diff --git a/modules/adagioBidAdapter.js b/modules/adagioBidAdapter.js
index fe086afbf43..57dd80aa9b1 100644
--- a/modules/adagioBidAdapter.js
+++ b/modules/adagioBidAdapter.js
@@ -860,8 +860,7 @@ function storeRequestInAdagioNS(bidRequest) {
       bidder: bidRequest.bidder,
       params: bidRequest.params // use the updated bid.params object with auto-detected params
     }],
-    // TODO: fix auctionId leak: https://github.com/prebid/Prebid.js/issues/9781
-    auctionId: bidRequest.auctionId,
+    auctionId: bidRequest.auctionId, // this auctionId has been generated by adagioBidAdapter
     pageviewId: internal.getPageviewId(),
     printNumber,
     localPbjs: '$$PREBID_GLOBAL$$',
@@ -870,7 +869,7 @@ function storeRequestInAdagioNS(bidRequest) {
 
   // (legacy) Store internal adUnit information
   w.ADAGIO.adUnits[bidRequest.adUnitCode] = {
-    auctionId: bidRequest.auctionId,
+    auctionId: bidRequest.auctionId, // this auctionId has been generated by adagioBidAdapter
     pageviewId: internal.getPageviewId(),
     printNumber,
   };
@@ -982,7 +981,14 @@ export const spec = {
     const syncEnabled = deepAccess(config.getConfig('userSync'), 'syncEnabled')
     const usIfr = syncEnabled && userSync.canBidderRegisterSync('iframe', 'adagio')
 
-    const adUnits = _map(validBidRequests, (bidRequest) => {
+    const aucId = generateUUID()
+
+    const adUnits = _map(validBidRequests, (rawBidRequest) => {
+      const bidRequest = {...rawBidRequest}
+
+      // Fix https://github.com/prebid/Prebid.js/issues/9781
+      bidRequest.auctionId = aucId
+
       const globalFeatures = GlobalExchange.getOrSetGlobalFeatures();
       const features = {
         ...globalFeatures,
@@ -1095,6 +1101,12 @@ export const spec = {
 
       storeRequestInAdagioNS(bidRequest);
 
+      // Remove these fields at the very end, so we can still use them before.
+      delete bidRequest.transactionId;
+      delete bidRequest.ortb2Imp;
+      delete bidRequest.ortb2;
+      delete bidRequest.sizes;
+
       return bidRequest;
     });
 
@@ -1233,33 +1245,8 @@ export const spec = {
    * @returns {object} updated params
    */
   transformBidParams(params, isOrtb, adUnit, bidRequests) {
-    const adagioBidderRequest = find(bidRequests, bidRequest => bidRequest.bidderCode === 'adagio');
-    const adagioBid = find(adagioBidderRequest.bids, bid => bid.adUnitCode === adUnit.code);
-
-    if (isOrtb) {
-      autoFillParams(adagioBid);
-
-      adagioBid.params.auctionId = deepAccess(adagioBidderRequest, 'auctionId');
-
-      const globalFeatures = GlobalExchange.getOrSetGlobalFeatures();
-      adagioBid.params.features = {
-        ...globalFeatures,
-        print_number: getPrintNumber(adagioBid.adUnitCode, adagioBidderRequest).toString(),
-        adunit_position: getSlotPosition(adagioBid.params.adUnitElementId) // adUnitElementId à déplacer ???
-      };
-
-      adagioBid.params.pageviewId = internal.getPageviewId();
-      adagioBid.params.prebidVersion = '$prebid.version$';
-      adagioBid.params.data = GlobalExchange.getExchangeData();
-
-      if (deepAccess(adagioBid, 'mediaTypes.video.context') === OUTSTREAM) {
-        adagioBid.params.playerName = setPlayerName(adagioBid);
-      }
-
-      storeRequestInAdagioNS(adagioBid);
-    }
-
-    return adagioBid.params;
+    // We do not have a prebid server adapter. So let's return unchanged params.
+    return params;
   }
 };
 
diff --git a/test/spec/modules/adagioBidAdapter_spec.js b/test/spec/modules/adagioBidAdapter_spec.js
index 7476482721b..2fb40070184 100644
--- a/test/spec/modules/adagioBidAdapter_spec.js
+++ b/test/spec/modules/adagioBidAdapter_spec.js
@@ -296,6 +296,7 @@ describe('Adagio bid adapter', () => {
       sandbox.stub(adagio, 'getDevice').returns({ a: 'a' });
       sandbox.stub(adagio, 'getSite').returns({ domain: 'adagio.io', 'page': 'https://adagio.io/hb' });
       sandbox.stub(adagio, 'getPageviewId').returns('1234-567');
+      sandbox.stub(utils, 'generateUUID').returns('blabla');
 
       const bid01 = new BidRequestBuilder().withParams().build();
       const bidderRequest = new BidderRequestBuilder().build();
@@ -309,6 +310,18 @@ describe('Adagio bid adapter', () => {
       expect(requests[0].data).to.have.all.keys(expectedDataKeys);
     });
 
+    it('should use a custom generated auctionId and remove transactionId', function() {
+      const expectedAuctionId = '373bcda7-9794-4f1c-be2c-0d223d11d579'
+      sandbox.stub(utils, 'generateUUID').returns(expectedAuctionId);
+
+      const bid01 = new BidRequestBuilder().withParams().build();
+      const bidderRequest = new BidderRequestBuilder().build();
+
+      const requests = spec.buildRequests([bid01], bidderRequest);
+      expect(requests[0].data.adUnits[0].auctionId).eq(expectedAuctionId);
+      expect(requests[0].data.adUnits[0].transactionId).to.not.exist;
+    });
+
     it('should enqueue computed features for collect usage', function() {
       sandbox.stub(Date, 'now').returns(12345);
 
@@ -1280,14 +1293,6 @@ describe('Adagio bid adapter', () => {
 
   describe('transformBidParams', function() {
     it('Compute additional params in s2s mode', function() {
-      GlobalExchange.prepareExchangeData('{}');
-
-      sandbox.stub(window.top.document, 'getElementById').returns(
-        fixtures.getElementById()
-      );
-      sandbox.stub(window.top, 'getComputedStyle').returns({ display: 'block' });
-      sandbox.stub(utils, 'inIframe').returns(false);
-
       const adUnit = {
         code: 'adunit-code',
         params: {
@@ -1308,22 +1313,8 @@ describe('Adagio bid adapter', () => {
         }
       }).withParams().build();
 
-      const params = spec.transformBidParams({ organizationId: '1000' }, true, adUnit, [{ bidderCode: 'adagio', auctionId: bid01.auctionId, bids: [bid01] }]);
-
-      expect(params.organizationId).to.exist;
-      expect(params.auctionId).to.exist;
-      expect(params.playerName).to.exist;
-      expect(params.playerName).to.equal('other');
-      expect(params.features).to.exist;
-      expect(params.features.page_dimensions).to.exist;
-      expect(params.features.adunit_position).to.exist;
-      expect(params.features.dom_loading).to.exist;
-      expect(params.features.print_number).to.exist;
-      expect(params.features.user_timestamp).to.exist;
-      expect(params.placement).to.exist;
-      expect(params.adUnitElementId).to.exist;
-      expect(params.site).to.exist;
-      expect(params.data.session).to.exist;
+      const params = spec.transformBidParams({ param01: 'test' }, true, adUnit, [{ bidderCode: 'adagio', auctionId: bid01.auctionId, bids: [bid01] }]);
+      expect(params.param01).eq('test');
     });
   });