Multipart Upload

Both upload and uploadAndPoll / upload_and_poll automatically use multipart upload for large files. The file is split into chunks and uploaded in parallel, improving reliability and speed. No extra configuration is needed — it just works.

Default Behavior

Files over 100MB automatically use multipart upload. The existing upload calls work without any changes:

const file = await mxbai.stores.files.upload({
  storeIdentifier: "my-knowledge-base",
  file: fs.createReadStream("./large-document.pdf"),
});

file = mxbai.stores.files.upload(
    store_identifier="my-knowledge-base",
    file=Path("./large-document.pdf"),
)

Custom Threshold

Lower the threshold to trigger multipart upload for smaller files:

const file = await mxbai.stores.files.upload({
  storeIdentifier: "my-knowledge-base",
  file: fs.createReadStream("./document.pdf"),
  multipartUpload: {
    threshold: 50 * 1024 * 1024, // 50MB instead of default 100MB
  },
});

from mixedbread.lib.multipart_upload import MultipartUploadOptions

file = mxbai.stores.files.upload(
    store_identifier="my-knowledge-base",
    file=Path("./document.pdf"),
    multipart_upload=MultipartUploadOptions(
        threshold=50 * 1024 * 1024,  # 50MB instead of default 100MB
    ),
)

Custom Concurrency

Control how many parts upload in parallel. The default is 5 concurrent uploads:

const file = await mxbai.stores.files.upload({
  storeIdentifier: "my-knowledge-base",
  file: fs.createReadStream("./large-document.pdf"),
  multipartUpload: {
    concurrency: 10,
  },
});

from mixedbread.lib.multipart_upload import MultipartUploadOptions

file = mxbai.stores.files.upload(
    store_identifier="my-knowledge-base",
    file=Path("./large-document.pdf"),
    multipart_upload=MultipartUploadOptions(
        concurrency=10,
    ),
)

Custom Part Size

Control the size of each chunk. The default part size is 100MB:

const file = await mxbai.stores.files.upload({
  storeIdentifier: "my-knowledge-base",
  file: fs.createReadStream("./large-document.pdf"),
  multipartUpload: {
    partSize: 50 * 1024 * 1024, // 50MB parts
  },
});

from mixedbread.lib.multipart_upload import MultipartUploadOptions

file = mxbai.stores.files.upload(
    store_identifier="my-knowledge-base",
    file=Path("./large-document.pdf"),
    multipart_upload=MultipartUploadOptions(
        part_size=50 * 1024 * 1024,  # 50MB parts
    ),
)

Progress Tracking

Get notified after each part finishes uploading. Works with both upload and uploadAndPoll / upload_and_poll:

Progress Tracking with uploadAndPoll

from pathlib import Path
from mixedbread import Mixedbread
from mixedbread.lib.multipart_upload import MultipartUploadOptions

mxbai = Mixedbread(api_key="YOUR_API_KEY")


def on_part_upload(event):
    pct = round((event.uploaded_bytes / event.total_bytes) * 100)
    print(f"Part {event.part_number}/{event.total_parts} done — {pct}%")


file = mxbai.stores.files.upload_and_poll(
    store_identifier="my-knowledge-base",
    file=Path("./large-document.pdf"),
    multipart_upload=MultipartUploadOptions(
        on_part_upload=on_part_upload,
    ),
)

print(file)

The callback receives a PartUploadEvent with the following fields:

Field	Description
`partNumber` / `part_number`	1-based part number that completed
`totalParts` / `total_parts`	Total number of parts in this upload
`partSize` / `part_size`	Size of this part in bytes
`uploadedBytes` / `uploaded_bytes`	Cumulative bytes uploaded so far
`totalBytes` / `total_bytes`	Total file size in bytes

All Options Together

Combine threshold, part size, concurrency, and progress tracking:

All Multipart Upload Options

from pathlib import Path
from mixedbread import Mixedbread
from mixedbread.lib.multipart_upload import MultipartUploadOptions

mxbai = Mixedbread(api_key="YOUR_API_KEY")


def on_part_upload(event):
    pct = round((event.uploaded_bytes / event.total_bytes) * 100)
    print(f"Part {event.part_number}/{event.total_parts} — {pct}%")


file = mxbai.stores.files.upload(
    store_identifier="my-knowledge-base",
    file=Path("./large-document.pdf"),
    multipart_upload=MultipartUploadOptions(
        threshold=50 * 1024 * 1024,  # 50MB threshold
        part_size=25 * 1024 * 1024,  # 25MB parts
        concurrency=10,
        on_part_upload=on_part_upload,
    ),
)

print(file)

Options Reference

Option	Default	Description
`threshold`	`100MB`	Minimum file size to trigger multipart upload
`partSize` / `part_size`	`100MB`	Size of each upload chunk
`concurrency`	`5`	Number of parts uploaded in parallel
`onPartUpload` / `on_part_upload`	—	Callback invoked after each part completes