meta:
  title: "Unlimited-OCR"
  slug: "unlimited-ocr"
  provider: "Ernie (Baidu)"
  description: "Baidu's state-of-the-art document-parsing model with Reference Sliding Window Attention (R-SWA), optimized for full-page OCR and markdown generation."
  date_added: 2026-06-28
  date_updated: 2026-06-28
  tasks:
    - multimodal
  performance_headline: "One-shot long-horizon document parsing to markdown"
  related_recipes:
    - "deepseek-ai/DeepSeek-OCR"

model:
  model_id: "baidu/Unlimited-OCR"
  min_vllm_version: "0.25.0"
  docker_image: "vllm/vllm-openai:unlimited-ocr"
  install:
    pip:
      note: "Unlimited-OCR (UnlimitedOCRForCausalLM) is supported since vLLM v0.25.0."
  architecture: dense
  parameter_count: "3B"
  active_parameters: "3B"
  context_length: 32768
  base_args:
    - "--trust-remote-code"
    - "--logits_processors"
    - "vllm.model_executor.models.unlimited_ocr:NGramPerReqLogitsProcessor"
    - "--no-enable-prefix-caching"
    - "--mm-processor-cache-gb"
    - "0"
  base_env: {}

features:
  encoder_parallel:
    description: "Run the vision encoder in data-parallel mode — avoids TP comm overhead on the small encoder."
    args:
      - "--mm-encoder-tp-mode"
      - "data"

opt_in_features:
  - encoder_parallel

variants:
  default:
    precision: bf16
    vram_minimum_gb: 8
    description: "Full precision BF16 (~3B params)"

compatible_strategies:
  - single_node_tp
  - multi_node_tp

hardware_overrides: {}

strategy_overrides: {}

guide: |
  ## Overview

  [Unlimited-OCR](https://huggingface.co/baidu/Unlimited-OCR) is Baidu's
  DeepSeek-OCR-lineage document-parsing model. It shares the DeepSeek-OCR
  *gundam* vision stack (SAM-ViT-B + CLIP-L DeepEncoder, `base_size=1024` /
  `image_size=640` / crop) and ships with the same n-gram logits processor for
  high-quality, repetition-free document → markdown generation.

  ## Prerequisites

  - **Hardware**: a single GPU with >=8 GB VRAM is enough for BF16 inference.
  - **vLLM**: served from the dedicated release image (the architecture is not yet
    in a stable pip wheel). Pull the image shown in the Install → Docker tab.

  ## Serving recipe (required)

  The model has **no chat template** and is trained for a specific prompt/decode
  recipe — without it the model returns empty output. The required pieces:

  - register the no-repeat-ngram logits processor on the server:
    `--logits_processors vllm.model_executor.models.unlimited_ocr:NGramPerReqLogitsProcessor`
  - prompt text must begin with a literal `<image>` (e.g. `<image>document parsing.`)
  - `skip_special_tokens=False`
  - pass the processor args per request: `ngram_size=35`, `window_size=128`
    (use `window_size=1024` for multi-page / PDF input)

  ## Client Usage

  ### Online OCR serving

  ```bash
  docker run --rm --gpus all --network host --ipc host \
    vllm/vllm-openai:unlimited-ocr \
    baidu/Unlimited-OCR \
    --trust-remote-code \
    --logits_processors vllm.model_executor.models.unlimited_ocr:NGramPerReqLogitsProcessor \
    --no-enable-prefix-caching \
    --mm-processor-cache-gb 0
  ```

  ```python
  import time
  from openai import OpenAI

  client = OpenAI(api_key="EMPTY", base_url="http://localhost:8000/v1", timeout=3600)

  messages = [
      {
          "role": "user",
          "content": [
              {"type": "text", "text": "<image>document parsing."},
              {"type": "image_url", "image_url": {"url": "https://huggingface.co/baidu/Unlimited-OCR/resolve/main/assets/baidu.png"}},
          ],
      }
  ]

  start = time.time()
  response = client.chat.completions.create(
      model="baidu/Unlimited-OCR",
      messages=messages,
      max_tokens=8192,
      temperature=0.0,
      extra_body={
          "skip_special_tokens": False,
          "vllm_xargs": {"ngram_size": 35, "window_size": 128},
      },
  )
  print(f"Response costs: {time.time() - start:.2f}s")
  print(f"Generated text: {response.choices[0].message.content}")
  ```

  The raw output carries `<|ref|>…<|/ref|>` / `<|det|>…<|/det|>` grounding tokens;
  unwrap the `<|ref|>` text and drop the `<|det|>` coordinate boxes to get clean markdown.

  ## Troubleshooting / Configuration Tips

  - **The custom logits processor is required** — without it long documents loop on
    `<|det|>` coordinate tokens.
  - Empty output almost always means the prompt is missing the literal `<image>`
    prefix or `skip_special_tokens` was left `True`.
  - OCR tasks don't benefit from prefix caching / image reuse, so prefix caching and
    the mm-processor cache are disabled in the recipe.
  - Single-image input uses gundam (crop) mode; multi-image requests automatically
    fall back to non-crop (base) mode — use `window_size=1024` for those.

  ## References

  - [Unlimited-OCR on Hugging Face](https://huggingface.co/baidu/Unlimited-OCR)
  - [vLLM multimodal inputs guide](https://docs.vllm.ai/en/latest/features/multimodal_inputs.html#offline-inference)