversionFeatureConfig(),
+    val channelChat: ChannelChatFeatureConfig = ChannelChatFeatureConfig(),
+    val velocityIntegration: VelocityIntegrationConfig = VelocityIntegrationConfig(),
 )
diff --git a/platform-paper/src/main/kotlin/dev/m1sk9/lunaticChat/paper/config/key/JapaneseConversionFeatureConfig.kt b/platform-paper/src/main/kotlin/dev/m1sk9/lunaticChat/paper/config/key/JapaneseConversionFeatureConfig.kt
index c329085..845a294 100644
--- a/platform-paper/src/main/kotlin/dev/m1sk9/lunaticChat/paper/config/key/JapaneseConversionFeatureConfig.kt
+++ b/platform-paper/src/main/kotlin/dev/m1sk9/lunaticChat/paper/config/key/JapaneseConversionFeatureConfig.kt
@@ -1,10 +1,36 @@
 package dev.m1sk9.lunaticChat.paper.config.key
 
+import dev.m1sk9.lunaticChat.paper.config.LenientBoolean
+import kotlinx.serialization.Serializable
+
+/**
+ * @property enabled Whether romaji-to-Japanese conversion is offered to players
+ * @property cache Conversion cache tuning
+ * @property api Google IME request tuning
+ */
+@Serializable
 data class JapaneseConversionFeatureConfig(
-    val enabled: Boolean,
-    val cacheMaxEntries: Int,
-    val cacheSaveIntervalSeconds: Int,
-    val cacheFilePath: String,
-    val apiTimeout: Long,
-    val apiRetryAttempts: Int,
+    val enabled: LenientBoolean = false,
+    val cache: ConversionCacheConfig = ConversionCacheConfig(),
+    val api: ConversionApiConfig = ConversionApiConfig(),
+)
+
+/**
+ * @property maxEntries Upper bound on cached word conversions
+ * @property saveIntervalSeconds How often the cache is flushed to disk
+ * @property filePath Cache file, relative to the plugin data folder
+ */
+@Serializable
+data class ConversionCacheConfig(
+    val maxEntries: Int = 500,
+    val saveIntervalSeconds: Int = 300,
+    val filePath: String = "conversion_cache.json",
+)
+
+/**
+ * @property timeout Per-request timeout in milliseconds
+ */
+@Serializable
+data class ConversionApiConfig(
+    val timeout: Long = 3000,
 )
diff --git a/platform-paper/src/main/kotlin/dev/m1sk9/lunaticChat/paper/config/key/MessageFormatConfig.kt b/platform-paper/src/main/kotlin/dev/m1sk9/lunaticChat/paper/config/key/MessageFormatConfig.kt
index d31ec4e..481f259 100644
--- a/platform-paper/src/main/kotlin/dev/m1sk9/lunaticChat/paper/config/key/MessageFormatConfig.kt
+++ b/platform-paper/src/main/kotlin/dev/m1sk9/lunaticChat/paper/config/key/MessageFormatConfig.kt
@@ -1,5 +1,8 @@
 package dev.m1sk9.lunaticChat.paper.config.key
 
+import kotlinx.serialization.Serializable
+
+@Serializable
 data class MessageFormatConfig(
     val directMessageFormat: String = "§7[§e{sender} §7>> §e{recipient}§7] §f{message}",
     val channelMessageFormat: String = "§7[§b#{channel}§7] §e{sender}: §f{message}",
diff --git a/platform-paper/src/main/kotlin/dev/m1sk9/lunaticChat/paper/config/key/QuickRepliesFeatureConfig.kt b/platform-paper/src/main/kotlin/dev/m1sk9/lunaticChat/paper/config/key/QuickRepliesFeatureConfig.kt
index cf0c00d..524cc57 100644
--- a/platform-paper/src/main/kotlin/dev/m1sk9/lunaticChat/paper/config/key/QuickRepliesFeatureConfig.kt
+++ b/platform-paper/src/main/kotlin/dev/m1sk9/lunaticChat/paper/config/key/QuickRepliesFeatureConfig.kt
@@ -1,5 +1,9 @@
 package dev.m1sk9.lunaticChat.paper.config.key
 
+import dev.m1sk9.lunaticChat.paper.config.LenientBoolean
+import kotlinx.serialization.Serializable
+
+@Serializable
 data class QuickRepliesFeatureConfig(
-    val enabled: Boolean,
+    val enabled: LenientBoolean = true,
 )
diff --git a/platform-paper/src/main/kotlin/dev/m1sk9/lunaticChat/paper/config/key/VelocityIntegrationConfig.kt b/platform-paper/src/main/kotlin/dev/m1sk9/lunaticChat/paper/config/key/VelocityIntegrationConfig.kt
index 2b2babb..927b7a0 100644
--- a/platform-paper/src/main/kotlin/dev/m1sk9/lunaticChat/paper/config/key/VelocityIntegrationConfig.kt
+++ b/platform-paper/src/main/kotlin/dev/m1sk9/lunaticChat/paper/config/key/VelocityIntegrationConfig.kt
@@ -1,9 +1,13 @@
 package dev.m1sk9.lunaticChat.paper.config.key
 
