diff --git a/.gitignore b/.gitignore
new file mode 100644
index 0000000..6ea8a8c
--- /dev/null
+++ b/.gitignore
@@ -0,0 +1,8 @@
+.gradle/
+build/
+.idea/
+*.iml
+.kotlin/
+.kotlinbin/
+local.properties
+.cortexkit/
\ No newline at end of file
diff --git a/api/build.gradle.kts b/api/build.gradle.kts
new file mode 100644
index 0000000..56cbd68
--- /dev/null
+++ b/api/build.gradle.kts
@@ -0,0 +1,28 @@
+plugins {
+    alias(libs.plugins.kotlin.multiplatform)
+    alias(libs.plugins.kotlin.serialization)
+}
+
+kotlin {
+    jvmToolchain(21)
+    jvm()
+    macosX64()
+    macosArm64()
+    iosX64()
+    iosArm64()
+    iosSimulatorArm64()
+    linuxX64()
+    linuxArm64()
+    mingwX64()
+
+    sourceSets {
+        commonMain.dependencies {
+            api(libs.kotlinx.coroutines.core)
+            api(libs.kotlinx.serialization.json)
+        }
+        commonTest.dependencies {
+            implementation(kotlin("test"))
+            implementation(libs.kotlinx.coroutines.test)
+        }
+    }
+}
\ No newline at end of file
diff --git a/api/src/commonMain/kotlin/pw/binom/agui/api/agent/AbstractAgent.kt b/api/src/commonMain/kotlin/pw/binom/agui/api/agent/AbstractAgent.kt
new file mode 100644
index 0000000..f450170
--- /dev/null
+++ b/api/src/commonMain/kotlin/pw/binom/agui/api/agent/AbstractAgent.kt
@@ -0,0 +1,51 @@
+package pw.binom.agui.api.agent
+
+import pw.binom.agui.api.event.BaseEvent
+import pw.binom.agui.api.message.Message
+import pw.binom.agui.api.run.RunAgentInput
+import pw.binom.agui.api.run.RunAgentParameters
+import pw.binom.agui.api.run.randomRunId
+import pw.binom.agui.api.run.toParameters
+import pw.binom.agui.api.run.toRunAgentInput
+import pw.binom.agui.api.state.State
+import pw.binom.agui.api.state.mutableState
+import kotlinx.coroutines.flow.Flow
+
+/**
+ * Convenience base class for building a stateful, local [Agent].
+ *
+ * It owns the agent's [agentId], [threadId], a mutable [state] and its own [messages],
+ * and adapts the wire-level [run] to the higher-level [runAgent] taking only
+ * [RunAgentParameters].
+ *
+ * Subclasses override [runAgent]; typically they call [toRunAgentInput] to obtain the full
+ * [RunAgentInput] for the run and return a flow of events.
+ */
+public abstract class AbstractAgent(
+    public val agentId: String,
+    public val threadId: String,
+) : Agent {
+
+    /** The agent's mutable state, exposed as an immutable [State] view. */
+    public val state: State = mutableState()
+
+    /** The agent's own running message list, merged into the input if none is supplied. */
+    public val messages: MutableList<Message> = mutableListOf()
+
+    /** Subclasses produce the event stream for a single run. */
+    public abstract fun runAgent(parameters: RunAgentParameters): Flow<BaseEvent>
+
+    /** Adapts [input] to [runAgent], binding the run to *this* agent's identity and state. */
+    final override fun run(input: RunAgentInput): Flow<BaseEvent> =
+        runAgent(input.toParameters())
+
+    /** Builds a [RunAgentInput] from [parameters], this agent's [threadId] and [state]. */
+    public fun toRunAgentInput(
+        parameters: RunAgentParameters,
+        state: State = this.state,
+    ): RunAgentInput = parameters.toRunAgentInput(
+        threadId = threadId,
+        runId = parameters.runId ?: randomRunId(),
+        state = state,
+    )
+}
\ No newline at end of file
diff --git a/api/src/commonMain/kotlin/pw/binom/agui/api/agent/Agent.kt b/api/src/commonMain/kotlin/pw/binom/agui/api/agent/Agent.kt
new file mode 100644
index 0000000..d0e597b
--- /dev/null
+++ b/api/src/commonMain/kotlin/pw/binom/agui/api/agent/Agent.kt
@@ -0,0 +1,21 @@
+package pw.binom.agui.api.agent
+
+import pw.binom.agui.api.event.BaseEvent
+import pw.binom.agui.api.run.RunAgentInput
+import kotlinx.coroutines.flow.Flow
+
+/**
+ * The core AG-UI abstraction: an entity that, given a complete [RunAgentInput], produces the
+ * agent's stream of [BaseEvent]s.
+ *
+ * This is the network-agnostic heart of the protocol. A concrete [Agent] can be:
+ *
+ *  - remote — [pw.binom.agui.client.HttpAgent] streams events over SSE;
+ *  - local — a real agent implementation;
+ *  - composed/decorated — logging, auth, retry, observability wrappers.
+ */
+public fun interface Agent {
+
+    /** Runs the agent for [input] and returns the resulting event stream. */
+    public fun run(input: RunAgentInput): Flow<BaseEvent>
+}
\ No newline at end of file
diff --git a/api/src/commonMain/kotlin/pw/binom/agui/api/agent/AgentSubscriber.kt b/api/src/commonMain/kotlin/pw/binom/agui/api/agent/AgentSubscriber.kt
new file mode 100644
index 0000000..b575c64
--- /dev/null
+++ b/api/src/commonMain/kotlin/pw/binom/agui/api/agent/AgentSubscriber.kt
@@ -0,0 +1,85 @@
+package pw.binom.agui.api.agent
+
+import pw.binom.agui.api.event.BaseEvent
+import pw.binom.agui.api.event.CustomEvent
+import pw.binom.agui.api.event.MessagesSnapshotEvent
+import pw.binom.agui.api.event.RawEvent
+import pw.binom.agui.api.event.RunErrorEvent
+import pw.binom.agui.api.event.RunFinishedEvent
+import pw.binom.agui.api.event.RunStartedEvent
+import pw.binom.agui.api.event.StateDeltaEvent
+import pw.binom.agui.api.event.StateSnapshotEvent
+import pw.binom.agui.api.event.StepFinishedEvent
+import pw.binom.agui.api.event.StepStartedEvent
+import pw.binom.agui.api.event.TextMessageContentEvent
+import pw.binom.agui.api.event.TextMessageEndEvent
+import pw.binom.agui.api.event.TextMessageStartEvent
+import pw.binom.agui.api.event.ToolCallArgsEvent
+import pw.binom.agui.api.event.ToolCallEndEvent
+import pw.binom.agui.api.event.ToolCallResultEvent
+import pw.binom.agui.api.event.ToolCallStartEvent
+
+/**
+ * Observer for a stream of [BaseEvent]s.
+ *
+ * Every method is a no-op by default, so implementations only override the events
+ * they care about. Dispatch a [BaseEvent] to this subscriber with
+ * [EventDispatcher.dispatch], or collect a whole flow with `dispatchTo`.
+ */
+public interface AgentSubscriber {
+
+    /** Called for every event, before the type-specific callback. */
+    public fun onEvent(event: BaseEvent) {
+    }
+
+    public fun onRunStarted(event: RunStartedEvent) {
+    }
+
+    public fun onRunFinished(event: RunFinishedEvent) {
+    }
+
+    public fun onRunError(event: RunErrorEvent) {
+    }
+
+    public fun onStepStarted(event: StepStartedEvent) {
+    }
+
+    public fun onStepFinished(event: StepFinishedEvent) {
+    }
+
+    public fun onTextMessageStart(event: TextMessageStartEvent) {
+    }
+
+    public fun onTextMessageContent(event: TextMessageContentEvent) {
+    }
+
+    public fun onTextMessageEnd(event: TextMessageEndEvent) {
+    }
+
+    public fun onToolCallStart(event: ToolCallStartEvent) {
+    }
+
+    public fun onToolCallArgs(event: ToolCallArgsEvent) {
+    }
+
+    public fun onToolCallEnd(event: ToolCallEndEvent) {
+    }
+
+    public fun onToolCallResult(event: ToolCallResultEvent) {
+    }
+
+    public fun onStateSnapshot(event: StateSnapshotEvent) {
+    }
+
+    public fun onStateDelta(event: StateDeltaEvent) {
+    }
+
+    public fun onMessagesSnapshot(event: MessagesSnapshotEvent) {
+    }
+
+    public fun onRaw(event: RawEvent) {
+    }
+
+    public fun onCustom(event: CustomEvent) {
+    }
+}
\ No newline at end of file
diff --git a/api/src/commonMain/kotlin/pw/binom/agui/api/agent/EventDispatcher.kt b/api/src/commonMain/kotlin/pw/binom/agui/api/agent/EventDispatcher.kt
new file mode 100644
index 0000000..064e492
--- /dev/null
+++ b/api/src/commonMain/kotlin/pw/binom/agui/api/agent/EventDispatcher.kt
@@ -0,0 +1,56 @@
+package pw.binom.agui.api.agent
+
+import pw.binom.agui.api.event.BaseEvent
+import pw.binom.agui.api.event.CustomEvent
+import pw.binom.agui.api.event.MessagesSnapshotEvent
+import pw.binom.agui.api.event.RawEvent
+import pw.binom.agui.api.event.RunErrorEvent
+import pw.binom.agui.api.event.RunFinishedEvent
+import pw.binom.agui.api.event.RunStartedEvent
+import pw.binom.agui.api.event.StateDeltaEvent
+import pw.binom.agui.api.event.StateSnapshotEvent
+import pw.binom.agui.api.event.StepFinishedEvent
+import pw.binom.agui.api.event.StepStartedEvent
+import pw.binom.agui.api.event.TextMessageContentEvent
+import pw.binom.agui.api.event.TextMessageEndEvent
+import pw.binom.agui.api.event.TextMessageStartEvent
+import pw.binom.agui.api.event.ToolCallArgsEvent
+import pw.binom.agui.api.event.ToolCallEndEvent
+import pw.binom.agui.api.event.ToolCallResultEvent
+import pw.binom.agui.api.event.ToolCallStartEvent
+import kotlinx.coroutines.flow.Flow
+
+/**
+ * Routes each [BaseEvent] to the matching [AgentSubscriber] callback.
