diff --git a/@xen-orchestra/backups/RemoteAdapter.mjs b/@xen-orchestra/backups/RemoteAdapter.mjs
index 993cc8038..8ab8bc1e8 100644
--- a/@xen-orchestra/backups/RemoteAdapter.mjs
+++ b/@xen-orchestra/backups/RemoteAdapter.mjs
@@ -191,13 +191,14 @@ export class RemoteAdapter {
   // check if we will be allowed to merge a a vhd created in this adapter
   // with the vhd at path `path`
   async isMergeableParent(packedParentUid, path) {
-    return await Disposable.use(openVhd(this.handler, path), vhd => {
+    return await Disposable.use(VhdSynthetic.fromVhdChain(this.handler, path), vhd => {
       // this baseUuid is not linked with this vhd
       if (!vhd.footer.uuid.equals(packedParentUid)) {
         return false
       }
 
-      const isVhdDirectory = vhd instanceof VhdDirectory
+      // check if all the chain is composed of vhd directory
+      const isVhdDirectory = vhd.checkVhdsClass(VhdDirectory)
       return isVhdDirectory
         ? this.useVhdDirectory() && this.#getCompressionType() === vhd.compressionType
         : !this.useVhdDirectory()
diff --git a/@xen-orchestra/backups/_runners/_vmRunners/IncrementalXapi.mjs b/@xen-orchestra/backups/_runners/_vmRunners/IncrementalXapi.mjs
index 994ab767c..b1ecf21b0 100644
--- a/@xen-orchestra/backups/_runners/_vmRunners/IncrementalXapi.mjs
+++ b/@xen-orchestra/backups/_runners/_vmRunners/IncrementalXapi.mjs
@@ -133,7 +133,7 @@ export const IncrementalXapi = class IncrementalXapiVmBackupRunner extends Abstr
       ])
       const srcVdi = srcVdis[snapshotOf]
       if (srcVdi !== undefined) {
-        baseUuidToSrcVdi.set(baseUuid, srcVdi)
+        baseUuidToSrcVdi.set(baseUuid, srcVdi.uuid)
       } else {
         debug('ignore snapshot VDI because no longer present on VM', {
           vdi: baseUuid,
@@ -154,18 +154,18 @@ export const IncrementalXapi = class IncrementalXapiVmBackupRunner extends Abstr
     }
 
     const fullVdisRequired = new Set()
-    baseUuidToSrcVdi.forEach((srcVdi, baseUuid) => {
+    baseUuidToSrcVdi.forEach((srcVdiUuid, baseUuid) => {
       if (presentBaseVdis.has(baseUuid)) {
         debug('found base VDI', {
           base: baseUuid,
-          vdi: srcVdi.uuid,
+          vdi: srcVdiUuid,
         })
       } else {
         debug('missing base VDI', {
           base: baseUuid,
-          vdi: srcVdi.uuid,
+          vdi: srcVdiUuid,
         })
-        fullVdisRequired.add(srcVdi.uuid)
+        fullVdisRequired.add(srcVdiUuid)
       }
     })
 
diff --git a/@xen-orchestra/backups/_runners/_writers/IncrementalRemoteWriter.mjs b/@xen-orchestra/backups/_runners/_writers/IncrementalRemoteWriter.mjs
index cb1885a86..0beb5f8f0 100644
--- a/@xen-orchestra/backups/_runners/_writers/IncrementalRemoteWriter.mjs
+++ b/@xen-orchestra/backups/_runners/_writers/IncrementalRemoteWriter.mjs
@@ -1,9 +1,8 @@
 import assert from 'node:assert'
 import mapValues from 'lodash/mapValues.js'
-import ignoreErrors from 'promise-toolbox/ignoreErrors'
 import { asyncEach } from '@vates/async-each'
 import { asyncMap } from '@xen-orchestra/async-map'
-import { chainVhd, checkVhdChain, openVhd, VhdAbstract } from 'vhd-lib'
+import { chainVhd, openVhd } from 'vhd-lib'
 import { createLogger } from '@xen-orchestra/log'
 import { decorateClass } from '@vates/decorate-with'
 import { defer } from 'golike-defer'
@@ -23,42 +22,45 @@ import { Disposable } from 'promise-toolbox'
 const { warn } = createLogger('xo:backups:DeltaBackupWriter')
 
