diff --git a/lambda-s3-files-sam/README.md b/lambda-s3-files-sam/README.md
new file mode 100644
index 000000000..7bd6a38a6
--- /dev/null
+++ b/lambda-s3-files-sam/README.md
@@ -0,0 +1,138 @@
+# Mount an Amazon S3 Bucket as a File System on AWS Lambda using Amazon S3 Files
+
+This pattern mounts an Amazon S3 bucket as a file system on an AWS Lambda function using **Amazon S3 Files**, enabling standard Python file I/O to read S3 data.
+
+Learn more about this pattern at Serverless Land Patterns: https://serverlessland.com/patterns/lambda-s3-files-sam
+
+Important: this application uses various AWS services and there are costs associated with these services after the Free Tier usage - please see the [AWS Pricing page](https://aws.amazon.com/pricing/) for details. You are responsible for any AWS costs incurred. No warranty is implied in this example.
+
+## Requirements
+
+* [Create an AWS account](https://portal.aws.amazon.com/gp/aws/developer/registration/index.html) if you do not already have one and log in. The IAM user that you use must have sufficient permissions to make necessary AWS service calls and manage AWS resources.
+* [AWS CLI](https://docs.aws.amazon.com/cli/latest/userguide/install-cliv2.html) installed and configured
+* [Git Installed](https://git-scm.com/book/en/v2/Getting-Started-Installing-Git)
+* [AWS Serverless Application Model](https://docs.aws.amazon.com/serverless-application-model/latest/developerguide/serverless-sam-cli-install.html) (AWS SAM) installed
+* [Python 3.14](https://www.python.org/downloads/) installed
+
+## How it works
+
+1. An Amazon S3 bucket is linked to an **S3 file system** (Amazon S3 Files), providing full POSIX file system semantics over S3 data.
+2. A **mount target** is created in a private subnet, giving the Lambda function NFS access to the file system.
+3. The Lambda function is configured with `FileSystemConfigs` pointing to the access point, mounting the S3 bucket at `/mnt/s3data`.
+4. When invoked, AWS Lambda reads a CSV file from `/mnt/s3data/input/` using Python's built-in `csv` module — a standard file path.
+5. It returns the row count, column names, and a preview of the first 5 rows as JSON.
+
+## Build Instructions
+
+```bash
+sam build
+```
+
+No external dependencies — the handler uses Python's built-in `csv` module.
+
+## Deployment Instructions
+
+1. Clone the repository:
+    ```bash
+    git clone https://github.com/aws-samples/serverless-patterns
+    ```
+
+2. Change to the pattern directory:
+    ```bash
+    cd lambda-s3-files-sam
+    ```
+
+3. Build (see Build Instructions above).
+
+4. Deploy:
+    ```bash
+    sam deploy --guided
+    ```
+
+5. During the prompts:
+    * Enter a stack name
+    * Enter the desired AWS Region
+    * Accept the default parameter values or adjust VPC CIDRs if needed
+    * Allow SAM CLI to create IAM roles with the required permissions
+
+    Once you have run `sam deploy --guided` once and saved arguments to `samconfig.toml`, you can use `sam deploy` for future deployments.
+
+6. Note the outputs — you will need `DataBucketName` and `S3FilesReaderFunctionName` for testing.
+
+## Testing
+
+### Unit tests (no AWS access required)
+
+```bash
+python3 -m venv .venv
+source .venv/bin/activate   # Windows: .venv\Scripts\activate
+pip install pytest
+pytest src/tests/ -v
+```
+
+### Integration test against a deployed stack
+
+#### 1. Upload the sample CSV
+
+```bash
+BUCKET=$(aws cloudformation describe-stacks \
+  --stack-name <your-stack-name> \
+  --query "Stacks[0].Outputs[?OutputKey=='DataBucketName'].OutputValue" \
+  --output text)
+
+aws s3 cp src/tests/sample_sales.csv s3://$BUCKET/lambda/input/sample_sales.csv
+```
+
+#### 2. Invoke the Lambda function
+
+```bash
+FUNCTION=$(aws cloudformation describe-stacks \
+  --stack-name <your-stack-name> \
+  --query "Stacks[0].Outputs[?OutputKey=='S3FilesReaderFunctionName'].OutputValue" \
+  --output text)
+
+aws lambda invoke \
+  --function-name $FUNCTION \
+  --payload '{"file": "input/sample_sales.csv"}' \
+  --cli-binary-format raw-in-base64-out \
+  response.json
+
+cat response.json
+```
+
+Expected response:
+
+```json
+{
+  "statusCode": 200,
+  "body": {
+    "file": "/mnt/s3data/input/sample_sales.csv",
+    "rows": 10,
+    "columns": ["region", "revenue", "units"],
+    "preview": [...]
