diff --git a/workflow/event.go b/workflow/event.go
new file mode 100644
index 0000000..1594b07
--- /dev/null
+++ b/workflow/event.go
@@ -0,0 +1,356 @@
+package workflow
+
+import (
+	"encoding/json"
+	"fmt"
+)
+
+// EventType identifies the kind of workflow event.
+type EventType string
+
+const (
+	EventWorkflowStarted         EventType = "WORKFLOW_EXECUTION_STARTED"
+	EventWorkflowCompleted       EventType = "WORKFLOW_EXECUTION_COMPLETED"
+	EventWorkflowFailed          EventType = "WORKFLOW_EXECUTION_FAILED"
+	EventWorkflowCanceled        EventType = "WORKFLOW_EXECUTION_CANCELED"
+	EventWorkflowContinuedAsNew  EventType = "WORKFLOW_EXECUTION_CONTINUED_AS_NEW"
+	EventWorkflowTaskTimedOut    EventType = "WORKFLOW_TASK_TIMED_OUT"
+	EventWorkflowTaskFailed      EventType = "WORKFLOW_TASK_FAILED"
+	EventCustomTaskStarted       EventType = "CUSTOM_TASK_STARTED"
+	EventCustomTaskInProgress    EventType = "CUSTOM_TASK_IN_PROGRESS"
+	EventCustomTaskCompleted     EventType = "CUSTOM_TASK_COMPLETED"
+	EventCustomTaskFailed        EventType = "CUSTOM_TASK_FAILED"
+	EventCustomTaskTimedOut      EventType = "CUSTOM_TASK_TIMED_OUT"
+	EventCustomTaskCanceled      EventType = "CUSTOM_TASK_CANCELED"
+	EventActivityTaskStarted     EventType = "ACTIVITY_TASK_STARTED"
+	EventActivityTaskCompleted   EventType = "ACTIVITY_TASK_COMPLETED"
+	EventActivityTaskRetrying    EventType = "ACTIVITY_TASK_RETRYING"
+	EventActivityTaskFailed      EventType = "ACTIVITY_TASK_FAILED"
+)
+
+// EventSource identifies where an event originated.
+type EventSource string
+
+const (
+	EventSourceDatabase EventSource = "DATABASE"
+	EventSourceLive     EventSource = "LIVE"
+)
+
+// Scope identifies the scope of an event subscription.
+type Scope string
+
+const (
+	ScopeActivity Scope = "activity"
+	ScopeWorkflow Scope = "workflow"
+	ScopeAll      Scope = "*"
+)
+
+// Event is a sealed interface for workflow execution events.
+type Event interface {
+	workflowEvent()
+	EventType() EventType
+}
+
+// eventBase holds fields common to all workflow events.
+type eventBase struct {
+	ID                   string  `json:"event_id"`
+	Timestamp            int64   `json:"event_timestamp"`
+	RootWorkflowExecID   string  `json:"root_workflow_exec_id"`
+	ParentWorkflowExecID *string `json:"parent_workflow_exec_id"`
+	WorkflowExecID       string  `json:"workflow_exec_id"`
+	WorkflowRunID        string  `json:"workflow_run_id"`
+	WorkflowName         string  `json:"workflow_name"`
+}
+
+// WorkflowStartedAttributes holds typed attributes for workflow started events.
+type WorkflowStartedAttributes struct {
+	TaskID string `json:"task_id"`
+}
+
+// JSONPayload holds a typed JSON value.
+type JSONPayload struct {
+	Value any    `json:"value"`
+	Type  string `json:"type"`
+}
+
+// WorkflowCompletedAttributes holds typed attributes for workflow completed events.
+type WorkflowCompletedAttributes struct {
+	TaskID string      `json:"task_id"`
+	Result JSONPayload `json:"result"`
+}
+
+// WorkflowFailedAttributes holds typed attributes for workflow failed events.
+type WorkflowFailedAttributes struct {
+	TaskID  string `json:"task_id"`
+	Failure any    `json:"failure"`
+}
+
+// WorkflowExecutionStartedEvent signals that a workflow execution has started.
+type WorkflowExecutionStartedEvent struct {
+	eventBase
+	Attributes WorkflowStartedAttributes `json:"attributes"`
+}
+
+func (*WorkflowExecutionStartedEvent) workflowEvent()      {}
+func (*WorkflowExecutionStartedEvent) EventType() EventType { return EventWorkflowStarted }
+
+// WorkflowExecutionCompletedEvent signals that a workflow execution has completed.
