diff --git a/.agents/rules/coding-guide.md b/.agents/rules/coding-guide.md
new file mode 100644
index 00000000..557ad7a9
--- /dev/null
+++ b/.agents/rules/coding-guide.md
@@ -0,0 +1,5 @@
+---
+trigger: always_on
+---
+
+Make sure `./gradlew build` compiles before you say you're done.
\ No newline at end of file
diff --git a/planet/src/main/kotlin/ext/Spring.kt b/planet/src/main/kotlin/ext/Spring.kt
index 3048ba62..cd53d667 100644
--- a/planet/src/main/kotlin/ext/Spring.kt
+++ b/planet/src/main/kotlin/ext/Spring.kt
@@ -32,10 +32,7 @@ fun HttpServletResponse.details() = mapOf(
 
 // HTTP
 operator fun HttpStatus.invoke(message: String? = null): Nothing = throw ApiException(value(), message ?: this.reasonPhrase)
-operator fun Int.minus(message: String): Nothing {
-    ApiException.log.info("> Error $this: $message")
-    throw ApiException(this, message)
-}
+
 fun <R> parsing(block: () -> R) = try { block() }
 catch (e: ApiException) { throw e }
 catch (e: Exception) { 400 - e.message.toString() }
diff --git a/planet/src/main/kotlin/icu/samnyan/aqua/net/utils/ErrorResponse.kt b/planet/src/main/kotlin/icu/samnyan/aqua/net/utils/ErrorResponse.kt
index 7c87b979..b421b5d2 100644
--- a/planet/src/main/kotlin/icu/samnyan/aqua/net/utils/ErrorResponse.kt
+++ b/planet/src/main/kotlin/icu/samnyan/aqua/net/utils/ErrorResponse.kt
@@ -1,29 +1,21 @@
-package icu.samnyan.aqua.net.utils
-
-import ext.Str
-import org.slf4j.LoggerFactory
-import org.springframework.http.ResponseEntity
-import org.springframework.web.bind.annotation.ControllerAdvice
-import org.springframework.web.bind.annotation.ExceptionHandler
-
-
-val SUCCESS = ResponseEntity.ok().body(mapOf("status" to "ok"))
-
-class ApiException(val code: Int, message: Str) : RuntimeException(message) {
-    companion object {
-        val log = LoggerFactory.getLogger(ApiException::class.java)
-    }
-
-    fun resp() = ResponseEntity.status(code).body(message.toString())
-}
-
-fun Exception.simpleDescribe(): String = if (this is ApiException) "E${code}" else javaClass.simpleName
-
-@ControllerAdvice(basePackages = ["icu.samnyan"])
-class GlobalExceptionHandler {
-    @ExceptionHandler(ApiException::class)
-    fun handleCustomApiException(e: ApiException): ResponseEntity<String> {
-        // On error, return the error code and message
-        return e.resp()
-    }
+package icu.samnyan.aqua.net.utils
+
+import org.springframework.http.ResponseEntity
+import org.springframework.web.bind.annotation.ControllerAdvice
+import org.springframework.web.bind.annotation.ExceptionHandler
+
+
+val SUCCESS: ResponseEntity<Map<String, String>> = ResponseEntity.ok().body(mapOf("status" to "ok"))
+
+fun ApiException.resp(): ResponseEntity<String> = ResponseEntity.status(code).body(message.toString())
+
+fun Exception.simpleDescribe(): String = if (this is ApiException) "E${code}" else javaClass.simpleName
+
+@ControllerAdvice(basePackages = ["icu.samnyan"])
+class GlobalExceptionHandler {
+    @ExceptionHandler(ApiException::class)
+    fun handleCustomApiException(e: ApiException): ResponseEntity<String> {
+        // On error, return the error code and message
+        return e.resp()
+    }
 }
\ No newline at end of file
diff --git a/planet/src/test/kotlin/ext/TestExt.kt b/planet/src/test/kotlin/ext/TestExt.kt
index aba1fc92..57847332 100644
--- a/planet/src/test/kotlin/ext/TestExt.kt
+++ b/planet/src/test/kotlin/ext/TestExt.kt
@@ -4,6 +4,8 @@ import io.ktor.client.request.*
 import io.ktor.client.statement.*
 import kotlin.random.Random
 import kotlin.random.nextInt
+import ext.ensureEndingSlash
+import ext.jsonMap
 
