langfuse-freeze 0.1.0

Langfuse Freeze

langfuse-freeze

Wraps the Langfuse client to snapshot prompts to disk at startup. If Langfuse is unreachable at runtime, the local backup is used as fallback.

How it works

On import langfuse_freeze, LangfuseBacked.bootstrap() runs automatically:

• Backup file already exists → skip (log and continue)
• Backup file missing → fetch all prompts from Langfuse, write to disk
• Fetch fails → retry with exponential backoff, raise RuntimeError after max retries

At runtime, LangfuseBacked.get_prompt() injects the backup as fallback so Langfuse SDK handles outages gracefully.

Installation

uv add langfuse-freeze

Usage

from langfuse_freeze.main import LangfuseBacked

client = LangfuseBacked()
prompt = client.get_prompt("my-prompt", type="text", label="production")

Drop-in replacement for Langfuse. Same API.

Bootstrap at container build time

Run before the app starts (e.g. in a Dockerfile or k8s init container):

langfuse-freeze-bootstrap

Same logic as import-time bootstrap — skips if backup already present.

Configuration

Env var	Default	Description
LANGFUSE_PUBLIC_KEY	—	Required
LANGFUSE_SECRET_KEY	—	Required
LANGFUSE_HOST	—	Required
LANGFUSE_PROMPTS_BACKUP_PATH	./langfuse-backup/prompts.json	Backup file location
LANGFUSE_BOOTSTRAP_MAX_RETRIES	3	Fetch attempts before crash
LANGFUSE_BOOTSTRAP_RETRY_DELAY	2	Base seconds for exponential backoff
LANGFUSE_DISABLE_BOOTSTRAP	—	Set to 1 to skip import-time bootstrap

Backup format

{
  "my-prompt": {
    "type": "text",
    "labels": {
      "production": "You are a helpful assistant.",
      "dev": "You are a dev assistant."
    }
  }
}

To refresh the backup, delete the file and restart (or re-run langfuse-freeze-bootstrap).

Running tests

Unit tests (no network):

uv run pytest tests/ -m "not integration"

Integration tests (requires Langfuse running at http://localhost:10016):

uv run pytest tests/ -m integration