ocr / serving-unlimited-ocr.md
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Serve Unlimited-OCR as a live endpoint on HF Jobs

The OCR recipes in this folder run as batch jobs (dataset in → dataset out). To call a model interactively, from an agent, or with ad-hoc concurrent requests, you can instead run it as a temporary HTTP endpoint. HF Jobs serving exposes a port on a GPU Job, giving an OpenAI-compatible endpoint that runs until the job is cancelled or its --timeout is reached.

This is a worked example for baidu/Unlimited-OCR (3B, MIT, based on DeepSeek-OCR; supports multi-page parsing in a single request). Two server options below: vLLM on Baidu's official image (the newer official path, OpenAI-compatible), or SGLang on the stock image with the model's own wheel. Either gives an OpenAI-compatible endpoint.

Single-image vs multi-page — pick the engine by task:

  • Single-page OCR (one image → markdown): both engines work. For a whole corpus, the batch recipe unlimited-ocr-vllm.py (offline vLLM, resumable, no network) is the better fit than a client loop; for interactive/agent use, serve with vLLM (Option A).
  • Multi-page / long-horizon parsing (the model's headline feature): both engines do it (validated 2026-06-28 — a clean 2-page doc read back both pages, <PAGE>-separated, on both vLLM and SGLang). The difference is robustness on hard inputs: on degraded historical scans / newspaper clippings, vLLM multi-page degraded to hallucination in our tests while SGLang (Option B) read real content — so SGLang is the more robust multi-page path (it's also the authors' documented one, via images_config). Use vLLM multi-page for clean docs; reach for SGLang for hard scans. (vLLM's upstream PR #46564 benchmarks single-page only.)

1. Start the server

Option A — vLLM (official image)

vLLM support landed upstream; Baidu ships a dedicated image (the architecture isn't in a stable pip wheel yet). Use the default :unlimited-ocr tag on L4/A100, or :unlimited-ocr-cu129 on Hopper. Runs on l4x1, no fa3/Hopper requirement. Single-image is validated; multi-page also works on clean docs (both pages, <PAGE>-separated) but degraded to hallucination on hard scans in our tests — for hard/degraded inputs prefer Option B (SGLang). For multi-page on vLLM, the request takes one <image> per page in the text and window_size=1024 in vllm_xargs (it has no images_config).

hf jobs run --detach --expose 8000 --flavor l4x1 -s HF_TOKEN --timeout 30m \
  vllm/vllm-openai:unlimited-ocr -- \
  vllm serve baidu/Unlimited-OCR --served-model-name Unlimited-OCR \
    --trust-remote-code --max-model-len 32768 --host 0.0.0.0 --port 8000 \
    --logits_processors vllm.model_executor.models.unlimited_ocr:NGramPerReqLogitsProcessor \
    --no-enable-prefix-caching --mm-processor-cache-gb 0

Per-request, vLLM takes the no-repeat n-gram knobs via vllm_xargs and needs skip_special_tokens off (it has no images_config — that's an SGLang param):

r = client.chat.completions.create(
    model="Unlimited-OCR",
    messages=[{"role": "user", "content": [
        {"type": "text", "text": "<image>document parsing."},  # literal <image> prefix is required
        {"type": "image_url", "image_url": {"url": f"data:image/jpeg;base64,{img}"}},
    ]}],
    temperature=0,
    extra_body={"skip_special_tokens": False, "vllm_xargs": {"ngram_size": 35, "window_size": 128}},
)

Option B — SGLang (model's own build) · supports multi-page

The model also ships its own SGLang build, installed at startup from a 12 MB wheel. This is the more robust path for multi-page / long-horizon parsing (§3) — the model authors' documented route (images_config), and the one that held up on hard scans where vLLM multi-page hallucinated. Two pins matter (both learned the hard way, 2026-06-28):

  • Pin the image to lmsysorg/sglang:v0.5.10.post1not :latest. :latest drifted to torch 2.11 / cu130, incompatible with the wheel (torch 2.9.1 / cuda-python 12.9); v0.5.10.post1 is the last release that matches the wheel exactly.
  • Run on a100-large with --attention-backend flashinfer, not h200/fa3. fa3 needs a Hopper GPU, but HF's h200 nodes currently fail GPU init with CUDA error 802: system not yet initialized (3/3 attempts) — an infra issue, not the model. a100 + flashinfer sidesteps it and works.
hf jobs run --detach --expose 10000 --flavor a100-large -s HF_TOKEN --timeout 30m \
  lmsysorg/sglang:v0.5.10.post1 -- \
  bash -lc 'pip install --no-deps https://github.com/baidu/Unlimited-OCR/raw/main/wheel/sglang-0.0.0.dev11416+g92e8bb79e-py3-none-any.whl \
    && pip install -q kernels==0.11.7 \
    && python -m sglang.launch_server --model baidu/Unlimited-OCR --served-model-name Unlimited-OCR \
       --attention-backend flashinfer --page-size 1 --mem-fraction-static 0.85 --context-length 32768 \
       --enable-custom-logit-processor --disable-overlap-schedule --skip-server-warmup \
       --host 0.0.0.0 --port 10000'