 const val BOARD_ID = "ACAE-01A99999999"
 const val FULL_CLIENT_ID = "A123-45678909999"
diff --git a/shared/build.gradle.kts b/shared/build.gradle.kts
index 97323024..d3f80072 100644
--- a/shared/build.gradle.kts
+++ b/shared/build.gradle.kts
@@ -9,4 +9,11 @@ dependencies {
     api("jakarta.servlet:jakarta.servlet-api:6.0.0")
     api("com.fasterxml.jackson.core:jackson-annotations:2.17.0")
     api("com.fasterxml.jackson.core:jackson-databind:2.17.0")
+    api("com.fasterxml.jackson.module:jackson-module-kotlin:2.17.0")
+
+    // Core libraries
+    api("org.slf4j:slf4j-api:2.0.12")
+    api("org.jetbrains.kotlinx:kotlinx-serialization-json:1.6.3")
+    api("org.jetbrains.kotlinx:kotlinx-coroutines-core:1.8.0")
+    api("org.jetbrains.kotlin:kotlin-reflect:2.1.10")
 }
diff --git a/planet/src/main/kotlin/ext/Ext.kt b/shared/src/main/kotlin/ext/Ext.kt
similarity index 94%
rename from planet/src/main/kotlin/ext/Ext.kt
rename to shared/src/main/kotlin/ext/Ext.kt
index fe233fa2..a7542455 100644
--- a/planet/src/main/kotlin/ext/Ext.kt
+++ b/shared/src/main/kotlin/ext/Ext.kt
@@ -2,6 +2,7 @@
 
 package ext
 
+import icu.samnyan.aqua.net.utils.ApiException
 import kotlinx.coroutines.Dispatchers
 import kotlinx.coroutines.withContext
 import org.slf4j.LoggerFactory
@@ -37,12 +38,12 @@ val emailRegex = "^(?=.{1,64}@)[\\p{L}0-9_-]+(\\.[\\p{L}0-9_-]+)*@[^-][\\p{L}0-9
 fun Str.isValidEmail(): Bool = emailRegex.matches(this)
 
 // Class resource
-object Ext { val log = logger() }
+object Ext
 fun res(name: Str) = Ext::class.java.getResourceAsStream(name)
 fun resStr(name: Str) = res(name)?.reader()?.readText()
 inline fun <reified T> resJson(name: Str, warn: Boolean = true) = resStr(name)?.let {
     JSON.decodeFromString<T>(it)
-} ?: run { if (warn) Ext.log.warn("Resource $name is not found"); null }
+} ?: run { if (warn) ApiException.log.warn("Resource $name is not found"); null }
 
 // Encodings
 fun Long.toHex(len: Int = 16): Str = "0x${this.toString(len).padStart(len, '0').uppercase()}"
@@ -56,6 +57,10 @@ fun Any.long() = when (this) {
     is String -> toLong()
     else -> 400 - "Invalid number: $this"
 }
+operator fun Int.minus(message: String): Nothing {
+    ApiException.log.info("> Error $this: $message")
+    throw ApiException(this, message)
+}
 fun Any.uint32() = long() and 0xFFFFFFFF
 fun Any.int() = long().toInt()
 val Any.long get() = long()
@@ -120,17 +125,19 @@ val Str.some get() = ifBlank { null }
 val ByteArray.hexStr get() = toHexString()
 operator fun StringBuilder.plusAssign(other: String) { this.append(other) }
 
-// Coroutine
-suspend fun <T> async(block: suspend kotlinx.coroutines.CoroutineScope.() -> T): T = withContext(Dispatchers.IO) { block() }
+// Coroutine-lite
 fun <T> thread(block: () -> T) = Thread { block() }.apply { start() }
 fun <T> Lock.maybeLock(block: () -> T) = if (tryLock()) try { block() } finally { unlock() } else null
 
