diff --git a/packages/mermaid/src/diagrams/sequence/types.ts b/packages/mermaid/src/diagrams/sequence/types.ts
new file mode 100644
index 0000000000..83ef0fc67a
--- /dev/null
+++ b/packages/mermaid/src/diagrams/sequence/types.ts
@@ -0,0 +1,85 @@
+export interface Box {
+  name: string;
+  wrap: boolean;
+  fill: string;
+  actorKeys: string[];
+}
+
+export interface Actor {
+  box?: Box;
+  name: string;
+  description: string;
+  wrap: boolean;
+  prevActor?: string;
+  nextActor?: string;
+  links: Record<string, unknown>;
+  properties: Record<string, unknown>;
+  actorCnt: number | null;
+  rectData: unknown;
+  type: string;
+}
+
+export interface Message {
+  from?: { actor: string };
+  to?: { actor: string };
+  message:
+    | string
+    | {
+        start: number;
+        step: number;
+        visible: boolean;
+      };
+  wrap: boolean;
+  answer?: unknown;
+  type?: number;
+  activate?: boolean;
+  placement?: string;
+}
+
+export interface AddMessageParams {
+  from: string;
+  to: string;
+  msg: string;
+  signalType: number;
+  type:
+    | 'addMessage'
+    | 'sequenceIndex'
+    | 'addParticipant'
+    | 'createParticipant'
+    | 'destroyParticipant'
+    | 'activeStart'
+    | 'activeEnd'
+    | 'addNote'
+    | 'addLinks'
+    | 'addALink'
+    | 'addProperties'
+    | 'addDetails'
+    | 'boxStart'
+    | 'boxEnd'
+    | 'loopStart'
+    | 'loopEnd'
+    | 'rectStart'
+    | 'rectEnd'
+    | 'optStart'
+    | 'optEnd'
+    | 'altStart'
+    | 'else'
+    | 'altEnd'
+    | 'setAccTitle'
+    | 'parStart'
+    | 'parAnd'
+    | 'parEnd'
+    | 'and'
+    | 'criticalStart'
+    | 'criticalOption'
+    | 'option'
+    | 'criticalEnd'
+    | 'breakStart'
+    | 'breakEnd'
+    | 'parOverStart'
+    | 'parOverEnd'
+    | 'parOverAnd'
+    | 'parOverEnd';
+
+  activate: boolean;
+}