pfm-ocr/backend/AGENTS.md

# AGENTS: PaddleOCR-VL-1.6 vLLM Service

This repository serves **PaddleOCR-VL-1.6** as a dedicated VLM inference backend using **vLLM**. All Python workflows use **uv** (never bare `pip` or system Python).

## Architecture

```
Client (PaddleOCR pipeline)  -->  HTTP /v1  -->  paddleocr genai_server (vLLM backend)
```

This service exposes only the VLM stage. Clients connect with `vl_rec_backend="vllm-server"` and `vl_rec_server_url="http://<host>:8118/v1"`.

## Prerequisites

- Linux with NVIDIA GPU (CC >= 8.0 recommended; CUDA 12.6+ driver support)
- [uv](https://docs.astral.sh/uv/) installed (`uv --version`)
- ~16 GB GPU VRAM for default settings (tune via `config/vllm_config.yaml`)

## Quick start

```bash
cd <YOUR-WORKING-DIR>/ai-ocr-pfm-2026

# 1) Create Python 3.12 venv and install dependencies
./scripts/install.sh

# 2) Start the vLLM-backed genai server
./scripts/serve.sh
```

Default endpoint: `http://0.0.0.0:8118/v1`

## uv conventions (always follow)

| Task | Command |
|------|---------|
| Create/sync env | `uv sync` |
| Run any Python | `uv run <command>` |
| Add a package | `uv add <package>` |
| Run server | `./scripts/serve.sh` or `uv run paddleocr genai_server ...` |

Never use `python -m pip`, `pip install`, or `python -m venv` directly in this repo.

## Issue recording (always follow)

**Every problem encountered** during install, serve, debug, or client integration must be written to `issues/` before moving on — even if it was resolved in the same session.

### Naming

```
issues/{NN}-{slug}.md
```

| Part | Rule | Example |
|------|------|---------|
| `{NN}` | Two-digit running number (`01`, `02`, …). Increment from the highest existing file. | `03` |
| `{slug}` | Lowercase kebab-case summary of the problem | `gpu-memory-startup-failure` |

Full example: `issues/04-gpu-memory-startup-failure.md`

### When to create a file

- Install or dependency errors (flash-attn, vLLM, uv conflicts)
- Server startup or runtime failures (OOM, port bind, model load)
- Client integration bugs or misconfiguration
- Workarounds that took non-obvious steps to discover

Do **not** rely on chat history or inline comments alone — if it blocked progress, it belongs in `issues/`.

### File template

```markdown
# Issue {NN}: {Short title}

## Problem
What failed, with exact error message or symptom.

## Context
Environment, command run, relevant config (`.env`, `config/vllm_config.yaml`).

## Solution
What fixed it, or current workaround / open status.

## References
Links, related issue files, or AGENTS.md sections.
```

### Index

Check `issues/` for the next number:

```bash
ls issues/*.md 2>/dev/null | sort
```

See [issues/](issues/) for recorded problems and fixes from this project.

## Environment variables

Copy `.env.example` to `.env` and adjust as needed:

| Variable | Default | Description |
|----------|---------|-------------|
| `GENAI_HOST` | `0.0.0.0` | Bind address |
| `GENAI_PORT` | `8118` | Service port |
| `GENAI_MODEL` | `PaddleOCR-VL-1.6-0.9B` | Model name for `genai_server` |
| `GENAI_BACKEND` | `vllm` | Inference backend |
| `VLLM_CONFIG` | `config/vllm_config.yaml` | vLLM backend YAML config |
| `CUDA_VISIBLE_DEVICES` | `1` (see `.env.example`) | GPU index(es) to use |

On dual-GPU hosts, pick the GPU with more free VRAM. If startup fails with a memory error, lower `gpu-memory-utilization` in `config/vllm_config.yaml`.

## Client usage

After the server is running:

```bash
# CLI
uv run paddleocr doc_parser \
  --input https://paddle-model-ecology.bj.bcebos.com/paddlex/imgs/demo_image/paddleocr_vl_demo.png \
  --vl_rec_backend vllm-server \
  --vl_rec_server_url http://localhost:8118/v1
```

```python
from paddleocr import PaddleOCRVL

pipeline = PaddleOCRVL(
    vl_rec_backend="vllm-server",
    vl_rec_server_url="http://127.0.0.1:8118/v1",
)
output = pipeline.predict("path/to/image.png")
```

Note: The full PaddleOCR-VL client should run in a **separate** environment if it needs PaddlePaddle GPU + Transformers. This repo is the isolated vLLM server only.