+// Coroutine
+suspend fun <T> async(block: suspend kotlinx.coroutines.CoroutineScope.() -> T): T = withContext(Dispatchers.IO) { block() }
+
 // Paths
 fun path(part1: Str, vararg parts: Str) = Path.of(part1, *parts)
 fun Str.path() = Path.of(this)
 operator fun Path.div(part: Str) = resolve(part)
 operator fun File.div(fileName: Str) = File(this, fileName)
-fun Str.ensureEndingSlash() = if (endsWith('/')) this else "$this/"
+fun String.ensureEndingSlash() = if (endsWith('/')) this else "$this/"
 fun Str.ensureNoEndingSlash() = if (endsWith('/')) dropLast(1) else this
 
 fun <T: Any> T.logger() = LoggerFactory.getLogger(this::class.java)
diff --git a/planet/src/main/kotlin/ext/Http.kt b/shared/src/main/kotlin/ext/Http.kt
similarity index 100%
rename from planet/src/main/kotlin/ext/Http.kt
rename to shared/src/main/kotlin/ext/Http.kt
diff --git a/planet/src/main/kotlin/ext/Jackson.kt b/shared/src/main/kotlin/ext/Jackson.kt
similarity index 88%
rename from planet/src/main/kotlin/ext/Jackson.kt
rename to shared/src/main/kotlin/ext/Jackson.kt
index 8ef2c452..99f69c4a 100644
--- a/planet/src/main/kotlin/ext/Jackson.kt
+++ b/shared/src/main/kotlin/ext/Jackson.kt
@@ -56,7 +56,7 @@ catch (e: Exception) {
     throw e
 }
 
-fun String.jsonMap(): Map<String, Any?> = json() ?: emptyMap()
-fun String.jsonArray(): List<Map<String, Any?>> = json() ?: emptyList()
-fun String.jsonMaybeMap(): Map<String, Any?>? = json()
-fun String.jsonMaybeArray(): List<Map<String, Any?>>? = json()
+fun String.jsonMap(): Map<String, Any?> = json<Map<String, Any?>>() ?: emptyMap()
+fun String.jsonArray(): List<Map<String, Any?>> = json<List<Map<String, Any?>>>() ?: emptyList()
+fun String.jsonMaybeMap(): Map<String, Any?>? = json<Map<String, Any?>>()
+fun String.jsonMaybeArray(): List<Map<String, Any?>>? = json<List<Map<String, Any?>>>()
diff --git a/planet/src/main/kotlin/ext/Json.kt b/shared/src/main/kotlin/ext/Json.kt
similarity index 100%
rename from planet/src/main/kotlin/ext/Json.kt
rename to shared/src/main/kotlin/ext/Json.kt
diff --git a/planet/src/main/kotlin/ext/Reflect.kt b/shared/src/main/kotlin/ext/Reflect.kt
similarity index 100%
rename from planet/src/main/kotlin/ext/Reflect.kt
rename to shared/src/main/kotlin/ext/Reflect.kt
diff --git a/planet/src/main/kotlin/ext/Time.kt b/shared/src/main/kotlin/ext/Time.kt
similarity index 100%
rename from planet/src/main/kotlin/ext/Time.kt
rename to shared/src/main/kotlin/ext/Time.kt
diff --git a/shared/src/main/kotlin/icu/samnyan/aqua/net/utils/ApiException.kt b/shared/src/main/kotlin/icu/samnyan/aqua/net/utils/ApiException.kt
new file mode 100644
index 00000000..891ea584
--- /dev/null
+++ b/shared/src/main/kotlin/icu/samnyan/aqua/net/utils/ApiException.kt
@@ -0,0 +1,10 @@
+package icu.samnyan.aqua.net.utils
+
+import ext.Str
+import org.slf4j.LoggerFactory
+
+class ApiException(val code: Int, message: Str) : RuntimeException(message) {
+    companion object {
+        val log = LoggerFactory.getLogger(ApiException::class.java)
+    }
+}
diff --git a/planet/src/main/kotlin/icu/samnyan/aqua/sega/util/ZLib.kt b/shared/src/main/kotlin/icu/samnyan/aqua/sega/util/ZLib.kt
similarity index 100%
rename from planet/src/main/kotlin/icu/samnyan/aqua/sega/util/ZLib.kt
rename to shared/src/main/kotlin/icu/samnyan/aqua/sega/util/ZLib.kt