+  }
+}
+```
+
+#### 3. Check Lambda logs
+
+```bash
+sam logs --stack-name <your-stack-name> --tail
+```
+
+## Cleanup
+
+1. Delete the stack:
+    ```bash
+    aws cloudformation delete-stack --stack-name STACK_NAME
+    ```
+
+2. Confirm the stack has been deleted:
+    ```bash
+    aws cloudformation list-stacks --query "StackSummaries[?contains(StackName,'STACK_NAME')].StackStatus"
+    ```
+
+----
+Copyright 2026 Amazon.com, Inc. or its affiliates. All Rights Reserved.
+
+SPDX-License-Identifier: MIT-0
diff --git a/lambda-s3-files-sam/example-pattern.json b/lambda-s3-files-sam/example-pattern.json
new file mode 100644
index 000000000..33eb2ba96
--- /dev/null
+++ b/lambda-s3-files-sam/example-pattern.json
@@ -0,0 +1,67 @@
+{
+  "title": "Amazon S3 Bucket as a File System on AWS Lambda with Amazon S3 Files",
+  "description": "This pattern mounts an Amazon S3 bucket as a file system on AWS Lambda using Amazon S3 Files. Read data with standard Python file I/O.",
+  "language": "Python",
+  "level": "200",
+  "framework": "AWS SAM",
+  "introBox": {
+    "headline": "How it works",
+    "text": [
+      "Amazon S3 Files is a shared file system built on Amazon EFS that provides full POSIX file system semantics over your S3 data. It lets file-based applications, agents, and tools work directly with S3 data without duplicating it or learning new APIs.",
+      "This pattern links an S3 bucket to an S3 file system and mounts it on a Lambda function at /mnt/s3data. When invoked, the Lambda function reads a CSV file from the mount path — all through standard Python file I/O, with no boto3 S3 calls.",
+      "This pattern deploys one Amazon S3 bucket, one Amazon S3 file system, one mount target, one Amazon S3 Files access point, one AWS Lambda function, and a VPC with a private subnet and VPC endpoints for Amazon S3."
+    ]
+  },
+  "gitHub": {
+    "template": {
+      "repoURL": "https://github.com/aws-samples/serverless-patterns/tree/main/lambda-s3-files-sam",
+      "templateURL": "serverless-patterns/lambda-s3-files-sam",
+      "projectFolder": "lambda-s3-files-sam",
+      "templateFile": "template.yaml"
+    }
+  },
+  "resources": {
+    "bullets": [
+      {
+        "text": "Amazon S3 Files — product page",
+        "link": "https://aws.amazon.com/s3/features/files/"
+      },
+      {
+        "text": "Working with Amazon S3 Files — documentation",
+        "link": "https://docs.aws.amazon.com/AmazonS3/latest/userguide/s3-files.html"
+      },
+      {
+        "text": "Mounting S3 file systems on AWS Lambda functions",
+        "link": "https://docs.aws.amazon.com/AmazonS3/latest/userguide/s3-files-mounting-lambda.html"
+      },
+      {
+        "text": "Configuring file system access for Lambda functions",
+        "link": "https://docs.aws.amazon.com/lambda/latest/dg/configuration-filesystem.html"
+      }
+    ]
+  },
+  "deploy": {
+    "text": [
+      "sam build",
+      "sam deploy --guided"
+    ]
+  },
+  "testing": {
+    "text": [
+      "See the GitHub repo for detailed testing instructions."
+    ]
+  },
+  "cleanup": {
+    "text": [
+      "Delete the stack: <code>aws cloudformation delete-stack --stack-name STACK_NAME</code>."
