hygate-c

A small, dependency-light C port of the Hygate gateway that exposes a Gradio-hosted Hunyuan model (hy3) behind an OpenAI-compatible REST API.

It translates OpenAI chat/completions requests into Gradio's queue API (POST /gradio_api/call/chat → GET /gradio_api/call/chat/{event_id} SSE stream) and translates the Gradio stream back into OpenAI streaming and non-streaming responses, including tool calls and reasoning content.

Build

Requires libcurl and json-c (auto-detected via pkg-config); falls back to -lcurl -ljson-c if pkg-config is unavailable.

make            # dynamic binary -> bin/hygate
make static     # static binary  -> bin/hygate.static
make clean

Build is POSIX-portable (Linux, FreeBSD, macOS) and compiles clean with -Wall -Wextra.

Run

./bin/hygate [options]

Options

Flag	Default	Description
-port <n>	8080	Listen port (binds 0.0.0.0).
-endpoint <url>	https://tencent-hy3.hf.space	Upstream Gradio Space base URL (trailing slash trimmed).
-model <name>	hy3	Model name reported in /v1/models and responses.
-user-agent <ua> / -ua <ua>	built-in Firefox UA	Outgoing User-Agent. Empty string => default.
-max-body <bytes>	5242880 (5 MiB)	Maximum request body size. Oversized requests are rejected with 413.
-max-conn <n>	16	Maximum concurrent connections (worker threads). Excess connections queue in the kernel listen backlog.

Flag forms: -key value or -key=value.

Example — listen on 9090, allow 8 MiB bodies, cap at 32 concurrent connections:

./bin/hygate -port 9090 -max-body 8388608 -max-conn 32

Endpoints

Method	Path	Notes
GET	/v1/models, /models	Returns the configured model (served locally, no upstream call).
POST	/v1/chat/completions, /chat/completions	OpenAI-style chat completion. Supports stream, tools/tool_calls, and reasoning_content.
OPTIONS	any of the above	CORS preflight.

CORS is enabled for all origins (Access-Control-Allow-Origin: *).

Request / response notes

• OpenAI messages are mapped into Gradio's [message, system, history, "high", temperature, max_tokens, top_p, null, functions_json] payload.
• max_tokens / max_completion_tokens are honored; defaults to 131072 when omitted.
• Upstream calls use Fibonacci-backoff retries (up to MAX_RETRIES = 5, 300 s timeout).

Token usage counting

Responses include an OpenAI-style usage object with prompt_tokens, completion_tokens, total_tokens, and completion_tokens_details (reasoning_tokens). These are computed locally by an embedded cl100k_base BPE tokenizer (vocabulary data in tokenizer_data.c, logic in tokenizer.c) — no upstream token counts are available from the Gradio backend.

• prompt_tokens sums the active system prompt, each message's content (or individual multi-part content parts), reasoning_content, tool_calls / function_call (name and arguments), tool result wrappers, and any request tools function definitions (name, description, parameters).
• completion_tokens sums the assistant content, reasoning_content, and any emitted tool_calls (name and arguments), with reasoning_tokens broken out under completion_tokens_details.
• total_tokens = prompt_tokens + completion_tokens.

cl100k_base is OpenAI's canonical multilingual tokenizer and is used as the best available approximation for Hunyuan; the resulting counts are deterministic subword counts and may differ slightly from the exact Hunyuan vocabulary. No per-message formatting overhead (the +3/priming tokens OpenAI applies) is added.

Security considerations

• The server binds all interfaces (0.0.0.0) and currently enforces no authentication — it is an open relay to the configured upstream. Do not expose it to untrusted networks without a fronting proxy or auth layer.
• -max-body and -max-conn exist to bound resource usage (memory and thread count) against abusive clients.

Source layout

File	Role
main.c	Entry point, flag parsing, TCP listen, thread-per-connection with concurrency cap.
server.c	HTTP parsing, routing, SSE emitters, libcurl upstream calls, streaming state machine.
jsonapi.c	OpenAI <-> Gradio payload translation and stream parsing.
util.c	Growable string buffer (strbuf), UUID, backoff, helpers.
hygate.h	Shared types and declarations.

Credits

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