# gr2gw: universal Gradio to OpenAI LLM gateway

A zero-dependency, high-performance Go proxy server that introspects any Gradio chat space (such as Hugging Face Spaces or custom deployments) and exposes a standards-compliant OpenAI `/v1/chat/completions` and `/v1/models` HTTP API.

Default demo space: `https://tencent-hy3.hf.space`

## Features

- **Zero external dependencies**: pure Go standard library (`net/http`, `encoding/json`, `bufio`, etc.).
- **Universal heuristic discovery engine**:
  - Automatically interrogates `/gradio_api/info`, `/config`, and Hugging Face metadata without endpoint-specific hardcoding.
  - Detects Gradio runtime versions across v3, v4, v5, and v6.
  - Classifies application architecture into `ChatInterface`, `Blocks (Chat)`, `Blocks (Multimodal Chat)`, `Interface`, and `Generic`.
  - Disambiguation scoring engine evaluates candidate endpoints, filtering out UI resets, clears, retries, likes, and utility triggers to pinpoint primary conversational completion functions.
  - Correlates semantic parameter names from `/gradio_api/info` with component IDs from `/config` to reconstruct parameter mappings even when component labels are obfuscated.
- **Dual protocol support with auto-fallback**:
  - Supports modern Gradio 4/5/6 `/call` SSE protocol with persistent session hashes.
  - Supports legacy Gradio 3 `/run/predict` and `/api/predict` direct execution protocol.
  - Instant zero-latency fallback from `/call` to `/run/predict` upon HTTP 404 or 405 status codes.
- **Tool calling support classification**:
  - Automatically identifies tool calling mechanisms: `native_slot`, `prompt_augmented_system`, `prompt_augmented_first_turn`, or `prompt_augmented_single_prompt`.
  - Upstream tool call recovery intercepts `tool_use_failed` errors and extracts function names and JSON arguments.
  - Real-time sliding-window `<tool_call>` tag interceptor emits structured OpenAI tool call chunks.
- **Native Tencent Hunyuan 3 (`tencent-hy3`) support**:
  - Full native zero-degradation handling for official spaces like `https://tencent-hy3.hf.space`.
  - Maps `functions_json_str` natively without polluting the system prompt.
  - Preserves multi-turn reasoning content and tool call history in standard OpenAI message schemas.
  - Maps `reasoning_effort` (`no_think`, `low`, `high`) directly to `think_level`.
- **Universal multi-turn handling**:
  - Automatically formats conversation history into structured inputs when the space supports them.
  - Transparently composes multi-turn dialogue (`System`, `User`, `Assistant`) into single prompt inputs when the space only accepts a single message textbox.
  - Automatically pads hidden/State inputs (e.g. Gradio State components) to prevent backend argument count mismatches.
  - Automatically handles multimodal textbox inputs (`MultimodalData` with `{text, files}`) and space component defaults (radios, sliders, checkboxes).
- **Real-time streaming & accumulation filter**:
  - Automatically computes token deltas from cumulative or incremental Gradio SSE output streams (including 2D Hy3 frames `[[content, reasoning, tool_calls, history]]`).
  - Emits standards-compliant `chat.completion.chunk` SSE events in real time.
- **Thinking & reasoning token separation**:
  - Streams native reasoning chunks as `delta.reasoning_content` in real time.
  - Detects `<think>...</think>` tags in real time as fallback for standard spaces.
  - Separates reasoning into `delta.reasoning_content` (streaming) and `message.reasoning_content` (non-streaming).
  - Keeps `content` clean without tag leakage.
- **Built-in SOCKS5 proxy client**:
  - Full RFC 1928 / RFC 1929 implementation with domain resolution (`socks5h://`), IPv4, IPv6, and username/password auth.
- **Dynamic space override**:
  - Switch the target Gradio space on-the-fly per request using the `X-Gradio-Space` or `X-Space-URL` HTTP headers.
- **Fibonacci retry engine**:
  - Resilient backoff retry mechanism (1s, 1s, 2s, 3s, 5s) for transient network hiccups with immediate break on 404/405 errors.

