diff --git a/file_upload.go b/file_upload.go
index 4318df8..cd8cc95 100644
--- a/file_upload.go
+++ b/file_upload.go
@@ -8,6 +8,7 @@ import (
 	"crypto/sha256"
 	"encoding/base64"
 	"encoding/hex"
+	"fmt"
 	"io"
 	"mime"
 	"os"
@@ -24,6 +25,17 @@ func (protonDrive *ProtonDrive) handleRevisionConflict(ctx context.Context, link
 
 		draftRevision, err := protonDrive.GetRevisions(ctx, link, proton.RevisionStateDraft)
 		if err != nil {
+			// If we can't list revisions but the link is already in draft state
+			// (e.g. a broken/incomplete upload from a previous failed attempt)
+			// and the user wants to replace existing drafts, delete the link and
+			// let the caller retry from scratch rather than failing outright.
+			if protonDrive.Config.ReplaceExistingDraft && link.State == proton.LinkStateDraft {
+				err = protonDrive.c.DeleteChildren(ctx, protonDrive.MainShare.ShareID, link.ParentLinkID, linkID)
+				if err != nil {
+					return "", false, err
+				}
+				return "", true, nil
+			}
 			return "", false, err
 		}
 
@@ -250,6 +262,18 @@ func (protonDrive *ProtonDrive) uploadAndCollectBlockData(ctx context.Context, n
 		return nil, 0, nil, "", ErrMissingInputUploadAndCollectBlockData
 	}
 
+	// Fetch the per-revision verification code required by Proton's storage backend.
+	// Each block's Verifier.Token is produced by XOR-ing this code with the first
+	// bytes of that block's ciphertext (per the Proton Drive JS SDK spec).
+	revVerification, err := protonDrive.c.GetRevisionVerification(ctx, protonDrive.MainShare.VolumeID, linkID, revisionID)
+	if err != nil {
+		return nil, 0, nil, "", fmt.Errorf("uploadAndCollectBlockData: get revision verification: %w", err)
+	}
+	verificationCode, err := base64.StdEncoding.DecodeString(revVerification.VerificationCode)
+	if err != nil {
+		return nil, 0, nil, "", fmt.Errorf("uploadAndCollectBlockData: decode verification code: %w", err)
+	}
+
 	totalFileSize := int64(0)
 
 	pendingUploadBlocks := make([]PendingUploadBlocks, 0)
@@ -309,7 +333,7 @@ func (protonDrive *ProtonDrive) uploadAndCollectBlockData(ctx context.Context, n
 	blockSizes := make([]int64, 0)
 	for i := 1; shouldContinue; i++ {
 		if (i-1) > 0 && (i-1)%UPLOAD_BATCH_BLOCK_SIZE == 0 {
-			err := uploadPendingBlocks()
+			err = uploadPendingBlocks()
 			if err != nil {
 				return nil, 0, nil, "", err
 			}
@@ -365,17 +389,31 @@ func (protonDrive *ProtonDrive) uploadAndCollectBlockData(ctx context.Context, n
 		}
 		manifestSignatureData = append(manifestSignatureData, hash...)
 
+		// Compute per-block verifier token: XOR verificationCode with the
+		// leading bytes of the encrypted block (zero-padded if block is shorter).
+		verificationToken := make([]byte, len(verificationCode))
+		for j, v := range verificationCode {
+			var b byte
+			if j < len(encData) {
+				b = encData[j]
+			}
+			verificationToken[j] = v ^ b
+		}
+
 		pendingUploadBlocks = append(pendingUploadBlocks, PendingUploadBlocks{
 			blockUploadInfo: proton.BlockUploadInfo{
 				Index:        i, // iOS drive: BE starts with 1
 				Size:         int64(len(encData)),
 				EncSignature: encSignatureStr,
 				Hash:         base64Hash,
+				Verifier: proton.BlockUploadVerifier{
+					Token: base64.StdEncoding.EncodeToString(verificationToken),
+				},
 			},
 			encData: encData,
 		})
 	}
-	err := uploadPendingBlocks()
+	err = uploadPendingBlocks()
 	if err != nil {
 		return nil, 0, nil, "", err
 	}
diff --git a/go.mod b/go.mod
index 62ef8b4..2f60fce 100644
--- a/go.mod
+++ b/go.mod
@@ -7,7 +7,7 @@ toolchain go1.23.5
 require (
 	github.com/ProtonMail/gluon v0.17.1-0.20230724134000-308be39be96e
 	github.com/ProtonMail/gopenpgp/v2 v2.8.2
-	github.com/rclone/go-proton-api v1.0.1-0.20260127173028-eb465cac3b18
+	github.com/rclone/go-proton-api v1.0.1-0.20260218123427-1a63a293e3a2
 	github.com/relvacode/iso8601 v1.6.0
 	golang.org/x/sync v0.10.0
 )
diff --git a/go.sum b/go.sum
index 5b8df5d..125b082 100644
--- a/go.sum
+++ b/go.sum
@@ -77,6 +77,8 @@ github.com/pmezard/go-difflib v1.0.0 h1:4DBwDE0NGyQoBHbLQYPwSUPoCMWR5BEzIk/f1lZb
 github.com/pmezard/go-difflib v1.0.0/go.mod h1:iKH77koFhYxTK1pcRnkKkqfTogsbg7gZNVY4sRDYZ/4=
 github.com/rclone/go-proton-api v1.0.1-0.20260127173028-eb465cac3b18 h1:Lc+d3ISfQaMJKWZOE7z4ZSY4RVmdzbn1B0IM8xN18qM=
 github.com/rclone/go-proton-api v1.0.1-0.20260127173028-eb465cac3b18/go.mod h1:LB2kCEaZMzNn3ocdz+qYfxXmuLxxN0ka62KJd2x53Bc=
+github.com/rclone/go-proton-api v1.0.1-0.20260218123427-1a63a293e3a2 h1:QR87vlRq+z0JwJsUteEhsXcSrXGJ2yte5MocMSfajM4=
+github.com/rclone/go-proton-api v1.0.1-0.20260218123427-1a63a293e3a2/go.mod h1:LB2kCEaZMzNn3ocdz+qYfxXmuLxxN0ka62KJd2x53Bc=
 github.com/relvacode/iso8601 v1.6.0 h1:eFXUhMJN3Gz8Rcq82f9DTMW0svjtAVuIEULglM7QHTU=
 github.com/relvacode/iso8601 v1.6.0/go.mod h1:FlNp+jz+TXpyRqgmM7tnzHHzBnz776kmAH2h3sZCn0I=
 github.com/sirupsen/logrus v1.9.3 h1:dueUQJ1C2q9oE3F7wvmSGAaVtTmUizReu6fjN8uqzbQ=