+    ]
+  },
+  "authors": [
+    {
+      "name": "Serda Kasaci Yildirim",
+      "image": "https://drive.google.com/file/d/1rzVS1hrIMdqy6P9i7-o7OBLNc0xY0FVB/view?usp=sharing",
+      "bio": "Serda is a Solutions Architect at Amazon Web Services based in Vienna, focused on serverless technologies, event-driven architecture, and application modernization.",
+      "linkedin": "serdakasaci"
+    }
+  ]
+}
diff --git a/lambda-s3-files-sam/lambda-s3-files-sam.json b/lambda-s3-files-sam/lambda-s3-files-sam.json
new file mode 100644
index 000000000..ffd6cf69b
--- /dev/null
+++ b/lambda-s3-files-sam/lambda-s3-files-sam.json
@@ -0,0 +1,86 @@
+{
+    "title": "Amazon S3 Bucket as a File System on AWS Lambda with Amazon S3 Files",
+    "description": "This pattern mounts an Amazon S3 bucket as a file system on AWS Lambda using Amazon S3 Files. Read data with standard Python file I/O.",
+    "language": "Python",
+    "level": "200",
+    "framework": "AWS SAM",
+    "introBox": {
+        "headline": "How it works",
+        "text": [
+            "Amazon S3 Files is a shared file system built on Amazon EFS that provides full POSIX file system semantics over your S3 data. It lets file-based applications, agents, and tools work directly with S3 data without duplicating it or learning new APIs.",
+            "This pattern links an S3 bucket to an S3 file system and mounts it on a Lambda function at /mnt/s3data. When invoked, the Lambda function reads a CSV file from the mount path — all through standard Python file I/O, with no boto3 S3 calls.",
+            "This pattern deploys one Amazon S3 bucket, one Amazon S3 file system, one mount target, one Amazon S3 Files access point, one AWS Lambda function, and a VPC with a private subnet and VPC endpoints for Amazon S3."
+        ]
+    },
+    "gitHub": {
+        "template": {
+            "repoURL": "https://github.com/aws-samples/serverless-patterns/tree/main/lambda-s3-files-sam",
+            "templateURL": "serverless-patterns/lambda-s3-files-sam",
+            "projectFolder": "lambda-s3-files-sam",
+            "templateFile": "template.yaml"
+        }
+    },
+    "resources": {
+        "bullets": [
+            {
+                "text": "Amazon S3 Files — product page",
+                "link": "https://aws.amazon.com/s3/features/files/"
+            },
+            {
+                "text": "Working with Amazon S3 Files — documentation",
+                "link": "https://docs.aws.amazon.com/AmazonS3/latest/userguide/s3-files.html"
+            },
+            {
+                "text": "Mounting S3 file systems on AWS Lambda functions",
+                "link": "https://docs.aws.amazon.com/AmazonS3/latest/userguide/s3-files-mounting-lambda.html"
+            },
+            {
+                "text": "Configuring file system access for Lambda functions",
+                "link": "https://docs.aws.amazon.com/lambda/latest/dg/configuration-filesystem.html"
+            }
+        ]
+    },
+    "deploy": {
+        "text": [
+            "sam build",
+            "sam deploy --guided"
+        ]
+    },
+    "testing": {
+        "text": [
+            "See the GitHub repo for detailed testing instructions."
+        ]
+    },
+    "cleanup": {
+        "text": [
+            "Delete the stack: <code>aws cloudformation delete-stack --stack-name STACK_NAME</code>."
+        ]
+    },
+    "authors": [
+        {
+            "name": "Serda Kasaci Yildirim",
+            "image": "https://drive.google.com/file/d/1rzVS1hrIMdqy6P9i7-o7OBLNc0xY0FVB/view?usp=sharing",
+            "bio": "Serda is a Solutions Architect at Amazon Web Services based in Vienna, focused on serverless technologies, event-driven architecture, and application modernization.",
+            "linkedin": "serdakasaci"
+        }
+    ],
+    "patternArch": {
+        "icon1": {
+            "x": 20,
+            "y": 50,
+            "service": "lambda",
+            "label": "AWS Lambda"
+        },
+        "icon2": {
+            "x": 80,
+            "y": 50,
+            "service": "s3",
+            "label": "Amazon S3 Files"
+        },
+        "line1": {
+            "from": "icon1",
+            "to": "icon2",
+            "label": ""
+        }
+    }
+}
diff --git a/lambda-s3-files-sam/src/handler.py b/lambda-s3-files-sam/src/handler.py
new file mode 100644
index 000000000..a97c85717
--- /dev/null
+++ b/lambda-s3-files-sam/src/handler.py
@@ -0,0 +1,54 @@
+"""
+Amazon S3 Files + AWS Lambda
+
+Demonstrates accessing an Amazon S3 bucket as a file system from AWS Lambda using
+Amazon S3 Files. Files are read and written via standard Python file I/O
+at the local mount path.
