diff --git a/packages/db-types/src/index.ts b/packages/db-types/src/index.ts
index 7c9e6c1..5684173 100644
--- a/packages/db-types/src/index.ts
+++ b/packages/db-types/src/index.ts
@@ -612,6 +612,41 @@ export type Database = {
         };
         Relationships: [];
       };
+      conversation_games: {
+        Row: {
+          id: string;
+          conversation_id: string;
+          game_type: 'ttt' | 'c4';
+          state: { kind: 'ttt' | 'c4'; board: Array<number | null> };
+          players: [string, string];
+          current_turn_user_id: string | null;
+          winner_user_id: string | null;
+          created_at: string;
+          finished_at: string | null;
+        };
+        Insert: {
+          id?: string;
+          conversation_id: string;
+          game_type: 'ttt' | 'c4';
+          state: { kind: 'ttt' | 'c4'; board: Array<number | null> };
+          players: [string, string];
+          current_turn_user_id: string | null;
+          winner_user_id?: string | null;
+          created_at?: string;
+          finished_at?: string | null;
+        };
+        Update: {
+          id?: string;
+          conversation_id?: string;
+          game_type?: 'ttt' | 'c4';
+          state?: { kind: 'ttt' | 'c4'; board: Array<number | null> };
+          players?: [string, string];
+          current_turn_user_id?: string | null;
+          winner_user_id?: string | null;
+          finished_at?: string | null;
+        };
+        Relationships: [];
+      };
     }
     Views: {
       [_ in never]: never
@@ -620,6 +655,10 @@ export type Database = {
       accept_dm: { Args: { conversation_id: string }; Returns: undefined }
       are_friends: { Args: { a: string; b: string }; Returns: boolean }
       revoke_device: { Args: { p_device_id: string }; Returns: undefined }
+      game_make_move: {
+        Args: { p_game_id: string; p_move: object };
+        Returns: { kind: 'ttt' | 'c4'; board: Array<number | null> };
+      }
       attachment_object_conv_id: {
         Args: { object_name: string }
         Returns: string
diff --git a/packages/shared/src/chat/attachments.ts b/packages/shared/src/chat/attachments.ts
index 6aa6f64..e8e45ca 100644
--- a/packages/shared/src/chat/attachments.ts
+++ b/packages/shared/src/chat/attachments.ts
@@ -88,12 +88,20 @@ export interface WatchTogetherPayload {
   session_id: string;
 }
 
+export interface GamePayload {
+  v: 1;
+  type: 'game';
+  game_id: string;
+  game_type: 'ttt' | 'c4';
+}
+
 export type MessagePayload =
   | TextMessagePayload
   | CallEventPayload
   | PollPayload
   | WhiteboardPayload
-  | WatchTogetherPayload;
+  | WatchTogetherPayload
+  | GamePayload;
 
 export type ParsedMessagePayload =
   | {
@@ -120,6 +128,11 @@ export type ParsedMessagePayload =
   | {
       kind: 'watch_together';
       sessionId: string;
+    }
+  | {
+      kind: 'game';
+      gameId: string;
+      gameType: 'ttt' | 'c4';
     };
 
 export function serializeMessagePayload(payload: MessagePayload): string {
@@ -190,6 +203,12 @@ export function parseMessagePayload(raw: string | null): ParsedMessagePayload {
           : '';
         return { kind: 'watch_together', sessionId: id };
       }
+      if (obj.type === 'game') {
+        const p = obj as Partial<GamePayload>;
+        const id = typeof p.game_id === 'string' && p.game_id.length > 0 ? p.game_id : '';
+        const t = p.game_type === 'ttt' || p.game_type === 'c4' ? p.game_type : 'ttt';
+        return { kind: 'game', gameId: id, gameType: t };
+      }
       const t = obj as TextMessagePayload;
       return {
         kind: 'text',
diff --git a/packages/shared/src/chat/games.test.ts b/packages/shared/src/chat/games.test.ts
new file mode 100644
index 0000000..25212f0
--- /dev/null
+++ b/packages/shared/src/chat/games.test.ts
@@ -0,0 +1,79 @@
+import { describe, expect, it } from 'vitest';
+
+import {
+  c4DropRow,
+  c4WinningCells,
+  emptyC4Board,
+  emptyTttBoard,