+import dev.m1sk9.lunaticChat.paper.config.LenientBoolean
+import kotlinx.serialization.Serializable
+
+@Serializable
 data class VelocityIntegrationConfig(
-    val enabled: Boolean = false,
-    val crossServerGlobalChat: Boolean = false,
-    val crossServerDirectMessage: Boolean = false,
+    val enabled: LenientBoolean = false,
+    val crossServerGlobalChat: LenientBoolean = false,
+    val crossServerDirectMessage: LenientBoolean = false,
     val serverName: String = "Unknown",
     val messageDeduplicationCacheSize: Int = 100,
 )
diff --git a/engine/src/main/kotlin/dev/m1sk9/lunaticChat/engine/converter/CacheData.kt b/platform-paper/src/main/kotlin/dev/m1sk9/lunaticChat/paper/converter/CacheData.kt
index 1f335b4..06bf3f0 100644
--- a/engine/src/main/kotlin/dev/m1sk9/lunaticChat/engine/converter/CacheData.kt
+++ b/platform-paper/src/main/kotlin/dev/m1sk9/lunaticChat/paper/converter/CacheData.kt
@@ -1,4 +1,4 @@
-package dev.m1sk9.lunaticChat.engine.converter
+package dev.m1sk9.lunaticChat.paper.converter
 
 import kotlinx.serialization.Serializable
 
diff --git a/platform-paper/src/main/kotlin/dev/m1sk9/lunaticChat/paper/converter/ConversionCache.kt b/platform-paper/src/main/kotlin/dev/m1sk9/lunaticChat/paper/converter/ConversionCache.kt
index c550f09..cba62af 100644
--- a/platform-paper/src/main/kotlin/dev/m1sk9/lunaticChat/paper/converter/ConversionCache.kt
+++ b/platform-paper/src/main/kotlin/dev/m1sk9/lunaticChat/paper/converter/ConversionCache.kt
@@ -1,6 +1,5 @@
 package dev.m1sk9.lunaticChat.paper.converter
 
-import dev.m1sk9.lunaticChat.engine.converter.CacheData
 import dev.m1sk9.lunaticChat.paper.writeTextAtomically
 import kotlinx.serialization.json.Json
 import java.nio.file.Path
diff --git a/engine/src/main/kotlin/dev/m1sk9/lunaticChat/engine/converter/GoogleIMEClient.kt b/platform-paper/src/main/kotlin/dev/m1sk9/lunaticChat/paper/converter/GoogleIMEClient.kt
index 4a23bc7..0689ad4 100644
--- a/engine/src/main/kotlin/dev/m1sk9/lunaticChat/engine/converter/GoogleIMEClient.kt
+++ b/platform-paper/src/main/kotlin/dev/m1sk9/lunaticChat/paper/converter/GoogleIMEClient.kt
@@ -1,4 +1,4 @@
-package dev.m1sk9.lunaticChat.engine.converter
+package dev.m1sk9.lunaticChat.paper.converter
 
 import io.ktor.client.HttpClient
 import io.ktor.client.call.body
diff --git a/engine/src/main/kotlin/dev/m1sk9/lunaticChat/engine/converter/KanaConverter.kt b/platform-paper/src/main/kotlin/dev/m1sk9/lunaticChat/paper/converter/KanaConverter.kt
index bdbdf69..544eea7 100644
--- a/engine/src/main/kotlin/dev/m1sk9/lunaticChat/engine/converter/KanaConverter.kt
+++ b/platform-paper/src/main/kotlin/dev/m1sk9/lunaticChat/paper/converter/KanaConverter.kt
@@ -1,4 +1,4 @@
-package dev.m1sk9.lunaticChat.engine.converter
+package dev.m1sk9.lunaticChat.paper.converter
 
 /**
  * Converts romanji text to hiragana using Trie data structure.
diff --git a/platform-paper/src/main/kotlin/dev/m1sk9/lunaticChat/paper/converter/RomanjiConverter.kt b/platform-paper/src/main/kotlin/dev/m1sk9/lunaticChat/paper/converter/RomanjiConverter.kt
index 530d3dc..100aeb3 100644
--- a/platform-paper/src/main/kotlin/dev/m1sk9/lunaticChat/paper/converter/RomanjiConverter.kt
+++ b/platform-paper/src/main/kotlin/dev/m1sk9/lunaticChat/paper/converter/RomanjiConverter.kt
@@ -1,7 +1,5 @@
 package dev.m1sk9.lunaticChat.paper.converter
 