+ */
+public object EventDispatcher {
+
+    /** Dispatches a single [event] to [subscriber]: always [AgentSubscriber.onEvent], then the typed callback. */
+    public fun dispatch(event: BaseEvent, subscriber: AgentSubscriber) {
+        subscriber.onEvent(event)
+        when (event) {
+            is RunStartedEvent -> subscriber.onRunStarted(event)
+            is RunFinishedEvent -> subscriber.onRunFinished(event)
+            is RunErrorEvent -> subscriber.onRunError(event)
+            is StepStartedEvent -> subscriber.onStepStarted(event)
+            is StepFinishedEvent -> subscriber.onStepFinished(event)
+            is TextMessageStartEvent -> subscriber.onTextMessageStart(event)
+            is TextMessageContentEvent -> subscriber.onTextMessageContent(event)
+            is TextMessageEndEvent -> subscriber.onTextMessageEnd(event)
+            is ToolCallStartEvent -> subscriber.onToolCallStart(event)
+            is ToolCallArgsEvent -> subscriber.onToolCallArgs(event)
+            is ToolCallEndEvent -> subscriber.onToolCallEnd(event)
+            is ToolCallResultEvent -> subscriber.onToolCallResult(event)
+            is StateSnapshotEvent -> subscriber.onStateSnapshot(event)
+            is StateDeltaEvent -> subscriber.onStateDelta(event)
+            is MessagesSnapshotEvent -> subscriber.onMessagesSnapshot(event)
+            is RawEvent -> subscriber.onRaw(event)
+            is CustomEvent -> subscriber.onCustom(event)
+        }
+    }
+}
+
+/** Collects [this] flow and dispatches each event to [subscriber]. */
+public suspend fun Flow<BaseEvent>.dispatchTo(subscriber: AgentSubscriber) {
+    collect { event -> EventDispatcher.dispatch(event, subscriber) }
+}
\ No newline at end of file
diff --git a/api/src/commonMain/kotlin/pw/binom/agui/api/context/Context.kt b/api/src/commonMain/kotlin/pw/binom/agui/api/context/Context.kt
new file mode 100644
index 0000000..9df3e76
--- /dev/null
+++ b/api/src/commonMain/kotlin/pw/binom/agui/api/context/Context.kt
@@ -0,0 +1,14 @@
+package pw.binom.agui.api.context
+
+import kotlinx.serialization.Serializable
+
+/**
+ * A single piece of context supplied for a run. Mirrors the AG-UI `Context` type.
+ *
+ * [description] is a human-readable label; [value] carries the opaque payload.
+ */
+@Serializable
+public data class Context(
+    val description: String,
+    val value: String,
+)
diff --git a/api/src/commonMain/kotlin/pw/binom/agui/api/event/BaseEvent.kt b/api/src/commonMain/kotlin/pw/binom/agui/api/event/BaseEvent.kt
new file mode 100644
index 0000000..c13e632
--- /dev/null
+++ b/api/src/commonMain/kotlin/pw/binom/agui/api/event/BaseEvent.kt
@@ -0,0 +1,173 @@
+package pw.binom.agui.api.event
+
+import pw.binom.agui.api.message.Message
+import pw.binom.agui.api.message.MessageRole
+import pw.binom.agui.api.state.State
+import kotlinx.serialization.SerialName
+import kotlinx.serialization.Serializable
+import kotlinx.serialization.json.JsonElement
+
+/**
+ * Root of the AG-UI event stream.
+ *
+ * AG-UI is a push protocol: an agent streams [BaseEvent]s to a client. The concrete
+ * subclasses mirror the AG-UI protocol event catalogue and are (de)serialized
+ * polymorphically by the `type` discriminator field.
+ */
+@Serializable
+public sealed interface BaseEvent {
+
+    /** Event creation timestamp in epoch milliseconds, if provided. */
+    public val timestamp: Long?
+}
+
+// region Lifecycle
+
+@Serializable
+@SerialName("RUN_STARTED")
+public data class RunStartedEvent(
+    val threadId: String,
+    val runId: String,
+    override val timestamp: Long? = null,
+) : BaseEvent
+
+@Serializable
+@SerialName("RUN_FINISHED")
+public data class RunFinishedEvent(
+    val threadId: String? = null,
+    val runId: String? = null,
+    override val timestamp: Long? = null,
+) : BaseEvent
+
+@Serializable
+@SerialName("RUN_ERROR")
+public data class RunErrorEvent(
+    val message: String,
+    val code: String? = null,
+    override val timestamp: Long? = null,
+) : BaseEvent
+
+@Serializable
+@SerialName("STEP_STARTED")
+public data class StepStartedEvent(
+    val stepName: String,
+    override val timestamp: Long? = null,
+) : BaseEvent
+
+@Serializable
+@SerialName("STEP_FINISHED")
+public data class StepFinishedEvent(
+    val stepName: String,
+    override val timestamp: Long? = null,
+) : BaseEvent
+
+// endregion
+
+// region Text message
+
+@Serializable
+@SerialName("TEXT_MESSAGE_START")
+public data class TextMessageStartEvent(
+    val messageId: String,
+    val role: MessageRole = MessageRole.ASSISTANT,
+    override val timestamp: Long? = null,
+) : BaseEvent
+
+@Serializable
+@SerialName("TEXT_MESSAGE_CONTENT")
+public data class TextMessageContentEvent(
+    val messageId: String,
+    val delta: String,
+    override val timestamp: Long? = null,
+) : BaseEvent
+
+@Serializable
+@SerialName("TEXT_MESSAGE_END")
+public data class TextMessageEndEvent(
+    val messageId: String,
+    override val timestamp: Long? = null,
+) : BaseEvent
+
+// endregion
+
+// region Tool call
+
+@Serializable
+@SerialName("TOOL_CALL_START")
+public data class ToolCallStartEvent(
+    val toolCallId: String,
+    val toolCallName: String,
+    val parentMessageId: String? = null,
+    override val timestamp: Long? = null,
+) : BaseEvent
+
+@Serializable
+@SerialName("TOOL_CALL_ARGS")
+public data class ToolCallArgsEvent(
+    val toolCallId: String,
+    val delta: String,
+    override val timestamp: Long? = null,
+) : BaseEvent
+
+@Serializable
+@SerialName("TOOL_CALL_END")
+public data class ToolCallEndEvent(
+    val toolCallId: String,
+    override val timestamp: Long? = null,
+) : BaseEvent
+
+@Serializable
+@SerialName("TOOL_CALL_RESULT")
+public data class ToolCallResultEvent(
+    val toolCallId: String,
+    val messageId: String? = null,
+    val role: MessageRole = MessageRole.TOOL,
+    val content: String? = null,
+    override val timestamp: Long? = null,
+) : BaseEvent
+
+// endregion
+
+// region State / messages
+
+@Serializable
+@SerialName("STATE_SNAPSHOT")
+public data class StateSnapshotEvent(
+    val snapshot: State,
+    override val timestamp: Long? = null,
+) : BaseEvent
+
+@Serializable
+@SerialName("STATE_DELTA")
+public data class StateDeltaEvent(
+    val delta: JsonElement,
+    override val timestamp: Long? = null,
+) : BaseEvent
+
+@Serializable
+@SerialName("MESSAGES_SNAPSHOT")
+public data class MessagesSnapshotEvent(
+    val messages: List<Message>,
+    override val timestamp: Long? = null,
+) : BaseEvent
+
+// endregion
+
+// region Special
+
+@Serializable
+@SerialName("RAW")
+public data class RawEvent(
+    val event: JsonElement,
+    override val timestamp: Long? = null,
+) : BaseEvent
+
+@Serializable
+@SerialName("CUSTOM")
+public data class CustomEvent(
+    val name: String,
+    val value: JsonElement? = null,
+    override val timestamp: Long? = null,
+) : BaseEvent
+
+// endregion
diff --git a/api/src/commonMain/kotlin/pw/binom/agui/api/message/Message.kt b/api/src/commonMain/kotlin/pw/binom/agui/api/message/Message.kt
new file mode 100644
index 0000000..eb26df7
--- /dev/null
+++ b/api/src/commonMain/kotlin/pw/binom/agui/api/message/Message.kt
@@ -0,0 +1,48 @@
+package pw.binom.agui.api.message
+
+import kotlinx.serialization.SerialName
+import kotlinx.serialization.Serializable
+
+/**
+ * A message role. Serialized using the AG-UI wire value (e.g. `"assistant"`, `"tool"`).