+type WorkflowExecutionCompletedEvent struct {
+	eventBase
+	Attributes WorkflowCompletedAttributes `json:"attributes"`
+}
+
+func (*WorkflowExecutionCompletedEvent) workflowEvent()      {}
+func (*WorkflowExecutionCompletedEvent) EventType() EventType { return EventWorkflowCompleted }
+
+// WorkflowExecutionFailedEvent signals that a workflow execution has failed.
+type WorkflowExecutionFailedEvent struct {
+	eventBase
+	Attributes WorkflowFailedAttributes `json:"attributes"`
+}
+
+func (*WorkflowExecutionFailedEvent) workflowEvent()      {}
+func (*WorkflowExecutionFailedEvent) EventType() EventType { return EventWorkflowFailed }
+
+// WorkflowExecutionCanceledEvent signals that a workflow execution was canceled.
+type WorkflowExecutionCanceledEvent struct {
+	eventBase
+	Attributes json.RawMessage `json:"attributes"`
+}
+
+func (*WorkflowExecutionCanceledEvent) workflowEvent()      {}
+func (*WorkflowExecutionCanceledEvent) EventType() EventType { return EventWorkflowCanceled }
+
+// WorkflowExecutionContinuedAsNewEvent signals that a workflow continued as a new execution.
+type WorkflowExecutionContinuedAsNewEvent struct {
+	eventBase
+	Attributes json.RawMessage `json:"attributes"`
+}
+
+func (*WorkflowExecutionContinuedAsNewEvent) workflowEvent()      {}
+func (*WorkflowExecutionContinuedAsNewEvent) EventType() EventType { return EventWorkflowContinuedAsNew }
+
+// WorkflowTaskTimedOutEvent signals that a workflow task timed out.
+type WorkflowTaskTimedOutEvent struct {
+	eventBase
+	Attributes json.RawMessage `json:"attributes"`
+}
+
+func (*WorkflowTaskTimedOutEvent) workflowEvent()      {}
+func (*WorkflowTaskTimedOutEvent) EventType() EventType { return EventWorkflowTaskTimedOut }
+
+// WorkflowTaskFailedEvent signals that a workflow task failed.
+type WorkflowTaskFailedEvent struct {
+	eventBase
+	Attributes json.RawMessage `json:"attributes"`
+}
+
+func (*WorkflowTaskFailedEvent) workflowEvent()      {}
+func (*WorkflowTaskFailedEvent) EventType() EventType { return EventWorkflowTaskFailed }
+
+// CustomTaskStartedEvent signals that a custom task has started.
+type CustomTaskStartedEvent struct {
+	eventBase
+	Attributes json.RawMessage `json:"attributes"`
+}
+
+func (*CustomTaskStartedEvent) workflowEvent()      {}
+func (*CustomTaskStartedEvent) EventType() EventType { return EventCustomTaskStarted }
+
+// CustomTaskInProgressEvent signals that a custom task is in progress.
+type CustomTaskInProgressEvent struct {
+	eventBase
+	Attributes json.RawMessage `json:"attributes"`
+}
+
+func (*CustomTaskInProgressEvent) workflowEvent()      {}
+func (*CustomTaskInProgressEvent) EventType() EventType { return EventCustomTaskInProgress }
+
+// CustomTaskCompletedEvent signals that a custom task has completed.
+type CustomTaskCompletedEvent struct {
+	eventBase
+	Attributes json.RawMessage `json:"attributes"`
+}
+
+func (*CustomTaskCompletedEvent) workflowEvent()      {}
+func (*CustomTaskCompletedEvent) EventType() EventType { return EventCustomTaskCompleted }
+
+// CustomTaskFailedEvent signals that a custom task has failed.
+type CustomTaskFailedEvent struct {
+	eventBase
+	Attributes json.RawMessage `json:"attributes"`
+}
+
+func (*CustomTaskFailedEvent) workflowEvent()      {}
+func (*CustomTaskFailedEvent) EventType() EventType { return EventCustomTaskFailed }
+
+// CustomTaskTimedOutEvent signals that a custom task timed out.
+type CustomTaskTimedOutEvent struct {
+	eventBase
+	Attributes json.RawMessage `json:"attributes"`
+}
+
+func (*CustomTaskTimedOutEvent) workflowEvent()      {}
+func (*CustomTaskTimedOutEvent) EventType() EventType { return EventCustomTaskTimedOut }
+
+// CustomTaskCanceledEvent signals that a custom task was canceled.
+type CustomTaskCanceledEvent struct {
+	eventBase
+	Attributes json.RawMessage `json:"attributes"`
+}
+
+func (*CustomTaskCanceledEvent) workflowEvent()      {}
+func (*CustomTaskCanceledEvent) EventType() EventType { return EventCustomTaskCanceled }
+
+// ActivityTaskStartedEvent signals that an activity task has started.