+  isBoardFull,
+  tttWinningLine,
+  type Cell,
+} from './games';
+
+describe('tttWinningLine', () => {
+  it('detects a row win', () => {
+    const b: Cell[] = [0, 0, 0, null, null, null, null, null, null];
+    expect(tttWinningLine(b)).toEqual([0, 1, 2]);
+  });
+
+  it('detects a diagonal win', () => {
+    const b: Cell[] = [1, null, null, null, 1, null, null, null, 1];
+    expect(tttWinningLine(b)).toEqual([0, 4, 8]);
+  });
+
+  it('returns null when no winner', () => {
+    expect(tttWinningLine(emptyTttBoard())).toBeNull();
+    const mixed: Cell[] = [0, 1, 0, 1, 0, 1, 1, 0, 1];
+    expect(tttWinningLine(mixed)).toBeNull();
+  });
+});
+
+describe('c4WinningCells', () => {
+  it('detects a horizontal win', () => {
+    const b = emptyC4Board();
+    b[35] = 1; b[36] = 1; b[37] = 1; b[38] = 1;
+    expect(c4WinningCells(b)).toEqual([35, 36, 37, 38]);
+  });
+
+  it('detects a vertical win', () => {
+    const b = emptyC4Board();
+    b[14] = 0; b[21] = 0; b[28] = 0; b[35] = 0;
+    expect(c4WinningCells(b)).toEqual([14, 21, 28, 35]);
+  });
+
+  it('detects a diagonal ↘ win', () => {
+    const b = emptyC4Board();
+    b[14] = 1; b[22] = 1; b[30] = 1; b[38] = 1;
+    expect(c4WinningCells(b)).toEqual([14, 22, 30, 38]);
+  });
+
+  it('returns null when no winner', () => {
+    expect(c4WinningCells(emptyC4Board())).toBeNull();
+  });
+});
+
+describe('c4DropRow', () => {
+  it('returns the bottom row on an empty column', () => {
+    expect(c4DropRow(emptyC4Board(), 0)).toBe(5);
+  });
+
+  it('stacks on top of an existing piece', () => {
+    const b = emptyC4Board();
+    b[35] = 0;
+    expect(c4DropRow(b, 0)).toBe(4);
+  });
+
+  it('returns -1 when the column is full', () => {
+    const b = emptyC4Board();
+    for (let r = 0; r < 6; r++) b[r * 7 + 3] = 0;
+    expect(c4DropRow(b, 3)).toBe(-1);
+  });
+});
+
+describe('isBoardFull', () => {
+  it('true for a fully filled board, false otherwise', () => {
+    expect(isBoardFull(emptyTttBoard())).toBe(false);
+    const filled: Cell[] = [0, 1, 0, 1, 0, 1, 1, 0, 1];
+    expect(isBoardFull(filled)).toBe(true);
+  });
+});
diff --git a/packages/shared/src/chat/games.ts b/packages/shared/src/chat/games.ts
new file mode 100644
index 0000000..ec240af
--- /dev/null
+++ b/packages/shared/src/chat/games.ts
@@ -0,0 +1,165 @@
+import type { AppSupabaseClient } from '../supabase/client';
+
+export type GameType = 'ttt' | 'c4';
+export type Cell = 0 | 1 | null;
+
+export const TTT_CELLS = 9;
+export const C4_ROWS = 6;
+export const C4_COLS = 7;
+export const C4_CELLS = C4_ROWS * C4_COLS;
+
+export const TTT_LINES: ReadonlyArray<readonly [number, number, number]> = [
+  [0, 1, 2], [3, 4, 5], [6, 7, 8],
+  [0, 3, 6], [1, 4, 7], [2, 5, 8],
+  [0, 4, 8], [2, 4, 6],
+];
+
+export interface GameRecord {
+  id: string;
+  conversationId: string;
+  gameType: GameType;
+  state: { kind: GameType; board: Cell[] };
+  players: [string, string];
+  currentTurnUserId: string | null;
+  winnerUserId: string | null;
+  createdAt: string;
+  finishedAt: string | null;
+}
+
+export function emptyTttBoard(): Cell[] {
+  return new Array(TTT_CELLS).fill(null);
+}
+
+export function emptyC4Board(): Cell[] {
+  return new Array(C4_CELLS).fill(null);
+}
+
+export function tttWinningLine(board: Cell[]): readonly [number, number, number] | null {
+  for (const line of TTT_LINES) {
+    const a = board[line[0]];
+    const b = board[line[1]];
+    const c = board[line[2]];
+    if (a !== null && a === b && b === c) return line;
+  }
+  return null;
+}
+
+export function c4WinningCells(board: Cell[]): readonly number[] | null {
+  const directions: Array<[number, number]> = [
+    [0, 1], [1, 0], [1, 1], [1, -1],
+  ];
+  for (let r = 0; r < C4_ROWS; r++) {
+    for (let c = 0; c < C4_COLS; c++) {
+      const base = board[r * C4_COLS + c];
+      if (base === null) continue;
+      for (const [dr, dc] of directions) {
+        const rEnd = r + dr * 3;
+        const cEnd = c + dc * 3;