+ */
+@Serializable
+public enum class MessageRole {
+    @SerialName("developer") DEVELOPER,
+
+    @SerialName("system") SYSTEM,
+
+    @SerialName("assistant") ASSISTANT,
+
+    @SerialName("user") USER,
+
+    @SerialName("tool") TOOL,
+}
+
+/**
+ * A single chat message. Mirrors the AG-UI `Message` type, which is a base message
+ * optionally carrying tool calls (assistant) or a tool result id (tool).
+ */
+@Serializable
+public data class Message(
+    val id: String,
+    val role: MessageRole,
+    val content: String = "",
+    val toolCalls: List<ToolCall> = emptyList(),
+    val toolCallId: String? = null,
+)
+
+/** A tool invocation requested by an assistant message. */
+@Serializable
+public data class ToolCall(
+    val id: String,
+    val type: String = "function",
+    val function: ToolFunction = ToolFunction(),
+)
+
+/** The function part of a [ToolCall]. */
+@Serializable
+public data class ToolFunction(
+    val name: String = "",
+    val arguments: String = "{}",
+)
diff --git a/api/src/commonMain/kotlin/pw/binom/agui/api/run/Run.kt b/api/src/commonMain/kotlin/pw/binom/agui/api/run/Run.kt
new file mode 100644
index 0000000..5f70caa
--- /dev/null
+++ b/api/src/commonMain/kotlin/pw/binom/agui/api/run/Run.kt
@@ -0,0 +1,66 @@
+package pw.binom.agui.api.run
+
+import pw.binom.agui.api.context.Context
+import pw.binom.agui.api.message.Message
+import pw.binom.agui.api.state.State
+import pw.binom.agui.api.tool.Tool
+import kotlinx.serialization.Serializable
+import kotlinx.serialization.json.JsonElement
+import kotlin.random.Random
+
+/**
+ * The complete request payload of an AG-UI run.
+ *
+ * This is exactly what a client POSTs to an agent and what a server receives.
+ */
+@Serializable
+public data class RunAgentInput(
+    val threadId: String,
+    val runId: String,
+    val state: State = emptyMap(),
+    val messages: List<Message> = emptyList(),
+    val tools: List<Tool> = emptyList(),
+    val context: List<Context> = emptyList(),
+    val forwardedProps: Map<String, JsonElement> = emptyMap(),
+)
+
+/**
+ * Parameters a *caller* supplies for a single run, before it is turned into a
+ * [RunAgentInput]. Unlike [RunAgentInput] it carries no thread/identity — the agent fills
+ * those in.
+ */
+public data class RunAgentParameters(
+    val context: List<Context> = emptyList(),
+    val tools: List<Tool> = emptyList(),
+    val messages: List<Message> = emptyList(),
+    val forwardedProps: Map<String, JsonElement> = emptyMap(),
+    val runId: String? = null,
+)
+
+/** Builds a [RunAgentInput] from [parameters] plus an explicit thread id, run id and state. */
+public fun RunAgentParameters.toRunAgentInput(
+    threadId: String,
+    runId: String = this.runId ?: randomRunId(),
+    state: State = emptyMap(),
+): RunAgentInput = RunAgentInput(
+    threadId = threadId,
+    runId = runId,
+    state = state,
+    messages = messages,
+    tools = tools,
+    context = context,
+    forwardedProps = forwardedProps,
+)
+
+/** The inverse of [toRunAgentInput]: projects a [RunAgentInput] back to caller parameters. */
+public fun RunAgentInput.toParameters(): RunAgentParameters = RunAgentParameters(
+    context = context,
+    tools = tools,
+    messages = messages,
+    forwardedProps = forwardedProps,
+    runId = runId,
+)
+
+/** Generates a reasonably-unique run identifier, suitable for the [RunAgentInput.runId]. */
+public fun randomRunId(prefix: String = "run"): String =
+    prefix + "-" + Random.nextLong().toULong().toString(16)
diff --git a/api/src/commonMain/kotlin/pw/binom/agui/api/serialization/AguiJson.kt b/api/src/commonMain/kotlin/pw/binom/agui/api/serialization/AguiJson.kt
new file mode 100644
index 0000000..3cc28d5
--- /dev/null
+++ b/api/src/commonMain/kotlin/pw/binom/agui/api/serialization/AguiJson.kt
@@ -0,0 +1,66 @@
+package pw.binom.agui.api.serialization
+
+import pw.binom.agui.api.event.BaseEvent
+import pw.binom.agui.api.event.CustomEvent
+import pw.binom.agui.api.event.MessagesSnapshotEvent
+import pw.binom.agui.api.event.RawEvent
+import pw.binom.agui.api.event.RunErrorEvent
+import pw.binom.agui.api.event.RunFinishedEvent
+import pw.binom.agui.api.event.RunStartedEvent
+import pw.binom.agui.api.event.StateDeltaEvent
+import pw.binom.agui.api.event.StateSnapshotEvent
+import pw.binom.agui.api.event.StepFinishedEvent
+import pw.binom.agui.api.event.StepStartedEvent
+import pw.binom.agui.api.event.TextMessageContentEvent
+import pw.binom.agui.api.event.TextMessageEndEvent
+import pw.binom.agui.api.event.TextMessageStartEvent
+import pw.binom.agui.api.event.ToolCallArgsEvent
+import pw.binom.agui.api.event.ToolCallEndEvent
+import pw.binom.agui.api.event.ToolCallResultEvent
+import pw.binom.agui.api.event.ToolCallStartEvent
+import kotlinx.serialization.json.Json
+import kotlinx.serialization.modules.SerializersModule
+import kotlinx.serialization.modules.polymorphic
+import kotlinx.serialization.modules.subclass
+
+/**
+ * Serializers module registering every [BaseEvent] subtype for polymorphic
+ * (de)serialization. A `sealed interface` does not auto-register its subtypes,
+ * so they are declared explicitly here.
+ */
+public val AguiEventsSerializersModule: SerializersModule = SerializersModule {
+    polymorphic(BaseEvent::class) {
+        subclass(RunStartedEvent::class, RunStartedEvent.serializer())
+        subclass(RunFinishedEvent::class, RunFinishedEvent.serializer())
+        subclass(RunErrorEvent::class, RunErrorEvent.serializer())
+        subclass(StepStartedEvent::class, StepStartedEvent.serializer())
+        subclass(StepFinishedEvent::class, StepFinishedEvent.serializer())
+        subclass(TextMessageStartEvent::class, TextMessageStartEvent.serializer())
+        subclass(TextMessageContentEvent::class, TextMessageContentEvent.serializer())
+        subclass(TextMessageEndEvent::class, TextMessageEndEvent.serializer())
+        subclass(ToolCallStartEvent::class, ToolCallStartEvent.serializer())
+        subclass(ToolCallArgsEvent::class, ToolCallArgsEvent.serializer())
+        subclass(ToolCallEndEvent::class, ToolCallEndEvent.serializer())
+        subclass(ToolCallResultEvent::class, ToolCallResultEvent.serializer())
+        subclass(StateSnapshotEvent::class, StateSnapshotEvent.serializer())
+        subclass(StateDeltaEvent::class, StateDeltaEvent.serializer())
+        subclass(MessagesSnapshotEvent::class, MessagesSnapshotEvent.serializer())
+        subclass(RawEvent::class, RawEvent.serializer())
+        subclass(CustomEvent::class, CustomEvent.serializer())
+    }
+}
+
+/**
+ * The canonical [Json] configuration used to (de)serialize the AG-UI wire protocol.
+ *
+ * - Polymorphic [BaseEvent]s are (de)serialized by their `type` discriminator
+ *   field, with every subtype registered in [AguiEventsSerializersModule].
+ * - Unknown keys are ignored, so newer protocol versions stay backward compatible.
+ * - Null fields are omitted to keep the wire payload compact.
+ */
+public val AguiJson: Json = Json {
+    serializersModule = AguiEventsSerializersModule
+    classDiscriminator = "type"
+    ignoreUnknownKeys = true
+    explicitNulls = false
+}
diff --git a/api/src/commonMain/kotlin/pw/binom/agui/api/state/State.kt b/api/src/commonMain/kotlin/pw/binom/agui/api/state/State.kt
new file mode 100644
index 0000000..77f4cdd
--- /dev/null
+++ b/api/src/commonMain/kotlin/pw/binom/agui/api/state/State.kt
@@ -0,0 +1,19 @@
+package pw.binom.agui.api.state
+
+import kotlinx.serialization.json.JsonElement
+
+/**
+ * A loosely-typed, platform-agnostic bag of agent state carried in AG-UI
+ * `STATE_SNAPSHOT`/`STATE_DELTA` events and in [pw.binom.agui.api.run.RunAgentInput.state].
+ *
+ * Because the value is a JSON element, it can be any JSON scalar, object or array — the
+ * protocol does not prescribe a concrete schema.
