After modest overnight gains, bonds had been pulling back in the early part of the domestic session.  Treasuries and MBS were both nearly back to unchanged levels when equities markets took control of the momentum.

The "stock lever" isn't always a factor for bonds, but it has been increasingly prevalent of late, and tends to be more prevalent in general amid uncertainty.  And there is certainly uncertainty.

Stock futures trade almost all night, but the 9:30am open of cash trading brings additional liquidity and participation from a wider variety of traders.  It's not uncommon to see a more pronounced move in stocks around this time (including shortly before or after).  Such was the case today as stocks began selling off after the NYSE open.

This particular bout of stock market weakness goes a long way toward confirming a potential bigger picture shift.  After beginning the record-setting bull run in mid 2009, the only other downturn that's been remotely similar was in 2011.  Days like today make the current downturn look definitively worse.  Bonds are loving every minute of it.  On the following chart, 10yr yields are in yellow, German Bunds are in red, and S&P futures are in blue (not that it really matters since all the lines are right on top of each other).  The second chart is a longer term look at the S&P.