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Prompt Registry

Beta

This feature is in Beta.

Overview​

The MLflow Prompt Registry is a centralized repository for managing prompt templates across their lifecycle. It enables teams to:

  • Version and track prompts with Git-like versioning, commit messages, and rollback capabilities
  • Deploy safely with aliases using mutable references (e.g., "production", "staging") for A/B testing and gradual rollouts
  • Collaborate without code changes by allowing non-engineers to modify prompts through the UI
  • Integrate with any framework including LangChain, LlamaIndex, and other GenAI frameworks
  • Maintain governance through Unity Catalog integration for access control and audit trails
  • Track lineage by linking prompts to experiments and evaluation results

The Prompt Registry follows a Git-like model:

  • Prompts: Named entities in Unity Catalog
  • Versions: Immutable snapshots with auto-incrementing numbers
  • Aliases: Mutable pointers to specific versions
  • Tags: Version-specific key-value pairs

Prerequisites​

  1. Install MLflow with Unity Catalog support:
    Bash
    pip install --upgrade "mlflow[databricks]>=3.1.0"
  2. Create an MLflow experiment by following the setup your environment quickstart.
  3. Make sure you have access to a Unity Catalog schema with the CREATE FUNCTION, EXECUTE, and MANAGE permissions to view or create prompts in the prompt registry.

Quick start​

The following code shows the essential workflow for using the Prompt Registry. Notice the double-brace syntax for template variables:

Python
import mlflow

# Register a prompt template
prompt = mlflow.genai.register_prompt(
    name="mycatalog.myschema.customer_support",
    template="You are a helpful assistant. Answer this question: {{question}}",
    commit_message="Initial customer support prompt"
)
print(f"Created version {prompt.version}")  # "Created version 1"

# Set a production alias
mlflow.genai.set_prompt_alias(
    name="mycatalog.myschema.customer_support",
    alias="production",
    version=1
)

# Load and use the prompt in your application
prompt = mlflow.genai.load_prompt(name_or_uri="prompts:/mycatalog.myschema.customer_support@production")
response = llm.invoke(prompt.format(question="How do I reset my password?"))

SDK overview​

The following table summarizes the six main functions that Prompt Registry provides. For examples, see Prompt Registry examples.

Function

Purpose

register_prompt()

Create new prompts or add new versions

load_prompt()

Retrieve specific prompt versions or aliases

search_prompts()

Find prompts by name, tags, or metadata

set_prompt_alias()

Create or update alias pointers

delete_prompt_alias()

Remove aliases (versions remain)

delete_prompt()

Delete entire prompts or specific versions

Prompt template formats​

Prompt templates can be stored in two formats: simple prompts or conversations. For both, prompt strings can be templatized using the double-brace syntax "Hello {{name}}".

Format

Python type

Description

Example

Simple prompt

str

Single-message prompt template

"Summarize the content below in {{num_sentences}} sentences. Content: {{content}}"

Conversation

List[dict]

Each dict is one message with 'role' and 'content' keys

[{"role": "user", "content": "Hello {{name}}"}, ...]

The following example shows both simple and conversation-style prompts, using the double-brace format for template variables:

Python
# Simple prompt
simple_prompt = mlflow.genai.register_prompt(
    name="mycatalog.myschema.greeting",
    template="Hello {{name}}, how can I help you today?",
    commit_message="Simple greeting"
)

# Conversation or chat-style prompt
complex_prompt = mlflow.genai.register_prompt(
    name="mycatalog.myschema.analysis",
    template=[
        {"role": "system", "content": "You are a helpful {{style}} assistant."},
        {"role": "user", "content": "{{question}}"},
    ],
    commit_message="Multi-variable analysis template"
)

# Use the prompt
rendered = complex_prompt.format(
    style="edgy",
    question="What is a good costume for a rainy Halloween?"
)

Single-brace format compatibility​

LangChain, LlamaIndex, and some other libraries support single-brace syntax (Python f-string syntax) for prompt templates: "Hello {name}". For compatibility, MLflow supports converting prompts to single-brace format:

Python
from langchain_core.prompts import ChatPromptTemplate

# Load from registry
mlflow_prompt = mlflow.genai.load_prompt("prompts:/mycatalog.myschema.chat@production")

# Convert to LangChain format
langchain_template = mlflow_prompt.to_single_brace_format()
chat_prompt = ChatPromptTemplate.from_template(langchain_template)

# Use in chain
chain = chat_prompt | llm | output_parser

Next steps​

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