chore: import upstream snapshot with attribution

examples/train/grpo/plugin/openenv/start_sudoku_server.py

@@ -0,0 +1,47 @@
+#!/usr/bin/env python3
+"""Start the TextArena Sudoku server with configurable concurrent sessions.
+
+The default OpenEnv server only allows 1 concurrent session because
+TextArenaEnvironment is not marked as SUPPORTS_CONCURRENT_SESSIONS.
+Since each WebSocket session creates an independent game instance,
+it is safe to enable concurrent sessions.
+
+Usage:
+    TEXTARENA_ENV_ID=Sudoku-v0 python start_sudoku_server.py
+    TEXTARENA_ENV_ID=Sudoku-v0 MAX_CONCURRENT_ENVS=8 python start_sudoku_server.py
+"""
+import os
+import uvicorn
+from openenv.core.env_server.http_server import create_app
+from textarena_env.server.app import (TextArenaAction, TextArenaObservation, build_textarena_gradio_app,
+                                      create_textarena_environment)
+from textarena_env.server.environment import TextArenaEnvironment
+
+# Read config from environment
+# Note: TEXTARENA_ENV_ID is read by create_textarena_environment factory,
+# not by this script directly.
+max_concurrent_envs = int(os.getenv('MAX_CONCURRENT_ENVS', '8'))
+host = os.getenv('HOST', '0.0.0.0')
+port = int(os.getenv('PORT', '8000'))
+
+# Mark TextArenaEnvironment as supporting concurrent sessions.
+# Each WebSocket session creates an independent game instance via the factory,
+# so concurrent sessions are safe.
+
+TextArenaEnvironment.SUPPORTS_CONCURRENT_SESSIONS = True
+
+# Build the app with custom max_concurrent_envs
+
+app = create_app(
+    create_textarena_environment,
+    TextArenaAction,
+    TextArenaObservation,
+    env_name='textarena_env',
+    max_concurrent_envs=max_concurrent_envs,
+    gradio_builder=build_textarena_gradio_app,
+)
+
+if __name__ == '__main__':
+    env_id = os.getenv('TEXTARENA_ENV_ID', 'Sudoku-v0')
+    print(f'Starting server: env={env_id}, max_concurrent_envs={max_concurrent_envs}')
+    uvicorn.run(app, host=host, port=port)