> ## Documentation Index
> Fetch the complete documentation index at: https://langchain-5e9cc07a-preview-opensw-1774360645-bf2eec8.mintlify.site/llms.txt
> Use this file to discover all available pages before exploring further.

# Specify a custom run ID

> How to specify a custom run ID when tracing with LangSmith.

By default, LangSmith assigns a random ID to each run. You can override this with a custom ID when you need to:

* Know the run ID ahead of time (e.g., to attach feedback immediately after a run).
* Correlate LangSmith runs with IDs from an external system.
* Make runs idempotent by reusing a deterministic ID.

<Note>
  We recommend using **UUID v7** custom run IDs. UUIDv7 embeds a timestamp, which preserves correct time-ordering of runs in a trace. Passing a non-UUIDv7 ID currently emits a warning, and will be required by a future version.

  The LangSmith SDK exports a uuid7 helper (Python v0.4.43+, JS v0.3.80+):

  * **Python**: `from langsmith import uuid7`
  * **JS/TS**: `import { uuid7 } from 'langsmith'`
</Note>

Any UUID v7 string is accepted. You can pass one generated by the LangSmith SDK helpers, or your own if your system already uses UUID v7 identifiers.

<Tabs>
  <Tab title="Python">
    ### Use `@traceable`

    Pass `run_id` inside `langsmith_extra` when calling a [`@traceable`](https://reference.langchain.com/python/langsmith/run_helpers/traceable) function:

    ```python Python theme={null}
    from langsmith import traceable, uuid7

    @traceable
    def my_pipeline(question: str) -> str:
        return "answer"

    run_id = uuid7()
    my_pipeline("What is the capital of France?", langsmith_extra={"run_id": run_id})

    # run_id can now be used to attach feedback, query the run, etc.
    ```

    ### Use the `trace` context manager

    Pass `run_id` directly to the [trace](https://reference.langchain.com/python/langsmith/run_helpers/trace) context manager constructor to set the ID for that traced block:

    ```python Python theme={null}
    from langsmith import trace, uuid7

    run_id = uuid7()

    with trace("my-pipeline", run_id=run_id) as run:
        result = "answer"
        run.end(outputs={"result": result})

    # run_id can now be used to attach feedback, query the run, etc.
    ```
  </Tab>

  <Tab title="TypeScript">
    ### Use `traceable`

    Pass `id` in the config object passed to [`traceable`](https://reference.langchain.com/javascript/langsmith/traceable/traceable):

    ```typescript TypeScript theme={null}
    import { traceable } from "langsmith/traceable";
    import { uuid7 } from "langsmith";

    const runId = uuid7();

    const myPipeline = traceable(
      async (question: string) => {
        return "answer";
      },
      { name: "my-pipeline", id: runId }
    );

    await myPipeline("What is the capital of France?");

    // runId can now be used to attach feedback, query the run, etc.
    ```
  </Tab>
</Tabs>

## Related

* [Attach user feedback](/langsmith/attach-user-feedback): common use case for pre-specifying a run ID.
* [Access the current run (span) within a traced function](/langsmith/access-current-span): read the auto-assigned ID from inside a trace.
* [Trace with the LangSmith API](/langsmith/trace-with-api): low-level API approach for specifying run IDs.
* [Trace Vercel AI SDK applications](/langsmith/trace-with-vercel-ai-sdk): specifying a custom run ID with `wrapAISDK`.

***

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