+ */
+public typealias State = Map<String, JsonElement>
+
+/** Mutable form of [State] used while an agent builds up its own state. */
+public typealias MutableState = MutableMap<String, JsonElement>
+
+/** Builds a [MutableState] from the given `key to json` pairs. */
+public fun mutableState(vararg pairs: Pair<String, JsonElement>): MutableState =
+    if (pairs.isEmpty()) linkedMapOf() else linkedMapOf(*pairs)
diff --git a/api/src/commonMain/kotlin/pw/binom/agui/api/tool/Tool.kt b/api/src/commonMain/kotlin/pw/binom/agui/api/tool/Tool.kt
new file mode 100644
index 0000000..afd5f1a
--- /dev/null
+++ b/api/src/commonMain/kotlin/pw/binom/agui/api/tool/Tool.kt
@@ -0,0 +1,17 @@
+package pw.binom.agui.api.tool
+
+import kotlinx.serialization.Serializable
+import kotlinx.serialization.json.JsonObject
+
+/**
+ * A tool the agent can call during a run. Mirrors the AG-UI `Tool` type.
+ *
+ * [parameters] is a JSON Schema object describing the tool's arguments; it is kept as a
+ * [JsonObject] so any schema shape can be carried verbatim.
+ */
+@Serializable
+public data class Tool(
+    val name: String,
+    val description: String = "",
+    val parameters: JsonObject = JsonObject(emptyMap()),
+)
diff --git a/api/src/commonTest/kotlin/pw/binom/agui/api/AgentTest.kt b/api/src/commonTest/kotlin/pw/binom/agui/api/AgentTest.kt
new file mode 100644
index 0000000..15e6087
--- /dev/null
+++ b/api/src/commonTest/kotlin/pw/binom/agui/api/AgentTest.kt
@@ -0,0 +1,91 @@
+package pw.binom.agui.api
+
+import pw.binom.agui.api.agent.AbstractAgent
+import pw.binom.agui.api.agent.AgentSubscriber
+import pw.binom.agui.api.agent.EventDispatcher
+import pw.binom.agui.api.agent.dispatchTo
+import pw.binom.agui.api.context.Context
+import pw.binom.agui.api.event.BaseEvent
+import pw.binom.agui.api.event.CustomEvent
+import pw.binom.agui.api.event.RunStartedEvent
+import pw.binom.agui.api.run.RunAgentInput
+import pw.binom.agui.api.run.RunAgentParameters
+import pw.binom.agui.api.run.randomRunId
+import pw.binom.agui.api.run.toParameters
+import pw.binom.agui.api.run.toRunAgentInput
+import pw.binom.agui.api.tool.Tool
+import kotlinx.coroutines.flow.flowOf
+import kotlinx.coroutines.flow.toList
+import kotlinx.coroutines.test.runTest
+import kotlin.test.Test
+import kotlin.test.assertEquals
+import kotlin.test.assertTrue
+
+class AgentTest {
+
+    @Test
+    fun `RunAgentParameters convert to RunAgentInput and back`() {
+        val params = RunAgentParameters(
+            runId = "r1",
+            context = listOf(Context(description = "c", value = "v")),
+            tools = listOf(Tool(name = "t")),
+        )
+        val input = params.toRunAgentInput(threadId = "t1")
+        assertEquals("t1", input.threadId)
+        assertEquals("r1", input.runId)
+        assertEquals(listOf(Context(description = "c", value = "v")), input.context)
+        assertEquals(params, input.toParameters())
+    }
+
+    @Test
+    fun `randomRunId is prefixed and non-empty`() {
+        val id = randomRunId()
+        val (prefix, rest) = id.split('-', limit = 2)
+        assertEquals("run", prefix)
+        assertTrue(rest.isNotEmpty(), "id should have a suffix, got: $id")
+    }
+
+    @Test
+    fun `EventDispatcher routes to the matching subscriber callback`() = runTest {
+        val seen = mutableListOf<String>()
+        val sub = object : AgentSubscriber {
+            override fun onRunStarted(event: RunStartedEvent) {
+                seen += "started"
+            }
+
+            override fun onCustom(event: CustomEvent) {
+                seen += "custom"
+            }
+        }
+        flowOf<BaseEvent>(
+            RunStartedEvent(threadId = "t1", runId = "r1"),
+            CustomEvent(name = "x"),
+            RunStartedEvent(threadId = "t1", runId = "r1"),
+        ).dispatchTo(sub)
+        assertEquals(listOf("started", "custom", "started"), seen)
+    }
+
+    @Test
+    fun `onEvent is called for every dispatched event`() {
+        var count = 0
+        val sub = object : AgentSubscriber {
+            override fun onEvent(event: BaseEvent) {
+                count++
+            }
+        }
+        EventDispatcher.dispatch(RunStartedEvent(threadId = "t1", runId = "r1"), sub)
+        EventDispatcher.dispatch(CustomEvent(name = "x"), sub)
+        assertEquals(2, count)
+    }
+
+    @Test
+    fun `AbstractAgent binds a run to its own identity`() = runTest {
+        val agent = object : AbstractAgent(agentId = "calculator", threadId = "thread-1") {
+            override fun runAgent(parameters: RunAgentParameters) = flowOf(
+                RunStartedEvent(threadId = threadId, runId = parameters.runId ?: "?"),
+            )
+        }
+        val events = agent.run(RunAgentInput(threadId = "other-thread", runId = "r9")).toList()
+        assertEquals(RunStartedEvent(threadId = "thread-1", runId = "r9"), events.single())
+    }
+}
\ No newline at end of file
diff --git a/api/src/commonTest/kotlin/pw/binom/agui/api/EventSerializationTest.kt b/api/src/commonTest/kotlin/pw/binom/agui/api/EventSerializationTest.kt
new file mode 100644
index 0000000..d52e6eb
--- /dev/null
+++ b/api/src/commonTest/kotlin/pw/binom/agui/api/EventSerializationTest.kt
@@ -0,0 +1,87 @@
+package pw.binom.agui.api
+
+import pw.binom.agui.api.event.BaseEvent
+import pw.binom.agui.api.event.CustomEvent
+import pw.binom.agui.api.event.MessagesSnapshotEvent
+import pw.binom.agui.api.event.RawEvent
+import pw.binom.agui.api.event.RunErrorEvent
+import pw.binom.agui.api.event.RunFinishedEvent
+import pw.binom.agui.api.event.RunStartedEvent
+import pw.binom.agui.api.event.StateDeltaEvent
+import pw.binom.agui.api.event.StateSnapshotEvent
+import pw.binom.agui.api.event.StepFinishedEvent
+import pw.binom.agui.api.event.StepStartedEvent
+import pw.binom.agui.api.event.TextMessageContentEvent
+import pw.binom.agui.api.event.TextMessageEndEvent
+import pw.binom.agui.api.event.TextMessageStartEvent
+import pw.binom.agui.api.event.ToolCallArgsEvent
+import pw.binom.agui.api.event.ToolCallEndEvent
+import pw.binom.agui.api.event.ToolCallResultEvent
+import pw.binom.agui.api.event.ToolCallStartEvent
+import pw.binom.agui.api.message.Message
+import pw.binom.agui.api.message.MessageRole
+import pw.binom.agui.api.serialization.AguiJson
+import pw.binom.agui.api.state.mutableState
+import kotlinx.serialization.decodeFromString
+import kotlinx.serialization.encodeToString
+import kotlinx.serialization.json.JsonPrimitive
+import kotlinx.serialization.json.buildJsonArray
+import kotlinx.serialization.json.buildJsonObject
+import kotlinx.serialization.json.put
+import kotlin.test.Test
+import kotlin.test.assertEquals
+import kotlin.test.assertTrue
+
+class EventSerializationTest {
+
+    private val events: List<BaseEvent> = listOf(
+        RunStartedEvent(threadId = "t1", runId = "r1", timestamp = 1L),
+        RunFinishedEvent(threadId = "t1", runId = "r1"),
+        RunErrorEvent(message = "boom", code = "E1"),
+        StepStartedEvent(stepName = "step1"),
+        StepFinishedEvent(stepName = "step1"),
+        TextMessageStartEvent(messageId = "m1", role = MessageRole.USER),
+        TextMessageContentEvent(messageId = "m1", delta = "hello"),
+        TextMessageEndEvent(messageId = "m1"),
+        ToolCallStartEvent(toolCallId = "tc1", toolCallName = "getWeather", parentMessageId = "m1"),
+        ToolCallArgsEvent(toolCallId = "tc1", delta = """{"city":""""),
+        ToolCallEndEvent(toolCallId = "tc1"),
+        ToolCallResultEvent(toolCallId = "tc1", messageId = "r1", content = "20C"),
+        StateSnapshotEvent(snapshot = mutableState("a" to JsonPrimitive(1))),
+        StateDeltaEvent(delta = buildJsonObject { put("a", 2) }),
