XAU/EUR isn't an independently quoted price, it's derived from dividing the dollar gold price by the EUR/USD exchange rate. That means every XAU/EUR move is really two moves layered on top of each other, and separating them changes how you should interpret the chart.
1. Two engines, one chart
When gold rallies in dollar terms and EUR/USD is flat, XAU/EUR rises by roughly the same amount. When gold is flat but the euro weakens against the dollar, XAU/EUR still rises, purely from the currency conversion, without gold itself doing anything. Reading a XAU/EUR chart without checking XAU/USD alongside it means missing which engine is actually driving the move.
2. Where the ECB fits in
European Central Bank rate decisions move EUR/USD directly, and since XAU/EUR incorporates that exchange rate, an ECB surprise can move XAU/EUR meaningfully even on a day when dollar gold barely reacts to anything. Traders watching only Fed policy while trading XAU/EUR are missing half of what actually determines the pair's move.
3. A practical check
Before reacting to a XAU/EUR move, glance at XAU/USD over the same period. If both moved together, it's a genuine gold story. If XAU/EUR moved and XAU/USD didn't, the real story is in EUR/USD, and that's the chart worth analyzing instead.