+
+The Amazon S3 bucket is mounted at /mnt/s3data via the Amazon S3 Files file system.
+"""
+
+import csv
+import json
+import logging
+import os
+
+logger = logging.getLogger()
+logger.setLevel(os.environ.get("LOG_LEVEL", "INFO"))
+
+MOUNT_PATH = os.environ.get("MOUNT_PATH", "/mnt/s3data")
+
+
+def lambda_handler(event, context):
+    """
+    Expected event:
+    {
+        "file": "input/sample_sales.csv"  # path relative to the S3 Files mount root
+    }
+    """
+    file_key = event.get("file")
+    if not file_key:
+        return {"statusCode": 400, "body": {"error": "Missing required field: 'file'"}}
+
+    input_path = os.path.join(MOUNT_PATH, file_key)
+
+    if not os.path.exists(input_path):
+        return {"statusCode": 404, "body": {"error": f"File not found: {input_path}"}}
+
+    # Read the CSV directly from the S3 Files mount using standard file I/O
+    with open(input_path, newline="") as f:
+        reader = csv.DictReader(f)
+        columns = reader.fieldnames or []
+        rows = list(reader)
+
+    logger.info("Read %s: %d rows, %d columns", input_path, len(rows), len(columns))
+
+    return {
+        "statusCode": 200,
+        "body": {
+            "file": input_path,
+            "rows": len(rows),
+            "columns": columns,
+            "preview": rows[:5],
+        },
+    }
diff --git a/lambda-s3-files-sam/src/tests/sample_sales.csv b/lambda-s3-files-sam/src/tests/sample_sales.csv
new file mode 100644
index 000000000..a9a6133a4
--- /dev/null
+++ b/lambda-s3-files-sam/src/tests/sample_sales.csv
@@ -0,0 +1,11 @@
+region,revenue,units
+North,1000,10
+South,2000,20
+North,500,5
+East,750,8
+South,300,3
+West,1200,15
+East,900,12
+West,450,6
+North,800,9
+South,1100,11
diff --git a/lambda-s3-files-sam/src/tests/test_handler.py b/lambda-s3-files-sam/src/tests/test_handler.py
new file mode 100644
index 000000000..15b0b4047
--- /dev/null
+++ b/lambda-s3-files-sam/src/tests/test_handler.py
@@ -0,0 +1,145 @@
+"""
+Unit tests for handler.py
+
+The Aamzon S3 Files mount is simulated using pytest's tmp_path fixture,
+so no real AWS infrastructure is needed to run these tests.
+
+Run:
+    pip install pytest
+    pytest src/tests/ -v
+"""
+
+import os
+import sys
+
+import pytest
+
+# Make src/ importable
+sys.path.insert(0, os.path.join(os.path.dirname(__file__), ".."))
+
+SALES_CSV = """\
+region,revenue,units
+North,1000,10
+South,2000,20
+North,500,5
+East,750,8
+South,300,3
+"""
+
+
+# ---------------------------------------------------------------------------
+# Fixtures
+# ---------------------------------------------------------------------------
+
+@pytest.fixture(autouse=True)
+def patch_mount(tmp_path, monkeypatch):
+    """Point MOUNT_PATH at a temp directory and reset the module constant."""
+    import handler
+    mount_dir = tmp_path / "s3data"
+    mount_dir.mkdir()
+    monkeypatch.setenv("MOUNT_PATH", str(mount_dir))
+    handler.MOUNT_PATH = str(mount_dir)
+    return mount_dir
+
+
+@pytest.fixture()
+def mount(tmp_path):
+    return tmp_path / "s3data"
+
+
+@pytest.fixture()
+def sales_file(mount):
+    """Write a standard sales CSV into the mock mount's input/ directory."""
