Sglang Agent Skill

Fast structured generation and serving for LLMs with RadixAttention prefix caching. Use for JSON/regex outputs, constrained decoding, agentic workflows with tool calls, or when you need 5× faster inference than vLLM with prefix sharing. Powers 300,000+ GPUs at xAI, AMD, NVIDIA, and LinkedIn.

11k tokens

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the whole folder, loaded on every use

files

instructions only

copies elsewhere

how many repositories repackaged it

11362

stars on the repo

on the repository, not the skill itself

Install

one command, takes just this skill from the repository

npx skills add https://github.com/Orchestra-Research/AI-Research-SKILLs --skill sglang

The instruction itself

26 sections, as written by the author

SGLang

High-performance serving framework for LLMs and VLMs with RadixAttention for automatic prefix caching.

When to use SGLang

Use SGLang when:

Need structured outputs (JSON, regex, grammar)
Building agents with repeated prefixes (system prompts, tools)
Agentic workflows with function calling
Multi-turn conversations with shared context
Need faster JSON decoding (3× vs standard)

Use vLLM instead when:

Simple text generation without structure
Don't need prefix caching
Want mature, widely-tested production system

Use TensorRT-LLM instead when:

Maximum single-request latency (no batching needed)
NVIDIA-only deployment
Need FP8/INT4 quantization on H100

Quick start

Installation

# pip install (recommended)
pip install "sglang[all]"

# With FlashInfer (faster, CUDA 11.8/12.1)
pip install sglang[all] flashinfer -i https://flashinfer.ai/whl/cu121/torch2.4/

# From source
git clone https://github.com/sgl-project/sglang.git
cd sglang
pip install -e "python[all]"

Launch server

# Basic server (Llama 3-8B)
python -m sglang.launch_server \
    --model-path meta-llama/Meta-Llama-3-8B-Instruct \
    --port 30000

# With RadixAttention (automatic prefix caching)
python -m sglang.launch_server \
    --model-path meta-llama/Meta-Llama-3-8B-Instruct \
    --port 30000 \
    --enable-radix-cache  # Default: enabled

# Multi-GPU (tensor parallelism)
python -m sglang.launch_server \
    --model-path meta-llama/Meta-Llama-3-70B-Instruct \
    --tp 4 \
    --port 30000

Basic inference

import sglang as sgl

# Set backend
sgl.set_default_backend(sgl.OpenAI("http://localhost:30000/v1"))

# Simple generation
@sgl.function
def simple_gen(s, question):
    s += "Q: " + question + "\n"
    s += "A:" + sgl.gen("answer", max_tokens=100)

# Run
state = simple_gen.run(question="What is the capital of France?")
print(state["answer"])
# Output: "The capital of France is Paris."

Structured JSON output

import sglang as sgl

@sgl.function
def extract_person(s, text):
    s += f"Extract person information from: {text}\n"
    s += "Output JSON:\n"

    # Constrained JSON generation
    s += sgl.gen(
        "json_output",
        max_tokens=200,
        regex=r'\{"name": "[^"]+", "age": \d+, "occupation": "[^"]+"\}'
    )

# Run
state = extract_person.run(
    text="John Smith is a 35-year-old software engineer."
)
print(state["json_output"])
# Output: {"name": "John Smith", "age": 35, "occupation": "software engineer"}

RadixAttention (Key Innovation)

What it does: Automatically caches and reuses common prefixes across requests.

Performance:

5× faster for agentic workloads with shared system prompts
10× faster for few-shot prompting with repeated examples
Zero configuration - works automatically

How it works:

Builds radix tree of all processed tokens
Automatically detects shared prefixes
Reuses KV cache for matching prefixes
Only computes new tokens

Example (Agent with system prompt):

Request 1: [SYSTEM_PROMPT] + "What's the weather?"
→ Computes full prompt (1000 tokens)

Request 2: [SAME_SYSTEM_PROMPT] + "Book a flight"
→ Reuses system prompt KV cache (998 tokens)
→ Only computes 2 new tokens
→ 5× faster!

