I’m not seeing the latest version of my prompt. Why?

If you’ve updated a prompt in Langfuse but your application still returns the old version, it’s likely due to caching behavior. The Langfuse SDKs cache prompts locally to ensure low latency and to keep your application running even if Langfuse would be temporarily unavailable.

For a detailed explanation, see the prompt caching documentation.

Solutions

1. Wait for cache revalidation

The SDK cache TTL is 60 seconds by default. After this time, the cached prompt is marked as stale. On the next get_prompt call, the stale prompt is returned immediately while the SDK fetches the new version in the background. This means you need two fetches after the TTL expires to see the updated prompt.

2. Disable caching for development

Set cacheTtlSeconds to 0 to always fetch the latest prompt.

Note: Disabling caching adds a network request on every get_prompt call, which will increase latency. This is recommended for development/testing only.

prompt = langfuse.get_prompt("my-prompt", cache_ttl_seconds=0)

const prompt = await langfuse.prompt.get("my-prompt", {
  cacheTtlSeconds: 0,
});

3. Verify the correct label

By default, get_prompt fetches the production label. If you haven’t promoted your changes to production, use label="latest" to fetch the most recent version:

prompt = langfuse.get_prompt("my-prompt", label="latest")

const prompt = await langfuse.prompt.get("my-prompt", {
  label: "latest",
});