> ## Documentation Index
> Fetch the complete documentation index at: https://docs.runagain.ai/llms.txt
> Use this file to discover all available pages before exploring further.

# Prompts

> Browse an agent's system-prompt versions and diff them.

The **Prompts** page reconstructs each agent's **system-prompt versions** from its runs — no
prompt registry to maintain. Every distinct system prompt an agent has used (matched by content)
is a version, ordered oldest-first.

## Versions

For each agent (`agent_name`), RunAgain lists its prompt versions with:

* **Version** — `v1` is the oldest observed prompt; a new version appears whenever the system
  prompt's content changes.
* **Runs** — how many runs used that version, and when it was **first** / **last** seen.
* A link to a sample **run** that used it, and a snippet of the prompt.

Versions are derived from recent runs, so they reflect what your agents actually sent — including
prompt edits you shipped without telling anyone.

## Diff two versions

Select any two versions to reveal a side-by-side **diff** — removed text on the left, added on the
right, rendered as markdown. Use it to see exactly what changed between two iterations of an
agent's instructions (and pair it with the trace-level
[Compare with previous run](/app/traces#compare-runs) to tie a prompt change to a behavior change).

<Tip>
  Set `gen_ai.agent.name` on your spans so runs group under the right agent — see
  [custom metadata](/concepts/observability#custom-metadata-identity).
</Tip>