SimpleLLMFunc 0.8.1

A lightweight yet complete LLM/Agent application development framework. Provides decorators that use function docstrings as prompts, requiring no function body implementation while allowing you to benefit from function definitions and type annotations for higher development efficiency. Seamlessly integrate LLM capabilities into any Python project with minimal code.

LLM as Function, Prompt as Code, Context-Centric

Chinese README

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Update Notes (0.8.1)

Architecture cleanup release: the public APIs stay stable, while PyRepl, SelfRef, and llm_chat internals have been split into smaller facade/component modules. PyRepl is now a thin facade over worker lifecycle, primitive host, execution, audit, tools, and input bridge components. SelfRef now separates durable store, active turn state, mutation queues, context memory, fork management, and agent binding. The full test suite passes with these refactors. See CHANGELOG for details.

Documentation

Chinese Docs | English Docs

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Design Philosophy

Principle	Meaning
LLM is Function	An LLM call is indistinguishable from a Python function call: signature, type hints, return value
Prompt as Code	DocString is the system prompt. Code and prompt are never separated
Context-Centric	Each LLM request is compiled from invocation config, transcript/history, and internal runtime patches

Quick Start

Installation

pip install SimpleLLMFunc

Build a General Agent in 30 Lines

That's it — a coding agent with persistent REPL, file tools, self-reflection memory, context compaction, and parallel fork:

from SimpleLLMFunc import llm_chat, OpenAICompatible, tui
from SimpleLLMFunc.builtin import PyRepl, FileToolset

llm = OpenAICompatible.load_from_json_file("provider.json")["openrouter"]["gpt-5.4"]
repl = PyRepl()
file_tools = FileToolset("./sandbox").toolset

@tui
@llm_chat(
    llm_interface=llm,
    toolkit=[*repl.toolset, *file_tools],
    stream=True,
    self_reference_key="agent_main",
)
async def agent(message: str, history=None):
    """You are a practical local coding agent.

    ## Rules
    - Read files before editing. Prefer small, local edits.
    - Use execute_code for Python. Use file tools for read/grep/sed.
    - When a milestone is done, compact your context via:
      runtime.selfref.context.compact(...)
    - For parallel subtasks, spawn forks via:
      runtime.selfref.fork.spawn(...)
      then gather with runtime.selfref.fork.gather_all(...)
    """

if __name__ == "__main__":
    agent()  # launches an interactive TUI

Run it:

python agent.py

The agent gets a terminal UI with streaming markdown, tool-call panels, and fork lifecycle visualization — no extra code needed.

See examples/tui_general_agent_example.py for the full production version with environment blocks, workspace config, and debug logging.

A Simpler Start — LLM as a Typed Function

If you just need an LLM-powered function with type-safe returns:

import asyncio
from SimpleLLMFunc import llm_function, OpenAICompatible

llm = OpenAICompatible.load_from_json_file("provider.json")["your_provider"]["model"]

@llm_function(llm_interface=llm)
async def classify_sentiment(text: str) -> str:
    """
    Analyze the sentiment of the given text.

    Args:
        text: Text to analyze

    Returns:
        One of: 'positive', 'negative', or 'neutral'
    """
    pass  # Prompt as Code!

async def main():
    result = await classify_sentiment("This product is amazing!")
    print(f"Sentiment: {result}")

asyncio.run(main())

Initial Configuration

1. Copy configuration template:

cp env_template .env

2. Configure API keys in .env. Optionally set LOG_DIR, LANGFUSE_BASE_URL, LANGFUSE_SECRET_KEY, LANGFUSE_PUBLIC_KEY.

3. Check examples/provider_template.json for multi-provider configuration.

Architecture

SimpleLLMFunc is organized in five layers, each with a strict boundary:

