diff --git a/internal/application/repository/knowledge.go b/internal/application/repository/knowledge.go
index 831d4d063..095dcaada 100644
--- a/internal/application/repository/knowledge.go
+++ b/internal/application/repository/knowledge.go
@@ -248,7 +248,7 @@ func (r *knowledgeRepository) CheckKnowledgeExists(
 			var knowledge types.Knowledge
 			duplicateQuery := query.Where("type = ? AND file_hash = ?", "file", params.FileHash)
 			if params.FileType != "" {
-				duplicateQuery = duplicateQuery.Where("file_type = ?", params.FileType)
+				duplicateQuery = duplicateQuery.Where("LOWER(file_type) = ?", strings.ToLower(params.FileType))
 			}
 			err := duplicateQuery.First(&knowledge).Error
 			if err != nil {
@@ -260,13 +260,17 @@ func (r *knowledgeRepository) CheckKnowledgeExists(
 			return true, &knowledge, nil
 		}
 
-		// If no hash or hash doesn't match, use filename and size
+		// If no hash or hash doesn't match, use filename, size, and file type.
 		if params.FileName != "" && params.FileSize > 0 {
 			var knowledge types.Knowledge
-			err := query.Where(
-				"file_name = ? AND file_size = ?",
-				params.FileName, params.FileSize,
-			).First(&knowledge).Error
+			duplicateQuery := query.Where(
+				"type = ? AND file_name = ? AND file_size = ?",
+				"file", params.FileName, params.FileSize,
+			)
+			if params.FileType != "" {
+				duplicateQuery = duplicateQuery.Where("LOWER(file_type) = ?", strings.ToLower(params.FileType))
+			}
+			err := duplicateQuery.First(&knowledge).Error
 			if err != nil {
 				if errors.Is(err, gorm.ErrRecordNotFound) {
 					return false, nil, nil
diff --git a/internal/application/repository/knowledge_duplicate_test.go b/internal/application/repository/knowledge_duplicate_test.go
index 55ae0a230..f7279d046 100644
--- a/internal/application/repository/knowledge_duplicate_test.go
+++ b/internal/application/repository/knowledge_duplicate_test.go
@@ -47,4 +47,17 @@ func TestCheckKnowledgeExists_FileHashIsScopedByFileType(t *testing.T) {
 		require.NotNil(t, knowledge)
 		assert.Equal(t, "md", knowledge.FileType)
 	})
+
+	t.Run("file type matching is case-insensitive", func(t *testing.T) {
+		exists, knowledge, err := repo.CheckKnowledgeExists(ctx, tenantID, kbID, &types.KnowledgeCheckParams{
+			Type:     "file",
+			FileHash: fileHash,
+			FileType: "MD",
+		})
+
+		require.NoError(t, err)
+		assert.True(t, exists)
+		require.NotNil(t, knowledge)
+		assert.Equal(t, "md", knowledge.FileType)
+	})
 }
diff --git a/internal/application/service/datasource_service.go b/internal/application/service/datasource_service.go
index 79522e64b..931723d03 100644
--- a/internal/application/service/datasource_service.go
+++ b/internal/application/service/datasource_service.go
@@ -1253,8 +1253,8 @@ func (s *DataSourceService) ingestItem(ctx context.Context, ds *types.DataSource
 
 // dupIsSameNode reports whether a duplicate-content error means the parent still
 // exists in the KB *under this item's own external_id* — i.e. a content-dedup hit
-// against this same node, so reconciling its subtree is safe. Deduplication keys
-// on file_hash alone (CheckKnowledgeExists), so an updated node whose rebuilt body
+// against this same node, so reconciling its subtree is safe. File deduplication
+// keys on file_hash plus file_type (CheckKnowledgeExists), so an updated node whose rebuilt body
 // happens to hash-collide with a DIFFERENT knowledge item (another node, or a
 // manually-uploaded file with no external_id) would otherwise sweep this node's
 // children even though its own parent row was just deleted for the update and
diff --git a/internal/application/service/datasource_sweep_wiring_test.go b/internal/application/service/datasource_sweep_wiring_test.go
index ffce2ed51..02dea3dbb 100644
--- a/internal/application/service/datasource_sweep_wiring_test.go
+++ b/internal/application/service/datasource_sweep_wiring_test.go
@@ -160,7 +160,7 @@ func TestIngestItem_ReplacesSubtreeSweepsOnDuplicateParent(t *testing.T) {
 
 // TestIngestItem_NoSweepWhenDuplicateIsDifferentNode guards the data-loss path:
 // when an updated node's rebuilt body content-hash-collides with a DIFFERENT
-// knowledge item (dedup keys on file_hash alone), the parent row under this
+// knowledge item (dedup keys on file_hash plus file_type), the parent row under this
 // node's external_id no longer exists (it was deleted for the update and never
 // recreated), so the subtree must NOT be swept — deleting the children would
 // destroy them with no parent to replace them.
diff --git a/internal/types/knowledge.go b/internal/types/knowledge.go
index 8b68aafd8..f3955c477 100644
--- a/internal/types/knowledge.go
+++ b/internal/types/knowledge.go
@@ -445,6 +445,7 @@ func (k *Knowledge) SetProcessOverrides(o *KnowledgeProcessOverrides) error {
 type KnowledgeCheckParams struct {
 	// File parameters
 	FileName string
+	// FileType scopes file-hash deduplication; callers checking file uploads should set it.
 	FileType string
 	FileSize int64
 	FileHash string