Player minimum of 3 to start a game or scene

Enforced server-side in lobby/start and confirm_scene_setup via
crud_base.has_min_players; Dev Mode bypasses it so local single-player
testing still works. Lobby and scene-setup UIs show a player-count
message instead of the start button when below the minimum.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

TODO.md

@@ -18,7 +18,7 @@
 ## Preventing blocked play
 
 - [x] **Multiple admins.** The Admin player should be able to grant other players Admin privileges in the admin panel.
-- [ ] **Player minimum.** You need at least three players to start a game, or to start a new scene if a player dropped out mid-game.
+- [x] **Player minimum.** You need at least three players to start a game, or to start a new scene if a player dropped out mid-game. (Dev Mode bypasses the minimum for local testing.)
 - [ ] **Player kicking.** Admins should be able to kick players out of the game so that it doesn't get stuck if a player vanishes. Admins can kick other admins.
 
 ## Session management

frontend/src/components/LobbyPhase.svelte

@@ -74,14 +74,14 @@
     
     <div class="lobby-action">
         {#if state.player.is_admin}
-            {#if state.players.length >= 1}
+            {#if state.players.length >= 3 || state.game.dev_mode}
             <button on:click={startGame}
                     disabled={starting}
                     class="btn btn-primary btn-large glow-effect">
                 {starting ? 'Starting...' : 'Start Character Creation'}
             </button>
             {:else}
-            <button class="btn btn-primary btn-large" disabled>Waiting for players...</button>
+            <button class="btn btn-primary btn-large" disabled>Waiting for players... ({state.players.length}/3 minimum)</button>
             {/if}
         {:else}
         <div class="waiting-indicator">

frontend/src/components/SceneSetupPhase.svelte

@@ -44,7 +44,8 @@
     $: allRolesAssigned = state.players.every(p => p.role !== null || p.needs_reroll);
     $: deepPlayer = state.players.find(p => p.role === 'deep');
     $: piratPlayer = state.players.find(p => p.role === 'pirat');
-    $: canStart = allRolesAssigned && deepPlayer && piratPlayer && (state.player.is_admin || state.player.role === 'deep');
+    $: enoughPlayers = state.players.length >= 3 || state.game.dev_mode;
+    $: canStart = enoughPlayers && allRolesAssigned && deepPlayer && piratPlayer && (state.player.is_admin || state.player.role === 'deep');
 </script>
 
 <div class="scene-setup-view text-center">
@@ -137,6 +138,8 @@
                 class="btn btn-primary btn-large glow-effect">
             {starting ? 'Starting Scene...' : 'Confirm Roles & Shuffle Deck'}
         </button>
+        {:else if !enoughPlayers}
+            <p class="text-danger italic mt-4">You need at least 3 players to start a scene — share the join link!</p>
         {:else if !allRolesAssigned}
             <p class="text-muted italic mt-4">Waiting for all players to choose a role...</p>
         {:else if !deepPlayer}

src/pirats/crud_base.py

@@ -234,6 +234,12 @@ def dev_mode_default() -> bool:
         return True
     return val.strip().lower() in ("1", "true", "yes", "on")
 
+MIN_PLAYERS = 3
+
+def has_min_players(game: Game) -> bool:
+    """The crew needs at least MIN_PLAYERS to start a game or a new scene; Dev Mode bypasses this for testing."""
+    return game.dev_mode or len(game.players) >= MIN_PLAYERS
+
 def create_game(db: Session, crew_name: Optional[str] = None) -> Game:
     deck = cards.get_fresh_deck()
     game = Game(

src/pirats/crud_scene.py

@@ -7,7 +7,7 @@ from . import cards
 from .crud_base import (
     get_player, get_game, get_player_hand, set_player_hand,
     get_game_deck, calculate_max_hand_size, add_game_event, reshuffle_discard_pile,
-    change_player_rank, set_captain, evaluate_card_play
+    change_player_rank, set_captain, evaluate_card_play, has_min_players, MIN_PLAYERS
 )
 
 # --- Scene Setup Operations ---
@@ -33,6 +33,9 @@ def confirm_scene_setup(db: Session, game_id: str) -> Tuple[bool, str]:
     if not game:
         return False, "Game not found."
 
+    if not has_min_players(game):
+        return False, f"You need at least {MIN_PLAYERS} players to start a scene."
+
     players = game.players
 
     # Default any unselected roles to 'pirat'. Pending recruits have no Pi-Rat

src/pirats/routes_lobby.py

@@ -1,4 +1,5 @@
 from fastapi import APIRouter, Depends, HTTPException
+from fastapi.responses import JSONResponse
 from sqlmodel import Session
 from .database import get_session
 from . import crud
@@ -10,6 +11,8 @@ def lobby_start_character_creation(game_id: str, db: Session = Depends(get_sessi
     game = crud.get_game(db, game_id)
     if not game:
         raise HTTPException(status_code=404, detail="Game not found")
+    if not crud.has_min_players(game):
+        return JSONResponse({"error": f"You need at least {crud.MIN_PLAYERS} players to start a game."}, status_code=400)
     game.phase = "character_creation"
     db.add(game)
     db.commit()

tests/test_game.py

@@ -1433,3 +1433,76 @@ def test_grant_and_revoke_admin():
         assert "admin_key" not in response.json()["game"]
     finally:
         app.dependency_overrides.clear()
+
+def test_player_minimum(session):
+    game = crud.create_game(session)
+    game.dev_mode = False
+    session.add(game)
+    session.commit()
+    crud.add_player(session, game.id, "P1", is_creator=True)
+    crud.add_player(session, game.id, "P2")
+    session.refresh(game)
+
+    # Two players can't start a scene
+    assert not crud.has_min_players(game)
+    ok, msg = crud.confirm_scene_setup(session, game.id)
+    assert not ok
+    assert "at least 3" in msg
+
+    # Dev Mode bypasses the minimum for testing
+    game.dev_mode = True
+    session.add(game)
+    session.commit()
+    assert crud.has_min_players(game)
+
+    # Three players is enough regardless
+    game.dev_mode = False
+    session.add(game)
+    session.commit()
+    crud.add_player(session, game.id, "P3")
+    session.refresh(game)
+    assert crud.has_min_players(game)
+
+def test_lobby_start_requires_min_players():
+    from fastapi.testclient import TestClient
+    from sqlalchemy.pool import StaticPool
+    from sqlmodel import SQLModel, create_engine, Session
+    from pirats.main import app
+    from pirats import crud
+
+    engine = create_engine(
+        "sqlite://",
+        connect_args={"check_same_thread": False},
+        poolclass=StaticPool,
+    )
+    SQLModel.metadata.create_all(engine)
+    session = Session(engine)
+
+    game = crud.create_game(session)
+    game.dev_mode = False
+    session.add(game)
+    session.commit()
+    crud.add_player(session, game.id, "P1", is_creator=True)
+    crud.add_player(session, game.id, "P2")
+
+    def get_session_override():
+        yield session
+
+    from pirats.database import get_session
+    app.dependency_overrides[get_session] = get_session_override
+    client = TestClient(app)
+
+    try:
+        response = client.post(f"/api/game/{game.id}/lobby/start")
+        assert response.status_code == 400
+        assert "at least 3" in response.json()["error"]
+        session.refresh(game)
+        assert game.phase == "lobby"
+
+        crud.add_player(session, game.id, "P3")
+        response = client.post(f"/api/game/{game.id}/lobby/start")
+        assert response.status_code == 200
+        session.refresh(game)
+        assert game.phase == "character_creation"
+    finally:
+        app.dependency_overrides.clear()