Write the manifest

coworld_manifest.json is the package map. It tells Coworld tooling what to run, what the game accepts, which variants exist, and which episode proves the package works. Start from the Paint Arena template. Keep the generated manifest schema open while you edit.

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Declare the live roles first

Every manifest requires one game and at least one bundled player.

• game describes the game, its runnable, schemas, protocols, documentation, and optional replay viewer.
• player contains the bundled clients used for examples, local play, and certification.
• reporter, grader, diagnoser, and optimizer are optional supporting roles.

For new Softmax Coworlds, omit commissioner runnables. Softmax leagues use the platform ladder instead of starting a commissioner container. Only declare supporting roles that have a concrete use and working implementation. Their exact behavior belongs in the role contracts.

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Describe the runtime config

game.config_schema validates the config the game reads at startup. It must require a tokens array of strings. Set minItems and maxItems on that array to the game’s supported seat bounds. Tokens authenticate player slots; they do not choose the scheduled roster size. Do not place token values in author-owned configs:

• variants[].game_config omits tokens.
• certification.game_config omits tokens.

The runner adds fresh tokens after it knows the episode roster. If the game displays player names, declare a players array whose items require a string name. Hosted dispatch can then replace placeholder names with the resolved player names. Keep game-specific seat mechanics in game-specific fields. For example, role, team, color, or spawn data can live in a slots structure owned by your game.

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Describe successful results

game.results_schema validates the JSON object written when an episode completes successfully. It must include a numeric scores array with one value per player slot. Add fields that help people explain those scores. Painted tiles, objectives completed, or team outcomes may be useful, depending on the game. The schema should reject incomplete results. Diagnostic logs are not a substitute for structured episode truth.

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Link the protocols and game docs

The manifest stores inline text or public HTTP(S) references. A referenced document must remain available after upload. Provide:

• game.protocols.player for the exact observation and action exchange;
• game.protocols.global for the spectator stream; and
• game.docs.readme for rules, setup, strategy, and game-specific guidance.

Use game.docs.pages for optional longer material. Keep Softmax login, policy upload, league submission, and replay retrieval in the platform guides instead of repeating them in each game repository.

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Create useful variants

A variant is a named, token-free game configuration. Declare at least one. Use variants for supported ways to run the same game image, such as:

• different seat counts within the schema bounds;
• shorter or longer episodes;
• alternate maps or rule toggles; or
• fixed scenarios used for comparisons.

The default competitive variant should usually omit a fixed seed. This gives episodes fresh initial states. Add seeded variants when reproducibility is the purpose. Do not use variants to bypass the config schema. Each variant must remain a valid config after the runner injects its tokens.

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Make certification small and complete

The certification fixture is the token-free config and bundled-player roster used by coworld certify and default local episode runs. It should:

• finish quickly enough to run during every authoring loop;
• exercise the real player protocol and game completion path;
• include every declared bundled player at least once;
• produce valid results and replay data; and
• remain deterministic enough to debug.

Certification is a package smoke test, not a gameplay benchmark. A weak baseline score can still certify if the episode and contracts are healthy.

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Keep the template buildable

Author coworld_manifest_template.json with image placeholders. A Compose service named my-game maps to the placeholder {{MY_GAME_IMAGE}}. Do not set game.version in the template. coworld build --version stamps the release version into the hydrated manifest. It is common for one image to implement several runnables with different commands. Pin Compose services to linux/amd64, which matches the hosted runners. When you add source_url, point it at the public source for that runnable. Prefer a commit SHA over a branch. Source metadata helps people inspect provenance, but the runtime executes the recorded image and command.

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Treat manifest environment as public

Uploaded manifests and bundled images are visible to users. Do not put raw credentials in runnable env. For game-container secrets needed during hosted episodes, upload the value with coworld secret put and use a secret://coworld/... reference. Local runs must override that reference with a local value they can read. See the manifest secret contract before adding a secret reference.

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Review before building

• game and at least one bundled player are declared.
• tokens is required and has correct seat bounds.
• Author-owned configs omit token values.
• Results require one numeric score per slot.
• Player and global protocols point to durable public documents.
• The game README explains rules and strategy.
• At least one valid variant exists.
• Certification seats every declared bundled player.
• Images build for linux/amd64.
• Public environment values contain no secrets.

Next, build, certify, and upload the package.