-import dev.m1sk9.lunaticChat.engine.converter.GoogleIMEClient
-import dev.m1sk9.lunaticChat.engine.converter.KanaConverter
 import kotlinx.coroutines.CancellationException
 import kotlinx.coroutines.async
 import kotlinx.coroutines.awaitAll
diff --git a/platform-paper/src/main/kotlin/dev/m1sk9/lunaticChat/paper/i18n/LanguageSerializer.kt b/platform-paper/src/main/kotlin/dev/m1sk9/lunaticChat/paper/i18n/LanguageSerializer.kt
new file mode 100644
index 0000000..080f0d5
--- /dev/null
+++ b/platform-paper/src/main/kotlin/dev/m1sk9/lunaticChat/paper/i18n/LanguageSerializer.kt
@@ -0,0 +1,28 @@
+package dev.m1sk9.lunaticChat.paper.i18n
+
+import kotlinx.serialization.KSerializer
+import kotlinx.serialization.descriptors.PrimitiveKind
+import kotlinx.serialization.descriptors.PrimitiveSerialDescriptor
+import kotlinx.serialization.descriptors.SerialDescriptor
+import kotlinx.serialization.encoding.Decoder
+import kotlinx.serialization.encoding.Encoder
+
+/**
+ * Reads a [Language] from its code, as written in config.yml.
+ *
+ * Goes through [Language.fromCode] rather than the enum name so the lookup stays
+ * case-insensitive and an unrecognised code falls back to English, instead of failing the whole
+ * configuration over one typo.
+ */
+object LanguageSerializer : KSerializer<Language> {
+    override val descriptor: SerialDescriptor = PrimitiveSerialDescriptor("Language", PrimitiveKind.STRING)
+
+    override fun deserialize(decoder: Decoder): Language = Language.fromCode(decoder.decodeString())
+
+    override fun serialize(
+        encoder: Encoder,
+        value: Language,
+    ) {
+        encoder.encodeString(value.code)
+    }
+}
diff --git a/platform-paper/src/main/kotlin/dev/m1sk9/lunaticChat/paper/velocity/CrossServerDirectMessageManager.kt b/platform-paper/src/main/kotlin/dev/m1sk9/lunaticChat/paper/velocity/CrossServerDirectMessageManager.kt
index ccd8d40..8328ad8 100644
--- a/platform-paper/src/main/kotlin/dev/m1sk9/lunaticChat/paper/velocity/CrossServerDirectMessageManager.kt
+++ b/platform-paper/src/main/kotlin/dev/m1sk9/lunaticChat/paper/velocity/CrossServerDirectMessageManager.kt
@@ -132,7 +132,7 @@ class CrossServerDirectMessageManager(
                     val messageKey =
                         when (error.reason) {
                             PluginMessage.DirectMessageError.Reason.SERVER_NOT_FOUND -> "directMessage.remoteServerNotFound"
-                            else -> "directMessage.remoteTargetOffline"
+                            PluginMessage.DirectMessageError.Reason.TARGET_OFFLINE -> "directMessage.remoteTargetOffline"
                         }
                     val text =
                         languageManager.getMessage(
diff --git a/platform-paper/src/main/resources/config.yml b/platform-paper/src/main/resources/config.yml
index 111d90b..37bfdc6 100644
--- a/platform-paper/src/main/resources/config.yml
+++ b/platform-paper/src/main/resources/config.yml
@@ -46,8 +46,6 @@ features:
     api:
       # Specify the timeout duration (in milliseconds) for API requests to the Romanization conversion service.
       timeout: 3000
-      # Specify the number of retry attempts for failed API requests to the Romanization conversion service.
-      retryAttempts: 2
   channelChat:
     # If enabled, channel-based chat functionality will be activated.
     enabled: false
diff --git a/platform-paper/src/test/kotlin/dev/m1sk9/lunaticChat/paper/TestUtils.kt b/platform-paper/src/test/kotlin/dev/m1sk9/lunaticChat/paper/TestUtils.kt
index 2d2a7c7..4bca21f 100644
--- a/platform-paper/src/test/kotlin/dev/m1sk9/lunaticChat/paper/TestUtils.kt
+++ b/platform-paper/src/test/kotlin/dev/m1sk9/lunaticChat/paper/TestUtils.kt
@@ -6,6 +6,7 @@ import dev.m1sk9.lunaticChat.engine.chat.channel.ChannelRole
 import dev.m1sk9.lunaticChat.engine.settings.PlayerChatSettings
 import dev.m1sk9.lunaticChat.paper.config.LunaticChatConfiguration
 import dev.m1sk9.lunaticChat.paper.config.key.ChannelChatFeatureConfig
+import dev.m1sk9.lunaticChat.paper.config.key.ConversionCacheConfig
 import dev.m1sk9.lunaticChat.paper.config.key.FeaturesConfig
 import dev.m1sk9.lunaticChat.paper.config.key.JapaneseConversionFeatureConfig
 import dev.m1sk9.lunaticChat.paper.config.key.MessageFormatConfig
@@ -86,11 +87,7 @@ object TestUtils {
                     japaneseConversion =
                         JapaneseConversionFeatureConfig(
                             enabled = japaneseConversionEnabled,
-                            cacheMaxEntries = 500,
-                            cacheSaveIntervalSeconds = 300,
-                            cacheFilePath = "test-conversion-cache.json",
-                            apiTimeout = 3000,
-                            apiRetryAttempts = 2,
+                            cache = ConversionCacheConfig(filePath = "test-conversion-cache.json"),
                         ),
                     channelChat =
                         ChannelChatFeatureConfig(
diff --git a/platform-paper/src/test/kotlin/dev/m1sk9/lunaticChat/paper/config/ConfigManagerTest.kt b/platform-paper/src/test/kotlin/dev/m1sk9/lunaticChat/paper/config/ConfigManagerTest.kt
index 3f936f6..d415e97 100644
--- a/platform-paper/src/test/kotlin/dev/m1sk9/lunaticChat/paper/config/ConfigManagerTest.kt
+++ b/platform-paper/src/test/kotlin/dev/m1sk9/lunaticChat/paper/config/ConfigManagerTest.kt
@@ -1,288 +1,292 @@
 package dev.m1sk9.lunaticChat.paper.config
 
