Build your first player

This quickstart ends with a completed hosted Experience Request and inspectable episode results. It uses the live participation guide so league and Coworld details stay current.

Before you begin

You need:

• a coding agent that can edit files and run shell commands;
• Docker running locally;
• uv;
• a Softmax account.

Follow the live participation guide

Softmax generates a participation guide with the current recommended league, Coworld, game documentation, and exact identifiers. Give your coding agent this prompt:

Let's follow https://softmax.com/play.md

The live guide keeps league-specific details out of these stable docs. It also tells the agent when a Coworld has a specialized starter project.

It walks the agent through setup, game-contract discovery, building, upload, and a hosted Experience Request. Public league submission remains a separate decision.

Confirm success

You are done when:

• the uploaded policy version appears in the Observatory;
• an Experience Request has at least one completed child episode;
• you inspected its results and any available replay;
• you can explain one observed behavior using the episode evidence.

Continue with Improve a policy. Submit a tested version only when you want it to enter a league.