---
title: "Changes to Read Tracer Session"
method: GET
path: "/api/v1/sessions/{session_id}"
---

# Changes to Read Tracer Session

`GET /api/v1/sessions/{session_id}`

> Every recorded change to this operation, newest first.

## Timeline

Changed in 2 of 77 revisions.

- **2026-10-16** `1a8ee9358d81`: 4 breaking, 3 info
- **2026-05-28** `d3056703d8de`: 1 info

## Changes

- **2026-10-16** `1a8ee9358d81`: 4 breaking, 3 info
  - the `detail/items/` response's property type changed from `object` to `string` for status `422`
  - removed the required property `detail/items/loc` from the response with the `422` status
  - removed the required property `detail/items/msg` from the response with the `422` status
  - removed the required property `detail/items/type` from the response with the `422` status
  - the `completion_cost/anyOf[subschema #1]/` response's property pattern `^(?!^[-+.]*$)[+-]?0*\d*\.?\d*$` was added for the status `200`
  - the `prompt_cost/anyOf[subschema #1]/` response's property pattern `^(?!^[-+.]*$)[+-]?0*\d*\.?\d*$` was added for the status `200`
  - the `total_cost/anyOf[subschema #1]/` response's property pattern `^(?!^[-+.]*$)[+-]?0*\d*\.?\d*$` was added for the status `200`
- **2026-05-28** `d3056703d8de`: 1 info
  - added the optional property `experiment_progress` to the response with the `200` status

---

[Operation](https://skmtc.dev/langchain-ai/apis/langsmith/docs/api/v1/sessions/:session_id/get.md) - [API](https://skmtc.dev/langchain-ai/apis/langsmith.md) - [Page](https://skmtc.dev/langchain-ai/apis/langsmith/changes/api/v1/sessions/:session_id/get)