┌──────────────────────────────────────────────────────────────────────────┐
│  L1. Decorator Layer          @llm_function / @llm_chat / @tool         │
│      Python call → InvocationSpec + PromptContract + TranscriptSeed     │
├──────────────────────────────────────────────────────────────────────────┤
│  L2. Compile Boundary          compile_pipeline.py (single entry)       │
│      Mutations applied → system prompt assembled → LLM messages rendered│
├──────────────────────────────────────────────────────────────────────────┤
│  L3. ReAct Runtime             react_loop.py (event-only core)          │
│      LLM call → tool batch → mutation collection → loop                 │
├──────────────────────────────────────────────────────────────────────────┤
│  L4. Interface Layer           OpenAICompatible / OpenAIResponsesAPI    │
│      Provider adapters, key pool, token-bucket rate limiting            │
├──────────────────────────────────────────────────────────────────────────┤
│  L5. Infrastructure            hooks / logger / observability / type    │
│      Event stream, Langfuse spans, structured logging, multimodal types │
└──────────────────────────────────────────────────────────────────────────┘

Core Data Flow: Mutation-Driven Context Evolution

The central rule: context changes are applied through compile-time mutation application, not by letting tools or selfref directly rewrite the live context.

     ┌──────────┐   ┌──────────────────────┐
     │ LLM Call │──►│AssistantMessageMutation│
     └──────────┘   └──────────┬───────────┘
     ┌──────────┐   ┌──────────────────────┐│
     │Tool Exec │──►│  ToolResultMutation   ││
     └──────────┘   └──────────┬───────────┘│
     ┌──────────┐   ┌──────────────────────┐│   ┌───────────────┐
     │SelfRef   │──►│ ExperienceRemember /  ││──►│compile_context│──► Compiled Context
     │ Hooks    │   │ ContextSummary        ││   │ apply_mutations│   (LLM-visible)
     └──────────┘   └──────────────────────┘│   └───────────────┘
     ┌──────────┐   ┌──────────────────────┐│
     │Abort     │──►│Truncated / Cancelled  ││
     └──────────┘   └──────────────────────┘│
                                         all mutations

9 mutation types cover every context change: assistant messages, tool results, multimodal outputs, full replacement, compaction, experience remember/forget, truncation, and cancellation.

SelfRef: Meta Context Editing

SelfRef enables an agent to read and edit its own context at runtime, while respecting the mutation boundary:

Operation	What it does	Mutation produced
Remember	Add durable experience that survives across turns	ExperienceRememberMutation
Forget	Remove experience by ID	ExperienceForgetMutation
Compact	Replace working transcript with a structured summary	ContextSummaryMutation
Fork	Spawn a child agent with inherited context snapshot	(sub-agent runs independently)

All changes take effect at the next compile boundary — SelfRef cannot bypass compile to modify live context directly.