## Heuristic discovery engine

The gateway implements an autonomous heuristic engine that discovers and configures the optimal completion path for any target Gradio space at startup.

### Space introspection and version detection

Upon initialization, `gr2gw` inspects the space metadata:
1. Queries `/gradio_api/info` and `/config` endpoints.
2. Extracts the Gradio runtime version (v3, v4, v5, or v6).
3. Detects API routing prefixes (e.g. `/gradio_api` on modern versions, or root on Gradio 3).

### UI flavor classification

The engine classifies the application structure into architectural flavors:
- **`ChatInterface`**: Standard Gradio chat interfaces equipped with chatbot, textbox, and optional additional inputs.
- **`Blocks (Chat)`**: Custom `gr.Blocks` layouts containing conversational components.
- **`Blocks (Multimodal Chat)`**: Blocks architectures featuring `MultimodalTextbox` components that accept `{text, files}` JSON payloads.
- **`Interface`**: Classic input-output `gr.Interface` instances.
- **`Generic`**: Spaces with custom or unclassified component topologies.

### Candidate endpoint scoring

Gradio spaces frequently expose dozens of internal endpoints for UI actions (e.g. clearing text, retrying responses, voting/liking, adjusting sliders). The scoring algorithm identifies the true conversational endpoint by:
- Penalizing non-conversational triggers (e.g. `-600` for clear/reset/undo/retry/like endpoints).
- Rewarding chat semantics (`+150` for `/chat`, `/predict`, `/generate`, `/respond`).
- Rewarding message inputs (`+120` for `Textbox` or `MultimodalTextbox`).
- Rewarding chat history slots (`+80` for `Chatbot` or `State` components).
- Rewarding generator and streaming dependencies (`+50`).

### Dual protocol execution and auto-fallback

- **`call` protocol**: Modern Gradio 4/5/6 execution via `POST /call/{endpoint}` returning an event ID, followed by `GET /call/{endpoint}/{event_id}` SSE streaming.
- **`predict` protocol**: Gradio 3 and legacy execution via direct `POST /run/predict` or `POST /api/predict`.
- **Runtime failover**: If a space returns HTTP 404 or 405 when calling the modern protocol, the gateway breaks immediately from the retry loop and falls back to `/run/predict`.

### Tool calling support modes

The gateway evaluates available input components to determine how tool schemas and function calls should be delivered:
- **`native_slot`**: The space provides a dedicated parameter slot for tool definitions (e.g. `functions_json_str` on Hunyuan 3). Function definitions are passed cleanly without prompt alteration.
- **`prompt_augmented_system`**: The space provides a separate `system_prompt` input slot. Tool definitions and invocation schemas are injected directly into the system prompt.
- **`prompt_augmented_first_turn`**: The space accepts chat history pairs but lacks a dedicated system prompt slot. Tool definitions are prepended to the user prompt on the first dialogue turn.
- **`prompt_augmented_single_prompt`**: The space accepts only a single textbox input. Full multi-turn dialogue, tool definitions, and system guidance are synthesized into a single cohesive prompt.

