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arena-prediction-cli 0.6.0 The arena command is paper trading from a terminal. Node.js 20 or newer. One login covers the CLI, the MCP server and the website.
arena login opens a browser. Google is the default. arena login --provider apple uses Apple. There is no guest sign-in. npx arena-prediction-cli@0.6.0 login runs the same binary without adding arena to PATH. An agent should use the global install, because prompts and hooks call arena.

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A machine with no browser

Sign in on a machine that has a browser, into a file:
Copy the file, keep it readable only by you (chmod 600), and set ARENA_CREDENTIALS_FILE to that path. One host per file: a refresh replaces the stored token, so two hosts sharing it sign each other out.

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Signed out

These work before arena login: Store ins_ ids. Tickers change per game.

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API keys

arena keys ships in 0.6.0. It uses your login, not a key. See API keys.

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Route

--venue chooses where a paper ticket is priced. Pass an instrument id, not a venue ticker. The CLI prints each leg: size, price, and venue. On the HTTP order result the same split is fills (see Conventions). fillVenue is the first leg.

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Live orders

Live submission is off until Arena turns it on. You can save credentials in Settings before that. A saved key does not send an order. Arena’s switches ARENA_KALSHI_LIVE_TRADE and ARENA_POLY_INTL_LIVE_TRADE stay off by default. --live is Kalshi. --poly-intl is Polymarket International. Passing both is refused. Neither flag is on unless you set it. Arena lists Polymarket International. It does not list Polymarket US. A visitor in the US, or in PR, GU, VI, AS, MP, or UM, cannot trade Polymarket International. Arena reads CF-IPCountry and refuses the order with us_not_eligible. Settings hides the form when this account is ineligible. Polymarket International credentials are your API key, secret, passphrase, signer address, and signer private key. Arena stores them envelope-encrypted. The secret, passphrase, and signer private key are not shown again. The website calls GET, PUT, and DELETE /api/account/poly-intl-trading with your session. That path is not under /api/v1. Signed out, it answers 401 unauthorized. Kalshi uses the same pattern at /api/account/kalshi-trading: a key id and a private key, stored envelope-encrypted.
Paper orders stay the default. execution on POST /portfolio/orders is paper unless you send kalshi or poly-intl.

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Where to read the rest

Every command and flag: arena-predictions.com/docs/cli. Agents: arena-predictions.com/agents and the agents page here.