The Open Robo source code is ultimately the best documentation for its investing algorithm. Major design decisions are documented below.

• To reduce user overhead and avoid incurring capital gains, rebalancing is performed only through deposits and withdrawals. For best operation, you should aim to regularly deposit money into your portfolio. Monthly or quarterly deposit goals are useful planning tools.
• When choosing which ETF to buy for a given category, Open Robo selects the first ETF for that category that does not have a current loss greater than the minimum tax loss harvesting threshold. ETFs with potential losses are avoided even if the loss cannot yet be realized without triggering a wash sale.
• When choosing which ETFs to sell for a given category, long term holdings are preferred to short term holdings.
• If you have questions about the investment algorithm that you feel should be documented here, please submit a GitHub issue or (even better!) a pull request.