+type ActivityTaskStartedEvent struct {
+	eventBase
+	Attributes json.RawMessage `json:"attributes"`
+}
+
+func (*ActivityTaskStartedEvent) workflowEvent()      {}
+func (*ActivityTaskStartedEvent) EventType() EventType { return EventActivityTaskStarted }
+
+// ActivityTaskCompletedEvent signals that an activity task has completed.
+type ActivityTaskCompletedEvent struct {
+	eventBase
+	Attributes json.RawMessage `json:"attributes"`
+}
+
+func (*ActivityTaskCompletedEvent) workflowEvent()      {}
+func (*ActivityTaskCompletedEvent) EventType() EventType { return EventActivityTaskCompleted }
+
+// ActivityTaskRetryingEvent signals that an activity task is being retried.
+type ActivityTaskRetryingEvent struct {
+	eventBase
+	Attributes json.RawMessage `json:"attributes"`
+}
+
+func (*ActivityTaskRetryingEvent) workflowEvent()      {}
+func (*ActivityTaskRetryingEvent) EventType() EventType { return EventActivityTaskRetrying }
+
+// ActivityTaskFailedEvent signals that an activity task has failed.
+type ActivityTaskFailedEvent struct {
+	eventBase
+	Attributes json.RawMessage `json:"attributes"`
+}
+
+func (*ActivityTaskFailedEvent) workflowEvent()      {}
+func (*ActivityTaskFailedEvent) EventType() EventType { return EventActivityTaskFailed }
+
+// UnknownEvent holds an event with an unrecognized event_type.
+// This prevents the SDK from breaking when new event types are added.
+type UnknownEvent struct {
+	eventBase
+	RawType string
+	Raw     json.RawMessage
+}
+
+func (*UnknownEvent) workflowEvent()       {}
+func (e *UnknownEvent) EventType() EventType { return EventType(e.RawType) }
+
+// UnmarshalEvent dispatches JSON to the concrete Event type
+// based on the "event_type" discriminator field.
+func UnmarshalEvent(data []byte) (Event, error) {
+	var probe struct {
+		Type string `json:"event_type"`
+	}
+	if err := json.Unmarshal(data, &probe); err != nil {
+		return nil, fmt.Errorf("mistral: unmarshal workflow event: %w", err)
+	}
+	switch probe.Type {
+	case string(EventWorkflowStarted):
+		var e WorkflowExecutionStartedEvent
+		return &e, json.Unmarshal(data, &e)
+	case string(EventWorkflowCompleted):
+		var e WorkflowExecutionCompletedEvent
+		return &e, json.Unmarshal(data, &e)
+	case string(EventWorkflowFailed):
+		var e WorkflowExecutionFailedEvent
+		return &e, json.Unmarshal(data, &e)
+	case string(EventWorkflowCanceled):
+		var e WorkflowExecutionCanceledEvent
+		return &e, json.Unmarshal(data, &e)
+	case string(EventWorkflowContinuedAsNew):
+		var e WorkflowExecutionContinuedAsNewEvent
+		return &e, json.Unmarshal(data, &e)
+	case string(EventWorkflowTaskTimedOut):
+		var e WorkflowTaskTimedOutEvent
+		return &e, json.Unmarshal(data, &e)
+	case string(EventWorkflowTaskFailed):
+		var e WorkflowTaskFailedEvent
+		return &e, json.Unmarshal(data, &e)
+	case string(EventCustomTaskStarted):
+		var e CustomTaskStartedEvent
+		return &e, json.Unmarshal(data, &e)
+	case string(EventCustomTaskInProgress):
+		var e CustomTaskInProgressEvent
+		return &e, json.Unmarshal(data, &e)
+	case string(EventCustomTaskCompleted):
+		var e CustomTaskCompletedEvent
+		return &e, json.Unmarshal(data, &e)
+	case string(EventCustomTaskFailed):
+		var e CustomTaskFailedEvent
+		return &e, json.Unmarshal(data, &e)
+	case string(EventCustomTaskTimedOut):
+		var e CustomTaskTimedOutEvent
+		return &e, json.Unmarshal(data, &e)
+	case string(EventCustomTaskCanceled):
+		var e CustomTaskCanceledEvent
+		return &e, json.Unmarshal(data, &e)
+	case string(EventActivityTaskStarted):
+		var e ActivityTaskStartedEvent
+		return &e, json.Unmarshal(data, &e)
+	case string(EventActivityTaskCompleted):
+		var e ActivityTaskCompletedEvent
+		return &e, json.Unmarshal(data, &e)
+	case string(EventActivityTaskRetrying):
+		var e ActivityTaskRetryingEvent
+		return &e, json.Unmarshal(data, &e)
+	case string(EventActivityTaskFailed):
+		var e ActivityTaskFailedEvent
+		return &e, json.Unmarshal(data, &e)
+	default:
+		var base eventBase
+		if err := json.Unmarshal(data, &base); err != nil {
+			return nil, fmt.Errorf("mistral: unmarshal workflow event base: %w", err)
+		}
+		return &UnknownEvent{
+			eventBase: base,
+			RawType:   probe.Type,
+			Raw:       json.RawMessage(data),
+		}, nil
+	}
+}
+
+// StreamPayload is a single SSE payload from the workflow event stream.