+import dev.m1sk9.lunaticChat.paper.TestUtils
 import dev.m1sk9.lunaticChat.paper.i18n.Language
-import io.mockk.every
-import io.mockk.mockk
-import org.bukkit.configuration.file.FileConfiguration
 import kotlin.test.Test
 import kotlin.test.assertEquals
 import kotlin.test.assertFalse
-import kotlin.test.assertNotNull
 import kotlin.test.assertTrue
 
 /**
- * Tests for ConfigManager to ensure proper configuration loading and parsing.
+ * Tests for ConfigManager.
+ *
+ * These parse real YAML rather than a mocked Bukkit FileConfiguration, so they exercise the same
+ * path the plugin uses at startup - including what happens to a file that is incomplete, stale or
+ * malformed.
  */
 class ConfigManagerTest {
-    private fun createMockConfig(values: Map<String, Any> = emptyMap()): FileConfiguration {
-        val config = mockk<FileConfiguration>(relaxed = true)
-
-        // Set up default values
-        every { config.getBoolean(any(), any()) } answers {
-            val key = firstArg<String>()
-            val default = secondArg<Boolean>()
-            (values[key] as? Boolean) ?: default
-        }
-
-        every { config.getInt(any(), any()) } answers {
-            val key = firstArg<String>()
-            val default = secondArg<Int>()
-            (values[key] as? Int) ?: default
-        }
-
-        every { config.getLong(any(), any()) } answers {
-            val key = firstArg<String>()
-            val default = secondArg<Long>()
-            (values[key] as? Long) ?: default
-        }
-
-        every { config.getString(any(), any()) } answers {
-            val key = firstArg<String>()
-            val default = secondArg<String>()
-            (values[key] as? String) ?: default
-        }
-
-        every { config.getString(any()) } answers {
-            val key = firstArg<String>()
-            values[key] as? String
-        }
-
-        return config
+    private fun load(yaml: String) = ConfigManager(TestUtils.TestLogger()).loadConfiguration(yaml)
+
+    /** The file shipped in resources, which is what a fresh install actually reads. */
+    private val bundledConfig: String =
+        checkNotNull(javaClass.classLoader.getResourceAsStream("config.yml")) {
+            "config.yml missing from resources"
+        }.bufferedReader().use { it.readText() }
+
+    @Test
+    fun `the bundled config parses`() {
+        val config = load(bundledConfig)
+
+        assertFalse(config.debug)
+        assertEquals("player-settings.yaml", config.userSettingsFilePath)
+        assertEquals(Language.EN, config.language)
     }
 
     @Test
-    fun `loadConfiguration should load all default values`() {
-        val configManager = ConfigManager()
-        val mockConfig = createMockConfig()
-
-        val configuration = configManager.loadConfiguration(mockConfig)
-
-        assertNotNull(configuration)
-        assertTrue(configuration.features.quickReplies.enabled)
-        assertFalse(configuration.features.japaneseConversion.enabled)
-        assertFalse(configuration.features.channelChat.enabled)
-        assertFalse(configuration.debug)
-        assertFalse(configuration.checkForUpdates)
-        assertEquals(Language.EN, configuration.language)
+    fun `the bundled config agrees with the declared defaults`() {
+        // The data class is meant to be the single source of every default. If config.yml ships a
+        // different value for a key, one of the two is lying to the operator.
+        assertEquals(LunaticChatConfiguration(), load(bundledConfig))
     }
 
     @Test
-    fun `loadConfiguration should load quick replies configuration`() {
-        val configManager = ConfigManager()
-        val mockConfig =
-            createMockConfig(
-                mapOf(
-                    "features.quickReplies.enabled" to false,
-                ),
-            )
+    fun `an empty document falls back to defaults`() {
+        assertEquals(LunaticChatConfiguration(), load("{}"))
+    }
 
-        val configuration = configManager.loadConfiguration(mockConfig)
+    @Test
+    fun `a config missing a section keeps that section's defaults`() {
+        val config = load("debug: true")
 
-        assertFalse(configuration.features.quickReplies.enabled)
+        assertTrue(config.debug)
+        assertEquals(LunaticChatConfiguration().features, config.features)
+        assertEquals(LunaticChatConfiguration().messageFormat, config.messageFormat)
     }
 
     @Test
-    fun `loadConfiguration should load Japanese conversion configuration`() {
-        val configManager = ConfigManager()
-        val mockConfig =
-            createMockConfig(
-                mapOf(
-                    "features.japaneseConversion.enabled" to true,
-                    "features.japaneseConversion.cache.maxEntries" to 1000,
-                    "features.japaneseConversion.cache.saveIntervalSeconds" to 600,
-                    "features.japaneseConversion.cache.filePath" to "custom_cache.json",
-                    "features.japaneseConversion.api.timeout" to 5000L,
-                    "features.japaneseConversion.api.retryAttempts" to 3,
-                ),
+    fun `values present in the file win over the defaults`() {
+        val config =
+            load(
+                """
+                debug: true
+                checkForUpdates: false
+                userSettingsFilePath: "custom.yaml"
+                language: "ja"
+                """.trimIndent(),
             )
 
-        val configuration = configManager.loadConfiguration(mockConfig)
+        assertTrue(config.debug)
+        assertFalse(config.checkForUpdates)
+        assertEquals("custom.yaml", config.userSettingsFilePath)
+        assertEquals(Language.JA, config.language)
+    }
 