 export class IncrementalRemoteWriter extends MixinRemoteWriter(AbstractIncrementalWriter) {
+  #parentVdiPaths
+  #vhds
   async checkBaseVdis(baseUuidToSrcVdi) {
+    this.#parentVdiPaths = {}
     const { handler } = this._adapter
     const adapter = this._adapter
 
     const vdisDir = `${this._vmBackupDir}/vdis/${this._job.id}`
 
-    await asyncMap(baseUuidToSrcVdi, async ([baseUuid, srcVdi]) => {
-      let found = false
+    await asyncMap(baseUuidToSrcVdi, async ([baseUuid, srcVdiUuid]) => {
+      let parentDestPath
+      const vhdDir = `${vdisDir}/${srcVdiUuid}`
       try {
-        const vhds = await handler.list(`${vdisDir}/${srcVdi.uuid}`, {
+        const vhds = await handler.list(vhdDir, {
           filter: _ => _[0] !== '.' && _.endsWith('.vhd'),
           ignoreMissing: true,
           prependDir: true,
         })
         const packedBaseUuid = packUuid(baseUuid)
-        await asyncMap(vhds, async path => {
-          try {
-            await checkVhdChain(handler, path)
-            // Warning, this should not be written as found = found || await adapter.isMergeableParent(packedBaseUuid, path)
-            //
-            // since all the checks of a path are done in parallel, found would be containing
-            // only the last answer of isMergeableParent which is probably not the right one
-            // this led to the support tickets  https://help.vates.fr/#ticket/zoom/4751 , 4729, 4665 and 4300
+        // the last one is probably the right one
 
-            const isMergeable = await adapter.isMergeableParent(packedBaseUuid, path)
-            found = found || isMergeable
+        for (let i = vhds.length - 1; i >= 0 && parentDestPath === undefined; i--) {
+          const path = vhds[i]
+          try {
+            if (await adapter.isMergeableParent(packedBaseUuid, path)) {
+              parentDestPath = path
+            }
           } catch (error) {
             warn('checkBaseVdis', { error })
-            await ignoreErrors.call(VhdAbstract.unlink(handler, path))
           }
-        })
+        }
       } catch (error) {
         warn('checkBaseVdis', { error })
       }
-      if (!found) {
+      // no usable parent => the runner will have to decide to fall back to a full or stop backup
+      if (parentDestPath === undefined) {
         baseUuidToSrcVdi.delete(baseUuid)
+      } else {
+        this.#parentVdiPaths[vhdDir] = parentDestPath
       }
     })
   }
diff --git a/@xen-orchestra/backups/_runners/_writers/IncrementalXapiWriter.mjs b/@xen-orchestra/backups/_runners/_writers/IncrementalXapiWriter.mjs
index bdcfc6cd2..4b4421f88 100644
--- a/@xen-orchestra/backups/_runners/_writers/IncrementalXapiWriter.mjs
+++ b/@xen-orchestra/backups/_runners/_writers/IncrementalXapiWriter.mjs
@@ -1,3 +1,4 @@
+import assert from 'node:assert'
 import { asyncMap, asyncMapSettled } from '@xen-orchestra/async-map'
 import ignoreErrors from 'promise-toolbox/ignoreErrors'
 import { formatDateTime } from '@xen-orchestra/xapi'
@@ -14,6 +15,7 @@ import find from 'lodash/find.js'
 
 export class IncrementalXapiWriter extends MixinXapiWriter(AbstractIncrementalWriter) {
   async checkBaseVdis(baseUuidToSrcVdi, baseVm) {
+    assert.notStrictEqual(baseVm, undefined)
     const sr = this._sr
     const replicatedVm = listReplicatedVms(sr.$xapi, this._job.id, sr.uuid, this._vmUuid).find(
       vm => vm.other_config[TAG_COPY_SRC] === baseVm.uuid