+        if (rEnd < 0 || rEnd >= C4_ROWS || cEnd < 0 || cEnd >= C4_COLS) continue;
+        let ok = true;
+        const cells: number[] = [r * C4_COLS + c];
+        for (let i = 1; i < 4; i++) {
+          const idx = (r + dr * i) * C4_COLS + (c + dc * i);
+          if (board[idx] !== base) { ok = false; break; }
+          cells.push(idx);
+        }
+        if (ok) return cells;
+      }
+    }
+  }
+  return null;
+}
+
+export function isBoardFull(board: Cell[]): boolean {
+  return board.every((c) => c !== null);
+}
+
+export function c4DropRow(board: Cell[], column: number): number {
+  for (let r = C4_ROWS - 1; r >= 0; r--) {
+    if (board[r * C4_COLS + column] === null) return r;
+  }
+  return -1;
+}
+
+export async function createGame(
+  client: AppSupabaseClient,
+  params: { conversationId: string; gameType: GameType; opponentUserId: string },
+): Promise<GameRecord> {
+  const { data: session } = await client.auth.getUser();
+  if (!session.user) throw new Error('not authenticated');
+  const board = params.gameType === 'ttt' ? emptyTttBoard() : emptyC4Board();
+  const state = { kind: params.gameType, board };
+  const players: [string, string] = [session.user.id, params.opponentUserId];
+  const { data, error } = await client
+    .from('conversation_games')
+    .insert({
+      conversation_id: params.conversationId,
+      game_type: params.gameType,
+      state,
+      players,
+      current_turn_user_id: session.user.id,
+    })
+    .select(
+      'id, conversation_id, game_type, state, players, current_turn_user_id, winner_user_id, created_at, finished_at',
+    )
+    .single();
+  if (error) throw error;
+  return mapRow(data);
+}
+
+export async function getGame(
+  client: AppSupabaseClient,
+  gameId: string,
+): Promise<GameRecord | null> {
+  const { data, error } = await client
+    .from('conversation_games')
+    .select(
+      'id, conversation_id, game_type, state, players, current_turn_user_id, winner_user_id, created_at, finished_at',
+    )
+    .eq('id', gameId)
+    .maybeSingle();
+  if (error) throw error;
+  return data ? mapRow(data) : null;
+}
+
+export async function makeGameMove(
+  client: AppSupabaseClient,
+  params: { gameId: string; move: object },
+): Promise<void> {
+  const { error } = await client.rpc('game_make_move', {
+    p_game_id: params.gameId,
+    p_move: params.move,
+  });
+  if (error) throw new Error(error.message);
+}
+
+function mapRow(row: {
+  id: string;
+  conversation_id: string;
+  game_type: string;
+  state: unknown;
+  players: unknown;
+  current_turn_user_id: string | null;
+  winner_user_id: string | null;
+  created_at: string;
+  finished_at: string | null;
+}): GameRecord {
+  const rawState = (row.state ?? {}) as { kind?: string; board?: unknown };
+  const kind: GameType = rawState.kind === 'c4' ? 'c4' : 'ttt';
+  const rawBoard = Array.isArray(rawState.board) ? rawState.board : [];
+  const board: Cell[] = rawBoard.map((c) =>
+    typeof c === 'number' && (c === 0 || c === 1) ? (c as Cell) : null,
+  );
+  const players = Array.isArray(row.players) ? row.players : [];
+  return {
+    id: row.id,
+    conversationId: row.conversation_id,
+    gameType: row.game_type === 'c4' ? 'c4' : 'ttt',
+    state: { kind, board },
+    players: [String(players[0] ?? ''), String(players[1] ?? '')],
+    currentTurnUserId: row.current_turn_user_id,
+    winnerUserId: row.winner_user_id,
+    createdAt: row.created_at,
+    finishedAt: row.finished_at,
+  };
+}
diff --git a/packages/shared/src/chat/index.ts b/packages/shared/src/chat/index.ts
index b58ae92..3f84a4b 100644
--- a/packages/shared/src/chat/index.ts
+++ b/packages/shared/src/chat/index.ts
@@ -13,6 +13,7 @@ export * from './viewOnceAttachments';
 export * from './whiteboards';
 export * from './soundboards';
 export * from './watchTogether';
+export * from './games';
 
 // ----- RPC wrappers ---------------------------------------------------------