+        MessagesSnapshotEvent(messages = listOf(Message(id = "m0", role = MessageRole.ASSISTANT, content = "hi"))),
+        RawEvent(event = buildJsonObject { put("anything", true) }),
+        CustomEvent(name = "my.custom", value = buildJsonArray { add(JsonPrimitive("x")) }),
+    )
+
+    @Test
+    fun `every event round-trips through the wire JSON`() {
+        for (event in events) {
+            val json = AguiJson.encodeToString<BaseEvent>(event)
+            val decoded = AguiJson.decodeFromString<BaseEvent>(json)
+            assertEquals(event, decoded, "round-trip failed for $event")
+        }
+    }
+
+    @Test
+    fun `events are discriminated by their AG-UI type name`() {
+        val json = AguiJson.encodeToString<BaseEvent>(RunStartedEvent(threadId = "t1", runId = "r1"))
+        assertTrue(json.contains("\"type\":\"RUN_STARTED\""), json)
+        assertTrue(json.contains("\"threadId\":\"t1\""), json)
+        assertTrue(json.contains("\"runId\":\"r1\""), json)
+    }
+
+    @Test
+    fun `an AG-UI wire event decodes with defaults applied`() {
+        val wire = """{"type":"TEXT_MESSAGE_START","messageId":"m1"}"""
+        val event = AguiJson.decodeFromString<BaseEvent>(wire)
+        assertEquals(TextMessageStartEvent(messageId = "m1"), event)
+    }
+
+    @Test
+    fun `unknown fields are ignored for forward compatibility`() {
+        val wire = """{"type":"RUN_ERROR","message":"boom","failureDetails":{}}"""
+        val event = AguiJson.decodeFromString<BaseEvent>(wire)
+        assertEquals(RunErrorEvent(message = "boom"), event)
+    }
+}
\ No newline at end of file
diff --git a/build.gradle.kts b/build.gradle.kts
new file mode 100644
index 0000000..886c1ef
--- /dev/null
+++ b/build.gradle.kts
@@ -0,0 +1,9 @@
+plugins {
+    alias(libs.plugins.kotlin.multiplatform) apply false
+    alias(libs.plugins.kotlin.serialization) apply false
+}
+
+allprojects {
+    group = "pw.binom.agui"
+    version = "0.1.0-SNAPSHOT"
+}
\ No newline at end of file
diff --git a/client/build.gradle.kts b/client/build.gradle.kts
new file mode 100644
index 0000000..732cd76
--- /dev/null
+++ b/client/build.gradle.kts
@@ -0,0 +1,41 @@
+plugins {
+    alias(libs.plugins.kotlin.multiplatform)
+    alias(libs.plugins.kotlin.serialization)
+}
+
+kotlin {
+    jvmToolchain(21)
+    jvm()
+    macosX64()
+    macosArm64()
+    iosX64()
+    iosArm64()
+    iosSimulatorArm64()
+    linuxX64()
+    linuxArm64()
+    mingwX64()
+
+    sourceSets {
+        commonMain.dependencies {
+            api(project(":api"))
+            implementation(libs.kotlinx.coroutines.core)
+            implementation(libs.kotlinx.serialization.json)
+            implementation(libs.ktor.client.core)
+        }
+        jvmMain.dependencies {
+            implementation(libs.ktor.client.cio)
+        }
+        nativeMain.dependencies {
+            implementation(libs.ktor.client.cio)
+        }
+        commonTest.dependencies {
+            implementation(kotlin("test"))
+        }
+        jvmTest.dependencies {
+            implementation(libs.kotlinx.coroutines.test)
+            implementation(project(":server"))
+            implementation(libs.ktor.server.test.host)
+            implementation(libs.ktor.server.sse)
+        }
+    }
+}
\ No newline at end of file
diff --git a/client/src/commonMain/kotlin/pw/binom/agui/client/HttpAgent.kt b/client/src/commonMain/kotlin/pw/binom/agui/client/HttpAgent.kt
new file mode 100644
index 0000000..4035dbc
--- /dev/null
+++ b/client/src/commonMain/kotlin/pw/binom/agui/client/HttpAgent.kt
@@ -0,0 +1,48 @@
+package pw.binom.agui.client
+
+import pw.binom.agui.api.agent.Agent
+import pw.binom.agui.api.event.BaseEvent
+import pw.binom.agui.api.run.RunAgentInput
+import pw.binom.agui.api.serialization.AguiJson
+import io.ktor.client.HttpClient
+import io.ktor.client.plugins.sse.sse
+import io.ktor.client.request.setBody
+import io.ktor.client.request.accept
+import io.ktor.http.ContentType
+import io.ktor.http.HttpMethod
+import io.ktor.http.contentType
+import kotlinx.coroutines.flow.Flow
+import kotlinx.coroutines.flow.flow
+import kotlinx.serialization.decodeFromString
+import kotlinx.serialization.encodeToString
+import kotlinx.serialization.json.Json
+
+/**
+ * A remote [Agent] that speaks the AG-UI transport: a `POST` of [RunAgentInput] as
+ * `application/json` to [endpointUrl], with the agent's [BaseEvent]s streamed back over
+ * Server-Sent Events, one JSON event per `data` line.
+ *
+ * The [HttpClient] is owned by the caller ([HttpAgent] does not close it).
+ */
+public class HttpAgent(
+    public val client: HttpClient,
+    public val endpointUrl: String,
+    public val json: Json = AguiJson,
+) : Agent {
+
+    override fun run(input: RunAgentInput): Flow<BaseEvent> = flow {
+        client.sse(
+            urlString = endpointUrl,
+            request = {
+                method = HttpMethod.Post
+                contentType(ContentType.Application.Json)
+                accept(ContentType.Text.EventStream)
+                setBody(json.encodeToString<RunAgentInput>(input))
+            },
+        ) {
+            incoming.collect { sse ->
+                sse.data?.let { emit(json.decodeFromString<BaseEvent>(it)) }
+            }
+        }
+    }
+}
\ No newline at end of file
diff --git a/client/src/jvmMain/kotlin/pw/binom/agui/client/HttpAgentFactory.kt b/client/src/jvmMain/kotlin/pw/binom/agui/client/HttpAgentFactory.kt
new file mode 100644
index 0000000..669b9a0
--- /dev/null
+++ b/client/src/jvmMain/kotlin/pw/binom/agui/client/HttpAgentFactory.kt
@@ -0,0 +1,26 @@
+package pw.binom.agui.client
+
+import io.ktor.client.HttpClient
+import io.ktor.client.HttpClientConfig
+import io.ktor.client.engine.cio.CIO
+import io.ktor.client.plugins.sse.SSE
+
+/**
+ * Creates an [HttpAgent] backed by a default CIO [HttpClient] with the SSE plugin installed
+ * and its lifecycle managed automatically.
+ *
+ * [configure] is applied to the client configuration; it runs before the SSE plugin is
+ * installed, so the plugin cannot be accidentally uninstalled. When you need full control
+ * over the [HttpClient] (custom engine, plugins, shared pools), construct [HttpAgent]
+ * directly instead.
+ */
+public fun createHttpAgent(
+    endpointUrl: String,
+    configure: HttpClientConfig<*>.() -> Unit = {},
+): HttpAgent = HttpAgent(
+    client = HttpClient(CIO) {
+        configure()
+        install(SSE)
+    },
+    endpointUrl = endpointUrl,
+)
\ No newline at end of file
diff --git a/client/src/jvmTest/kotlin/pw/binom/agui/client/HttpAgentTest.kt b/client/src/jvmTest/kotlin/pw/binom/agui/client/HttpAgentTest.kt
new file mode 100644
index 0000000..632d642
--- /dev/null
+++ b/client/src/jvmTest/kotlin/pw/binom/agui/client/HttpAgentTest.kt
@@ -0,0 +1,61 @@
+package pw.binom.agui.client
+
+import pw.binom.agui.api.agent.Agent
+import pw.binom.agui.api.event.RunFinishedEvent
+import pw.binom.agui.api.event.RunStartedEvent
+import pw.binom.agui.api.event.TextMessageContentEvent
+import pw.binom.agui.api.event.TextMessageEndEvent
+import pw.binom.agui.api.event.TextMessageStartEvent
+import pw.binom.agui.api.message.Message
+import pw.binom.agui.api.message.MessageRole
+import pw.binom.agui.api.run.RunAgentInput
+import pw.binom.agui.server.agui
+import io.ktor.client.plugins.sse.SSE
+import io.ktor.server.application.application
+import io.ktor.server.testing.testApplication
+import kotlinx.coroutines.flow.flow
+import kotlinx.coroutines.flow.toList
+import kotlinx.coroutines.test.runTest
+import kotlin.test.Test
+import kotlin.test.assertEquals
+import kotlin.test.assertIs
+
+/**
+ * Exercises [HttpAgent] against the real AG-UI endpoint exposed by [pw.binom.agui.server.agui],
+ * using the Ktor test host so the SSE transport is exercised end-to-end over HTTP.
