Why does the short run aggregate supply curve shift to the left in the long run following an increase in aggregate demand?

The aggregate supply curve shifts to the left as the price of key inputs rises, making a combination of lower output, higher unemployment, and higher inflation possible. When an economy experiences stagnant growth and high inflation at the same time it is referred to as stagflation.

Why does the short−run aggregate supply curve shift to the left in the long​ run, following an increase in aggregate​ demand? Workers and firms adjust their expectations of wages and prices upward and they push for higher wages and prices.

What causes shifts in SRAS? When the price level changes and firms produce more in response to that, we move along the SRAS curve. But, any change that makes production different at every possible price level will shift the SRAS curve. Events like these are called “shocks” because they aren't anticipated.

Short-run aggregate supply curves illustrate supply in the near future or over a period in which capital is fixed. Long-run aggregate supply curves show supply in the long-term in which all inputs are variable. Aggregate supply is a function of total production within an economy and the price level.