Structured generation patterns

JSON with schema

@sgl.function
def structured_extraction(s, article):
    s += f"Article: {article}\n\n"
    s += "Extract key information as JSON:\n"

    # JSON schema constraint
    schema = {
        "type": "object",
        "properties": {
            "title": {"type": "string"},
            "author": {"type": "string"},
            "summary": {"type": "string"},
            "sentiment": {"type": "string", "enum": ["positive", "negative", "neutral"]}
        },
        "required": ["title", "author", "summary", "sentiment"]
    }

    s += sgl.gen("info", max_tokens=300, json_schema=schema)

state = structured_extraction.run(article="...")
print(state["info"])
# Output: Valid JSON matching schema

Regex-constrained generation

@sgl.function
def extract_email(s, text):
    s += f"Extract email from: {text}\n"
    s += "Email: "

    # Email regex pattern
    s += sgl.gen(
        "email",
        max_tokens=50,
        regex=r'[a-zA-Z0-9._%+-]+@[a-zA-Z0-9.-]+\.[a-zA-Z]{2,}'
    )

state = extract_email.run(text="Contact [email protected] for details")
print(state["email"])
# Output: "[email protected]"

Grammar-based generation

@sgl.function
def generate_code(s, description):
    s += f"Generate Python code for: {description}\n"
    s += "```python\n"

    # EBNF grammar for Python
    python_grammar = """
    ?start: function_def
    function_def: "def" NAME "(" [parameters] "):" suite
    parameters: parameter ("," parameter)*
    parameter: NAME
    suite: simple_stmt | NEWLINE INDENT stmt+ DEDENT
    """

    s += sgl.gen("code", max_tokens=200, grammar=python_grammar)
    s += "\n```"

Agent workflows with function calling

import sglang as sgl

# Define tools
tools = [
    {
        "name": "get_weather",
        "description": "Get weather for a location",
        "parameters": {
            "type": "object",
            "properties": {
                "location": {"type": "string"}
            }
        }
    },
    {
        "name": "book_flight",
        "description": "Book a flight",
        "parameters": {
            "type": "object",
            "properties": {
                "from": {"type": "string"},
                "to": {"type": "string"},
                "date": {"type": "string"}
            }
        }
    }
]

@sgl.function
def agent_workflow(s, user_query, tools):
    # System prompt (cached with RadixAttention)
    s += "You are a helpful assistant with access to tools.\n"
    s += f"Available tools: {tools}\n\n"

    # User query
    s += f"User: {user_query}\n"
    s += "Assistant: "

    # Generate with function calling
    s += sgl.gen(
        "response",
        max_tokens=200,
        tools=tools,  # SGLang handles tool call format
        stop=["User:", "\n\n"]
    )

# Multiple queries reuse system prompt
state1 = agent_workflow.run(
    user_query="What's the weather in NYC?",
    tools=tools
)
# First call: Computes full system prompt

state2 = agent_workflow.run(
    user_query="Book a flight to LA",
    tools=tools
)
# Second call: Reuses system prompt (5× faster)

Performance benchmarks

RadixAttention speedup

Few-shot prompting (10 examples in prompt):

vLLM: 2.5 sec/request
SGLang: 0.25 sec/request (10× faster)
Throughput: 4× higher

Agent workflows (1000-token system prompt):

vLLM: 1.8 sec/request
SGLang: 0.35 sec/request (5× faster)

JSON decoding:

Standard: 45 tok/s
SGLang: 135 tok/s (3× faster)

Throughput (Llama 3-8B, A100)

|----------|------|--------|---------|

Multi-turn conversations

@sgl.function
def multi_turn_chat(s, history, new_message):
    # System prompt (always cached)
    s += "You are a helpful AI assistant.\n\n"

    # Conversation history (cached as it grows)
    for msg in history:
        s += f"{msg['role']}: {msg['content']}\n"

    # New user message (only new part)
    s += f"User: {new_message}\n"
    s += "Assistant: "
    s += sgl.gen("response", max_tokens=200)

# Turn 1
history = []
state = multi_turn_chat.run(history=history, new_message="Hi there!")
history.append({"role": "User", "content": "Hi there!"})
history.append({"role": "Assistant", "content": state["response"]})

# Turn 2 (reuses Turn 1 KV cache)
state = multi_turn_chat.run(history=history, new_message="What's 2+2?")
# Only computes new message (much faster!)

