diff --git a/packages/cdk/lambda/utils/bedrockAgentApi.ts b/packages/cdk/lambda/utils/bedrockAgentApi.ts
index 7a385aa39..6a6f64452 100644
--- a/packages/cdk/lambda/utils/bedrockAgentApi.ts
+++ b/packages/cdk/lambda/utils/bedrockAgentApi.ts
@@ -21,6 +21,7 @@ import {
   BraveSearchResult,
 } from 'generative-ai-use-cases';
 import { streamingChunk } from './streamingChunk';
+import { convertToSafeFilename } from './fileNameUtils';
 import {
   initBedrockAgentClient,
   initBedrockAgentRuntimeClient,
@@ -127,7 +128,7 @@ const bedrockAgentApi: ApiInterface = {
           files: messages
             .flatMap((m: UnrecordedMessage) => {
               return m.extraData?.map((file) => ({
-                name: file.name.replace(/[^a-zA-Z0-9\s\-()[\].]/g, 'X'), // If the file name contains Japanese, it is not recognized, so replace it
+                name: convertToSafeFilename(file.name),
                 source: {
                   sourceType: 'BYTE_CONTENT',
                   byteContent: {
diff --git a/packages/cdk/lambda/utils/fileNameUtils.ts b/packages/cdk/lambda/utils/fileNameUtils.ts
new file mode 100644
index 000000000..6e4160032
--- /dev/null
+++ b/packages/cdk/lambda/utils/fileNameUtils.ts
@@ -0,0 +1,27 @@
+import crypto from 'crypto';
+
+/**
+ * Convert filename to safe format for AWS Bedrock API
+ * AWS Bedrock DocumentBlock.name only allows: alphanumeric, whitespace, hyphens, parentheses, square brackets
+ * Replaces non-allowed characters with '_' and adds hash suffix only when replacements occur
+ * @param filename Original filename
+ * @returns Safe filename with hash suffix (only if non-allowed characters were replaced)
+ */
+export const convertToSafeFilename = (filename: string): string => {
+  const lastDotIndex = filename.lastIndexOf('.');
+  const nameWithoutExt =
+    lastDotIndex > 0 ? filename.substring(0, lastDotIndex) : filename;
+  const safeName = nameWithoutExt.replace(/[^a-zA-Z0-9\s\-()[\]]/g, '_');
+
+  // Add hash only if non-ASCII characters were replaced
+  if (safeName !== nameWithoutExt) {
+    const hash = crypto
+      .createHash('md5')
+      .update(filename)
+      .digest('hex')
+      .substring(0, 8);
+    return `${safeName}_${hash}`;
+  }
+
+  return safeName;
+};
diff --git a/packages/cdk/lambda/utils/models.ts b/packages/cdk/lambda/utils/models.ts
index 2d7dda05c..c11433139 100644
--- a/packages/cdk/lambda/utils/models.ts
+++ b/packages/cdk/lambda/utils/models.ts
@@ -31,6 +31,7 @@ import {
   applyAutoCacheToSystem,
 } from './promptCache';
 import { getFormatFromMimeType, getMimeTypeFromFileName } from './media';
+import { convertToSafeFilename } from './fileNameUtils';
 
 // Default Models
 
@@ -403,9 +404,7 @@ const createConverseCommandInput = (
           contentBlocks.push({
             document: {
               format,
-              name: extra.name
-                .split('.')[0]
-                .replace(/[^a-zA-Z0-9\s\-()[\]]/g, 'X'), // If the file name contains Japanese, it will cause an error, so convert it
+              name: convertToSafeFilename(extra.name),
               source: {
                 bytes: Buffer.from(extra.source.data, 'base64'),
               },
diff --git a/packages/cdk/test/lambda/utils/fileNameUtils.test.ts b/packages/cdk/test/lambda/utils/fileNameUtils.test.ts
new file mode 100644
index 000000000..77eb347d3
--- /dev/null
+++ b/packages/cdk/test/lambda/utils/fileNameUtils.test.ts
@@ -0,0 +1,54 @@
+/* eslint-disable i18nhelper/no-jp-string */
+import { convertToSafeFilename } from '../../../lambda/utils/fileNameUtils';
+
+describe('convertToSafeFilename', () => {
+  it('should return filename without hash when only ASCII characters', () => {
+    const result = convertToSafeFilename('document.pdf');
+    expect(result).toBe('document');
+  });
+
+  it('should return filename without hash for ASCII with allowed special chars', () => {
+    const result = convertToSafeFilename('report-2024 (final)[v1].pdf');
+    expect(result).toBe('report-2024 (final)[v1]');
+  });
+
+  it('should add hash when Japanese characters are present', () => {
+    const result = convertToSafeFilename('資料.pdf');
+    expect(result).toBe('___46a890b2');
+  });
+
+  it('should add hash when mixed Japanese and ASCII characters', () => {
+    const result = convertToSafeFilename('report資料2024.pdf');
+    expect(result).toBe('report__2024_f3805637');
+  });
+
+  it('should generate different hashes for different Japanese filenames with same length', () => {
+    const result1 = convertToSafeFilename('資料.pdf');
+    const result2 = convertToSafeFilename('書類.pdf');
+    expect(result1).toBe('___46a890b2');
+    expect(result2).toBe('___5c4aa342');
+    expect(result1).not.toBe(result2);
+  });
+
+  it('should generate consistent hash for same filename', () => {
+    const result1 = convertToSafeFilename('資料.pdf');
+    const result2 = convertToSafeFilename('資料.pdf');
+    expect(result1).toBe('___46a890b2');
+    expect(result2).toBe('___46a890b2');
+  });
+
+  it('should handle filename without extension', () => {
+    const result = convertToSafeFilename('document');
+    expect(result).toBe('document');
+  });
+
+  it('should handle filename with multiple dots', () => {
+    const result = convertToSafeFilename('report.final.pdf');
+    expect(result).toBe('report_final_8d101382');
+  });
+
+  it('should replace special characters with underscore and add hash', () => {
+    const result = convertToSafeFilename('file@#$.pdf');
+    expect(result).toBe('file____cf25ced4');
+  });
+});