Treasury yields are at their lowest--and MBS at their highest--levels since early June.  For 10yr Treasuries specifically, it wouldn't take more than a few bps of improvement to be at the best levels in 3 months.  Moving out the curve to 30yr Treasuries and we're already there. 

Does this matter?  Not really.  It's just another commentary on the phenomenon of longer maturities performing differently than shorter maturities.  Nothing has changed about that outperformance today.  It's just interesting to note that 30yr yields are at 3 month lows while 2yr yields remain at the highest levels since 2011. 

Longer maturities are more sensitive to long term economic growth and inflation prospects.  Short term maturities are more concerned with monetary policy.  Today's news has arguably benefited both, but with some caveats.

As for the news in question, today is all about China's move to devalue its currency.  It can be looked at from several angles, but few are positive for the global economy.  Chiefly, it's seen as an act of desperation to buoy a struggling Chinese economy.  Some would refer to China as a "global growth engine," whatever that means.  So sure... maybe it's a bad sign that they seem to be pulling out all the stops to avoid a decline in growth. 

In a more practical sense, this is yet another feather in the cap of global currency wars and central bank accommodation.  It certainly could affect the Fed's willingness to hike rates because overly strong domestic currency has its downsides.  Fed funds futures reflected this stance with the likelihood of a December or September hike quickly moving back to its lowest levels in a week.