Project Map

SimpleLLMFunc/
├── llm_decorator/             # L1: Decorator layer
│   ├── llm_function_decorator.py  # @llm_function — stateless LLM → typed result
│   ├── llm_chat_decorator.py      # @llm_chat public facade / LLMChat callable
│   ├── chat_call_context.py       # Bound args/template/runtime call context
│   ├── chat_selfref.py            # SelfRef binding/finalization helpers
│   ├── chat_toolkit.py            # Runtime toolkit and fork toolkit helpers
│   ├── chat_types.py              # Shared decorator constants/types
│   ├── invocation_spec.py         # InvocationSpec / PromptContract / TranscriptSeed
│   ├── invocation_builder.py      # Spec builders for function/chat modes
│   ├── prompt_contract.py         # Prompt templates + XML Schema generation
│   ├── signature.py               # Signature binding + trace_id + log context
│   └── utils/tools.py             # Tool processing + spec collection
│
├── base/                      # L2+L3: Compile boundary + ReAct runtime
│   ├── compile_pipeline.py        # Single compile entry: reduce + convert
│   ├── context_compile.py         # Mutation apply engine
│   ├── llm_input_render.py        # Ephemeral system prompt rendering
│   ├── react_loop.py              # ReAct main loop (event-only)
│   ├── llm_call.py                # Single LLM call execution
│   ├── tool_scheduler.py          # Concurrent tool scheduling
│   ├── post_process.py            # Response → typed result (XML → Pydantic)
│   ├── types/                     # Core type contracts (all dataclasses)
│   │   ├── source.py              # CompileSource / DataFromAgentConfig / DataFromSelfRef
│   │   ├── context.py             # ContextState / CompiledContext
│   │   ├── compile.py             # ReducedTurnContext / CompiledTurnContext
│   │   ├── mutation.py            # ContextMutation (9 variant union type)
│   │   ├── react.py               # ReactLoopState
│   │   ├── llm.py                 # SingleLLMCallResult
│   │   └── scheduler.py           # ToolSchedulerResult
│   ├── messages/                  # Message building / extraction / validation
│   ├── tool_call/                 # Tool call extraction / execution / streaming / validation
│   └── type_resolve/              # Type description + XML round-trip
│
├── tool/                      # @tool decorator + Tool base class
├── builtin/                   # Built-in tools
│   ├── pyrepl.py                  # PyRepl public facade
│   ├── pyrepl_execution.py        # execute/reset orchestration
│   ├── pyrepl_worker_client.py    # subprocess + queue lifecycle
│   ├── pyrepl_worker_mixin.py     # facade-compatible worker wrappers
│   ├── pyrepl_primitive_host.py   # runtime primitive host / backend bridge
│   ├── pyrepl_tools.py            # execute_code/reset_repl tool factory
│   ├── pyrepl_audit.py            # audit log writer
│   ├── pyrepl_input_bridge.py     # process-wide input bridge
│   ├── pyrepl_input_mixin.py      # PyRepl input submission API
│   └── file_tools.py              # Workspace-scoped file tools
│
├── runtime/                   # Runtime primitive system
│   ├── primitives.py              # PrimitiveRegistry / PrimitivePack / @primitive()
│   ├── worker_proxy.py            # WorkerRuntimeProxy (runtime.selfref.*)
│   └── selfref/
│       ├── state.py               # SelfReference public facade
│       ├── store.py               # Durable history/source store
│       ├── active_turn.py         # Active memory/fork/toolkit/template contextvars
│       ├── mutations.py           # Pending compaction/context mutation queues
│       ├── memory_api.py          # self_reference.memory[...] proxy/handle
│       ├── context_memory.py      # Context memory, experiences, compaction, direct edits
│       ├── agent_binding.py       # Bound recursive agent callable state
│       ├── fork_manager.py        # Fork/spawn/gather lifecycle
│       ├── fork_utils.py          # Fork helper functions/constants
│       ├── session.py             # SelfRefSession (invocation-scoped plugin)
│       ├── context_ops.py         # Context parse / build / canonicalize
│       └── primitives.py          # selfref runtime primitives
│
├── hooks/                     # Event stream system
│   ├── events.py                  # 14 ReActEvent subtypes
│   ├── stream.py                  # ReactOutput / ResponseYield / EventYield
│   ├── event_bus.py               # Event ingress + origin metadata
│   └── event_emitter.py           # Tool custom event emitter
│
├── interface/                 # L4: LLM interface layer
│   ├── llm_interface.py           # Abstract base class
│   ├── openai_compatible.py       # OpenAI Compatible adapter
│   ├── openai_responses_compatible.py  # Responses API adapter
│   ├── key_pool.py                # API key rotation pool
│   └── token_bucket.py            # Token-bucket rate limiting
│
├── logger/                    # Structured logging + trace_id
├── observability/             # Langfuse integration
├── type/                      # Multimodal types (Text / ImgUrl / ImgPath)
└── utils/tui/                 # Textual TUI integration

Detailed Guide

@llm_function — Stateless Typed LLM Calls

Returns Pydantic models, primitives, dicts, or lists directly:

from typing import List
from pydantic import BaseModel, Field

class ProductReview(BaseModel):
    rating: int = Field(..., description="Product rating, 1-5")
    pros: List[str] = Field(..., description="Advantages")
    cons: List[str] = Field(..., description="Disadvantages")
    summary: str = Field(..., description="Review summary")

@llm_function(llm_interface=llm)
async def analyze_review(product_name: str, review_text: str) -> ProductReview:
    """You are a professional product review expert.
    Analyze the review and generate a structured report.

    Args:
        product_name: Product name
        review_text: User review content

    Returns:
        A structured ProductReview object
    """
    pass

result = await analyze_review("XYZ Headphones", "Great sound but unstable connection...")
print(result.rating)   # 4
print(result.pros)     # ["Great sound quality", ...]

