fix: change GAME_ROUNDS from strings to numbers

apps/api/src/controllers/gameController.test.ts

@@ -60,7 +60,7 @@ const validBody = {
   target_language: "it",
   pos: "noun",
   difficulty: "easy",
-  rounds: "3",
+  rounds: 3,
 };
 
 const fakeTerms = [
@@ -177,4 +177,22 @@ describe("POST /api/v1/game/answer", () => {
     expect(body.success).toBe(false);
     expect(body.error).toContain("Question not found");
   });
+
+  it("returns 400 when a field has an invalid value", async () => {
+    const res = await request(app)
+      .post("/api/v1/game/start")
+      .send({ ...validBody, difficulty: "impossible" });
+    const body = res.body as ErrorResponse;
+    expect(res.status).toBe(400);
+    expect(body.success).toBe(false);
+  });
+
+  it("returns 400 when rounds has an invalid value", async () => {
+    const res = await request(app)
+      .post("/api/v1/game/start")
+      .send({ ...validBody, rounds: "invalid" });
+    const body = res.body as ErrorResponse;
+    expect(res.status).toBe(400);
+    expect(body.success).toBe(false);
+  });
 });

apps/api/src/services/gameService.test.ts

@@ -14,7 +14,7 @@ const validRequest: GameRequest = {
   target_language: "it",
   pos: "noun",
   difficulty: "easy",
-  rounds: "3",
+  rounds: 3,
 };
 
 const fakeTerms = [

apps/api/src/services/gameService.ts

@@ -21,7 +21,7 @@ export const createGameSession = async (
     request.target_language,
     request.pos,
     request.difficulty,
-    Number(request.rounds),
+    request.rounds,
   );
 
   const answerKey = new Map<string, number>();

apps/web/src/components/game/GameSetup.tsx

@@ -24,19 +24,19 @@ const LABELS: Record<string, string> = {
 
 type GameSetupProps = { onStart: (settings: GameRequest) => void };
 
-type SettingGroupProps = {
+type SettingGroupProps<T extends string | number> = {
   label: string;
-  options: readonly string[];
-  selected: string;
-  onSelect: (value: string) => void;
+  options: readonly T[];
+  selected: T;
+  onSelect: (value: T) => void;
 };
 
-const SettingGroup = ({
+const SettingGroup = <T extends string | number>({
   label,
   options,
   selected,
   onSelect,
-}: SettingGroupProps) => (
+}: SettingGroupProps<T>) => (
   <div className="w-full">
     <p className="text-xs font-bold tracking-widest uppercase text-(--color-primary) mb-2">
       {label}
@@ -52,7 +52,7 @@ const SettingGroup = ({
               : "bg-white text-(--color-primary-dark) border-(--color-primary-light) hover:bg-(--color-surface) hover:-translate-y-0.5 active:translate-y-0"
           }`}
         >
-          {LABELS[option] ?? option}
+          {LABELS[String(option)] ?? option}
         </button>
       ))}
     </div>
@@ -68,7 +68,7 @@ export const GameSetup = ({ onStart }: GameSetupProps) => {
   );
   const [pos, setPos] = useState<string>(SUPPORTED_POS[0]);
   const [difficulty, setDifficulty] = useState<string>(DIFFICULTY_LEVELS[0]);
-  const [rounds, setRounds] = useState<string>(GAME_ROUNDS[0]);
+  const [rounds, setRounds] = useState<number>(GAME_ROUNDS[0]);
 
   const handleSourceLanguage = (value: string) => {
     if (value === targetLanguage) {

documentation/roasts/gameService.md

@@ -151,7 +151,7 @@ export const evaluateAnswer = async (...) => { ... };
 
