We propose a channel whereby uncertainty about the central bank's reaction function raises risk premia, especially when inflation deviates from target. To test the channel, we focus on the period after the Federal Reserve's revision of its policy framework in 2020. Post-framework communication introduced reaction function uncertainty just as inflation surged to a four-decade high. Market concerns about policy mistakes amid incoming data drove up term premia, undermining the easy financial conditions the Fed initially sought. While short-rate expectations were anchored by forward guidance, term premium sensitivity to inflation news increased. The subsequent shift in the Fed's words and then actions, reaffirming its anti-inflation stance, stabilized premia and neutralized the effect of macroeconomic news on long-term yields.