add auto_create_bucket defaulting to false, enabled for tests

llama_stack/providers/remote/files/s3/README.md

@@ -108,6 +108,41 @@ The S3 provider requires the following permissions:
 }
 ```
 
+### Automatic Bucket Creation
+
+By default, the S3 provider expects the bucket to already exist. If you want the provider to automatically create the bucket when it doesn't exist, set `auto_create_bucket: true` in your configuration:
+
+```yaml
+config:
+  bucket_name: my-bucket
+  auto_create_bucket: true  # Will create bucket if it doesn't exist
+  region: us-east-1
+```
+
+**Note**: When `auto_create_bucket` is enabled, the provider will need additional permissions:
+
+```json
+{
+  "Version": "2012-10-17",
+  "Statement": [
+    {
+      "Effect": "Allow",
+      "Action": [
+        "s3:GetObject",
+        "s3:PutObject",
+        "s3:DeleteObject",
+        "s3:ListBucket",
+        "s3:CreateBucket"
+      ],
+      "Resource": [
+        "arn:aws:s3:::your-bucket-name",
+        "arn:aws:s3:::your-bucket-name/*"
+      ]
+    }
+  ]
+}
+```
+
 ### Bucket Policy (Optional)
 
 For additional security, you can add a bucket policy:

llama_stack/providers/remote/files/s3/config.py

@@ -21,6 +21,9 @@ class S3FilesImplConfig(BaseModel):
         default=None, description="AWS secret access key (optional if using IAM roles)"
     )
     endpoint_url: str | None = Field(default=None, description="Custom S3 endpoint URL (for MinIO, LocalStack, etc.)")
+    auto_create_bucket: bool = Field(
+        default=False, description="Automatically create the S3 bucket if it doesn't exist"
+    )
     metadata_store: SqlStoreConfig = Field(description="SQL store configuration for file metadata")
 
     @classmethod
@@ -31,6 +34,7 @@ class S3FilesImplConfig(BaseModel):
             "aws_access_key_id": "${env.AWS_ACCESS_KEY_ID:=}",
             "aws_secret_access_key": "${env.AWS_SECRET_ACCESS_KEY:=}",
             "endpoint_url": "${env.S3_ENDPOINT_URL:=}",
+            "auto_create_bucket": "${env.S3_AUTO_CREATE_BUCKET:=false}",
             "metadata_store": SqliteSqlStoreConfig.sample_run_config(
                 __distro_dir__=__distro_dir__,
                 db_name="s3_files_metadata.db",

llama_stack/providers/remote/files/s3/files.py

@@ -59,6 +59,11 @@ async def _create_bucket_if_not_exists(client: boto3.client, config: S3FilesImpl
     except ClientError as e:
         error_code = e.response["Error"]["Code"]
         if error_code == "404":
+            if not config.auto_create_bucket:
+                raise RuntimeError(
+                    f"S3 bucket '{config.bucket_name}' does not exist. "
+                    f"Either create the bucket manually or set 'auto_create_bucket: true' in your configuration."
+                ) from e
             try:
                 # For us-east-1, we can't specify LocationConstraint
                 if config.region == "us-east-1":