---
title: "Append Workflow Message"
method: POST
path: "/v1/workflows/runs/{run_id}/messages"
tags: ["workflow management"]
---

# Append Workflow Message

`POST /v1/workflows/runs/{run_id}/messages`

Append a conversation message. Stores full content (not truncated).

Uses optimistic concurrency for sequence numbers.

## Path parameters

- `run_id` string, required

## Request body

- WorkflowMessageCreateRequest
  - `role` string, required
  - `content` string, required
  - `session_id` string, nullable

## Response `200`

Successful Response

- unknown

## Other responses

- `422` — Validation Error

## Changes

- **2026-09-18** `082b5fabd909` — 2 info
  - added the optional property `detail/items/ctx` to the response with the `422` status
  - added the optional property `detail/items/input` to the response with the `422` status

[Change history](https://skmtc.dev/flock/apis/litellm-api/changes/v1/workflows/runs/:run_id/messages/post.md)

---

[API](https://skmtc.dev/flock/apis/litellm-api.md) · [All operations](https://skmtc.dev/flock/apis/litellm-api/llms.txt) · [OpenAPI document](https://skmtc.dev/flock/apis/litellm-api/revisions/731afbea6a1b?raw)