-        assertTrue(configuration.features.japaneseConversion.enabled)
-        assertEquals(1000, configuration.features.japaneseConversion.cacheMaxEntries)
-        assertEquals(600, configuration.features.japaneseConversion.cacheSaveIntervalSeconds)
-        assertEquals("custom_cache.json", configuration.features.japaneseConversion.cacheFilePath)
-        assertEquals(5000L, configuration.features.japaneseConversion.apiTimeout)
-        assertEquals(3, configuration.features.japaneseConversion.apiRetryAttempts)
+    @Test
+    fun `an unknown language code falls back to English`() {
+        assertEquals(Language.EN, load("""language: "kl"""").language)
     }
 
     @Test
-    fun `loadConfiguration should load channel chat configuration`() {
-        val configManager = ConfigManager()
-        val mockConfig =
-            createMockConfig(
-                mapOf(
-                    "features.channelChat.enabled" to true,
-                    "features.channelChat.maxChannelsPerServer" to 20,
-                    "features.channelChat.maxMembersPerChannel" to 100,
-                    "features.channelChat.maxMembershipPerPlayer" to 10,
-                ),
-            )
+    fun `a language code is matched regardless of case`() {
+        assertEquals(Language.JA, load("""language: "JA"""").language)
+    }
 
-        val configuration = configManager.loadConfiguration(mockConfig)
+    @Test
+    fun `nested japanese conversion settings are read`() {
+        val config =
+            load(
+                """
+                features:
+                  japaneseConversion:
+                    enabled: true
+                    cache:
+                      maxEntries: 1000
+                      saveIntervalSeconds: 600
+                      filePath: "custom_cache.json"
+                    api:
+                      timeout: 5000
+                """.trimIndent(),
+            )
 
-        assertTrue(configuration.features.channelChat.enabled)
-        assertEquals(20, configuration.features.channelChat.maxChannelsPerServer)
-        assertEquals(100, configuration.features.channelChat.maxMembersPerChannel)
-        assertEquals(10, configuration.features.channelChat.maxMembershipPerPlayer)
+        val japanese = config.features.japaneseConversion
+        assertTrue(japanese.enabled)
+        assertEquals(1000, japanese.cache.maxEntries)
+        assertEquals(600, japanese.cache.saveIntervalSeconds)
+        assertEquals("custom_cache.json", japanese.cache.filePath)
+        assertEquals(5000L, japanese.api.timeout)
     }
 
     @Test
-    fun `loadConfiguration should load message format configuration`() {
-        val configManager = ConfigManager()
-        val customDMFormat = "DM: {sender} -> {recipient}: {message}"
-        val customChannelFormat = "[{channel}] {sender}: {message}"
-        val mockConfig =
-            createMockConfig(
-                mapOf(
-                    "messageFormat.directMessageFormat" to customDMFormat,
-                    "messageFormat.channelMessageFormat" to customChannelFormat,
-                ),
+    fun `channel message logging is read from the file`() {
+        // This block was documented in config.yml but never parsed, so editing it did nothing.
+        val config =
+            load(
+                """
+                features:
+                  channelChat:
+                    enabled: true
+                    messageLogging:
+                      enabled: false
+                      retentionDays: 7
+                      maxFileSizeMB: 20
+                """.trimIndent(),
             )
 
-        val configuration = configManager.loadConfiguration(mockConfig)
-
-        assertEquals(customDMFormat, configuration.messageFormat.directMessageFormat)
-        assertEquals(customChannelFormat, configuration.messageFormat.channelMessageFormat)
+        val logging = config.features.channelChat.messageLogging
+        assertFalse(logging.enabled)
+        assertEquals(7, logging.retentionDays)
+        assertEquals(20, logging.maxFileSizeMB)
     }
 
     @Test
-    fun `loadConfiguration should load debug and update check settings`() {
-        val configManager = ConfigManager()
-        val mockConfig =
-            createMockConfig(
-                mapOf(
-                    "debug" to true,
-                    "checkForUpdates" to true,
-                ),
+    fun `velocity integration settings are read from the file`() {
+        val config =
+            load(
+                """
+                features:
+                  velocityIntegration:
+                    enabled: true
+                    crossServerGlobalChat: true
+                    crossServerDirectMessage: true
+                    serverName: "survival"
+                    messageDeduplicationCacheSize: 250
+                """.trimIndent(),
             )
 
-        val configuration = configManager.loadConfiguration(mockConfig)
-
-        assertTrue(configuration.debug)
-        assertTrue(configuration.checkForUpdates)
+        val velocity = config.features.velocityIntegration
+        assertTrue(velocity.enabled)
+        assertTrue(velocity.crossServerGlobalChat)
+        assertTrue(velocity.crossServerDirectMessage)
+        assertEquals("survival", velocity.serverName)
+        assertEquals(250, velocity.messageDeduplicationCacheSize)
     }
 
     @Test
-    fun `loadConfiguration should load custom settings file path`() {
-        val configManager = ConfigManager()
-        val customPath = "custom-player-settings.yaml"
-        val mockConfig =
-            createMockConfig(
-                mapOf(
-                    "userSettingsFilePath" to customPath,
-                ),
+    fun `message formats are read from the file`() {
+        val config =
+            load(
+                """
+                messageFormat:
+                  directMessageFormat: "DM {sender} {message}"
+                  channelMessageFormat: "CH {channel} {message}"
+                  crossServerGlobalChatFormat: "GL {server} {message}"
+                """.trimIndent(),
             )
 
