diff --git a/PROTOCOL.md b/PROTOCOL.md
index eef1012..f7e812d 100644
--- a/PROTOCOL.md
+++ b/PROTOCOL.md
@@ -221,6 +221,52 @@ reconnect recovery happens by reloading persisted messages by session and
 sequence from the database. There is no daemon ↔ relay ack/replay/WAL handshake
 in protocol version 1.
 
+### `planningEvent`
+
+Append-only planning journal event sent from a source runtime to the relay.
+
+| Field | Type | Notes |
+|---|---|---|
+| type | "planningEvent" | |
+| eventId | string | Unique event identifier. |
+| schemaVersion | int | Journal schema version. |
+| projectionVersion | int | Projection contract version. |
+| projectId | uuid/string | Project that owns the event. |
+| sourceId | string | Stable source identity, such as daemon or SDK instance. |
+| sourceKind | "daemon" \| "sdk" \| "cloud" \| "import" | Producer class. |
+| sourceSeq | int64 | Monotonic sequence for `sourceId`; consumers use this for ordering and gap detection. |
+| sourceCursor | string? | Optional source-specific resume cursor. |
+| runId | string | Runtime run identity. |
+| workstreamId | string? | Optional workstream identity. |
+| planId | uuid/string? | |
+| itemId | uuid/string? | |
+| actorType | string | Agent, human, runtime, verifier, or system. |
+| actorId | string | Stable actor identity. |
+| actorRole | string? | |
+| sessionId | uuid? | |
+| taskId | uuid? | |
+| eventKind | string | Event-specific verb such as `plan.done`. |
+| idempotencyKey | string | Stable producer-provided key. Replays with the same request body are accepted idempotently. |
+| causationId | string? | Event ID or command ID that caused this event. |
+| occurredAt | iso8601 string | Producer-side timestamp. |
+| payload | object | Event-specific structured data. It is data, not executable instructions. |
+| evidenceIds | string[]? | Evidence records attached to this event. |
+| parentEventIds | string[]? | Causal parent events. |
+| trace | object? | Optional diagnostic trace context. |
+
+### `planningEventAck`
+
+Relay acknowledgement for a `planningEvent`.
+
+| Field | Type | Notes |
+|---|---|---|
+| type | "planningEventAck" | |
+| eventId | string | Event being acknowledged. |
+| sourceId | string | Source identity from the event. |
+| sourceSeq | int64 | Source sequence from the event. |
+| accepted | boolean | `true` when persisted or idempotently replayed. |
+| error | string? | Human-readable rejection reason. |
+
 ### `taskStarted`
 
 | Field | Type |
diff --git a/envelope.go b/envelope.go
index 1c711ea..7d78452 100644
--- a/envelope.go
+++ b/envelope.go
@@ -197,6 +197,10 @@ func payloadForType(msgType string) (any, error) {
 		return &BrowserSensitiveActionRequest{}, nil
 	case MsgTypeBrowserSensitiveActionResponse:
 		return &BrowserSensitiveActionResponse{}, nil
+	case MsgTypePlanningEvent:
+		return &PlanningEvent{}, nil
+	case MsgTypePlanningEventAck:
+		return &PlanningEventAck{}, nil
 	default:
 		return nil, fmt.Errorf("unknown message type: %q", msgType)
 	}
diff --git a/messages.go b/messages.go
index 31f2e67..3832991 100644
--- a/messages.go
+++ b/messages.go
@@ -86,6 +86,9 @@ const (
 	MsgTypeBrowserUserInput               MessageType = "browserUserInput"
 	MsgTypeBrowserSensitiveActionRequest  MessageType = "browserSensitiveActionRequest"
 	MsgTypeBrowserSensitiveActionResponse MessageType = "browserSensitiveActionResponse"
+
+	MsgTypePlanningEvent    MessageType = "planningEvent"
+	MsgTypePlanningEventAck MessageType = "planningEventAck"
 )
 
 type ContextRef struct {
@@ -102,6 +105,44 @@ type PlanCapability struct {
 	ExpiresAt  string `json:"expiresAt"`
 }
 