+type StreamPayload struct {
+	Data json.RawMessage `json:"data"`
+}
+
+// StreamWorkflowContext holds context for a workflow event stream.
+type StreamWorkflowContext struct {
+	WorkflowName string `json:"workflow_name"`
+	ExecutionID  string `json:"execution_id"`
+}
+
+// EventStreamParams holds query parameters for streaming workflow events.
+type EventStreamParams struct {
+	Source      *EventSource
+	LastEventID *string
+	Scope       *Scope
+}
+
+// EventListParams holds query parameters for listing workflow events.
+type EventListParams struct {
+	Source *EventSource
+	Scope  *Scope
+	Cursor *string
+	Limit  *int
+}
+
+// EventListResponse is the response from listing workflow events.
+type EventListResponse struct {
+	Events     []json.RawMessage `json:"events"`
+	NextCursor *string           `json:"next_cursor,omitempty"`
+}
diff --git a/workflow/event_test.go b/workflow/event_test.go
new file mode 100644
index 0000000..563ee5c
--- /dev/null
+++ b/workflow/event_test.go
@@ -0,0 +1,158 @@
+package workflow
+
+import (
+	"encoding/json"
+	"fmt"
+	"testing"
+)
+
+func TestUnmarshalEvent_WorkflowExecutionCompleted(t *testing.T) {
+	data := []byte(`{
+		"event_id": "evt-1",
+		"event_timestamp": 1711929600000000000,
+		"root_workflow_exec_id": "root-1",
+		"parent_workflow_exec_id": null,
+		"workflow_exec_id": "exec-1",
+		"workflow_run_id": "run-1",
+		"workflow_name": "my-workflow",
+		"event_type": "WORKFLOW_EXECUTION_COMPLETED",
+		"attributes": {"task_id": "t1", "result": {"value": {"answer": 42}, "type": "json"}}
+	}`)
+	event, err := UnmarshalEvent(data)
+	if err != nil {
+		t.Fatal(err)
+	}
+	e, ok := event.(*WorkflowExecutionCompletedEvent)
+	if !ok {
+		t.Fatalf("expected *WorkflowExecutionCompletedEvent, got %T", event)
+	}
+	if e.ID != "evt-1" {
+		t.Errorf("got ID %q", e.ID)
+	}
+	if e.WorkflowName != "my-workflow" {
+		t.Errorf("got WorkflowName %q", e.WorkflowName)
+	}
+	if e.EventType() != EventWorkflowCompleted {
+		t.Errorf("got EventType %q", e.EventType())
+	}
+}
+
+func TestUnmarshalEvent_CustomTaskStarted(t *testing.T) {
+	data := []byte(`{
+		"event_id": "evt-2",
+		"event_timestamp": 1711929600000000000,
+		"root_workflow_exec_id": "root-1",
+		"parent_workflow_exec_id": "parent-1",
+		"workflow_exec_id": "exec-1",
+		"workflow_run_id": "run-1",
+		"workflow_name": "my-workflow",
+		"event_type": "CUSTOM_TASK_STARTED",
+		"attributes": {}
+	}`)
+	event, err := UnmarshalEvent(data)
+	if err != nil {
+		t.Fatal(err)
+	}
+	e, ok := event.(*CustomTaskStartedEvent)
+	if !ok {
+		t.Fatalf("expected *CustomTaskStartedEvent, got %T", event)
+	}
+	parent := "parent-1"
+	if e.ParentWorkflowExecID == nil || *e.ParentWorkflowExecID != parent {
+		t.Errorf("expected parent %q, got %v", parent, e.ParentWorkflowExecID)
+	}
+}
+
+func TestUnmarshalEvent_ActivityTaskRetrying(t *testing.T) {
+	data := []byte(`{
+		"event_id": "evt-3",
+		"event_timestamp": 1711929600000000000,
+		"root_workflow_exec_id": "root-1",
+		"parent_workflow_exec_id": null,
+		"workflow_exec_id": "exec-1",
+		"workflow_run_id": "run-1",
