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

# Conversation Version Conflict

> The expected_version in the request does not match the conversation's current head version.

**HTTP status:** 409

## Error message

```
conversation version mismatch: expected {N}, current {M}
```

Example: `conversation version mismatch: expected 2, current 5`.

## When this error occurs

`POST /agents/conversations/{id}/runs` was called with an `expected_version` that no longer
matches the conversation's current head. This is an [optimistic-concurrency](https://en.wikipedia.org/wiki/Optimistic_concurrency_control)
guard: the API rejects the run before starting a workflow that would conflict at finalize time.

It happens when another writer (a previous run, or a concurrent caller) advanced the conversation
between the time you read `version` and the time you posted the new run.

## How to fix

1. Re-read the conversation via `GET /agents/conversations/{id}` to get the current `version`.
2. If you were resuming from a `requires_action` run, also re-read the latest assistant turn via
   `GET /agents/conversations/{id}/messages?since={your_known_version}` to learn whether the
   pending tool calls have changed.
3. Retry the run with the fresh version.

## Race-free continuation pattern

For tool-output resumes, always refetch the conversation's `version` immediately before posting —
don't rely on a value cached from earlier in the conversation's lifecycle.