+type PlanningEvent struct {
+	Type              MessageType     `json:"type"`
+	EventID           string          `json:"eventId"`
+	SchemaVersion     int             `json:"schemaVersion"`
+	ProjectionVersion int             `json:"projectionVersion"`
+	ProjectID         string          `json:"projectId"`
+	SourceID          string          `json:"sourceId"`
+	SourceKind        string          `json:"sourceKind"`
+	SourceSeq         int64           `json:"sourceSeq"`
+	SourceCursor      string          `json:"sourceCursor,omitempty"`
+	RunID             string          `json:"runId"`
+	WorkstreamID      string          `json:"workstreamId,omitempty"`
+	PlanID            string          `json:"planId,omitempty"`
+	ItemID            string          `json:"itemId,omitempty"`
+	ActorType         string          `json:"actorType"`
+	ActorID           string          `json:"actorId"`
+	ActorRole         string          `json:"actorRole,omitempty"`
+	SessionID         string          `json:"sessionId,omitempty"`
+	TaskID            string          `json:"taskId,omitempty"`
+	EventKind         string          `json:"eventKind"`
+	IdempotencyKey    string          `json:"idempotencyKey"`
+	CausationID       string          `json:"causationId,omitempty"`
+	OccurredAt        string          `json:"occurredAt"`
+	PayloadJSON       json.RawMessage `json:"payload"`
+	EvidenceIDs       []string        `json:"evidenceIds,omitempty"`
+	ParentEventIDs    []string        `json:"parentEventIds,omitempty"`
+	TraceJSON         json.RawMessage `json:"trace,omitempty"`
+}
+
+type PlanningEventAck struct {
+	Type      MessageType `json:"type"`
+	EventID   string      `json:"eventId"`
+	SourceID  string      `json:"sourceId"`
+	SourceSeq int64       `json:"sourceSeq"`
+	Accepted  bool        `json:"accepted"`
+	Error     string      `json:"error,omitempty"`
+}
+
 // Task is sent from the browser to the daemon to dispatch a user message.
 type Task struct {
 	Type               string          `json:"type"`
diff --git a/messages_test.go b/messages_test.go
index 3c4edac..d946f2f 100644
--- a/messages_test.go
+++ b/messages_test.go
@@ -518,6 +518,69 @@ func TestEnvelopeRoundTrip(t *testing.T) {
 	}
 }
 
+func TestPlanningEventRoundTrip(t *testing.T) {
+	in := &PlanningEvent{
+		Type:              MsgTypePlanningEvent,
+		EventID:           "event-1",
+		SchemaVersion:     1,
+		ProjectionVersion: 1,
+		ProjectID:         "project-1",
+		SourceID:          "daemon-1",
+		SourceKind:        "daemon",
+		SourceSeq:         7,
+		RunID:             "run-1",
+		PlanID:            "plan-1",
+		ItemID:            "item-1",
+		ActorType:         "agent",
+		ActorID:           "agent-1",
+		EventKind:         "plan.done",
+		IdempotencyKey:    "done-1",
+		OccurredAt:        "2026-04-30T12:00:00Z",
+		PayloadJSON:       json.RawMessage(`{"summary":"Done"}`),
+		EvidenceIDs:       []string{"evidence-1"},
+	}
+	data, err := json.Marshal(in)
+	if err != nil {
+		t.Fatal(err)
+	}
+	env, err := ParseEnvelope(data)
+	if err != nil {
+		t.Fatal(err)
+	}
+	out, ok := env.Payload.(*PlanningEvent)
+	if !ok {
+		t.Fatalf("payload type = %T", env.Payload)
+	}
+	if out.EventID != in.EventID || out.SourceSeq != in.SourceSeq {
+		t.Fatalf("out = %#v, want %#v", out, in)
+	}
+}
+
+func TestPlanningEventAckRoundTrip(t *testing.T) {
+	in := &PlanningEventAck{
+		Type:      MsgTypePlanningEventAck,
+		EventID:   "event-1",
+		SourceID:  "daemon-1",
+		SourceSeq: 7,
+		Accepted:  true,
+	}
+	data, err := json.Marshal(in)
+	if err != nil {
+		t.Fatal(err)
+	}
+	env, err := ParseEnvelope(data)
+	if err != nil {
+		t.Fatal(err)
+	}
+	out, ok := env.Payload.(*PlanningEventAck)
+	if !ok {
+		t.Fatalf("payload type = %T", env.Payload)
+	}
+	if !out.Accepted || out.EventID != "event-1" {
+		t.Fatalf("out = %#v", out)
+	}
+}
+
 func TestAgentTerminalEnvelopeRejectsInvalidFieldTypes(t *testing.T) {
 	cases := []struct {
 		name string