+    csv_path = mount / "input" / "sales.csv"
+    csv_path.parent.mkdir(parents=True, exist_ok=True)
+    csv_path.write_text(SALES_CSV)
+    return mount
+
+
+# ---------------------------------------------------------------------------
+# Happy path
+# ---------------------------------------------------------------------------
+
+class TestHappyPath:
+
+    def test_returns_200(self, sales_file):
+        import handler
+        handler.MOUNT_PATH = str(sales_file)
+        result = handler.lambda_handler({"file": "input/sales.csv"}, {})
+        assert result["statusCode"] == 200
+
+    def test_row_count_is_correct(self, sales_file):
+        import handler
+        handler.MOUNT_PATH = str(sales_file)
+        result = handler.lambda_handler({"file": "input/sales.csv"}, {})
+        assert result["body"]["rows"] == 5
+
+    def test_columns_are_returned(self, sales_file):
+        import handler
+        handler.MOUNT_PATH = str(sales_file)
+        result = handler.lambda_handler({"file": "input/sales.csv"}, {})
+        assert result["body"]["columns"] == ["region", "revenue", "units"]
+
+    def test_preview_contains_up_to_5_rows(self, sales_file):
+        import handler
+        handler.MOUNT_PATH = str(sales_file)
+        result = handler.lambda_handler({"file": "input/sales.csv"}, {})
+        assert len(result["body"]["preview"]) == 5
+
+    def test_preview_capped_at_5_for_large_file(self, mount):
+        """Files with more than 5 rows should still return only 5 in preview."""
+        import handler
+        handler.MOUNT_PATH = str(mount)
+        csv_path = mount / "input" / "big.csv"
+        csv_path.parent.mkdir(parents=True, exist_ok=True)
+        rows = "id,value\n" + "\n".join(f"{i},{i*10}" for i in range(20))
+        csv_path.write_text(rows)
+        result = handler.lambda_handler({"file": "input/big.csv"}, {})
+        assert len(result["body"]["preview"]) == 5
+
+    def test_file_path_in_response(self, sales_file):
+        import handler
+        handler.MOUNT_PATH = str(sales_file)
+        result = handler.lambda_handler({"file": "input/sales.csv"}, {})
+        assert "input/sales.csv" in result["body"]["file"]
+
+    def test_preview_values_are_strings(self, sales_file):
+        """csv.DictReader returns all values as strings."""
+        import handler
+        handler.MOUNT_PATH = str(sales_file)
+        result = handler.lambda_handler({"file": "input/sales.csv"}, {})
+        first_row = result["body"]["preview"][0]
+        assert first_row["region"] == "North"
+        assert first_row["revenue"] == "1000"
+
+
+# ---------------------------------------------------------------------------
+# Input validation
+# ---------------------------------------------------------------------------
+
+class TestInputValidation:
+
+    def test_missing_file_field_returns_400(self, mount):
+        import handler
+        handler.MOUNT_PATH = str(mount)
+        result = handler.lambda_handler({}, {})
+        assert result["statusCode"] == 400
+        assert "file" in result["body"]["error"].lower()
+
+    def test_empty_event_returns_400(self, mount):
+        import handler
+        handler.MOUNT_PATH = str(mount)
+        result = handler.lambda_handler({}, {})
+        assert result["statusCode"] == 400
+
+    def test_file_not_found_returns_404(self, mount):
+        import handler
+        handler.MOUNT_PATH = str(mount)
+        result = handler.lambda_handler({"file": "input/missing.csv"}, {})
+        assert result["statusCode"] == 404
+
+    def test_404_error_message_contains_path(self, mount):
+        import handler
+        handler.MOUNT_PATH = str(mount)
+        result = handler.lambda_handler({"file": "input/missing.csv"}, {})
+        assert "missing.csv" in result["body"]["error"]
diff --git a/lambda-s3-files-sam/template.yaml b/lambda-s3-files-sam/template.yaml
new file mode 100644
index 000000000..df30180b4
--- /dev/null
+++ b/lambda-s3-files-sam/template.yaml
@@ -0,0 +1,278 @@
+AWSTemplateFormatVersion: '2010-09-09'
+Transform: AWS::Serverless-2016-10-31
+Description: >
+  Mount an Amazon S3 Bucket as a file system on AWS Lambda using Amazon S3 Files. Read
+  CSV files using standard Python file I/O at /mnt/s3data.
