---
title: "Open a session"
method: POST
path: "/v1/sessions"
---

# Open a session

`POST /v1/sessions`

## Request

- Base URL: `https://assemble-vms-api.fly.dev`
- URL: `https://assemble-vms-api.fly.dev/v1/sessions`
- Auth: HTTP bearer

Create or find an owner's session by name, then prepare its VM and filesystem. Reopening the same name reuses its identity. Selecting a different image for an existing name fails.

## Request body

- OpenSession
  - `name` string, required
  - `resources` SessionResources
    - `cpu` integer, required: vCPU count.
    - `memory` integer, required: RAM in GiB.
    - `disk` integer, required: Local VM disk in GiB; separate from session-filesystem storage.

## Response `200`

Session ready for work.

- Session: One persistent Assemble VM and its session filesystem. The session remains allocated until explicitly deleted; completing an execution or agent run does not delete it.
  - `id` string, uuid, required
  - `name` string, required
  - `state` 'starting' | 'running' | 'paused' | 'stopped' | 'error' | 'deleting', required
  - `rootDirectory` string, required: Persistent project directory used by file operations and the default working directory for managed commands.
  - `homeDirectory` string, required: VM-local HOME for managed commands. Raw SSH uses the image login home unless the user explicitly exports this value.
  - `createdAt` string, date-time, required
  - `updatedAt` string, date-time, required
  - `resources` SessionResources
    - `cpu` integer, required: vCPU count.
    - `memory` integer, required: RAM in GiB.
    - `disk` integer, required: Local VM disk in GiB; separate from session-filesystem storage.

## Other responses

- `default`: Structured API error. HTTP 400 invalid request, 401 authentication, 404 missing resource, 409 conflict, 413 size limit, 429 quota, or 503 unavailable.

---

[API](https://skmtc.dev/assemble/apis/assemble-vms-api.md) - [All operations](https://skmtc.dev/assemble/apis/assemble-vms-api/llms.txt) - [OpenAPI document](https://skmtc.dev/assemble/apis/assemble-vms-api/revisions/93f55a2e3de3?raw)