diff --git a/packages/server/src/bot/brain.ts b/packages/server/src/bot/brain.ts
new file mode 100644
index 0000000..7366684
--- /dev/null
+++ b/packages/server/src/bot/brain.ts
@@ -0,0 +1,46 @@
+import type {
+  Announcement,
+  BoardView,
+  Color,
+  PromotionType,
+  Square,
+} from '@blind-chess/shared';
+import type { ModeratorText } from '@blind-chess/shared';
+
+export interface CandidateMove {
+  from: Square;
+  to: Square;
+  promotion?: PromotionType;
+}
+
+export interface AttemptHistoryEntry {
+  move: CandidateMove;
+  rejection: ModeratorText;
+}
+
+export interface BrainInput {
+  view: BoardView;
+  newAnnouncements: Announcement[];
+  legalCandidates: CandidateMove[];
+  attemptHistory: AttemptHistoryEntry[];
+  drawOfferFromOpponent: boolean;
+  ply: number;
+}
+
+export type BrainAction =
+  | { type: 'commit'; from: Square; to: Square; promotion?: PromotionType }
+  | { type: 'resign' }
+  | { type: 'offer-draw' }
+  | { type: 'respond-draw'; accept: boolean };
+
+export interface BrainInitArgs {
+  color: Color;
+  mode: 'blind' | 'vanilla';
+  gameId: string;
+}
+
+export interface Brain {
+  init(args: BrainInitArgs): Promise<void>;
+  decide(input: BrainInput): Promise<BrainAction>;
+  dispose?(): Promise<void>;
+}
diff --git a/packages/server/src/bot/index.ts b/packages/server/src/bot/index.ts
new file mode 100644
index 0000000..d86506f
--- /dev/null
+++ b/packages/server/src/bot/index.ts
@@ -0,0 +1,4 @@
+export type {
+  Brain, BrainInput, BrainAction, BrainInitArgs,
+  CandidateMove, AttemptHistoryEntry,
+} from './brain.js';