Notes:

  • -- before bash is required, or the CLI parses -lc as its own flags.
  • --timeout stops the endpoint (and billing) at the deadline; hf jobs cancel <id> stops it earlier.
  • Validated 2026-06-28 on a100-large: server came up, single-image and multi-page both read correctly (a clean 2-page doc returned both pages verbatim, <PAGE>-separated). The model card's "official" backend is fa3 on Hopper for exact R-SWA — switch back to --attention-backend fa3 --flavor h200 once the h200 802 infra issue clears; flashinfer on a100 is the working fallback.
  • Follow startup with hf jobs logs -f <id>; ready at The server is fired up / Application startup complete (a few minutes cold; the wheel + model download dominate).

The client examples below use the SGLang request format (images_config in extra_body, port 10000). The single-image call (§2) also works on the vLLM server — just use the Option A extra_body and your exposed port. Multi-page (§3) is SGLang-only.

2. Call it (OpenAI client; HF token as the API key)

The exposed port is at https://<job_id>--10000.hf.jobs; the OpenAI base URL is that plus /v1.

import base64, os
from openai import OpenAI

client = OpenAI(base_url="https://<job_id>--10000.hf.jobs/v1", api_key=os.environ["HF_TOKEN"])
img = base64.b64encode(open("page.jpg", "rb").read()).decode()

r = client.chat.completions.create(
    model="Unlimited-OCR",
    messages=[{"role": "user", "content": [
        {"type": "text", "text": "document parsing."},
        {"type": "image_url", "image_url": {"url": f"data:image/jpeg;base64,{img}"}},
    ]}],
    temperature=0,
    extra_body={"images_config": {"image_mode": "gundam"}},  # "gundam" (crop-tiling) or "base"
)
print(r.choices[0].message.content)

Output is layout-grounded markdown: each block is tagged <|det|>type [x1,y1,x2,y2]<|/det|> text, with coordinates normalized to 0–1000. Remove the tags for plain text (re.sub(r'<\|det\|>.*?<\|/det\|>', '', text)) or keep them for structure.

3. Multi-page / PDF (SGLang shown; vLLM also works on clean docs)

✅ This SGLang flow (Option B) is validated working 2026-06-28 (a clean 2-page doc read back both pages verbatim, <PAGE>-separated) and follows the model card's multi-page example. The images_config/image_mode param is SGLang-specific — vLLM ignores it; on vLLM, do multi-page with one <image> per page in the text + window_size=1024 in vllm_xargs (no images_config). Both engines read clean multi-page docs; SGLang was the more robust on hard/degraded scans, where vLLM multi-page hallucinated in our tests. (vLLM's upstream PR #46564 benchmarks single-page only.)

Send multiple page images in one request with the Multi page parsing. prompt and image_mode="base":

parts = [{"type": "text", "text": "Multi page parsing."}]
for page_png in page_images:            # e.g. PDF pages rendered with pymupdf at ~150 dpi
    b64 = base64.b64encode(open(page_png, "rb").read()).decode()
    parts.append({"type": "image_url", "image_url": {"url": f"data:image/png;base64,{b64}"}})

r = client.chat.completions.create(
    model="Unlimited-OCR",
    messages=[{"role": "user", "content": parts}],
    temperature=0, max_tokens=16384,
    extra_body={"images_config": {"image_mode": "base"}},
)

Pages are separated by <PAGE>; tables are returned as HTML and equations as LaTeX, with reading order preserved across pages. The context length is 32k tokens, so split longer documents.

4. Concurrency

SGLang batches concurrent requests, so a client can send many requests in parallel to one endpoint; the upstream infer.py uses a ThreadPoolExecutor at concurrency=8. For a large corpus, a batch job that runs next to the data (resumable, no network transfer) is usually a better fit than a client-to-endpoint loop.

5. Stop it

hf jobs cancel <job_id>

Billing is per-minute for the GPU flavor plus a small flat fee for the exposed port; scheduling time is not billed. Run hf jobs hardware for current flavors and prices.