+ */
+class HttpAgentTest {
+
+    private val agent: Agent = Agent { input ->
+        flow {
+            emit(RunStartedEvent(threadId = input.threadId, runId = input.runId))
+            val messageId = "m-${input.runId}"
+            emit(TextMessageStartEvent(messageId = messageId))
+            emit(TextMessageContentEvent(messageId = messageId, delta = "pong"))
+            emit(TextMessageEndEvent(messageId = messageId))
+            emit(RunFinishedEvent(threadId = input.threadId, runId = input.runId))
+        }
+    }
+
+    @Test
+    fun `run POSTs the input and decodes the SSE stream into typed events`() = runTest {
+        testApplication {
+            application {
+                agui(agent)
+            }
+            val httpAgent = HttpAgent(client = createClient { install(SSE) }, endpointUrl = "/agui")
+            val input = RunAgentInput(
+                threadId = "t1",
+                runId = "r1",
+                messages = listOf(Message(id = "m0", role = MessageRole.USER, content = "ping")),
+            )
+            val events = httpAgent.run(input).toList()
+
+            assertEquals(5, events.size)
+            assertEquals(RunStartedEvent(threadId = "t1", runId = "r1"), events.first())
+            assertIs<TextMessageStartEvent>(events[1])
+            assertIs<TextMessageContentEvent>(events[2]).let { assertEquals("pong", it.delta) }
+            assertEquals(RunFinishedEvent(threadId = "t1", runId = "r1"), events.last())
+        }
+    }
+}
diff --git a/gradle/libs.versions.toml b/gradle/libs.versions.toml
new file mode 100644
index 0000000..7168719
--- /dev/null
+++ b/gradle/libs.versions.toml
@@ -0,0 +1,26 @@
+[versions]
+kotlin = "2.2.0"
+kotlinx-coroutines = "1.10.2"
+kotlinx-serialization = "1.8.1"
+ktor = "3.1.3"
+
+[libraries]
+kotlinx-coroutines-core = { module = "org.jetbrains.kotlinx:kotlinx-coroutines-core", version.ref = "kotlinx-coroutines" }
+kotlinx-coroutines-test = { module = "org.jetbrains.kotlinx:kotlinx-coroutines-test", version.ref = "kotlinx-coroutines" }
+kotlinx-serialization-json = { module = "org.jetbrains.kotlinx:kotlinx-serialization-json", version.ref = "kotlinx-serialization" }
+
+ktor-server-core = { module = "io.ktor:ktor-server-core", version.ref = "ktor" }
+ktor-server-sse = { module = "io.ktor:ktor-server-sse", version.ref = "ktor" }
+ktor-server-netty = { module = "io.ktor:ktor-server-netty", version.ref = "ktor" }
+ktor-server-cio = { module = "io.ktor:ktor-server-cio", version.ref = "ktor" }
+ktor-server-content-negotiation = { module = "io.ktor:ktor-server-content-negotiation", version.ref = "ktor" }
+ktor-server-test-host = { module = "io.ktor:ktor-server-test-host", version.ref = "ktor" }
+
+ktor-client-core = { module = "io.ktor:ktor-client-core", version.ref = "ktor" }
+ktor-client-cio = { module = "io.ktor:ktor-client-cio", version.ref = "ktor" }
+ktor-client-content-negotiation = { module = "io.ktor:ktor-client-content-negotiation", version.ref = "ktor" }
+ktor-serialization-kotlinx-json = { module = "io.ktor:ktor-serialization-kotlinx-json", version.ref = "ktor" }
+
+[plugins]
+kotlin-multiplatform = { id = "org.jetbrains.kotlin.multiplatform", version.ref = "kotlin" }
+kotlin-serialization = { id = "org.jetbrains.kotlin.plugin.serialization", version.ref = "kotlin" }
\ No newline at end of file
diff --git a/gradle/wrapper/gradle-wrapper.jar b/gradle/wrapper/gradle-wrapper.jar
new file mode 100644
index 0000000..1b33c55
Binary files /dev/null and b/gradle/wrapper/gradle-wrapper.jar differ
diff --git a/gradle/wrapper/gradle-wrapper.properties b/gradle/wrapper/gradle-wrapper.properties
new file mode 100644
index 0000000..d4081da
--- /dev/null
+++ b/gradle/wrapper/gradle-wrapper.properties
@@ -0,0 +1,7 @@
+distributionBase=GRADLE_USER_HOME
+distributionPath=wrapper/dists
+distributionUrl=https\://services.gradle.org/distributions/gradle-8.14.3-bin.zip
+networkTimeout=10000
+validateDistributionUrl=true
+zipStoreBase=GRADLE_USER_HOME
+zipStorePath=wrapper/dists
diff --git a/gradlew b/gradlew
new file mode 100755
index 0000000..23d15a9
--- /dev/null
+++ b/gradlew
@@ -0,0 +1,251 @@
+#!/bin/sh
+
+#
+# Copyright © 2015-2021 the original authors.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#      https://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+#
+# SPDX-License-Identifier: Apache-2.0
+#
+
+##############################################################################
+#
+#   Gradle start up script for POSIX generated by Gradle.
+#
+#   Important for running:
+#
+#   (1) You need a POSIX-compliant shell to run this script. If your /bin/sh is
+#       noncompliant, but you have some other compliant shell such as ksh or
+#       bash, then to run this script, type that shell name before the whole
+#       command line, like:
+#
+#           ksh Gradle
+#
+#       Busybox and similar reduced shells will NOT work, because this script
+#       requires all of these POSIX shell features:
+#         * functions;
+#         * expansions «$var», «${var}», «${var:-default}», «${var+SET}»,
+#           «${var#prefix}», «${var%suffix}», and «$( cmd )»;
+#         * compound commands having a testable exit status, especially «case»;
+#         * various built-in commands including «command», «set», and «ulimit».
+#
+#   Important for patching:
+#
+#   (2) This script targets any POSIX shell, so it avoids extensions provided
+#       by Bash, Ksh, etc; in particular arrays are avoided.
+#
+#       The "traditional" practice of packing multiple parameters into a
+#       space-separated string is a well documented source of bugs and security
+#       problems, so this is (mostly) avoided, by progressively accumulating
+#       options in "$@", and eventually passing that to Java.
+#
+#       Where the inherited environment variables (DEFAULT_JVM_OPTS, JAVA_OPTS,
+#       and GRADLE_OPTS) rely on word-splitting, this is performed explicitly;
+#       see the in-line comments for details.
+#
+#       There are tweaks for specific operating systems such as AIX, CygWin,
+#       Darwin, MinGW, and NonStop.
+#
+#   (3) This script is generated from the Groovy template
+#       https://github.com/gradle/gradle/blob/HEAD/platforms/jvm/plugins-application/src/main/resources/org/gradle/api/internal/plugins/unixStartScript.txt
+#       within the Gradle project.
+#
+#       You can find Gradle at https://github.com/gradle/gradle/.
+#
+##############################################################################
+
+# Attempt to set APP_HOME
+
+# Resolve links: $0 may be a link
+app_path=$0
+
+# Need this for daisy-chained symlinks.
+while
+    APP_HOME=${app_path%"${app_path##*/}"}  # leaves a trailing /; empty if no leading path
+    [ -h "$app_path" ]
+do
+    ls=$( ls -ld "$app_path" )
+    link=${ls#*' -> '}
+    case $link in             #(
+      /*)   app_path=$link ;; #(
+      *)    app_path=$APP_HOME$link ;;
+    esac
+done
+
+# This is normally unused
+# shellcheck disable=SC2034
+APP_BASE_NAME=${0##*/}
+# Discard cd standard output in case $CDPATH is set (https://github.com/gradle/gradle/issues/25036)
+APP_HOME=$( cd -P "${APP_HOME:-./}" > /dev/null && printf '%s\n' "$PWD" ) || exit
+
+# Use the maximum available, or set MAX_FD != -1 to use that value.
+MAX_FD=maximum
+
+warn () {
+    echo "$*"
+} >&2
+
+die () {
+    echo
+    echo "$*"
+    echo
+    exit 1
+} >&2
+
+# OS specific support (must be 'true' or 'false').
+cygwin=false
+msys=false
+darwin=false
+nonstop=false
+case "$( uname )" in                #(
+  CYGWIN* )         cygwin=true  ;; #(
+  Darwin* )         darwin=true  ;; #(
+  MSYS* | MINGW* )  msys=true    ;; #(
+  NONSTOP* )        nonstop=true ;;
+esac
+
+CLASSPATH="\\\"\\\""
+
+
+# Determine the Java command to use to start the JVM.
+if [ -n "$JAVA_HOME" ] ; then
+    if [ -x "$JAVA_HOME/jre/sh/java" ] ; then
+        # IBM's JDK on AIX uses strange locations for the executables
+        JAVACMD=$JAVA_HOME/jre/sh/java
+    else
+        JAVACMD=$JAVA_HOME/bin/java
+    fi
+    if [ ! -x "$JAVACMD" ] ; then
+        die "ERROR: JAVA_HOME is set to an invalid directory: $JAVA_HOME
+
+Please set the JAVA_HOME variable in your environment to match the
+location of your Java installation."
+    fi
+else
+    JAVACMD=java
+    if ! command -v java >/dev/null 2>&1
+    then
+        die "ERROR: JAVA_HOME is not set and no 'java' command could be found in your PATH.
+
+Please set the JAVA_HOME variable in your environment to match the
+location of your Java installation."
+    fi
+fi
+
+# Increase the maximum file descriptors if we can.
+if ! "$cygwin" && ! "$darwin" && ! "$nonstop" ; then
+    case $MAX_FD in #(
+      max*)
+        # In POSIX sh, ulimit -H is undefined. That's why the result is checked to see if it worked.
+        # shellcheck disable=SC2039,SC3045
+        MAX_FD=$( ulimit -H -n ) ||
+            warn "Could not query maximum file descriptor limit"
+    esac
+    case $MAX_FD in  #(
+      '' | soft) :;; #(
+      *)
+        # In POSIX sh, ulimit -n is undefined. That's why the result is checked to see if it worked.
+        # shellcheck disable=SC2039,SC3045
+        ulimit -n "$MAX_FD" ||
+            warn "Could not set maximum file descriptor limit to $MAX_FD"
+    esac
+fi
+
+# Collect all arguments for the java command, stacking in reverse order:
+#   * args from the command line
+#   * the main class name
+#   * -classpath
+#   * -D...appname settings
+#   * --module-path (only if needed)
+#   * DEFAULT_JVM_OPTS, JAVA_OPTS, and GRADLE_OPTS environment variables.
