marvin

library3.2.7pypypi✓ verified 30d ago

AI functions and agentic workflow library by PrefectHQ. Provides decorator-based AI functions (marvin.fn, marvin.classify, marvin.extract, marvin.cast) and agent/task orchestration. v3.0 released 2024 — merged with ControlFlow, switched LLM backend from OpenAI-only to Pydantic AI (multi-provider). Current version: 3.2.7 (Mar 2026). WARNING: 'marvin' on PyPI is PrefectHQ's AI library — not the SDSS astronomy Marvin library (sdss-marvin on PyPI).

llm-agents ai-ml workflow

pip install marvin

package ↗homepage ↗

INSTALL

IMPORT

SIG · MARVIN

marvin

llm-agentspythonv3.2.7

Install

24.1s avg

Import

7415ms

Disk

214MB

Pass rate

10/ 10

Env Coverage10 / 10

glibc

3.9–3.13

musl

3.9–3.13

Install & Compatibility

Where this runs

tested against v3.2.7 · pip install

no network on importno background threads

Install × environment matrix

Each cell = how many times install + import succeeded across repeated harness runs. Partial = flaky.
glibc = Debian/Ubuntu slim · musl = Alpine Linux

musl

py 3.10–3.95 runs

installs and imports cleanly · install 0.0s · import 1.656s · 235MB

glibc

py 3.10–3.95 runs

installs and imports cleanly · install 24.1s · import 1.310s · 233MB

214MB installed

● package 214MB

Code

Verified usage

Verified import paths — ran on the pinned version, not inferred.

extract

✓ from marvin import extract

✗ from marvin import extract

✓ from marvin import fn

classify

✓ from marvin import classify

Core marvin 3.x structured output functions.

# pip install marvin import marvin import os # Set OPENAI_API_KEY env var — marvin uses OpenAI by default # Structured extraction numbers = marvin.extract( 'I paid $45 for lunch and $12 for coffee', int, instructions='USD amounts only' ) print(numbers) # [45, 12] # Classification category = marvin.classify( 'The new iPhone has great camera features', labels=['tech', 'sports', 'politics'] ) print(category) # 'tech' # AI function @marvin.fn def translate(text: str, language: str) -> str: """Translates text to the given language.""" print(translate('Hello world', 'Spanish')) # 'Hola mundo'

marvin --version

Debug

Known issues

breakingmarvin v2 was OpenAI-only. v3 uses Pydantic AI as backend supporting all providers. marvin.settings.openai.api_key configuration pattern from v2 is gone.

fix

Set OPENAI_API_KEY env var. Or configure other providers via pydantic-ai settings.

affects: >= 3.0.0

breakingControlFlow's @flow decorator removed in v3. ControlFlow merged into marvin. Use marvin.Thread() context manager instead.

fix

Replace @flow decorated functions with 'with marvin.Thread(): marvin.run(...)' pattern.

affects: >= 3.0.0

breakingThread/message history storage changed to SQLite in v3. No database migrations available — expect data loss when updating during development.

fix

Reset SQLite data after version updates during development. Production: handle migrations manually.

affects: >= 3.0.0

gotchaName collision: 'marvin' PyPI package is PrefectHQ's AI library. 'sdss-marvin' is the SDSS astronomy toolkit. LLMs may conflate them. They are completely unrelated.

fix

pip install marvin for AI functions. pip install sdss-marvin for astronomy. Never mix.

affects: all

gotchaMarvin defaults to OpenAI gpt-4o. No model specified = OpenAI API call. Fails silently with AuthenticationError if OPENAI_API_KEY not set.

fix

Set OPENAI_API_KEY or configure a different pydantic-ai provider explicitly.

affects: all

gotchaai_fn decorator from very old v1 docs still appears in many tutorials. Renamed to marvin.fn in v2+.

fix

Use @marvin.fn not @ai_fn.

affects: >= 2.0

breakingInstallation of Python packages with Rust extensions (e.g., 'temporalio') often fails on Alpine Linux (musl) due to dynamic linking requirements of the Rust toolchain or its dependencies (e.g., missing 'libgcc_s.so.1' and '_Unwind' symbols). This occurs because the Rust components might be compiled for glibc, which is incompatible with musl environments.

fix

Install build essentials and C/C++ libraries in your Alpine environment (e.g., 'apk add build-base libstdc++'). Alternatively, use a glibc-based Python image or ensure you're using a Rust toolchain specifically compiled for musl targets.

affects: all

Upgrade

Version history

3.2.7latest on PyPI · released Mar 4, 2026

Audit

Dependencies

pydantic-airequiredLLM backend from v3. Replaces direct OpenAI dependency from v2.

openaioptionalDefault model provider. Marvin uses OpenAI by default — set OPENAI_API_KEY.

Agent activity

28 hits · last 30 days

node

Anthropic

OpenAI (training)

Resources

packagehttps://pypi.org/project/marvin/ ↗

homepagehttps://askmarvin.ai ↗