-        val configuration = configManager.loadConfiguration(mockConfig)
+        assertEquals("DM {sender} {message}", config.messageFormat.directMessageFormat)
+        assertEquals("CH {channel} {message}", config.messageFormat.channelMessageFormat)
+        assertEquals("GL {server} {message}", config.messageFormat.crossServerGlobalChatFormat)
+    }
+
+    @Test
+    fun `a key this build no longer knows is ignored`() {
+        // An operator upgrading from a build that had extra keys must still be able to start.
+        val config = load("debug: true\nsomeRetiredOption: 42")
 
-        assertEquals(customPath, configuration.userSettingsFilePath)
+        assertTrue(config.debug)
     }
 
     @Test
-    fun `loadConfiguration should load Japanese language`() {
-        val configManager = ConfigManager()
-        val mockConfig =
-            createMockConfig(
-                mapOf(
-                    "language" to "ja",
-                ),
-            )
+    fun `a document that is not YAML at all says that every setting was reset`() {
+        val logger = TestUtils.TestLogger()
 
-        val configuration = configManager.loadConfiguration(mockConfig)
+        val config = ConfigManager(logger).loadConfiguration("features: [this is not a map")
 
-        assertEquals(Language.JA, configuration.language)
+        assertEquals(LunaticChatConfiguration(), config)
+        assertTrue(logger.severeMessages.any { it.contains("EVERY setting") })
     }
 
     @Test
-    fun `loadConfiguration should handle unknown language code`() {
-        val configManager = ConfigManager()
-        val mockConfig =
-            createMockConfig(
-                mapOf(
-                    "language" to "fr", // French not supported
-                ),
-            )
+    fun `a file the YAML reader rejects before parsing still leaves the plugin running`() {
+        val logger = TestUtils.TestLogger()
+        // What a config.yml saved as UTF-16 looks like once it is read back as UTF-8: the scanner
+        // refuses it over the NUL bytes, before anything is YAML.
+        val notUtf8 = String("debug: true".toByteArray(Charsets.UTF_16), Charsets.UTF_8)
 
-        val configuration = configManager.loadConfiguration(mockConfig)
+        val config = ConfigManager(logger).loadConfiguration(notUtf8)
 
-        // Should fall back to English
-        assertEquals(Language.EN, configuration.language)
+        assertEquals(LunaticChatConfiguration(), config)
+        assertTrue(logger.severeMessages.any { it.contains("EVERY setting") })
     }
 
     @Test
-    fun `loadConfiguration should use default values when keys are missing`() {
-        val configManager = ConfigManager()
-        val mockConfig = createMockConfig(emptyMap())
-
-        val configuration = configManager.loadConfiguration(mockConfig)
-
-        // All features should have their defaults
-        assertTrue(configuration.features.quickReplies.enabled)
-        assertEquals(500, configuration.features.japaneseConversion.cacheMaxEntries)
-        assertEquals(300, configuration.features.japaneseConversion.cacheSaveIntervalSeconds)
-        assertEquals("conversion_cache.json", configuration.features.japaneseConversion.cacheFilePath)
-        assertEquals(3000L, configuration.features.japaneseConversion.apiTimeout)
-        assertEquals(2, configuration.features.japaneseConversion.apiRetryAttempts)
-        assertEquals(0, configuration.features.channelChat.maxChannelsPerServer)
-        assertEquals(0, configuration.features.channelChat.maxMembersPerChannel)
-        assertEquals(0, configuration.features.channelChat.maxMembershipPerPlayer)
+    fun `a leading byte order mark does not cost the first setting`() {
+        assertTrue(load("\uFEFFdebug: true").debug)
     }
 
     @Test
-    fun `loadConfiguration can be called multiple times`() {
-        val configManager = ConfigManager()
-        val mockConfig1 =
-            createMockConfig(
-                mapOf("debug" to true),
-            )
-        val mockConfig2 =
-            createMockConfig(
-                mapOf("debug" to false),
-            )
+    fun `a file holding only comments is not reported as a failure`() {
+        val logger = TestUtils.TestLogger()
 
-        val config1 = configManager.loadConfiguration(mockConfig1)
-        val config2 = configManager.loadConfiguration(mockConfig2)
+        val config = ConfigManager(logger).loadConfiguration("# everything left at its default\n")
 
-        assertTrue(config1.debug)
-        assertFalse(config2.debug)
+        assertEquals(LunaticChatConfiguration(), config)
+        assertTrue(logger.severeMessages.isEmpty())
     }
 
     @Test
-    fun `loadConfiguration should handle all features enabled`() {
-        val configManager = ConfigManager()
-        val mockConfig =
-            createMockConfig(
-                mapOf(
-                    "features.quickReplies.enabled" to true,
-                    "features.japaneseConversion.enabled" to true,
-                    "features.channelChat.enabled" to true,
-                ),
-            )
+    fun `the boolean spellings Bukkit accepted are still booleans`() {
+        // Bukkit read config.yml as YAML 1.1, where these are booleans. A file written against that
+        // must keep meaning what it says.
+        val config = load("debug: yes\ncheckForUpdates: off")
 
-        val configuration = configManager.loadConfiguration(mockConfig)
+        assertTrue(config.debug)
+        assertFalse(config.checkForUpdates)
+    }
 
