---
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`

## Request

- Base URL: `https://api.sea-lion.ai` (the document declares no server; this is the origin it was published from)
- URL: `https://api.sea-lion.ai/v1/workflows/runs/{run_id}/messages`
- Auth: API key in header `x-litellm-api-key`

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

- **2026-10-21** `f2fb14eab3f5`: 1 info
  - endpoint added

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

---

[API](https://skmtc.dev/sea-lion/apis/litellm-api.md) · [All operations](https://skmtc.dev/sea-lion/apis/litellm-api/llms.txt) · [OpenAPI document](https://skmtc.dev/sea-lion/apis/litellm-api/revisions/1ba9123c189a?raw)