---
title: "Query Thread Traces"
method: GET
path: "/v2/threads/{thread_id}/traces"
tags: ["threads"]
---

# Query Thread Traces

`GET /v2/threads/{thread_id}/traces`

**Alpha:** The request and response contract may change;
Retrieve all traces belonging to a specific thread within a project.

## Path parameters

- `thread_id` string, required

## Query parameters

- `cursor` string
- `filter` string
- `page_size` integer
- `project_id` string, uuid, required
- `selects` string[]

## Response `200`

items and pagination

- ThreadsQueryThreadTracesResponseBody
  - `items` ThreadsThreadTraceListItem[] — `items` is the page of root traces in this thread. Which properties are populated on each trace depends on the `selects` query parameter.
    - `completion_cost` number — `completion_cost` is the estimated USD cost for the completion. Omitted unless included in `selects`.
    - `completion_cost_details` QueryRunCompletionCostDetails
      - `raw` object — `raw` maps each category name to its estimated USD cost.
    - `completion_token_details` QueryRunCompletionTokenDetails
      - `raw` object — `raw` maps each category name to its completion-token count.
    - `completion_tokens` integer — `completion_tokens` is the completion-side token count. Omitted unless included in `selects`.
    - `end_time` string, date-time — `end_time` is when the root run ended (RFC3339 date-time). JSON null if the run is still in progress. Omitted unless included in `selects`.
    - `error_preview` string — `error_preview` is a short error summary when the run failed. Omitted unless included in `selects`.
    - `first_token_time` string, date-time — `first_token_time` is when the first output token was produced (RFC3339 date-time), for streamed runs when that metadata exists. Omitted unless included in `selects`.
    - `inputs_preview` string — `inputs_preview` is a truncated text preview of inputs. Omitted unless included in `selects`.
    - `latency` number — `latency` is wall-clock duration from start to end in seconds. Omitted unless included in `selects`.
    - `name` string — `name` is a human-readable label for the root run (for example the model name, function name, or step name chosen when the run was traced). Omitted unless included in `selects`.
    - `op` number — `op` is a numeric code identifying the root run's `run_type` (for example LLM vs. tool vs. chain). Encoded as a number for compatibility with legacy clients; prefer the string `run_type` on `RunResponse` when available. Omitted unless included in `selects`.
    - `outputs_preview` string — `outputs_preview` is a truncated text preview of outputs. Omitted unless included in `selects`.
    - `prompt_cost` number — `prompt_cost` is the estimated USD cost for the prompt. Omitted unless included in `selects`.
    - `prompt_cost_details` QueryRunPromptCostDetails
      - `raw` object — `raw` maps each category name to its estimated USD cost.
    - `prompt_token_details` QueryRunPromptTokenDetails
      - `raw` object — `raw` maps each category name to its prompt-token count.
    - `prompt_tokens` integer — `prompt_tokens` is the prompt-side token count. Omitted unless included in `selects`.
    - `start_time` string, date-time — `start_time` is when the trace started (RFC3339 date-time). Omitted unless included in `selects`.
    - `thread_id` string, uuid — `thread_id` is the conversation thread UUID that contains this trace. Matches the `thread_id` path parameter of the request. Omitted unless included in `selects`.
    - `total_cost` number — `total_cost` is the estimated total USD cost for the root run. Omitted unless included in `selects`.
    - `total_tokens` integer — `total_tokens` is the total token count (prompt plus completion). Omitted unless included in `selects`.
    - `trace_id` string, uuid — `trace_id` is the UUID of this trace (the root run). Always present.
  - `next_cursor` string — `next_cursor` is the opaque cursor to pass as `cursor` on the next request. Omitted on the final page.

## Other responses

- `400` — bad request (missing or invalid query parameters)
- `401` — missing or invalid authentication
- `403` — forbidden (insufficient permission)
- `404` — session not found
- `422` — unprocessable entity (e.g. invalid project UUID)
- `500` — internal server error
- `503` — service unavailable
- `504` — gateway timeout or deadline exceeded

---

[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/revisions/a0acb3a6a101/schema)