+
+# For Cygwin or MSYS, switch paths to Windows format before running java
+if "$cygwin" || "$msys" ; then
+    APP_HOME=$( cygpath --path --mixed "$APP_HOME" )
+    CLASSPATH=$( cygpath --path --mixed "$CLASSPATH" )
+
+    JAVACMD=$( cygpath --unix "$JAVACMD" )
+
+    # Now convert the arguments - kludge to limit ourselves to /bin/sh
+    for arg do
+        if
+            case $arg in                                #(
+              -*)   false ;;                            # don't mess with options #(
+              /?*)  t=${arg#/} t=/${t%%/*}              # looks like a POSIX filepath
+                    [ -e "$t" ] ;;                      #(
+              *)    false ;;
+            esac
+        then
+            arg=$( cygpath --path --ignore --mixed "$arg" )
+        fi
+        # Roll the args list around exactly as many times as the number of
+        # args, so each arg winds up back in the position where it started, but
+        # possibly modified.
+        #
+        # NB: a `for` loop captures its iteration list before it begins, so
+        # changing the positional parameters here affects neither the number of
+        # iterations, nor the values presented in `arg`.
+        shift                   # remove old arg
+        set -- "$@" "$arg"      # push replacement arg
+    done
+fi
+
+
+# Add default JVM options here. You can also use JAVA_OPTS and GRADLE_OPTS to pass JVM options to this script.
+DEFAULT_JVM_OPTS='"-Xmx64m" "-Xms64m"'
+
+# Collect all arguments for the java command:
+#   * DEFAULT_JVM_OPTS, JAVA_OPTS, and optsEnvironmentVar are not allowed to contain shell fragments,
+#     and any embedded shellness will be escaped.
+#   * For example: A user cannot expect ${Hostname} to be expanded, as it is an environment variable and will be
+#     treated as '${Hostname}' itself on the command line.
+
+set -- \
+        "-Dorg.gradle.appname=$APP_BASE_NAME" \
+        -classpath "$CLASSPATH" \
+        -jar "$APP_HOME/gradle/wrapper/gradle-wrapper.jar" \
+        "$@"
+
+# Stop when "xargs" is not available.
+if ! command -v xargs >/dev/null 2>&1
+then
+    die "xargs is not available"
+fi
+
+# Use "xargs" to parse quoted args.
+#
+# With -n1 it outputs one arg per line, with the quotes and backslashes removed.
+#
+# In Bash we could simply go:
+#
+#   readarray ARGS < <( xargs -n1 <<<"$var" ) &&
+#   set -- "${ARGS[@]}" "$@"
+#
+# but POSIX shell has neither arrays nor command substitution, so instead we
+# post-process each arg (as a line of input to sed) to backslash-escape any
+# character that might be a shell metacharacter, then use eval to reverse
+# that process (while maintaining the separation between arguments), and wrap
+# the whole thing up as a single "set" statement.
+#
+# This will of course break if any of these variables contains a newline or
+# an unmatched quote.
+#
+
+eval "set -- $(
+        printf '%s\n' "$DEFAULT_JVM_OPTS $JAVA_OPTS $GRADLE_OPTS" |
+        xargs -n1 |
+        sed ' s~[^-[:alnum:]+,./:=@_]~\\&~g; ' |
+        tr '\n' ' '
+    )" '"$@"'
+
+exec "$JAVACMD" "$@"
diff --git a/gradlew.bat b/gradlew.bat
new file mode 100644
index 0000000..db3a6ac
--- /dev/null
+++ b/gradlew.bat
@@ -0,0 +1,94 @@
+@rem
+@rem Copyright 2015 the original author or authors.
+@rem
+@rem Licensed under the Apache License, Version 2.0 (the "License");
+@rem you may not use this file except in compliance with the License.
+@rem You may obtain a copy of the License at
+@rem
+@rem      https://www.apache.org/licenses/LICENSE-2.0
+@rem
+@rem Unless required by applicable law or agreed to in writing, software
+@rem distributed under the License is distributed on an "AS IS" BASIS,
+@rem WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+@rem See the License for the specific language governing permissions and
+@rem limitations under the License.
+@rem
+@rem SPDX-License-Identifier: Apache-2.0
+@rem
+
+@if "%DEBUG%"=="" @echo off
+@rem ##########################################################################
+@rem
+@rem  Gradle startup script for Windows
+@rem
+@rem ##########################################################################
+
+@rem Set local scope for the variables with windows NT shell
+if "%OS%"=="Windows_NT" setlocal
+
+set DIRNAME=%~dp0
+if "%DIRNAME%"=="" set DIRNAME=.
+@rem This is normally unused
+set APP_BASE_NAME=%~n0
+set APP_HOME=%DIRNAME%
+
+@rem Resolve any "." and ".." in APP_HOME to make it shorter.
+for %%i in ("%APP_HOME%") do set APP_HOME=%%~fi
+
+@rem Add default JVM options here. You can also use JAVA_OPTS and GRADLE_OPTS to pass JVM options to this script.
+set DEFAULT_JVM_OPTS="-Xmx64m" "-Xms64m"
+
+@rem Find java.exe
+if defined JAVA_HOME goto findJavaFromJavaHome
+
+set JAVA_EXE=java.exe
+%JAVA_EXE% -version >NUL 2>&1
+if %ERRORLEVEL% equ 0 goto execute
+
+echo. 1>&2
+echo ERROR: JAVA_HOME is not set and no 'java' command could be found in your PATH. 1>&2
+echo. 1>&2
+echo Please set the JAVA_HOME variable in your environment to match the 1>&2
+echo location of your Java installation. 1>&2
+
+goto fail
+
+:findJavaFromJavaHome
+set JAVA_HOME=%JAVA_HOME:"=%
+set JAVA_EXE=%JAVA_HOME%/bin/java.exe
+
+if exist "%JAVA_EXE%" goto execute
+
+echo. 1>&2
+echo ERROR: JAVA_HOME is set to an invalid directory: %JAVA_HOME% 1>&2
+echo. 1>&2
+echo Please set the JAVA_HOME variable in your environment to match the 1>&2
+echo location of your Java installation. 1>&2
+
+goto fail
+
+:execute
+@rem Setup the command line
+
+set CLASSPATH=
+
+
+@rem Execute Gradle
+"%JAVA_EXE%" %DEFAULT_JVM_OPTS% %JAVA_OPTS% %GRADLE_OPTS% "-Dorg.gradle.appname=%APP_BASE_NAME%" -classpath "%CLASSPATH%" -jar "%APP_HOME%\gradle\wrapper\gradle-wrapper.jar" %*
+
+:end
+@rem End local scope for the variables with windows NT shell
+if %ERRORLEVEL% equ 0 goto mainEnd
+
+:fail
+rem Set variable GRADLE_EXIT_CONSOLE if you need the _script_ return code instead of
+rem the _cmd.exe /c_ return code!
+set EXIT_CODE=%ERRORLEVEL%
+if %EXIT_CODE% equ 0 set EXIT_CODE=1
+if not ""=="%GRADLE_EXIT_CONSOLE%" exit %EXIT_CODE%
+exit /b %EXIT_CODE%
+
+:mainEnd
+if "%OS%"=="Windows_NT" endlocal
+
+:omega
diff --git a/server/build.gradle.kts b/server/build.gradle.kts
new file mode 100644
index 0000000..7a18d40
--- /dev/null
+++ b/server/build.gradle.kts
@@ -0,0 +1,41 @@
+plugins {
+    alias(libs.plugins.kotlin.multiplatform)
+    alias(libs.plugins.kotlin.serialization)
+}
+
+kotlin {
+    jvmToolchain(21)
+    jvm()
+    macosX64()
+    macosArm64()
+    iosX64()
+    iosArm64()
+    iosSimulatorArm64()
+    linuxX64()
+    linuxArm64()
+    mingwX64()
+
+    sourceSets {
+        commonMain.dependencies {
+            api(project(":api"))
+            implementation(libs.kotlinx.coroutines.core)
+            implementation(libs.kotlinx.serialization.json)
+            implementation(libs.ktor.server.core)
+            implementation(libs.ktor.server.sse)
+        }
+        jvmMain.dependencies {
+            implementation(libs.ktor.server.netty)
+        }
+        nativeMain.dependencies {
+            implementation(libs.ktor.server.cio)
+        }
+        jvmTest.dependencies {
+            implementation(kotlin("test"))
+            implementation(libs.kotlinx.coroutines.test)
+            implementation(libs.ktor.server.test.host)
+            implementation(libs.ktor.client.core)
+            implementation(libs.ktor.client.cio)
+            implementation(project(":client"))
+        }
+    }
+}
\ No newline at end of file
diff --git a/server/src/commonMain/kotlin/pw/binom/agui/server/Agui.kt b/server/src/commonMain/kotlin/pw/binom/agui/server/Agui.kt
new file mode 100644
index 0000000..95b638a
--- /dev/null
+++ b/server/src/commonMain/kotlin/pw/binom/agui/server/Agui.kt
@@ -0,0 +1,81 @@
+package pw.binom.agui.server
+
+import pw.binom.agui.api.agent.Agent
+import pw.binom.agui.api.event.BaseEvent
+import pw.binom.agui.api.event.RunErrorEvent
+import pw.binom.agui.api.run.RunAgentInput
+import pw.binom.agui.api.serialization.AguiJson
+import io.ktor.server.application.Application
+import io.ktor.server.application.ApplicationCall
+import io.ktor.server.application.call
+import io.ktor.server.request.receiveText
+import io.ktor.server.response.respond
+import io.ktor.server.routing.Route
+import io.ktor.server.routing.post
+import io.ktor.server.routing.routing
+import io.ktor.server.sse.SSEServerContent
+import io.ktor.server.sse.ServerSSESession
+import kotlinx.coroutines.CancellationException
+import kotlinx.coroutines.flow.collect
+import kotlinx.serialization.SerializationException
+import kotlinx.serialization.encodeToString
+import kotlinx.serialization.json.Json
+
+/**
+ * Exposes [agent] over the AG-UI HTTP + SSE transport on [path].
