diff --git a/engine/docs/schema/protocol.schema.json b/engine/docs/schema/protocol.schema.json
index 1baa04b0..25b307b3 100644
--- a/engine/docs/schema/protocol.schema.json
+++ b/engine/docs/schema/protocol.schema.json
@@ -3,7 +3,7 @@
   "$id": "https://github.com/sheathedsharp/option-berth/engine/docs/schema/protocol.schema.json",
   "title": "option-berth daemon protocol",
   "description": "Generated from the Go types in internal/state and internal/daemon/rpc. Do not edit by hand; run `go generate ./...`.",
-  "protocol_version": "2.0.0",
+  "protocol_version": "2.1.0",
   "definitions": {
     "ChangeGroup": {
       "properties": {
diff --git a/engine/internal/daemon/rpc/types.go b/engine/internal/daemon/rpc/types.go
index 2ad69129..91fa08b6 100644
--- a/engine/internal/daemon/rpc/types.go
+++ b/engine/internal/daemon/rpc/types.go
@@ -17,7 +17,11 @@ const Version = "2.0"
 //
 // 2.0.0 removed two fields no handler read: Selector.Key and the host envelope
 // that every params type used to embed.
-const ProtocolVersion = "2.0.0"
+//
+// 2.1.0 added the groups.code method and GroupsKillParams.ExpectRuns. Both are
+// additive, so a client must gate them on the daemon's advertised capabilities
+// (CapabilityKillExpectRuns) rather than on this version.
+const ProtocolVersion = "2.1.0"
 
 // Request is a client call. ID is raw so a client can use numbers or strings.
 type Request struct {