# Turn 3 (reuses Turn 1 + Turn 2 KV cache)
state = multi_turn_chat.run(history=history, new_message="Tell me a joke")
# Progressively faster as history grows

Advanced features

Speculative decoding

# Launch with draft model (2-3× faster)
python -m sglang.launch_server \
    --model-path meta-llama/Meta-Llama-3-70B-Instruct \
    --speculative-model meta-llama/Meta-Llama-3-8B-Instruct \
    --speculative-num-steps 5

@sgl.function
def describe_image(s, image_path):
    s += sgl.image(image_path)
    s += "Describe this image in detail: "
    s += sgl.gen("description", max_tokens=200)

state = describe_image.run(image_path="photo.jpg")
print(state["description"])

Batching and parallel requests

# Automatic batching (continuous batching)
states = sgl.run_batch(
    [
        simple_gen.bind(question="What is AI?"),
        simple_gen.bind(question="What is ML?"),
        simple_gen.bind(question="What is DL?"),
    ]
)

# All 3 processed in single batch (efficient)

OpenAI-compatible API

# Start server with OpenAI API
python -m sglang.launch_server \
    --model-path meta-llama/Meta-Llama-3-8B-Instruct \
    --port 30000

# Use with OpenAI client
curl http://localhost:30000/v1/chat/completions \
  -H "Content-Type: application/json" \
  -d '{
    "model": "default",
    "messages": [
      {"role": "system", "content": "You are helpful"},
      {"role": "user", "content": "Hello"}
    ],
    "temperature": 0.7,
    "max_tokens": 100
  }'

# Works with OpenAI Python SDK
from openai import OpenAI
client = OpenAI(base_url="http://localhost:30000/v1", api_key="EMPTY")

response = client.chat.completions.create(
    model="default",
    messages=[{"role": "user", "content": "Hello"}]
)

Supported models

Text models:

Llama 2, Llama 3, Llama 3.1, Llama 3.2
Mistral, Mixtral
Qwen, Qwen2, QwQ
DeepSeek-V2, DeepSeek-V3
Gemma, Phi-3

Vision models:

LLaVA, LLaVA-OneVision
Phi-3-Vision
Qwen2-VL

100+ models from HuggingFace

Hardware support

NVIDIA: A100, H100, L4, T4 (CUDA 11.8+)

AMD: MI300, MI250 (ROCm 6.0+)

Intel: Xeon with GPU (coming soon)

Apple: M1/M2/M3 via MPS (experimental)

References

Structured Generation Guide - JSON schemas, regex, grammars, validation
RadixAttention Deep Dive - How it works, optimization, benchmarks
Production Deployment - Multi-GPU, monitoring, autoscaling

Resources

GitHub: https://github.com/sgl-project/sglang
Docs: https://sgl-project.github.io/
Paper: RadixAttention (arXiv:2312.07104)
Discord: https://discord.gg/sglang

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How to use it

Copy the folder

Take orchestra-research/sglang from the repository into ~/.claude/skills for personal use, or into .claude/skills inside a project.

Check the name does not clash

The agent identifies a skill by the name field in its header. Two skills with the same name cannot sit side by side — one of them will be ignored.

Install what it needs

The instructions reference pip. Without those the skill loads but fails at the first command.

Sglang Agent Skill

Install

The instruction itself

SGLang

When to use SGLang

Quick start

Installation

Launch server

Basic inference

Structured JSON output

RadixAttention (Key Innovation)

Structured generation patterns

JSON with schema

Regex-constrained generation

Grammar-based generation

Agent workflows with function calling

Performance benchmarks

RadixAttention speedup

Throughput (Llama 3-8B, A100)

Multi-turn conversations

Advanced features

Speculative decoding

Multi-modal (vision models)

Batching and parallel requests

OpenAI-compatible API

Supported models

Hardware support

References

Resources

Other skills for the same job

How to use it