### Startup resolution diagnostics

Whenever the gateway starts or inspects a new space, it prints the complete resolution picture:

```text
================================================================================
Gradio Space Resolution Picture
--------------------------------------------------------------------------------
Space URL:         https://tencent-hy3.hf.space
Title:             Hunyuan 3 Chat
Gradio Version:    5.29.0
UI Flavor:         Blocks (Chat)
Protocol:          call
API Prefix:        /gradio_api
Resolved Endpoint: /chat_fn
Function Index:    1
Primary Model:     hy3
Exposed Models:    hy3, hunyuan3, tencent/Hy3
History Format:    tuples
Tool Call Support: native_slot
Total Input Slots: 9
Input Slot Mappings:
  [0] Component ID 1    textbox (label="message")      -> message
  [1] Component ID 2    textbox (label="system")       -> system_prompt
  [2] Component ID 3    chatbot (label="chatbot")      -> history
  [3] Component ID 4    radio (label="think_level")    -> think_level
  [4] Component ID 5    slider (label="temperature")   -> temperature
  [5] Component ID 6    slider (label="max_tokens")    -> max_tokens
  [6] Component ID 7    slider (label="top_p")         -> top_p
  [7] Component ID 8    state (label="preserved")      -> preserved_thinking
  [8] Component ID 9    textbox (label="functions")    -> functions_json_str
================================================================================
```

### Gateway status endpoint

Making a `GET` request to `/` returns a JSON summary of the running gateway and the discovered space profile:

```bash
curl http://localhost:8080/
```

Response:
```json
{
  "name": "gr2gw",
  "status": "ready",
  "space_url": "https://tencent-hy3.hf.space",
  "gradio_version": "5.29.0",
  "flavor": "Blocks (Chat)",
  "protocol": "call",
  "tool_call_mode": "native_slot",
  "models": ["hy3", "hunyuan3", "tencent/Hy3"]
}
```

## Installation

```bash
go install code.luxferre.top/luxferre/gr2gw@latest
```

## Build

```bash
make build
```

Binary will be compiled to `bin/gr2gw`.

To run tests:
```bash
make test
```

## Usage

### Quick start

Run with the default space (`https://tencent-hy3.hf.space`):
```bash
./bin/gr2gw -port 8080
```

Target any other Gradio space:
```bash
./bin/gr2gw -space https://lucasmarchettidelima-digital-twin.hf.space -port 8080
```

With SOCKS5 proxy:
```bash
./bin/gr2gw -space https://tencent-hy3.hf.space -socks socks5://127.0.0.1:1080
```

### CLI flags

| Flag | Default | Description |
|------|---------|-------------|
| `-space`, `-url`, `-endpoint` | `https://tencent-hy3.hf.space` | Target Gradio space URL |
| `-model` | `""` | Exposed model name override (default: auto-detected) |
| `-port` | `8080` | Port to listen on |
| `-host` | `0.0.0.0` | Host interface to bind to |
| `-socks`, `-proxy`, `-socks5` | `""` | SOCKS5 proxy URL (`socks5://user:pass@host:port`) |
| `-user-agent`, `-ua` | Firefox string | Custom User-Agent header |
| `-timeout` | `300` | Upstream request timeout in seconds |

### Environment variables

- `GRADIO_SPACE_URL`: default Gradio space URL fallback.
- `ALL_PROXY`, `SOCKS5_PROXY`, `SOCKS_PROXY`: default SOCKS5 proxy URL fallback.

## API examples

### List models

```bash
curl http://localhost:8080/v1/models
```

Response:
```json
{
  "object": "list",
  "data": [
    {
      "id": "hy3",
      "object": "model",
      "created": 1788756307,
      "owned_by": "gradio"
    },
    {
      "id": "hunyuan3",
      "object": "model",
      "created": 1788756307,
      "owned_by": "gradio"
    },
    {
      "id": "tencent/Hy3",
      "object": "model",
      "created": 1788756307,
      "owned_by": "gradio"
    }
  ]
}
```

### Chat completions (non-streaming)

```bash
curl http://localhost:8080/v1/chat/completions \
  -H "Content-Type: application/json" \
  -d '{
    "model": "hy3",
    "messages": [
      {"role": "user", "content": "What is the capital of France?"}
    ]
  }'
```