@llm_chat — Conversational Agents

Multi-turn history, streaming, tool calls, SelfRef integration:

@llm_chat(llm_interface=llm, toolkit=[search_tool, calculator], stream=True)
async def agent(user_message: str, history=None):
    """An intelligent assistant that can search and calculate."""
    pass

async for response, updated_history in agent("Hello", []):
    print(response)

@tui — Terminal UI for @llm_chat

Out-of-the-box Textual TUI with streaming markdown, tool-call panels, token stats, and fork visualization:

from SimpleLLMFunc import llm_chat, tui

@tui(custom_event_hook=[...])
@llm_chat(llm_interface=llm, stream=True)
async def agent(message: str, history=None):
    """Your agent prompt"""

if __name__ == "__main__":
    agent()  # launches TUI

See examples/tui_chat_example.py for a full example. Each EventYield carries origin metadata for fork-aware event routing.

@tool — Register Functions as LLM Tools

from SimpleLLMFunc.tool import tool
from SimpleLLMFunc.type import ImgPath

@tool(name="generate_chart", description="Generate a chart from data")
async def generate_chart(data: str, chart_type: str = "bar") -> ImgPath:
    """Generate charts based on provided data.

    Args:
        data: CSV format data
        chart_type: Chart type, default is bar chart

    Returns:
        Generated chart file path
    """
    chart_path = "./generated_chart.png"
    # ... chart generation logic
    return ImgPath(chart_path)

Tools can be stacked with @llm_function on the same function.

Multimodal Support

from SimpleLLMFunc.type import ImgPath, ImgUrl, Text

@llm_function(llm_interface=llm)
async def analyze_image(
    description: Text,        # Text description
    web_image: ImgUrl,        # Web image URL
    local_image: ImgPath      # Local image path
) -> str:
    """Analyze images based on the description"""
    pass

result = await analyze_image(
    description=Text("Describe the differences between these images"),
    web_image=ImgUrl("https://example.com/image.jpg"),
    local_image=ImgPath("./reference.jpg")
)

Tool-Call Limit Default

Both @llm_function and @llm_chat default to max_tool_calls=None (unbounded). Pass an explicit integer like max_tool_calls=8 for safety caps:

@llm_chat(llm_interface=llm, stream=True, max_tool_calls=12)
async def cautious_agent(message: str, history=None):
    """Agent with an explicit safety cap."""
    pass

Decorator Parameters

@llm_function(
    llm_interface=llm_interface,
    toolkit=[tool1, tool2],
    retry_on_exception=True,
    timeout=60
)
async def my_function(param: str) -> str:
    """Supports {language} {style} analysis"""
    pass

result = await my_function(
    "input",
    _template_params={"language": "English", "style": "Professional"},
)

_template_params is passed at call time and only used to format the DocString via str.format. It is removed before signature binding and is not part of the LLM input.

LLM Provider Interface

Supported providers:

• OpenAI (GPT-4, etc.)
• Deepseek
• Anthropic Claude
• Volc Engine Ark
• Baidu Qianfan
• Local LLM (Ollama, vLLM, etc.)
• Any OpenAI API-compatible service
• OpenAI Responses API via OpenAIResponsesCompatible

from SimpleLLMFunc import APIKeyPool, OpenAICompatible, OpenAIResponsesCompatible

# From JSON config
provider = OpenAICompatible.load_from_json_file("provider.json")
llm = provider["deepseek"]["v3-turbo"]

# Direct creation
llm = OpenAICompatible(
    api_key_pool=APIKeyPool(["sk-xxx"], provider_id="deepseek-chat"),
    base_url="https://api.deepseek.com/v1",
    model_name="deepseek-chat",
)

# Responses API
responses_llm = OpenAIResponsesCompatible(
    api_key_pool=APIKeyPool(["sk-xxx"], provider_id="openrouter-gpt-5.4"),
    base_url="https://openrouter.ai/api/v1",
    model_name="gpt-5.4",
)

For Responses API, write normal docstrings and chat history. The adapter maps system prompt to instructions and forwards reasoning={...}.

provider.json

{
    "deepseek": [{
        "model_name": "deepseek-v3.2",
        "api_keys": ["sk-key-1", "sk-key-2"],
        "base_url": "https://api.deepseek.com/v1",
        "max_retries": 5,
        "retry_delay": 1.0,
        "rate_limit_capacity": 10,
        "rate_limit_refill_rate": 1.0
    }]
}