+ *
+ * The endpoint accepts a `POST` with a [RunAgentInput] JSON body and replies with
+ * `text/event-stream`: each server-sent event carries one [BaseEvent] as its `data` payload.
+ *
+ * If the agent's flow throws, a [RunErrorEvent] is emitted before the stream closes.
+ *
+ * This function installs nothing globally: no content negotiation, no plugins — just an
+ * endpoint inside the application's routing. Add other routes freely.
+ */
+public fun Application.agui(
+    agent: Agent,
+    path: String = "/agui",
+    json: Json = AguiJson,
+) {
+    routing {
+        aguiAgent(agent, path, json)
+    }
+}
+
+/**
+ * Route-level variant for composing into an existing routing block. Unlike
+ * [Application.agui] it does not create its own routing context.
+ */
+public fun Route.aguiAgent(
+    agent: Agent,
+    path: String = "/agui",
+    json: Json = AguiJson,
+) {
+    post(path) {
+        val input: RunAgentInput = decodeInput(call, json)
+        val handler: suspend (ServerSSESession) -> Unit = { session ->
+            try {
+                agent.run(input).collect { event ->
+                    session.send(json.encodeToString<BaseEvent>(event))
+                }
+            } catch (e: CancellationException) {
+                throw e
+            } catch (e: Throwable) {
+                session.send(json.encodeToString<BaseEvent>(RunErrorEvent(e.message ?: "Agent error")))
+            }
+        }
+        call.respond(SSEServerContent(call, handler))
+    }
+}
+
+private suspend fun decodeInput(call: ApplicationCall, json: Json): RunAgentInput {
+    val text = call.receiveText()
+    if (text.isBlank()) {
+        return RunAgentInput(threadId = "", runId = "")
+    }
+    return try {
+        json.decodeFromString(RunAgentInput.serializer(), text)
+    } catch (e: SerializationException) {
+        throw IllegalArgumentException("Malformed AG-UI RunAgentInput: ${e.message}", e)
+    }
+}
\ No newline at end of file
diff --git a/server/src/jvmMain/kotlin/pw/binom/agui/server/demo/SampleServer.kt b/server/src/jvmMain/kotlin/pw/binom/agui/server/demo/SampleServer.kt
new file mode 100644
index 0000000..a0a962d
--- /dev/null
+++ b/server/src/jvmMain/kotlin/pw/binom/agui/server/demo/SampleServer.kt
@@ -0,0 +1,39 @@
+package pw.binom.agui.server.demo
+
+import pw.binom.agui.api.agent.Agent
+import pw.binom.agui.api.event.RunFinishedEvent
+import pw.binom.agui.api.event.RunStartedEvent
+import pw.binom.agui.api.event.StateSnapshotEvent
+import pw.binom.agui.api.event.TextMessageContentEvent
+import pw.binom.agui.api.event.TextMessageEndEvent
+import pw.binom.agui.api.event.TextMessageStartEvent
+import pw.binom.agui.server.agui
+import io.ktor.server.engine.embeddedServer
+import io.ktor.server.netty.Netty
+import kotlinx.coroutines.flow.flow
+
+/**
+ * A minimal AG-UI server that echoes the last user message back.
+ *
+ * Run it with:  gradlew :server:run   (or start the embedded server)
+ * then:  curl -N -X POST http://localhost:8080/agui -H "Content-Type: application/json" \
+ *        -d '{"threadId":"t","runId":"r","messages":[{"id":"m","role":"user","content":"hi"}]}'
+ */
+private val echoAgent: Agent = Agent { input ->
+    flow {
+        emit(RunStartedEvent(threadId = input.threadId, runId = input.runId))
+        emit(StateSnapshotEvent(snapshot = input.state))
+        val reply = (input.messages.lastOrNull()?.content ?: "world").ifBlank { "world" }
+        val messageId = "msg-${input.runId}"
+        emit(TextMessageStartEvent(messageId = messageId))
+        emit(TextMessageContentEvent(messageId = messageId, delta = "Hello, $reply!"))
+        emit(TextMessageEndEvent(messageId = messageId))
+        emit(RunFinishedEvent(threadId = input.threadId, runId = input.runId))
+    }
+}
+
+fun main() {
+    embeddedServer(Netty, port = 8080, host = "0.0.0.0") {
+        agui(echoAgent, path = "/agui")
+    }.start(wait = true)
+}
\ No newline at end of file
diff --git a/server/src/jvmTest/kotlin/pw/binom/agui/server/AguiServerTest.kt b/server/src/jvmTest/kotlin/pw/binom/agui/server/AguiServerTest.kt
new file mode 100644
index 0000000..032abea
--- /dev/null
+++ b/server/src/jvmTest/kotlin/pw/binom/agui/server/AguiServerTest.kt
@@ -0,0 +1,81 @@
+package pw.binom.agui.server
+
+import pw.binom.agui.api.agent.Agent
+import pw.binom.agui.api.event.RunErrorEvent
+import pw.binom.agui.api.event.RunFinishedEvent
+import pw.binom.agui.api.event.RunStartedEvent
+import pw.binom.agui.api.event.StateSnapshotEvent
+import pw.binom.agui.api.event.TextMessageContentEvent
+import pw.binom.agui.api.event.TextMessageEndEvent
+import pw.binom.agui.api.event.TextMessageStartEvent
+import pw.binom.agui.api.message.Message
+import pw.binom.agui.api.message.MessageRole
+import pw.binom.agui.api.run.RunAgentInput
+import pw.binom.agui.api.state.mutableState
+import pw.binom.agui.client.HttpAgent
+import io.ktor.client.plugins.sse.SSE
+import io.ktor.server.application.application
+import io.ktor.server.testing.testApplication
+import kotlinx.coroutines.flow.flow
+import kotlinx.coroutines.flow.toList
+import kotlinx.coroutines.test.runTest
+import kotlinx.serialization.json.JsonPrimitive
+import kotlin.test.Test
+import kotlin.test.assertEquals
+import kotlin.test.assertTrue
+
+class AguiServerTest {
+
+    private val agent: Agent = Agent { input ->
+        flow {
+            emit(RunStartedEvent(threadId = input.threadId, runId = input.runId))
+            emit(StateSnapshotEvent(snapshot = input.state))
+            val messageId = "msg-${input.runId}"
+            emit(TextMessageStartEvent(messageId = messageId))
+            val last = input.messages.lastOrNull()
+            emit(TextMessageContentEvent(messageId = messageId, delta = "Hello ${last?.content ?: "world"}"))
+            emit(TextMessageEndEvent(messageId = messageId))
+            emit(RunFinishedEvent(threadId = input.threadId, runId = input.runId))
+        }
+    }
+
+    private val failingAgent: Agent = Agent { _ ->
+        flow { throw IllegalStateException("boom") }
+    }
+
+    @Test
+    fun `POST runs an agent and streams events via SSE`() = runTest {
+        testApplication {
+            application {
+                agui(agent)
+            }
+            val httpAgent = HttpAgent(client = createClient { install(SSE) }, endpointUrl = "/agui")
+            val input = RunAgentInput(
+                threadId = "t1",
+                runId = "r1",
+                messages = listOf(Message(id = "m0", role = MessageRole.USER, content = "hi")),
+                state = mutableState("counter" to JsonPrimitive(42)),
+            )
+            val events = httpAgent.run(input).toList()
+
+            assertEquals(RunStartedEvent(threadId = "t1", runId = "r1"), events.first())
+            assertEquals(RunFinishedEvent(threadId = "t1", runId = "r1"), events.last())
+            val snapshot = events.filterIsInstance<StateSnapshotEvent>().single()
+            assertEquals(mutableState("counter" to JsonPrimitive(42)), snapshot.snapshot)
+            assertTrue(events.any { it is TextMessageContentEvent && it.delta == "Hello hi" })
+        }
+    }
+
+    @Test
+    fun `an agent failure is signalled with a RUN_ERROR event`() = runTest {
+        testApplication {
+            application {
+                agui(failingAgent)
+            }
+            val httpAgent = HttpAgent(client = createClient { install(SSE) }, endpointUrl = "/agui")
+            val events = httpAgent.run(RunAgentInput(threadId = "t1", runId = "r1")).toList()
+            val error = events.single() as RunErrorEvent
+            assertEquals("boom", error.message)
+        }
+    }
+}
\ No newline at end of file
diff --git a/settings.gradle.kts b/settings.gradle.kts
new file mode 100644
index 0000000..751f727
--- /dev/null
+++ b/settings.gradle.kts
@@ -0,0 +1,16 @@
+rootProject.name = "agui"
+
+pluginManagement {
+    repositories {
+        gradlePluginPortal()
+        mavenCentral()
+    }
+}
+
+dependencyResolutionManagement {
+    repositories {
+        mavenCentral()
+    }
+}
+
+include(":api", ":client", ":server")
\ No newline at end of file