Response:
```json
{
  "id": "chatcmpl-16425f9d-c350-47a1-9a6d-e9ce10871545",
  "object": "chat.completion",
  "created": 1788756310,
  "model": "hy3",
  "choices": [
    {
      "index": 0,
      "message": {
        "role": "assistant",
        "content": "The capital of France is Paris."
      },
      "finish_reason": "stop"
    }
  ],
  "usage": {
    "prompt_tokens": 0,
    "completion_tokens": 0,
    "total_tokens": 0
  }
}
```

### Chat completions (streaming)

```bash
curl -N http://localhost:8080/v1/chat/completions \
  -H "Content-Type: application/json" \
  -d '{
    "model": "hy3",
    "messages": [
      {"role": "user", "content": "Count from 1 to 5."}
    ],
    "stream": true
  }'
```

### Tool calling (turn 1)

```bash
curl http://localhost:8080/v1/chat/completions \
  -H "Content-Type: application/json" \
  -d '{
    "model": "hy3",
    "messages": [
      {"role": "user", "content": "What is the weather in Tokyo?"}
    ],
    "tools": [{
      "type": "function",
      "function": {
        "name": "get_weather",
        "description": "Get current weather in a location",
        "parameters": {
          "type": "object",
          "properties": {
            "location": {"type": "string", "description": "City name"}
          },
          "required": ["location"]
        }
      }
    }]
  }'
```

Response:
```json
{
  "id": "chatcmpl-32727c62-ef2a-4866-855b-f1c7ec2b8023",
  "object": "chat.completion",
  "created": 1788756322,
  "model": "hy3",
  "choices": [
    {
      "index": 0,
      "message": {
        "role": "assistant",
        "content": null,
        "tool_calls": [
          {
            "id": "call_3d4c016a",
            "type": "function",
            "function": {
              "name": "get_weather",
              "arguments": "{\"location\":\"Tokyo\"}"
            }
          }
        ]
      },
      "finish_reason": "tool_calls"
    }
  ],
  "usage": {
    "prompt_tokens": 0,
    "completion_tokens": 0,
    "total_tokens": 0
  }
}
```

### Tool response submission (turn 2)

```bash
curl http://localhost:8080/v1/chat/completions \
  -H "Content-Type: application/json" \
  -d '{
    "model": "hy3",
    "messages": [
      {"role": "user", "content": "What is the weather in Tokyo?"},
      {
        "role": "assistant",
        "tool_calls": [
          {
            "id": "call_3d4c016a",
            "type": "function",
            "function": {
              "name": "get_weather",
              "arguments": "{\"location\":\"Tokyo\"}"
            }
          }
        ]
      },
      {
        "role": "tool",
        "tool_call_id": "call_3d4c016a",
        "content": "{\"temperature\": 20, \"condition\": \"sunny\"}"
      }
    ],
    "tools": [{
      "type": "function",
      "function": {
        "name": "get_weather",
        "description": "Get current weather in a location",
        "parameters": {
          "type": "object",
          "properties": {
            "location": {"type": "string", "description": "City name"}
          },
          "required": ["location"]
        }
      }
    }]
  }'
```

Response:
```json
{
  "id": "chatcmpl-4903ba12-f12b-4cd3-a801-7290bc91a421",
  "object": "chat.completion",
  "created": 1788756335,
  "model": "hy3",
  "choices": [
    {
      "index": 0,
      "message": {
        "role": "assistant",
        "content": "The current weather in Tokyo is sunny with a temperature of 20 °C."
      },
      "finish_reason": "stop"
    }
  ],
  "usage": {
    "prompt_tokens": 0,
    "completion_tokens": 0,
    "total_tokens": 0
  }
}
```

### Dynamic target space override

Override the target space per request without restarting the server:

```bash
curl http://localhost:8080/v1/chat/completions \
  -H "Content-Type: application/json" \
  -H "X-Gradio-Space: https://ericsqin-hy3.hf.space" \
  -d '{
    "messages": [
      {"role": "user", "content": "Hello!"}
    ]
  }'
```

## Credits

Created by Luxferre in 2026, released into the public domain with no warranties.