---
title: "Open a Reason's conversation"
method: POST
path: "/v3/organizations/{orgId}/reasons/{reasonId}/conversation"
tags: ["Reasons"]
---

# Open a Reason's conversation

`POST /v3/organizations/{orgId}/reasons/{reasonId}/conversation`

## Request

- Base URL: `https://api.reasonmachines.com`
- URL: `https://api.reasonmachines.com/v3/organizations/{orgId}/reasons/{reasonId}/conversation`
- Auth: HTTP bearer

Finds or creates the Reason's long-running conversation Session. Creating it runs the ordinary Session admission (plan, credits and write checks) and starts no task until a message is sent. sendReasonMessage does this itself, so a client that only gives the Reason work does not need it.

<sub>Scope: `run`</sub>

## Response `200`

The Reason's conversation.

- ReasonConversation
  - `reason_id` string, uuid, required: The Reason whose conversation this is.
  - `session_id` string, required: The conversation Session. Send to it with sendSessionMessage; read replies with listSessionConversation or getSession.
  - `created` boolean, required: True when this call created the conversation; false when it already existed.

## Other responses

- `400`: Session admission refused the conversation's create as invalid; the body names why.
- `401`: Missing, invalid, or expired key.
- `402`: Usage is unavailable for a new conversation; the body names why.
- `403`: A required scope or workspace permission is missing, or admission refused the create; the body names why.
- `404`: Resource not found.
- `409`: This is an ephemeral benchmark workspace, which holds only its one benchmark Session (`reasons_unavailable_in_ephemeral_workspace`), or admission reported a conflict.
- `413`: Admission refused the create as too large.
- `422`: Admission refused the create as unsupported here; the body names why.
- `429`: Too many requests. Retry after the number of seconds in the `Retry-After` response header.
- `503`: Session writes are disabled.

## Changes

- **2026-10-15** `fad7b15a74a7`: 1 info
  - endpoint added

[Operation history](https://skmtc.dev/ara/apis/reason-api/changes/v3/organizations/:orgId/reasons/:reasonId/conversation/post.md)

---

[API](https://skmtc.dev/ara/apis/reason-api.md) - [All operations](https://skmtc.dev/ara/apis/reason-api/llms.txt) - [OpenAPI document](https://skmtc.dev/ara/apis/reason-api/revisions/e97c8704807c?raw)