pyplait 2025.1.0

A PyTorch-inspired framework for LLM inference pipelines

plait

A PyTorch-inspired framework for building, executing, and optimizing LLM inference pipelines.

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plait brings the familiar PyTorch programming model to compound AI systems. Define your LLM pipelines as modules with forward() methods, trace them into execution DAGs, and run them with automatic concurrency, backpressure, and resource management.

Why plait?

Most LLM applications are systems, not single calls: they chain multiple LLM invocations, pass structured data between steps, run verifiers, and need consistent handling for retries and rate limits. In plain Python, this complexity leaks everywhere.

plait moves that complexity into a shared runtime:

1. Write normal module composition in forward() - no async boilerplate
2. Trace it into a DAG - dependencies discovered automatically
3. Execute with a scheduler - concurrent I/O, rate limiting, retries handled for you
4. Optimize with feedback - backward passes propagate feedback to improve prompts

Framework Comparison

Feature	plait	DSPy	LangGraph	Pydantic AI
Automatic parallelism	✅	❌	❌	❌
Implicit graph definition	✅	✅	❌	❌
Runtime optimization	✅	❌	❌	❌
Multi-model pipelines	✅	✅	✅	✅
Async-first execution	✅	❌	✅	✅
PyTorch-like API	✅	❌	❌	❌
Learnable parameters	✅	✅	❌	❌

Benchmark: Extract-and-Compare Pipeline

Real-world performance on a fan-out workflow (2 parallel extractions + 1 comparison):

Framework	Time	Memory	Notes
plait	6.9s	0.4 MB	Automatic parallel execution
Pydantic AI	8.7s	17.6 MB	Requires manual asyncio.gather()
LangGraph	10.1s	26.2 MB	Requires explicit Send() config
DSPy	13.4s	76.0 MB	Sequential execution only

plait is up to 2x faster and uses up to 99% less memory than alternatives. See detailed comparisons →

Features

• PyTorch-like API: Module with forward() and backward() methods
• Automatic DAG capture: Trace-based graph construction from eager-mode code
• Async execution: Maximum throughput with adaptive backpressure and rate limiting
• Resource management: Decouple module definitions from endpoint configuration
• LLM-based optimization: Backward passes that propagate feedback to update prompts
• Execution profiling: Chrome Trace Format export for performance visualization

Installation

# Install with uv (recommended)
uv add pyplait

# Or with pip
pip install pyplait

Note: The package is published as pyplait on PyPI, but you import it as plait in Python.

Requirements: Python 3.13+

Quick Start

Define a pipeline as a module composition:

from plait import Module, LLMInference, Parameter
from plait.resources import OpenAIEndpointConfig, ResourceConfig


class SummarizeAndAnalyze(Module):
    """A two-stage pipeline: summarize, then analyze."""

    def __init__(self):
        super().__init__()
        # Learnable instruction that can be optimized via backward passes
        self.instructions = Parameter(
            value="Be concise and highlight key insights.",
            description="Controls the style of analysis output.",
        )
        self.summarizer = LLMInference(
            alias="fast",
            system_prompt="Summarize the input text concisely.",
        )
        self.analyzer = LLMInference(
            alias="smart",
            system_prompt=self.instructions,
        )

    def forward(self, text: str) -> str:
        summary = self.summarizer(text)
        return self.analyzer(f"Analyze this summary:\n{summary}")


# Configure OpenAI endpoints separately from module definition
resources = ResourceConfig(
    endpoints={
        "fast": OpenAIEndpointConfig(
            model="gpt-4o-mini",
            max_concurrent=20,
        ),
        "smart": OpenAIEndpointConfig(
            model="gpt-4o",
            max_concurrent=5,
        ),
    }
)

# Bind resources to the pipeline, then execute
pipeline = SummarizeAndAnalyze().bind(resources=resources)
result = await pipeline("Your input text...")

The pipeline is traced into a DAG, and the scheduler runs nodes concurrently where dependencies allow. Independent branches execute in parallel without manual asyncio.gather() calls.