+		"workflow_name": "my-workflow",
+		"event_type": "ACTIVITY_TASK_RETRYING",
+		"attributes": {}
+	}`)
+	event, err := UnmarshalEvent(data)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if _, ok := event.(*ActivityTaskRetryingEvent); !ok {
+		t.Fatalf("expected *ActivityTaskRetryingEvent, got %T", event)
+	}
+}
+
+func TestUnmarshalEvent_UnknownType(t *testing.T) {
+	data := []byte(`{
+		"event_id": "evt-4",
+		"event_timestamp": 1711929600000000000,
+		"root_workflow_exec_id": "root-1",
+		"parent_workflow_exec_id": null,
+		"workflow_exec_id": "exec-1",
+		"workflow_run_id": "run-1",
+		"workflow_name": "my-workflow",
+		"event_type": "FUTURE_EVENT_TYPE",
+		"attributes": {}
+	}`)
+	event, err := UnmarshalEvent(data)
+	if err != nil {
+		t.Fatal(err)
+	}
+	unk, ok := event.(*UnknownEvent)
+	if !ok {
+		t.Fatalf("expected *UnknownEvent, got %T", event)
+	}
+	if unk.RawType != "FUTURE_EVENT_TYPE" {
+		t.Errorf("got RawType %q", unk.RawType)
+	}
+}
+
+func TestUnmarshalEvent_AllTypes(t *testing.T) {
+	types := []struct {
+		eventType string
+		wantType  string
+	}{
+		{"WORKFLOW_EXECUTION_STARTED", "*workflow.WorkflowExecutionStartedEvent"},
+		{"WORKFLOW_EXECUTION_COMPLETED", "*workflow.WorkflowExecutionCompletedEvent"},
+		{"WORKFLOW_EXECUTION_FAILED", "*workflow.WorkflowExecutionFailedEvent"},
+		{"WORKFLOW_EXECUTION_CANCELED", "*workflow.WorkflowExecutionCanceledEvent"},
+		{"WORKFLOW_EXECUTION_CONTINUED_AS_NEW", "*workflow.WorkflowExecutionContinuedAsNewEvent"},
+		{"WORKFLOW_TASK_TIMED_OUT", "*workflow.WorkflowTaskTimedOutEvent"},
+		{"WORKFLOW_TASK_FAILED", "*workflow.WorkflowTaskFailedEvent"},
+		{"CUSTOM_TASK_STARTED", "*workflow.CustomTaskStartedEvent"},
+		{"CUSTOM_TASK_IN_PROGRESS", "*workflow.CustomTaskInProgressEvent"},
+		{"CUSTOM_TASK_COMPLETED", "*workflow.CustomTaskCompletedEvent"},
+		{"CUSTOM_TASK_FAILED", "*workflow.CustomTaskFailedEvent"},
+		{"CUSTOM_TASK_TIMED_OUT", "*workflow.CustomTaskTimedOutEvent"},
+		{"CUSTOM_TASK_CANCELED", "*workflow.CustomTaskCanceledEvent"},
+		{"ACTIVITY_TASK_STARTED", "*workflow.ActivityTaskStartedEvent"},
+		{"ACTIVITY_TASK_COMPLETED", "*workflow.ActivityTaskCompletedEvent"},
+		{"ACTIVITY_TASK_RETRYING", "*workflow.ActivityTaskRetryingEvent"},
+		{"ACTIVITY_TASK_FAILED", "*workflow.ActivityTaskFailedEvent"},
+	}
+	for _, tt := range types {
+		t.Run(tt.eventType, func(t *testing.T) {
+			data, _ := json.Marshal(map[string]any{
+				"event_id":                "evt",
+				"event_timestamp":         1711929600000000000,
+				"root_workflow_exec_id":   "root",
+				"parent_workflow_exec_id": nil,
+				"workflow_exec_id":        "exec",
+				"workflow_run_id":         "run",
+				"workflow_name":           "wf",
+				"event_type":              tt.eventType,
+				"attributes":              map[string]any{},
+			})
+			event, err := UnmarshalEvent(data)
+			if err != nil {
+				t.Fatal(err)
+			}
+			got := fmt.Sprintf("%T", event)
+			if got != tt.wantType {
+				t.Errorf("event_type %q: got %s, want %s", tt.eventType, got, tt.wantType)
+			}
+		})
+	}
+}