## Tuning vLLM

Edit `config/vllm_config.yaml`:

```yaml
gpu-memory-utilization: 0.8
max-num-seqs: 128
```

Reference: [PaddleOCR-VL vLLM parameter tuning](https://www.paddleocr.ai/latest/en/version3.x/pipeline_usage/PaddleOCR-VL.html#331-server-side-parameter-adjustment)

## Troubleshooting

See `issues/` for full write-ups. Quick pointers:

| Symptom | Issue file |
|---------|------------|
| `paddleocr install_genai_server_deps` / `No module named pip` | [01-genai-server-deps-pip-in-uv-venv.md](issues/01-genai-server-deps-pip-in-uv-venv.md) |
| flash-attn wheel incompatible with Python version | [02-flash-attn-wheel-python-version-mismatch.md](issues/02-flash-attn-wheel-python-version-mismatch.md) |
| `uv pip` targets wrong venv from another project | [03-active-virtual-env-from-other-project.md](issues/03-active-virtual-env-from-other-project.md) |
| Free memory below `gpu-memory-utilization` on startup | [04-gpu-memory-startup-failure.md](issues/04-gpu-memory-startup-failure.md) |
| `TokenizersBackend has no attribute all_special_tokens_extended` | [05-transformers-tokenizers-incompatibility.md](issues/05-transformers-tokenizers-incompatibility.md) |
| Extracted images not shown in Gradio demo (raw base64 in markdown) | [06-extracted-images-raw-base64-not-displayed.md](issues/06-extracted-images-raw-base64-not-displayed.md) |

### flash-attn build failures

Install the prebuilt wheel after `uv sync` (see `scripts/install.sh`):

```bash
FLASH_ATTN_WHEEL="https://github.com/mjun0812/flash-attention-prebuild-wheels/releases/download/v0.3.14/flash_attn-2.8.2+cu128torch2.8-cp312-cp312-linux_x86_64.whl" \
  ./scripts/install.sh
```

Pick the wheel matching your Python and CUDA versions from [flash-attention prebuild wheels](https://mjunya.com/flash-attention-prebuild-wheels/). Details: [02-flash-attn-wheel-python-version-mismatch.md](issues/02-flash-attn-wheel-python-version-mismatch.md).

Note: `paddleocr install_genai_server_deps` uses `pip` internally and is incompatible with uv-managed venvs. See [01-genai-server-deps-pip-in-uv-venv.md](issues/01-genai-server-deps-pip-in-uv-venv.md). This repo installs the vLLM stack via `uv sync` + `uv pip`.

### `TokenizersBackend has no attribute all_special_tokens_extended`

Pin transformers (already in `pyproject.toml`):

```bash
uv pip install "transformers==4.57.6"
```

See [05-transformers-tokenizers-incompatibility.md](issues/05-transformers-tokenizers-incompatibility.md).

### Do not install `paddlepaddle-gpu` in this venv

vLLM and PaddlePaddle GPU conflict. This server env uses `paddleocr[doc-parser]` without Paddle GPU.

### GPU memory on startup

If vLLM reports free memory below `gpu-memory-utilization`, either:

- Set `CUDA_VISIBLE_DEVICES` to a less-busy GPU
- Lower `gpu-memory-utilization` in `config/vllm_config.yaml` (e.g. `0.75` or `0.7`)

See [04-gpu-memory-startup-failure.md](issues/04-gpu-memory-startup-failure.md).

### Health check

```bash
curl -s http://localhost:8118/v1/models | jq .
```

## File map

| Path | Purpose |
|------|---------|
| `issues/` | Recorded problems and fixes (`{NN}-{slug}.md`) |
| `pyproject.toml` | uv project metadata and base dependencies |
| `scripts/install.sh` | Bootstrap venv + vLLM server deps |
| `scripts/serve.sh` | Start `paddleocr genai_server` |
| `config/vllm_config.yaml` | vLLM backend tuning |
| `.env.example` | Environment variable template |

## References

- [PaddleOCR-VL usage tutorial](https://www.paddleocr.ai/latest/en/version3.x/pipeline_usage/PaddleOCR-VL.html)
- [PaddleOCR genai_server FAQ](https://github.com/PaddlePaddle/PaddleOCR/discussions/16822)

## Coding Guidelines (always follow)

We use the [karpathy-guidelines](file:///home/user/LABS/OCR/paddle-ocr-vl-1-6-using-vllm-2026/andrej-karpathy-skills/skills/karpathy-guidelines/SKILL.md) skill to reduce common LLM coding mistakes. Refer to [SKILL.md](file:///home/user/LABS/OCR/paddle-ocr-vl-1-6-using-vllm-2026/andrej-karpathy-skills/skills/karpathy-guidelines/SKILL.md) for details:
1. **Think Before Coding**: Explicitly state assumptions and surface tradeoffs instead of making silent choices.
2. **Simplicity First**: Write the minimum amount of code to solve the problem with zero speculative configurations.
3. **Surgical Changes**: Edit only what is required and match the existing coding style exactly.
4. **Goal-Driven Execution**: Define verifiable success criteria and run automated tests/screenshots to confirm correctness.

## Path Guidelines (always follow)

Never use full paths containing the user's logged-in name (e.g., `/home/{uid}/path`). Always use relative paths instead (e.g., `.` or `./path` relative to the workspace root).

## App Testing Guidelines (always follow)

When the user intentionally asks to test the app:
- Use browser tools to test the app.
- Take a screenshot for each sample image, each step, and each variant/option (if any), until the OCR result appears.
- Save the screenshots in the `/screenshots/` folder.
- Follow the file naming convention: `{2-digit-number}-{step#}-{variant_or_options_if_any}-{slug}.jpg` (e.g., `01-step1-default-upload.jpg`).