Tradier is the broker most index builders forget. Flat-fee monthly pricing on the Pro plan flips the cost maths against per-trade brokers the moment a custom index starts rebalancing meaningfully. That makes it an unusually good fit for a thematic basket that updates with the screen.
The flow
- Connect Tradier with a sandbox access token first. Encrypted at rest.
- Describe the index. Example: "Dividend Growers ex-tobacco ex-banks, 40 names, dividend-yield weighted, capped at 4%."
- Agent picks the universe, runs the screen, runs the backtest.
- Sandbox the basket. Watch a quarterly rebalance cycle before going live.
- Switch to live token. The same basket executes against the real account.
Why Tradier specifically
- Flat-fee Pro pricing absorbs the rebalance cost of a real custom index.
- API access on every plan, no developer tier upsell.
- Sandbox is genuine, not a toy. The same calls work against the real account.
- Options exposure available if a thesis needs hedging (no integration in Arithmos yet, but the connection survives).
Dividend Growers ex-tobacco ex-banks, 40 names, dividend-yield weighted, capped at 4% per name, rebalanced quarterly.
Fees
Arithmos charges the subscription. Tradier charges its flat-fee or per-trade plan, whichever you picked. No markup from us.
FAQ
Does Tradier's flat-fee plan actually save money on a custom index?
It depends on the rebalance frequency. A 60-stock index rebalanced quarterly fires roughly 240 trades a year. On a per-trade broker that adds up; on Tradier's flat-fee Pro plan it does not. The break-even sits at about 30 to 40 trades a month for most users.
How does the Tradier connection work?
Connect by pasting your Tradier access token. Stored AES-256-GCM encrypted, sandbox and live separated, revocable from your profile at any time.
Can I run sandbox first?
Yes. Sandbox and live are separated at the credential level. The default is sandbox. Live execution requires explicit acknowledgement on each index.