Core Concepts

PyTorch	plait	Purpose
nn.Module	Module	Base class for operations
nn.Parameter	Parameter	Learnable values (prompts, instructions)
forward()	forward()	Define computation
backward()	backward()	Propagate feedback
torch.fx.Tracer	Tracer	Capture computation graph
torch.optim.*	Optimizer	Update parameters

Module

The base class for all operations. Compose modules by assigning them as attributes:

class DocumentProcessor(Module):
    def __init__(self):
        super().__init__()
        self.extractor = LLMInference(alias="fast", system_prompt="Extract key facts.")
        self.analyzer = MultiPerspectiveAnalysis()  # Another Module
        self.reporter = LLMInference(alias="smart", system_prompt="Write a report.")

    def forward(self, document: str) -> str:
        facts = self.extractor(document)
        analyses = self.analyzer(facts)
        return self.reporter(str(analyses))

LLMInference

The atomic unit for LLM API calls. Uses aliases that are bound to endpoints at execution time:

llm = LLMInference(
    alias="reasoning",           # Bound to endpoint config at runtime
    system_prompt="You are a helpful assistant.",
    temperature=0.7,
    max_tokens=500,
)

Parameter

Learnable values (typically prompts or instructions) that can be optimized:

instructions = Parameter(
    value="Be concise and accurate.",
    description="System instructions for the assistant.",
    requires_grad=True,  # Enable optimization
)

ResourceConfig

Decouple module definitions from infrastructure. The same pipeline can run against different endpoints:

from plait.resources import (
    OpenAIEndpointConfig,
    AnthropicEndpointConfig,
    EndpointConfig,
    ResourceConfig,
)

# Development: use cheaper models
dev_resources = ResourceConfig(
    endpoints={
        "fast": OpenAIEndpointConfig(model="gpt-4o-mini", max_concurrent=5),
        "smart": OpenAIEndpointConfig(model="gpt-4o-mini", max_concurrent=5),
    }
)

# Production: use appropriate models with rate limiting
prod_resources = ResourceConfig(
    endpoints={
        "fast": OpenAIEndpointConfig(
            model="gpt-4o-mini",
            max_concurrent=50,
            rate_limit=1000.0,  # requests per minute
        ),
        "smart": OpenAIEndpointConfig(
            model="gpt-4o",
            max_concurrent=20,
            rate_limit=500.0,
        ),
    }
)

# Self-hosted models with OpenAI-compatible API (vLLM, TGI, etc.)
local_resources = ResourceConfig(
    endpoints={
        "fast": EndpointConfig(
            provider_api="vllm",
            model="mistral-7b",
            base_url="http://vllm.internal:8000/v1",
            max_concurrent=50,
        ),
    }
)

# Bind resources to a pipeline
pipeline = MyPipeline().bind(resources=dev_resources)
result = await pipeline("input text")

# Or use ExecutionSettings for shared resources across multiple pipelines
async with ExecutionSettings(resources=prod_resources):
    result1 = await pipeline1("input")
    result2 = await pipeline2("input")

Examples

The examples/ directory contains focused, runnable examples:

Example	Description
01_module.py	Module, Parameter, and composition
02_llm_pipeline.py	LLMInference and pipeline patterns
03_tracing.py	DAG capture and visualization
04_execution.py	run(), bind(), ExecutionSettings, batch
05_optimization.py	Backward pass and prompt optimization

Run an example:

python examples/01_module.py

Documentation

For detailed architecture and design documentation, see the design_docs/ directory:

• Architecture Overview - System design and component interactions
• Module - Core module system
• Tracing - How DAGs are captured from code
• Execution - Scheduler, state, and error handling
• Resources - Endpoint configuration and rate limiting
• Optimization - Feedback propagation and learning

Development

Setup

# Clone the repository
git clone https://github.com/eric-tramel/plait.git
cd plait

# Install dependencies with uv
uv sync

# Run all checks
make ci

Commands

make ci           # Run all checks (lint, types, test)
make lint         # Format and lint with ruff
make types        # Type check with ty
make test         # Run all pytest tests
make test-unit    # Run unit tests only

See CLAUDE.md for detailed development guidelines.

License

Apache-2.0 License - see LICENSE for details.