+
+Globals:
+  Function:
+    Runtime: python3.14
+    Architectures:
+      - x86_64
+    Timeout: 60
+    MemorySize: 512
+    Environment:
+      Variables:
+        MOUNT_PATH: /mnt/s3data
+        LOG_LEVEL: INFO
+
+Parameters:
+  VpcCidr:
+    Type: String
+    Default: 10.0.0.0/16
+    Description: CIDR block for the VPC
+
+  PrivateSubnetCidr:
+    Type: String
+    Default: 10.0.1.0/24
+    Description: CIDR for the private subnet (Lambda and mount target)
+
+Resources:
+
+  # -----------------------------------------------------------------------
+  # VPC
+  # -----------------------------------------------------------------------
+  VPC:
+    Type: AWS::EC2::VPC
+    Properties:
+      CidrBlock: !Ref VpcCidr
+      EnableDnsSupport: true
+      EnableDnsHostnames: true
+      Tags:
+        - Key: Name
+          Value: !Sub "${AWS::StackName}-vpc"
+
+  PrivateSubnet:
+    Type: AWS::EC2::Subnet
+    Properties:
+      VpcId: !Ref VPC
+      CidrBlock: !Ref PrivateSubnetCidr
+      AvailabilityZone: !Select ["0", !GetAZs ""]
+      Tags:
+        - Key: Name
+          Value: !Sub "${AWS::StackName}-private-subnet"
+
+  PrivateRouteTable:
+    Type: AWS::EC2::RouteTable
+    Properties:
+      VpcId: !Ref VPC
+
+  PrivateSubnetRouteTableAssociation:
+    Type: AWS::EC2::SubnetRouteTableAssociation
+    Properties:
+      SubnetId: !Ref PrivateSubnet
+      RouteTableId: !Ref PrivateRouteTable
+
+  # -----------------------------------------------------------------------
+  # Security Groups
+  # -----------------------------------------------------------------------
+  LambdaSecurityGroup:
+    Type: AWS::EC2::SecurityGroup
+    Properties:
+      GroupDescription: Security group for Lambda function
+      VpcId: !Ref VPC
+      SecurityGroupEgress:
+        - IpProtocol: tcp
+          FromPort: 443
+          ToPort: 443
+          CidrIp: !Ref VpcCidr
+          Description: HTTPS outbound to VPC endpoints
+        - IpProtocol: tcp
+          FromPort: 2049
+          ToPort: 2049
+          CidrIp: !Ref VpcCidr
+          Description: NFS outbound to S3 Files mount target
+      Tags:
+        - Key: Name
+          Value: !Sub "${AWS::StackName}-lambda-sg"
+
+  MountTargetSecurityGroup:
+    Type: AWS::EC2::SecurityGroup
+    Properties:
+      GroupDescription: Security group for S3 Files mount target
+      VpcId: !Ref VPC
+      SecurityGroupIngress:
+        - IpProtocol: tcp
+          FromPort: 2049
+          ToPort: 2049
+          SourceSecurityGroupId: !Ref LambdaSecurityGroup
+          Description: NFS inbound from Lambda
+      Tags:
+        - Key: Name
+          Value: !Sub "${AWS::StackName}-mount-target-sg"
+
+  # -----------------------------------------------------------------------
+  # VPC Endpoints — keep all traffic on the AWS network
+  # -----------------------------------------------------------------------
+
+  # S3 Gateway Endpoint — free, routes S3 API traffic via the route table
+  S3GatewayEndpoint:
+    Type: AWS::EC2::VPCEndpoint
+    Properties:
+      VpcId: !Ref VPC
+      ServiceName: !Sub "com.amazonaws.${AWS::Region}.s3"
+      VpcEndpointType: Gateway
+      RouteTableIds:
+        - !Ref PrivateRouteTable
+
+  # S3 Files Interface Endpoint — for NFS mount operations
+  S3FilesInterfaceEndpoint:
+    Type: AWS::EC2::VPCEndpoint
+    Properties:
+      VpcId: !Ref VPC
+      ServiceName: !Sub "com.amazonaws.${AWS::Region}.s3-outposts"
+      VpcEndpointType: Interface
+      SubnetIds:
+        - !Ref PrivateSubnet
+      SecurityGroupIds:
+        - !Ref LambdaSecurityGroup
+      PrivateDnsEnabled: true
+
+  # -----------------------------------------------------------------------
+  # S3 Bucket
+  # -----------------------------------------------------------------------
+  DataBucket:
+    Type: AWS::S3::Bucket
+    Properties:
+      VersioningConfiguration:
+        Status: Enabled
+      Tags:
+        - Key: Pattern
+          Value: s3files-lambda
+
+  # -----------------------------------------------------------------------
+  # IAM Role — grants S3 Files service access to the S3 bucket
+  # -----------------------------------------------------------------------
+  S3FilesRole:
+    Type: AWS::IAM::Role