-        assertTrue(configuration.features.quickReplies.enabled)
-        assertTrue(configuration.features.japaneseConversion.enabled)
-        assertTrue(configuration.features.channelChat.enabled)
+    @Test
+    fun `boolean spellings are matched regardless of case`() {
+        assertTrue(load("debug: YES").debug)
     }
 
     @Test
-    fun `loadConfiguration should handle all features disabled`() {
-        val configManager = ConfigManager()
-        val mockConfig =
-            createMockConfig(
-                mapOf(
-                    "features.quickReplies.enabled" to false,
-                    "features.japaneseConversion.enabled" to false,
-                    "features.channelChat.enabled" to false,
-                ),
+    fun `an unreadable setting falls back alone and leaves the rest of the file standing`() {
+        val logger = TestUtils.TestLogger()
+
+        val config =
+            ConfigManager(logger).loadConfiguration(
+                """
+                debug: perhaps
+                userSettingsFilePath: "custom.yaml"
+                language: "ja"
+                """.trimIndent(),
             )
 
-        val configuration = configManager.loadConfiguration(mockConfig)
+        assertFalse(config.debug)
+        assertEquals("custom.yaml", config.userSettingsFilePath)
+        assertEquals(Language.JA, config.language)
+        assertTrue(logger.warningMessages.any { it.contains("debug") })
+        assertTrue(logger.severeMessages.isEmpty())
+    }
+
+    @Test
+    fun `an unreadable nested setting leaves its siblings standing`() {
+        val logger = TestUtils.TestLogger()
+
+        val config =
+            ConfigManager(logger).loadConfiguration(
+                """
+                features:
+                  velocityIntegration:
+                    enabled: true
+                    serverName: "survival"
+                    messageDeduplicationCacheSize: "not a number"
+                """.trimIndent(),
+            )
+
+        val velocity = config.features.velocityIntegration
+        assertTrue(velocity.enabled)
+        assertEquals("survival", velocity.serverName)
+        assertEquals(
+            LunaticChatConfiguration().features.velocityIntegration.messageDeduplicationCacheSize,
+            velocity.messageDeduplicationCacheSize,
+        )
+        assertTrue(logger.warningMessages.any { it.contains("features.velocityIntegration.messageDeduplicationCacheSize") })
+    }
+
+    @Test
+    fun `several unreadable settings each fall back without taking the others`() {
+        val config =
+            load(
+                """
+                debug: perhaps
+                checkForUpdates: sometimes
+                userSettingsFilePath: "custom.yaml"
+                """.trimIndent(),
+            )
 
-        assertFalse(configuration.features.quickReplies.enabled)
-        assertFalse(configuration.features.japaneseConversion.enabled)
-        assertFalse(configuration.features.channelChat.enabled)
+        assertFalse(config.debug)
+        assertTrue(config.checkForUpdates)
+        assertEquals("custom.yaml", config.userSettingsFilePath)
     }
 }
diff --git a/platform-paper/src/test/kotlin/dev/m1sk9/lunaticChat/paper/converter/CacheDataTest.kt b/platform-paper/src/test/kotlin/dev/m1sk9/lunaticChat/paper/converter/CacheDataTest.kt
new file mode 100644
index 0000000..f44dd10
--- /dev/null
+++ b/platform-paper/src/test/kotlin/dev/m1sk9/lunaticChat/paper/converter/CacheDataTest.kt
@@ -0,0 +1,31 @@
+package dev.m1sk9.lunaticChat.paper.converter
+
+import kotlinx.serialization.json.Json
+import kotlin.test.Test
+import kotlin.test.assertEquals
+
+class CacheDataTest {
+    private val json = Json
+
+    @Test
+    fun `CacheData should store version and entries`() {
+        val data = CacheData(version = "1.0", entries = mapOf("hello" to "こんにちは"))
+        assertEquals("1.0", data.version)
+        assertEquals("こんにちは", data.entries["hello"])
+    }
+
+    @Test
+    fun `CacheData serialization round-trip should preserve all fields`() {
+        val original =
+            CacheData(
+                version = "2.0",
+                entries = mapOf("hello" to "こんにちは", "world" to "世界"),
+            )
+
+        val serialized = json.encodeToString(CacheData.serializer(), original)
+        val deserialized = json.decodeFromString(CacheData.serializer(), serialized)
+
+        assertEquals(original.version, deserialized.version)
+        assertEquals(original.entries, deserialized.entries)
+    }
+}
diff --git a/engine/src/test/kotlin/dev/m1sk9/lunaticChat/engine/converter/KanaConverterTest.kt b/platform-paper/src/test/kotlin/dev/m1sk9/lunaticChat/paper/converter/KanaConverterTest.kt
index 5ba7f0e..798772d 100644
--- a/engine/src/test/kotlin/dev/m1sk9/lunaticChat/engine/converter/KanaConverterTest.kt
+++ b/platform-paper/src/test/kotlin/dev/m1sk9/lunaticChat/paper/converter/KanaConverterTest.kt
@@ -1,4 +1,4 @@
-package dev.m1sk9.lunaticChat.engine.converter
+package dev.m1sk9.lunaticChat.paper.converter
 
 import kotlin.test.Test
 import kotlin.test.assertEquals
diff --git a/platform-paper/src/test/kotlin/dev/m1sk9/lunaticChat/paper/converter/RomanjiConverterTest.kt b/platform-paper/src/test/kotlin/dev/m1sk9/lunaticChat/paper/converter/RomanjiConverterTest.kt
index eba2c54..c8fe680 100644
--- a/platform-paper/src/test/kotlin/dev/m1sk9/lunaticChat/paper/converter/RomanjiConverterTest.kt
+++ b/platform-paper/src/test/kotlin/dev/m1sk9/lunaticChat/paper/converter/RomanjiConverterTest.kt
@@ -1,7 +1,7 @@
 package dev.m1sk9.lunaticChat.paper.converter
 
