---
title: "Create Tracer Session"
method: POST
path: "/api/v1/sessions"
tags: ["tracer-sessions"]
---

# Create Tracer Session

`POST /api/v1/sessions`

Create a new session.

## Query parameters

- `upsert` boolean

## Request body

- TracerSessionCreate — Create class for TracerSession.
  - `start_time` string, date-time
  - `end_time` string, date-time, nullable
  - `extra` object, nullable
  - `name` string
  - `description` string, nullable
  - `default_dataset_id` string, uuid, nullable
  - `reference_dataset_id` string, uuid, nullable
  - `trace_tier` 'longlived' | 'shortlived'
  - `id` string, uuid, nullable

## Response `200`

Successful Response

- TracerSessionWithoutVirtualFields — TracerSession schema.
  - `start_time` string, date-time
  - `end_time` string, date-time, nullable
  - `extra` object, nullable
  - `name` string
  - `description` string, nullable
  - `default_dataset_id` string, uuid, nullable
  - `reference_dataset_id` string, uuid, nullable
  - `trace_tier` 'longlived' | 'shortlived'
  - `id` string, uuid, required
  - `tenant_id` string, uuid, required
  - `last_run_start_time_live` string, date-time, nullable

## Other responses

- `422` — Validation Error

---

[API](https://skmtc.net/langchain-ai/apis/langsmith.md) · [All operations](https://skmtc.net/langchain-ai/apis/langsmith/llms.txt) · [OpenAPI document](https://skmtc-service-staging.skmtc.workers.dev/v1/apis/langchain-ai/langsmith/versions/a0acb3a6a101/schema)