+    Properties:
+      AssumeRolePolicyDocument:
+        Version: "2012-10-17"
+        Statement:
+          - Sid: AllowS3FilesAssumeRole
+            Effect: Allow
+            Principal:
+              Service: elasticfilesystem.amazonaws.com
+            Action: sts:AssumeRole
+            Condition:
+              StringEquals:
+                aws:SourceAccount: !Ref AWS::AccountId
+              ArnLike:
+                aws:SourceArn: !Sub "arn:aws:s3files:${AWS::Region}:${AWS::AccountId}:file-system/*"
+      Policies:
+        - PolicyName: S3FilesAccess
+          PolicyDocument:
+            Version: "2012-10-17"
+            Statement:
+              - Effect: Allow
+                Action:
+                  - s3:GetObject
+                  - s3:PutObject
+                  - s3:DeleteObject
+                  - s3:HeadObject
+                  - s3:ListBucket
+                  - s3:GetBucketLocation
+                  - s3:GetBucketVersioning
+                  - s3:ListBucketVersions
+                  - s3:GetObjectVersion
+                  - s3:DeleteObjectVersion
+                Resource:
+                  - !GetAtt DataBucket.Arn
+                  - !Sub "${DataBucket.Arn}/*"
+
+  # -----------------------------------------------------------------------
+  # S3 Files resources
+  # -----------------------------------------------------------------------
+  S3FileSystem:
+    Type: AWS::S3Files::FileSystem
+    Properties:
+      Bucket: !GetAtt DataBucket.Arn
+      RoleArn: !GetAtt S3FilesRole.Arn
+      Tags:
+        - Key: Pattern
+          Value: s3files-lambda
+
+  MountTarget:
+    Type: AWS::S3Files::MountTarget
+    Properties:
+      FileSystemId: !GetAtt S3FileSystem.FileSystemId
+      SubnetId: !Ref PrivateSubnet
+      SecurityGroups:
+        - !Ref MountTargetSecurityGroup
+
+  AccessPoint:
+    Type: AWS::S3Files::AccessPoint
+    Properties:
+      FileSystemId: !GetAtt S3FileSystem.FileSystemId
+      PosixUser:
+        Uid: "1000"
+        Gid: "1000"
+      RootDirectory:
+        Path: /lambda
+        CreationPermissions:
+          OwnerUid: "1000"
+          OwnerGid: "1000"
+          Permissions: "755"
+      Tags:
+        - Key: Pattern
+          Value: s3files-lambda
+
+  # -----------------------------------------------------------------------
+  # Lambda Function
+  # -----------------------------------------------------------------------
+  S3FilesReaderFunction:
+    Type: AWS::Serverless::Function
+    DependsOn: MountTarget
+    Properties:
+      FunctionName: !Sub "${AWS::StackName}-s3files-reader"
+      CodeUri: src/
+      Handler: handler.lambda_handler
+      Description: >
+        Reads a CSV from /mnt/s3data/input/ using Python's built-in csv module
+        and returns the row count, column names, and a preview of the first 5
+        rows — all via standard file I/O through the Amazon S3 Files mount.
+      FileSystemConfigs:
+        - Arn: !GetAtt AccessPoint.AccessPointArn
+          LocalMountPath: /mnt/s3data
+      VpcConfig:
+        SubnetIds:
+          - !Ref PrivateSubnet
+        SecurityGroupIds:
+          - !Ref LambdaSecurityGroup
+      Policies:
+        - Statement:
+            - Sid: S3FilesMount
+              Effect: Allow
+              Action:
+                - s3files:ClientMount
+                - s3files:ClientWrite
+              Resource: "*"
+            - Sid: S3DirectRead
+              Effect: Allow
+              Action:
+                - s3:GetObject
+                - s3:GetObjectVersion
+              Resource: !Sub "${DataBucket.Arn}/*"
+      Tags:
+        Pattern: s3files-lambda
+
+Outputs:
+  DataBucketName:
+    Description: S3 bucket linked to the file system — upload CSV files here
+    Value: !Ref DataBucket
+
+  S3FileSystemId:
+    Description: S3 file system ID
+    Value: !GetAtt S3FileSystem.FileSystemId
+
+  S3FilesReaderFunctionName:
+    Description: Lambda function name — use this to invoke for testing
+    Value: !Ref S3FilesReaderFunction
+
+  S3FilesReaderFunctionArn:
+    Description: Lambda function ARN
+    Value: !GetAtt S3FilesReaderFunction.Arn
+
+  MountPath:
+    Description: Local mount path inside Lambda
+    Value: /mnt/s3data