-import dev.m1sk9.lunaticChat.engine.converter.GoogleIMEClient
 import dev.m1sk9.lunaticChat.paper.TestUtils
+import dev.m1sk9.lunaticChat.paper.converter.GoogleIMEClient
 import io.mockk.coEvery
 import io.mockk.coVerify
 import io.mockk.every
diff --git a/platform-velocity/build.gradle.kts b/platform-velocity/build.gradle.kts
index 65bd27f..9f35fae 100644
--- a/platform-velocity/build.gradle.kts
+++ b/platform-velocity/build.gradle.kts
@@ -13,7 +13,7 @@ repositories {
 }
 
 dependencies {
-    // Engine module (provides serialization, coroutines, ktor)
+    // Engine module (provides serialization)
     api(project(":engine"))
 
     // Velocity-specific dependencies
diff --git a/platform-velocity/src/main/kotlin/dev/m1sk9/lunaticChat/velocity/messaging/CrossServerDirectMessageRelay.kt b/platform-velocity/src/main/kotlin/dev/m1sk9/lunaticChat/velocity/messaging/CrossServerDirectMessageRelay.kt
index f9cc52d..70ca525 100644
--- a/platform-velocity/src/main/kotlin/dev/m1sk9/lunaticChat/velocity/messaging/CrossServerDirectMessageRelay.kt
+++ b/platform-velocity/src/main/kotlin/dev/m1sk9/lunaticChat/velocity/messaging/CrossServerDirectMessageRelay.kt
@@ -78,7 +78,7 @@ class CrossServerDirectMessageRelay(
     private fun sendError(
         sourceServer: RegisteredServer,
         message: PluginMessage.DirectMessageRelay,
-        reason: String,
+        reason: PluginMessage.DirectMessageError.Reason,
     ) {
         val error =
             PluginMessage.DirectMessageError(
diff --git a/website/src/docs/configuration.md b/website/src/docs/configuration.md
index 859b617..78430f3 100644
--- a/website/src/docs/configuration.md
+++ b/website/src/docs/configuration.md
@@ -32,7 +32,6 @@ LunaticChat's configuration is managed in `plugins/LunaticChat/config.yml`. A de
 | `cache.saveIntervalSeconds` | Int | `300` | Interval (in seconds) for saving cache to disk |
 | `cache.filePath` | String | `"conversion_cache.json"` | Path to the cache file |
 | `api.timeout` | Long | `3000` | API request timeout (in milliseconds) |
-| `api.retryAttempts` | Int | `2` | Number of retries on API request failure |
 
 ### Channel Chat (`features.channelChat`)
 
diff --git a/website/src/docs/features/japanese-conversion.md b/website/src/docs/features/japanese-conversion.md
index 3bcd52b..ec1df1b 100644
--- a/website/src/docs/features/japanese-conversion.md
+++ b/website/src/docs/features/japanese-conversion.md
@@ -57,6 +57,5 @@ Settings related to the connection to the Google IME API.
 | Setting Key | Default | Description |
 |-------------|---------|-------------|
 | `api.timeout` | `3000` | Request timeout (milliseconds) |
-| `api.retryAttempts` | `2` | Number of retry attempts on failure |
 
 If the API times out or fails, the message is sent in hiragana as-is.
diff --git a/website/src/ja/docs/configuration.md b/website/src/ja/docs/configuration.md
index 60a79c7..c2c8c12 100644
--- a/website/src/ja/docs/configuration.md
+++ b/website/src/ja/docs/configuration.md
@@ -32,7 +32,6 @@ LunaticChat の設定は `plugins/LunaticChat/config.yml` で管理されます�
 | `cache.saveIntervalSeconds` | Int | `300` | キャッシュのディスク保存間隔(秒) |
 | `cache.filePath` | String | `"conversion_cache.json"` | キャッシュファイルのパス |
 | `api.timeout` | Long | `3000` | API リクエストのタイムアウト(ミリ秒) |
-| `api.retryAttempts` | Int | `2` | API リクエスト失敗時のリトライ回数 |
 
 ### チャンネルチャット (`features.channelChat`)
 
diff --git a/website/src/ja/docs/features/japanese-conversion.md b/website/src/ja/docs/features/japanese-conversion.md
index e5e751b..b94542e 100644
--- a/website/src/ja/docs/features/japanese-conversion.md
+++ b/website/src/ja/docs/features/japanese-conversion.md
@@ -57,6 +57,5 @@ Google IME API への接続に関する設定です．
 | 設定キー | デフォルト | 説明 |
 |----------|-----------|------|
 | `api.timeout` | `3000` | リクエストタイムアウト (ミリ秒) |
-| `api.retryAttempts` | `2` | 失敗時のリトライ回数 |
 
 API がタイムアウトまたは失敗した場合，ひらがなのまま送信されます．