diff --git a/internal/application/repository/knowledge.go b/internal/application/repository/knowledge.go
index 79b9a36ae..831d4d063 100644
--- a/internal/application/repository/knowledge.go
+++ b/internal/application/repository/knowledge.go
@@ -241,10 +241,16 @@ func (r *knowledgeRepository) CheckKnowledgeExists(
 
 	switch params.Type {
 	case "file":
-		// If file hash exists, prioritize exact match using hash
+		// File content is only a duplicate within the same file type. This keeps
+		// same-content documents with distinct formats (for example, .md and
+		// .txt) available as separate knowledge items.
 		if params.FileHash != "" {
 			var knowledge types.Knowledge
-			err := query.Where("file_hash = ?", params.FileHash).First(&knowledge).Error
+			duplicateQuery := query.Where("type = ? AND file_hash = ?", "file", params.FileHash)
+			if params.FileType != "" {
+				duplicateQuery = duplicateQuery.Where("file_type = ?", 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
new file mode 100644
index 000000000..55ae0a230
--- /dev/null
+++ b/internal/application/repository/knowledge_duplicate_test.go
@@ -0,0 +1,50 @@
+package repository
+
+import (
+	"context"
+	"testing"
+
+	"github.com/Tencent/WeKnora/internal/types"
+	"github.com/google/uuid"
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+)
+
+func TestCheckKnowledgeExists_FileHashIsScopedByFileType(t *testing.T) {
+	db := setupKnowledgeTestDB(t)
+	repo := NewKnowledgeRepository(db)
+	ctx := context.Background()
+	tenantID := uint64(1)
+	kbID := uuid.NewString()
+	const fileHash = "same-content-hash"
+
+	require.NoError(t, db.Exec(`
+		INSERT INTO knowledges (id, tenant_id, knowledge_base_id, type, title, file_name, file_type, file_hash, parse_status)
+		VALUES (?, ?, ?, 'file', 'document.md', 'document.md', 'md', ?, 'completed')
+	`, uuid.NewString(), tenantID, kbID, fileHash).Error)
+
+	t.Run("same content with another file type is allowed", func(t *testing.T) {
+		exists, knowledge, err := repo.CheckKnowledgeExists(ctx, tenantID, kbID, &types.KnowledgeCheckParams{
+			Type:     "file",
+			FileHash: fileHash,
+			FileType: "txt",
+		})
+
+		require.NoError(t, err)
+		assert.False(t, exists)
+		assert.Nil(t, knowledge)
+	})
+
+	t.Run("same content and file type remains a duplicate", 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/knowledge_create.go b/internal/application/service/knowledge_create.go
index 84f5393c9..fc5523405 100644
--- a/internal/application/service/knowledge_create.go
+++ b/internal/application/service/knowledge_create.go
@@ -82,6 +82,7 @@ func (s *knowledgeService) CreateKnowledgeFromFile(ctx context.Context,
 	exists, existingKnowledge, err := s.repo.CheckKnowledgeExists(ctx, tenantID, kbID, &types.KnowledgeCheckParams{
 		Type:     "file",
 		FileName: fileName,
+		FileType: getFileType(fileName),
 		FileSize: file.Size,
 		FileHash: hash,
 	})
diff --git a/internal/types/knowledge.go b/internal/types/knowledge.go
index 461a618dd..8b68aafd8 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 string
 	FileSize int64
 	FileHash string
 	// URL parameters