 ---
 
-## 4. `rounds` is typed as a string
+
 
 **Problem**
 

documentation/tickets/t00002.md

@@ -0,0 +1,149 @@
+# ADR: Change GAME_ROUNDS from strings to numbers
+
+## Status
+
+Accepted
+
+## Date
+
+2026-04-28
+
+## Context
+
+`GAME_ROUNDS` in `packages/shared/src/constants.ts` was typed as `["3", "10"] as const`, making `GameRounds` a string union (`"3" | "10"`). This meant `gameService.ts` had to cast the value with `Number(request.rounds)` deep in business logic — a type conversion happening far from the boundary where data enters the system. The type system was lying: `rounds` was described as a string everywhere but used as a number where it mattered.
+
+## Decision
+
+Change `GAME_ROUNDS` to `[3, 10] as const` and update the Zod schema to use `z.literal(GAME_ROUNDS)` instead of `z.enum(GAME_ROUNDS)`. The single source of truth remains `constants.ts` — adding a new round count (e.g. `20`) requires only editing that file.
+
+## Options considered
+
+### Option A — Numbers everywhere ✅
+
+Change `GAME_ROUNDS` to `[3, 10] as const`. Use `z.literal(GAME_ROUNDS)` in the schema. Update the frontend component state and `SettingGroup` props. Drop `Number()` cast in the service.
+
+Chosen because: JSON carries numbers natively, both ends of the wire are owned by this codebase, and type conversions belong at the boundary — not inside business logic.
+
+### Option B — Keep strings, accept the cast
+
+Leave `GAME_ROUNDS` as `["3", "10"]`. The `Number()` cast stays in `gameService.ts`.
+
+Rejected because: it pushes type conversion into business logic and makes the inferred `GameRequest` type misleading. The cast has to live somewhere — the schema boundary is the right place.
+
+### Option C — Coerce at the schema boundary
+
+Keep `GAME_ROUNDS` as numbers but use `z.coerce.number().pipe(z.literal(GAME_ROUNDS))` so the frontend can keep sending strings.
+
+Rejected because: coercion is for untrusted or uncontrolled inputs (form fields, query params, third-party clients). We control both ends of the wire. Coercing a self-inflicted type mismatch is treating a wound we gave ourselves.
+
+## Consequences
+
+- `GameRounds` is now `3 | 10` instead of `"3" | "10"`
+- `Number(request.rounds)` cast removed from `gameService.ts`
+- `SettingGroup` in `GameSetup.tsx` now accepts `string | number` options
+- `useState<string>` for rounds changed to `useState<number>`
+- Adding a new round count requires only editing `GAME_ROUNDS` in `constants.ts`
+- `z.enum` cannot be used for number literals — `z.literal` must be used instead (this is a Zod constraint, not a project convention)
+
+## Affected files
+
+- `packages/shared/src/constants.ts`
+- `packages/shared/src/schemas/game.ts`
+- `apps/api/src/services/gameService.ts`
+- `apps/api/src/services/gameService.test.ts`
+- `apps/api/src/controllers/gameController.test.ts`
+- `apps/web/src/components/game/GameSetup.tsx`
+
+## References
+
+- [Zod literals](https://zod.dev/?id=literals)
+
+---
+
+## Setup guide / implementation notes
+
+1. In `packages/shared/src/constants.ts`, change:
+
+   ```ts
+   export const GAME_ROUNDS = ["3", "10"] as const;
+   ```
+
+   to:
+
+   ```ts
+   export const GAME_ROUNDS = [3, 10] as const;
+   ```
+
+2. In `packages/shared/src/schemas/game.ts`, change:
+
+   ```ts
+   rounds: z.enum(GAME_ROUNDS),
+   ```
+
+   to:
+
+   ```ts
+   rounds: z.literal(GAME_ROUNDS),
+   ```
+
+3. In `apps/api/src/services/gameService.ts`, change:
+
+   ```ts
+   Number(request.rounds),
+   ```
+
+   to:
+
+   ```ts
+   request.rounds,
+   ```
+
+4. In `apps/api/src/services/gameService.test.ts`, change:
+
+   ```ts
+   rounds: "3",
+   ```
+
+   to:
+
+   ```ts
+   rounds: 3,
+   ```
+
+5. In `apps/api/src/controllers/gameController.test.ts`, change:
+
+   ```ts
+   rounds: "3",
+   ```
+
+   to:
+
+   ```ts
+   rounds: 3,
+   ```
+
+   Also add a pinning test before the refactor:
+
+   ```ts
+   it("returns 400 when rounds has an invalid value", async () => {
+     const res = await request(app)
+       .post("/api/v1/game/start")
+       .send({ ...validBody, rounds: "invalid" });
+     expect(res.status).toBe(400);
+     expect(res.body.success).toBe(false);
+   });
+   ```
+
+6. In `apps/web/src/components/game/GameSetup.tsx`:
+   - Update `SettingGroup` props to accept `string | number`:
+  
+     ```ts
+     type SettingGroupProps = {
+       options: readonly (string | number)[];
+       selected: string | number;
+       onSelect: (value: string | number) => void;
+     };
+     ```
+
+   - Update `LABELS` lookup to `LABELS[String(option)]`
+   - Change rounds state from `useState<string>` to `useState<number>`

packages/shared/src/constants.ts

@@ -4,7 +4,7 @@ export type SupportedLanguageCode = (typeof SUPPORTED_LANGUAGE_CODES)[number];
 export const SUPPORTED_POS = ["noun", "verb", "adjective", "adverb"] as const;
 export type SupportedPos = (typeof SUPPORTED_POS)[number];
 
-export const GAME_ROUNDS = ["3", "10"] as const;
+export const GAME_ROUNDS = [3, 10] as const;
 export type GameRounds = (typeof GAME_ROUNDS)[number];
 
 export const CEFR_LEVELS = ["A1", "A2", "B1", "B2", "C1", "C2"] as const;

packages/shared/src/schemas/game.ts

@@ -12,7 +12,7 @@ export const GameRequestSchema = z.object({
   target_language: z.enum(SUPPORTED_LANGUAGE_CODES),
   pos: z.enum(SUPPORTED_POS),
   difficulty: z.enum(DIFFICULTY_LEVELS),
-  rounds: z.enum(GAME_ROUNDS),
+  rounds: z.literal(GAME_ROUNDS),
 });
 
 export type GameRequest = z.infer<typeof GameRequestSchema>;