Logging and Observability

Feature	Description
Trace ID tracking	Auto-generated trace_id per call, linking all related logs
Structured logging	Multiple levels (DEBUG–CRITICAL), colored console output
Context propagation	Async-safe contextvars, trace_id auto-associated
File persistence	Auto-rotation and archiving
Langfuse integration	Visualize LLM call chains, nested spans per tool/LLM call

from SimpleLLMFunc.logger import app_log, push_error, log_context

app_log("Starting request", trace_id="request_123")

with log_context(trace_id="task_456", function_name="analyze_text"):
    app_log("Analysis started")     # inherits trace_id
    push_error("Analysis failed")   # inherits trace_id

Built-in Tools

PyRepl — persistent IPython subprocess with variable persistence, execution timeout, event-emitter streaming, and primitive pack support:

from SimpleLLMFunc.builtin import PyRepl
repl = PyRepl(working_directory="./workspace")
tools = repl.toolset  # [execute_code, reset_repl, list_variables]

FileToolset — workspace-scoped file tools with stale-write protection:

from SimpleLLMFunc.builtin import FileToolset
file_tools = FileToolset("./workspace").toolset  # [read_file, read_image, grep, sed, echo_into]

API Key Management and Traffic Control

• Multiple API keys with min-heap load balancing
• Token-bucket algorithm for rate limiting
• Per-model configuration in provider.json

Async Native

All decorators return async functions. Use await or asyncio.run():

# Concurrent LLM calls
results = await asyncio.gather(*[classify_text(t) for t in texts])

Common Use Cases

Data Processing

@llm_function(llm_interface=llm)
async def extract_entities(text: str) -> Dict[str, List[str]]:
    """Extract named entities from text"""
    pass

entities = await extract_entities("John works at Apple in Beijing")
# {"person": ["John"], "location": ["Beijing"], "organization": ["Apple"]}

General-Purpose Agent

@llm_chat(llm_interface=llm, toolkit=[*repl.toolset, *file_tools], stream=True, self_reference_key="main")
async def agent(message: str, history=None):
    """A coding agent with REPL, file tools, and self-reflection"""
    pass

Batch Processing

results = await asyncio.gather(*[classify_text(t) for t in texts])

Multimodal

@llm_function(llm_interface=llm)
async def analyze_images(local_img: ImgPath, web_img: ImgUrl) -> str:
    """Compare and analyze two images"""
    pass

Running Examples

pip install SimpleLLMFunc
cp env_template .env
# Edit .env with your API keys

python examples/tui_general_agent_example.py    # Full coding agent with TUI
python examples/llm_function_pydantic_example.py # Structured output
python examples/event_stream_chatbot.py          # Chat + event stream
python examples/parallel_toolcall_example.py     # Concurrent tool calls
python examples/pyrepl_example.py                # Persistent REPL
python examples/response_api_example.py          # Responses API

Export Agent Skills

simplellmfunc-skill usage ~/.config/opencode/skills
simplellmfunc-skill developer ~/.config/opencode/skills

Use --force to overwrite.

Configuration

Priority (high → low): program config → environment variables → .env file.

# .env
LOG_DIR=./logs
LOG_LEVEL=INFO
LANGFUSE_BASE_URL=https://cloud.langfuse.com
LANGFUSE_PUBLIC_KEY=pk_xxx
LANGFUSE_SECRET_KEY=sk_xxx
LANGFUSE_EXPORT_ALL_SPANS=true

Contributing

• Bug reports: GitHub Issues
• Feature suggestions welcome
• Documentation improvements welcome
• Example code welcome

More Resources

• Chinese Docs | English Docs
• Changelog
• GitHub Repository

Star History

Citation

@software{ni2025simplellmfunc,
  author = {Jingzhe Ni},
  month = {February},
  title = {{SimpleLLMFunc: A New Approach to Build LLM Applications}},
  url = {https://github.com/NiJingzhe/SimpleLLMFunc},
  version = {0.8.1},
  year = {2026}
}

License

MIT