It's not possible to have pipeline output close prices to match what you would fetch from Yahoo. The issue lies at the heart of what pipeline is designed to do (and not do). Pipeline is designed to surface data to match what an individual would have seen on each pipeline date. The intent is to never allow any lookahead bias in the data. This is true of pricing data by never including future price adjustments, and true of fundamental data by never making it available until when it was actually released to the public.
Yahoo prices are adjusted for splits and, oddly, not dividends as of the actual current day. Only the 'Adj Close' field is adjusted for both. If pipeline were to output prices to match Yahoo then it would need to account for potential 'future' splits and dividends. This lookahead bias is not allowed.
If one wanted to get prices similar to the Yahoo 'Adj Close' prices, use the get_pricing method in a notebook. Simply set the 'end' date to the current 'today' date. Something like this to get close prices for SPY from 1-1-2008.
today = datetime.now()
spy_prices = get_pricing('SPY', start_date='1-1-2008', end_date=today, fields='close_price')
There still may be a discrepancy in prices however. Quantopian uses the last traded price as the close price for a security. Yahoo uses end-of-day (EOD) prices which include the final auction orders. These auction orders are not technically 'market' orders and are not included in Quantopian's prices. There is a little more info about this in the FAQ and in this post
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